Optimization of low nitrogen burner in cracking furnace

　　Crack b olefine cracking solution furnace INDUSTRY 2018, 30 (4) 53 ~ 56 ETHYLENE cracking furnace INDUSTRY low nitrogen burner optimal operation study Wei Yuee, king fierce (China petroleum & chemical co., LTD., Beijing yanshan branch, Beijing 102500) pick to: application of CBL - Ⅲ type 100 kt cracking furnace low nitrogen after burner, analyzes reasons for NOx emission levels.According to the design condition, working principle and actual operation condition of the low nitrogen burner, the air leakage of the cracking furnace was blocked.By adjusting the fan speed, the opening degree of the air door at the bottom and the side wall, the oxygen content in the flue gas is controlled, the heat field distribution in the furnace is optimized, and the NOx production in the flue gas of the cracking furnace is reduced.Through optimization and adjustment, NOx emission of cracking furnace can meet the national emission requirements under normal operating conditions.At the same time, the influence of oxygen content in flue gas on the formation of NOx and CO was explored, and the optimal range of oxygen content in flue gas was determined.The influence of production load of cracking furnace on NOx generation was analyzed, and the direction of operation adjustment of cracking furnace was put forward after the change of load.Forming low nitrogen burner operation manual to guide the daily operation of cracking furnace.Key words: cracking furnace low nitrogen burner NOx according to gb31571-2015 "emission standards of pollutants from petroleum refining industry", process heating furnace to implement NOx(standard state) 150 mg/m3(furnace temperature greater than 850 ℃ to implement 180 mg/m3) atmospheric pollutant emission limit.The standard also requires the implementation of a special emission limit of NOx(standard condition) of 100 mg/m3 in environmentally sensitive areas.The emission standard is the concentration converted to the benchmark oxygen content of 3%.China petroleum and chemical co., LTD., Beijing branch of yanshan ethylene plant (hereinafter referred to as the yanshan ethylene) have 2 units of 100 kt CBL - Ⅲ cracking furnace (SL - Ⅰ) type, after the Chinese petrochemical technology of CBL is innovated, structure of furnace tube after cracking furnace run smoothly, but normal production conditions, cracking furnace flue gas NOx emissions.In order to meet the national requirements for NOx emission from cracking furnaces, two cracking furnaces were transformed into low-nitrogen burners in 2016.After the low nitrogen burner is put into use, the emission of NOx has been reduced to a certain extent, but the NOx emission (standard state) reaches up to 120 mg/m3, which still cannot meet the environmental emission requirements.In order to make the NOx emission of cracking furnace reach the standard, the operation of cracking furnace was optimized by yanshan ethylene.According to the design condition, working principle and actual operation condition of the low-nitrogen burner, the air leakage area of the cracking furnace is blocked, and the oxygen content in the flue gas is controlled, the heat field distribution in the furnace is adjusted, and the NOx production is reduced by adjusting the fan speed, the opening degree of the air door at the bottom and the side wall, etc.Through optimization and adjustment, NOx emission of cracking furnace can meet the national emission requirements under normal operating conditions.1. Brief introduction of cracking furnace and modification of low nitrogen burner 1.1 introduction of yanshan ethylene cracking furnace 2 sets of CBL - Ⅲ (SL - Ⅰ) type 100 kt cracking furnace, its main raw material for naphtha and hydrocracking tail oil.There are 36 bottom burners and 2 rows of side wall burners in total. The combustion load ratio of bottom/side wall before the modification is 80∶ 20. Air preheater is installed in the bottom burners of the cracking furnace.Before modification, NOx emission index of cracking furnace flue gas is shown in table 1.Table 1 CBL - Ⅲ 100 kt cracking furnace flue gas before modification NOx emissions cracking furnace no. A raw material production load/t. h - (1) the oxygen content, % / NOx (mg · m - 3) BA BA - 113-114 hydrocracking tail oil and 2.Naphtha 40 2.69 122 hydrocracking tail oil 41 3.06 134 naphtha 42 3.Note: NOx index is converted according to 3% of the reference oxygen content.It can be seen from table 1 that before the modification of low-nitrogen burner, NOx emission of cracking furnace flue gas exceeded the standard under different production loads, raw materials and operating conditions.Received date: 2018-04-04;Date of receipt of revised draft: 2018-08-15.Author's brief introduction