Volatile yield and properties of coke. Yield of volatile substances

Lab #3

Determination of the calorific value of coals according to their moisture content,

ash content and volatile matter

Objective- get acquainted with the methods for determining the main indicators of the technical analysis of coals, master the practical skills of working with the appropriate laboratory equipment and learn in practice the basics of the accelerated method for assessing coals.

Laboratory work is complex. It is based on the definition of three main indicators of coal - humidity, ash content and volatile matter on the basis of which the net calorific value of the working mass of coal is calculated, which is the most important indicator of the quality of coal as an energy fuel.

The calorific value, usually denoted by the symbol, is the amount of thermal energy (hereinafter referred to as heat, or heat) released during the complete oxidation of combustible fuel components with gaseous oxygen. At the same time, it was assumed that higher oxides are formed as a result of oxidation reactions. and sulfur is oxidized to , and fuel nitrogen is released in the form of molecular nitrogen. The heat of combustion is a specific characteristic. For hard and liquid fuels refers to a unit of mass, that is, to 1 kg(specific heat of combustion), and for gaseous fuels - to a unit volume (volumetric heat of combustion) under normal physical conditions, that is, at R = P 0 = 760 mmHg Art. = 1 atm =101325 Pa and
T \u003d T 0 \u003d 273.15 TO (t = t0 = 0°C). Concerning m 3 under these conditions was called normal cubic meter ” and the recommended designation “ nor. m 3". Thus, for gaseous fuels, it is assigned to 1 nor. m 3. Units of measurement accepted in the technical literature: " kJ/kg» (« kJ/norm. m 3") or " MJ/kg» (« MJ/Nor. m 3"). In the old technical literature, the units of measurement were " kcal/kg» (« kcal/nor. m 3"). When translating them into modern units of measurement, it should be remembered that 1 kcal = 4,1868 kJ.

The amount of heat that went to heat the products of complete combustion 1 kg or 1 nor. m 3 fuel, provided that these products contain condensed water vapor, that is, water, is called higher calorific value of fuel . This heat is denoted as .

If during the combustion of fuel water vapor is not condensed, then a smaller amount of released heat will be spent on heating the combustion products by the value of the latent heat of condensation of water vapor (latent heat of water evaporation) . In this case, heat is called lower calorific value of fuel and is denoted as . Thus, the determination does not take into account the heat spent on the evaporation of the moisture of the fuel itself and the moisture formed during the combustion of fuel hydrogen. Accordingly, the value is related to how .

The composition of coal, like any other solid fuels, is expressed as a percentage by weight (wt.%). At the same time, 100% is most often taken as:

composition in the working state of the fuel (composition of its working mass), indicated by the superscript “ r »:

composition in the analytical state (composition of the analytical mass), indicated by the superscript “ a »:

composition in the dry state (dry mass composition), indicated by the superscript “ d »:

composition in a dry ash-free state (composition of dry ash-free mass), indicated by the superscript “ daf »:

where mass fractions in the corresponding mass of coal of carbon, hydrogen, combustible sulfur, oxygen, nitrogen, total and analytical moisture, wt. %; A - ash content of the corresponding mass of coal, wt. %.

To determine the heat of combustion of coals, a single standard method is used - the method of combustion in a calorimetric bomb. With this method, an analytical sample of coal weighing 0.8 ... 1.5 G they are burned in an atmosphere of compressed oxygen in a hermetically sealed metal vessel - a calorimetric bomb, which is immersed in a certain volume of water. By increasing the temperature of this water, the amount of heat released during the combustion of the sample is determined. This gives the calorific value of the fuel for the bomb. Due to the fact that the combustion of fuel occurs in rather specific

Rice. circuit diagram classical calorimeter for determining the calorific value of solid fuels

1 - calorimetric bomb; 2 - stirrer; 3 - thermostat cover; 4 - system for ignition of the sample; 5 - thermometer or a device replacing it; 6 - calorimetric vessel; 7 - thermostat.

conditions (atmosphere of pure oxygen, oxidation of combustible sulfur to SO 3 followed by the formation of nitric acid in condensed moisture, and so on), the value is recalculated to according to the following formula:

where is the heat of formation of sulfuric acid from SO2 and dissolving it in water, numerically equal to 94.4 kJ based on 1% sulfur; - the sulfur content “in the washout of the bomb”, is the amount of sulfur converted into sulfuric acid during combustion, based on the initial coal sample, wt. % (it is allowed to use instead of the total sulfur content in the analytical mass of coal, if , a
); a - coefficient taking into account the heat of formation and dissolution of nitric acid, equal to 0.001 for lean coals and anthracites and 0.0015 for all other fuels.

Knowing , first determine the highest calorific value of the working mass of fuels :

, (2)

where =kJ/kg or kJ / norm.m 3; =
= wt. %.

The coefficient 24.62 in (3) reflects the heat of heating water from
t0 = 0°C to t = 100°C and its evaporation at P 0 = 101325 Pa based on
1 wt. % water.

The value calculated for the operating state of the fuel corresponds to the actual heat released during its combustion in furnaces, and therefore is widely used in heat engineering calculations. is an integral indicator of the quality of fuels and largely determines their consumer properties.

