Application and preparation of soda ash_industrial additives

Background and overview of the application and preparation of soda ash

Soda ash is also called soda or soda ash. The scientific name is sodium carbonate. White powder or fine particles. Synthetic soda ash began at the end of the 18th century, when France’s N. Loublain invented the Loublain method. In the 1860s and 1870s, Belgian E. Solvay used salt, ammonia and carbon dioxide to produce soda ash, which was called the Solvay method or the ammonia-alkali method. It replaced the Loubrand method and has since become the main method for producing soda ash. In 1937, China’s Hou Debang developed Hou’s alkali production method (now called the combined alkali production method) based on the Solvay method, which can produce soda ash and ammonium chloride at the same time. In 1952, a pilot workshop was established in Dalian Chemical Plant, and in 1964, a joint alkali production industrial unit was officially built. There is another important source of soda ash, which is produced by processing trona. The United States is the main country that produces soda ash from trona. In 1999, the soda ash produced from trona reached 11.135 million tons, accounting for more than 90% of the total output. China and Russia also produce it. In the late 1990s, the world produced 37 million tons of soda ash, and China produced 8.25 million tons of soda ash in 2000 (including 184,000 tons of trona). The glass industry accounts for 50% of the world’s soda ash consumption, chemicals account for 15% to 18%, soaps and detergents account for 10%, and papermaking, water treatment, food, etc. account for 20%.

Applications and preparation properties of soda ash

Soda ash is generally a white powder. It is a colorless crystal containing ten crystal water in the air. However, the crystal water is unstable and turns into white powder at high temperatures. It becomes a strong electrolyte, has thermal stability and is easily soluble in water. , can reach the maximum saturated solubility at 35°C, and the solubility will no longer increase as the temperature increases. The aqueous solution of soda ash is alkaline. Sodium carbonate is a salt of weak acid and strong alkali. The reason why it is called “soda ash” is because the steel carbonate produced by chemical methods in the laboratory is purer than trona. Among the industrial products currently produced in my country, the purity of soda ash is generally 98 %-99%, classified according to the bulk density of soda ash as shown in the table. 

Applications and Preparation Applications of Soda Ash

Soda ash is most commonly used as a basic chemical raw material. It is widely used in industry and has a large demand. In the process of preparing other types of alkalis or inorganic salts and other commonly used chemical products, soda ash is the most common raw material, such as:

1) The lime causticization method can be used to prepare caustic soda. The main raw materials used are square soda ash, heavy alkali, etc. The main process is through the lime causticization method, that is, the metathesis reaction of calcium hydroxide and soda ash is used to produce caustic soda. The overall process saves resources, is easy to operate, and the resulting product is of high quality, and is suitable for small-scale industrial production of intermittent reactions;

2) The carbonation method can be used to prepare heavy alkali (baking soda). Baking soda is a common daily di-tert-butylpyridine product in daily life. It is also an intermediate product in the process of preparing soda ash. Its purity is directly It affects the final soda ash product. In our industry, it is very common to use soda ash carbonation to prepare baking soda. The main method is to pass carbon dioxide into the soda ash solution to obtain sodium bicarbonate, which will precipitate as a slightly soluble substance. The process flow is very simple;

3) In the preparation process of soda ash (sodium silicate), soda ash and clay are also used as raw materials, so that the two react under melting conditions to obtain the product soda ash, which has a wide range of uses and is widely used in national industry. Each part of the system is reflected. For example, caustic soda can be used to prepare various sodium silicate products in the chemical industry system. It is the basic raw material of silicate compounds. In light industry, it is indispensable for washing powder, soap and other detergents. Raw materials can be used for bleaching, dyeing or starching in the textile industry. In addition, they are also widely used in adhesives, refractory materials, etc. in the construction and machinery industries. The preparation method is mainly by mixing soda ash and sand in the Mix the reaction in the molten state, then add water for dissolution and filtration. The process is easy to operate and the output is large. In our industrial system, in addition to the above main uses, soda ash can also be used as an intermediate raw material in the industry to prepare various steel-containing products. , and can be used as an auxiliary material in the production of other chemical products, and has a wide range of uses. Therefore, it is an important indicator to measure the industrial level of a country and marks the industrial level of a country to a certain extent. In recent years, due to the invention of degradable plastics, there have been more and more plastic products. At the same time, the country has increased its efforts to recycle waste glass products. The demand for glass products has gradually decreased and been gradually replaced by plastic products. Therefore, soda ash has played an important role in the glass industry The dosage gradually decreased. However, in developing countries such as my country, soda ash still occupies a very important position. In addition, the wide range of uses of soda ash also determines its important position in the industrial system. In terms of global industrial development, the demand for soda ash will still remain at a high level and will grow slowly in the future.

