Eco-friendly, renewable energy sources

Benefits of using wood chips over coal

1. When using wood chips, the following issues are resolved:
   1. sawmill waste disposal;
   2. utilization of knots, undergrowth in the development of plots at the logging site;
   3. questions on cleaning up agricultural land overgrown with birch and shrubs;
   4. for the disposal of non-commercial wood;
   5. for clearing forests and forest belts;
   6. reducing the fire hazard of forests and forest belts.
2. Wood chip boilers are more environmentally friendly, because the boiler automation system monitors the complete combustion of the wood chips and the correct ratio of the supplied air and wood chips.
3. Wood chips are a renewable source of energy.

Chip quality

The smooth functioning of small heating systems requires dry, sieved material with certain sizes of individual chips. Usually, a material with a particle length of the main fraction from 3.15 to 30 mm and a residual moisture content of less than 30% is used for this.

Larger installations may use coarser materials with increased edge length variation.

An important indicator of the quality of combustion is the ash content of wood chips. With a high ash content, flue gas cleaning is required.

Rationing and classification of wood chips

As the main parameters, according to the classification according to the Austrian standard M7133, requirements are set for the size of the chips, for example: G30 - for chips with a maximum cross section of 3 cm 2, G50 - for chips with a maximum cross section of 5 cm 2, as well as moisture content , for example: W35 - for wood chips with a maximum moisture content of 35%.

This standard establishes classes and specifications for the following parameters:

• Humidity
• Ash content
• Fractional composition (size)
• Bulk density
• Nitrogen and chlorine content
• Heat of combustion

Chip characteristics

If the calorific value of a tree depends only to a small extent on the type of wood, then the humidity in this regard is of great importance. In addition, humidity is a determining factor for the storage stability of wood chips.

Wood chips below 30% moisture content are classified as “storable”, i.e. in this case, we cannot talk about the microbial decomposition of wood and the associated mass and energy losses. The moisture content of freshly cut material is between 50% and 60%. Therefore, it is recommended to produce wood chips after pre-drying.

The following table shows the calorific value as a function of humidity. The calorific value of freshly cut coniferous trees is approximately 2 kWh per kg, after drying to a moisture content of 20%, the calorific value of wood chips can double (4 kWh).

Bulk density is the next main characteristic of wood chips (and other solid fuels).

Among other things, it determines the energy density of the fuel and is directly dependent on the volume of space required to store and transport a certain amount of energy.

If the calorific value of chips with a moisture content of 20% from oak and beech is 1100 kWh per bulk cubic meter, then the calorific value of chips from poplar is significantly lower and amounts to 680 kWh per bulk cubic meter.

For example, to cover the annual requirement of 44 MWh of an apartment building, 40 bulk cubic meters of oak and beech chips or 65 bulk cubic meters of poplar chips are required.

Manufacturing and marketing

In Germany, coniferous wood chips are primarily in demand on the market.

In 2007, according to the Federal Bureau of Statistics, the production of chips from coniferous trees was 3.80 million tons, during the same period only 41,000 tons of chips from deciduous trees were produced.

Sales of lower quality products from croaker and small shrub forest amounted to 1.98 million tons. In the same period, 4.04 million tons of chips or flakes from coniferous trees and 85,000 tons from deciduous trees were imported. This is a 340% increase in imports over 5 years. 63% of imports came from Austria, the Netherlands and France. Export of wood chips and chips in 2007 amounted to 17.94 million tons, which is 66% more than in 2002.

Price

Prices for wood chips have increased over the past years, from July 2004 to July 2009 the increase was 80%. The retail selling price for dry chips in Q4 2009 in Germany was 119 Euro per tonne (20% moisture or 25% wood moisture, 30m 3 delivery including delivery up to 20 km and VAT). This equates to a liquid fuel equivalent price of 29.71 cents per litre.

A significant difference or fluctuation in price is determined depending on the region, season, quality, humidity and distance from the object of delivery. The volume of delivery is also an important factor, since large CHP plants consume 40% less fuel than small plants.

FUEL - WOOD CHIPS

Wood chips are crushed wood. As a fuel, the benefits are unrivaled, available in sufficient quantities and continuously replenished.

If necessary, only as a result of regular maintenance of their forests, it is possible to mobilize additional annually large numbers.

Any unprocessed wood can be processed into chips: roundwood, sawmill waste, wood after processing and processing, products from farms with a fast turnover of felling, trees after thinning and wood residues.

Wood chips, like pellets:

• domestic fuel.
• Does not depend on the crisis.
• Neutral to carbon dioxide.
• Not expensive for the price.

Its application reduces dependence on imports, restrains the formation of prices in the country and offers sustainable development chances for the regions.

The advantages of wood chips compared to firewood and lumps of wood lie primarily in their flowability, which ensures combustion in fully automatic heating systems.

For the quality of wood chips, fuel characteristics such as moisture content, lumpiness, particle size distribution, proportion of fines, proportion of bark, bulk density and ash content are important.

With an increase in the proportion of bark, a greater amount of ash is formed during combustion.

Bulk density reflects the weight of a bulk cubic meter and ultimately determines what heat of combustion the buyer will receive for his money.

In Germany, there are no DIN standards for wood chips. As a result of long-term use in Germany, the limit values ​​and conditions of the Austrian classification for wood chips in accordance with the Austrian standard M7133 have taken root as a trade standard.

In May 2005, a provisional standard (technical specification) entitled "Solid Biofuels - Fuel Specifications and Classes" (DIN CEN/TS 14961) came into force as a classification standard, which defines classes and specifications for the following parameters:

• Humidity
• Ash content
• Grain size distribution
• Bulk density
• Nitrogen and chlorine content
• Heat of combustion

Other chip data:

• Heat of combustion: OK. 3.3 - 4.3 kWh/kg or 783 kWh/m 3 depending on humidity (from freshly cut state to 40% humidity).
• Bulk density: OK. 210 - 250 kg/m 3 depending on humidity, 230 kg/m 3 at 20% humidity.
• Ideal size: edge length 30-50 mm.
• Humidity: w (relative humidity) - the mass of water indicated as a percentage in relation to the total mass, the mass of freshly cut wood.
• Dominion: u (absolutely dry wood=absolutely air-dried) is the mass of water indicated as a percentage in relation to the dry mass, the mass of dry matter.

Units:

• 1 Srm = bulk cubic meter, corresponds to 1 m 3 of wood in bulk
• 1 rm = storage cubic meter (ster), corresponds to 1 m 3 of timber laid in rows
• 1 fm = 1 cubic meter of solid wood (no gaps)

Conversion factors:

• 1 bulk cubic meter of wood chips = approx. 65-75 liters of liquid fuel
• 1 bulk cubic meter of chips = bulk density 210-250 kg / m 3
• 1 kg wood chips = approx. 3.4 kWh
• 1 storage cubic meter of wood (ster) = approx. 2.5 bulk cubic meters of wood chips
• 1 cubic meter of solid wood = ca. 2.8 bulk cubic meters of chips

Primary Energy Ratio: for chips fP= 0.2
(describes the losses that occur when obtaining, converting and transporting the corresponding energy carrier)

Heat of combustion and cost:

Indicative data.

Prices for wood chips may vary by region. (1 ton of wood chips = exactly 3.400 kWh)

The following chart shows the evolution of prices since 2007 for wood chips, fuel oil, gas and pellets per 10 kWh

1 - wood chips, 2 - wood pellets, 3 - liquid fuel, 4 - natural gas.

The right choice of fuel for a solid fuel boiler helps to save money and keep the equipment operable.

When using firewood, pellets (fuel pellets), fuel briquettes and coal for space heating, it is important that heat release occurs slowly.

For space heating, hardwood is best suited: oak, ash, birch, hazel, yew, hawthorn.

Different types of trees have their own burning characteristics. So, firewood from beech, birch, ash, hazel is difficult to kindle, but they can burn damp, as they have little moisture. In addition, “deciduous” firewood, except for beech, easily splits.

Alder and aspen burn without the formation of soot and even burn it out of the chimney. Birch firewood is good for heat, but if there is not enough air in the firebox, it burns smokyly and forms tar (birch resin), which settles on the walls of the pipe. In turn, pine wood burns hotter than spruce due to a higher resin content.

Oak and hornbeam have better heat dissipation when burning, but do not split well, cedar gives long-smoldering coal, firewood from pear and apple trees splits easily and burns well, from cherry and elm they smoke when burned, and from plane tree they melt easily, but it is difficult to prick.

