Technical analysis of coal. Method for determining volatile substances in coals

In the composition of coals, along with organic substances mineral impurities are present, which are usually ballast. To evaluate coals, it is important to know the relationship between these components. Technical analysis consists of determining moisture (W), ash content (A), volatile matter (V), sulfur content (Sob), calorific value (Q) and coke residue.

Humidity reduces the heat of combustion of coals. Coals are divided into three groups: B1 - with a moisture content of more than 40%, B2 - 30-40%, B3 - 30% or less. Humidity is determined by heating to 1050 ° C or by drying in a desiccator over concentrated sulfuric acid. 1% moisture reduces the thermal conductivity of coals by 6 kcal.

Ash content. Ash is a solid non-combustible residue formed from mineral impurities of coal; by weight it is not equal to mineral impurities, because Some of them turn into gas and water vapor. Each percentage of ash reduces blast furnace productivity by 2.5%. The permissible ash content for coking coals is less than 10%; with a high ash content, coal enrichment is required. The main components that make up the ash: oxy-

oxides Si, Al, Fe, Ca, Mq, Na, K; Ti and Mn oxides are of subordinate importance.

Release of volatile substances. Refers to the combustible part; during dry distillation, coal partially transforms into volatile substances (CH 4, H, CO, CO 2, etc.) Volatile substances are very valuable. They have the ability to burn, and also form the basis for the production of various chemical products: dyes, plastics, aromatics and explosives.

Coke residue. This is a solid residue remaining after removal of volatiles, depending on the quality of the coals it has different kind. It can be powder - unsintered, sintered, fused or expanded. The sintering ability of coals is expressed in the ability, when heated under certain conditions, to combine into one whole and produce a sufficiently strong solid residue with a porous structure - metallurgical type coke. Coals that produce a powdery residue are non-caking and are suitable only for energy purposes. Sulfur is a harmful impurity in coals, especially coke coals, causing increased coke consumption during ore smelting and deteriorating the quality of iron. Based on sulfur content, coals are divided into groups: low-sulfur (up to 1.5%), medium-sulfur (1.5-2.5%), sulfur (2.5-4%), high-sulfur (more than 4%). The latter are not suitable for use in ferrous metallurgy without prior enrichment.

Heat of combustion coal is approximately 24.62 kJ/kg. It is determined experimentally - by burning coal in a calorimetric bomb, and by calculation, using formulas. Anthracite and lean coals have the highest calorific value.

In many cases, especially when assessing non-metallic minerals, in addition to studying the technical properties, chemical analyzes of raw materials (refractory and ceramic clays, limestones as fluxes, kaolin, talc, etc.) must also be carried out. For some minerals (founding sands), granulometric analysis is also carried out.

Definition release of volatile substances. When heated without access to air, coal decomposes, releasing gas and vapor products called volatile substances.

Depending on the heating temperature, after removal of volatile substances, a solid residue (crust), coke or semi-coke remains. Volatile substances are not contained in free form in the fuel, but are formed during heating, so we do not talk about the content of volatiles, but about their yield.

The yield of volatile substances depends not only on the type of fuel, but also on the conditions of its heating (dry distillation of coal). Exit volatile substances and at the same time the determined caking ability are general indicators by which the Properties and composition of coal can be approximately predicted.

The composition of volatile substances includes valuable substances that are widely used in the national economy. For example, the volatile substances of coal contain benzene, toluene, ammonia, hydrogen, methane, etc. The volatile substances formed during the dry distillation of wood contain methane, carbon monoxide, acetic acid, methyl alcohol, etc.

Type of coal Volatile yield - % Carbon content - C,% True density - 4, g/cm 413

Determination of volatile matter yield is classical method coal analysis. In almost all existing classifications of coals, volatile yield is one of the main indicators.

In Fig. the dependence of expansion pressure on release of volatiles weight of coal. From Fig. Some correlation is already visible, but when the release of volatile substances is more than 21-22%, it weakens and becomes clearer when heterogeneous coals are excluded (about 0.20).

