CN102476790A - Method for preparing hydrochloric acid and potassium carbonate by using KCl as raw material through molten hydrolysis method - Google Patents

Abstract

A new method for directly producing hydrochloric acid and potassium carbonate by molten state hydrolysis of potassium chloride, which is characterized in that potassium chloride and KB ₅ O ₈ are melted and mixed by utilizing the special properties of KB ₅ O ₈ molten state, and then passed into Superheated steam makes the hydrogen ions in the system combine with chloride ions to become hydrogen chloride gas, which is mixed with the remaining water vapor after the reaction, and becomes hydrochloric acid solution after condensation. The alkali metal borate with a smaller ratio of B ₂ O ₃ /K ₂ O generated during the reaction process is quenched in water, then regenerated KB ₅ O ₈ ·4H ₂ O through carbonation, and recycled after drying. While regenerating potassium pentaborate by carbonation, KHCO ₃ solution is obtained, which is further processed to obtain K ₂ CO ₃ .

Description

A kind of method that takes KCl as raw material molten state hydrolysis to prepare hydrochloric acid and salt of wormwood

technical field

The invention belongs to brine chemical industry and relates to a method of using industrial potassium chloride as a raw material and potassium pentaborate as an intermediate circulation medium to undergo hydrolysis reaction in a high-temperature molten state, firstly prepare hydrochloric acid, and then go through a carbonation process to prepare potassium carbonate products .

Background technique

Potassium carbonate is one of the important basic inorganic chemical, pharmaceutical and light industrial raw materials. It is mainly used in optical glass, welding electrodes, electron tubes, TV picture tubes, light bulbs, printing and dyeing, dyes, inks, photographic medicines, sodium hydroxide, polyester, Production of explosives, electroplating, tanning, ceramics, building materials, crystals, soaps and medicines; it can also be used as potassium-containing fertilizers, gas adsorbents, dry powder fire extinguishing agents, rubber anti-aging agents, and for removing carbon dioxide from fertilizer synthesis gas . With the continuous development of high and new technology, the application of potassium carbonate in detergent additives, monosodium glutamate, food and other fields is also expanding day by day. At present, potassium carbonate is mainly used in the manufacture of potassium glass, potassium soap, and other inorganic chemicals, for the removal of hydrogen sulfide and carbon dioxide in industrial gases, and also for welding electrodes, ink manufacturing, printing and dyeing industries, etc.

Potassium carbonate production includes plant ash method, Lubrand method, electrolysis method, ion exchange method and so on. Commonly used are electrolysis and ion exchange. The plant ash method is the oldest method, that is, it is extracted from the plant ash burnt from various plant shells (such as cottonseed shells, tea seed shells, tung seed shells, and sunflower shells). Plant ash contains soluble salts such as potassium carbonate, potassium sulfate, and potassium chloride, which can be separated by precipitation and filtration. This method is rarely used because of low product quality, uneconomical, and limited by raw material sources. The Lublin method is to mix potassium sulfate with coal powder and lime, reduce and roast to obtain black ash (including potassium carbonate, calcium sulfide and other fired products), and obtain potassium bicarbonate after leaching, filtering, evaporating and carbonizing. The product is obtained by filtering and calcining; this method has been replaced by other methods due to the long process flow and other reasons.

The electrolysis method is to electrolyze the potassium hydroxide solution obtained after potassium chloride, and carbonize it with carbon dioxide in a carbonization tower; evaporate and filter in a multi-effect evaporator to obtain potassium bicarbonate; and then calcinate to obtain the product. This method is widely used because of the easy availability of raw materials, high utilization rate of potassium, and no generation of three wastes, but the power consumption is relatively large.

The ion exchange method is to use cation exchange resin to exchange with potassium chloride. Then eluted with ammonium bicarbonate to form a dilute solution of potassium bicarbonate, and the product is obtained by multi-effect evaporation, carbonization, crystallization, separation, and calcination; this method has good product quality and short process flow, but is only suitable for small-scale production.

The method of the invention utilizes the reaction between potassium chloride and borate in a high-temperature molten state to obtain the product from chloride ions in the potassium chloride in the form of hydrochloric acid, and carbonates the potassium-containing molten salt to produce potassium carbonate. The chemical reaction process of the method has not been reported in the literature, and at the same time, the process route is short, forming a brand-new method for preparing hydrochloric acid and potassium carbonate by molten state hydrolysis.

