Methodology for determining the flow rate and temperature of generated hot water when calculating the thermal diagram of a hot water boiler room

The consumption and temperature of hot water produced by boiler units are calculated using such a quantity as the consumption of the consumed network water. The formulas represent functional dependencies connecting the obtained values not only with the consumption of heating water, but also with the consumption of hot water supplied for recirculation, for own needs and for the needs of the fuel economy. They take into account the losses of network and hot water. The formulas are obtained as a result of the joint solution of the equation for the total consumption of hot water and the equation for its partial costs.

HARDWARE AND SOFTWARE OF AUTOMATIC CONTROL SYSTEM OF FUEL COMBUSTION PROCESS IN LOW AND MEDIUM POWER BOILERS. PART 2. ALGORITHMIC SOFTWARE

The efficiency of the functioning of boiler units depends on the availability of reliable information on the progress of technological processes. The lack of control and measuring systems for the composition of the exhaust gases leads to low efficiency of the boiler unit, in particular, due to poor-quality fuel combustion. Therefore, in modern operating conditions of boiler units, it is relevant to develop technological solutions focused on finding and minimizing the causes and mechanisms of the formation of harmful substances in exhaust gases. Due to the fact that replacement of outdated boiler units with new ones requires significant capital investments, a promising direction is the modernization of existing boiler units. It is a low-cost and efficient way of rational use of fuel while simultaneously reducing the level of harmful substances in exhaust gases. It remains relevant to ensure the functioning of the control systems for the composition of the air-fuel mixture (AFM) with a given speed and high reliability of maintaining the excess air ratio (EAR) at the stoichiometric level. In the article the high-quality algorithm is proposed for the operation of an automatic control system for the combustion of fuel in boilers of medium and low power by regulating the ratio of the components of the AFM for the burner with feedback according to the signals of the oxygen sensor. The algorithms for the operation of the frequency regulator of the ratio of the components of the AFM in various operating modes are considered. The developed algorithms allowed maintaining the stoichiometric air-fuel ratio in the boiler furnace, reducing the level of toxic emissions into the atmosphere and increasing the boiler efficiency by optimizing the fuel combustion process. The AFM ratio programmer is made in the LM Programmer technical programming environment and works with Windows operating systems (XP, Vista, 7, 8, 10) and oxygen sensors manufactured by Bosch. The visualization of the control process of the fuel combustion process is made in the technical programming environment LogWorks 3 and operates in the environment of Windows operating systems.

EFFECTIVENESS ANALYSIS OF SOFTENING METHODS OF WATER FROM NATURAL SOURCES

The results of chemical analysis of natural waters from surface (river, water supply) and underground (well, well) sources are given. Water selection for analysis was carried out in a number of cities and villages of the Samara and Penza regions. The analysis was performed on the following indicators: total stiff ness, hydrogen index, calcium, magnesium, iron cations, chlorides, sulfates, hydrocarbonates, permanganate oxidability. The most common chemical indicator of water quality exceeding MPC was identifi ed. The negative impact of rigid water on the operation of boiler units and household needs is shown. Various methods of water softening are illuminated. The results of determination of water hardness before softening and after fi ltration through a layer of cationite and anionite are presented. Based on the obtained indicators, recommendations are given on the selection of softening methods for various types of boilers.

EFFECTIVENESS ANALYSIS OF SOFTENING METHODS OF WATER FROM NATURAL SOURCES

The results of chemical analysis of natural waters from surface (river, water supply) and underground (well, well) sources are given. Water selection for analysis was carried out in a number of cities and villages of the Samara and Penza regions. The analysis was performed on the following indicators: total stiff ness, hydrogen index, calcium, magnesium, iron cations, chlorides, sulfates, hydrocarbonates, permanganate oxidability. The most common chemical indicator of water quality exceeding MPC was identifi ed. The negative impact of rigid water on the operation of boiler units and household needs is shown. Various methods of water softening are illuminated. The results of determination of water hardness before softening and after fi ltration through a layer of cationite and anionite are presented. Based on the obtained indicators, recommendations are given on the selection of softening methods for various types of boilers.

USE AND DISPOSAL OF ACIDIC WATER CONDENSATE FROM GAS-FIRED BOILER UNITS

During operation in boiler units of modern condensing boilers or modernization of old-style boilers, water condensate is formed due to heat-recovery equipment in the mode of cooling exhaust-gases below the dew point of water vapor. At natural gas is burned in equipment, the range of values of the pH value of the condensate is within the range of 3 ÷ 6. In this connection, the problem arises of the useful use of this condensate or its safe drainage into the sewer network. At useful use, the resulting condensate can be used for the needs of the boiler units (for washing boilers, in chemical water-purification systems) or outside the boiler house (for laundries, greenhouses, swimming pools, etc.). In the case of condensate drainage into the city sewer network, as a rule, its preliminary decarbonization is required. This is a necessary environmental measure and operational standard to protect the sewer network and related equipment, including treatment facilities, from premature wear. Among the directions of condensate decarbonization known in Ukraine, the most common are: - decarbonization by degassing by the contact method, which consists in removing CO2 from the heated solution by blowing air in the nozzle layer (ceramic or plastic), through which condensate flows. Degassing occurs due to the instability of the H2CO3 compound, which, when heated, easily decomposes into H2O and CO2; - chemical decarbonization, by combining carbon dioxide in an insoluble compound with various reagents, which are added to the container using a dispenser; - decarbonization by passing the condensate through a granular filter containing calcium carbonate, such as marble chips or lime. Removal of carbonic acid from condensate during filtration in a layer of marble chips is seen as the simplest method of decarbonization of water condensate from those considered. On the basis of this method of decarbonization, the authors propose a technical solution for the developed neutralizer with a description of its design and operating principle. The paper presents the results of calculated studies of the volumes of formed condensate and an example of its safe use in the case of modernization of a gas-fired water-heating boiler with a nominal thermal power of 1 MW by a heat-recovery system with simple or complex use of heat. It is shown that when using modern heat-recovery technologies in gas-fired boiler houses, there are different circuit and technical solutions for possible useful use or safe evacuation of acidic condensate formed during the implementation of these technologies. In cases where it is advisable to neutralize this condensate, there are effective methods for its decarbonization and appropriate equipment.

