ENSURING RELIABLE OF CHIMNEYS WASTE INCINERATORS WITH EXHAUST HEAT RECOVERY SYSTEMS

Abstract

The work is devoted to research on the development and scientific and technical substantiation of measures to ensure anticorrosion protection of solid waste incineration plants chimneys. The reliability, strength, and durability of these chimneys are essential for the uninterrupted operation of the main equipment of these plants. One of the reasons for the chimneys destruction is a deviation from the design mode of their operation, in particular due to condensation on the internal surfaces of these gas exhaust channels. Among the factors that exacerbate non-compliance with the design conditions of chimneys operation is the use of modern heat recovery technologies that lead to a significant decrease in exhaust gas temperature and a decrease in their velocity in the chimneys. The purpose of the work is to develop and investigate the effectiveness of measures to prevent condensation in the chimneys of a waste incineration heating boiler under conditions of using the deep cooling exhaust gas technology. The main objectives of the work were to determine the efficiency indicators of preventing condensation in the chimney when using the method of reducing heat losses from the chimney hull under conditions of its modification by heat insulation or placement of an insertion gas exhaust pipe; to establish the regularity of changes in the main thermal and humidity indicators at the chimney mouth with the specified modifications when using the air method of preventing condensation in gas exhaust ducts. Known thermal calculation methods of heat installations and the results of our own research into heat exchange during deep cooling of exhaust gases of boiler plants were used. The results of research of the main indicators of the thermal and humidity state (dew point t_dp and internal surface temperature t_s at the chimney mouth) under the conditions of using combined heat recovery systems and using the method of reducing heat losses from the chimney hull through the specified modifications are presented. It is shown that this method does not prevent the condensate formation at the mouth of the reinforced concrete chimney in all operating modes of the considered boiler during the heating period. Condensation prevention is only realized at negative ambient temperatures corresponding to high boiler heat loads. The regularities of changes in the studied indicators in the case of the combined use of two thermal methods, namely: a) the air method, which consists in mixing a part σ of the air heated in the heat recovery system with the exhaust gases cooled in the heat recovery system; b) the method of reducing heat losses to the environment (by heat insulation of the chimney hull or installing an insertion gas exhaust pipe in it). Based on the analysis results of the studied indicators, it is shown that using these two methods ensures the safe operation of the considered chimney in all boiler modes. At the same time, the part of mixed air σ does not exceed 5 %, and the heat consumption coefficient g for the implementation of the methods is no higher than 5 % of the volume recovered heat.