Byutilizing the residual gas and exhaust temperature in exhaust gas, pollutantssuch as CO, HC and NOx are converted into harmless CO2, N2 and H2O throughcatalytic effect, which meets the emission standards of National V, NationalVI, Euro V and Euro VI of lightweight vehicles；As thetightly coupled catalyst is located close to the engine exhaust outlet, itenables the conversion of CO, HC and rapid increase of exhaust temperaturethrough low temperature ignition under cold start condition；Chassiscatalyst delivers effective purification of CO, HC and NOx over a wide air-fuelratio window.Performance CharacteristicsCoating is stable, with excellent airvelocity adaptability；Good resistanceto high-temperature hydrothermal aging and to sulfur poisoning with longservice life；The tightlycoupled catalyst has good cold start performance and higher hydrothermalstability at high temperature.

Ceramic filters are more and more widely used in many industrial fields, such as catalytic noble metal recovery, fluidized bed combustion, calcination, organic waste gasification power generation, building materials, chemical and various industrial kiln, furnace and other industrial processes of high temperature flue gas purification. The application of high temperature flue gas purification will also appear in smelting, material production and glass manufacturing. These high temperature soot purification is usually carried out under the condition of close to atmospheric pressure.The most prominent application of ceramic filters is soot purification in the field of coal-fired power generation. Because of the increasing demand for electric power worldwide, coal is the main source of electricity. For the non-renewable nature of this fossil fuel, maximizing the efficiency of power generation and reducing the pollution to the atmosphere has become a major task for countries around the world, especially China, a big coal-burning country. Circulating fluidized bed (CFBC) power generation, coal gasification (IGCC) power generation, and combined power generation can achieve the purpose of improving power generation efficiency. Coal gasification power generation is different from the traditional steam engine power generation process. After the coal is heated and vaporized, the gas needs to be purified before it enters the gas-fired generator (gas turbine). That is, any dust or other impurities must be removed. Most power plants limit the allowable dust concentration into the gas turbine to less than 5 mg/m3. Ideally below 1 mg/m3 in theory. The operating temperature of the dust removal system is often 350 ~ 1000℃, and the pressure is 1 ~ 2.5 SPa. Therefore, to achieve such a high purification effect under such high temperature and high pressure, ceramic filter will inevitably become the first choice.

The research of ceramic filter mainly focuses on two aspects: one is the material of ceramic filter, including the manufacturing process and performance of ceramic filter; The second is the structure of the ceramic filter, including the shape of the filter, placement position, filtering mechanism and filtering effect.The filter material should be selected according to the type of inclusions to be removed by filtration, and the creep resistance and thermal vibration resistance of the material should also be considered. A large number of experimental results show that material, porosity and inner surface roughness of ceramic filter affect the filtration effect. The structure of ceramic filter is determined by its material. According to the different material, ceramic filter can be divided into foam ceramic filter and particle ceramic filter.Ceramic foam filters have an open volume of 75% to 90% and are usually classified by PPI per inch of line. For example, 10 PPI ceramic foam filter, its pore size is 1778 μm, the range is 584 ~ 3708 μm; The pore size of the 30 PPI ceramic foam filter is 711 μm, ranging from 229 μm to 1422 μm. The thickness of the ceramic foam filter is generally 25 mm. In the pouring system, there are upright and horizontal placement, and its structure is designed according to the specific situation of use.Ceramic foam filter has been selected material NCL-MulLite, ZrO2, ZR-SiO4 and Al2O3. The use of Al2O3 foam ceramic, in the operation is not fragile, its thermal vibration cracking performance is good, at 1700℃ high temperature liquid metal flow, anti-creep deformation ability is strong. Because of the high porosity of the pores (75% to 90%) and the thin walls of the pores, the foam ceramic filter does not need to be preheated before coming into contact with the liquid metal.The structure of the particle ceramic filter is a support plate with holes up and down, and the middle is a particle filler, on which a layer of active adsorption material is plated. The thickness of the support plate is generally 12 mm, and the hole diameter is 4.5 ~ 13 mm. MgO or Al2O3 is selected as filler for granular ceramic filter, and active adsorbent is selected according to the type of inclusions to be filtered. For the superalloy treated with rare earth metal, the rare earth metal is selected as the activator, and the waterproof problem should be solved when using calcium oxide particles.CaO refractory is a good filler material for granular ceramic filters, which can not only rely on the principle of physical adsorption, but also can remove inclusions through chemical reactions. However, there are two reasons that limit its extensive application. First, it requires extremely high sintering temperatures (above 1800℃) to obtain the required density and mechanical strength. Second, it is easy to hydrate at room temperature and atmosphere.The advantages of CaO refractoriness are high refractoriness, high alkalinity, good filterability of liquid steel and abundant resources. The way to improve the hydration resistance of CaO refractory for liquid steel filtration is to improve the sintering degree of CaO refractory, large crystal size, using ultra-high calcination or electromelting lime; A protective film is formed on the surface of CaO; Tar or organic resin film is soaked on Cao-fired products as an intermediate transition measure; The effect of adding a small amount of chemical additives in CaO is to reduce the sintering temperature of CaO, and to produce part of liquid phase in the sintered body at the later stage of sintering, so as to promote the growth of CaO grains.