Increasing the Efficiency of the Autothermal Processing of Coal in a Fluidized Bed

The results of work on increasing the efficiency of heat energy production in standard boiler units using the «TERMOKOKS-KS» technology by intensifying the energy-technological processing of coal in a fluidized bed are presented. A significant increase in productivity has been established when removing small grades from coal and subsequent drying of coal, which makes it possible to reduce the cost of the obtained heat energy. The coarsening of the particles of the obtained browncoal coke with a decrease in the moisture content of the coal was revealed, which increases its transport characteristics. The range of temperatures of stable operation of the fluidized bed has been increased, due to which the product range of the «TERMOKOKS-KS» process has been expanded. The heat and material balances of the processes of combined production of heat energy and carbon-containing products are presented

Integrated research of slaging intensityof the boilerunit heating surfaceswhen burning non-project fuels

THE PURPOSE. Comprehensive research of the slagging intensity is the heating surfaces of the BKZ-420-140 boiler unit with solid slag removal at the Abakan CHP when burning non-project fuels. The relevance of the work is due to the technical necessity and economic feasibility of conversion boiler units to combustion of non-design coals. METHODS. The problem has been analyzed by methodology for conducting complex tests, measurements and processing of experimental data, as well as the results of experimental and computational studies of a boiler unit when operating on coals of various qualities. RESULTS. Qualitative and quantitative parameters for assessing the properties of off-design coals and their behavior in real operating conditions of radiation, semi-radiation and convective conditions, taking into account their modes and design functions, have been obtained. CONCLUSION: A computational analysis of the operating modes of boiler units when burning non-design fuels showed that a promising technology for involving non-design coals in the fuel and energy balance of a thermal power plant is providing a scientifically based mixture of design and nondesign fuels.Analysis of the slagging and polluting properties of non-design coals makes it possible to predict changes in the characteristics of the thermal efficiency of heating surfaces and to develop many practical recommendations for optimizing the parameters of the cleaning equipment installed on the boiler.Also, mixtures of fuels were determined for which the wall temperatures of the metal of the outlet stack of the superheater increase, which significantly reduces the strength characteristics of the surface.The assessment and prediction of the reliability of the heating surface is carried out by calculating the temperature of the metal wall in the most heat-stressed place.

Complex Efficiency of Using Wood Pellets in Power Plants

In advanced countries, the dramatic impact of greenhouse gases on the global climate is reduced by replacing fossil fuels with biofuels. This method is being actively encouraged. However, by-products of logging, processing and conversion of wood are classified as difficult to burn fuels due to their high moisture content, low energy density and extremely heterogeneous granulometric composition. A promising direction to increase the energy density and transportability of the timber industry by-products is their granulation. Wood pellet fuel burning in heat-generating plants results in significant increase in their energy and environmental performance. The purpose of the paper is an experimental and calculation study of the energy and environmental performance of 4 MW hot water boilers produced by Polytechnik Luft- und Feuerungstechnik GmbH in the process of burning pine and spruce wood pellets obtained from by-products woodworking. When performing studies, the components of the boiler’s heat balance, gas release, and particulate emissions were determined. Numerical modeling of thermochemical and aerodynamic processes taking place in the boiler combustion chamber was carried out by using the Ansys Fluent three-dimensional simulation software. Together with industrial-operational tests it showed the possibility to reduce the total share of flue gas recirculation into combustion chambers of boiler units to values not exceeding 0.45, in providing an acceptable temperature of combustion products at the combustion chamber outlet and maintaining minimum emissions of carbon and nitrogen monoxides. At the same time, the share of gases fed by recirculation smoke exhausters to the over-bed area of the burner should have higher values than under the reciprocating grates of boilers. Guidelines for comprehensive improvement of wood pellet combustion efficiency in combustion chamber of 4 MW hot water boilers have been developed and implemented. The priorities are: using the air passed through the cooling channels of the setting as secondary air; reducing the rarefaction in the combustion chambers to 30–70 Pa; optimizing the ratio of primary and secondary air, herewith, the share of primary air in the total flow should be 0.26–0.35. Implementation of the developed guidelines allowed to increase the boiler gross efficiency by 0.5–1.8 %, to reduce the aerodynamic resistance of the gas path by 15–20 % and to ensure consistently low emissions of carbon and nitrogen monoxides and soot particles. When designing boiler units for burning wood pellet fuel it is advisable to place heating surfaces in the combustion chamber, included in the circulation circuit of the boiler. This will increase the efficiency and life cycle of the boiler unit.