阅读说明：本技术 一种利用废盐联合制碱的方法 (Method for preparing alkali by using waste salt in combination manner ) 是由 刘建武 张跃 严生虎 沈介发 辜顺林 马晓明 陈代祥 于 2019-10-29 设计创作，主要内容包括：本发明公开了一种利用废盐联合制碱的方法,属于工业生产中废盐回收处理技术领域。常温下,将集中收集的废盐经预处理后溶解在碳酸氢铵溶液制成一定浓度的饱和盐水溶液,移至高压反应釜中吸氨,吸氨完毕后作降温处理,水浴保温下持续通入CO<Sub>2</Sub>进行碳酸化,当釜中温度开始下降,水浴加热并保温,反应完毕降温出料,过滤并多次洗涤碳酸氢钠滤饼,降低其中NaCl含量,烘干称重,测量纯度；滤液加热蒸出氨、二氧化碳,加入废盐直至滤液饱和,加热滤液,趁热过滤,滤液降温结晶析出NH<Sub>4</Sub>Cl晶体,烘干称重,测量纯度,并将母液用吸附剂进行处理,回收套用。本发明通过采用探索不同反应条件,可实现得到更高纯度的纯碱和NH<Sub>4</Sub>Cl产品。(The invention discloses a method for preparing alkali by utilizing waste salt in a combined manner, belonging to the technical field of waste salt recovery treatment in industrial production. At normal temperature, the waste salt collected in a centralized way is dissolved in an ammonium bicarbonate solution after being pretreated to prepare a saturated salt water solution with a certain concentration, the saturated salt water solution is moved to a high-pressure reaction kettle to absorb ammonia, then the temperature is reduced after the ammonia absorption is finished, and CO is continuously introduced into the high-pressure reaction kettle under the condition of water bath temperature preservation 2 Carbonating, when the temperature in the kettle begins to decrease, heating in a water bath and preserving heat, cooling and discharging after the reaction is finished, filtering and washing the sodium bicarbonate filter cake for multiple times to reduce the NaCl content, drying and weighing, and measuring the purity; heating the filtrate to evaporate ammonia and carbon dioxide, adding waste salt until the filtrate is saturated, heating the filtrate, filtering while the filtrate is hot, cooling the filtrate to crystallize and separate out NH 4 Cl crystal, drying, weighing, measuring purity, treating mother liquor with adsorbent, and recycling. The invention can realize the purpose of obtaining higher purity soda ash and NH by exploring different reaction conditions 4 And (4) Cl products.)

1. The method for preparing alkali by using waste salt in a combined manner is characterized by comprising the following steps of:

(1) at normal temperature, the waste salt collected in a centralized way is dissolved in an ammonium bicarbonate solution after being pretreated to prepare a saturated salt water solution with a certain concentration, the saturated salt water solution is moved to a high-pressure reaction kettle to absorb ammonia, then the temperature is reduced after the ammonia absorption is finished, and CO is continuously introduced into the high-pressure reaction kettle under the condition of water bath temperature preservation₂Carbonating, when the temperature in the kettle begins to decrease, heating in a water bath and preserving heat, cooling and discharging after the reaction is finished, filtering and washing the sodium bicarbonate filter cake for multiple times to reduce the NaCl content, drying and weighing, and measuring the purity;

(2) heating the filtrate to evaporate ammonia and carbon dioxide, adding waste salt until the filtrate is saturated, heating the filtrate, filtering while the filtrate is hot, cooling the filtrate to crystallize and separate out NH₄And drying and weighing Cl crystals, measuring the purity, treating the mother liquor by using an adsorbent, and recycling and reusing the mother liquor.

2. The method for preparing alkali by using waste salt in combination as claimed in claim 1, wherein the waste salt in step (1) is subjected to calcination pretreatment in advance to reduce the organic content therein, so as to ensure that the mass concentration of NaCl is 60-85%, the molar ratio of ammonia gas to NaCl in the waste salt is (1.0-2.0): 1, the mass concentration of the brine solution is 30-50%, the dosage of ammonium bicarbonate is 10-18% (wt.) of the mass of the waste salt, the water bath heating temperature is 50-80 ℃, and the pressure in the carbonation process is always kept at 1-5 MPa.

3. The method for preparing alkali by using waste salt in combination as claimed in claim 1, wherein the adsorbent in step (2) is one of activated carbon, macroporous sulfonic acid resin, acrylate-dimethacrylate copolymer and porphyrin cross-linked chitosan, and the amount of the adsorbent is 5-30% (wt.) of the mass of the waste salt.