One of the main features of fossil coals is the ability to decompose (destruct) their organic mass when heated without air access. With such heating, gas and vaporous decomposition products are formed, called volatile substances. After the removal of volatile substances from the heating zone, a residue is left, called coke residue, or bead. Since volatile substances are not contained in coals, but are formed when they are heated, one speaks of a "volatilization yield", and not of their content in coals.

The yield of volatile substances is understood as the relative mass of volatile substances, expressed as a percentage, formed during the thermal decomposition of coal under standard conditions. The volatile output is indicated by the symbol V , and non-volatile (coke) residue - NV .

The vapor part of volatile substances consists of condensable hydrocarbons, which are a group of oily and resinous substances, which are the most valuable chemical product.

The gaseous part of volatile substances consists of hydrocarbon gases of the limiting and unsaturated series ( CH 4 , C m H n and so on), carbon monoxide and carbon dioxide ( SO , CO 2 ), hydrogen ( H 2 ) etc.

The composition of the non-volatile residue includes mainly carbon and mineral impurities in the form of ash.

The yield of volatile substances is one of the main classification parameters of fossil coals. Based on the values ​​of the yield of volatiles and the characteristics of the coke residue, the suitability of coals for coking and the behavior of coals in the processes of processing and combustion are evaluated.

The essence of the standard method for determining the yield of volatile substances is to heat a sample of an analytical sample of coal weighing 1 ± 0.1 g without air at t = 900±5 °С within 7 min. The yield of volatile substances is determined by the weight loss of the initial sample, taking into account the moisture content in the fuel.

The yield of volatiles from the analytical sample is calculated by the formula

(4)

where = wt. %; - weight loss of the coal sample after the release of volatile substances, G; - weight of the initial sample of coal, G; - moisture content in the initial sample of the analytical sample of coal, wt. %;

- the yield of non-volatile residue from the analytical sample of the tested coal, %, is calculated by the formula

V laboratory work coals will be used
wt % , therefore, methods for determining quantities and were not considered in the laboratory work.

The yield of volatile substances on a dry ash-free state of coal is determined as follows:

. (6)

Permissible discrepancies between the results of two parallel determinations according to absolute values should not exceed 0.3 wt. % at wt%; 0.5 wt. % at wt. %; 1.0 wt. % at wt. % .

VOLATILE SUBSTANCES (in fossil fuels) - gas and vapor products released during the decomposition of org. substances when heating fossil fuels under standard conditions at t about 850 ° С (GOST 6382 - 65, for anthracites 7303 - 54). Hygroscopic moisture and carbonate carbonic acid are not included in this concept. Increased content. m-fishing, which emit volatile products when heated, introduces a distortion in the output figures of V. l .; solid residue after removal of V. l. called non-volatile residue. With an increase in the degree of coalification, V.'s output of l. falls. Humolites differ in the lowered output of V. l. compared with sapropelites and liptobiolites. Gelified components give a lower yield of V. l. than lipoid components, and higher than fusenized components. Exit V. l. in claren varieties of humic coals, starting from the lower gas coals, it is used as one of the most important indicators of the degree of their coalification.

Geological dictionary: in 2 volumes. - M.: Nedra. Edited by K. N. Paffengolts et al.. 1978 .

See what "Volatile Substances" are in other dictionaries:

See volatile substances. Geological dictionary: in 2 volumes. M.: Nedra. Edited by K. N. Paffengolts et al. 1978. Volatile substances ... Geological Encyclopedia

Gaseous and vaporous substances released from a solid mineral fuel when it is heated without air or with insufficient air supply. The content of L. in. along with the nature of the coke residue is the most important ... ... Technical railway dictionary

volatile substances of the pigment- Substances contained in the pigment that volatilize under certain test conditions. Note Same for filler. [GOST 19487 74] Subjects paintwork materials Generalizing terms additional terms characterizing ... ...

volatile matter of coal- Substances formed during the decomposition of coal under heating conditions without air access. [GOST 17070 87] Topics coals Generalizing terms composition, properties and analysis of coals EN volatile matter … Technical Translator's Handbook

Moisture and hydrocarbons contained in the fuel and released from it during dry distillation in the form of vapors and gases. The amount of L.W. in fuel depends on the type of fuel and varies from 10% (in lean coals and anthracites) to 50% (dry long-flame coals). L. ... ... Marine dictionary

volatiles- — Topics oil and gas industry EN volatile constituents … Technical Translator's Handbook

Volatiles- Substances released from carbon-containing materials (coal, coke, etc.) when heated. The content of volatile substances in coals ranges from 50% (brown coals) to 4% (anthracites). The solid mass remaining after the removal of volatile substances is called ... ... Encyclopedic Dictionary of Metallurgy

VOLATILES- Substances released from carbon-containing materials (coal, coke and others) when heated. The content of volatile substances in coals ranges from 50% (brown coals) to 4% (anthracites). The solid mass remaining after the removal of volatile substances is called ... Metallurgical Dictionary

"LOV" redirects here; see also other meanings. Volatile aromatic substances (VAS) are a group of substances that can cause olfactory sensations. The term is intended to characterize substances used in aromatherapy. In this ... ... Wikipedia

This article should be wikified. Please, format it according to the rules for formatting articles. VOC (volatile organic compounds) volatile organic substances, the Russian equivalent of VOCs). Organi ... Wikipedia

Page 1

The composition of volatile substances formed on the surface of burning solid materials is, as a rule, extremely complex. All those of them that are of interest from the point of view of fire danger are polymeric materials with a high relative molecular weight. Of the two main types of polymers (step polymers and condensation polymers), the first is the simplest, since polymers of this type are formed by directly adding monomer units to the end of a growing polymer chain.

