Search Results (6)

The study presents a comprehensive assessment of the combustion efficiency of low-grade coal from the Karazhyra deposit in small- and medium-capacity boiler units of the energy workshops operated by Vostokenergo LLP (East Kazakhstan Region, Kazakhstan). It was found that the average annual thermal energy output amounts to 2,387,348.85 GJ with a coal consumption of 164,328.5 tons. Based on operational data from 2016 to 2017, the average thermal efficiency (boiler efficiency) was 66.03%, with a maximum value of 75% recorded at the Zhezkent energy workshop. The average lower heating value (LHV) of the coal was 19.41 MJ/kg, which is below the design value of 20.52 MJ/kg, indicating the use of coal with reduced energy characteristics and elevated ash content (21.4%). The unburned carbon content in the ash and slag waste (ASW) was determined to be between 14 and 35%, indicating incomplete combustion. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses revealed the presence of microspheres, porous granules, and coal residues, with silicon and aluminum oxides dominating the composition (up to 70.49%). Differences in the pollutant potential of ash from different boiler units were identified. Recommendations were substantiated regarding the adjustment of the air–fuel regime, modernization of combustion control systems, and utilization of ASW. The results may be used to develop measures aimed at improving the energy efficiency and environmental safety of coal-fired boiler plants. Full article

The combustion of briquettes made from organic and industrial residues in small boilers requires researchers to consider the characteristics of this type of fuel and methods of its combustion. For the efficient combustion of fuel briquettes, a layered combustion method with the ability to regulate the supply of combustion air is better suited. The purpose of this research is to study the thermal technical conditions of briquetted fuel combustion. In order to carry this out, a stand was created, which made it possible to determine the combustion efficiency of this type of fuel. Two types of briquettes were studied: one with 30% sunflower husks and 70% leaves, and one with and 70% sunflower husks and 30% coke breeze. The combustion results of the briquettes show that heat loss from chemical under-burning was no more than 6.25%. To determine the temperature distribution in the fuel layer, a model of unsteady heat transfer in a fixed layer was used. A calculation of the temperature fields in the layer of burned fuel briquettes was carried out, which showed that the most favorable conditions for burning briquettes were created with a layer about 15–20 cm thick for both burned briquette options. The temperature was in the range of 450–750 °C, which on the one hand corresponds to experimental data and on the other hand provides a combustion regime that occurs with a relatively low loss to the environment. This installation and mathematical model will help future studies based on the processes of other types of organic waste combustion with a grate system. Full article

The constant development of electronic devices and components allows for older systems (which have been well received) with electronic control of combustion processes in municipal thermal energy to be improved to new levels, with significant economic and ecological effects. This article presents details of the development of an improved natural gas combustion quality control system in the modernized DKVR 6.5-13 steam boiler. This paper presents the results of comparative tests of this boiler obtained for various variants of the system operation. It has been proven that maximum boiler efficiency indicators and minimum toxicity of exhaust gases discharged into the atmosphere can be achieved by using a proposed control system. The system uses the regulated residual chemical underburning method, based on simultaneous control of the oxygen and carbon dioxide content in the exhaust gases. As a result of the use of the proposed method, an increase in boiler efficiency was achieved by 1.5–2.1% compared with standard automatic regulation and an increase by 0.3–0.8% compared with regulation based only on the oxygen content in the exhaust gases. These results were achieved by reducing the excess air coefficient. In addition, nitrogen oxide emissions were reduced by 25–30%, which, with a justified safe carbon monoxide content in exhaust gases of up to 250 ppm, reduced the exhaust gas toxicity index to 20%. Full article

Temperature uniformity within a large vertical quenching furnace is the key factor to determine the properties of aluminum workpieces. The existing temperature control method for quenching furnaces cannot overcome the influence of multi-zone coupling issues, which lead to unstable product performance and a lack of key performance. Based on a workpiece temperature field model, a spatial-temporal dimensional extrapolation method is proposed to realize fast and accurate solving of the temperature model. In view of the over-burning and under-burning problems during the temperature rising period, a self-incentive nonparametric adaptive iterative control algorithm is presented, which realizes consistent temperature rising of multiple heating zones. Aiming at the strong coupling problem of the multi-zone heating manner during the temperature holding period, the decoupling problem of multiple control loops is converted into a multi-loop integrated control optimization problem. An eigenvector self-update recurrent neural network (ESRNN) is constructed to determine the Jacobian information and tune the control parameters of each loop controller in real time, thereby realizing the integrated intelligent decoupling control of multiple heating loops. Simulation and industrial results verify the superiority of the proposed method, which can realize high-precision and high-uniformity control of a large-scale temperature field and effectively improve the quality and performance of aluminum alloy workpieces. Full article

Increasing the percentage of recycling of various industrial waste is an important step towards caring for the environment. Coal ash is one of the most large-tonnage wastes, which is formed as a result of the operation of thermal power plants. The aim of this work is to develop a technology for the complex processing of coal ash. The tasks to achieve this aim are to develop a technology for the complex enrichment and separation of coal ash into components, with the possibility of their use in various applications, in particular: processing the aluminosilicate part as a pozzolanic additive to cement; carbon underburning for fuel briquettes; the iron-containing part for metallurgy and fertilizers. Complex enrichment and separation into components of coal ash were carried out according to the author’s technology, which includes six stages: disintegration, flotation, two-stage magnetic separation, grinding, and drying. The aluminosilicate component has a fairly constant granulometric composition with a mode of 13.56 μm, a specific surface area of 1597.2 m²/kg, and a bulk density of 900 kg/m³. The compressive strength for seven and twenty-eight daily samples when Portland cement is replaced by 15% with an aluminosilicate additive, increases to 30–35%. According to the developed technology, high-calorie fuel briquettes are obtained from underburnt with a density of 1000–1200 kg/m³, a calorific value of 19.5–20 MJ/kg, and an ash content of 0.5–1.5%. The iron-containing component, recovered by two-stage magnetic separation, has the potential to be used in metallurgy as a coking additive, in particular for the production of iron and steel. In addition, an effective micro-fertilizer was obtained from the iron-containing component, which: is an excellent source of minerals; improves the quality of acidic soil; helps soil microorganisms decompose organic matter faster, turning it into elements available to plants; promotes rooting of seedlings; helps to more effectively deal with many pests and diseases. As a result, the complete utilization of coal ash in various applications has been achieved. Full article

The main anthropogenic emissions (CO, CO₂, NO_x, SO_x) produced by the processing (combustion) of wastes (coal filter cakes) were measured directly for the first time. The research considered the most widespread coal filter cakes: those of nonbaking, low-caking, coking, flame, and gas coals. These filter cakes are regarded as promising components for the technologies of coal-water slurry (CWS) and coal-water slurry containing petrochemicals (CWSP). According to our estimates, the annual increment of such wastes in the world is as high as 100 million tons. Consequently, the effective utilization of these wastes in the power industry is of high interest. The evaluation of hazardous emissions from the combustion of such wastes shows that filter cakes produce a similar amount of CO and CO₂ as the initially-used coals but filter cakes are more cost-effective. We have established that CWS and CWSP technologies can be used to reduce NO_x and SO_x emissions. To reduce CO and CO₂ emissions when burning filter cakes, we need to switch to low-temperature combustion. Lowering the combustion temperature of filter cakes from 850 °C down to 650 °C decreases the underburning insignificantly while decreasing CO and CO₂ emissions by 30–40%. Full article