Process for preparing potassium nitrate by double decomposition method

Abstract

The invention provides a metathesis method for preparation of potassium nitrate. After raw potassium chloride, ammonium nitrate and craft water finish their preparation at a certain ratio, they are input into vacuum cooling crystallizer. Then potassium nitrate is separated by crystallization and grows up. The crystallized liquid thickens by the thickening apparatus and continuously separates potassium nitrate as aim products by centrifugal machine. After the separated mother liquid exchanges heat with the reacting liquid, it is input into natural circulation evaporator to concentrate, adopting backward feed and dual effect concentration with constant pressure in the first chamber and negative pressure in the second chamber. Through cooling crystallization, thickening by the thickening apparatus, the concentrated liquid continuously separates ammonium chloride as by-products. The gained secondary mother liquid returns to preparation groove. Repeating this cyclic process, we could sequentially get solid potassium nitrate and ammonium chloride.The invention has improved production stability and product quality a lot and reduced raw material consumption and energy consumption, with simple and serial flow process. The invention has realized the mass production.

Description

technical field [0001] The invention relates to a method for preparing potassium nitrate by double decomposition reaction of ammonium nitrate solid (or ammonium nitrate solution above 65%) and potassium chloride solid. Background technique [0002] Pure potassium nitrate contains N 13.85% (mass fraction, the same below), K 2 O46.59%; fertilizer grade KNO 3 Contains N13.5%, K 2 O44%~46%, is a high-efficiency nitrogen and potassium compound fertilizer, especially suitable for chlorine-avoiding crops such as tobacco, coffee, tomatoes, grapes, citrus, gardening, flowers, potatoes, avocados, tea, field vegetables, mangoes, etc. Fertilize. [0003] The chemical principle of the double decomposition of ammonium nitrate and potassium chloride to produce potassium nitrate and by-product ammonium chloride is as follows: [0004] <chemistry num="001"> <chem file="200510094223_cml001.xml" / > < / chemistry> [0005] The realization of this process is to carry out ...

AI Technical Summary

Problems solved by technology

This is firstly because the cooling process of the reaction feed liquid needs to be cooled indirectly through the heat exchanger, and the heat exchange surface of the heat exchanger is easily covered with precipitated solid potassium nitrate, commonly known as "scarring" on the cooling surface, thus hindering the heat exchange. The process affects the cooling result of the entire feed liquid, so that the end temperature of the feed liquid cooling cannot reach the expected target of the design, and in each batch of crude product K 2 The content of O is significantly different and very unstable; correspondingly, the composition of the circulating mother liquor in the production process fluctuates greatly

The ratio of raw materials and water addition is difficult to grasp, and it is difficult to form a stable cycle, which directly leads to the inability of continuous and large-scale production

Another aspect is the evaporation of the ammonium chloride mother liquor. At present, it is generally used to heat the mother liquor after the coil steam is installed inside the container. The heat exchange efficiency is low and the steam consumption is also large; device, the serious problem is corrosion, high temperature above 100 ℃ and K + 、CL - , NH 4 + , NO 3 - Under the condition of quaternary water-salt system, the internal parts of the container are obviously corroded, especially the rotating equipment such as stirring paddle

If the evaporation temperature is reduced by vacuuming, it is difficult to achieve dynamic sealing at the support of the stirring shaft and the top cover.

This results in frequent replacement of materials, large maintenance workload, increased labor intensity and consumption of raw materials, and it is difficult to enlarge the equipment body to achieve large-scale production

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