The composition of volatile substances includes valuable substances that are widely used in the national economy.

Combustible gases - carbon monoxide CO, hydrogen H2, various hydrocarbons CnHm and non-combustible gases - nitrogen N2, oxygen O%, carbon dioxide COg, etc., as well as water vapor go into the composition of volatile substances.

The composition of volatile substances includes solvents, thinners, moisture and other compounds contained in the paintwork material and volatilizing during the formation of coatings.

The composition of volatile substances, along with hydrogen and methane, includes resinous products in the form of vapors and tiny drops, which at temperatures below 700 C can cause coke sintering and clogging of chimneys and equipment.

Volatile substances include water vapor, oxygen, nitrogen, volatile sulfur, and various hydrocarbons. At a sufficiently high temperature, combustible components in volatile substances burn with a bright flame, so the composition and amount of volatile substances have a significant effect on the ignition and combustion of fuel, as well as on the volume of the combustion chamber.

The amount and composition of volatile substances in solid fuel determines the participation and importance of dry distillation and coke gasification in the gas generator process, as well as the composition and quality of the resulting generator gas. Therefore, for different fuels and in relation to the requirements for gas engines, set different systems gas generators.

At first glance, it may seem that the composition of volatile substances has a secondary effect on their combustion in a gas mixture, but this point of view does not allow one to understand the features of the fire dynamics. The chemical activity of volatile substances affects the nature of flame stabilization at the surface of a combustible solid material (Sec. The latter affects the amount of heat radiated by the flame into the surrounding space and towards the combustion surface (Sec. Thus, volatile substances containing molecules of aromatic hydrocarbons such as benzene [from carbonaceous residue formed as a result of breaking the branches of the main chain of polyvinyl chloride molecules, equation (РЗ)], or styrene (from polystyrene), give a smoky flame with a high relative emissivity (Sec. Below, it will be shown how these factors affect the burning rate of solid and liquid substances (Sec. In some cases, the composition of volatile substances determines the degree of toxicity of combustion products (cf.

An important advantage is the ability to determine the metabolic products of living cultures, which makes it possible to study the composition of volatile substances during the growth of microflora under anaerobic conditions. Of great importance for performing mass analyzes is also the possibility of using already existing automatic headspace analyzers and special devices described in Chap.

This is due both to the complexity of the composition of such mixtures of harmful substances, the correct analysis of which using gas chromatography alone is simply impossible, and the presence of high-molecular compounds of complex structure (often with several heteroatoms) in the composition of volatile substances of rubber and other elastomers (often with several heteroatoms), the analysis of which by the chromatographic method ami is extremely difficult.

RSK - identification of organic compounds of nitrogen.

Yield of volatile substances

(a. content of volatile agents; n. Gehalt an fluchtigen Bestandteilen; f. teneur en matieres volatiles; and. desprendimiento de substancias volatiles) - an indicator of the quality of solid combustible fuels, which is taken into account when determining their rational prom. use. - gaseous and vaporous products released during heating of fossil fuels under standard conditions (in the CCCP) at t 850±10°C. During coking and semi-coking of fossil coals, in the process of thermal. oil shale processing is captured and used as a valuable chemical. raw materials. Definition of B. l. v. standardized; in the CCCP it is produced in accordance with the conditions stipulated by the state. standards (GOST 6382-75 for fossil coals, GOST 7303-77 for anthracites, GOST 12270-66 for oil shale, GOST 3929-75 for coke).
B. l. in., defined as the ratio of the mass of volatile substances to a unit mass of fuel (in%) and converted to its cyxoe ash-free state V daf characterizes the composition and its organic. substances. For V daf is approx. 70%, oil shale 70-85%, brown humus coal within 60-33%, kam. coal 50-8%, anthracite 9-2%. The value of V daf is used in the CCCP and abroad as one of the main. parameters of classifications of the subdivision of kam. coal for stamps; for the classification of anthracites, volumetric B. l is determined. v. - the volume of decomposition gases per unit mass of anthracite V daf m 3 /kg. To reduce the distorting effect on the value of B. l. v. inorganic impurities in fuel definition B. l. v. produced on samples with ash content A d not higher than 10%; at a higher ash content, the sample material is pretreated. enrichment. K. B. Mironov.

Mountain Encyclopedia. - M.: Soviet Encyclopedia. Edited by E. A. Kozlovsky. 1984-1991 .

