Specific Calorific Value Research Articles

Mathematical model for heat transfer during underground coal gasification process

Purpose. To develop a mathematical model of the “coal-gas” medium heat transfer during underground coal gasification to predict the combustion face advance velocity and the duration of gasification column mining. Methodology. To detect the temperature fields in the coal seam and gas, depending on the displacement length of the phase transition boundary, a boundary-value problem of mathematical physics has been developed. To solve this boundary-value problem, Boltzmann transformations, as well as methods for solving ordinary differential equations, are used. Newton-Raphson method, which has quadratic convergence, is used to find the roots of the transcendental equation. Findings. Tendencies in the formation of mathematical models when studying temperature fields around an underground gasifier have been analyzed, with highlighting their disadvantages. A mathematical model of heat transfer during underground gasification has been developed, taking into account the phase transition boundaries of the “coal-gas” medium. A computational experiment was conducted to determine the temperature of the phase transition boundary based on the length of the gasification column and the duration of the process. Originality. A mathematical model for heat transfer during coal gasification in the form of a boundary-value problem of mathematical physics, which consists of parabolic heat-transfer equations, the Stefan condition at the phase transition boundary, and the Dirichlet boundary conditions, has been constructed. As a result of solving the boundary-value problem, a self-similar solution has been obtained for the distribution of the coal seam and gas temperature fields, as well as the position of the phase transition boundary depending on the gasification duration and on the medium density, thermal conductivity coefficients, specific heat capacity of gas and coal, specific calorific value and temperature of coal combustion, initial coal temperature and constant temperature of the gasification process. The conducted analysis of numerical calculations provides a deeper understanding of the dynamics of underground coal gasification process and makes necessary corrections to achieve the maximum process efficiency. Practical value. A methodology for determining the displacement length of the phase transition boundary of the “coal-gas” medium has been developed, taking into account the change in the combustion face temperature along the gasification zone length depending on the duration of this process. Application of the methodology makes it possible to predict the time of mining the gasified coal column for drawing up a calendar plan for mining operations.

Stability of Pure Biodiesel (B100), Biodiesel Mixture (B40), and Petroleum Diesel (B0) Due to Storage

Biodiesel is produced from synthetic ester compounds of vegetable and animal oils through a process of refining, bleaching, degumming, transesterification, and esterification. The quality and characteristics of the fuel are greatly influenced by the storage. The purpose of this research is to determine and analyze the effect of storage conditions on the physical and chemical changes of biodiesel (B100), biodiesel blend (B40), and petro diesel (B0). Experiment was conducted by storage fuels using glass bottle for 35 days arranged into four conditions based on cap and wrapping using aluminum foil, namely P1 (with cap, with wrapping), P2 (with cap, no wrapping), P3 (no cap, with wrapping), and P4 (no cap, no wrapping). Results showed that fuel quality decreases due to storage indicated by an increase in water content, density, acid number, and color parameters, as well as a decrease in the specific calorific value of all fuels. The condition of the storage container affected the changes the quality parameters. Based on its impact on fuel quality decline, the order of storage container conditions from the best is P1 (with cap, with wrap) > P2 (with cap, no wrap) > P3 (no cap, with wrap) > P4 (no cap, no wrap). Keywords: Biodiesel, Biodiesel blend (B40), Diesel fuel, Stability, Storage time.

Research of processes of thermochemical disposal of components of the morphological composition and model analogs of MSW

