Hydrogen chloride purification technology
First, the background generated by the technology
High-purity hydrogen chloride is an important material for silicon wafer etching, passivation and epitaxy in integrated circuit production, and can also be used in metal smelting, optical communication and scientific research. With the development of large-scale integrated circuits, the requirements for the purity of hydrogen chloride are getting higher and higher, and the content of impurities is becoming more and more demanding. In particular, the content of hydrocarbons and carbon oxides is strictly limited to prevent wafer processing. The formation of C in the process. There are many manufacturing methods for high-purity hydrogen chloride in China.
Second, the technical type of high purity hydrogen chloride
1. Desorption method
Prior to the 1970s, the preparation of high-purity hydrogen chloride for the electronics industry was carried out by adding concentrated sulfuric acid to concentrated hydrochloric acid to absorb the water therein. It is a supersaturated hydrogen chloride gas which is precipitated. After the 1980s, the preparation method was developed to react with concentrated potassium sulfate and dried potassium chloride to form a high-purity hydrogen chloride gas, which was pressed into a cylinder with a compressor. That is, the Mannheim method potassium sulfate co-produces hydrogen chloride gas. The purity of the hydrogen chloride gas in this method is 99.9% (mass fraction) or more. The domestic process is: using potassium chloride and 98% concentrated sulfuric acid as raw materials, adding to the Mannheim furnace in a ratio of 2:1 (molar ratio), indirect heating by dry gas combustion to make the material in the furnace 500~ At a high temperature of 600 °C, the molars are continuously stirred and mixed to make the reaction sufficient. The generated potassium sulfate enters the closed cooler through the discharge port, and a small amount of free sulfuric acid is neutralized with lime, and then crushed, cooled, sieved and packaged. The finished product, the hydrogen chloride gas generated in the reaction is introduced into the absorption process by the fan. The hydrogen chloride gas passes through the air cooler and the cooling scrubber. After the washing tower is indirectly cooled by the circulating water and washed with concentrated hydrochloric acid, it is cooled and the impurities are removed. The purified hydrogen chloride gas is taken from the desorption step by 21% in the falling film absorption tower. The hydrochloric acid absorbs 35% of concentrated hydrochloric acid, and a part of concentrated hydrochloric acid is used for washing, and the rest is sent to a desorption step for desorption. The 35% concentrated hydrochloric acid sent from the absorption process is controlled by the flow meter to enter the top of the analytical column, and exchanges heat and mass with the 120 ° C hydrogen chloride liquid mixture from the reboiler to decompose the hydrogen chloride gas in the concentrated hydrochloric acid until The bottom of the column and the reboiler reach the equilibrium state of the azeotrope. The desorbed hydrogen chloride enters the condenser and the cooler from the top of the desorption column, removes most of the water, and enters the concentrated hydrochloric acid separator. After further removing the acid mist, high-purity hydrogen chloride gas is obtained, and 21% of the diluted hydrochloric acid at the bottom of the column is analyzed. The reboiler enters the desorption function, and the rest is cooled by the cooler and sent back to the absorption process as an absorption liquid to absorb hydrogen chloride gas.
2. Hydrochloric acid desorption method
The concentrated hydrochloric acid is placed in a decanting column to be heated and decomposed to produce hydrogen chloride gas. The high-purity hydrogen chloride produced by the hydrochloric acid desorption method is widely used in the production of PVC, chloroprene and high-purity hydrochloric acid. The purity of the hydrogen chloride gas produced by the method is above 99.9% (mass fraction), and the process flow is: pumping concentrated hydrochloric acid in the concentrated hydrochloric acid storage tank to the desorption column with a concentrated acid pump, and connecting the reboiler at the lower part of the desorption tower, The acid is sprayed from the top of the tower and counter-current heat transfer with the dilute hydrochloric acid vapor from the reboiler to dehydrogenate the hydrogen chloride. A portion of the resulting azeotrope is replenished by the reboiler and a portion is passed through the cooler to the dilute acid storage tank. The water-containing vapor hydrogen chloride gas from the decanting tower enters the graphite tube cooler and is cooled by water and then passed through a cyclone to separate the entrained acid mist. Then, after a series of normal temperature, low temperature drying, adsorption removal of water and carbon dioxide, compression to 1.2 MPa, low temperature rectification, and then low temperature adsorption nitrogen removal, compressed to 4.2 MPa, bottling.
