Study On Coal Water Mixture Concentration Technology By The Cross-flow Filtration Device

The main energy source of China is coal as a few countries in the world. The emergence of coal water mixture(CWM) is an important part of clean coal technology in China, because it can effectively improve the utilization rate of coal and reduce the emission of pollution. The long distance pipeline transportation of CWM is a new kind of transportation method which it has been paid attention, because it has many advantages, such as saving energy, large amount of transportation, no environment pollution, easy operation and management. There is a concentration difference between Water coal mixture pipeline transportation(about 50%) and terminal gasification(65% to 70%), therefore it needs to be concentrated before the gasification terminal. But the concentration cannot work for the CWM added about 1% of the dispersion agent and stabilizer, which lead gravity concentration, frame filter press method to be ineffective. So it need a new type of concentration technology, this concentration technology is different from the past treatment goal “as far as possible to achieve solid-liquid separation”, but to make a certain degree of concentration regulation.In this study, NaCl, CaCl2, Al2(SO4)3 and PAC are used to adjust the dewatering performance of CWM. The changes of dewatering rate were detected by vacuum filtration test and the suitable agent is selected. Then, measure Zeta potential, particle size, viscosity and dynamic stability of conditioning PAC and select the suitable dosage. The last, design the cross-flow filtration device, compare the filter performance of plain polypropylene fabric, geotextile separation and twill polypropylene fabric, and detect the stability and feasibility of cross-flow filtration device. It can be concluded as follow:The concentration of CWM is 52%. Different dosages of NaCl, CaCl2, Al2(SO4)3 and PAC are added into CWM and detect their dewatering rate. The results show that every kind of agents can improve the dewatering performance of CWM. In order to increase CWM concentration from 52% to 65%, it required dosage of four pesticides is NaCl>CaCl2>Al2(SO4)3> PAC.Add different dosages of PAC into CWM and measure their Zeta potential, particle size, viscosity and dynamic stability. Results shows that the PAC dosage under 0.02% has little change in physical and chemical properties of CWM, which meets the requirement of pipeline transportation. So PAC dosage should not exceed 0.02%.TG- DTA method is used to study the changes in CWM water distribution after adding PAC. The results showed that the addition of PAC can increase the free water content while reduce the middle water content. The increasing of free water content is benefit for filtering, so PAC can improve the dewatering rate.The designed cross-flow filtration device can effectively concentrate CWM from 52% to 65%. Compared to three kinds of cloth, plain weave polypropylene fabric filter works best. When the backwash time is 40 s, backwash water volume is 5 L, the device can run multiple cycles stably.