The Influence Of Different Types Sodium Compounds On Gasification Characteristics Of Zhun Dong Coal Under CO₂ Atmosphere

ZhunDong coalfield is China's largest coal field with reserves accounted for about 40% of the total reserves across the country.On one hand,the large sodium content in ZhunDong coal makes it easy to cause slagging and corrosion on heating surface at the fouling in the process of combustion and heat transfer.Sodium, on the other hand, is a highly efficient catalyst, which plays an important role on the activation of oxygen containing functional groups such as carboxyl, hydroxyl and C- C key in coal.It can significantly reduce the ignition point, promote the char gasification of coal, improve the coke burning rate.Different forms of sodium in coal has different effects on pyrolysis and gasification.Also different forms of sodium in coal could transform from one to another when heating. Therefore, the research of sodium's transformation during the process of pyrolysis of ZhunDong coal is very important.In this paper, ZhunDong Wucaiwan coal is selected as research object, by using the methods of extraction, microwave digestion step by step to explore sodium form and content in the ZhunDong coal.Coal is given priority to with water soluble inorganic sodium, which is in the accounts for more than 70% of the sodium content in coal, the accounts for organic sodium follows. With different forms of sodium added to deashing coal, it is found that the form and content of sodium in coal differs from each other after pyrolysis: NaCl and Na₂SO₄ added tar mainly hava sodium in the form of water soluble, NaAc added tar has both water soluble sodium and sodium organic,.When pyrolysis temperature increases over 600?, the sodium in coal begins to release.Isothermal gasification experiment is taken with washed-coal and Na-added coal through thermobalance, we get the following results: the activity of gasification of tar can be improved through water-washing, after acid pickling and deashing treatment, the char gasification activity decreased; With the add of three forms of sodium salt NaCl, NaAc, Na₂SO₄, the gasification reactivity of tar can improve, but the effects are not completely the same. The char gasification reactivity of NaCl added char decreases after increasing with the increase of NaCl's quantity. With the increasing amounts of NaAc, Na₂SO₄,the char gasification reactivity increased before they are stable and the critical concentration is 0.2mol/L.Using gas analyzer to test the gasification product. In order to understand how different sodium salt affact gas generation. The results show that under the same conditions, the load of NaAc coal tar has the highest CO yield, and the gas yield of different Na-added coal all increases with gasification temperature rise.For different sodium salt, the amount of added sodium salt has no significant influence on gasification product.