Migration Of Sulfur During Pyrolysis Of Coking Coal With Organic Sulfur And Bituminous Coal With High Volatile

With the increasing growth of energy consumption, the reserves of coal resources have been gradually exhausted, especially the scarce coals such as coking coal and fat coal. Coal blending is a useful way for efficient utilization of coal sources and it has been used to the steel industry for many years in order to alleviate the pressure of the shortage of high quality coal reslurces. But the stringent requirements of ash and sulfur content restrict the choice of coal types for high quality metallurgical coke.The sulfur in coal mainly exists in the forms of organic and inorganic compounds. Inorganic sulfur can be generally removed by flotation or other physical methods. Organic sulfur is very difficult to be removed and it still only makes a part of sulfur migration by undergoing thermal process. The sulfur content in coke and the use amount of the coking coal may be reduced by blending coal during pyrolysis of coking coal through regulating the migration behaviors of sulfur according to the interactions existing in different kinds of coal samples. Based on this, a coking coal containg high organic sulfur was selected as the main coal and a young bituminous coal with high volatile as well as low sulfur content was used as ingredient. A novel type of two sections and three tubes fixed-bed reacor was used to study the sulfur migration in co-pyrolysis of the two coals. And some conclusions are drawn from the experiments as follows:(1) There exists a remarkable difference of pyrolysis behavior between Coal A with high sulfur coant and Coal B with high volatile matters. The experimental value of the volatile and char yield during pyrolysis of the different proportions blends is different to the calculated value, which indicates there exist synergistic effects between them. The sulfur-containing gases mainly consist of H2S and COS and the main factors influencing them are different. The release of hydrogen containing gases such as H2 and CH4 can promote the formation of H2S. And the release of oxygen containg gases such as CO and CO2 can promote the formation of COS.(2) During temperature programmed pyrolysis, the sulfur distribution with the different proptions of Coal A and Coal B is different. High volatile Coal B can provide enough H-containg radicals to promote the release of sulfur containing radicals to gases when the ratio of Coal A in blending sample is 50%-60%. The reaction between the volatile provided by Coal B and Coal A can reduce the sulfur content in char. Comparing to theoretically calculated value, the sulfur in char can be reduced by 12.4% when the content of Coal A is 50%. When the content of coal A increases to 75%, the content of Coal B is lower and cann’t provide enough H-containing radicals to react with the sulfur radicals in Coal A. Then the sulfur transfer to char or tar. The pyrolysis of Coal A is the dominate reason to cause the sulfur distribution when the content of Coal A is over 75%.(3) During fast pyrolysis, the gasous sulfur increases gradually with the pyrolysis temperatue of Coal A. While the sulfur release of Coal B reaches the maximum at 600℃, then the sulfur in gas decrease slightly with the increase of temperature because of the sulfur fixing effects of inherent minerals in coal. The experimental value of sulfur content in gas during blends pyrolysis is obviously different to the calculated value, which indicates there exist the synergistic effects in this system and they promotes the sulfur migration during fast pyrolysis.(4) The reaction between the volatile of Coal B with the char of Coal A can promote the sulfur in Coal A to release in the gaeous forms during fast pyrolysis But the sulfur content in coke also increases because of the sulfur-containg gases reacting to char A.