GOST R 55660-2013

NATIONAL STANDARD OF THE RUSSIAN FEDERATION

SOLID MINERAL FUEL

Solid mineral fuel. Determination of volatile matter

OKS 75.160.10*
OKP 03 2000

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

Date of introduction 2015-01-01

Preface

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 TK 179 "Solid mineral fuels"

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

4 This standard is modified from the international standards ISO 562:2010* “Hard coal and coke - Determination of volatile matter” and ISO 5071-1:2013 "Brown coals and lignites - Determination of the volatile matter in the analysis sample - Part 1: Two furnace method" (ISO 5071-1:2013 "Brown coals and lignites - Determination of the volatile matter in the analysis sample - Part 1: Two furnace method").
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* Access to international and foreign documents mentioned here and further in the text can be obtained by following the link to the website http://shop.cntd.ru

Additional provisions included in the text of the standard to address needs national economy, italicized* and stated in the introduction
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* In the original paper, the designations and numbers of standards and normative documents in the “Foreword” section are given in regular font, marked with a “**” and the rest of the document text is in italics. - Database manufacturer's note.

5 INTRODUCED FOR THE FIRST TIME

The rules for the application of this standard are established 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 is published 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, notices and texts are also posted in information system common use- on the official site Federal agency on technical regulation and metrology on the Internet (gost.ru)

Introduction

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

Test results are relative, therefore, to achieve reproducibility, it is necessary to maintain the consistency of the main parameters: heating rate, final temperature and heating duration. To reduce the oxidation of a sample of fuel during heating, the access of oxygen to the sample should be limited. This is achieved by using crucibles with ground or lapped lids, allowing the free removal of volatile substances, but preventing the penetration of oxygen.

The equipment and test method allow one or more determinations to be carried out simultaneously in a muffle furnace.

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

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

When determining the yield of volatile substances, mass losses due to the decomposition of organic and mineral masses of coal are taken into account. When the ash content of coal is significant, the resulting destruction products of the mineral mass distort the yield of volatile substances, therefore, if the test is carried out for the purpose of classifying coals, their ash content should not exceed 10%. Samples with 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 ability of coals, as well as the behavior of coals in the processes of technological processing and combustion.

This standard includes additional requirements in relation to ISO 562 and ISO 5071-1, reflecting the needs of the national economy, namely:

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

- added section 3 "Terms and definitions";

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

- the procedure for preparing coal samples for the purposes of coal classification is given (subsection 7.2);

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

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

1 area of use

This standard applies to lignites, brown and hard coals, anthracite, oil shale, enrichment products, briquettes and cokes (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 hard coals (hard coals, anthracites, oil shale, coal briquettes, enrichment products) and cokes and for the group of brown coals (lignites, brown coals, lignite briquettes, processed products).

Note - For the group of brown coals, two alternative methods are recommended to prevent the release of solid particles from the crucible: briquetting a sample and/or heating in two furnaces.

2 Normative references

This standard uses references to the following standards:

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

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

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

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

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

GOST 4790-93 Solid fuel. Definition and presentation of fractional analysis indicators. General specifications (ISO 7936:1992, MOD)

GOST 5955-75 Reagents. Benzene. Specifications

GOST 9147-80 Porcelain laboratory utensils and equipment. Specifications

GOST 10742-71 Brown coals, hard coals, anthracite, oil shale and coal briquettes. Methods of sampling and preparation of samples for laboratory tests

GOST 11014-2001 Brown coals, hard coals, anthracite and oil shale. Accelerated methods for moisture determination

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

GOST 14198-78 Technical cyclohexane. Specifications

GOST 17070-87 Coals. Terms and Definitions

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

GOST 25336-82 Laboratory glassware and equipment. Types, main parameters and sizes

GOST 27313-95 Solid mineral fuel. Designation of quality indicators and formulas for recalculating analysis results for various fuel states (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 the reference standards in the public information system - on the official website of the Federal Agency for Technical Regulation and Metrology on the Internet or using 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 is replaced, it is recommended that the current version of that standard be used, taking into account all changes made to it. this version changes. If a dated reference standard is replaced, it is recommended to use the version of that standard with the year of approval (adoption) indicated above. If, after the approval of this standard, a change is made to the referenced standard to which a dated reference is made that affects the provision referred to, it is recommended that that provision be applied without regard to that change. If the reference standard is canceled without replacement, then the provision in which a 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 for them - according to GOST 27313 .