Softwood firewood has a low calorific value, smokes and sparks, forming resinous deposits in the pipe, but easily splits and melts. Poplar and linden burn well, spark strongly and burn out very quickly.

The calorific value of firewood of various species depends on the density of the wood, which in turn affects the conversion factor cubic meter => warehouse meter.

Table with average values ​​​​of calorific value per 1 storage meter of firewood

It is noteworthy that 1 warehouse meter of dry wood of deciduous trees replaces 200-210 liters of liquid fuel or 200-210 m 3 of natural gas.

Pellets, for the production of which bark, sawdust, wood chips, agricultural waste (sunflower husks, straw, substandard flax), as well as organic packaging materials and cardboard containers, are used, are equivalent in efficiency to coal.

Today, this modern universal type of biofuel is produced both from cobblestone of hard and soft wood species, and from straw, sunflower husks, corn cobs and stalks, and peat.

Made from recyclable materials that are harmless to humans and the environment, pellets emit 10-50 times less carbon dioxide (CO 2) into the environment and 15-20 times less ash than in the case of coal combustion.

Pellets are used for heating residential buildings by burning in stoves, fireplaces and boilers, to provide heat and electricity to industrial facilities and small settlements (using large pellets, with a high content of wood bark).

In addition, pellets are cheaper than coal, liquid fuels or firewood, such biofuels are conveniently transported in packaged bags and in bulk, they do not require large storage areas and can be stored outdoors without swelling or rotting.

During storage, pellets do not ignite spontaneously, do not require additional processing before use, and their calorific value is higher than that of sawdust and wood chips, and is 1.5 times higher than the calorific value of firewood.

Heat dissipation from pellets and alternative energy sources

When burning 1.9 tons of pellets, approximately the same amount of heat is released as when burning 1 ton of fuel oil. At the same time, the cost of pellets in the domestic market is 3 times cheaper, that is, heating with pellets is 40% cheaper than fuel oil.

Comparative characteristics of fuels

Such biofuel burns almost completely with a minimum amount of slag and allows you to clean the boiler much less frequently. Pellet boilers last longer, require less maintenance and are more economical. In addition, domestic pellet heaters can be controlled automatically.

In the USA, the production of pellets is regulated by certain standards - Standard Regulations & Standards for Pellets in the US - for density, size, humidity, dust content and other substances. Thus, the Premium variety, whose ash content is no more than 1%, accounts for about 95% of pellets produced in the United States, the rest - for the Standard variety, whose ash content is no more than 3%.

– In Germany: DIN 51731, in Austria: ONORM M 7135, in the UK: The British BioGen Code of Practice for biofuel (pellets), in Switzerland: SN 166000, in Sweden: SS 187120.

Main European quality standards for fuel pellets

Fuel briquettes, the production of which also uses woodworking waste (sawdust, wood chips), agricultural waste (straw, sunflower husks, buckwheat) and peat, are suitable for various types of furnaces (stoves), wood-burning boilers and fireplaces.

Now you can buy RUF-briquettes - rectangular bricks, NESTRO-briquettes of cylindrical shape, sometimes with a radial hole inside and Pini & Kay - briquettes that have 4, 6 or 8 faces with a longitudinal radial hole inside.

This environmentally friendly biofuel is not affected by fungi, burns 2-4 times longer than firewood, is convenient to store and use.

Also, briquettes have on average twice the calorific value compared to conventional firewood, ensuring a constant temperature at each stage of combustion due to an even flame.

Modern solid fuel boilers on briquettes can be cleaned no more than once a year, and the ash can be used as an environmentally friendly fertilizer.

The cost of heating with fuel briquettes is lower than in the case of using coal or firewood.

The quality of coal depends on the age and conditions of coalification. With aging, there was a concentration of carbon and a decrease in the content of volatile components, in particular water. So, young brown coal has a moisture content of 30-40% and more than 50% of volatile components, hard coal has a moisture content of 12-16% and about 40% of volatile components, and for old coal - anthracite - these 2 indicators are 5-7%.

Coal also contains various non-combustible ash-forming impurities, "rock". Ash pollutes the environment and sinters into slag on the grate, which makes it difficult to burn coal, and the presence of rock reduces the specific heat of combustion of coal.

Depending on the variety and conditions of extraction, the amount of minerals differs very much. Thus, the ash content of coal is about 15% (10-20%).

Sulfur is also a harmful component of coal, during the combustion of which oxides are formed, which in the air turn into sulfuric acid.

Coal is classified according to many parameters (geography of production, chemical composition), but from a “household” point of view, it is enough to know the marking and the possibilities of use.

The following coal designation system is used: Grade = (brand) + (size class).

Coal consists of two combustible components: volatile substances and solid (coke) residue.

At the first stage of combustion, volatile substances are released; with an excess of oxygen, they quickly burn out, giving a long flame, but a small amount of heat. At the second stage, the coke residue burns out, the combustion intensity and ignition temperature of which depend on the degree of coalification, that is, on the type of coal (brown, stone, anthracite).

The higher the degree of coalification (anthracite has the highest), the higher the ignition temperature and heat of combustion, but the lower the combustion intensity.

Coal of grades B (brown), D (stone long-flame), G (stone gas) due to the high content of volatile substances quickly flares up and quickly burns out.

Coal of these grades is available and suitable for almost all types of boilers, however, for complete combustion, this coal must be supplied in small portions so that volatile substances have time to fully combine with oxygen.

Complete combustion of coal is characterized by yellow flames and clear flue gases, while incomplete combustion is characterized by purple flames and black smoke. For efficient combustion of such coal, the process must be constantly monitored.

Coal grades SS (stone weakly caking, A (Anthracite) is more difficult to kindle, but it burns for a long time and releases much more heat.

Such coal can be loaded in large batches, since it burns mainly coke residue and there is no mass release of volatile substances.

The blowing mode is very important, since with a lack of air, combustion occurs slowly, it may stop, or, conversely, an excessive increase in temperature, which leads to the removal of heat and burnout of the boiler.

Comparative table of calorific value of some types of fuel

"B.M. Engineering" performs a full range of services for the design, construction, commissioning and subsequent maintenance of: biomass processing plants (production of pellets and briquettes), feed mills

• analysis of the raw material base and working capital for production
• calculation of the main equipment
• calculation of additional equipment and mechanisms
• the cost of installation, commissioning, staff training
• calculation of the cost of preparing the production site
• calculation of the cost of production or a waste disposal complex
• calculation of profitability of production or waste disposal complex
• ROI calculation
The cost of settlements is determined after receiving an official request and the formation of a list and completeness of our services.

BM Engineering SPECIALIZATION:

• PRODUCTION OF EQUIPMENT: pellet / briquette lines, drying complexes, disintegrators, biomass presses
• INSTALLATION OF INDUSTRIAL COMPLEXES: design, site search, construction, commissioning
• COMMISSIONING OF EQUIPMENT: start and configure equipment
• TRAINING: setting up the work of the technical department, creating sales, logistics, marketing departments from "0"
• SERVICE MAINTENANCE: full service and warranty service
• AUTOMATION OF PRODUCTION: implementation of control and accounting systems in production
• CERTIFICATION: preparation for certification according to EN+, ISO

BM Engineering, an engineering company in the field of biomass processing, for the first time in the Ukrainian market provides a full range of services for the creation of turnkey modern biomass processing plants producing pellets, briquettes, and animal feed. At the stage of project preparation, the company's specialists give a qualified opinion on the feasibility of building an object, its expected profitability and payback period.

We analyze future production from A to Z! We start the study by calculating the volume of the raw material base, its quality, and supply logistics. The amount of biomass at the initial stage and its supply should be sufficient for the uninterrupted operation of the equipment for a long time. On the basis of objective information collected about future production, we calculate the characteristics of the main equipment, and, at the request of the customer, additional equipment and mechanisms.

The total cost of the project necessarily includes the costs of preparing the production site, installation and commissioning, and training of personnel. And in the forecast of the cost of production, energy efficiency and the specific cost of producing a unit of finished products, its technical and qualitative characteristics, compliance with international standards, profitability and payback period of investments are taken into account in advance. The use of equipment for the production of extruded feed significantly increases the profitability of animal husbandry by improving their quality and reducing costs.

Certification and audit of pellet production in accordance with the norms of the European standards of the EN 17461 series provides that at all stages of work from the receipt and quality control of bio-raw materials to the manufacture of pellets, their packaging, labeling, storage, delivery and use, it is necessary to strictly comply with uniform standards, technical conditions and rules.

