Device and method for combined removal of sulphur dioxide (SO2), nitrogen oxide (NOX) and mercury from fume

Abstract

The invention discloses a device and a method for combined removal of sulphur dioxide (SO2), nitrogen oxide (NOX) and mercury from fume. In the device, a nitrogen dioxide (NO2) generation device is added between a dust remover and a wet desulphurization tower in a wet desulphurization system. The method comprises the following steps of: adding 9 percent of NO2 gas into the fume which is subjected to dust removal by the dust remover by using the NO2 generation device; adjusting the content of NO2 in the fume to 50 percent of the total amount of the NOX; controlling the pH value of a circulating solution in an absorption tower to 5.5 to 6.3; absorbing and oxidizing the SO2 and the NOX in the fume by a reaction tower to obtain a mixed solution of ammonium sulphate and ammonium nitrate; carrying out operation on the mixed solution in an ammonium sulphate and ammonium nitrate recovery system to generate a fertilizer which can be used for agricultural production, wherein desulphurization efficiency is over 95 percent and denitration efficiency is over 80 percent; and after adding the NO2 into the fume, oxidizing a certain amount of mercury oxide (Hg<O>) as Hg<2+>, absorbing the Hg<2+> by a water solution of the system, and removing from the fume, wherein the removal efficiency of the Hg<O> can be increased by over 50 percent.

Description

technical field [0001] The invention relates to a device and method for jointly removing sulfur dioxide, nitrogen oxides and mercury in flue gas, belonging to the technical field of air pollution control. Background technique [0002] With the rapid development of my country's economy, industry and agriculture, the emissions of air pollutants sulfur dioxide and nitrogen oxides have also increased rapidly. As of 2009, my country's sulfur dioxide emissions were 25.9 million tons; nitrogen oxide emissions were about 16 million tons, of which coal-fired boiler flue gas emissions accounted for nearly 70%. If no effective nitrogen oxide pollution control measures are taken, my country's nitrogen oxide emissions will reach about 29 million tons in 2020. And in recent years, the concentration of nitrogen oxides in the air of some super-large cities in my country exceeds the standard, the environmental capacity of nitrogen oxides is basically in a saturated state, and some places ev...

AI Technical Summary

Problems solved by technology

At present, large-scale flue gas desulfurization has caused the accumulation of desulfurized gypsum; and the implementation of large-scale flue gas denitrification projects will inevitably lead to a situation where flue gas denitrification and agriculture compete for ammonia and urea resources.

Obviously, the above two mainstream flue gas desulfurization and denitrification technologies and processes have high operating costs, and the by-products cannot be fully recycled, let alone the organic combination of the two basic national policies of environmental protection and agriculture. Long-term operation will seriously hinder my country's flue gas desulfurization The sustainable development of denitrification and environmental protection is not suitable for my country's national conditions

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