| In recent years,fine particulate matter(PM2.5)and dust in the air have caused frequent smog weather in the country,and environmental pollution has become increasingly serious.Diesel exhaust is one of the main sources of PM2.5.5 and diesel particulate filter?DPF?is the preferred technology to reduce particulate matter?PM?emissions from diesel vehicles.The wall-flow honeycomb ceramic filter is currently the only filter that can be applied to the DPF,and is obtained by cross-blocking the ends of the honeycomb ceramic carrier.SiC and cordierite are the main materials for the preparation of wall-flow honeycomb ceramic filters,but SiC materials have high thermal expansion coefficient and poor thermal stability,which are easy to crack during use.Moreover,the higher sintering temperature?about 2200°C?determines the high production cost of SiC.Cordierite materialhas a low coefficient of thermal expansion(about 0.9×10-6°C-12.5×10-6°C-1),good thermal stability,low sintering temperature?about 1300°C?and low production energy consumption;but cordierite ceramics have high brittleness and low mechanical strength,while compressive strength,open porosity and thermal expansion coefficient are important factors affecting the performance and life of wall-flow honeycomb ceramics.Therefore,how to prepare high compressive strength,high open porosity and low wall-flow cordierite honeycomb ceramics with thermal expansion coefficient has been a hot spot of research.In this paper,industrial cordierite powder is used as the main raw material,and the preparation of wall-flow cordierite honeycomb ceramic filter body is systematically carried out by extrusion molding and extrusion plugging process.The application effect was examined by testing the collection efficiency and pressure drop of the filter.The main findings are as follows:?1?Firstly,the influence of plasticizer content on the extrusion molding effect of mud was investigated by single factor experiment.Then the influence of sintering temperature and holding time on the performance of honeycomb ceramic carrier was investigated by orthogonal experiment.When the plasticizer water,methyl cellulose,glycerin,and ethanol content are 35%,5%,3%,and 6%,respectively,the material has good plasticity,the green ware body is easily extruded and it has a smooth surface and no deformation.The sintering temperature has a great influence on the properties of cordierite honeycomb ceramic carrier.The sintering performance is better when the sample is sintered at 1300°C for 2 h,and the opening ratio is 49.15%,the C-axis compressive strength is 6.75 MPa,the B-axis compressive strength is 1.66 MPa,and when the sintering temperature is higher than 1300°C,the liquid phase formed by alkali metal impurities will significantly reduce the compressive strength of the honeycomb ceramic carrier.?2?The honeycomb ceramic with different content of mullite fiber were prepared by different sintering temperature.The effects of sintering temperature and fiber addition on the reinforcing effect of cordierite honeycomb ceramic were determined by investigating the related properties and compressive strength of porous media.At1300°C and 2 h of heat preservation,the compressive performance of fiber-reinforced honeycomb ceramic carrier is the most significant,the fiber and the substrate are sintered densely,so the mechanical properties are best at 1300°C.When the fiber content is 20%,the opening pore ratio of ceramic is 52.28%,the radial shrinkage is 1.47%,the C-axis compressive strength is 17.92 MPa,the B-axis compressive strength is 3.82 MPa,the C-axis compressive strength is increased by165%compared with the fiber-free one,and the B-axis is increased by 130%.The further increase in the fiber is liable to form floccules to lower the compressive strength of the ceramic.?3?Based on the sample with small shrinkage after sintering in the above study,the formula of?-spodumite plugging material with shrinkage compensation is introduced.By examining the plasticity of the plugging material and whether the plugging material is tightly combined with the honeycomb ceramic carrier or not,the formulation of the plugging material that matches the ceramic body is determined.When the water-powder ratio is 32%,glycerin and ethanol are 2%and 4%,the plugging material is easy to be plugged and the hole wall is not deformed;when the?-spodumene content is 12%,the plugging material and the honeycomb ceramic carrier are tightly combined and the hole blocking effect is the best.?4?Further optimize the thermal expansion coefficient of the honeycomb ceramic carrier by adjusting the pore former content.The influence of this factor on the compressive strength and opening ratio of ceramic carrier was also investigated,and the trapping effect of wall-flow indigo honeycomb ceramic filter was evaluated.When the toner content is 10%,honeycomb ceramic carrier has the lowest average coefficient of thermal expansion?room temperature800°C?1.724×10-6°C-1,at this time,the ceramic opening ratio,shrinkage ratio,C-axis compressive strength,and B-axis compressive strength are:53%,7.7%,11.59 MPa,and 2.08 MPa,respectively.The collection efficiency of the wall-flow type honeycomb ceramic filter in the deep filtration stage increases with the increase of the carbon content content,and is basically maintained at about 98%;The larger the opening ratio of the DPF,the greater the resistance formed by the accumulation of particulate matter in the porous structure,hindering the flow of the exhaust gas stream,resulting in a higher pressure drop across the DPF. |
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