Operation Optimization Of A 170t/h Three Gases Co-fired Boiler

In recent years, Chinese steel industry developed rapidly, as the output of steel increased year after year, the production of the accessory gas has also increased year by year. How to recycle these gas and make full use of them has an important significance on heat recovery for the steel industry. BFG(blast furnace gas) is the most unstable, insecure and the lowest calorific value of the three byproducts. Full blast furnace gas boiler often has combustion instability, and has a low efficiency, there will even be severe boiler accident. The paper firstly make a theoretical analysis of the combustion characteristics on low calorific value gas; and introduce methods usually used on gas boiler operation optimization. Then based on problems of combustion, gas blending amount, the instability of the air in the furnace and the other issues that a steel industry whose gas boiler combustion is blended with 170t/h blast furnace gas, coke oven gas and converter gas. Use thermodynamic calculations and numerical simulation to study and got the following conclusions:(1) proposed a fluent model that is suitable for three gas co-firing, and compared the calculated results and the actual boiler operation with the results of thermodynamic calculation, proved the simulation is correct. (2) study the three gas calorific value of 3:4:3,4:3:3,5:3:2,6:2:2 respectively to carry out numerical simulation, analyze four conditions of temperature field, and four kinds of working conditions of economic, get the result that the recommended maximum blast Gas boiler firing rate is 40-50%. (3) changes in the excess air ratio have a great impact on the theoretical combustion temperature, Integrated numerical simulation and the results of thermodynamic calculations derived gas co-firing of the three best gas boiler excess air ratio of 1:1. (4) Preheat gas temperature can help increase the speed of response to meet the combustion than the preheated combustion air temperature. Appropriate adjustments to the air preheater and gas preheater, select 500K as air preheat temperature, gas preheating temperature of 650K as a gas boiler optimization conditions.In this paper, study on the mixed gas fired boiler three dimensional numerical simulation propose a theoretical guidance on the gas boiler operation optimization.