Автор: Platova O.K., Dedovets I.G., Boyko V.N.
Источник:Young scientists’ researches and achievements in science = Научные исследования и достижения молодых ученых: сборник материалов научно-практической конференции 25 апреля 2024 года / Под общей редакцией Е.Н. Кушниренко. – Донецк: ДОННТУ, 2024 – 326–333 с.
Platova O.K., Dedovets I.G., Boyko V.N. STUDY OF THE INFLUENCE OF THE ELEMENTAL COMPOSITION OF RAW MATERIALS FROM COKE PLANTS IN DONBASS ON THE PROPERTIES OF THE RESULTING PRODUCTS
Coal is a solid combustible sedimentary rock formed from the remains of dead plants as a result of biochemical, physicochemical, chemical and physical changes. Fossil coals are characterized by a wide variety of chemical compositions, and therefore have a wide variety of properties. This is what determines the possibility of its use in almost all sectors of the national economy – from an ordinary stove to spacecraft.
The article discusses a method for determining carbon and sulfur in coals, which is based on the oxidation reaction to oxides using special equipment – Carbon and Sulfur Analyzer CS-3000
.
coal, elemental composition, oxidation reaction, sulfur, carbon, coal combustion, semi-coking, coking, CS-3000 analyzer.
Sulfur is contained in all types of solid fuels in the form of various compounds included in the organic and mineral parts of fuels. Sulfur is an undesirable and even harmful part of fuel.
When coal is burned, it is released in the form of SO2, polluting and poisoning the environment and causing corrosion of metal surfaces. When coal is used in metallurgy, sulfur goes into the metal, deteriorating its quality. When fuel is burned, sulfur forms sulfur compounds, which react in the atmosphere with water vapor to form sulfuric acid, which falls as acid rain. In small-scale power generation, sulfur is the main factor limiting the minimum thermal loads of boilers, since at low temperatures of flue gases condensation falls on the tail surfaces, and sulfur dioxide from the combustion products combines with the condensate to form sulfuric acid, which destroys the metal of the boilers.
Coals are most commonly used in three cases:
The sulfur compounds contained in coal undergo transformation during the above mentioned processing methods. It is the study of this transformation that is the basis for coal enrichment.
When coal is extracted, the coal immediately interacts with air and light, and the substance undergoes changes under the influence of oxygen and humidity. Sulfur metals turn into sulfates in air.
The formation of FeSO4, SO2, H2SO4 from FeS2 should be taken into account when storing coal, especially if it is stored openly and can get wet.
There was a lot of debate about whether the oxidation of sulfur pyrites is the cause of spontaneous combustion of coals or is it just a passing phenomenon. However, as it turned out, the reason for the spontaneous combustion of coals is the ability of organic coal matter in air to absorb oxygen, and the presence of pyrite or marcasite plays only a secondary role. Combustion of coal in domestic or industrial furnaces is the most important and common use of coal.
Sulfur, which is found in soot and fly ash, is also harmful. When interacting with water, it releases hydrogen sulfide.When coal containing sulfur compounds is burned, sulfur dioxide is released into the atmosphere. In moisture it dissolves to form H2SO3, which is then oxidized to H2SO4. This leads to acid rain, which in turn leads to the death of vegetation.
The release of hydrogen sulfide during coking begins at a temperature of 300°C and continues with its further increase. However, coke still contains sulfur. When coking coal, half of the sulfur turns into gas in the form of hydrogen sulfide, of the second half, a tenth turns into tar, and the rest remains in the coke. During semi-coking, 70% of the sulfur remains in the semi-coke, approximately one tenth in the tar, and the remainder in the form of gas (2-3% hydrogen sulfide). In general, we can say that during heat treatment, sulfur is partially removed due to the decomposition of pyrite. However, up to 70% of sulfur goes into semi-coke or coke.
Sulfur compounds negatively affect the thermal treatment of solid fossil fuels. This leads to technological and environmental problems: poisoning of catalysts, corrosion of equipment, air pollution, as well as a change in the coking ability of coal. High sulfur content has a negative effect on the strength of coke; coke rich in sulfur is softer.
Coal gasification is based on incomplete combustion of coal due to a lack of oxygen or the reaction of carbon with carbon dioxide or water vapor to produce combustible gases. In the generator, the loaded coal is first dried, then distilled, gasified and finally burned. Gases pass through layers of coal and are reduced by a hot layer of coke. Sulfurous acid combines with hydrogen to form hydrogen sulfide. Sulfur is contained in the generator exclusively in the form of this compound.
The hydrogen sulfide content in gases depends on the following factors:
In general, 40% of sulfur goes into gas, the remainder is contained in ash and slag. If the gas generator operates with dry air, the amount of sulfur in the gas is significantly less.
The choice of ways to use coals often depends on their carbon content, total sulfur and its varieties. The forms of sulfur are determined, as a rule, when it is necessary to fully characterize high-sulfur and high-ash fuels.
The methods for determining carbon and sulfur are based on the oxidation reaction of all forms to oxides, followed by their determination in various ways. The principle of operation of the equipment The Carbon and Sulfur Analyzer CS-3000
is similarly based on the combustion of portions of the samples under study. Time for analysis takes 40 seconds.
The sample and flux are placed in a ceramic crucible and burned in a high-frequency furnace by passing oxygen, carbon and sulfur respectively to form CO2 and SO2. The concentration of CO2 and SO2 in the gases released during combustion is determined by the method of absorption of infrared radiation; based on this, the mass fraction of carbon and sulfur in the original sample is calculated. The output signal obtained by the infrared detector, corresponding to the concentration of CO2 и SO2, is non-linear and requires linear calibration during analysis.
The precise method is to first linearly adjust each output signal obtained, then double integrally sum to obtain the integral areas corresponding to the carbon and sulfur content of the sample. Thus, the mass fractions of carbon and sulfur in the original sample are calculated. The curve shown on the display during sample analysis is the curve before linearization. The parameters obtained by linearization and integration have a linear dependence on the absolute mass of carbon or sulfur in the sample. The relationship between this integral area and the amount of carbon and sulfur in the sample is then established by calibrating a reference sample. The slope of this image after calibration of the reference sample is called the correction factor, and its segment, cut off on the coordinate axis, in turn, is the value of the blank sample for the device. The computer calculates the mass fraction of carbon and sulfur based on the integral area, sample weight, correction factor and blank value, and displays as a percentage: %C and %S. The measurement result contains a value for the blank sample, which can be determined in advance and automatically subtracted from the result.
For the first time, using analyzers, a method for determining carbon and sulfur was developed, in which the program itself calculates the selection of optimal temperatures, flow rates and other conditions for combustion with oxygen, and calculates the mass fraction based on the obtained integral area and mass of the sample.
The scientific significance lies in the fact that the method takes into account the main disadvantages of the most popular methods for determining carbon and sulfur. For example, analysis time is accelerated.
The practical significance of the study lies in the fact that the developed method allows you to quickly and accurately determine the amount of sulfur in the raw materials of coke plants for rational use and production of high-quality products without harm to the environment.
The reliability of the method results is due to:
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