White carbon black and white carbon black is a general term for white powdered X-ray amorphous silica and silicate products, mainly referring to precipitated silica, gas-phase silica, and process 1) gas-phase method


Mainly chemical vapor deposition (CAV) method, also known as pyrolysis, dry method, or combustion method. Its raw materials are generally silicon tetrachloride, oxygen (or air), and hydrogen, which react at high temperatures to form. The reaction formula is:


SiCl4+2H2+O2->SiO2+4HCl


Air and hydrogen are respectively pressurized, separated, cooled and dehydrated, dried with silica gel, and filtered for dust removal before being sent to the synthetic hydrolysis furnace. Send the raw material of silicon tetrachloride to the distillation tower for distillation, heat and evaporate it in the evaporator, and use the dried and filtered air as the carrier to send it to the synthesis hydrolysis furnace. After gasification of silicon tetrachloride at high temperature (flame temperature 1000-1800 ℃), it undergoes gas-phase hydrolysis with a certain amount of hydrogen and oxygen (or air) at a high temperature of around 1800 ℃; At this time, the generated gas-phase silica particles are extremely fine and form aerosols with the gas, which are not easy to capture. Therefore, they are first aggregated into larger particles in the aggregator, collected by a cyclone separator, and then sent to a deacidification furnace. The gas-phase silica is washed with nitrogen-containing air to a pH value of 4-6, which is the finished product.


The gas phase production technology of German company Degussa and American company Cabot is globally leading. Their production equipment has a large scale, high degree of automation, low product cost, multiple grades (especially functional specialized product grades applied in special fields), good quality, such as uniform surface area distribution and low water content. China's Shenyang Chemical Co., Ltd. and Shanghai Chloroalkali Chemical Co., Ltd. also use gas-phase production, but they are far behind foreign large companies in terms of production scale, production technology, automation level, and product grades. Guangzhou Jibisheng Technology Industry Co., Ltd. is currently the largest producer, most complete brand, and most advanced supplier of gas-phase silica in China. It is the drafting unit responsible for the national standard GB20020-2005 for gas-phase silica.


(2) Precipitation method


The precipitation method, also known as sodium silicate acidification method, uses water glass solution to react with acid, and obtains white carbon black through precipitation, filtration, washing, drying, and calcination. The reaction formula is:


Na2SiO3+2H+->White carbon black+2Na++H20


Most domestic production enterprises adopt the precipitation method.


New methods


The new method mainly uses non-metallic minerals and their extensions as silicon sources and uses precipitation method to prepare white carbon black. The key technology is to transform crystalline silica and silicates into amorphous silica. The main raw materials include wollastonite, opal, halloysite, olivine, serpentinite, kaolin, hard kaolin, coal gangue, fly ash, etc.


Emphasis is placed on introducing the process technology for preparing white carbon black using kaolin or hard kaolin, coal gangue or fly ash as raw materials.


(1) Using kaolin or hard kaolin as raw materials

First, crush kaolin or hard kaolin to 50-60 mesh, then calcine at a high temperature of 500-600 ℃ for 2 hours. Then, mix the calcined soil with industrial hydrochloric acid with a concentration of 30% in a ratio of 1:2.5 (weight), acid soak at around 90 ℃ for 7 hours, neutralize, filter, wash, and dry to obtain white carbon black. The product quality meets the GB10507-89 standard; Simultaneously obtaining high-efficiency water purifier polyaluminum chloride. The calcination and acid leaching reaction formulas are as follows:


Baking: Al2O3?? 2SiO2?? 2H20->Al2O3?? 2SiO2+2H20


Acid leaching: Al2O3?? 2SiO2+6HCl+9H20->2AlCl3?? 6H20+2SiO2


(2) Using coal gangue or fly ash as raw materials


First, crush the coal gangue or fly ash to a particle size less than 120 mesh, and then divide it into two steps:


The first step in producing sodium silicate is to mix the crushed coal gangue or fly ash with soda ash in a weight ratio of 1:50, and obtain sodium silicate by high-temperature melting (1400-1500 ℃, 1 hour), water extraction and leaching (above 100 ℃, 4-5 hours), filtering out impurities, and concentrating the filtrate to 45-46 Baume degrees.


The second step in producing white carbon black: First, prepare sodium silicate into a water glass solution (modulus of 2.4-3.6, SiO2 content of 4-10%), then acid soak in 5-20% sulfuric acid (28-32 ℃, 8-16 hours), then heat up to 80 ℃, stir, adjust the pH value to 5-7, mature for 20 minutes, filter, wash, dry, and sort to obtain white carbon black. The white carbon black is active and has high purity.