Method for quickly converting NOx tail gas into potassium nitrate

Abstract

The invention discloses a method for quickly converting NOx tail gas into potassium nitrate, and solves the problems of the conventional tail gas treatment for existing enterprises in the prior art, such as high tail gas treatment cost, environmental pollution and the like. The method is characterized in that a nitrogen oxide and a potassium chloride solution (or a mixed solution) are rapidly converted into potassium nitrate in an absorption tower. The purity of potassium nitrate is controlled through controlling the concentration of dilute nitric acid, the volume of dilute nitric acid and the added amount of potassium chloride, and the purity of potassium nitrate is further improved through adopting the saturated solution of potassium nitrate as a scrubbing solution. Meanwhile, the yield of potassium nitrate is judged based on the concentration of Cl. Specifically, the method comprises the steps of (1) absorbing the industrial tail gas containing NOx, and converting the tail gas into nitric acid, wherein a 1% salt crystallization inhibitor is previously added in an absorbent; (2) reacting nitric acid with potassium chloride to convert the tail gas into potassium nitrate; (3) separating the HCl gas and dissolving out the potassium nitrate; (4) washing and separating the potassium nitrate; (5) drying the potassium nitrate and recycling the filtrate. The above method has the advantages of convenient operation, environmental protection, energy saving and the like. Based on the method, the NOx-contained tail gas of a chemical enterprise is directly converted into the potassium nitrate. Therefore, the method has wide popularization and application value.

Description

technical field [0001] The invention belongs to the comprehensive waste gas treatment technology of chemistry, chemical industry, medicine and environmental protection industries, and in particular relates to a method for rapidly converting nitrogen oxide tail gas into potassium nitrate. Background technique [0002] With the improvement of people's awareness of environmental protection, the emission standards of industrial tail gas are becoming more and more stringent, such as nitrogen oxides and sulfur dioxide emissions must meet the standards. At present, the treatment of nitrogen oxides tail gas in factories is generally to use lye to absorb or further oxidize and absorb Converted into nitric acid, due to the low concentration of nitric acid converted under normal pressure, it is difficult to bring benefits, and it can neither be sold nor digested. [0003] Potassium nitrate is not only an important industrial raw material but also a high-quality chlorine-free potassium-...

AI Technical Summary

Problems solved by technology

The method for producing potassium nitrate at this stage is mainly the metathesis reaction method. One is to use sodium saltpeter and potassium chloride to undergo a metathesis reaction. The Changsha Design and Research Institute of Chemical Industry adopts multi-step reaction and purification to obtain potassium nitrate with high purity (CN201510747903.0 ), but this reaction sodium saltpeter is less in our country and the price is more expensive, so the profit margin is limited; Shandong Changle County Nitrate Factory uses dilute nitric acid to produce potassium nitrate (CN92106421.7), the condition is 70-105 ℃, negative pressure Reaction and conversion at 300-400mm-Hg for more than 3 hours. In fact, this condition has already decomposed a large amount of nitric acid. The use of negative pressure concentrated salt solution consumes a lot of energy. Washing with a large amount of tap water during impurity removal will dissolve a large amount of potassium nitrate and reduce the yield.

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