Method using circulating fluidized bed for rice hull organic acid pretreatment and combustion to prepare nanometer SiO2

Abstract

The invention discloses a method using a circulating fluidized bed for rice hull organic acid pretreatment and combustion to prepare nanometer SiO2, belongs to the technical field of chemical engineering, and solves the problems in the existing method of utilizing the rice hulls to prepare high-purity silicon dioxide. The method comprises the following steps: step 1, preparing an organic acid solution for pretreating the rice hulls; step 2, placing the rice hulls into the organic acid solution to be soaked; step 3, utilizing a centrifugal machine to dehydrate the soaked rice hulls, and then using clear water to repeatedly clean the rice hulls; step 4, pumping the cleaned rice hulls and water together into a plate-and-frame filter press to be compressed and dehydrated until the moisture of the rice hulls is 30%; step 5, drying the rice hulls until the water content is 15% below; step 6, feeding the rice hulls into a circulating fluidized bed boiler to be combusted, feeding the rice hull ash after being burnt into a bag type dust remover along with the flue gas, and grinding the rice hull ash collected by the bag type dust remover, so as to obtain the nanoscale active silicon dioxide with the particle size of 50-80 nm and the purity of 98.0-99.6%. The method disclosed by the invention is used for preparing the nanometer SiO2.

Description

Technical field [0001] The present invention belongs to the field of chemical technology, which involves the specifically involved circulating fluid bed combustion organic acidic acid intercourse to prepare rice shells to prepare nano SIO 2 Methods. Background technique [0002] SiO (SIO 2 ) It is a very widely used chemical product that has important use in rubber, ink, plastic, medicine, pesticides, toothpaste, cosmetics, paint and other industries. [0003] The main ingredient of rice shell ash is silicon dioxide, so the rice shells, as by -products in the process of rice processing and production, are agricultural processing wastes with industrial value. At present, the undertaken rice shells are currently using unsolved rice shells at low temperature 600 ℃ ~ 650 650Burning for a long time under ° C can obtain nano -grade silica -grade silica containing impurities such as metal oxides. Therefore, rice shells are ideal raw materials for preparing high -purity and non -fixed si...

AI Technical Summary

Problems solved by technology

Problems in this method: long burning time, discontinuous burning, difficult temperature control; and secondary pollutants such as HCl, SO 2 , NO X Emissions, corrosion of boiler heating surfaces

Problems in this method: the incineration device in this method is too simple, the combustion is discontinuous, the heat is not recovered, the temperature control is difficult, the silicon dioxide content is low, and the rice husk burning after inorganic acid treatment has secondary pollutants such as HCl and SO 2 , NO X Emissions, corrosion of boiler heating surfaces

Problems in this method: Dry distillation and carbonization of rice husks cannot directly obtain high-purity ultrafine silica through water washing, because the carbon content of carbonized rice husks is very high, and the waste water after inorganic acid treatment contains a large amount of carbon black, which is difficult to process

[0010] 1. Combustion after treating rice husk with inorganic acid will cause SO 2 , NO X , HCl and other secondary pollution;

[0011] 2. The existing processes all adopt fixed-bed intermittent combustion or dry distillation of rice husks, so the temperature is difficult to control and cannot be continuously produced;

[0012] 3. After dry distillation and carbonization, the pickling step is added, which increases the difficulty and cost of wastewater treatment;

[0013] 4. The heat recovery rate is not high or cannot be recovered

[0014] It can be seen that there is currently no process for preparing silica that can achieve industrial continuous production and make full use of the heat generated by combustion (such as power generation or heating)

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