See what "Volatile Substances" is in other dictionaries:

Yield of volatile substances- Mass of volatile decomposition products per unit mass solid fuel when it is heated without air access under established standard conditions Source: RD 153 34.0 44.219 00: Solid mineral fuel. Determination of the calorific value of volatile ... ... Dictionary-reference book of terms of normative and technical documentation

volatile matter yield- The amount of gas and vaporous substances released during fuel heating without air access under certain conditions, adjusted for moisture content [A.S. Goldberg. English Russian Energy Dictionary. 2006] Topics energy in general EN… …

volatile matter yield of coal- The mass of volatile substances per unit mass of coal, determined under the conditions established by the standard. [GOST 17070 87] Topics coals Generalizing terms composition, properties and analysis of coals EN yield of volatile matter … Technical Translator's Handbook

volatile content per dry ash-free mass of fuel- - [A.S. Goldberg. English Russian Energy Dictionary. 2006] Topics energy in general EN volatiles on dry ash free basisVdaf … Technical Translator's Handbook

Volatile matter yield of coal- 77. Yield of volatile substances of coal E. Yield of volatile matter

GOST R 55660-2013

NATIONAL STANDARD OF THE RUSSIAN FEDERATION

FUEL SOLID MINERAL

Determination of the yield of volatile substances

solid mineral fuel. Determination of volatile matter

OKS 75.160.10*
OKP 03 2000

_______________
* In IUS 1-2015 GOST R 55660-2013 is given with OKS 75.160.10, 73.040. -
- Database manufacturer's note.

Introduction date 2015-01-01

Foreword

1 PREPARED BY Federal State unitary enterprise"All-Russian Research Center for Standardization, Information and Certification of Raw Materials, Materials and Substances" (FSUE "VNITSSMV") based on its own authentic translation into Russian of the standards specified in paragraph 4

2 INTRODUCED by the Technical Committee for Standardization Russian Federation TC 179 "Solid mineral fuel"

3 APPROVED AND PUT INTO EFFECT by Order of the Federal Agency for Technical Regulation and Metrology dated October 28, 2013 N 1230-st

4 This International Standard is modified from international standards ISO 562:2010* Hard coal and coke - Determination of volatile matter and ISO 5071-1:2013 Brown coals and lignites - Determination of volatile matter ISO 5071-1:2013 "Brown coals and lignites - Determination of the volatile matter in the analysis sample - Part 1: Two furnace method".
________________
* Access to international and foreign documents mentioned hereinafter can be obtained by clicking on the link to the site http://shop.cntd.ru

Additional provisions included in the text of the standard to meet the needs of the national economy are in italics* and set out in the introduction.
________________
* In the paper original, the designations and numbers of standards and normative documents in the "Foreword" section are given in regular type, marked with "**" and the rest of the text of the document is in italics. - Database manufacturer's note.

5 INTRODUCED FOR THE FIRST TIME


The rules for the application of this standard are set out in GOST R 1.0-2012 ** (section 8). Information about changes to this standard is published in the annual (as of January 1 of the current year) information index " National Standards", and the official text of changes and amendments - in the monthly information index "National Standards". In case of revision (replacement) or cancellation of this standard, the corresponding notice will be published in the next issue of the information index "National Standards". Relevant information, notification and texts are also placed v information system general use - on the official website of the Federal Agency for Technical Regulation and Metrology on the Internet (gost.ru)

Introduction

Introduction

The yield of volatile substances is defined as the weight loss of a sample of solid fuel, minus moisture, when heated without air access under standard conditions.

The test results are relative, therefore, in order to achieve reproducibility, it is necessary to maintain the constancy of the main parameters: heating rate, final temperature and heating duration. To reduce the oxidation of the sample of fuel during heating, the access of oxygen to the sample should be limited. This is achieved by using crucibles with ground or ground lids that allow the free removal of volatile substances, but prevent the penetration of oxygen.

The equipment and the test method make it possible to carry out one or more determinations simultaneously in the muffle furnace.

When testing brown coals and lignites, a rapid release of volatile substances is possible, accompanied by the release of solid particles from the crucible, which distorts the result of the determination. To minimize the probability of entrainment of particles from the crucible during the heating process, special methods are provided: briquetting the sample and/or heating in two furnaces.

The yield of volatile substances is one of the classification parameters of hard coals.

When determining the yield of volatile substances, the mass loss due to the decomposition of the organic and mineral masses of coal is taken into account in total. With a significant ash content of coal, the formed products of the destruction of the mineral mass distort the value of the yield of volatile substances, therefore, if the test is carried out to classify coals, their ash content should not exceed 10%. Samples with a higher ash content are pre-enriched.

Based on the values ​​of the yield of volatile substances and the characteristics of the non-volatile residue, it is possible to roughly estimate the caking capacity of coals, as well as the behavior of coals in the processes of technological processing and combustion.