Contents of the invention

A new method for directly producing hydrochloric acid and potassium carbonate by molten state hydrolysis of potassium chloride. The molten state hydrolysis is a hydrolysis reaction in a molten state by passing superheated steam into an alkali metal chloride in a molten state , known as "melt hydrolysis". Its main principles are as follows:

The overall reaction balance formula:

离子，热分解得纯d净K₂CO₃产品。该方法主要利用KB₅O₈溶解度小的特征，容易实现再生循环，而碳酸化过程CO₂分压1Kg/cm²可满足要求。Reaction formula (1) shows that KCl solid and KB ₅ O ₈ crystals are mixed and heated to 800-1200°C for eutectic reaction, and react with superheated steam, and KB ₅ O ₈ has acidity after melting above 800°C, which can provide for the decomposition of KCl Acidic environment; Cl in the melt ^is hydrolyzed into gaseous HCl, mixed with the remaining water vapor after the reaction, and separated from the melt, and becomes a hydrochloric acid solution after condensation; the melt KBO ₂ (actually B ₂ O ₃ /K ₂ A series of K-series borates whose O ratio is less than 2, that is, potassium polyborate between K ₂ B ₄ O ₇ and K ₄ B ₂ O ₅ , mainly K ₂ B ₄ O ₇ ) is directly quenched into a slurry. Reaction formula (2) shows that the slurry reacts with CO ₂ gas, the carbonation reaction temperature is 30-40°C, the pressure is 0.1-0.3Mpa, the crystallization temperature is 10-15°C, and KB ₅ O ₈ ·4H ₂ O crystals and KHCO are generated ₃ Nearly saturated solution, after filtration, KB ₅ O ₈ ·4H ₂ O crystals are returned, dried and decrystallized water is mixed with new KCl solid, and then eutectically hydrolyzed. The KHCO ₃ nearly saturated solution obtained by filtration is refined to remove Cl ^- ,

Ions, thermal decomposition to obtain pure d K ₂ CO ₃ products. This method mainly utilizes the feature of low solubility of KB ₅ O ₈ , which is easy to realize the regeneration cycle, and the CO ₂ partial pressure of 1Kg/cm ² in the carbonation process can meet the requirements.

The superheated steam is the superheated steam whose temperature reaches above 200°C but whose pressure is normal pressure.

Compared with the existing method for making acid and alkali, the present invention has the following advantages:

(1) No Ca ²⁺ is involved, no CaCO ₃ is used as raw material, and the lime kiln with high energy consumption is eliminated.

(2) The process flow is short, the conversion agent regeneration cycle is realized through crystallization, the operation is easy, and the equipment investment is small.

(3) The high-temperature molten salt reaction contains HCl gas, and the heat energy of the melt and the melt is easy to recycle, and the total energy consumption is low.

(4) The production scale can be large or small, and it is easy to build a clean production and circular economy system. On-site production and on-site use avoid the difficulties in storage and transportation of hydrochloric acid, and even high-temperature HCl dilution gas can be directly chemically absorbed and utilized.

(5) HCl is widely used and can be easily converted into Cl ₂ gas. Under certain conditions, it will be superior to Cl ₂ gas produced by electrolysis, without H ₂ associated, low energy consumption, and small investment.

Description of drawings

Accompanying drawing 1 is to be circulation medium with potassium pentaborate, and Repone K is the technological process of raw material preparation hydrochloric acid and salt of wormwood;

Detailed ways

Take a certain amount of potassium chloride and potassium pentaborate, mix them into solid powder, heat and melt them, place them in a reactor, and pass in superheated steam to react, and the gas phase products after the reaction are condensed after heat recovery to obtain Hydrochloric acid solution. After the reaction, the molten salt is quenched with water and sent to the carbonization tower for carbonation. Carbonation is completed, solid-liquid separation, and washing. The liquid phase KHCO ₃ is thermally decomposed into K ₂ CO ₃ , evaporated and concentrated to obtain the K ₂ CO ₃ product, the solid phase is dried to become anhydrous potassium pentaborate, and returns to the first step; the carbon dioxide obtained from thermal decomposition is recycled;

Example 1

Weigh 4mol KCl (analytically pure, content ≥ 99.5%) and 1mol KB ₅ O ₈ (prepared by mixing KOH and H ₃ BO ₃ ) after drying at 500°C, put them into the reactor after mixing, and heat to 800°C Melt, then feed superheated steam at 200°C, design the steam flow rate according to 10mol steam volume, condense the gas product after reaction, and obtain hydrochloric acid solution. The material quenched by molten salt water is put into a pressurized reactor, and CO ₂ (content ≥ 99%) is passed through, carbonation reaction is carried out at 0.1Mpa, 30°C for 1 hour, and then cooled to 15°C for crystallization; pressurized filtration, solid Dry at 500°C and turn it into KB ₅ O ₈ for recycling. The filtrate is concentrated by heating and thermally decomposed to obtain K ₂ CO ₃ , weighing 265g.