The article emphasizes that processing and disposal of household waste mainly concerns large densely populated cities, where millions of cubic meters of solid household waste (MSW) are accumulated annually. It was noted that thermal methods of solid waste disposal are among the most advanced methods of their processing. The advantage of these methods is a significant reduction in the volume of processed material. When waste is burned, its weight is reduced by 85-90%. In addition to reducing the volume and mass of waste, incineration of household waste allows you to obtain additional energy resources. Indicators of the amount of heat of combustion of MSW are similar to indicators of brown coal - from 1000 to 3000 kcal/kg.
 To date, existing waste incineration plants have a number of disadvantages, the main of which is low efficiency. The rate of useful use of thermal energy does not exceed 65%, even with the use of a more advanced property.
 The combustion processes themselves, the formation and composition of ash residues are affected by a large number of factors, starting with the properties and characteristics of the fuel, the physical and chemical properties of the raw materials, the parameters of the combustion process, the dispersed size of the fuel, the type of reactor, and the level of oxygen in the working area.
 Thus, the selection of the range of temperatures and pressures, the rate of heating of the gas medium for the thermogravimetric method of disposal of carbon-containing waste plays a decisive role in overcoming the shortcomings of this method.
 The purpose of the article is the development of a thermogravitational installation for studying the peculiarities of the flow of kinetic processes during the combustion of MSW samples.
 The article presents the development of an experimental thermogravitational unit for researching processes of thermochemical processing of carbon-containing alternative fuels with wide possibilities, which allows to study the influence of technological parameters on the combustion process. A description of the main nodes and the measurement system, the methodology of the experiment and the analysis of the obtained data is given. 
 A series of experiments was conducted with all the main components of solid waste: wood, food waste (potatoes, meat), office and chart paper, leather, garden waste, tetrapak, plastic. It is shown that the nature of the mass change curves of various components practically does not depend on their chemical composition and is determined mainly by the staged course of the combustion process, and the latter, in turn, by the rate of heating of the sample, the only exception being the combustion of plastic. The oxidation time of all components, except plastic, after reaching the temperature of the beginning of combustion (~ 200-250, sometimes 300 °С) is from 5-7 to 40-50 minutes, while the intensive combustion of plastic ends in 1 minute. 
 It was determined that the composition and thermophysical properties of ash play an important role in the processes of thermochemical disposal of MSW, affecting the value of the specific calorific value of MSW as a fuel and the value of the adiabatic temperature of the gaseous products of the process.

Enhancing and upgrading biogas and biomethane production in anaerobic digestion: a comprehensive review

Anaerobic digestion (AD) processes can face operational challenges or flaws such as substrate structure and characteristics complexity, process complexity, low productivity, inefficient biodegradability, and poor stability, which suppresses or reduces biogas and biomethane production. As a result of the need to overcome these challenges/shortcomings and improve or enhance biogas and biomethane yield, process intensification methods have gained attention. There is some literature review on pretreatment and co-digestion as a means of improving AD performance; however, there is no systematic information on the various strategies required for improving AD performance and, in turn, increasing biogas/biomethane yield. The AD process produces biogas, a valuable renewable biofuel. Biogas is composed primarily of biomethane and other undesirable components such as carbon dioxide, oxygen, hydrogen sulphide, water vapour, ammonia, siloxanes, nitrogen, hydrocarbons, and carbon monoxide, which act as impurities or contaminants and tend to reduce the biogas specific calorific value while also causing various problems with machine operation. As a result, various technologies are used to improve raw biogas quality by removing contaminants during biogas transformation to biomethane. As a result, this paper provides a comprehensive review of the various systematic process intensification strategies used to overcome AD process challenges/shortfalls, improve or enhance biogas and biomethane production, and conventional and emerging or advanced technologies for biogas purification, cleaning, and upgrading.

Mathematical models for estimate of the ecological consequences of the impact of the pyrogenic factor on forest ecosystems

There is a need for the development of simple analytical mathematical models of the burning of large forest areas, necessary for the assessment of the ecological consequences of the impact of the pyrogenic factor. Purpose. Develop mathematical models describing the spread of large-scale forest fires aimed at estimate the ecological consequences of the impact of the pyrogenic factor. Methods. Analytical review of research on the problem, theoretical and computational, mathematical modeling. Results. The results of the main parameters analysis of large forest areas combustion are presented. These include the area covered by the fire, the duration of the fire, the burnout time, the specific mass of combustible materials, the energy and power of combustion, the specific calorific value, the intensity of combustion, the movement speed of the combustion front, the influx of combustible materials, etc. Simple analytical mathematical models of large forest areas combustion have been established. These include the following models: a model with a constant growth rate of the fire area, a two-dimensional model, a model with sectorial movement of the combustion front, a model with a linear growth of the length of the combustion front, a model with a quadratic growth of the change rate of the fire area, and a generalized model. A new fire intensity classification has been proposed, containing 1–7 points from extremely low to extreme intensity. The maximum area covered by the fire (10–100 thousand km2), combustion energy (1–10 EJ) and combustion power (0.1–1 PW) have been estimated. Conclusions. Simple analytical mathematical models of the combustion process of large forest surface areas, which are necessary for quantitative assessment of the ecological consequences of fires, have been developed.

Dietary Catering: The Perfect Solution for Rational Food Management in Households

The problem of food waste is a global phenomenon. Food waste occurs at all stages of the food chain. Households, especially in developed countries, produce the most food waste. In order to effectively prevent consumers from throwing food away, it is important to understand the factors that determine these behaviors in the household. The aim of this study was to define the goal of using dietary catering in Polish society as a form of consumption of wholesome meals with a specific calorific value and distribution of macronutrients in the aspect of reducing losses related to food waste. The research was carried out online in the years 2020–2022 among the clients of a catering company. The survey respondents were residents of the Małopolskie Voivodeship in Poland. The research tool was an original anonymous questionnaire in the form of a shortened nutritional interview. On the basis of the obtained results, it can be concluded that factors such as age and gender influence consumer behavior. The reasons for the decision to choose dietary catering were mainly indicated as wasting and throwing away food, as well as inadequate management of food supplies and preparing too large portions of meals.