4 Essence of methods

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

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

When testing fuel from the brown coal group (see Section 1), the following alternative determination conditions are established:

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

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

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 the sample and sequential heating in two furnaces: at (400±10) °C for 7 minutes and at (900±5) °C for 7 minutes.

5 Reagents

5.1 Cyclohexane By GOST 14198.

5.2 Benzene GOST 5955 .

6 Equipment

6.1 Muffle furnace

A muffle furnace with electric heating and a thermostat is used, ensuring a constant temperature (900±5) °C in the working area of the furnace. To test fuels belonging to the group of brown coals, a second muffle furnace of a similar design is additionally used, in the working area of which a constant temperature (400±10) °C is maintained.

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

Dimensions in millimeters

1 - heating system; 2 - constant temperature zone; 3 - control (not sheathed) thermocouple; 4 - muffle furnace chamber (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 exhaust pipe protrudes slightly above the furnace and should be equipped with a throttling valve to limit the air flow through the muffle furnace.

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

In a muffle furnace of a conventional design (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 zone with a constant temperature is 40 mm.

The oven temperature of 900°C should be maintained as accurately as possible. Permissible deviation ±5 °C includes possible mistakes temperature measurements and unevenness of its distribution.

6.2 Thermocouple

Thermoelectric converter for measuring temperatures up to 1000 °C according to GOST R 50342 with a 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 must be sufficient so that the junction of the thermocouple inserted into the muffle furnace through the front or rear wall is located midway between the bottom of the crucible placed on the stand and the bottom of the furnace. If a rack with multiple crucibles is used, the temperature is checked under each crucible. It is permissible to check the temperature above the crucibles at the same level in the working area of the furnace.

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

NOTE The temperature/electromotive force ratio of a thermocouple junction used to measure high temperatures changes gradually over time.

6.3 Crucible with lid

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

Dimensions in millimeters

Figure 2 - Quartz crucible with lid

Note - To test highly intumescent coals, it is necessary to use taller crucibles. Increasing the crucible height to 45 mm does not affect the determination result if the rate of temperature recovery in the furnace is maintained.

It is allowed to use porcelain crucibles No. 3 high shape with lids GOST 9147 . The lids must be adjusted and carefully ground in, and the grinding 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 selected and ground-in lid must 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 stand

The stand on which the crucibles are placed in the muffle furnace allows the set heating rate to be maintained.

The following stands can be used:

a) for a single determination - a ring made of heat-resistant steel wire (Figure 3, a) with a ceramic disk with a diameter of 25 mm and a thickness of 2 mm, placed on the internal protrusions of the supports;

b) to carry 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 heat-resistant steel sheet, usually for six crucibles (if the dimensions of the working area allow) (Figure 4).

Dimensions in millimeters

a) for a single definition

b) for several definitions

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

Figure 3 - Stands for crucibles

Dimensions in millimeters

Figure 4 - Stand for six crucibles

6.5 Libra

Laboratory scales By GOST R 53228 with a permissible error limit of ±0.1 mg.

6.6 Press

Manual laboratory press with a matrix diameter of no more than 15 mm.

6.7 Desiccator

Use a desiccator By GOST 25336 with drying agent.

7 Sample preparation

7.1 The fuel sample to determine the yield of volatile substances is an analytical sample selected and prepared in accordance with GOST 10742 or GOST 23083.

The analytical sample, crushed to a maximum particle size of 212 microns, must be in an air-dry state, 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 humidity of the fuel and the laboratory atmosphere.

Before taking a sample, the sample is thoroughly mixed for at least 1 minute, preferably mechanically.

Simultaneously with taking a sample for analysis, samples are taken to determine the analytical moisture content 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 floating fraction is carried out at the actual ash content.

7.3 Briquetting of brown coal

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

8 Carrying out the test

8.1 Temperature control in muffle furnaces

In muffle furnaces, using permanently installed sheathed thermocouples, operating temperatures are set at (400±10) °C and (900±5) °C. Temperatures in furnaces are controlled using 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 temperature values must be within the permissible deviations from the temperature of the working area. When carrying out all procedures during testing, 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 unsheathed thermocouple at the same height above the crucibles within the stable heating zone.