In accordance with the ENplus system, a certificate must be obtained for a specific batch of biofuel after appropriate tests have been carried out for all parameters in a certified laboratory. Remember! Certified products cost several times more!

A full range of engineering services provided by BM Engineering includes: drawing up a business plan for production with the calculation of energy efficiency, profitability and product cost, design, construction, commissioning, commissioning and maintenance. In addition, the company supplies equipment of its own production, performs work on automation and certification of built enterprises.

The unique module for processing biomass (wood chips and sawdust) MB-3 was developed according to the latest technology, in which bio-raw materials are not dried before pressing with high energy costs, but are washed in a hydrowasher. Contaminants (metal, soil particles, debris) are removed by a stream of water, and clean and wet particles of raw materials are conveyed through a conveyor, and then through a sieve, into the input hopper of the processing module.

The rotating auger grinds the wet biomass and pushes it through the sieve. During a biochemical reaction, heat is released in wood cells (biopolymers). The optimal temperature of the moistened mass is maintained by the thermal stabilization module. The heat pump circulates heated water around the entire recycling circuit. The entire technological process is controlled by an automation system.

Module complete set:

• hydrowash;
• biomass processing module;
• Heat pump;
• thermal stabilization module;
• process automation system.

Specifications of biomass processing module MB-3:

• productivity - 1000 kg/h;
• electric motor power - up to 100 kW;
• input raw materials: particle size - up to 4 cm, humidity - up to 50%;
• shipping dimensions - 2000x2200x12000 mm;
• weight - 16700 kg.

Only in the first half of 2015, 6 specialized seminars "Fundamentals of Pellet Production" were held, where about 200 students were trained. Since the second half of 2015, seminars have been held monthly and are becoming increasingly popular with listeners. Those specialists who listened to all the lectures and looked at the operating equipment completely changed their attitude towards the technology of pellet production. The wet pressing method is a completely new innovative approach to biomass processing, which is the future.

Wood is a rather complex material in terms of its chemical composition.

Why are we interested in chemistry? Why, combustion (including burning wood in a stove) is a chemical reaction of wood materials with oxygen from the surrounding air. The calorific value of firewood depends on the chemical composition of a particular type of wood.

The main binding chemical materials in wood are lignin and cellulose. They form cells - a kind of container, inside which there is moisture and air. The wood also contains resin, proteins, tannins and other chemical ingredients.

The chemical composition of the vast majority of wood species is almost the same. Small fluctuations in the chemical composition of different species and determine the differences in the calorific value of different types of wood. Calorific value is measured in kilocalories - that is, the amount of heat obtained by burning one kilogram of a tree of a particular species is calculated. There are no fundamental differences between the calorific values ​​of different types of wood. And for domestic purposes, it is enough to know the average values.

Differences between rocks in calorific value appear to be minimal. It is worth noting that, based on the table, it may seem that it is more profitable to buy firewood harvested from coniferous wood, because their calorific value is greater. However, on the market, firewood is supplied by volume, not by mass, so there will simply be more of it in one cubic meter of firewood harvested from hardwood.

Harmful impurities in wood

During the chemical combustion reaction, the wood does not burn completely. After combustion, ash remains - that is, the unburned part of the wood, and during the combustion process, moisture evaporates from the wood.

Ash has less effect on the quality of combustion and the calorific value of firewood. Its amount in any wood is the same and is about 1 percent.

But the moisture in the wood can cause a lot of problems when burning them. So, immediately after felling, wood can contain up to 50 percent moisture. Accordingly, when burning such firewood, the lion's share of the energy released with the flame can simply be spent on the evaporation of the wood moisture itself, without doing any useful work.

The moisture present in wood dramatically reduces the calorific value of any firewood. Burning firewood not only does not fulfill its function, but also becomes unable to maintain the required temperature during combustion. At the same time, the organic matter in the firewood does not burn out completely; when such firewood burns, a suspended amount of smoke is released, which pollutes both the chimney and the furnace space.

What is the moisture content of wood, what does it affect?

The physical quantity that describes the relative amount of water contained in wood is called moisture content. The moisture content of the wood is measured as a percentage.

When measuring, two types of humidity can be taken into account:

• Absolute moisture content is the amount of moisture that is contained in the wood at the current moment in relation to a completely dried tree. Such measurements are usually carried out for construction purposes.
• Relative humidity is the amount of moisture that wood currently contains relative to its own weight. Such calculations are made for wood used as fuel.

So, if it is written that wood has a relative humidity of 60%, then its absolute humidity will be expressed as 150%.

Analyzing this formula, it can be established that firewood harvested from coniferous wood with a relative humidity index of 12 percent will release 3940 kilocalories when burning 1 kilogram, and firewood harvested from hardwood with comparable humidity will already release 3852 kilocalories.

To understand what a relative humidity of 12 percent is, let's explain that such humidity is acquired by firewood, which is dried for a long time on the street.

Density of wood and its effect on calorific value

To estimate the calorific value, you need to use a slightly different characteristic, namely the specific calorific value, which is a value derived from density and calorific value.

Experimentally, information was obtained on the specific calorific value of certain types of wood. Information is given for the same moisture content of 12 percent. Based on the results of the experiment, the following table:

Using the data from this table, you can easily compare the calorific value of different types of wood.

What firewood can be used in Russia

Traditionally, the most favorite type of firewood for burning in brick kilns in Russia is birch. Although, in fact, birch is a weed, the seeds of which easily cling to any soil, it is extremely widely used in everyday life. An unpretentious and fast-growing tree has faithfully served our ancestors for many centuries.

Birch firewood has a relatively good calorific value and burns quite slowly, evenly, without overheating the stove. In addition, even the soot obtained by burning birch firewood is used - it includes tar, which is used both for domestic and medicinal purposes.

In addition to birch, aspen, poplar and linden wood is used as firewood from hardwoods. Their quality compared to birch, of course, is not very good, but in the absence of others, it is quite possible to use such firewood. In addition, linden firewood emits a special aroma when burned, which is considered beneficial.

Aspen firewood gives a high flame. They can be used at the final stage of the firebox to burn off the soot formed by burning other firewood.

Alder also burns quite evenly, and after combustion it leaves a small amount of ash and soot. But again, in terms of the sum of all the quality, alder firewood cannot compete with birch firewood. But on the other hand - when used not in a bath, but for cooking - alder firewood is very good. Their even burning helps to cook food efficiently, especially pastries.

Firewood harvested from fruit trees is quite rare. Such firewood, and especially maple, burns very quickly and the flame reaches a very high temperature during combustion, which can adversely affect the condition of the stove. In addition, you just need to heat air and water in the bath, and not melt the metal in it. When using such firewood, it must be mixed with firewood with a low calorific value.

Softwood firewood is rarely used. Firstly, such wood is very often used for construction purposes, and secondly, the presence of a large amount of resin in coniferous trees pollutes furnaces and chimneys. It makes sense to heat the stove with coniferous wood only after a long drying time.

How to prepare firewood

Firewood harvesting usually begins in late autumn or early winter, before permanent snow cover is established. Felled trunks are left on the plots for primary drying. After some time, usually in winter or early spring, firewood is taken out of the forest. This is due to the fact that during this period no agricultural work is carried out and the frozen ground allows you to load more weight on the vehicle.

But this is the traditional order. Now, due to the high level of development of technology, firewood can be harvested all year round. Entrepreneurial people can bring you already sawn and chopped firewood any day for a reasonable fee.

How to saw and chop wood

Saw the brought log into pieces that fit the size of your firebox. After the resulting decks are split into logs. Decks with a cross section of more than 200 centimeters are pricked with a cleaver, the rest with an ordinary ax.

The decks are pricked into logs so that the cross section of the resulting log is about 80 sq.cm. Such firewood will burn for quite a long time in a sauna stove and give off more heat. Smaller logs are used for kindling.

Chopped logs are stacked in a woodpile. It is intended not only for the accumulation of fuel, but also for drying firewood. A good woodpile will be located in an open space, blown by the wind, but under a canopy that protects the firewood from precipitation.

The bottom row of woodpile logs is laid on logs - long poles that prevent firewood from contacting wet soil.

Drying firewood to an acceptable moisture content takes about a year. In addition, wood in logs dries much faster than in logs. Chopped firewood reaches an acceptable moisture content already in three months of summer. When dried for a year, firewood in a woodpile will receive a moisture content of 15 percent, which is ideal for combustion.

