Method for preparing water-soluble magnesium ammonium sulphate phosphate fertilizer additive by phosphorite magnesium removal waste liquid

Abstract

The invention belongs to the technical field of the chemical industry, and particularly relates to a method for preparing a water-soluble magnesium ammonium sulphate phosphate fertilizer additive by phosphorite magnesium removal waste liquid. The method comprises the following steps: adding a phosphorite magnesium removal filtrate into a dosing tank; regulating pH to a range of 8 to 9; then feeding the phosphorite magnesium removal filtrate into a washing tower; filling sulfuric acid tail gas to carry out circulating washing; enabling obtained washing liquid to enter a neutralizing tank; filling liquid ammonia to perform a neutralization reaction for 30 to 60min; feeding obtained slurry into a setting tank to settle for 30 to 60min so as to obtain supernate and sediments; transferring thesediments into an aeration oxidation tank to perform a reaction; carrying out solid-liquid separation on the product obtained after the reaction is ended; and after concentration and crystallization,using the filtrate for producing a magnesium ammonium sulphate phosphate fertilizer. Not only is a magnesium resource in the phosphorite magnesium removal waste liquid recovered, but also recycling reproduction of the sulfuric acid tail gas, for example, sulfur dioxide, is implemented; economic benefits of tail gas treatment are improved; and not only is waste of resources avoided, but also production cost is reduced.

Description

technical field [0001] The invention belongs to the technical field of chemical industry, in particular to a method for preparing water-soluble magnesium ammonium sulfophosphate fertilizer additive from phosphate rock demagnesization waste liquid. Background technique [0002] Phosphorus and sulfur mixed acid leaching agent has good demagnesization effect and low phosphorus loss rate, and the magnesium oxide content in phosphate rock after the demagnesization process can be reduced by less than 2%, so as to meet the standard for acid-processed ore, mixed acid demagnesia The process will produce a large amount of acid waste liquid containing metal cations such as magnesium, calcium, iron, aluminum and phosphorus and sulfur. The composition is complex. If it is discharged directly without treatment, it will cause serious pollution to the environment. Eutrophication and acid pollution will change the PH value of the water body, inhibit the growth of microorganisms, hinder the p...

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Problems solved by technology

[0003] At present, there are many studies on the comprehensive utilization of magnesium resources in phosphate rock tailings, but there are few reports on the recovery and utilization of magnesium in phosphate rock waste liquid. In the prior art, ion exchange is mainly used. , extraction method, precipitation method and other methods to realize the recovery and utilization of the magnesium removal waste liquid. Among them, the ion exchange method separates the magnesium ions in the magnesium removal waste liquid of phosphate rock. Although the magnesium removal rate is high, the amount of resin is large and the regeneration cost is high. High; the solvent extraction method separates the separation of phosphorus and magnesium in the phosphate rock demagnesization solution, but the process is long, the cost of the extraction agent is high and the loss rate is high; the chemical precipitation method is the most effective method for recovering magnesium ions from the phosphate rock demagnesization solution, and has the advantages of The production cost is low, the operation control requirements are not high, and the process flow is simple. Among them, the process of preparing magnesium hydroxide by ammonia precipitation with sulfuric acid leaching acid solution is the most mature, but this method is not suitable for the treatment of phosphate rock demagnesia filtrate. Because the phosphorus content in the waste liquid is high, the optimum pH value for forming magnesium hydroxide is 11-12, and the optimum pH value for forming magnesium hydrogen phosphate is 5.0-6.0, so magnesium ions are more likely to be absorbed by the demagnesization solution with high phosphorus content. Magnesium hydrogen phosphate precipitates; therefore, further research is needed on the recovery and comprehensive utilization of magnesium from phosphate rock demagnesization solution