Solids collected by CERAMIC filters accumulate outside or inside the FILTER layer, blocking the pores in the filter and reducing the filtration capacity. This clogging state can take several forms, such as surface collection of solids; Solids enter the inner layer of the filter; There is also the accumulation of solids on the surface to form a rough surface layer (like a filter layer). In these cases, although the filtration capacity gradually decreases, the degree of decline is not the same. [2]Strength is one of the most important characteristics of ceramic filters because they are subjected to internal pressure, external pressure, compression and tension. In addition, when used at high temperature (700 ~ 1000℃), the filter does not cause softening and strength reduction after heating is a very important characteristic. Although the strength is affected by many factors such as aggregate quality, aggregate particle size, binder quality and mixing ratio, it is mainly related to aggregate strength and bonding layer strength.Although the strength of the bonding layer mainly depends on the binder and firing conditions (temperature and atmosphere), it is also important to adjust the thermal expansion coefficient of the binder and the bone (aggregate) material to ensure the bonding force of the binder and aggregate (i.e. the thermal expansion coefficient and bonding force are also important factors affecting the strength of the bonding layer).Ceramic filters usually have excellent acid resistance and are stable to all acids except fluoric acid at high temperatures. The acid resistance is affected by binder fit, firing condition, aggregate quality and other factors. In order to obtain a filter with excellent alkaline and vapor resistance, specially formulated binders are needed. Carbonaceous filter has excellent alkaline resistance.In the precision filtration occasion (as a special case), in order to prevent contamination of liquid, do not allow trace dissolved matter, the use of ceramic filter, usually no dissolved matter, and according to the food hygiene law to test, is also qualified, so can be used in the field of poultry industryAlthough ceramic filters can be used for other porous bodies can not reach the high temperature area, but in the filter combustion waste gas, molten metal, and in the gas blown into the high temperature furnace nozzle, it is best used in the high temperature area below 1000℃. In order to adapt to higher temperature zones, filters with very little binder and aggregates self-binding to each other are considered. In the high temperature region of 700 ~ 1000℃, the silicon carbide ceramic filter with excellent thermal shock resistance shows good effect. The second is alumina ceramic filter.In this paper, the thermal shock resistance of ceramic filter is discussed by using silicon carbide ceramic filter. When the fluid is a gas, from the shape of the product, the temperature difference can be up to 400 ~ 700℃. Alumina ceramic filter can withstand temperature difference up to 300 ~ 400℃. The high thermal shock resistance of this filter is due to the porous nature of the ceramic, which can absorb thermal deformation.

Filtration characteristics of the most important is the dust collection efficiency, followed by filtration capacity, pore blockage, etc.For clean fluid, the fluid permeability through the ceramic filter layer is proportional to the area and pressure difference, and inversely proportional to the plate thickness and viscosity coefficient. The filter layer is regarded as a collection of capillaries, and the fluid flow through the capillary can be expressed as follows:V = (π· D4 · δP)/(128η· L) = (π· D4 · δP)/(128α·η·L)In addition, the relationship between the gas penetration rate ε and the number of capillaries per unit area N and the capillary diameter D can be expressed as follows:ε= (π/4) d2·NThus, the permeability V can be expressed as follows:V=N· V= (d2·ε· δP)/(32α·η·L)Where V -- permeability per unit area per unit time (cm 3/ cm 2· second);δP -- pressure difference (dyne/cm 2);η -- viscosity coefficient (dyne · SEC/cm 2);L -- thickness of filter (filter) layer (cm);D -- capillary diameter (cm);L -- capillary length (cm);α -- bending degree (1 ~ 3).The amount of fluid permeating through the ceramic filter layer is proportional to the porosity of the filter and the square of the capillary diameter. Increase the amount of binder, expand the distribution range of particle diameter, so that the porosity ε decreased, the fluid permeability decreased, therefore, the amount of binder and particle diameter distribution should be used as the manufacturing conditions of the filter. The porosity of the ceramic filter is 33±2%. Although the permeability can be increased by decreasing the thickness and increasing the diameter of the pore, the dust collection efficiency is decreased. In addition, the intensity and other factors should be considered, and then various conditions should be selected.

The ceramic filter is composed of a porous body with two end faces and a peripheral face separated from the next to form a plurality of main flow paths of the purified fluid from one end face to the other end face and a filter membrane arranged on the inner surface of the main flow path. Through a transverse lateral opening into the mainstream way, be purged of fluid through porous membranes and plastid inside to purification, and as a cleaning fluid was removed from the outer surface of porous plasmids, or through the outer surface of porous plastid inflow, purified of fluid through porous plastid inside for purification and filtration membrane, And is removed as a purifying fluid from at least one end face side opening of the main flow path.Ceramic filter is a kind of filter widely used, it uses rigid microporous material as filter element. It includes ceramic, corundum, silicon carbide, sand chip and a series of filters. Because OF too LARGE AIRFLOW CAN MAKE dust adhere to the filter, causing blockage, in order to prevent too large airflow directly blowing ceramic cup, so in the outside of the ceramic cup plus a protective cover, so that the airflow around the lower part of the filter, and then into the filter. In order to reduce the invalid volume, the bottom of the filter is tapered and a splitter is added. On the one hand, it blows the dust away; On the other hand, due to the constant flow of gas, the gas exchange is accelerated and the lag time is reduced. A ceramic filter system is designed to facilitate the replacement and cleaning of the filter. When a filter is blocked, two four-way directional valves can be turned to pass the sample gas into another filter, and the blocked filter can be blown back through high-pressure air, so that the dust attached to the ceramic filter cup is removed. The two filters work in rotation. It is suitable for more important analytical systems as well as sampling systems with high dust content which are prone to blockage.