Calorific value of firewood: video

The most progressive type of solid fuel used for heating buildings are pellets. These are solid cylindrical granules 6-10 mm in diameter, obtained by pressing (granulating) waste from various industries - woodworking and agricultural. Their use in the field of heat supply is strikingly different from the combustion of other types of biomass - firewood, coal, sawdust and straw in its pure form.

Why are pellets good?

The advantages of fuel pellets have made them one of the widely used energy carriers in Western Europe:

high bulk density - 550-600 kg/m3, which saves space for fuel storage;

low relative humidity, allowable maximum - 12%;

due to the high degree of compaction and low humidity, pellets are characterized by increased calorific value - from 5 to 5.4 kW / kg;

low ash content - from 0.5 to 3%, depending on the raw material.

The pellets have the size and solid structure to automate the combustion process, while the low ash content makes it last longer without intervention for maintenance.

Thermal equipment that burns pellets is stopped for cleaning from soot on average 1 time per week.

The fuel perfectly tolerates transportation and bulk storage, without collapsing or turning into dust. This allows you to arrange the supply of fuel to high-capacity industrial boilers from special storage facilities - silos, where a monthly supply of pellets is placed.

Fuel pellets are a convenient and environmentally friendly energy carrier that does not form dirt and dust when heating a private house.

Types of waste for the production of pellets

The raw materials for the manufacture of pellets are the following types of waste from various industries:

Wood shavings, sawdust, slabs, wood chips and other substandard wood;

The husk remaining from the processing of sunflower or buckwheat seeds;

Stems of various agricultural crops in the form of straw;

Pellet varieties

Granules are conditionally divided into grades depending on the raw material from which they are pressed. A brief description of the varieties is given in the list:

Pellets of the first grade (white) are made from pure wood of various species without bark impurities. They are distinguished by the lowest ash content - 0.5% and the best calorific value - up to 5.4 kW / kg. It is the best choice for heating your home!

Fuel of the 2nd grade includes various impurities, which is why it is darker in color than the first grade. This also includes granules from cereal straw. Impurities practically do not affect the calorific value of the fuel, but its ash content is higher - 1-1.5%.

Pellets of the 3rd grade with an ash content of 2.5-3% are made from all kinds of agricultural waste. The heat of combustion of such fuel is also quite high - at least 5 kW / kg.

The lowest grade fuel is obtained from peat. In terms of ash content and calorific value, peat pellets lose to the rest and therefore are not very popular.

As a rule, sites for pressing fuel pellets are located on the territory or not far from parent industries that provide them with waste.

About granulation technology

The task of each production process for the manufacture of fuel pellets is to obtain dense and durable cylinders from raw materials with a low moisture content. When granulating wood waste, this is achieved in several stages:

1. First, woodworking waste is sorted into small and large fractions. The former include sawdust and small chips, whose dimensions do not exceed 25 mm with a thickness of 2-4 mm. Chips, branches, slabs and other large wood are sorted and sent for primary crushing.
2. Primary crushing of large waste is carried out by crushers of various types. The task is to obtain wood particles of the specified sizes. The crushed raw material is moved to the next stage by pneumatic transport or by means of a screw conveyor.
3. Secondary crushing goes through the entire mass of raw materials, turning into a fine fraction. The maximum particle size at the outlet is 4 mm with a thickness of 1.5 mm.
4. Drying. To obtain high-quality fuel with high heat transfer, it is necessary to remove all excess moisture from the tree, which in freshly cut branches reaches 50%. The process takes place in a special drum or other type drying chamber. At the outlet, the moisture content of the raw material should not exceed 12%.
5. Humidity adjustment. Since initially waste with different moisture content gets into the work, at the previous stage, part of the raw material is overdried, that is, its moisture content is less than 8%. This is not enough to form a strong granule. Therefore, a certain amount of steam is supplied to the hopper with the raw mass. Wood comes to granulation with humidity from 8 to 18%.
6. Granulation. Here, presses are used - granulators with a cylindrical or flat matrix (thick metal with calibrated holes). The raw material coming from the hopper is pressed into the holes by steel rollers that move at high speed inside the matrix. During this process, the already heated and crushed mass of raw materials is heated to an even higher temperature of over 100 degrees Celsius. This is due to the high pressure during granulation. A binding substance, lignin, is released from the raw material. This is facilitated by the level of humidity, which is achieved during the adjustment. In addition, from a pressure of 30-40 MPa, the mass spontaneously heats up to temperatures above 100 degrees Celsius. To remove excess mass, grooves are cut on the surface of the rollers.
7. Raw pellets are sent by pneumatic transport or auger to the secondary drying and cooling chamber, where they are blown by powerful fans and finally harden.
8. The last stage is packing in plastic bags or big bags. Products can be dispensed to large customers in bulk.

The principle of granulation does not involve the use of third-party binders and additional heating of raw materials.

The pressing of fuel pellets from straw is somewhat simpler, since sorting and primary crushing are excluded from the technological process. When granulating the husks from sunflower seeds, the drying stage is also excluded. The reason is that the seed processing waste initially has a moisture content close to the required one, and is immediately sent for adjustment and pressing.

Comparison with other solid fuels

The strength of pellets is their progressiveness compared to wood, coal and even briquettes. Imagine a solid fuel boiler operating in the same mode as a gas boiler. Only even safer because pellets don't explode like natural gas.

The difference between gas and pellet heating is expressed in several points:

The supply of pellets must be replenished;

Once a week, the boiler stops for cleaning;

During the operation of the pellet heat generator, the noise of pellets pouring down the plastic pipe is heard;

The use of this fuel is not related to the work of utilities and various inspections;

Heating equipment that burns pellets is automated no worse than gas.

If we compare granulated waste with firewood or coal, then the latter win only in terms of cost.

In return, they take away comfort and time from the homeowner, as wood or coal heating requires constant attention. Even a long-burning boiler needs to be “feeded” 2 times a day and constantly cleaned, while a pellet one works non-stop for weeks.

The results of comparison according to other criteria also speak in favor of heating with pellets:

Burning pellets is safer than wood and coal. Boilers equipped with pellet burners practically do not suffer from inertia, like conventional solid fuel ones. When the required coolant temperature is reached, the burner turns off and the fuel supply stops. Only a small handful of pellets burn out.

The room with the pellet boiler is clean, there is no smell of smoke, which is present when the furnace is loaded with coal and firewood.

Installation of a buffer tank - at the request of the owner. Pellet heat generators can do without a battery to dump excess heat.

Comparison of the technical characteristics of different types of biomass fuels

The actual heat transfer of energy carriers may differ from the theoretical one and depends on the efficiency of your heating equipment and the moisture content of the raw materials you purchased.

It should be borne in mind that not the highest quality granules - agropellets - take part in the comparison. Pellets from wood waste show themselves even better.

Fuel briquettes have excellent performance in all criteria, but they lose to pellets in terms of the degree of automation of heating equipment.

Briquettes, like firewood, must be put into the firebox by the owner of the house. There are very few disadvantages of granular fuel:

The high cost of boiler equipment and automation. The price of a medium quality pellet burner is comparable to a conventional solid fuel boiler with a power of up to 15 kW.

Granules must be stored under certain conditions so that they do not become saturated with moisture and do not crumble. The method of storing a pile under a canopy is categorically not suitable, you will need a closed room or a container like a silo.

In the use of pellets for heating, there are several secondary advantages that also do not hurt to take into account:

Use of pellets

The combustion of pellets not only produces little ash, but also leaves much less soot on the inner walls of the chimney;

The combustion mode and the design of the burners make it possible to use fuel energy more efficiently than wood, the efficiency of pellet boilers reaches 85%;

The automation of a pellet heat generator interacts well with automatic control devices for water heating systems, including underfloor heating.

From an environmental point of view, the expansion of the production and use of pellets reduces a huge amount of various waste, which has a very beneficial effect on the environment around us.

Now these wastes are simply burned, polluting the atmosphere, or taken to landfills. The problem of utilization of husks from seeds is faced by many enterprises producing sunflower oil. Hence the conclusion: the production and burning of pellets is not only comfortable and safe, it helps to protect the environment and the "green lungs" of the planet - the forest.

