Soda ash-Basic information soda ash chemical formula: Na2CO3
Molecular weight: 105.99
Common name: lump alkali, caustic soda, soda ash, and oral alkali (historically, it was generally transported to the whole country through Zhangjiakou and Gubeikou, so it was also called "oral alkali". )
Appearance: white powder or fine crystal (anhydrous pure product)
Taste: astringent
Relative density (water = 1): 2.532.
Melting point: 85 1℃
Classification: strong alkali and weak acid salt * * Note * * (Soda Soda is not alkali, it is salt! )
Chemical properties:
1) solution is alkaline and can react with acid.
2)Na2CO3+2HCl=2NaCl+H2O+CO2
3)Na2CO3 reacts with alkali. Na2CO3+Ca(OH)2=CaCO3↓+2NaOH、na2co 3+2 HCl = 2 NaCl+H2O+CO2↑CaCO3+2 HCl = CaCl 2+H2O+CO2 ↑.
4)Na2CO3 and NaCl react with salt.
Na2CO3+BaCl2=BaCO3↓+2NaCl
Stability: It can be decomposed into sodium oxide and carbon dioxide at high temperature. Long-term exposure to the air can absorb moisture and carbon dioxide in the air, generate sodium bicarbonate and form lumps. Strong hygroscopicity, easy to form lumps, and does not decompose at high temperature. There are three kinds of sodium carbonate containing crystallization water: Na2CO3 7H2O, Na2CO3 7H2O and Na2CO310H2O.
Solubility: soluble in water, slightly soluble in anhydrous ethanol, insoluble in propanol. Sodium carbonate is soluble in water and is a weak acid salt. When it is dissolved in water, it will undergo hydrolysis reaction, making the solution alkaline and corrosive, and it can react with acid to generate corresponding salt and release carbon dioxide.
Preparation: Sodium carbonate prepared in laboratory: 2NaOH+CO2=Na2CO3+H2O. Sodium carbonate existing in nature (such as salt lake) is called trona, which was used as detergent and printing and dyeing in ancient times. 179 1 year, using salt, sulfuric acid, coal and limestone as raw materials to produce sodium carbonate, which is the Nicholas Leblanc method. This method is gradually replaced by Solvi method because of insufficient utilization rate of raw materials, poor working conditions and poor product quality. 1859 Solvay, Belgium takes salt, ammonia and carbon dioxide as raw materials, and at room temperature, sodium bicarbonate is precipitated from the solution, which is decomposed into sodium carbonate by heating. This method has been used to this day. 1943 China Hou combined with the national conditions of salt shortage in China, improved the Suwei process, combined soda ash and synthetic ammonia, and produced sodium carbonate and ammonium chloride at the same time, which greatly improved the utilization rate of salt, so it was a method of soda ash production in Hou Shi. Sodium carbonate is used to produce soap, paper, detergent, flux and water softener in metallurgical industry.
Soda water-basic introduction
Soda soda ash is mainly used to produce glass, such as flat glass, bottle glass, optical glass and advanced utensils; In chemical industry, it is used to prepare sodium salt, metal carbonate, bleaching agent, filler, detergent, catalyst and dye. In metallurgical industry, it is used to remove sulfur and phosphorus, process minerals and produce copper, lead, nickel, tin, uranium, aluminum and other metals; In the ceramic industry, it is used to make refractories and glazes. In addition, industrial gas desulfurization, industrial water treatment, metal degreasing, cellulose and paper production, soap manufacturing and so on also need soda ash.
Soda soda production includes Suwei method, Hou's alkali production method and natural alkali processing method. Because of different processing methods, the raw materials used are also different. The main raw materials are crude salt (including sea salt, pond salt, mineral salt and underground brine), trona, limestone and ammonia.
Suwei process, also known as ammonia-alkali process, was put forward by Belgian E. Solvi in 186 1 (see the history of soda industry development), and it is the most important method to make alkali. This method replaces nicolas leblanc method because it has the advantages of easily available raw materials (raw salt and limestone), continuous production process, large scale, high quality and low cost.