For coals whose volatile matter yield is in the range of 17-21%, no correlation is observed at all. However, it is possible to delineate a zone that includes heterogeneous coals (curve with a dashed line), which give insignificant expansion pressure. This obviously means that any homogeneous coal with a volatile matter yield of 19-24% is not included397

The coke obtained according to such a technological scheme has fairly good physical and mechanical properties. Thus, the molded coke used for the first experimental blast furnace smeltings had the following quality indicators (at the charge yard of the metallurgical plant) M40 = 89.9%, MIO = 6%, the content of pieces with a size of 40-80 mm is 86% When calcined to 0 C in an inert atmosphere, this coke does not separate fines, does not fall apart, but, on the contrary, becomes denser and mechanically stronger. The porosity of this coke, depending on the requirements of the consumer, can be adjusted by changing the process from 35 to 60% when coking the same coal. The yield of volatile substances from commercial molded coke is 1.6-2.5%

What is coking of coals, volatile yield

Name and symbol of the coal grade Output volatile substances Y,% Coke yield, % Lump sizes, mm Characteristics of non-volatile residue (coke)

Types of coals Volatile matter yield, % and organic mass Composition, % 337

After 9-10 months of storage in stacks of different Donetsk coal output volatile substances from OS grade coals increases by 2-3%, T grade - by 1.39%, while for Zh grade coals it changed within 1.18-0.54%; in general, the change in the yield of volatile substances is relatively small .
The yield of volatile substances and the heat of combustion as a result of the oxidation of coals change differently depending on the degree of metamorphism and the molecular structure of the organic mass of coal. Release of volatile substances during long-term storage47

The yield and quality of chemical coking products depend on a number of factors, the degree of metamorphism, the petrographic composition of coals, the release of volatile substances, humidity, temperature conditions of coking, etc.10

Coal designation Volatile yield (Parr recalculation), % Bulk weight(converted to dry weight), g/lw 306

The bake depends on the properties of the coal charge (the nature of the coal, the yield of volatile substances) and the coking temperature. The burning temperature for Donbass coals is 1.0-2.6% (Donbass), and for coals from the Eastern regions of Russia it is 1.5-3.0%.85

Anthracite coal (AS) is coal particles up to 13 mm in size, screened out in mines when producing ordinary anthracite. When sorting dry anthracite for coals of class ASh, the size of the pieces is set to less than 3 mm.

For hard coal grades D, G and anthracite, when supplied to power plants for combustion in a pulverized state, also at high humidity, a class has been established with a piece size of less than 13 mm, conventionally designated DSSh, GSSH and ASH (seed with a piece). AS has the lowest volatile yield of all coal grades, which makes it difficult to ignite. Ash ash consists mainly of silicon oxide and aluminum. A small part of the ash consists of calcium, magnesium, potassium and sodium oxide.15

In the near future, the international classification of hard coals will become widespread. It is based on three very important parameters of coal: the release of volatile substances, caking and coking properties.12

The difference in the scope of analysis for hard and brown coals is determined different meaning a way out for them volatile output volatiles in bituminous coals can fluctuate greatly; here, together with the characteristics of the coke residue, it determines their grade and hydrogen content; in oxidized bituminous coals, the characteristics of the coke residue, and often the yield of volatiles, change according to the change in the calorific value and humidity of the air-dry sample. In brown coals, the yield of volatiles fluctuates -

What is the reason for the gap between the practical and calculated coke yield, or coke burn, as it is sometimes incorrectly called? The calculations are based on the value of the yield of volatile substances during crucible testing, which is identified with the practical coke yield in furnaces. However, it is known that the yield of volatile substances depends on the rate of temperature rise; with the acceleration of coal heating, the yield of volatile substances increases, which corresponds to a decrease in the yield of coke. Comparing the rate of temperature rise during crucible coking (approximately 400-500 °C per minute) and in coke ovens (about 1 °C per minute), one can see the complete discrepancy between these processes; obviously, in coke ovens the coke residue should be greater than with crucible coking testing. In addition, with an increase in the yield of volatile substances in the charge and an increase in the coking rate, the formation of graphite increases due to the pyrolysis of coke oven gas hydrocarbons.437

Replacement of classifications based on elementary analysis with classification based on two parameters - the release of volatile substances in relation to the combustible mass and physical properties- showed that the results obtained are quite convergent and the coals are also arranged in a row of the same sequence approximately as in the classification based on elementary analysis. From consideration of a large number of industrial classifications different countries it can be seen that the yield of volatile substances is the most important characteristic, which is included in almost all technical classifications hard coals. There are reasons for this, because the chemical nature of coal and its chemical age greatly affect the yield of volatile substances. As the chemical age of coals increases, the yield of volatile substances continuously decreases.569

Coal production from the Chernogorsk deposit increased in 8 compared to 0 from 1 to 2.9 million. In terms of quality, coal from the Minusinsk basin is close to gas and long-flame coals. The yield of volatile substances per combustible mass is 35-42%, the thickness of the plastic layer y = O-7 mm.