Buy first class pellets from suppliers who are responsible for their storage and compliance with a certain humidity. In some cases, it is justified to purchase pellets not in bags of 20-25 kilograms, but in one or several big bags at once, with this approach you can demand a significant discount;

Determining the quality of pellets can be quite simple: good pellets are hard, dry and do not crumble into dust even with strong squeezing. When a pellet breaks, it breaks up into two or more particles without dust and turns into dust. The appearance is glossy and shiny;

Store pellets in a dry place with low humidity, avoiding the presence of open flames near them;

Use pellets only in specially designed pellet boilers. Experience shows that combined boilers have a number of problems associated with both insufficiently debugged fuel combustion process and increased soot formation in the chimney and other unpleasant problems. Specialized boilers are devoid of such problems.

According to http://energylogia.com

gkx.by

Comparative table of calorific value of some types of fuel

Type of fuel	Unit rev.	Specific heat of combustion			Equivalent
		kcal	kW	MJ	Natural gas, m3	Diz. fuel, l	Fuel oil, l
Electricity	1 kWh	864	1,0	3,62	0,108	0,084	0,089
Diesel fuel (diesel fuel)	1 l	10300	11,9	43,12	1,288	-	1,062
fuel oil	1 l	9700	11,2	40,61	1,213	0,942	-
Kerosene	1 l	10400	12,0	43,50	1,300	1,010	1,072
Oil	1 l	10500	12,2	44,00	1,313	1,019	1,082
Petrol	1 l	10500	12,2	44,00	1,313	1,019	1,082
natural gas	1 m 3	8000	9,3	33,50	-	0,777	0,825
Liquefied gas	1 kg	10800	12,5	45,20	1,350	1,049	1,113
Methane	1 m 3	11950	13,8	50,03	1,494	1,160	1,232
Propane	1 m 3	10885	12,6	45,57	1,361	1,057	1,122
Ethylene	1 m 3	11470	13,3	48,02	1,434	1,114	1,182
Hydrogen	1 m 3	28700	33,2	120,00	3,588	2,786	2,959
Hard coal (W=10%)	1 kg	6450	7,5	27,00	0,806	0,626	0,665
Brown coal (W=30…40%)	1 kg	3100	3,6	12,98	0,388	0,301	0,320
Anthracite coal	1 kg	6700	7,8	28,05	0,838	0,650	0,691
Charcoal	1 kg	6510	7,5	27,26	0,814	0,632	0,671
Peat (W=40%)	1 kg	2900	3,6	12,10	0,363	0,282	0,299
Peat briquettes (W=15%)	1 kg	4200	4,9	17,58	0,525	0,408	0,433
Peat crumb	1 kg	2590	3,0	10,84	0,324	0,251	0,267
wood pellet	1 kg	4100	4,7	17,17	0,513	0,398	0,423
straw pellet	1 kg	3465	4,0	14,51	0,433	0,336	0,357
Sunflower husk pellet	1 kg	4320	5,0	18,09	0,540	0,419	0,445
Freshly cut wood (W=50...60%)	1 kg	1940	2,2	8,12	0,243	0,188	0,200
Dried wood (W=20%)	1 kg	3400	3,9	14,24	0,425	0,330	0,351
Wood chips	1 kg	2610	3,0	10,93	0,326	0,253	0,269
Sawdust	1 kg	2000	2,3	8,37	0,250	0,194	0,206
Paper	1 kg	3970	4,6	16,62	0,496	0,385	0,409
Sunflower husk, soy	1 kg	4060	4,7	17,00	0,508	0,394	0,419
Rice husk	1 kg	3180	3,7	13,31	0,398	0,309	0,328
Bonfire linen	1 kg	3805	4,4	15,93	0,477	0,369	0,392
Corn on the cob (W>10%)	1 kg	3500	4,0	14,65	0,438	0,340	0,361
Straw	1 kg	3750	4,3	15,70	0,469	0,364	0,387
cotton stalks	1 kg	3470	4,0	14,53	0,434	0,337	0,358
Vine (W=20%)	1 kg	3345	3,9	14,00	0,418	0,325	0,345

ecoles-nn.ru

Pellets

Pellets are fuel pellets made from wood waste. Most often, sawdust is used for the production of pellets. Currently, there is a trend towards an increase in the use of recyclables. The production of pellets is the most promising area for the use of wood waste.

The characteristics of pellets directly depend on the composition of the product. In their production, both pure wood and wood mixed with bark can be used. Sometimes straw, sunflower husks, and grain waste are added to the granules.

Classification of pellets by feedstock:

· White pellets are considered Premium grade, light in color, made from wood without the use of bark. The calorific value of white pellets is 17.2 MJ/kg. There is very little ash when cleaning the boiler. Premium pellets account for more than 95% of all pellet production and are burned in any stove suitable for standard or premium quality fuels.

• Industrial pellets are a lower quality grade. The composition of the product includes: bark and fireproof residues. The ash content of such pellets is slightly higher than that of the Premium grade, but the calorific value is almost the same. The boiler will need to be cleaned more often.
• Agropellets are fuel of standard quality from buckwheat waste, sunflower seeds. Pellets are dark in appearance. The calorific value is 15 MJ / kg, and the ash content is more than 4%. The main advantage of this type of fuel is their low price. Most often they are used for combustion in large thermal power plants. The use of this type of fuel requires daily cleaning of the boiler.

What caused such a great interest in this type of fuel?

Wood pellets are the fuel of the future. Their heat of combustion is 4.3 - 4.5 kW / kg, which is one and a half times more than that of wood, but the heat transfer is comparable to coal. During combustion, emissions to the atmosphere are minimal. Burning 2 tons of fuel pellets gives the same amount of thermal energy as burning 957 m3 of gas, 1000 liters of diesel fuel, or 3.2 tons of wood.

During the combustion of pellets, a large amount of heat is released, and combustion proceeds in an even layer, as in the combustion of traditional fuels. Fuel pellets do not require a large amount of storage space.

Pellets have a high energy concentration with an insignificant volume. Their high bulk density makes it possible to move fuel over long distances with high economic justification. Pellets reduce the risk of fires, explosions and leakage during transport.

The consumption of pellets for heating a house with an area of ​​150 square meters for a heating season of 7 months will require no more than 5 tons of pellets, and after combustion, the product can be used as a fertilizer in the fields. The mass of ash is approximately 1% of the total mass of fuel pellets.

Efficiency of pellets as a type of fuel

Characteristics of wood pellets have indicators:

• Released energy during combustion - 5 kW / kg;
• Ash content - no more than 5%;
• Length - from 5 to 40 mm;
• Density of pellets 1200-1400 kg/m3;
• The bulk density of the product for transportation and storage is 650 kg/m3;

Packing and packing:

Packing and packaging of fuel pellets depends on what kind of storage system the consumer will provide them with:

• in free form - in bulk;
• in big-bag bags, from 500 to 1200 kg;
• in small packaging - from 10 to 15 kg.

www.svirpellets.com

Calorific value of wood

The calorific value of wood, it is the heat of combustion of wood, it is also the calorific value of wood

Wood is a very diverse natural heating material in terms of its properties, which belongs to renewable fuels. The heating value of wood is determined by its calorific value and depends on many factors, each of which can have very wide deviations from the norm. Therefore, the theoretical definition is purely general in nature and gives only approximate figures. An accurate determination of the calorific value of wood is possible only in laboratory conditions and will be true only for the sample under study. At the same time, it (the sample) is simply burned in the calorimeter and the result is looked at. The calorific value of wood and the calorific value of firewood are concepts that are close in meaning. About the calorific value of firewood in more detail - “Firewood | Calorific value of firewood»

1. wood substance
2. Calorific value of wood
3. Calculation of the calorific value of wood

Table of specific calorific value of wood for different types of wood

wood species	Absolute (highest) calorific value of wood (kcal/kg)	Working (lower) mass calorific value of wood (kcal/kg)	Working (lower) volumetric calorific value of wood (kcal / dm3)	Density of wood (kg/dm3)	Wood density limit (kg/dm3)
Oak	4753	4000	3240	0,810	0,690-1,03
Ash	––||––	––||––	3000	0,750	0,520-0,950
Rowan (tree)	––||––	––||––	2920	0,730	0,690-0,890
Apple tree	––||––	––||––	2880	0,720	0,660-0,840
Beech	––||––	––||––	2720	0,680	0,620-0,820
Acacia	––||––	––||––	2680	0,670	0,580-0,850
Elm	––||––	––||––	2640	0,660	0,560-0,820
Larch	––||––	––||––	2640	0,660	0,470-0,560
Maple	––||––	––||––	2600	0,650	0,470-0,560
Birch	––||––	––||––	2600	0,650	0,510-0,770
Pear	––||––	––||––	2600	0,650	0,610-0,730
Chestnut	––||––	––||––	2600	0,650	0,600-0,720
Cedar	––||––	––||––	2280	0,570	0,560-0,580
Pine	––||––	––||––	2080	0,520	0,310-0,760
Linden	––||––	––||––	2040	0,510	0,440-0,800
Alder	––||––	––||––	2000	0,500	0,470-0,580
Aspen	––||––	––||––	1880	0,470	0,460-0,550
Willow	––||––	––||––	1840	0,460	0,490-0,590
Spruce	––||––	––||––	1800	0,450	0,370-0,750
Willow	––||––	––||––	1800	0,450	0,420-0,500
Hazelnut	––||––	––||––	1720	0,430	0,420-0,450
Fir	––||––	––||––	1640	0,410	0,350-0,600
Bamboo	––||––	––||––	1600	0,400	0,395-0,405
Poplar	––||––	––||––	1600	0,400	0,390-0,590