The temperature in the oven is checked before the determination begins. With routine daily work It is enough to carry out such monitoring monthly.

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

8.2 Preparation for testing

Empty crucibles are covered with lids (6.3), placed on a stand (6.4), filling all slots, and placed in a 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 stand with crucibles from the oven, cool on a metal plate for 5 minutes 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, empty crucibles with lids are weighed.

The procedure for calcining empty crucibles before each use for testing is not mandatory. Sufficient condition To obtain test results within the limits of permissible discrepancies, it is necessary to store pre-heated crucibles in a desiccator with a drying agent and clarify the mass of the crucible immediately before placing the sample into it.

Place a sample weighing (1±0.01) g, prepared in accordance with Section 7, into a weighed crucible. Close the crucible with a lid and weigh. All weighings are carried out with a permissible error limit of ±0.1 mg.

The sample in the form of 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 with the lid again. It is permissible to use benzene (5.2) instead of cyclohexane.

Note - Addition of cyclohexane or benzene prevents coke oxidation.

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

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

Crucibles with powder samples, closed with lids, are placed in the sockets of a cold stand. If there are empty slots on the stand, empty crucibles with lids are placed in them. The stand with crucibles is transferred to the muffle furnace, the furnace door is closed and left for 7 minutes ± 5 s.

The temperature, which dropped when the crucibles were installed 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 yield in brown coals (alternative methods)

8.4.1 Determination from a powder sample in two ovens

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

Crucibles with samples in the form of powder are covered with lids and placed in the sockets of a cold stand. If there are empty slots on the stand, empty crucibles with lids are placed in them. The stand with crucibles is transferred to a muffle furnace heated to (400 ± 10) °C, the furnace door is closed and left for 7 minutes ± 5 s. Remove the stand and immediately place it in a muffle furnace heated to (900 ± 5) °C, close the furnace door and leave for the next 7 minutes ± 5 s.

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

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

The crucibles containing the non-volatile residue are weighed.

After testing, 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 briquetted sample in one oven

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

Briquetted samples prepared according to 7.3 are placed in weighed crucibles. 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. Next, the determination is carried out according to 8.3.

Notes

1 When testing some brown coals, lignites and their processed products 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 powder in two furnaces, neither when using the heating method briquetted sample in one oven. In such cases, the 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 portions of the sample. It is not recommended to test portions of the same sample on the same stand.

9 Characteristics of non-volatile residue

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* The name of section 9 in the original paper 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;

- sticky - when lightly pressed with a finger, it crumbles into powder;

- weakly baked - when lightly pressed with a finger, it splits into separate pieces;

- sintered, not fused - force must be applied to split into separate pieces;

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

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

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

10 Processing of results

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

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

Mass of the crucible with lid and sample before testing, g;

- mass of the crucible with a lid and non-volatile residue after testing, 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 yield corrected for carbon dioxide from carbonates , expressed as a percentage, is calculated using 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 parallel tests, is rounded to the first decimal place.

Recalculation of test results for other states of fuel other than air-dry is carried out according to 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 person using the same equipment on representative portions taken from the same analytical sample, should not differ from each other more than the repeatability limit value given in Table 1.

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


Name of coal	Maximum permissible discrepancy between results (calculated for the same mass fraction of moisture)
	Repeatability limit	Reproducibility limit
Group of hard coals* with volatile matter release less than 10%	0.3% absolute	0.5% absolute
Group of hard coals* with a volatile matter release of 10% or more	3% of average result	the greater of the two: 0.5% absolute or 4% of the average result
	0.2% absolute	0.3% absolute
Brown coal group*	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. given in table 1.

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

If the result of the third determination is within the acceptable discrepancies in relation to each of the two previous results, the arithmetic mean of the results of the three determinations is taken as the test result.