Combustion effectivity of high ash coal in adiabatic calorimeter

A series of coal-mineral matter mixtures was investigated by bomb combustion calorimetry (IKA C4000, Germany) to elucidate boundary for ash content in coal at which combustion proceeds with lowered efficiency. For the experiments, a high rank bituminous coal was mixed with particles of mine stone, both being milled to size below 0.2 mm. Before the usage, the sample of stone was heated at 900°C for 2 hours in air to stabilize mineral matter composition. Mixtures 5, 10, 15, 20, 25, 30, 40, and 50% of coal were used, with sample weights both of 1 g and/or 2 grams being applied. The efficiency of the combustion process at the bomb test was assessed of the measured calorific value and that of “theoretically” calculated. The “theoretical” calorific value of the mixture was determined from the actual content of the coal proving known specific calorific value (36.6 MJ/kg). Based on the measurements, mineral matter content of about 50% was found as limiting for fully efficient combustion of coal in the bomb calorimeter. At content of 90% of mineral matter, the efficiency of combustion is about 70 % (sample weight 1 g) and/or 50 % (sample weight 2 g). Afterwards, the combustion efficiency steeply decreases to zero.

Combustion, Pyrolysis, and Gasification of Waste-Derived Fuel Slurries, Low-Grade Liquids, and High-Moisture Waste: Review

The article discusses the modern achievements in the field of thermal recovery of industrial and municipal waste. The average accumulation rate and calorific value of typical wastes were analyzed. The focus is on the opportunities to exploit the energy potential of high-moisture waste, low-grade liquid components, and fuel slurries. We consider the relevant results in the field of combustion, pyrolysis, and gasification of such fuels. The main attention is paid to synergistic effects, the influence of additives, and external conditions on the process performance. Vortex combustion chambers, boilers with burners, and nozzles for fuel injection, grate, and fluidized bed boilers can be used for the combustion of waste-derived liquid, high-moisture, and slurry fuels. The following difficulties are possible: long ignition delay, incomplete combustion, low combustion temperature and specific calorific value, high emissions (including particulate matter, polycyclic aromatic hydrocarbons), fast slagging, and difficult spraying. A successful solution to these problems is possible due to the use of auxiliary fuel; boiler modifications; oxy-fuel combustion; and the preparation of multi-component fuels, including the use of additives. An analysis of methods of waste recovery in the composition of slurries for fuel gas production showed that there are several main areas of research: pyrolysis and gasification of coal–water slurry with additives of oil waste; study of the influence of external conditions on the characteristics of final products; and the use of specialized additives and catalysts to improve the efficiency of the pyrolysis and gasification. The prospects for improving the characteristics of thermochemical conversion of such fuels are highlighted.

Аналіз обсягу виробництва українськими коксохімічними підприємствами коксового газу у 2020 році.

It has been carried out the properties, production volume and application balance analysis of coke oven gas, produced in 2020 by seven Ukrainian coke-chemical enterprises and plants, located at the territory controlled by Ukraine. Studies have been established the total volume of raw coke oven gas to be purified from hydrogen sulfide (given up to 4000 kcal/m3 ) – 4223,4 million m3 and the degree of its purification – 88,7 %, which compared to 2019 is less by 1,8 % (in quantitative terms per 76 million m3 ) and 1,1 %, respectively. Physicchemical properties indicators of heating coke oven gas in terms of hydrogen sulfide and naphthalene mass concentration, as well as lower specific calorific value, corresponded to the norm for the Ι grade. The total volume of coke oven gas (given up to 4000 kcal/m3 ), produced by coke-chemical enterprises and plants, was equal to 4239,7 million m3 , coke oven gas output from 1 ton of dry charge – 351 m3 , which compared to 2019 is less by 2,0 % (in quantitative terms per 87082 thousand m3 ) and more by 0,3 % (in quantitative terms per 1 m3 ), respectively. According to 6 enterprises, the volume of purified coke oven gas (given up to 4000 kcal/m3 ) used for own needs amounted to 70 %, provided for metallurgists and other consumer’s needs – 25 %, unused – 5 %. Because of consequences of hostilities, the issue of the ability of domestic coke-chemical enterprises to manufacture products becomes very relevant. The analysis presented in the article should be used to assess the losses caused to Ukrainian enterprises and plants by the armed aggression of the Russian Federation. Keywords: analysis, coke-chemical production, coke oven gas, fuel, moisture, coal tar, crude benzene, hydrogen sulfide, condensation, purification, directions of the application, balance. Corresponding author S.V. Chaplianko, e-mail: chaplianko_sv@ukr.net

