Preparation method of nitrogen phosphorus or nitrogen phosphorus potassium composite fertilizer

Abstract

A process for preparing the compound NP or NPK fertilizer features that the powdered or granular monoammonium phosphate is used to replace dryer tubular reactor and control the reaction heat and avoid the overconcentrating of heat, and the phosphoric acid is added to the cyclone washing towder other than gas-liquid separator in tail gas washing system to use evaporation power of washing system to maximum, so it is possible to prepare said compound fertilizer with diluted phosphoric acid.

Description

technical field [0001] The invention relates to a preparation method of compound fertilizer, in particular to a preparation method of nitrogen phosphorus or nitrogen phosphorus potassium compound fertilizer. Background technique [0002] The current technologies for producing compound fertilizers using dilute phosphoric acid include: [0003] 1. "Production process of sulfur-based compound fertilizer": dilute phosphoric acid can be used (concentration in P 2 o 5 Calculated as 20% to 28%) to produce. In the production process, dilute phosphoric acid is mixed with potassium bisulfate, and then atomized and sprayed after neutralization in the neutralization tank. Dilute phosphoric acid brings in more water, resulting in a high return ratio and high drying energy consumption. Nitrogen, phosphorus, and potassium The ratio of the product is limited by the main component potassium ammonium phosphate in the product, and the product ratio is not very flexible. Such as the sulfur-...

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Problems solved by technology

The production process of this method is: dilute phosphoric acid reacts with ammonia in the neutralization tank first, and then concentrates the slurry, but the concentration of the slurry also needs to evaporate the water in it, and the energy consumption is still high

[0005] 3. "Pre-neutralization tank method": The pre-neutralization tank method commonly used at home and abroad can be used in the form of P 2 o 5 Phosphoric acid with a concentration of 40% to 44%, but the heat loss in the pre-neutralization reaction is large, the utilization is insufficient, the water entering the system is high, the return ratio is as high as 1:4 to 5, and the drying load is large

[0006] 4. "Slurry concentration and phosphoric acid concentration co-production method": Chinese patent 02113425.1 applied by Sichuan University discloses a technology for producing monoammonium from diammonium phosphoric acid washing tail gas, using P 2 o 5 Medium-concentration phosphoric acid with a concentration of 40% to 44% and P 2 o 5 Dilute phosphoric acid with a concentration of 25% to 28%, but the production of diammonium still adopts the pre-neutralization tank method. The tail gas in the production process of diammonium is washed with dilute phosphoric acid and then used for the production of monoammonium by the slurry concentration method. balance

Phosphoric acid is required to be P 2 o 5 The calculated concentration is 30% to 54%, but its disadvantage is that salts with high solubility such as urea and ammonium nitrate are added in the process of producing nitrogen, phosphorus and potassium compound fertilizers. In order to control water balance and reduce the return ratio, the concentration of phosphoric acid is required to be at 50 %above

[0008] 7. Shanghai Research Institute of Chemical Industry discloses "Pipeline Reactor Ammonium Phosphate Production Process" in Chinese patent 00127678.2. This process can use low-concentration phosphoric acid, but needs to add a large amount of sulfuric acid to provide reaction heat. The ratio of phosphoric acid: sulfuric acid is 0.3 ~0.7:1 weight ratio, nitrogen, phosphorus and potassium compound fertilizer can be produced, but the total nutrient content of the final product is low, the formula is not flexible, and the requirements for the material of the tubular reactor are also high

[0009] 8. The Chinese patent No. 90102317.5, which was applied by Norwegian Hydro company on April 19, 1990 and published on November 6, 1991, discloses a method for making diammonium phosphate granular fertilizer, using P 2 o 5 Phosphoric acid production with a concentration of 36% to 50%, but in order to control the reaction heat balance and water balance, the single dryer tubular reactor process is adopted, and the slurry can not be sprayed into the granulator for granulation production. In the granulator Add washing water and steam granulation, the return rate is low, but the drying load is large

[0010] 9. In order to reduce the return ratio, GP company in France has developed a double-tube reactor to transfer part of the heat of reaction to the dryer, but it needs to use P 2 o 5 Concentrated phosphoric acid with a concentration of 50% to 57% has high requirements on the quality of phosphate rock, and the operating conditions of the tubular reactor of the dryer are extremely harsh, the copying board of the dryer is severely scabbed, the production efficiency is low, and the cleaning work large