Type of coal Volatile matter yield, and Color Trait Gloss Hardness (Mohs scale) Specific gravity20

If coals consist only or predominantly of microcomponents of the vitrinite group, then the change in their properties depending on the degree of their metamorphism is well expressed by the yield of volatile substances, recalculated to the combustible mass, with an increase in the degree of metamorphism of coals, the yield of volatile substances from them decreases. This is the basis for various classifications of coals, which are especially applicable to claren-type coals, i.e., to coals with a predominant content of vitrinite (for example, coals of the Donetsk basin).8

Coal grade Technological group of coal Volatile yield, % Thickness of plastic-21

Fuel Coal grade Volatile yield per combustible mass UD v7o Lowest caloric content per combustible mass in kcal/kg Coefficient of conversion to standard fuel Calorific value of working fuel 0 in kcal/kg650

Coal grade Volatile matter yield 0/ /0 Intumescence according to AFNOR Expansion temperature, °C International dilatometry (dilatation) International classification

Pattaisky and Teichmüller 24, studying the relationship between the carbon content in humus coals and the release of volatile substances, found that with an increase in carbon content, the yield of volatile substances from coals decreases unequally at different stages of metamorphism. Thus, in brown and poorly metamorphosed hard coals, the yield of volatile substances is poorly consistent with changes in carbon content. In this case, the degree of metamorphism of coals is more clearly characterized by carbon content than by the release of volatile substances.

According to Storch and staff 11, p. 30, the elementary structural formula of carbon substance consists of indene trimers linked by ether bridges. They provide a number of evidence in favor of this structure related to the elemental composition of coal, the release of volatile substances, mechanical properties, etc. However, this formula must also be rejected, since it does not correspond to the results obtained during the oxidation of coal and its decomposition by metallic sodium.

Research by E. A. Shapatina showed that the main factor determining decomposition, and therefore loss volatile coal In the process of high-speed heating, it is not the residence time, but the heating temperature field. Based on the example of studying the process of releasing volatiles from pulverized (micron-sized) gas coal (volatile yield in the original coal is 38.8%) when it is quickly (in 0.45 s) heated to various temperatures in the range of 390-600 ° C with exposure at 71

As the particle heats up, it is heated, dried, and then sublimation of the fuel begins. The higher the content of volatiles in the fuel, the more intense their release. The release of volatiles begins at higher temperatures, the older the fuel.

From the brown ones coal output volatiles begin at a temperature of about °C, from gas coal - about °C, from PG - about °C, from lean coals - about 320 °C, from anthracite - about 380 °C L. 46. The release of volatiles continues up to temperatures of the order 800-1000°С.341

Coking ability is influenced by the petrographic composition, the degree of metamorphism of coal, the release of volatile substances, as well as the nature of changes during heating - the transition to a partial state, the degree of viscosity and the temperature range of this state, sintering, and the dynamics of gas evolution19

The gas and vapor products formed during the thermal destruction of coal undergo various transformations, which are associated with both the sintering process and the decomposition process during their evacuation. The decomposition process is influenced by the technological and thermal regimes of coking. The yield and quality of the chemical products of coking depend on a number of factors. degree of metamorphism, petrographic composition of coals, release of volatile substances, humidity, coking temperature, etc.78

To characterize the plastic properties and gas release, Bunte and Imhof tested the following German coals using this method: 1) non-expanding (sticky) coal from Upper Silesia 2) non-expanding caking coals from the Saar basin 3) Saar coal, which in properties occupies an intermediate position between the first two coals 4-5 ) two intumescent caking coals, one from Upper Silesia, the other from the Wurm deposit. For the listed five coals, the yield of volatile substances per combustible mass was respectively equal to 38.6 33.8 34.2 27.8 19.0%. Coal 1 showed a maximum pressure at 420° of only about 8 jas of water. Art. For coal 2, the maximum pressure was about 1000 mm of water. Art. at 420°, both with a sample of 10 g and 5 g. The maximum pressure for the 3rd coal was equal to 450 lsh at 440° for the 4th coal - 340 lsh at 480° and for the 5th coal - 550 ML1 at 490°.