ANALYSIS OF CALORIMETRIC METHOD OF MEASUREMENT OF NATURAL GAS CALORIFIC VALUE

The article considers the current methods of measuring the calorific value of natural gas which are valid in the upto-date gasometry. The procedure for measuring the gross and net volume-basis specific calorific value of natural gas by the calorimetric method is analyzed. It is shown that to increase the accuracy and validity of measurement results, the experiment to determine the values of gross and net volume-basis specific calorific should be performed for at least 5 samples of the investigated gas. A methodology for estimating the accuracy of measuring the gross and net volume-basis specific calorific values of natural gas by the calorimetric method by finding estimates of the uncertainty of the obtained measurement results taking into account both random and systematic influencing factors are developed. The uncertainty budgets for measuring the gross and net volumebasis-specific calorific values of natural gas have been developed for the practical implementation of the methodology. The results of experimental studies of samples of one of the natural gas fields are given and the objective values of the gross and net volumebasis specific calorific with estimates of extended uncertainty are obtained.

The correlations of the particle size, calorific value, moisture- and ash content of waste derived fuel, and examination of its heavy metal content

Significant development has taken place in the field of waste management recently in the preparation of the energetic exploitation of recyclable, non-hazardous municipal solid waste. With mechanical-biological waste treatment, 35-40% of the weight of this waste can be made appropriate for energetic exploitation, mainly for co-incineration in cement factories and power plants.
 The recoverability of waste derived fuel produced in mechanical-biological waste treatment plants highly depends on the burning and combustion technological properties of the mixture, and on its compounds influencing burning and different emissions. Waste recovery facilities do not take over fuel below a specific calorific value and over a given heavy metal, halogen and pollutant content.
 In our research we were looking for correlations in the particle size, calorific value, moisture-, ash- and heavy metal content of waste derived fuel. On the basis of the measurement results, the connection between the particle size fractions and the fuel properties can clearly be stated. The fractions of smaller particle size have higher moisture-, ash- and heavy metal content, while the fractions of bigger particle size have higher calorific value.

Thermal effect of hydrocarbon fuels combustion after a sudden change in the specific calorific value

Using associated gas and waste oil refineries in thermal power plants, a complex problem due to the variability in fuel composition. This article explores the burning of hydrocarbon fuel in the case of an abrupt change in its specific combustion heat. Results of the analysis allowed developing a technique of stabilizing the rate of heat release, ensuring complete combustion of the fuel and its minimum flow.

Comparative Analysis of Combustion Vs Auto-gasification of Prosopis Juliflora Sticks for Rural Household Application

In 1870's the concern about deforestation, desertification and fuel wood shortage leading to the introduction of the Prosopis juliflora in India. The pro-line content in Prosopis is high under stress conditions, which helped the plant to thrive under extreme draught. Since Prosopis juliflora is abundantly available in rural areas, Indian rural households mainly depends on firewood for cooking and other thermal application using combustion route. The conversion efficiency of such system is very low and also degrade the environment. This paper analysis the combustion Vs autogasification route of converting Prosopis juliflora strikes into thermal as well as power application due to its high calorific value and ash properties. A novel gasification approach called autogasification has been employed converting solid combustible to gaseous fuel without supplying of oxygen to enrich specific calorific value of producer gas.

Effect of volatile retention on the products from low temperature pyrolysis in a fixed bed batch reactor

This study looks at the effect of volatile retention, within a batch reactor, on the products from fixed bed coal pyrolysis. It has been found that increased retention of volatiles within the reactor can increase the specific calorific value of the solid product. Increased confinement can also increase the specific calorific value of the gas, by increasing the production of methane and ethane from the reactor. The oxygen content of the coal is also shown to be an important parameter in determining the degree of upgrading that can be achieved. The reactivity of the chars from the fixed bed has also been tested in a drop tube furnace. Increasing treatment temperature and increased confinement have been shown to decrease the reactivity of the solid, as measured by combustibles remaining from the drop tube. It is concluded that increased confinement during pyrolysis in a fixed bed batch reactor may improve both the gas and solid products in terms of heat content, although problems may be encountered in burning the solid, in conventional pulverised fuel boilers.