Comparison of differential and integral methods for coal oxidation kinetic analysis

The influence of two different methods of kinetic analysis on obtained values of kinetic constants of coal oxidation process was studied. The oxidation of T-grade bituminous coal of Kuznetskiy deposit and 2B-grade lignite of Borodinskoe deposit was investigated by means of thermogravimetric analysis. All measurements were carried out with heating rates 2,5, 10, 25 and 40 K/min in temperature range 300-1100 K in air medium. The dependences of activation energy and frequency factor on conversion were obtained using two isoconversional methods: differential method of Freidman and integral method of Kissinger-Akahira-Sunose. The average values of activation energy which were obtained by KAS method were higher by 14.5 % for bituminous coal and 23.3 % for lignite in comparison with values obtained by Freidman method. The same relations were observed for frequency factor values

Reasons for tangerine peel utilization in the composition of mixed fuels based on bituminous coal

Application analysis of processed tangerine peel in a mixture with T grade coal (lean) as a fuel for hot water boilers is presented. Technical characteristics, as well as conditions and ignition delay times for such mixed fuels at different mass concentrations of the initial components, have been experimentally determined. The experiments were carried out in air at temperatures from 600 ° C to 800 ° C. Record of ignition and combustion processes of composite fuel samples was carried out using a high-speed video camera (image format — 1024 Ч 1024 pixels, frame rate — up to 1000000 per second), which ensures high discretization of the recording results of characteristic process times. A temperature limit has been identified for the stable ignition of such fuels. It has been established that an increase of tangerine peel proportion in the mixture leads to acceleration of ignition processes of the studied mixed fuels. Reasons for application of fuel mixtures based on bituminous coal and food waste in the small energy sector have been provided

Justification of the Energy Use of Cedar Husk Waste as an Environmentally Friendly Additive for Co-Combustion with Coal

In this paper, the properties of ignition of mixed fuel pellets formed on the basis of fairly typical energy coal and wood industry waste in the form of cedar husks are experimentally established. The technical characteristics of the initial fuel components and the mixtures based on them, the ignition delay times for different mass concentrations of biomass in coal, and the composition of flue gases formed during the thermal decomposition of these mixed fuels and their base components were determined. Pellets of mixed fuels were made by a hydraulic press. The experiments were performed in an air environment at temperatures from 600 °C to 800 °C. Recording of the processes of pellet ignition and combustion was carried out using a high-speed video camera with an image format of 1024 Ч 1024 pixels, and a frame rate up to 500 frames per second. The analysis of the flue gas composition was performed using a Test-1 factory gas analyzer (BONER Co.). It was found that the increase in the share of biomass up to 50% in the mixed fuel led to a significant reduction in the ignition delay time to less than 1 s and the sequestration of sulfur oxide emissions by 37.6% and of nitrogen oxides by 3.8% in the studied granular mixed fuels

On the Effect of the Distances between Coal and Wood Particles during Their Joint Pyrolysis on Sulfur Oxides Formation

The simultaneous pyrolysis of coal with wood was experimentally found to allow reducing concentrations of sulfur-containing substances in gases released. The objective of experimental studies is comparison of the sulphate of calcium and aluminum in the ash of coal-wood mixtures after pyrolysis of the latter in a dense “packing” of aggregate particles of these two fuels and at a few millimeters distance between particles. The 3B-grade lignite, T-grade bituminous coal and pinewood sawmill waste were chosen as feedstocks for pyrolysis experiments because they are widespread in Russia as well as many other countries. The elemental composition of all raw materials and pyrolysis residues was determined. The inorganic composition of obtained pyrolysis product in the solid phase was characterized by X-ray analysis. The content of aluminum and calcium sulfate in residue in case of simultaneous processing of coal with wood was found to be higher, compared to the processing of coal only (within the random errors of the experiment), than those established for such mixtures under conditions of dense “packing” of large masses (up to 15 g)

Justification of the Reduction Possibility of Sulfur Oxides and Fly Ash Emissions during Co-Combustion of Coal and Waste from Woodworking Enterprises

In this work, we experimentally investigated the effect of widespread biomass (woodworking waste—pine sawdust) in the composition of mixed fuel, formed also using the widespread steam coals metalignitous (D) and lean (T), on the concentration of sulfur, nitrogen and carbon oxides in flue gases. Investigations of composite fuels with a mass of at least 5 g were carried out in a reactor with continuous recording of the composition of the flue gases formed during the thermal decomposition of the investigated fuels. Thermal decomposition of fuels was carried out in the temperature range from 293 K to 873 K. It was found that an increase in the proportion of wood components in mixed fuels based on two different coals from 10% to 50% leads to a significant decrease in the concentration of sulfur oxides from 11% to 95.8% relative to the concentration of the formation of sulfur oxides in a homogeneous coal, respectively. It was found that an increase in the proportion of the wood component in the mixture with grade D coal up to 50% leads to a significant increase in the content of calcium sulfates (45.1%) and aluminum (43.2%) in the blended fuel. The increase in the content of these salts in the ash of mixed fuels based on T coal and wood is 35.1% and 38.6%, respectively. The obtained research results allowed us to conclude that woodworking wastes are an effective addition to the coals of various deposits, which would help to reduce anthropogenic-induced gas emissions when they are co-combusting in the furnaces of power boilers

Study of the physical-chemical characteristics of non-food solid waste combustion

The ignition and combustion processes of six non-food municipal solid waste (MSW) samples of different type were studied. The samples of wood waste, rubber, leather, cardboard, textile and plastic were put into the combustion chamber at a temperature of 600 °C in air medium at atmospheric pressure. The observations were carried out by means of high-frequency video imaging of the combustion process. Based on the obtained results the characteristic times of the ignition delay, combustion of volatiles and carbon residue were defined. The highest values of ignition delay and combustion of the carbon residue times were obtained for rubber sample and were 11.3 and 285 s, respectively. Significant correlation was found between the time of volatiles and carbon residue combustion and the fixed carbon content of the sample: the higher the Cd content, the higher value of respective time. The concentration peaks of the gas-phase products release during combustion of non-food MSW were presented as well

Effect of Cu(NO3)2 and Cu(CH3COO)2 Activating Additives on Combustion Characteristics of Anthracite and Its Semi-Coke

The process of anthracite and its semi-coke combustion in the presence of 5 wt.% (in terms of dry salt) additives of copper salts Cu(NO3)2 and Cu(CH3COO)2 was studied. The activating additives were introduced by an incipient wetness procedure. The ignition and combustion parameters for coal samples were examined in the combustion chamber at the heating medium temperatures (Tg) of 600-800 °C. The composition of the gaseous combustion products was controlled using an on-line gas analyzer. The fuel modification with copper salts was found to reduce the ignition delay time on average, along with a drop in the minimum ignition temperature Tmin by 138-277 °C. With an increase in Tg temperature, a significant reduction in the ignition delay time for the anthracite and semi-coke samples (by a factor of 6.7) was observed. The maximum difference in the ignition delay time between the original and modified samples of anthracite (ΔTi = 5.5 s) and semi-coke (ΔTi = 5.4 s) was recorded at a Tg temperature of 600 °C in the case of Cu(CH3COO)2. The emergence of micro-explosions was detected at an early stage of combustion via high-speed video imaging for samples modified by copper acetate. According to the on-line gas analysis data, the addition of copper salts permits one to reduce the volume of CO formed by 40% on average, providing complete oxidation of the fuel to CO2. It was shown that the introduction of additives promoted the reduction in the NOx emissions during the combustion of the anthracite and semi-coke samples