Technical Field

The invention relates to a process method for preparing alkali by utilizing waste salt in a combined way, which relates to the technical field of waste salt recovery treatment in industrial production, realizes the purpose of recycling by using a combined alkali preparation method and reusing mother liquor repeatedly and belongs to the technical field of waste salt recovery treatment in industrial production.

Background

The industrial utilization of waste salt for preparing alkali mainly comprises an ammonia alkali method and a combined alkali preparation method. The ammonia-soda process is to calcine limestone to produce lime and carbon dioxide, slake lime to obtain lime milk, and carbonating with ammoniated ammonia salt water to produce heavy soda. CO from limestone calcination and heavy alkali calcination₂Compressing, cooling and sending to a carbonization tower. Filtering and washing heavy alkali, and distilling and recovering ammonia in mother liquor. The combined soda production method is characterized in that salt, ammonia and carbon dioxide which is a byproduct in the synthetic ammonia industry are used as raw materials, and soda ash and ammonium chloride are produced simultaneously, namely the combined method for producing soda ash and ammonium chloride is called as the combined method and is called as the combined soda production method for short.

The former part of the combined alkali method is the same as the ammonia-alkali method, and finally, ammonium chloride crystals are separated out to be used as a nitrogen fertilizer product, and the rest salt is returned to be used for preparing sodium bicarbonate. Compared with the ammonia-soda process, the combined soda process has the following advantages: the utilization rate of raw materials is high; limestone and coke are not needed, so that the cost is reduced; the soda part does not need heavy equipment such as an ammonia still, a lime pit, an ash melting machine and the like, the flow is shortened, and the cost of building long investment is reduced; no large amount of waste liquid and waste residue are discharged, and the factory can be built in the country.

Disclosure of Invention

Aiming at the method, the invention recycles the recovered waste salt, improves the effective utilization rate of the reaction materials through process optimization, and further improves the existing industrialized production method.

In order to achieve the purpose, the technical scheme adopted by the invention is a method for preparing alkali by using waste salt in a combined manner, and the method is carried out according to the following steps:

(1) at normal temperature, the waste salt collected in a centralized way is dissolved in an ammonium bicarbonate solution after being pretreated to prepare a saturated salt water solution with a certain concentration, the saturated salt water solution is moved to a high-pressure reaction kettle to absorb ammonia, then the temperature is reduced after the ammonia absorption is finished, and CO is continuously introduced into the high-pressure reaction kettle under the condition of water bath temperature preservation₂Carbonating, when the temperature in the kettle begins to decrease, heating in a water bath and preserving heat, cooling and discharging after the reaction is finished, filtering and washing the sodium bicarbonate filter cake for multiple times to reduce the NaCl content, drying and weighing, and measuring the purity;

(2) heating the filtrate to evaporate ammonia and carbon dioxide, adding waste salt until the filtrate is saturated, heating the filtrate, filtering while the filtrate is hot, cooling the filtrate to crystallize and separate out NH₄And drying and weighing Cl crystals, measuring the purity, treating the mother liquor by using an adsorbent, and recycling and reusing the mother liquor.

The waste salt in the step (1) is subjected to calcination pretreatment in advance, the content of organic matters in the waste salt is reduced, the mass concentration of NaCl is ensured to be 60-85%, the molar ratio of ammonia to NaCl in the waste salt is (1.0-2.0) to 1, the mass concentration of a saline solution is 30-50%, the feeding amount of ammonium bicarbonate is 10-18% (wt.) of the mass of the waste salt, the water bath heating temperature is 50-80 ℃, and the pressure in the carbonation process is always kept at 1-5 MPa.

Wherein the adsorbent in the step (2) is one of activated carbon, macroporous sulfonic acid resin, acrylate-dimethacrylate copolymer and porphyrin cross-linked chitosan, and the dosage of the adsorbent is 5-30% (wt.) of the waste salt.

Compared with the prior art, the invention has the following advantages:

1. the invention can realize the purpose of obtaining higher purity soda ash and NH by exploring different reaction conditions₄And (4) Cl products.

2. The method has the advantages of simple reaction equipment, strong operability, no great potential safety hazard and improvement on the safety of the reaction process.

3. The method is simple and convenient to operate and wide in application range, and can provide an effective method for recycling the waste salt.

Drawings

FIG. 1 is a process flow diagram of the method for producing alkali by using waste salt in combination.

Detailed Description

The present invention is described in detail with reference to the following examples, which are only preferred embodiments of the present invention, and the scope of the present invention is not limited thereto, and any person skilled in the art can substitute or change the technical solution of the present invention and the inventive concept within the technical scope of the present invention.