Improving the environmental friendliness of a solid fuel boiler house using SHF energy

To reduce harmful emissions, solid fuel consumption and increase the efficiency of the boiler plant, an automated system with a combined heating device and a condensing air heater connected in series was designed. In a combined heating device (SHF + flue gases) equipped with a magnetron, quality control and additional preparation of solid fuel with a high moisture content (up to 80%) for combustion are carried out. In the condensing air heater, the heat of the flue gases coming into it from the combined heating deviceand the latent heat of vaporization are extracted. The use of this system allows reducing the moisture content and temperature of flue gases, the volume of harmful emissions from the boiler plant in the form of nitrogen oxides and dioxides (NOx), carbon oxides (CO), ash, volatile coke residues. By increasing the volume and reducing the corrosiveness of the condensate formed from the flue gases in the condensation air heater during the drying process of fuel with a high moisture content, it can be subsequently used as process and make-up water. Practical application of the system makes it possible to reduce the cost of generating heat energy by the boiler house by increasing the use of low-calorie fuel with a high moisture content in the form of waste from logging, wood processing, low-grade coal and peat, which also has a positive environmental effect.

Microwave solid fuel ignition

The article continues the study of the effect of microwave exposure on solid fuel. On the basis of the experimental studies, the dependences of changes in the temperature and humidity fields of the fuel on the time of microwave exposure, to arson, have been established. The possibility of using the microwave electromagnetic field to automate the process of burning solid fuel in a boiler plant, afterburning unburned fuel residues is considered. The mechanism and basic conditions of these processes are presented. The influence of this technology on the intensification of the fuel ignition process, its homogenization, an increase in energy characteristics and a change in the elemental composition, an increase in the efficiency of a boiler plant, a decrease in chemical, mechanical underburning and harmful emissions of a boiler plant is considered. The main conditions of the applied technology are: placement of the microwave generator on the combustion device of the boiler unit, the size of the solid fuel samples or its contacting pieces should be less than the wavelength of the microwave electromagnetic field (12.4 cm), the moisture content - within the range from 10 to 95%. The intensification of the process of burning solid fuel also depends on the type of fuel, its physical and chemical properties (various types of coal, wood fuel, including wood waste, peat, and others). Modernization of boiler plants using this technology is possible by unifying projects that take into account the correspondence of microwave generators to the thermal power of boiler units.

Prevention of condensation in chimneys of boiler plants with heat-recovery systems

The results of studies of the effectiveness of using the air method of preventing condensation formation in the gas-exhaust ducts for anticorrosive protection of chimneys of gas-fired heating boiler plants are presented. This method is used in heat-recovery systems of boiler plants, characterized by deep cooling of gases (below the dew point temperature of water vapor contained in exhaust-gases). The essence of this method is to change the thermal and humidity characteristics of exhaust-gases after heat-recovery by mixing dry and heated air in front of the chimney. Schematic solutions of heat-recovery systems using two options for using the air method are presented. The first option corresponds to the use of the air method when mixing air from the heater of boiler plant. In the second option, for the implementation of the air method, air heated in the heat-recovery system itself is used. To assess the efficiency of the air method, computational studies were carried out to determine the thermal and moisture characteristics of flue gases at the mouth of different types of chimneys under different operating modes of the boiler during the heating period. The studies were carried out for two proposed options for using the air method when using air with a change in its temperature over a wide range. The values of the dew point of the flue gases at the mouth of the chimney and the temperature of its inner surface were calculated at various proportions of the mixed air. The parameters of flue gases and mixed air were determined, ensuring the absence of condensation in the chimneys. Based on the values of the obtained parameters, a comparative analysis of the effectiveness of the considered options for using the air method was carried out. It is shown that for heating boilers the use of this method is the most effective in complex heat-recovery systems when using recovered heat for heating return heat-network water and combustion air. Key words: gas-fired boilers, exhaust-gases, deep cooling, air method, thermal and humidity condition, chimney, anticorrosive protection

The Cost-Efficiency Analysis of a System for Improving Fine-Coal Combustion Efficiency of Power Plant Boilers

Hard coal is widely used as a source of energy, and a number of catalysts have been developed to minimize the noxious impact of this fuel on combustion. This paper presents the cost-efficiency analysis of a system for improving the combustion of solid fuels, especially fine coal, in power boilers. The system is provided with a control and supervision device. It has been designed for better accuracy in controlling the boiler operating parameters, with a view to improving combustion efficiency due to the use of catalysts. The tests were carried out for system capacities ranging from 3 to 100 MW. It was found that, depending on the size of the system in the range of 3–100 MW, savings in the fuel consumption ranged from 2% to 8% due to the implementation of novel solutions in the boiler plant operation and from 2 to 6% due to the use of the combustion catalysts. Apart from boosting energy efficiency, the use of catalysts and the efficiency-boosting system resulted in the costs of overhauls being cut by about 20%. The payback time depends on system capacities, and it is between 6.75 and 1.74 years for capacities ranging from 3 to 75 MW and 2.0 years for a 100 MW plant.

Experimental Study of a Coil Type Steam Boiler Operated on an Oil Field in the Subarctic Continental Climate

Transportable boiler plants are widespread in the northern regions of the Russian Federation and have a large and stable demand in various spheres of life. The equipment used and the schemes of existing boiler plants are outdated—they require replacement and modernization. Our proposed new installation includes a coil type steam boiler and ancillary equipment designed with the identified deficiencies in mind. The steam boiler coils are coaxial cylinders. The scope of the modernized transportable boiler plant is an oil field in the subarctic continental climate. The work is aimed at completing an experimental and theoretical study of the operation of a coil type steam boilers under real operating conditions. Experimental data on the operation of boiler plants are presented. The dependences of the fuel consumption of boiler plants on the temperature and pressure of the coolant are obtained. Statistical analysis is applied to the collected data. Conclusions are formulated and a promising direction is laid out for further research and improvement of coil type steam boilers. Equations are proposed for calculating the convective component of radiant-convective heat transfer in gas ducts, taking into account the design features of boiler units by introducing new correction factors. Comparison of the calculated and experimental data showed their satisfactory agreement.