12 Test report

The test report must contain the following information:

- identification of the test sample;

- reference to this standard;

- test date;

- test results indicating which fuel condition they relate to;

- mass fraction of moisture and ash content of the 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, hard coal, brown coal, anthracite, oil shale, coke, determination method, yield of volatile substances

_____________________________________________________________________

Electronic document text
prepared by Kodeks JSC and verified against:
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M.: Standartinform, 2014

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 °C (GOST 6382 - 65, for anthracite 7303 - 54). Hygroscopic moisture and carbonate carbon dioxide are not included in this concept. Increased content minerals that release volatile products when heated introduce distortion into the VL yield figures; solid residue after removal of V. l. called non-volatile residue. With an increase in the degree of carbonization, the yield of V. l. falls. Humolites differ in reduced yield of V. l. compared with sapropelites And liptobiolites. Gelified components give a lower yield of VL than lipoid components, and higher than fusainized components. Exit V. l. in Claren varieties of humus coals, starting with lower gas ones, it is used as one of the most important indicators of the degree of their carbonification.

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

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Laboratory work No. 3

Determination of the heat of combustion of coals based on their moisture content,

ash content and volatile matter yield

Goal of the work- become familiar with the methods for determining key indicators technical analysis coals, acquire practical skills in operating appropriate laboratory equipment and learn in practice the basics of the accelerated coal assessment method.

Laboratory work is complex. It is based on the determination of three main indicators of coal - moisture, ash content and the release of volatile substances on the basis of which the lower calorific value is calculated working mass coal, which is the most important indicator of the quality of coal as an energy fuel.

The heat of combustion, usually denoted by the symbol, is the amount of thermal energy (hereinafter referred to as heat, or heat) released when the combustible components of the fuel are completely oxidized by oxygen gas. In this case, it is accepted that higher oxides are formed as a result of oxidation reactions And sulfur oxidizes only to , and fuel nitrogen is released in the form of molecular nitrogen. Heat of combustion is a specific characteristic. In hard and liquid fuels referred to a unit of mass, that is, 1 kg (specific heat combustion), and for gaseous fuels - to a unit volume (volumetric heat of combustion) at normal physical conditions, that is, when R = P 0 = 760 mmHg Art. = 1 atm =101325 Pa And
T = T 0 = 273.15 TO (t = t 0 = 0°C). Due to this m 3 under these conditions it received the name “ normal cubic meter " and recommended designation " no. m 3" Thus, gaseous fuels are classified as 1 no. m 3. Units of measurement accepted in technical literature: “ kJ/kg» (« kJ/no. m 3") or " MJ/kg» (« MJ/no. m 3"). In the old technical literature, the units of measurement were " kcal/kg» (« kcal/no. m 3"). When converting them into modern units of measurement, it should be remembered that 1 kcal = 4,1868 kJ.

The amount of heat that went into heating the products of complete combustion 1 kg or 1 no. 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 fuel combustion water vapor is not condensed, then a smaller amount of released heat will be consumed to heat the combustion products by the amount of the latent heat of condensation of water vapor (latent heat of evaporation of water) . In this case, heat was called lower heating value of fuel and is denoted as . Thus, the determination does not take into account the heat spent on evaporating the moisture of the fuel itself and the moisture formed during the combustion of hydrogen in the fuel. Accordingly, the value is related to how .

The composition of coal, like any other solid fuel, is expressed as a percentage by weight (wt.%). In this case, the following are most often taken as 100%:

· composition of the fuel in working condition (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 »:

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

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

where the mass fractions in the corresponding mass of coal are 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, a weighed portion of an analytical coal sample weighing 0.8...1.5 G 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 combustion of the sample is determined. This gives the fuel combustion heat for the bomb due to the fact that fuel combustion occurs in quite specific

Rice. Schematic diagram of a classic calorimeter for determining the heat of combustion of solid fuels

1 – calorimetric bomb; 2 – stirrer; 3 – thermostat cover; 4 – system for igniting the hitch; 5 – thermometer or a device replacing it; 6 – calorimetric vessel; 7 – thermostat.