It is known that entrainment from pulverized coal furnaces consists of a mixture of combustible particles and fly ash. The content of the latter ranges from 75 7o when burning anthracite to 99.5% in the case of burning brown coal.

As it turned out, with such a small content of combustibles in the drift, it is impossible to achieve objective results when analyzing the technical, elemental and fractional composition of the flammable part of the drift. In table

Figure 2 shows the yield of volatile substances from the entrainment of industrial pulverized coal furnaces burning various grades of coal, as well as from samples of Nazarovo brown coal taken along the length of the torch. Before analysis, the entrainments were dispersed into fractions.

It can be seen that the yield of volatile substances in the entrainment often exceeds that of the original coal. The yield of volatile substances in fine fractions is especially high.

In samples from a flare of Nazarovo brown coal, the yield of volatiles per combustible mass was 65% with a combustible content of 50% and >100% in all fractions with a combustible content of 6.61%. All this indicates that fly ash is not a completely inert material.

Apparently, during analyzes associated with high heat entrainment, ash undergoes a number of changes, interacting with flammable residues and gaseous products of their thermal decomposition. The presence of a flammable part of the entrainment creates a reducing atmosphere. Metal oxides contained in fly ash can be partially or completely reduced by reacting with carbon, as well as with gaseous products of thermal decomposition of the combustible part of the fly ash.82

The quality of coals from the Tunguska and Lena basins is very diverse and is represented by various groups of coalification - from anthracite to brown coal. Release of volatile substances from various groups coal content ranges from 5 to 59% 25.

Some regularity has been established in the distribution of coals over the basin area. Anthracite and graphite are located in the west of the basin.

In its middle part along the meridian there are hard coals with a significant release of volatile substances, and in the east there are mainly brown coals. It is noted that as one moves from east to west, the release of volatile substances in coals decreases 25.

A test for coking ability of coals from the Angarsk region showed that they have fairly good caking ability. 25 When using Tunguska coals for coking, their enrichment will be required, since the coals of the identified reserves have an ash content of up to 15%. The sulfur content of the studied coals does not exceed 1.5%. in connection with which they can be classified as low- and medium-sulfur coals.

Sandor coked briquettes of Yorkshire coal (output volatile substances 32.5%), compressed under a pressure of 698 kg/cm, when heated in a nitrogen atmosphere at a rate of 5° per minute. up to 690 and 800°. The resulting cokes were kept at the final temperature for two hours and then cooled.

The electrical resistance values ​​measured on coke blocks produced in this way during repeated heating and cooling of the latter gave curves that coincided with each other. Electrical resistance was measured in an air atmosphere in a vacuum and in nitrogen. The electrical resistance of samples stored in air increased slightly after a few days compared to the initial one. The curves of the dependence of electrical resistance on temperature, in vacuum and in nitrogen, in the temperature range -50° - -360° obeyed the equation

Similar experiments carried out on a production scale were published in the American press. In American experiments, a significant improvement in the quality of coke (Table 64) was obtained by coking coal from coal (volatile yield 38.5/about) with semi-coke from the same coal in an industrial furnace.

It has been established that, along with a decrease in the content of carbon and hydrogen, the yield of volatile substances in coals increases, the calorific value, the amount of extracted substances, etc. decrease.

During the oxidation of reduced coals, the same pattern is observed in the change in the yield of volatile substances in young and more mature coals as in the original coal that has not been subjected to hydrogenation, i.e., in gas coal, the yield of volatile substances decreases, and in lean, although it decreases, does not decrease below the output. volatile compounds in the original coal.

During the oxidation of reduced coals, a decrease in the yield of volatile substances is observed in all types of coals without exception, i.e., the oxidation process of reduced coals proceeds in the direction of a more complex molecule. However, it should be noted that for gas coal the yield of volatile substances after oxidation becomes less than that of the original coal, for coke coal it changes little, and for lean coal with a plastic layer equal to zero, it remains significantly higher than the yield of the original coal.

