A Study On The Pyrolysis Characters Of North Shanbei Coal Carbonization At Lower Temperature

The experimental samples of this thesis are coals produced in Northern Part of Shaan’xi, including coals from Huangling mine, Yan’an Checun mine, Zichang He Caogou mine and Shenmu Hepan mine. The author studies the process of low-rank coal and its product by changing the final temperature of pyrolysis, heating rate and retention time so that the features of the four pyrolysis coals can finally be obtained. The main results are as follows:(1) All the four coals have high volatile matter, fixed carbon, calorific value, N, H and O, and have low ash specification a s well as sulfur content. The four coals can be proved to be low-rank coal through recognizing their functional group with infrared spectroscopy. They can be used as high grade power coal because of their high calorific value.(2)When different coals produced in varied mines are carbonized at lower temperature, their yields are quite different. The tar yields of Yan’an Checun coal is from 5%-7% while that of Huangling is from 11%-13%. Semicoke Calorific value of the four coals are all above 70% and that of Yan’an Checun coal is from 82%-85%. The gas production rates of the four coals are all above 8% and that of Shenmu coal reaches to 13%. Different coals can be carbonized according to the varied needs of tar, semicoke and gas if this experiment is carried out in a real factory.(3)Carbonization temperature has a remarkable influence on yields. When the temperature reaches to 550℃, the tar yields are maximized. Tar yields of Huangling coal and He caogou coal are especially affected by the temperature. However, yields are hardly changed when the heating rate rises. When the retention time come to 40 minutes,the yields of tar, semicoke and gas tend towards stability. So, it is very important to choose a suitable pyrolysis condition to get different products.(4)As the temperature and retention time to extend,The semicoke volatile matter reduce and fixed carbon increases. The increasing heating rate leads to volatile increased slightly and fixed carbon reduction. As the temperature raises, the semicoke calorific value increase.When the temperature reaches 550℃, the semicoke calorific value increased 23.47% than the raw coal. When the retention time reaches 50 minute, the semicoke calorific value increased 28.09% than the raw coal.(5)The semicoke do electron microscope scanning analysis under the condition of high temperature.As the temperature increase,He Caogou semicoke construction become densification and stiffness ingreagually,which have a low reactivity and good for the blast furnace furnace process.