V present standard additional requirements are included in relation to ISO 562 and ISO 5071-1, reflecting the needs of the national economy, namely:

- in the distribution area, the types of solid mineral fuels are specified;

- added section 3 "Terms and definitions";

- the characteristics of the non-volatile residue are given (section 9);

- the method of preparation of samples of coals for the purposes of classification of coals is given (subsection 7.2);

- added methods for briquetting a sample (subsection 7.3) and determining the release of volatile substances from a briquetted sample (p. 8.5.1);

- the method with preliminary drying of the sample in the crucible (ISO 5071-1) is excluded from the text of the standard.

1 area of ​​use

This standard applies to lignites, brown and black coals, anthracites, oil shale, enrichment products, briquettes and coke (hereinafter referred to as fuel) and establishes gravimetric methods for determining the yield of volatile substances.

The general principle for determining the yield of volatile substances is established for all types of solid mineral fuels, and the determination conditions are different for the group of coals (hard coals, anthracites, oil shale, coal briquettes, enrichment products) and cokes and for the group of brown coals (lignites, brown coals, brown coal briquettes, processed products).

NOTE For the lignite group, two alternative methods are recommended to prevent the release of solid particles from the crucible: briquetting the sample and/or heating in two furnaces.

2 Normative references

This standard uses references to the following standards:

GOST R 50342-92 Thermoelectric converters. Are common specifications(IEC 584-2:1982)

GOST R 52917-2008 Solid mineral fuel. Methods for determining moisture in an analytical sample (ISO 11722:1999, ISO 5068-2:2007, MOD)

GOST R 53288-2008* Scales of non-automatic action. Part 1. Metrological and technical requirements. Tests (OIML R 76-1:2006(E), MOD)

________________
*Probably an original error. Should read: GOST R 53228-2008. - Database manufacturer's note.

GOST 1186-87 Stone coals. Method for determining plastometric indicators

GOST 4790-93 Fuel is solid. Definition and presentation of fractional analysis indicators. General specification (ISO 7936:1992, MOD)

GOST 5955-75 Reagents. Benzene. Specifications

GOST 9147-80 Glassware and laboratory porcelain equipment. Specifications

GOST 10742-71 Coals brown, stone, anthracite, combustible shales and coal briquettes. Sampling and Sample Preparation Methods for Laboratory Tests

GOST 11014-2001 Coals brown, stone, anthracite and combustible shales. Accelerated Methods for Moisture Determination

GOST 13455-91 Solid mineral fuel. Methods for the determination of carbon dioxide of carbonates (ISO 925:1997, MOD)

GOST 14198-78 Cyclohexane technical. Specifications

GOST 17070-87 Coals. Terms and Definitions

GOST 23083-78 Coal, pitch and thermoanthracite coke. Methods for sampling and preparing samples for testing

GOST 25336-82 Ware and laboratory glassware. Types, basic parameters and dimensions

GOST 27313-95 Solid mineral fuel. Designation of quality indicators and conversion formulas for analysis results for various fuel conditions (ISO 1170:1997, MOD)

GOST 27589-91 Coke. Method for determining moisture in an analytical sample

Note - When using this standard, it is advisable to check the validity of reference standards in the public information system - on the official website of the Federal Agency for Technical Regulation and Metrology on the Internet or according to the annual information index "National Standards", which was published as of January 1 of the current year, and on issues of the monthly information index "National Standards" for the current year. If a reference standard to which an undated reference is given has been replaced, it is recommended to use current version of this standard, including any changes made to this version. If the reference standard to which the dated reference is given is replaced, then it is recommended to use the version of this standard with the year of approval (acceptance) indicated above. If, after the approval of this standard, a change is made to the referenced standard to which a dated reference is given, affecting the provision to which the reference is given, then this provision is recommended to be applied without taking into account this change. If the reference standard is canceled without replacement, then the provision in which the reference to it is given is recommended to be applied in the part that does not affect this reference.

3 Terms and definitions

This standard uses terms and definitions according to GOST 17070 .

Designation of quality indicators and indices to them - according to GOST 27313 .

4 Essence of methods

A sample of an air-dry sample of solid fuel is heated without air at a temperature of (900±5) °C for 7 minutes. The yield of volatile substances in percent is calculated from the weight loss of the sample sample minus moisture.

When testing the fuel of the coal and coke group (see Section 1), the following determination conditions were established: a sample in the form of a powder and heating in one furnace at (900±5) °C for 7 min.

When testing the fuel of the lignite group (see section 1), the following alternative determination conditions are established:

a) powder sample and subsequent heating in two ovens: at (400 ± 10) °C for 7 minutes and at (900 ± 5) °C for 7 minutes.

b) briquetted sample and heating in one oven at (900±5) °С for 7 min.

If, when testing a sample under conditions a) and b), it is not possible to avoid the release of solid particles, then it is recommended to determine the yield of volatile substances under the following conditions: briquetting a sample and sequential heating in two furnaces: at (400 ± 10) ° C for 7 min and at (900±5) °С for 7 min.

5 Reagents

5.1 Cyclohexane on GOST 14198.

5.2 Benzene by GOST 5955 .

6 Equipment

6.1 Muffle furnace

A muffle furnace with electric heating and a temperature controller is used to ensure a constant temperature (900 ± 5) °С in the working zone of the furnace. For testing fuels belonging to the group of brown coals, a second muffle furnace of a similar design is additionally used, in the working zone of which a constant temperature (400 ± 10) °C is maintained.

