Optimization Research On The Boiler's Steam-Air Heater Thermal System

Steam-air heater is a kind of boiler auxiliary equipment that uses steam to heat air .Generally steam-air heater thermal system is composed of the steam-air heater, valves, drain storage tanks, drain pump. When boiler being in start-up condition or in low-load condition, boiler exit gas temperature is low, or in winter the air temperature is low, so it's easy for air preheater having low-temperature corrosion. Steam-air heater's basic function is using steam from turbine to heat boiler inlet air, and then sending the air into air preheater, improving air preheater inlet air temperature, prevent low-temperature corrosion. So steam-air heater for the boiler is necessary, and may also play a role in reducing coal consumption.In this paper there are 6 kinds of steam-air heater thermal system forms, some operate well, some operate badly. So it is necessary to study steam-air heater thermal system, and get the economy, stability, security objectives. this thesis analyses in the following three aspects :(1) Analyzing the existing problems in the operation of steam-air heater, such as leakage, blocking dust, water hammer, and the corresponding solutions; also analyzing the existing problems with examples in the design, calculation of steam-air heater.(2)For the existing 6 typical steam-air heater thermal systems there are some prevalent operational problems, such as the vibration, that makes steam-air heater dose not operate normally. As the environmental temperature is changing, and the boiler is also in different conditions, so steam-air heater system had better be adjustable. These 6 forms of the steam-air heater thermal system on the principle can generally be summed up as the steam-side regulation, drain-side regulation and mixed regulation. But we find that drain-side regulation is better than others, and analyzing the superiority of the drain-side regulation.(3)The main parameters that affect steam-air heater thermal system's operation include steam-air heater outlet air temperature and steam parameters. Parameters analysis is built on the steam-air heater thermal system that can be controlled. On a continent with the heater thermal analysis, prepared by the use of simulation software calculation it's found that when only the heater outlet air temperature is raised or only the steam parameters are decreased, saving of coal increases(under the premise that air preheater's cold-side temperature is the same, increasing boiler inlet air temperature can correspondingly reduce boiler exit gas temperature); to improve when the heater outlet air temperature is raised and at the same time the steam parameters are decreased, saving of coal significantly increases, more than the one when only the heater outlet air temperature is raised or only the steam parameters are decreased. This shows that raising the heater outlet air temperature and at the same time reducing steam parameters, we can get a better operational result for the controlled heater thermal system .Basing on this paper's study and calculation, it's found that the use of the drain-side regulation system that can be controlled, combined with increased heater outlet air temperature, a lower steam parameters will enable the steam-air heater thermal system operate better.