1. All indicators of the table, except for the absolute (highest) calorific value, correspond to a wood moisture content of 12%
2. The wood density values ​​are taken from the Handbook of Aircraft Material Weights, ed. "Engineering" Moscow 1975

wood substance

Wood substance is the material that makes up the walls of wood cells. Wood substance is a solid wood mass without intracellular voids and pericellular cavities. The chemical composition of the wood substance is almost always the same for wood of all tree species. It includes approximately 60% cellulose, 30% lignin, 7...9% associated hydrocarbons and 1...3% minerals. Accordingly, the specific gravity of the wood substance for different tree species is not very different and is approximately equal to 1540 kg/m3. This is more than the density of water. And, if the wood did not have a hollow-cellular structure of its structure and there were no intracellular voids and pericellular cavities in it, then it (wood) would sink in water, like a stone. Wood substance (the material of the walls of wood cells) is the main calorific component of wood, which burns with the release of heat.

The production (pressing) of wood heating briquettes, eurofirewood and pellets is nothing more than an attempt to compact the hollow-cellular structure of wood to the state of wood substance density. The density of high-quality compressed wood fuel is always above unity and starts from 1.1 g/cm3

Calorific value of wood

The calorific value, (calorific value, calorific value) of wood is the amount of heat that is generated during the combustion of wood. Rather, the calorific value of wood is the amount of heat that is generated during the combustion of a wood substance (the main calorific component of wood) and associated hydrocarbons (resins and essential oils).

An important point. When wood burns, water vapor is formed. The formation of water vapor has a dual nature of origin. Firstly, wood is very hygroscopic, and free water is simply found in its voids and cavities. Secondly, water molecules are synthesized directly in the process of combustion (temperature decomposition and oxidation) of hydrocarbon compounds, of which, in fact, all wood consists.

Depending on whether or not the heat of combustion of the fuel is taken into account, spent on the evaporation (synthesis) of water and the heating of water vapor - there are higher and lower (absolute and working) calorific value of wood

Specific calorific value of wood

The calorific value of wood, related to the occupied unit of mass or volume of fuel, is called the specific heat of combustion (specific calorific value) of wood. The specific calorific value of wood is the amount of heat that is released during the complete combustion of its mass or volume unit (kg, tons or dm3, m3). The value of the specific calorific value of wood is determined by the amount of combustible material contained in its unit of weight or volume.

Depending on whether the fuel was accounted for in mass or volume units, the specific calorific value of wood can be mass or volume.

Units for measuring mass specific calorific value: J/kg, kcal/kgUnits for measuring volumetric specific calorific value: J/dm3, kcal/dm3

For practical purposes, the volumetric specific calorific value of wood is of greater interest. Since, traditionally, firewood is taken into account in volumetric units of measurement (warehouse meters and cubic meters), it is the volumetric calorific value of wood that comes to the fore and becomes a decisive factor in determining the quality of firewood as a type of fuel.

Higher (absolute) calorific value of wood

The calorific value of wood is called the highest or absolute, if the heat of condensation of water vapor formed during the combustion process is taken into account.

The highest (absolute) calorific value of wood is determined by complete combustion of the studied fuel sample in the calorimeter, followed by condensation of water vapor and cooling of all combustion products to the initial temperature. 1 kg of absolutely dry wood is taken as a sample

Under absolutely dry wood is meant the humidity of such a sample of wood, at which it, being in a drying cabinet with a drying temperature of 102 ... 103ºС, does not change its mass value by more than 1% within three days

Lower (working) calorific value of wood

The calorific value of wood is called lower or working if the heat of condensation of water vapor formed during the combustion process is not taken into account.

The heat of condensation of water vapor formed during combustion is called the latent heat of combustion.

In practice, it is never possible to cool the products of combustion to the state of complete condensation of water vapor. Therefore, the working (lower) calorific value of wood has a wide practical application.

The net and gross calorific values ​​of wood are related as follows: Gross calorific value = net calorific value + latent heat of combustion, or so:

The lower (working) calorific value of wood is determined by complete combustion of the test sample in the calorimeter without subsequent cooling of all combustion products to the initial temperature and without condensation of water vapor. At the same time, the test sample is not dried and burned "as is". Before laboratory studies, they simply fix the moisture content of the sample and then, be sure to indicate at what moisture content of the wood the result was obtained to determine its calorific value.

The lower (working) calorific value varies depending on the degree of moisture content of the wood, since the moisture content of wood is a very changeable value.

The working (lower) calorific value of wood is always less than the absolute

Lower (working) mass specific calorific value of wood

The working (lower) calorific value of wood, referred to a unit mass of fuel, is called the working (lower) mass specific calorific value of wood, or simply - mass specific calorific value. Mass specific calorific value is measured in J / kg, cal / kg, or in multiples of them.

From the definition of the working calorific value of wood, the following follows:

1. The mass specific working calorific value of wood does not depend much on the type of wood, since 1 kg of absolutely dry wood of any type of wood contains an approximately equal amount of a combustible substance that is similar in composition (see Wood substance).
2. The mass specific working calorific value of wood directly depends on its moisture content.

The reasons for the dependence of the mass specific working calorific value of wood on its moisture content:

1. Reducing the amount of combustible substance by an amount equal to the weight of moisture. So, 1 kg of wet wood contains pure combustible wood substance in an amount equal to 1 kg minus the weight of moisture. At a time when 1 kg of absolutely dry wood will contain exactly 1 kg of clean fuel.
2. Increasing the latent heat of combustion, i.e. increase in heat loss for moisture evaporation and heating of water vapor to the average temperature of combustion products (≈800...1100°C).

Lower (working) volumetric specific calorific value of wood

The working (lower) calorific value of wood, referred to a unit volume of fuel, is called the working (lower) volumetric specific calorific value of wood, or simply - volumetric specific calorific value. Volumetric specific calorific value is measured in J / dm3, kcal / dm3, or in multiples of them.

The volumetric specific calorific value of wood depends on its density, i.e. from the concentration of wood substance in a unit volume of fuel

Explanation:

Wood has a porous-cellular structure. Intracellular cavities and pericellular voids reduce the amount of combustible wood substance contained in a unit volume of fuel. The denser the wood, the less voids in its volume and, accordingly, the greater the concentration of combustible wood substance, the greater the volumetric calorific value of such wood.

Volumetric specific calorific value directly depends on the type of wood, since different types of trees have a different density of their wood and, accordingly, a different amount of combustible (calorific) substance per unit volume

Volumetric specific calorific value is determined individually for each type of wood, is a reference value and has the greatest practical application (see Table of specific calorific value of wood for different types of wood). And since the lower calorific value of wood is dependent on its moisture content, then in such tables it is necessary to indicate for what moisture content of wood the values ​​​​of its calorific value are given.

The volumetric specific heat of combustion of wood is widely used in practice as a qualitative and quantitative characteristic of the calorific value of firewood.

Once again: The volumetric specific working calorific value of wood directly depends on the density of the wood and its moisture content. The volumetric specific working calorific value of wood can vary over a very wide range, since the density of wood and its moisture content are very unstable and variable values.

Calculation of the calorific value of wood

1. Calculation of the absolute (gross) calorific value of wood

Explanation to the calculation: In laboratory experiments to determine the gross calorific value of wood, an absolutely dry sample, weighing 1 kg, appears. Obviously, in this case, we are talking more about the absolute calorific value of the material of the walls of wood cells - wood substance. For what else can be in a piece of absolutely dry wood, weighing 1 kg?