Structurally, the muffle furnace can be with a closed back wall or have a drain tube with a diameter of 25 mm and a length of 150 mm on the back wall (Figure 1).

Dimensions in mm

1 - heating system; 2 - zone of constant temperature; 3 - control (not sheathed) thermocouple; 4 - chamber of the muffle furnace (width 200 mm); 5 - throttle valve; 6 - outlet tube; 7 - sheathed thermocouple

Figure 1 - Muffle furnace (example)

NOTE In muffle furnaces, the front door must be tightly closed. The outlet tube protrudes slightly above the furnace and must be fitted with a throttle valve to restrict the flow of air through the muffle furnace.


The thermal power of the muffle furnace must be such that the initial temperature of 900 °C or 400 °C is restored after the introduction of a cold support with crucibles into the furnace in no more than 4 minutes. The temperature is measured using a thermocouple (6.2).

In a conventionally designed muffle furnace (Figure 1), a series of determinations can be carried out simultaneously using a stand for several crucibles.

In this case, the constant temperature zone must be at least 160x100 mm. For a single determination in one crucible on an individual stand, the diameter of the constant temperature zone is 40 mm.

The temperature of 900 °C in the furnace should be maintained as precisely as possible. The permissible deviation of ±5 °C includes possible temperature measurement errors and uneven distribution of temperature.

6.2 Thermocouple

Thermoelectric converter for temperature measurement up to 1000 °C GOST R 50342 with measuring device.

The temperature in the furnace is measured using an uncovered thermocouple (control) made of wire no more than 1 mm thick. The length of the thermocouple should be sufficient so that the junction of the thermocouple inserted into the muffle furnace through the front or rear wall is in the middle between the bottom of the crucible placed on the stand and the bottom of the furnace. If a rack with several crucibles is used, the temperature is checked under each crucible. It is allowed to check the temperature above the crucibles at the same level in the working area of ​​the furnace.

If necessary, a sheathed thermocouple may be permanently present in the furnace, with its junction placed as close as possible to the center of the constant temperature zone. The readings of a sheathed thermocouple must be checked at short intervals against the readings of an unsheathed thermocouple, which is brought into the furnace for this. A sheathed thermocouple is usually integral part temperature meter-regulator used in the muffle furnace.

NOTE The temperature/electromotive force relationship of the thermocouple junction used for measurement high temperatures, gradually changes over time.

6.3 Crucible with lid

A cylindrical crucible with a well-fitting lid is made of fused silica glass. The mass of the crucible with the lid is from 10 to 14 g, the dimensions are shown in Figure 2. The lid should fit snugly against the crucible, the horizontal gap between the lid and the crucible should not exceed 0.5 mm. The selected cover is ground to the crucible, making the contact surfaces smooth.

Dimensions in mm

Figure 2 - Quartz crucible with lid

NOTE For testing highly intumescent coals, taller crucibles must be used. Increasing the height of the crucible to 45 mm does not affect the result of the determination, if the rate of temperature recovery in the furnace is maintained.


It is allowed to use porcelain crucibles No. 3 high form with lids GOST 9147 . The lids must be fitted and carefully lapped, and the lapping of the lids to the porcelain crucibles is carried out by mechanical rotation until a groove is formed on the inner surface of the lid.

Crucibles with a matched and ground-in lid should be identically marked, calcined at a temperature of (900 ± 5) ° C to constant weight and placed in a desiccator with a drying agent.

6.4 Crucible support

The stand, on which the crucibles are placed in the muffle furnace, makes it possible to observe the set heating rate.

The following supports are allowed:

a) for a single determination - a ring of heat-resistant steel wire(Figure 3, a) with a ceramic disk 25 mm in diameter and 2 mm thick, placed on the inner ledges of the supports;

b) for carrying out several determinations simultaneously (two, four or six):

1) a frame made of heat-resistant steel wire with ceramic plates 2 mm thick, on which crucibles are placed (Figure 3, b);

2) a stand made of sheet heat-resistant steel, usually for six crucibles (if the dimensions of the working area allow) (Figure 4).

Dimensions in mm

a) for a single definition

b) for multiple definitions

1 - three supports located in relation to each other at 120 °; 2 - ring; 3 - frame; 4 - ceramic plates

Figure 3 - Supports for crucibles

Dimensions in mm

Figure 4 - Stand for six crucibles

6.5 Scales

Scales laboratory on GOST R 53228 with a margin of error of ±0.1 mg.

6.6 Press

Manual laboratory press with a matrix diameter of not more than 15 mm.

6.7 Desiccator

Use a desiccator on GOST 25336 with drying agent.

7 Sample preparation

7.1 The fuel sample for determining the volatile matter yield is an analytical sample taken and prepared in accordance with GOST 10742 or GOST 23083.

An analytical sample, ground to a maximum particle size of 212 µm, must be air-dry, for which it is laid out in a thin layer and kept in air at room temperature for the minimum time necessary to achieve equilibrium between the moisture content of the fuel and the laboratory atmosphere.

