Honeycomb ceramics are composed of numerous equal pores. At present, the largest number of holes has reached 20-40 per square centimeter, the density is 4-6 grams per cubic centimeter, and the water absorption rate is up to 20%. Due to the characteristics of porous thin wall, the geometric surface area of ​​the carrier is greatly increased and the thermal shock resistance is improved. At present, the mesh holes of the products are mainly triangular and square, and the triangle is much better than the square, and the number of holes is also More, this is especially important as a catalytic carrier.
As the number of holes per unit area increases and the thickness of the carrier wall decreases, the thermal shock resistance of the ceramic carrier increases, and the temperature of thermal shock damage also increases. Therefore, honeycomb ceramics must reduce the expansion coefficient and increase the number of holes per unit area. The coefficient of thermal expansion is the main performance index. The current foreign level is α25-1000°C≤1.0×10-6°C-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 kaolin, talc, aluminum powder, clay, etc., and today it has broken through, especially the application of diatomaceous earth, zeolite, expansive soil and refractory materials. The application of honeycomb ceramics is increasingly widespread and the performance is getting more and more. it is good.
In addition to the honeycomb ceramics used for sintering, non-sintered honeycomb ceramics have appeared, which greatly enhances the catalytic performance. Not only does the apparent size evolve from the smallest ring shape to large columns and squares and circles. Depending on the mold design; honeycomb ceramics of different sizes and shapes can be made. For example, in the petrochemical industry, the refining air adsorption drying molecular sieve catalyst, the size of up to 0.8m, the width of 0.25m square, the number of holes per square centimeter to 25, from raw materials, process and mechanical manufacturing have changed a lot. In particular, the production process has been greatly improved. The honeycomb ceramic as a catalyst is required to be cracked during the molding process, and the organic component must be released cleanly. In addition to the wear resistance, a certain mechanical strength is required, and the regeneration is reused many times.
Honeycomb ceramics have dozens of products such as heat storage filler, activated carbon, activated alumina, molecular sieve, porcelain ball, tower packing and catalyst. The thermal capacity of honeycomb ceramics is more than J/kgk1000, and the temperature is ≥1700 °C. In furnaces such as heating furnaces, roasters, soaking furnaces, cracking furnaces, etc., fuel can be saved by more than 40%, production can be increased by more than 15%, and exhaust gas temperature is lower than 150 °C.
After the activated carbon powder or granules are made into the shape of honeycomb ceramics, the purification of water treatment and the ability of wastewater treatment are greatly improved, especially in the pharmaceutical industry, such as antibiotics, hormones, vitamins, nucleic acid injections, various injections, dehydration and decolorization of drugs, and the like.
Honeycomb ceramic filler has better specific surface area and better strength than other shaped fillers, which makes the vapor-liquid distribution more uniform, the bed resistance is reduced, the effect is better, and the service life can be extended in the petrochemical, pharmaceutical and fine chemical industries. The effect of the middle filler is quite good.
Honeycomb ceramics have an advantage in terms of catalysts. The honeycomb ceramic material is used as the carrier, and the unique coating material is used to prepare the precious metal, the rare earth metal and the transition metal, thereby having the advantages of high catalytic activity, good thermal stability, long service life and high strength.
Honeycomb ceramics for catalytic cracking are replacing existing products. Catalytic cracking uses heavy distillate between 200 and 500 ° C as raw materials (including vacuum distillation fraction, straight distillation light diesel oil, coking wax oil, etc.), with aluminosilicate as catalyst, and the reaction temperature is between 450 and 550 ° C ( Depending on the type of reactor). It has a large output (each large-scale catalytic cracking unit, cracking oil products over one million tons per year) and requires high technical conditions (for example, the catalyst is regenerated every few minutes or even seconds after contact with the oil, and flows through the fluidized bed catalyst every minute. Up to 10 t or more) As the catalytic activity increases, more stringent regeneration conditions are required in order to speed up the regeneration.
For example, 600 to 650 ° C, or even 700 ° C, the catalyst consumption is large, the consumption of 0.3 to 0.6 kg of catalyst per ton of feed oil, the mechanical strength of the catalyst is poor, the consumption is much larger. This requires a slight increase in catalyst activity, selectivity, and stability, which will be of great significance to production. Because of this, honeycomb ceramic catalysts are constantly being introduced and the market demand is increasing. These catalysts for catalytic cracking have been replaced by honeycomb ceramic catalysts, and large-sized porous ceramic honeycomb catalysts have emerged and have a strong development momentum.
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