高炉喷吹用煤燃烧过程中氯的析出特性

Chlorine precipitation characteristics during the combustion process of pulverized coal injection used in blast furnace

高炉喷吹用煤在低温燃烧和风口条件下高温快速燃烧过程中氯元素的析出特性差别很大。为对比其差别,对煤燃烧过程中氯的析出机理进行了热力学分析,并试验研究了高炉喷吹用煤低温燃烧过程中氯的析出特性,分析了温度、时间和空气流量对其影响规律。结果表明,低温燃烧条件下,高炉喷吹用煤氯的析出率受温度影响显著。在300~600℃内随温度上升,氯的析出率迅速增加,600℃时,氯析出率高达90%。继续升温至800℃以上时,氯析出率有所减缓;随燃烧时间的延长,煤中氯析出率增大;在500~700℃固定温度下,煤粉燃烧过程中氯的析出属于零级反应,其析出的表观活化能Ea为6 691.1 k J/mol、频率因子k0=3.562;氯的析出率随空气流量的增加缓慢增加。高炉喷吹用煤粉在风口高温快速燃烧时氯的析出率仅在50%左右,远低于其在低温燃烧时氯的析出率。煤粉在高炉中燃烧时部分氯元素滞留在未燃煤粉中,故高炉生产建立煤粉中氯元素检测制度,并使用低氯煤进行喷吹。

The precipitation characteristics of chlorine in pulverized coal injection( PCI) of blast furnace at low temperature combustion are different from that at high temperature combustion in tuyere of blast furnace. Initally,the thermodynamics analysis about chlorine precipitation mechanism of coal was conducted,and then the precipitation characteristics of chlorine in PCI of blast furnace at low temperature combustion were studied in order to find the difference of chlorine precipitation rate at low temperature and high temperature combustion conditions. Also,the influences of temperature,time and air flow on chlorine precipitation were analyzed in details. The results show that the temperature has significant effect on the precipitation rate of chlorine under the conditions of low temperature. With the temperature increasing from 300- 600 ℃,the precipitation rate of chlorine increased rapidly. The precipitation rate of chlorine is up to 90% at 600 ℃. When the temperature rises beyond 800 ℃,the increase of precipitation rate of chlorine becomesslowly. With the prolongation of burning time,the precipitation rate of chlorine increases. The chlorine precipitation process of coal combustion process belongs to zero order reaction at 500- 700 ℃. Ea and k0 of chlorine precipitation is6 691. 1 k J / mol and 3. 562 respectively. The precipitation rate of chloride enhances slowly with the increase of air flow. At the tuyere combustion conditions of blast furnace,the precipitation rate of chlorine is only about 50%,lower than that at low temperature combustion conditions. Fraction of chlorine element in coal will be resident in the unburned coal when the PCI combusts in the blast furnace. Therefore,the chlorine check system of PCI should be established in the blast furnace production site.