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

where is the heat of formation of sulfuric acid from SO 2 and dissolving it in water, numerically equal to 94.4 kJ based on 1% sulfur; - sulfur content “in the bomb wash” is the amount of sulfur converted into sulfuric acid during combustion, based on the initial sample of coal, wt. % (may be used 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 higher calorific value of the working mass of fuels:

, (2)

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

Coefficient 24.62 in (3) reflects the heat of heating water from
t 0 = 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 thermal engineering calculations. is an integral indicator of fuel quality 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 vapor decomposition products called volatiles are formed. After removing volatile substances from the heating zone, a residue remains called coke residue, or coke residue. Since volatile substances are not contained in coals, but are formed when they are heated, they speak of the “yield of volatile substances”, and not about 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 release of volatiles is indicated by the symbol V , and the non-volatile (coke) residue is N.V. .

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

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

The composition of the non-volatile residue consists mainly of 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 volatile yield values and the characteristics of the coke residue, the suitability of coals for coking and the behavior of coals in processing and combustion processes are assessed.

Essence standard method determining the yield of volatile substances consists of heating a weighed portion of an analytical sample of coal weighing 1±0.1 g without access to air at t = 900±5 °C within 7 min. The yield of volatile substances is determined by the loss of mass of the initial sample, taking into account the moisture content in the fuel.

The release of volatiles from an analytical sample is calculated using the formula

(4)

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

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

In laboratory work, coals with
wt % , therefore, methods for determining quantities and not considered in laboratory work.

The yield of volatile substances in the dry, ash-free state of coal is determined as follows:

. (6)

Permissible differences 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. % .

Release of volatile substances and characteristics of coke residue

When solid fuel is heated to high temperatures without air access, hydrocarbons decompose with the formation of gaseous products (CO, H 2, CH 4, CO 2, etc.), which are called "volatiles". The release of volatile substances from solid fuel occurs in the temperature range 100...1100 °C. After removal of volatile substances, a solid remains coke residue.

Release of volatile substances is one of the important parameters of hard coals and anthracites. Volatile yield and characteristics coke residue determine the suitability of coals for coking, as well as methods of fuel combustion.

The yield of volatile substances increases with increasing temperature and depends on the rate of heating of coal particles. The bulk of volatile substances are formed when coal is heated to 800...850 °C. The release of volatiles ends after 6...7 minutes of heating at 850 °C.

Essence standard method Determining the yield of volatile substances consists of heating a 1 g portion of an analytical fuel sample without access to air at t= (850±10) °C for 7 minutes. The yield of volatile substances is determined depending on the mass loss of the initial sample, taking into account the moisture content in the fuel.

Caking coals serve as raw materials for obtaining coke, which is used as a reducing agent in the blast furnace process when smelting iron from ore. Such coals are more valuable than non-caking coals, which are used as fuel.

Coal sintering can be divided into two stages:

Softening of coal particles;

Formation of a solid residue from plastic mass.

Caking coals transform into a plastic state at temperatures above 300 °C. At a temperature of 500...550 °C, the plastic mass hardens and a sintered solid residue is formed - char. When the temperature rises to 1000 °C, the strength of the residue increases and coke.

The determination of plastometric indicators is carried out in a special plastometric apparatus. The test conditions are similar to the conditions for coking coal in industry. The coal is under load and heated from one side, from the bottom of the glass. In this case, at different distances from the heating surface, the coal will be at different stages of transformation into coke. The layer closest to the heating surface will be coke and semi-coke, then layer plastic coal mass(plastic layer), and above the plastic mass is coal, which has not yet passed into the plastic state. These layers are located parallel to the heating surface. As the temperature rises, the char layer increases, and the coal becomes plastic. The longer the coal remains in a plastic state, the thicker the plastic layer becomes.

Using the plastometric method, the thickness of the plastic layer is determined at– this is the maximum distance between the interfaces “coal - plastic mass” and “plastic mass – semi-coke” (Fig. 1.5).

Figure 1.5 - Plastometric test schedule

To carry out the tests, a sample of coal (100±1) g with a particle size of less than 1.6 mm is placed in a plastometric cup. A stamp with a lever is placed on top of the coal, on which a weight is suspended, providing a pressure of 0.1 MPa. Heating is carried out in such a way that 30 minutes after the start of the experiment, the temperature on the surface of the bottom of the glass reaches 250 °C. Then, up to 730 °C, heating is carried out at a rate of 3 °C per minute (8 hours). Starting from 350 °C, the upper and lower levels of the plastic layer are measured at certain intervals.