Experiment Research Of Co-cracking Coal And Natural Gas For C₂H₂ By Thermal Plasma Jet

This thesis is concerning the acetylene produced through co-cracking coal and natural gas by plasma jet. The plasma jet, which is leaded into a high temperature reactor, is formed by means of arc discharging of nitrogen. At the same time, the coal powder carried by natural gas is leaded into the reactor. Under conditions of oxygen-free, high temperature and normal pressure, coal and natural gas is co-cracked, and converted into the acetylene. The experiments show that the cracking effect of coal and natural gas is not only same as their cracking alone, but also gain some surplus. The surplus probably comes from the interaction of hydrogen and carbon. Here, the hydrogen is come from cracking natural gas and the carbon from coal. The thesis consists of three parts. In the first part, the research status of acetylene produced by coal or natural gas is estimated and summarized in detail. There are partial oxidation cracking, arc cracking process and water to carbide process which have been industrialized, and emphases give to the actual acetylene preparation through pyrolysis coal alone and pyrolysis natural gas alone by thermal plasma. The advantage and scarcity of those technics are got by comparison. A special notice is paid to that during cracking natural gas by thermal plasma, one not only can gain acetylene, but also hydrogen. Generally speaking, the hydrogen can further react with the carbon in coal. Therefore, co-cracking coal and natural gas will gain more products, and reduce specific energy. The second of all, some key questions of co-cracking technics are investigated. By use of thermodynamic equilibrium and energy-balance equation we get the degree of dissociation of nitrogen plasma and the relation of temperature depend on arc power and working gas flux. At typical conditions of power: 15 KW , working gas flux: 2 Nm 3 /hr , by calculation the degree of dissociation of nitrogen plasma is 20%, velocity and temperature at the exit of plasma generator is 63.3 m /s and 5000K, respectively. Cokeability is always the pivotal question of plasma technics. By use of the heat transfer model of multi layers cylinder, the thermal insulation reactor is designed. It is calculated that the temperature at the reactor inwall can reach 2000K and the temperature gradient is low. The functions of this reactor are confirmed by experiment, and weaken the cokeability effectively. Feeder and air delivery is designed by the drum feeder theory and the air delivery principle. The separate control of the coal quantity and the carried gas'flux are realized. The experiment requests are satisfied and the fluidization of coal powder is improved. The third is the experiment. The co-cracking of natural gas and coal by 15KW of nitrogen (N2 flux: 2 m 3/hr ) thermal plasma jet was investigated experimentally. For comparing with the cracking alone natural gas or coal, the experiments was arranged as following: â…°. Cracking of natural gas; â…±.Cracking of coal; â…². Co-cracking of natural gas and coal. At the same experimental conditions, especially the same power, the experiments show that co-cracking can gain more output of acetylene and ethylene, even 1~5% more than the summation of that from â…°a nd â…±. The analysis shows, during the co-cracking, the natural gas and the coal both gain the effect of its cracking alone; the surplus probably come from the interaction of hydrogen and carbon. Here, the hydrogen is come from cracking natural gas and the carbon from coal. The specific energy of co-cracking reduced 33~40% less than cracking natural gas, and reduced 60~72% less than cracking coal.