Honeycomb ceramic is a new type of ceramic product with a honeycomb-like structure. It is widely used in chemical, electric power, metallurgy, petroleum, electronic appliances, machinery and other industries from the earliest use in small automobile exhaust purification, and it is becoming more and more extensive, and its development prospects are considerable. Honeycomb ceramics are composed of numerous and equal pores in various shapes. The maximum number of pores has reached 120 to 140 per square centimeter, the density is 0.3 to 0.6 grams per cubic centimeter, and the water absorption rate is as high as 20%. Due to the characteristics of porous thin wall, the geometric surface area of the carrier is greatly increased and the thermal shock resistance performance is improved. The meshed pores of the produced products are mainly triangular and square. These are especially important as catalytic supports. With the increase of the number of pores per unit area and the decrease of the thickness of the carrier hole wall, the thermal shock resistance of the ceramic carrier increases, and the temperature of thermal shock damage also increases. Therefore, the honeycomb ceramic must reduce the expansion coefficient and increase the pore size per unit area. number. The thermal expansion coefficient is the main performance index. The current foreign level is α25-800℃≤1.0×10-6℃-1, which has a certain gap with the domestic comparison, but the gap is getting smaller and smaller. The earliest raw materials for the production of honeycomb ceramics are mainly kaolin, talc, aluminum powder, clay, etc., especially the application of diatomite, zeolite, expansive soil and refractory materials.
Honeycomb ceramics are more advantageous in catalysts. The honeycomb ceramic material is used as the carrier, and the unique coating material is used to prepare the precious metal, rare earth metal and transition metal, so it has the advantages of high catalytic activity, good thermal stability, long service life, high strength and so on. Honeycomb ceramics for catalytic cracking are replacing existing products. Catalytic cracking uses heavy distillate oil between 200 ~ 500 ℃ as raw material (including vacuum distillate, straight-run light diesel oil, coking wax oil, etc.), uses aluminosilicate as catalyst, and the reaction temperature is between 450 ~ 550 ℃ ( varies by reactor type). It has a large output (each large-scale catalytic cracking unit cracks more than one million tons of oil products per year), and requires high technical conditions (for example, the catalyst needs to be regenerated every few minutes or even seconds when it contacts the oil, and the fluidized bed catalyst flows through the fluidized bed catalyst every minute. Up to 10t or more) With the improvement of catalytic activity, in order to speed up the regeneration, more severe regeneration conditions are required. For example, at 600 to 650 °C, or even 700 °C, the consumption of catalyst is large, and each ton of feed oil consumes 0.3 to 0.6 kg of catalyst. If the mechanical strength of the catalyst is poor, the consumption is much larger. This requires a slight improvement in catalyst activity, selectivity, and stability, which will be of great significance to actual production. Because of this, honeycomb ceramic catalysts are constantly innovating, and the market demand is also increasing. These catalysts for catalytic cracking are replaced by honeycomb ceramic catalysts. Honeycomb ceramic catalysts with large size and number of pores have emerged and have a strong development momentum.
A catalytic converter is part of a car's exhaust system. Catalytic conversion device is an exhaust purification device that converts CO, HC, and NOx in exhaust gas into gases that are harmless to human body by using the action of catalyst, also known as catalytic conversion device. The catalytic conversion device converts the three harmful gases CO, HC, and NOx in the exhaust gas into harmless gases carbon dioxide, nitrogen, Hydrogen and water. According to the purification form of catalytic converter, it can be divided into oxidation catalytic converter, reduction catalytic converter and three-way catalytic converter. The ceramic carrier is also a key component of the catalytic converter. One of its important materials is cordierite, which is resistant to high temperature, with a maximum continuous working temperature of 1200 °C, high strength and low coefficient of linear expansion. The carrier adopts an effective surface and a suitable pore structure. The opening rate of the domestic ceramic carrier can reach 400-460 mesh/inch2, and the minimum wall thickness can reach about 0.16mm. It can enhance the mechanical strength of the catalyst, as well as its ability to resist wear, impact, gravity, compression, high temperature, and phase change, improve the conductivity of the catalyst, and reduce the content of active components. Especially when using precious metal catalysts platinum, palladium and rhodium, the active components can be highly dispersed and the dosage can be reduced. In conclusion, the quality of the carrier is extremely important for the catalyst.
The urea pump is an important part of the urea solution injection metering system. Its main function is to extract the urea solution in the urea tank, maintain a certain pressure, and then deliver it to the injection unit to meet the requirements of the injection metering system for flow and pressure. As an important means of controlling diesel engine exhaust emissions, it has been widely used in developed countries such as Europe, and has played a significant role in improving the environmental pollution caused by exhaust emissions. After using SCR technology, the emission performance of the engine depends to a large extent on the calibration of the urea injection system and the related performance of the urea pump. Based on the basic principle of nitrogen and oxygen reduction, the SCR device uses a 32.5% urea aqueous solution as a reducing agent to reduce NOX in the exhaust gas to N2 and H2O under the catalytic action of the catalyst surface coating. The exhaust temperature of the diesel engine is generally 200-500 °C, which basically meets the activity requirements of the vanadium-based catalyst used in SCR. Therefore, the NOX in the exhaust gas discharged from the diesel engine quickly reacts with the urea aqueous solution to generate nitrogen and water. The urea dosing pump is the core component of the SCR system, and its performance is closely related to the emission function of the engine. In order to ensure that the working reliability of the urea dosing pump meets the working requirements of the SCR system, the urea dosing pump needs to be calibrated.
A nitrogen oxygen sensor or NOx sensor is typically a high-temperature device built to detect nitrogen oxides in combustion environments such as an automobile, truck tailpipe or smokestack. The drive to develop a NOx sensor arises from environmental factors. NOx gases can cause various problems such as smog and acid rain. Many governments around the world have passed laws to limit their emissions (along with other combustion gases such as SOx (oxides of sulfur), CO (carbon monoxide) and CO2 (carbon dioxide) and hydrocarbons). Companies have realized that one way of minimizing NOx emissions is to first detect them and then to employ some sort of feedback loop in the combustion process, thereby enabling the minimization of NOx production by, for example, combustion optimization or regeneration of NOx traps. Therefore, in many applications with exhaust-gas treatment systems, one NOx sensor is used upstream of the exhaust-gas treatment system (upstream) and a second sensor is used downstream of the exhaust-gas treatment system. The upstream sensor is used for the aforementioned feedback loop. Meanwhile, the downstream sensor is used mainly to confirm that the legislated emissions limits have not been exceeded.