Before sampling, the sample is thoroughly mixed for at least 1 min, preferably mechanically.

Simultaneously with taking a sample for analysis, samples are taken to determine the content of analytical moisture in accordance with GOST R 52917 , GOST 11014 or GOST 27589 .

7.2 If the determination of the yield of volatile substances in hard coals and anthracites is carried out for the purpose of classification, their ash content should be no more than 10%. If the ash content of the sample exceeds 10%, the sample is enriched in organic or inorganic liquids in accordance with GOST 1186 and GOST 4790 .

Hard coals are enriched in liquids with a density of 1500 to 1600 kg/m, and anthracites - in liquids with a density of 1800 kg / m(zinc chloride). If, after enrichment of samples of hard coals and anthracites, their ash content exceeds 10%, the determination of the yield of volatile substances of the surfaced fraction is carried out at the actual ash content.

7.3 Briquetting of brown coal

An air-dry sample of brown coal, prepared according to 7.1, weighing (1 ± 0.1) g, is placed in a laboratory press matrix (6.6), covered with an insert on top, and then the punch is lowered by rotating the press screw or turning the handle and compressing the coal until a briquette is formed . The resulting briquette is removed from the press and stored in a weighing bottle until the start of the test.

8 Testing

8.1 Temperature control in muffle furnaces

In muffle furnaces, with the help of permanently installed sheathed thermocouples, the operating temperatures are set to (400 ± 10) ° C and (900 ± 5) ° C. The temperatures in the furnaces are controlled with the help of uncovered thermocouples.

Stands filled with empty crucibles with lids are placed in the working areas of muffle furnaces. Check the temperature under each crucible at the same height using an uncovered thermocouple. The measured temperatures must be within the tolerances of the working area temperature. When carrying out all procedures during the test, adhere to the selected position of the stand with crucibles in the working area of ​​​​the furnace.

It is allowed to place the junction of an uncovered thermocouple at the same height above the crucibles within the stable heating zone.

The temperature in the oven is checked before the start of the determinations. With routine daily work, it is enough to carry out such control monthly.

Checking the rate of temperature recovery in the furnace is carried out in a similar way.

8.2 Preparation for testing

Empty crucibles are closed with lids (6.3), placed on a stand (6.4), filling all the nests, and placed in the stable temperature zone of a muffle furnace heated to (900 ± 5) °C. The crucibles are kept in a closed oven for 7 minutes.

Remove the crucibles from the furnace, cool on a metal plate for 5 min without removing the lids, after which the crucibles are placed in a desiccator (6.7) and cooled to room temperature near the balance.

After cooling, the empty crucibles with lids are weighed.

The procedure for igniting empty crucibles before each use for testing is optional. A sufficient condition for obtaining test results within the allowed discrepancies is the storage of pre-calcined crucibles in a desiccator with a drying agent and the clarification of the mass of the crucible immediately before placing a sample in it.

A weighed portion of the sample, prepared in accordance with Section 7, weighing (1 ± 0.01) g is placed in a weighed crucible. Close the crucible with a lid and weigh. All weighings are carried out with a margin of error of ±0.1 mg.

The sample in the form of a powder is distributed over the bottom of the crucible in an even layer, lightly tapping the crucible on a clean, hard surface.

When testing coke, remove the lid from the crucible, add 2-4 drops of cyclohexane (5.1) to the sample and close the crucible again with a lid. Benzene (5.2) may be used instead of cyclohexane.

Note - Addition of cyclohexane or benzene prevents coke oxidation.

8.3 Determination of the release of volatile substances in coals and cokes

The temperature in the muffle furnace is set to (900 ± 5) °C.

Crucibles weighed in the form of a powder, closed with lids, are placed in the nests of a cold stand. If empty nests remain on the stand, empty crucibles with lids are placed in them. The support with the crucibles is transferred to the muffle furnace, the furnace door is closed and left for 7 min ± 5 s.

The temperature that dropped when the crucibles were placed in the furnace should again reach (900 ± 5) °C in no more than 4 minutes. Otherwise, the test is repeated.

8.4 Determination of volatile matter in brown coal (alternative methods)

8.4.1 Determination from weighed powder in two ovens

In one muffle furnace, the temperature is set to (400 ± 10) ° C, and in the other - (900 ± 5) ° C.

Crucibles weighed in the form of a powder are covered with lids and placed in the nests of a cold stand. If empty nests remain on the stand, empty crucibles with lids are placed in them. The support with crucibles is transferred to a muffle furnace heated to (400 ± 10) °C, the furnace door is closed and left for 7 min ± 5 s. The stand is removed and immediately placed in a muffle furnace heated to (900 ± 5) °C, the furnace door is closed and left for another 7 min ± 5 s.

The temperature, which decreases when the crucibles are placed in the furnace, should again reach (400 ± 10) °С and (900 ± 5) °С in no more than 4 minutes. Otherwise, the test is repeated.