Example 2

Weigh 4mol KCl (analytically pure, content ≥ 99.5%) and 1.1mol KB ₅ O ₈ (prepared by mixing KOH and H ₃ BO ₃ ) after drying at 500°C, put them into the reactor after mixing, and heat to 900°C Melt, then feed superheated steam at 200°C, design the steam flow rate according to 15mol steam volume, condense the gas product after reaction, and obtain hydrochloric acid solution. The material quenched by molten salt water is put into a pressurized reactor, passed through CO ₂ (content ≥ 99%), carbonated at 0.1Mpa, 30°C for 50min, then cooled to 15°C to crystallize; pressurized filtration, solid at 500 °C to dry and turn into KB ₅ O ₈ for recycling. The filtrate was concentrated by heating and thermally decomposed to obtain K ₂ CO ₃ , weighing 260g.

Example 3

Weigh 4mol KCl (analytically pure, content ≥ 99.5%) and 1.1mol KB ₅ O ₈ (prepared by mixing KOH and H ₃ BO ₃ ) after drying at 500°C, put them into the reactor after mixing, and heat to 950°C Melt, then feed superheated steam at 200°C, design the steam flow rate according to 10mol steam volume, condense the gas product after reaction, and obtain hydrochloric acid solution. The material quenched by molten salt water is put into a pressurized reactor, passed through CO ₂ (content ≥ 99%), carbonated at 0.1Mpa, 30°C for 40min and then cooled to 15°C for crystallization; pressurized filtration, solid at 500 °C to dry and turn it into KB ₅ O ₈ for recycling. The filtrate was concentrated by heating and thermally decomposed to obtain K ₂ CO ₃ , weighing 255g.

Claims (6)

1. A method for directly producing hydrochloric acid and salt of wormwood by _{a KCl molten state hydrolysis method is characterized in that potassium chloride and KB 5 O 8 are melted and} mixed with 800 ~ 1200°C, mixing ratio KCl: KB ₅ O ₈ (4: 1 ~ 1.2) molar ratio, and then through hot water steam, hydrogen ions in the water combine with chloride ions to become hydrogen chloride gas, which is mixed with the remaining water vapor after the reaction, After condensation, it becomes a hydrochloric acid solution; the alkali metal borate with a smaller ratio of B ₂ O ₃ /K ₂ O produced by the reaction is quenched in water, and then crystallized after carbonation to generate KB ₅ O ₈ 4H ₂ O. Recycle after drying; carbonation to obtain KHCO ₃ solution, and further processing to obtain K ₂ CO ₃ . 2. a kind of KCl molten state hydrolysis method according to claim 1 directly produces the method for hydrochloric acid and salt of wormwood, it is characterized in that described molten state hydrolysis is when alkali metal chloride is in molten state, passes into superheated Water vapor, for the hydrolysis reaction in the molten state, is called "melt state hydrolysis". 3. a kind of KCl molten state hydrolysis method according to claim 1 directly produces the method for hydrochloric acid and salt of wormwood, it is characterized in that described KB _{5 O} The special property when molten state refers to utilizing KB above 800 ℃ ₅ O ₈ is acidic after melting, which can provide an acidic environment for the decomposition of KCl. 4. according to the method for directly producing hydrochloric acid and salt of wormwood by a kind of KCl molten state hydrolysis method described in claim 1, it is characterized in that described superheated steam is that temperature reaches more than 200 ℃, but pressure is the superheated of normal pressure steam. 5. a kind of KCl molten state hydrolysis method according to claim 1 directly produces the method for hydrochloric acid and salt of wormwood, it is characterized in that described reaction generates B ₂ O ₃ /K ₂ The alkali metal that the ratio of O 3 becomes smaller Borates, including series of K-series borates with a ratio of B ₂ O ₃ /K ₂ O less than 2, mainly K ₂ B ₄ O ₇ . 6. a kind of KCl molten state hydrolysis method according to claim 1 directly produces the method for hydrochloric acid and salt of wormwood, it is characterized in that after described carbonation crystallization regeneration KB ₅ O ₈ 4H ₂ O, carbonation reaction temperature The temperature is 30-40°C, the pressure is 0.1-0.3Mpa, and the crystallization temperature is 10-15°C.

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