Development of Condensing Low-NOx Gas Boiler Using Can-type Burner and Exchanger

초록

Most of existing gas boilers is Bunsen type burner. They have low-efficiency, because of forced exhaust of high temperature combustion gas, caused by their structure. Also condensing heat exchange is unsuitable because heat exchanger and burner was located respectively up and down. Aa a result, thermal efficiency is around 80% on the basis of higher heating value. Also, the amount of NOx emission of Bunsun burner is abound because the length of Bunsen-burner flame is longer than that of completely premixed flames. This paper describes the major result obtained by researching the process of design and development of the low NOx condensing gas boiler, which is to improve the problem of existing gas boilers, so as to save energy and to reduce environment pollution. The burner and heat exchanger are can-types and the burner is located in the inner-up side of heat exchanger. The heat exchanger was composed of an inner tube and an outer tube. A hot water tube of coil-type was first implements heat exchange inside of an upper heat exchanger, and then, it implements condensing heat exchang inside of a lower heat exchanger. For the purpose of this research, a condensing gas boiler was densigned for the effect to reduction of NOx emission and to implementation of condensing heat exchange. Accordingly premixed surface combustion type was adopted and a heat exchanger was located next to the flame front, so as to lower the temperature of the combustion gas.