In the process of preparing sodium carbonate from raw salt and limestone, ammonia plays an intermediary role. Firstly, the crude salt is dissolved in saturated brine to remove impurities, and then ammonia is absorbed to make ammonia brine, which is carbonized to get sodium bicarbonate (also known as heavy alkali), and then filtered and calcined to get soda ash. The filtered ammonium chloride mother liquor is added with lime milk for reaction, and the distilled ammonia is recovered, and the obtained distilled waste liquid is discarded. Lime and carbon dioxide obtained from limestone calcination are used to decompose ammonium chloride in mother liquor and carbonize to make alkali respectively.
Hou Shi soda process: also known as combined soda process (see soda industry history). This method overcomes the discharge of waste liquid from ammonia-alkali process, combines soda ash production with synthetic ammonia production, and uses ammonia and carbon dioxide from synthetic ammonia plant to produce ammonium chloride and soda ash only by adding washing salt or high-quality salt into the process. The method produces soda ash 1t and ammonium chloride 1t at the same time, so the salt utilization rate can reach 95%. Production is divided into two main processes, I and II (Figure 2).
The first process: the mother liquor after centrifugal separation of ammonium chloride, called mother liquor M Ⅱ, exchanges heat with the ammonia mother liquor A Ⅰ in the second process. After the mother liquor M Ⅱ is heated, it enters the ammonia absorber to absorb ammonia, and the ammonia mother liquor A Ⅱ is prepared. After clarification, the impurities are removed and sent to the dissolution tower of carbonization cleaning tower to scar and absorb a small amount of carbon dioxide, which is called ammonia washing mother liquor. Sending the mixture to a soda carbonization tower to react with carbon dioxide to generate sodium bicarbonate with low solubility. The heavy alkali (NaHCO3) obtained by filtration and separation is sent to a decomposing furnace for decomposition into soda ash, and the discharged gas containing high-concentration carbon dioxide is cooled and washed by a condensing tower and a washing tower, and then sent to a carbonization tower by a compressor for alkali production.
Second step: filter the mother liquor after heavy alkali, which is called mother liquor M I, and make ammonia mother liquor A I after absorbing ammonia, which is used to clean the scar in the external cooler of crystallizer, and then exchange heat with mother liquor M II in the first step, so that the ammonia mother liquor A I is cooled and sent to the cold precipitation crystallizer, and a part of ammonium chloride is cooled and separated out in the external cooler. The clear liquor at the upper part of crystallizer is called semi-mother liquor, and the semi-mother liquor overflows to the salting-out crystallizer, and the remaining ammonium chloride is added for salting-out.
Natural alkali is the raw material for producing sodium carbonate, sodium bicarbonate and sodium hydroxide. In addition to sodium carbonate, there are minerals such as sodium bicarbonate, sodium chloride and sodium sulfate, and the proportion is uncertain. The common component of trona is Na2CO3 NaHCO3 2H2O. Countries that exploit trona in large quantities include the United States, Kenya, Mexico and the Soviet Union. The United States has the largest output, with 1979 reaching 6.7 mt. There are three processing methods of natural alkali in the United States: ① sodium sesquicarbonate method: the process is to crush, dissolve, clarify, filter, evaporate and crystallize alkali ore, then separate the crystallized Na2CO3 NaHCO3 2H2O, and then calcine and screen to obtain sodium carbonate products. (2) Sodium carbonate monohydrate method: the process is that sodium bicarbonate in alkali ore is calcined and decomposed, then dissolved, clarified, filtered and evaporated to separate out Na2CO3 H2O, and then dehydrated and dried to obtain heavy soda ash. This method is widely used by companies in Green River, Wyoming, USA, and its production process is more complicated than sodium sesquicarbonate method. ③ Direct carbonation of brine: mainly used for brine processing in Sears Lake, California, USA.