The answer is more than simple - in 1 kg of absolutely dry wood, other hydrocarbon compounds that are not woody substances may be present. First of all, these are polyester resins and oils, which are especially rich in coniferous wood.

Since the elemental chemical composition of the wood substance is almost always the same, and the percentage difference between the weight calorific value of the wood substance and hydrocarbons replacing it does not significantly affect the calorific value per unit mass of fuel, then for further calculations of the calorific value of wood, we take it as an axiom:

The highest (absolute) calorific value of 1 kg of wood depends little on the type of wood, is fundamentally equal to the value of the absolute (highest) calorific value of the wood substance and corresponds to ≈ 4752.9 kcal / kg

Calculation progress: The gross calorific value (VTS) of wood is defined as the sum of the calorific values ​​of all its individual chemical elements and is calculated according to the Mendeleev formula: Q (VTS) \u003d 81C + 300H - 26Owhere C, H and O are the percentage of carbon, hydrogen in the fuel and oxygen

The composition of the wood substance for any type of wood: 49.5% carbon, 6.3% hydrogen, 44.1% oxygen

Accordingly, we get: Q (VTS) \u003d 81 x 49.5 + 300 x 6.3 - 26 x 44.1 \u003d 4752.9 kcal / kg (The resulting value will be used in the Nadezhdin formula when determining the working mass specific calorific value of wood for a moisture content of 12% )

2. Calculation of the specific mass working (lower) calorific value of wood

The mass working calorific value of wood (MRTS) is determined by the Nadezhdin formula and depends on the moisture content of firewood:

for room-dry wood, humidity 7...18% Q(MRTS) = 4600 - 50 x W = 4600 - 50 x (7...18) = 4250...3700 kcal/kg for air-dry wood, humidity 25...30% Q(MRTS) = 4370 - 50 x W = 4370 - 50 x (25...30) = 3120...2870 kcal/kg for driftwood, humidity 50...70% Q (MRTS) = 3870 - 45 x W = 3870 - 45 x (50...70) = 1620...720 kcal/kg

where W is the relative humidity of wood in percent, 4600, 4370, 3870 are the values ​​of the mass absolute (higher) calorific value of wood, which are calculated individually for each sample, based on the percentage of absolutely dry wood substance and the moisture contained in it.

Accordingly, for a humidity of 12%: Q (MRTS) = 4600 - 50 x 12 = 4000 kcal / kg

3. Calculation of the specific volumetric working (lower) calorific value of wood

The volumetric working calorific value of wood (VHF) is determined by multiplying the mass working calorific value by the density of the wood.

For example, average calorific value for ash: 4000 kcal/kg X 0.750 kg/dm3 = 3000 kcal/dm3 Lower calorific value for ash: 4000 kcal/kg X 0.520 kg/dm3 = 2800 kcal/dm3 Upper calorific value for ash: 4000 kcal/kg X 0.950 kg/dm3 = 3800 kcal/dm3

where, 0.750 kg/dm3 is the average density of ash wood 0.520 kg/dm3 and 0.950 kg/dm3 are the lower and upper limits of density deviation for ash wood

The density (specific gravity) of wood for different types of wood is taken from the "Handbook on the masses of aviation materials" ed. "Engineering" Moscow 1975 (see wood density table)

Based on the wood density table, the mass specific calorific value from Nadezhdin was converted to volumetric calorific value depending on the type of wood, at a moisture content of 12%.

Based on the results of the calculation, from the data obtained, the following table was compiled: Table of specific calorific value of wood for different types of wood

Conversion of units of volumetric calorific value of wood

The site tehnopost.kiev.ua offers a unique online calculator for converting units of volumetric calorific value of wood, firewood and other types of fuel.

Volumetric Calorific Value Converter (J/cm3, Cal/cm3)

Additionally, the site tehnopost.kiev.ua offers a set of online calculators for direct and reverse conversion of alternative units of measurement of physical quantities related to heat engineering and thermodynamics.

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Heat engineering online converters on tehnopost.kiev.ua

1. Calories =>
2. Kilocalories => to joules, kilowatt hours and their multiples
3. Megacalories => to joules, kilowatt hours and their multiples
4. Gigacalories => to joules, kilowatt hours and their multiples

1. Joules =>
2. Kilojoules => to calories, kilowatt hours and their multiples

1. Kilowatt hours => to Joules, calories and their multiples

1. Units of volumetric calorific value (J/cm3, cal/cm3)

Download the program "Converter of units and quantities"

Calorific value of wood, firewood on tehnopost.kiev.ua

1. wood substance
2. Calorific value of wood
3. Specific calorific value of wood
4. Higher (absolute) calorific value of wood
5. Lower (working) calorific value of wood
6. Lower (working) mass specific calorific value
7. Lower (working) volumetric specific calorific value
8. Calculation of the calorific value of wood
9. Table of specific calorific value of wood for different types of wood
10. Conversion of units of volumetric calorific value of wood

Alternative heating: wood wood heat firewood calorific value combustion fuel

tehnopost.kiev.ua

Coal or wood pellets?

Now let's analyze each item of qualitative characteristics:

the lowest calorific value (working), kcal / kg is the amount of heat released during the combustion of fuel, taking into account the heat costs for the evaporation of moisture contained in the product.

Sometimes they confuse the highest calorific value and the lowest, indicate the one that you want to show in the calculations, and the difference between them is big! The gross calorific value does not take into account the heat costs for moisture evaporation (i.e., as if there is no moisture in the product). For example, in our case, the higher calorific value of coal is 5900 kcal/kg, and for wood pellets 4900 kcal/kg.

To sum up the comparison in terms of calorific value, it can be said more simply - to heat the same amount of coolant in the heating system, it will be necessary to burn less coal than wood pellets.

Ash content (average),% - this is an indicator that ultimately indicates how much unburned residue remains and how often it will be necessary to clean the ash collector. According to this indicator, wood pellets are more convenient to use - they burn out almost completely, so the ash will have to be "raked out" much less often.

Moisture (average), % - characterizes the moisture content in the product, which in turn affects the calorific value of the fuel. But since we compared the net calorific value, the moisture content was already taken into account.

The yield of volatile substances,% - the value of this indicator depends on how quickly the fuel will ignite and how long it will burn. Pellets light up faster and quickly release heat, but at the same time they burn out just as quickly, so the design of the boiler must provide for this property of the pellets. Coal flares up more slowly, but it burns longer and heat transfer is more stable.

Possibility of use for burning in automatic boiler rooms -

Today there are a large number of different automated boilers that work on pellets, on coal, as well as universal ones - working both on coal and on pellets. There is practically no difference in the degree of automation of fuel supply and combustion process control when using coal and pellets. It all depends on the fuel used (fractional composition and quality characteristics).

Assessment of emissions of pollutants from the combustion of coal and wood pellets - this indicator can be used to evaluate and compare the "environmental friendliness" of each type of fuel.

The main points are the release of carbon dioxide and sulfur dioxide (mixing with moisture, it forms acid). According to these indicators, wood pellets are more environmentally friendly than coal and air pollution during their combustion is lower. Although, when using modern boiler equipment, the degree of atmospheric pollution during coal combustion is largely reduced (it is not for nothing that automatic coal-fired boilers are used quite widely in Europe).

But it is necessary to pay attention to the characteristics of the fuel - varieties of coal, and pellets, which are quite large, so be sure to look at the quality indicators of the fuel that you purchase.

centcoal.com

Prices and news on the forest and lumber market

News & Events

Production volumes of "Fuel pellets from wood waste" (pellets) in Russia as a whole in 2018 For the period from January to August, the production of pellets from wood waste as a whole by...

pellet in 2017 on a global scale is 60% of the output, which corresponds to the level of 18.74 million tons. Among the leaders in the export of pellets are such countries as the USA, Canada, Latvia, Russia, Vietnam, Estonia, etc.

The leading producer of pellets in the world is the undisputed leader in the production of these products - the United States. The share of this country today accounts for 22% of the world production of pellets. Recall that it was in the United States in the 90s of the XX century that the ...

trends of the modern world, and the transition to pellet products from wood waste puts the pellet industry among the priorities. Large-scale production of pellets has more than 25 years - the first pellet plants...

Chipboard, fiberboard and MDF. Over the past five years, the production of OSB boards has been actively developing. The production of pellets in Russia is no more than ten years old. Since 2012, pellet production has been growing at a high rate.

for softwood lumber, the growth is insignificant, +0.1%. In general, the level of sawn timber output in Russia increased by 1%. Pellet production, according to data for the first half of 2018, decreased by 3.3%. 8.5% down...

