The Influence Of Electrolyte On The Fine Coal Dewatering Under The Action Of Electrochemistry

With the improvement of coal mechanization, the amount of fine coal during the coal procession also increases.At present available filtration techniques are either ineffective or costly for dewatering of fine coal to the desired moisture level of about 20%.Steam coal with high moisture will affect the heat.Cokeing coal with high moisture will bure calories,reduce oven temperature,extended coking time and lower production efficiency.Nevertheless, the excess moisture content will increase transportation costs, reduce calorific value and easily get frozen, which will result in much inconvenience in production.For fine coal dewatering, restricted by investment in equipment, pharmaceutical sources and cost, traditional dewatering methods such as the use of filter, flocculants addition and filter aids etc.still cannot provide a better solution. In order to address the issue of fine coal dewatering, the use of electrochemical method for slurry dewatering has been attached great importance by scientists around the world.Based upon coking coal, anthracite,slightly-caking coal and gas coal in the diameter of-0.5mm, this paper mainly focuses on the electrolyte on the effect of fine coal dewatering.Cake moisture content and the filtration velocity are chosen to investigated.Using the methods of FTIR, TG and so on to characterize some samples and probing from the mechanism, we can draw some conclusions as follows:1. Through the laboratory batch-scale filtration dewatering tests for clean fine coal with electro-chemistry pretreatment method by employing electrode, on the basis of investigating the electrolysis volt, feed concentration and electrolysis time on the influence of dewatering capability, the testing results showed that fine coal upon electro-chemistry pretreatment dewatered easier than that untreated, the process parameters obtained are 20%, electrolyze time 30 minutes, current density 5mA/cm2 and its resulting moisture is 23.53%.The moisture of raw coal is 24.20%,reduced cake moisture content is 0.67%.2.In this paper, the author chose NaCl and Na2CO3.MgCl2 and MgSO4. CaCl2 and Ca(OH)2.AlCl3 and Al2(SO4)3.FeCl3 and Fe2(SO4)3, experimenting different cations effect of different fine coal's electrochemistry dewatering. The result shows that NaCl and Na2CO3 make the moisture content greater, but is bad for dewatering, while MgCl2 and MgSO4, CaCl2 and Ca(OH)2, AlCl3 and A12(SO4)3,FeCl3 and Fe2(SO4)3 are just opposite.The dewatering effect of adding AlCl3 is best. Reduced cake moisture content of coking coal, anthracite, slightly-caking coal and gas coal are 4.00%,2.10%,10.42%,3.22%.3.Adding electrolyte into the slurry can neutralize the surface negative charges and compress the double electrical layer, and so the absolute value ofζ-potential is becoming smaller. The coal surface charge is reduced, subsequently the strong polar functional group is transformed into weak polar functional group to induce to the increase of surface non-polarity.The particle would coagulate in order to facilitate the dewatering of fine coal particles.4.FTIR characterization results show that the fine coal particle surface after electrolysis do not produce new types of functional groups.Each functional group have basically no big change, indicating no change in the nature of coal.-OH,> C=O and-COOH with a negative charge slightly reduced that will reduceζ-potential and low hydrophilic groups,thus speed up the fine coal dewatering.5.Fine coal with a negative charge in electric power to the anode move directionaly, loss electronics in anode board, remove the electrical repulsion, reduce the surface energy, so that fine coal are increasingly to stability, gather the particles, accelerate the fine coal dewatering.