Wet denitration method for high-sulfur flue gas

Abstract

The invention discloses a wet denitration method for high-sulfur flue gas. The method comprises the following steps of 1) purifying, 2) conducting conversion and absorption, (3) discharging gas, and 4) conducting acid production treatment. High-sulfur flue gas self-denitration is carried out by adopting the characteristics that a purified dilute acid aqueous solution absorbs part of nitrogen oxides and concentrated sulfuric acid, and sulfur trioxide reacts with the nitrogen oxides to generate nitroso sulfuric acid. Advanced treatment of nitrososulfuric acid and iron nitrososulfate in the concentrated sulfuric acid is focused, and nitrososulfuric acid and iron nitrososulfate are reduced into nitrogen, water and sulfuric acid or ferrous sulfate through a medicament, so that the final purposes of sulfuric acid wet denitration and no adverse byproducts are achieved, and a complete closed-loop process is formed. According to the denitration system disclosed by the invention, advanced treatment processes such as reduction and purification of nitrososulfuric acid or iron nitrososulfate are also added. Not only are NOHSO4 and Fe(NO)SO4 reduced completely, but also the adverse effect of excess of a small amount of reducing agent is eliminated thoroughly, and the production quality of sulfuric acid is not reduced practically.

Description

technical field [0001] The invention belongs to the technical field of environmental protection denitrification, and in particular relates to a method for wet denitrification of high-sulfur flue gas. Background technique [0002] Due to the presence of nitrogen and fuel coal during the smelting process, nitrogen oxides cannot be avoided. With oxygen-enriched smelting, nitrogen still exists in the combustion-supporting gas, but its content is reduced from 78% in the air to 30%, or even less, but oxygen-enriched smelting significantly increases the combustion temperature (above 1500°C), which is a thermal type. The main cause of nitrogen oxides. When coal is used as fuel in the smelting process, almost all organic nitrogen in coal is converted into fuel-type nitrogen oxides. The cumulative concentration of nitrogen oxides in the two forms is hundreds of mg / Nm 3 , even thousands of mg / Nm 3 . Since sulfur combustion in non-ferrous smelting produces a large amount of sulfur ...

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Problems solved by technology

Since sulfur combustion in non-ferrous smelting produces a large amount of sulfur dioxide and part of sulfur trioxide, the presence of sulfur makes the treatment of nitrogen oxides in flue gas particularly difficult

[0003] Using the SNCR process, there are two major problems in the reduction of nitrogen oxides by spraying ammonia into the denitrification temperature range of the metallurgical furnace: 1. Oxygen-enriched combustion leads to high oxygen content in the flue gas. reaction, the actual consumption of ammonia is much larger than the ammonia demand for only reducing nitrogen oxides, and the operating cost is greatly increased; 2. The excess ammonia injected into the system will combine with sulfur trioxide in the low temperature area to form NH 4 HSO 4 , it has strong water absorption, and the acidic liquid formed will seriously corrode carbon steel equipment such as cloth bags and electric dust collectors, and its chance of corroding waste heat boilers and other smelting equipment will greatly increase during the process of shutting down the furnace to cool down

For non-ferrous smelting plants without self-produced coke oven gas sources, additional electricity or gas is needed to supplement this part of the heat energy shortage, which is the main factor causing the high energy consumption of the heating SCR process, and at the same time limits the use of this process in the non-ferrous industry to promote

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