INCREASE THE EFFICIENCY OF COMPLEX HEAT-RECOVERY SYSTEMS FOR HEATING AND HUMIDIFYING OF BLOWN AIR OF GAS-FIRED BOILERS

Abstract

The work is devoted to increase of thermal and ecological efficiency of water-heating gas-fired boilers of municipal heat-power engineering. To improve thermal efficiency, heat-recovery technologies are used in which deep cooling of the exhaust-gases from boilers with the realization of the condensation mode of the heat recovery equipment is ensured. To implement this regime throughout the heating period, it is advisable to use complex heat-recovery systems in which several heat transfer agents are heated with sufficiently different thermal potentials. To enhance the environmental effect when using complex systems, it is possible to carry out combustion air humidifying in them, which contributes to the reduction of NOx emissions to the environment by the boiler plants. The work suggests improvement of the known complex heat-recovery system for heating and humidifying the blown air by introducing into its comprise an additional element - water heater of chemical water-purification system. Such the technological solution will ensure a reduction in the thermal losses of the boiler plant and improve the operating conditions of the gas ducts of the boiler house by preventing the condensate from falling out of the wet exhaust-gases. The aim of the work is to investigate the operating parameters of the complex heat-recovery system for heating and humidifying the blown air and preheating the water for chemical water-purification and comparing its basic heatly and humidity characteristics with the corresponding complex system without preheating the water. The results of the investigations are presented in a wide operating range of the load variation of the water-heating boiler respectively the boiler plant temperature graph and are shown graphically. The analysis of the obtained data showed that due to the proposed modernization by preheating the water of the chemical water-purification system in the complex heat-recovery system for heating and humidifying the blown air, an increase of coefficient the use heat of fuel of boilers is provided, depending on their load from 11% to 17%. For this improved heat-recovery system with preheating the water of the chemical water-purification system in comparison with the system without such preheating, the total heating capacity of the complex system increases by 1.3÷1.6 times, and the coefficient the use heat of fuel of the boiler  increases by 5.2%.