Application and preparation of soda ash

1. Chemical synthesis method: It is the main method used in the world to prepare soda ash. But before that, there were many other methods of chemically synthesizing soda ash in the world. For example, French doctor Lou Blanc used table salt as raw material to prepare soda ash and obtained a patent. Therefore, this method is called Lou Blanc’s method of making soda ash. The process principle is as follows:

This method is called the Lubulan alkali production method. It can be seen from the chemical reaction equation that the conditions required for the overall process are relatively harsh. At the same time, the waste materials and waste gas generated are difficult to reuse, so this method This method has not been widely used internationally.��.

2. Combined alkali production method: It includes two processes: the first unit is similar to the ammonia-alkali method, which mainly involves continuously flowing ammonia gas into saturated lithium carbonate and brine to obtain ammonia salt water, and then passing carbon dioxide gas through it. When it is put into it, the slightly soluble sodium bicarbonate steel precipitate can be obtained. After filtration and washing, tiny crystals of sodium bicarbonate can be obtained. At this time, the obtained intermediate product steel bicarbonate is sent to the general furnace for calcination. Soda ash products. The clarified filtrate after removing the precipitated ammonium carbonate contains a large amount of sodium chloride and a small amount of sodium chloride, which needs to be treated. This part is the second unit, which mainly processes the sodium chloride crystals to precipitate from the clarified filtrate. . According to the solubility curves of the two substances in water, the solubility trends of hydrogen chloride and sodium chloride vary greatly with temperature. Therefore, the by-product of sodium chloride can be precipitated through concentration and condensation. The seed delivery method can achieve cyclic alkali production, greatly improve the alkali production efficiency, and at the same time overcome the shortcomings of the Solvay alkali production method, and has been widely recognized internationally. However, there are still major problems in the later processing of the chlorination and separation process. It is difficult to properly solve the recycling process of the mother liquor during the circulation process. At the same time, it is difficult to ensure the purity of the chloride, and there is also great pollution in the waste liquid. These shortcomings It greatly limits the development of seed delivery technology.

3. Metathesis method

1) Research progress in preparing soda ash by metathesis method

Through the research on the alkali production by the metathesis method of ammonium carbonate and sodium chloride, it is concluded that this method cannot produce two pure products at the same time. Whenever salts are synthesized by the metathesis method, if you want to obtain two pure product salts, from From the perspective of the phase diagram, the following two conditions must be met: From the analysis of the metathesis phase range, the two raw material salts should be a pair of relatively unstable reactants, which can completely react to obtain pure products, and the two obtained The products should be two relatively stable salts. When selecting ammonia carbonate and sodium chloride as the raw materials for the reaction, these two raw materials meet the above requirements and meet the conditions when performing the metathesis reaction. It is necessary to use two temperatures, one high and one low, to produce two products at the same time. Through phase diagram analysis, when at these two temperatures, the solubility phase diagram of the selected unstable salt needs to change significantly. This facilitates the separate precipitation of one product at high temperatures; while the other product can be easily separated at low temperatures. When Na+, NH4+/HCO32-, and Cr are added to 50°C to prepare soda ash and chlorinated steel through double decomposition, it can be seen from the phase diagram that the boundary position of the phase zone between chlorinated sodium and carbonated steel will basically not change. , in addition, in the high-temperature phase region and the low-temperature phase region, the phase boundaries of the two substances overlap. This makes it relatively difficult to prepare two pure product salts at the same time.

2) Intermediate salt method

Using the sulfuric acid intermediate salt method, a metathesis method alkali production device was built at the Yongan Synthetic Ammonia Plant in Fujian Province. This method adds concentrated sulfuric acid to the mother liquor after the precipitation of sodium bicarbonate to remove HCO3- in the mother liquor, which can prevent the precipitation of sodium chloride. The precipitation of sodium ammonia carbonate during the process. However, when adding concentrated sulfuric acid, a large amount of heat is released after adding concentrated sulfuric acid, resulting in a large amount of smoke and a poor environment.

3) Room temperature crystallization method

The room temperature crystallization method is improved on the basis of the sulfuric acid intermediate salt or nitric acid intermediate salt method, and the intermediate salt is directly added to the mother liquor, so that the chloride can be directly precipitated. In the process, the process section of cold separation after concentration is omitted, the process flow is simplified, the cost is saved, and the competitiveness of preparing soda ash by metathesis method is improved.

4) Other process improvement methods

Commonly used production methods can be used to reduce the salt contained in soda ash when preparing soda ash in the current soda ash industry. The first one can use a heavy alkali centrifuge to perform a secondary dehydration process on the sodium ammonia carbonate precipitate obtained by filtration. The second one can The second is to modify the washing device of the alkali filter machine, and the third is to improve the washing process, that is, adding more washing steps. The principle of these measures is to remove the carbonic acid contained in the precipitate of ammonium carbonate steel by increasing the energy efficiency of the washing process. The salt component makes the impurity salt content in the final soda ash product less than 0.4%. 