Aluminum hydroxide roasting system and method

Abstract

The invention discloses an aluminum hydroxide roasting system and method. The system includes a feeder, a dryer, a preheater, a roaster, and the like, and also includes a flue gas recirculation deviceand a fuel gas distribution device. The outlet end of a recirculating flue gas pipe is disposed on a gas communication pipe between a cooler and the roaster. The fuel gas distribution device includesa fuel gas header, a main burner and an auxiliary burner. A secondary air nozzle and a secondary air regulating valve are also disposed in the middle upper portion of the roaster. The roaster roastsaluminum hydroxide to generate hot flue gas, the hot flue gas is cooled, and dedusted, the cooled and dedusted flue gas as recirculating flue gas and hot air are mixed and partly burnt by the auxiliary burner to form high-temperature low-oxygen combustion-supporting air, and through the classification ratio and staged combustion of primary and secondary air, the initial concentration of nitrogen oxides can be reduced. Through use of a low-oxygen combustion mode and a staged combustion structure, the temperature of a main combustion zone is significantly reduced, and complete combustion of a fuel can be ensured while suppresses of formation of the nitrogen oxides.

Description

technical field [0001] The invention relates to a roasting system and method for aluminum hydroxide, belonging to the technical field of metallurgy. Background technique [0002] The roasting process of aluminum hydroxide is the last process in the production process of alumina, and it is an important link that determines the output, quality, energy consumption and pollutant discharge of alumina in the production process. At present, my country's aluminum hydroxide roasting technology widely adopts the gaseous suspension roasting technology of Smith Company in Denmark. In the gaseous suspension roaster, natural gas or coal gas is burned with air preheated to 700-1000°C to produce high-temperature flue gas, and the high-temperature flue gas heats the aluminum hydroxide material to complete the process of dehydration and partial crystal phase transformation to produce alumina. Alumina undergoes multi-stage cooling and finally becomes a qualified alumina product. The gas susp...

AI Technical Summary

Problems solved by technology

However, although SCR technology has high efficiency, it requires the use of expensive catalysts, which will gradually deactivate during use and need to be replaced regularly, which significantly increases the cost of the entire roasting process

Although the cost of SNCR technology is relatively low, its efficiency is low, and it cannot meet the requirements when used alone. Moreover, SNCR technology has a serious ammonia escape problem, causing secondary pollution

At the same time, SCR and SNCR are passive treatment measures, which cannot effectively and fundamentally solve the problem of nitrogen oxide generation in the roaster

Therefore, the low-nitrogen technology in the aluminum hydroxide roasting process still needs further breakthroughs

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