Remove the crucible rack from the oven and cool on a metal plate for 5 minutes. After that, the crucibles, closed with lids, are transferred to a desiccator and cooled to room temperature near the balance.

Crucibles with non-volatile residue are weighed.

After the test, non-volatile residues are removed from the crucibles. Open crucibles and lids are calcined in a muffle furnace at a temperature of (900 ± 5) ° C, cooled, freed from ash residue and stored in a desiccator with a drying agent.

8.4.2 Determination from a briquette sample in one oven

The temperature in the muffle furnace is set to (900 ± 5) °C.

The weighed crucibles are filled with briquettes prepared according to 7.3. The crucibles are covered with lids and weighed. Closed crucibles with briquettes are placed in the nests of the cold stand, leaving no empty nests. Further determination is carried out according to 8.3.

Notes

1 When testing some brown coals, lignites and products of their processing it is not possible to avoid the emission of solid particles from the crucible either when using the method of heating a sample in the form of a powder in two furnaces, nor when using the heating method briquetted sample in one oven. In such cases, an air-dry fuel sample is briquetted according to 7.3 and then determine the yield of volatile substances by heating in two furnaces.

2 The yield of volatile substances is determined in parallel in two sample portions. It is not recommended to test weighed portions of the same sample on the same stand.

9 Non-volatile residue characterization

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* The name of section 9 in the paper original is in italics. - Database manufacturer's note.

Non-volatile residues obtained after determining the yield of volatile substances of coals are characterized depending on appearance and strength as follows:

- powdery;

- stuck together - with light pressure with a finger, crumbles into powder;

- weakly baked - with light pressure with a finger, it breaks into separate pieces;

- sintered, not fused - for splitting into separate pieces, it is necessary to apply force;

- fused, not swollen - a flat cake with a silvery metallic sheen of the surface;

- fused, swollen - swollen non-volatile residue with a silvery metallic sheen of the surface less than 15 mm high;

- fused, strongly swollen - swollen non-volatile residue with a silvery metallic sheen of the surface with a height of more than 15 mm.

10 Processing results

The yield of volatile substances from the analytical sample of the test fuel, expressed as a percentage, is calculated by the formula:

where is the mass of an empty crucible with a lid, g;

The mass of the crucible with a lid and a sample sample before testing, g;

- mass of the crucible with a lid and non-volatile residue after the test, g;

- mass fraction of moisture in the analytical sample, %, determined by. (3)

If the mass fraction of carbon dioxide from carbonates in the fuel sample is more than 2%, the volatile matter yield corrected for carbon dioxide from carbonates , expressed as a percentage, is calculated by the formula

, (4)

where - mass fraction of carbon dioxide from carbonates in the analytical sample, determined by GOST 13455 , %;

- mass fraction of carbon dioxide from carbonates in the non-volatile residue, determined by GOST 13455 , %.

The test results are calculated to the second decimal place, and the final result, which is the arithmetic mean of the results of two replicate tests, is rounded to the first decimal place.

Recalculation of test results for other fuel states other than air-dry is carried out in accordance with GOST 27313.

11 Precision

The precision of the method is characterized by the repeatability and reproducibility of the results obtained.

11.1 Repeatability

The results of two parallel determinations carried out within a short period of time, but not simultaneously, in the same laboratory by the same performer using the same equipment on representative portions taken from the same analytical sample, should not differ from each other more than the value of the repeatability limit given in Table 1.


Table 1 - Limits of repeatability and reproducibility of the results of determining the yield of volatile substances

Name of coal	The maximum allowable difference between the results (calculated for the same mass fraction moisture)
	Repeatability limit	Reproducibility limit
A group of hard coals* with a volatile matter yield of less than 10%	0.3% absolute	0.5% absolute
A group of hard coals* with a volatile matter yield of 10% or more	3% of the average result	the greater of the two: 0.5% absolute or 4% of the mean
	0.2% absolute	0.3% absolute
Group of brown coals*	1.0% absolute	3.0% absolute
* See section 1.

11.2 Reproducibility

The results, each of which is the arithmetic mean of the results of two parallel determinations carried out in two different laboratories on representative portions taken from the same sample after the last stage of its preparation, should not differ from each other by more than the value of the reproducibility limit, shown in table 1.

If the discrepancy between the results of the two determinations is greater than the repeatability limit given in Table 1, a third determination is made. The test result is taken as the arithmetic mean of the results of two determinations that are within the tolerance limits.

If the result of the third determination is within the tolerance for each of the two previous results, the test result is taken as the arithmetic mean of the results of the three determinations.

12 Test report

The test report must contain the following information:

- identification of the test sample;

- a reference to this standard;

- date of testing;

- test results indicating which fuel state they refer to;

- mass fraction of moisture and ash content of an air-dry sample, if the results are presented for the analytical state of the fuel;

- features observed during the test.

UDC 622.33:543.813:006.354 OKS 75.160.10 OKP 03 2000

Key words: solid mineral fuel, coal, brown coal, anthracite, oil shale, coke, determination method, volatile matter

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Electronic text of the document
prepared by CJSC "Kodeks" and checked against:
official publication
M.: Standartinform, 2014