Study On Preparation Of Cao-rich Briquette From Powdered Semi-coke

The reserve of coal is rich and the distribution is widely in our country,especially the law rank coal,but the reserves of oil and gas are low.Char/coke from fast pyrolysis is a new carbon material which has the advantages of high carbon fixation,high resistivity,low ash,low sulfur and phosphorus.However,the char/coke is generally characterizedas powder state and can't be used effectively which needs to expand its utilization in a value-added manner.Therefore,the powder coke is gradually applied to the production of calcium carbide,ferroalloy,and other products to replace the expensive metallurgical coke in recent years.The quicklime(CaO)and powdered char can be effectively utilized by combination of molding CaO-rich briquetting coke and calcium carbide reaction simultaneously.In the in-situ reaction process of CaO-rich briquetting coke,the mass transfer and reaction rate can be improved,giving low energy consumption and smaller reactor volume on account of high resistance and sufficient contact between semi coke and CaO.Experiments of cold press molding were conducted under a certain pressure after mixing CaO and semi-coke at the weight ratio of 5:3 in the presence of 2?14%binder.The obtained monolith was then carbonized at 850? for 30 minutes.Than test the forming condition and the performance of CaO-rich briquetting coke.The experimental results show that the best molding pressure is 35 MPa and the optimal binder type is aromatic binder 3 with the content of 6%.The grain size distribution of semi coke can affect the strength properties,density,resistivity,porosity of CaO-rich briquette.The compressive strength and density of CaO-rich briquetting coke firstly increase and then decrease as the increase of the ratio of big particle(>0.425 mm).The compressive strength and density could reach optimum when the ratio of big particle(>0.425 mm)is 75%?85%.As for the CaO-rich briquetting coke,the resistivity increased when the proportion of small coke(<0.098 mm)increased.Moreover,the resistivity of CaO-rich briquetting coke is about hundreds of times higher than that of the raw semi coke and the increase in the resistivity could greatly save electricity and energy for the reaction of CaO-rich briquetting coke.The heating rate of carbonization affects the properties of CaO-rich briquetting coke and reducing the heating rate properly can play bonding effect well to improve the strength of the CaO-rich briquetting coke.From the test results of BET we can see that the total pore volume of CaO-rich briquetting coke is small and most of them exist in the form of pore volume and the micropore volume is very small.It must be pointed out that the total pore volume increased several times after carbonization.The microstructure analysis shows that the CaO and binder filled in the larger particle semi coke.The distribution between material particles is uniform and the pore structure is not obvious,but we can see that the distribution between material particles is uneven and a small mesh structure after the treatment of carbonization.The reason is that the binder filled inside the CaO-rich briquetting coke and formed carbon skeleton structure after carbonization and which can improve the consolidation strength of the CaO-rich briquetting coke.