Information

Infographics. Pellet production volumes in the Russian Federation in 2018 Export prices of the global pellet market World leaders in pellet production

Directory of organizations and enterprises

Manufacture and sale of equipment for the production of pellets: press granulators, granulators, flat die granulators, mini-granulators, sawdust dryers, wood waste crushers, hammer crushers, chippers, coolers and screeners...

Sale of cereals, steel products, ferroalloys, packaging, fuel pellets...

Wholesale of pellets. Wood pellets available. Pellets 6mm. Pellets 8mm...

LLC "Pellet Systems" produces and sells fuel granules (pellets) from coniferous wood shavings. Pellets diameter 6 and 8 mm.

Fuel supplies to organizations, own production of fuel wood briquettes, pellets. Delivery to regions.

A set of measures for subscriber and service maintenance of solid fuel boilers. Supply of fuel - wood pellets (pellets) and coal.

Offers for the purchase and sale of products

Green Board slabs The Green Board® slab system is a multifunctional, environmentally friendly and safe building material that meets all the criteria for a comfortable and safe home. Plates Green...

Branch and branch chipper, wood and wood waste chipper BOXER BX92 R Wood waste chipper BOXER BX92 R (trunks, branches, bark, leaves, needles, etc.) has the ability to convert...

Pellets are fuel pellets made from wood waste. Most often, sawdust is used for the production of pellets. As the current trend is to increase the use of...

Laboratory filter paper is produced in accordance with GOST 12026-76. Produced in sheets and rolls. * Designed to filter water, oil and other substances containing suspended impurities...

Plate OSB(OSB)-3 moisture resistant 10 mm 2500x1200mm. OSB (OSB) oriented strand board is made from thin wood chips bonded with synthetic resin. Multi-layer bond provides...

Plate OSB(OSB)-3 moisture resistant 12mm 2500x1200mm. OSB (OSB) oriented strand board is made from thin wood chips bonded with synthetic resin. Multi-layer communication provides...

GOSTs, TUs, standards

Water in the water supply network in front of the dispenser, MPa (kgf/cm2) 0.06 (0.6) Maximum water heating temperature, K (°С) 353 (80) Duration of heating of the full volume of water in the water tank with fuel calorific value of 2440 kcal/ kg, min, no.

3.11 The specific volumetric calorific value (calorific value) of natural gas is the amount of heat that is released during the complete combustion of gas in air at a constant pressure pc and a constant temperature Tcg, divided by volume ...

3.16.2. Determination of the calorific value of high-calorie gases - according to GOST 10062-75. The calorific value of low-calorie gases should be determined from their composition.

3.1.15 calorific value of hydrocarbon fuels: The total amount of energy that natural hydrocarbon fuels possess, releasing it under regulated conditions.

3.1.17 calorific value of hydrocarbon fuels: The total amount of energy that natural hydrocarbon fuels possess, releasing it under regulated conditions.

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what is it and what are they made of

In our time, the issue of preserving the environment is acute. First of all, this concerns the fuel that is burned in furnaces at factories and in boilers for heating residential buildings. For many years, coal was considered the most common type of solid fuel, but the extraction of such fuel is becoming more and more difficult and expensive. Because of this, many companies are switching to a new type of fuel - pellets. But what is it?

0.1. Biofuel - pellets

1. Pellets what is it

Pellets are a new type of solid biofuel. In fact, pellets are firewood. They are made by pressing waste in the woodworking industry:

• Chips;
• sawdust;
• Shavings;
• wood dust;
• tree bark and so on.

In addition, pellets can be made from other raw materials, such as:

• Straw;
• Sunflower husk;
• Nut shell;
• Peat;
• Reeds;
• Cake of grapes and so on.

The production of pellets requires special equipment, which is available in Russia. At the same time, there are both mobile models of machines that can be used for private purposes, as well as entire industrial lines that are characterized by increased productivity.

It is worth noting that the production of pellets is not only a profitable business, but also the production of environmentally friendly biofuels. Such production makes it possible to utilize waste from the agricultural and woodworking industries.

The quality of pellets, as well as their calorific value, directly depends on the raw materials from which they are made. Thus, buyers often face the question, which pellets are better? To answer this question, it is necessary to analyze the types of pellets in more detail.

1.1. straw pellets

Straw is a great alternative to wood waste. In terms of calorific value, straw pellets are not inferior to wood pellets. At the same time, straw is a cheap and widespread raw material that is constantly renewed. In addition to straw, husks from corn and other crops can also be used for the production of pellets.

The properties of straw, of course, differ from sawdust. It contains a large amount of volatile substances, which are characterized by low density. In addition, these substances burn for a relatively long time. It is also worth noting that straw pellets have a higher calorific value than wood pellets. This difference is not significant, however, nevertheless, it can become a determining factor.

Unlike wood pellets, straw pellets are highly resistant to moisture. This means that the storage of such fuel does not require a dry room, as is the case with wood pellets. The only indicator by which straw pellets are inferior to wood pellets is the ash content. The ash content of straw pellets is about 5.5%, while wood pellets have an ash content of only 1.5%.

However, despite this indicator, straw biofuel is a promising type of energy, and the production of such pellets today is a very profitable business. In addition, unlike wood, straw is a rapidly renewable raw material.

1.2. Sunflower husk pellets

Another alternative to wood pellets is biofuel, which is made from sunflower husks. Before the advent of pellet production technologies, sunflower husks were used only for the production of cake, which was used in agriculture. However, today this type of raw material has found a more efficient use in the production of fuel.

Pellets from sunflower husks are also almost as good as pellets made from wood. When burned, husk pellets release the same amount of energy as wood pellets. However, as with straw, biofuel production from husks requires a rapidly renewable feedstock. In terms of ash residue, such pellets are superior to straw fuel, but still inferior to wood pellets. The ash content of such fuel is 3.6%.

In addition to sunflower husks, pellets can also be made from pumpkin seed husks, walnut shells, as well as grape cake and other crops. Such production also allows you to get rid of waste, turning it into a valuable fuel. In turn, the manufacturer of such fuel literally makes money on garbage.

1.3. Peat pellets

Until recently, peat extraction was a loss-making business. Today, however, peat deposits have again come under the attention of fuel producers. After the development of biofuels in granules, people began to use all kinds of waste from the agricultural and woodworking industries. Peat is also an excellent raw material for the production of biofuels.

Peat pellets have a characteristic black color. According to its abilities, such fuel is considered one of the best options for heating equipment. Peat granules have the following characteristics:

• Efficient combustion of fuel increases the efficiency of the boiler. At the same time, the ash content is 2.2%, which is the second indicator after wood pellets;
• Peat pellets do not have hidden pores. They are not prone to spontaneous combustion even at elevated ambient temperatures;
• Like any other, peat pellets are made without the use of chemicals, which makes them an environmentally friendly fuel that does not form hazardous compounds when burned;
• When burning 1 ton of peat pellets, the same amount of energy is released that is released when burning 1.6 tons of wood, 475 m3 of gas, 0.5 tons of diesel fuel or 685 liters of fuel oil. These are quite high figures, especially considering the cost of such fuel.

2. Pellets as a new type of fuel: Video

2.1. Reed pellets

In all respects, fuel pellets made from reeds are in no way inferior to peat pellets, as well as pressed straw. Moreover, reed pellets burn with less sulfur and carbon dioxide, which has a positive effect on the environment. This type of fuel has no unpleasant odor and can be used as a natural adsorbent.

Such fuel is widely used for heating fireplaces and boilers for heating private houses. In addition, such pellets are quite successfully used in heating equipment, which provides heat to entire streets and quarters. In terms of calorific value, reed pellets are inferior to wood pellets, however, the cost of such fuel is significantly lower.

2.2. Biofuel - pellets

Now you know what pellets are. This is an alternative type of fuel, which is already actively used today in many areas of industry. In addition, fuel pellets are used for private purposes, for heating houses and burning fireplaces. The main feature of such fuel is its low cost and high calorific value. Moreover, regardless of the raw materials from which the pellets were made.

Among other things, this type of biofuel emits much less smoke during combustion, is practically odorless and does not emit compounds hazardous to health. Pellet production is a profitable business, especially considering that this is a young industry, and there is no fierce competition in Russia yet.

However, mainly pellets are a great alternative to all traditional fuels. Thanks to this, people will soon be able to completely abandon expensive coal mines.