The Hilt rule in the Irkutsk basin is not confirmed with an increase in the stratigraphic depth of coal seams, the yield of volatile substances does not decrease, but, on the contrary,. At the same time, the content of hydrogen and sulfur in coals increases and, accordingly, the content of carbon and acid decreases.

White Charcoal Binchotan from Vietnam

Categories

Blood test for quantitative volatile content toxic substances(phenol, formaldehyde)
Poisoning (intoxication) should be understood as structural and functional changes in the body caused by external chemical factors. External chemical factors are called poisons.

While in the body, toxic substances are influenced by enzymes and other biological active substances undergo chemical transformations.

While in the body, toxic substances, under the influence of enzymes and other biologically active substances, undergo chemical transformations (oxidation, reduction, hydrolysis, etc.) with the formation of most often harmless compounds. In other cases, intermediate products are formed that have more pronounced toxic properties (acetaldehyde, oxalic acid, formaldehyde, respectively - in case of poisoning with ethyl alcohol, ethylene glycol, methyl alcohol). One of the ways to transform toxic substances in the body is the formation of free radicals, which have the ability to damage intracellular membranes with subsequent cell death. As a rule, some of the poison is excreted unchanged from the body.

Phenols
Phenols - carbolic acid, cresol, resorcinol, hydroquinone. Colorless or colored crystals or amorphous substances; often have a strong characteristic odor.

They have a local cauterizing, psychotropic (narcotic), neurotoxic (convulsive), nephrotoxic effect. The lethal dose when taken orally is 2 g. Poisoning by phenol vapors is possible if it comes in contact with the mouth or on the skin. Absorption is fast. When taken orally, phenol is quickly absorbed by the blood, transported and distributed throughout the body. In the liver, phenol undergoes biotransformation: 10% of phenol is oxidized to diatomic phenols (ortho- and para-compounds). In case of phenol poisoning in a patient, the dark green color of urine is explained by the presence of hydroquinone and quinhydrone in it.

Phenol belongs to the group of liver poisons. Its hepatotoxic effect manifests itself in the development of toxic liver dystrophy. It is expressed in an increase in the size of the liver and the appearance of pain in the liver. Jaundice, pallor, dizziness, signs of hemorrhagic diathesis, increased body temperature, disturbance mental activity. The cerebrotoxic effect of phenol is manifested by hepatic encephalopathy. Severe forms of phenol poisoning are accompanied by loss of consciousness and hepatic coma. When phenol enters the body through the mouth, pain in the stomach, diarrhea, sometimes with blood, vomiting of whitish, flaky masses are observed, the smell of phenol appears on the breath, and the urine becomes olive-colored. At autopsy: the mucous membranes of the mouth, esophagus and stomach are covered with milky spots that are hard to the touch. Protein and fatty degeneration of parenchymal organs, minor hemorrhages in internal organs and brain tissues are noted.

Formaldehyde
Formaldehyde is a colorless gas with a strong, irritating odor. Let's dissolve well in water, alcohols and other polar solvents.

Formalin is an aqueous solution of formaldehyde (usually 37 - 40%) containing 6-15% methanol (formaldehyde polymerization inhibitor). It is a colorless liquid with a characteristic pungent odor.

Formaldehyde is used in organic synthesis, in the production of synthetic resins and plastics, for the synthesis of many medicines and dyes, for tanning leather, as a disinfectant, antiseptic and deodorizing agent.

When inhaling air containing a large amount of formaldehyde, symptoms of acute poisoning develop with lacrimation, a sharp cough, and a feeling of tightness in the chest. When taken orally (in most cases erroneously), as a result of absorption of formaldehyde, loss of consciousness, convulsions, depression of nerve centers, and irritation of the kidneys are observed.

Preparation
Blood
Toxicological examination does not require special preparation. It is recommended that blood be taken no earlier than 4 hours after the last meal.
Before diagnosis, it is not recommended to expose yourself stressful situations, drink alcohol and smoke.
Diet and medications do not affect the results of the study.

Urine
On the eve of the test, it is not recommended to eat vegetables and fruits that can change the color of urine (beets, carrots, cranberries, etc.), or take diuretics.

Collect the morning portion of urine excreted immediately after sleep. Before collecting urine, it is necessary to perform a thorough hygienic toilet of the external genitalia. When urinating for the first time in the morning, release a small amount of urine (the first 1-2 seconds) into the toilet, then collect the entire portion of urine in a clean container without interrupting urination. Pour approximately 50 ml of urine into a sterile plastic container with a screw cap. When collecting urine, it is advisable not to touch the container to your body. It is necessary to deliver the container with urine to the medical office as soon as possible from the moment the biomaterial is taken.

Interpretation of results

Blood, urine
Units: µg/ml.

The answer is given in quantitative format.

One of the most important thermal characteristics of fuels is the volatile yield and the properties of the coke residue.

When solid fuels are heated, thermally unstable complex oxygen-containing hydrocarbon compounds of the combustible mass decompose with the release of flammable gases: hydrogen, hydrocarbons, carbon monoxide and non-combustible gases - carbon dioxide and water vapor. The yield of volatile substances is determined by heating a sample of air-dry fuel in an amount of 1 g without access of air at a temperature of 850°C for 7 minutes. The volatile yield, defined as the decrease in the mass of the test fuel sample minus the moisture contained in it, is referred to as the combustible mass of the fuel.

Different fuels have different composition and heat of combustion of volatile substances. As the chemical age of the fuel increases, the content of volatile substances decreases and their release temperature increases. At the same time, due to a decrease in the amount of inert gases, the heat of combustion of volatile substances increases. For shale, the volatile yield is 80-90% of the combustible mass; peat - 70%; brown coals - 30-60%, hard coals of grades G and D - 30 - 50%, for lean coals and anthracites the volatile yield is low and, accordingly, equals 11-13 and

2-9%. Therefore, the content of volatile substances and their composition can be taken as indicators of the degree of carbonization of the fuel and its chemical age.

For peat, the release of volatiles begins at a temperature of approximately 100°C, brown and fatty coals - 150-170°C, oil shale - 230°C, lean coals and anthracites ~400°C and ends at high temperatures - 1100-1200°C.

After distillation of volatile substances from the fuel, a so-called coke residue is formed. When coal contains bituminous substances, which when heated turn into a plastic state or melt, a powdered sample of coal tested for volatile content can cake and swell. The ability of a fuel to form more or less strong coke during thermal decomposition is called sinterability. Peat, brown coals and anthracite provide. powdered coke. Hard coals with a volatile yield of 42-45% and lean coals with a volatile yield of less than 17% produce powdery or sticky coke residue.

Coals that form a caked coke residue are a valuable technological fuel and are used primarily for the production of metallurgical coke. Coke in the form of a sintered or fused residue is obtained by heating crushed coke to

3-3.5 mm of coal at a temperature of 1000°C without air access. The properties of coke depend on the composition of organic compounds of the combustible mass of fuel and the content of volatile substances in it.

A further improvement of two-chamber furnaces were cyclone furnaces, in which the combustion process is intensified by increasing the specific combustion rate and increasing the residence time of fuel particles in the combustion chamber. The following types are available...

To intensify the combustion process and increase the reliability of work with stable liquid slag removal in a wider range of loads, we switched to multi-chamber furnaces. In them, the combustion process is completely carried out into the combustion chamber...

To increase the stability and intensity of operation of steam generators with a capacity of up to 75 kg/s with liquid slag removal and increase slag collection, furnaces with intersecting jets were developed and introduced. In a firebox with intersecting jets...

GOST R 55660-2013

NATIONAL STANDARD OF THE RUSSIAN FEDERATION

SOLID MINERAL FUEL

Determination of volatile matter yield

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 of the Russian Federation TC 179 "Solid Mineral Fuel"

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").
________________
* 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
________________
* 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

Introduction

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

Test results are relative, so 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 of 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. Are common technical 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 preparing 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 an undated reference standard is replaced, it is recommended that the current version of that standard be used, taking into account any changes made to that version. 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 throttle valve to restrict 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 N 3 of high shape with lids according to 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 size of the working area allows) (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 rate 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 allowed 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 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 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 volatile matter yield of coals are characterized depending on their appearance and strength as follows:

- powdery;

- stuck together - 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

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, coal, brown coal, anthracite, oil shale, coke, method of determination, yield of volatile substances

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official publication
M.: Standartinform, 2014