3. Synthesis method
The combustion reaction of hydrogen chloride in a synthesis furnace to generate hydrogen chloride gas was proposed in the early 1980s to adapt to the rapid development of China's electronics industry, and is a relatively advanced method in technology. The purity of the hydrogen chloride gas produced by this method is above 99.99% (mass fraction), and the process flow is as follows: the raw material hydrogen is sent from the hydrogen press of the hydrogen treatment process, and after passing through the hydrogen buffer tank, the flame arrester enters the bottom of the steel synthesis furnace. The burner (commonly known as quartz lamp cap or just casing lamp cap) is ignited and burned. The chlorine gas of the raw material is pressurized by the chlorine press of the chlorine treatment process, and then sent to the buffer tank, and enters the inner tube of the lamp base of the synthetic furnace at a certain molecular ratio, and is uniformly mixed with the hydrogen of the outer casing through the inclined hole on the lamp cap from bottom to top. . The combustion flame temperature reached 2000 left °C right, and released heat and light, the normal flame was blue-white. The synthesized hydrogen chloride gas is cooled by the cooling water of the synthesis furnace jacket. When the outlet temperature of the synthesis furnace is lowered to 400-600 ° C, it is naturally cooled by an air cooler, cooled to 100-150 ° C, and further cooled by a graphite separator into a graphite cooler. The cooled hydrogen chloride gas is removed from the lower portion of the graphite cooler, and enters the acid mist separator to further remove hydrochloric acid droplets in the hydrogen chloride gas. The hydrogen chloride gas from the synthesis furnace is usually dried at a low temperature and a low temperature, and is adsorbed and purified. The mixture is cooled at a low temperature and a low pressure to remove non-condensable gas impurities, and is bottled in a liquid state.
4. Industrial by-product acid extraction method
With the gradual popularization of the hydrochloric acid desorption method, the process of producing hydrogen chloride by by-product acid extraction has been widely used in production. It is a by-product hydrogen chloride which is absorbed by the dilute acid in the absorption of organic chloride in the adiabatic absorption tower. After concentration, it is desorbed into the analytical column to desorb a high concentration of hydrogen chloride gas. The purity of the hydrogen chloride gas produced by this method is above 99.99% (mass fraction). The process is as follows: the by-product hydrogen chloride is countercurrently contacted with 20% dilute hydrochloric acid sent by the dilute acid pump through the packed adiabatic absorption tower, and the by-product hydrogen chloride is made into hydrochloric acid by adiabatic absorption. More than 31% of the concentrated acid can be obtained from the bottom of the tower, and the dilute acid is preheated by the graphite heat exchanger to enter the concentrated acid tank, and sent to the packed or plate type analytical tower by the concentrated acid pump. The material discharged from the bottom of the tower is analyzed by a reboiler connected thereto, and heated by externally introduced steam, hydrogen chloride and a small amount of water vapor are evaporated, and heat and mass exchange are performed with concentrated hydrochloric acid flowing downward from the top of the column, and the acid is exchanged. The hydrogen chloride gas is desorbed out. The hydrogen chloride gas enters the graphite primary cooler from the top of the tower, is cooled to room temperature by the external cooling water, enters the graphite secondary cooler, is cooled to 12-18 ° C with chilled brine, and is removed by the acid mist collector. Acid mist. The dilute acid coming out from the bottom of the analytical column is an azeotrope of hydrogen chloride and water with a volume fraction of 20-22%. After heat exchange with a dilute acid cooler or concentrated acid, it is cooled to below 40 ° C and enters a dilute acid tank. The pump is sent to the absorption tower and absorbed to obtain concentrated acid.
5. Petrochemical by-product hydrogen chloride purification method
At present, the application of electronic grade hydrogen chloride has been produced, and the hydrogen chloride content reaches 99.999%. The main purpose is to prepare high-purity hydrogen chloride by using petrol chemical by-product hydrogen chloride as raw material. Petrochemical by-product hydrogen chloride gas, low moisture content, basically no corrosion to stainless steel and carbon steel, but usually contains up to 100ppm or more of ethylene and acetylene impurities. For the purification of such gas, rectification or adsorption is usually adopted, but since the boiling point of acetylene and ethylene impurities is close to the boiling point of hydrogen chloride, it is difficult to remove by distillation, and the adsorption process is cumbersome. A cumbersome replacement of the adsorbent is required, and the production cost is high. A preferred method is to convert acetylene and hydrogen chloride into corresponding corresponding halogenated hydrocarbons having a relatively high boiling point relative to hydrogen chloride in the presence of a hydrogen chloride reaction catalyst, and then separating and removing the reaction product. The purity of the hydrogen chloride gas produced by this method is above 99,998% (mass fraction). Reaction process: trace amounts of acetylene and hydrogen chloride are reacted in a gas phase on a catalyst having mercuric chloride as an active component to form vinyl chloride. Main reaction:
Reaction mechanism: acetylene is first reacted with mercuric chloride to form an intermediate product of vinyl chloride chloromer:
Vinyl chloride chloromercury is unstable and reacts with hydrogen chloride to form vinyl chloride
After the raw material gas is subjected to a pretreatment process such as filtration, water removal, compression, distillation and purification, 3.0N chemically pure hydrogen chloride is produced, that is, a raw material for producing electronic grade hydrogen chloride. After the raw material is flashed, the unsaturated hydrocarbon is removed by catalytic reaction, and the light components N2, O2, Ar, CH4 and heavy components H2O, C2HnCIm and the like are further removed by distillation to obtain 4.8N electronic grade hydrogen chloride product. . The product is used as a raw material, and then a 5.0N hydrogen chloride product is produced by flashing, reacting, rectifying and producing.
Third, our company's high purity hydrogen chloride technology
The deionization process designed by our company has a purity of 99.99% (mass fraction) of hydrogen chloride gas. The process is as follows: concentrated acid is pumped from concentrated acid to packed or plate desorption tower. The material discharged from the bottom of the desorption column is heated by the externally introduced steam by the reboiler connected thereto, and hydrogen chloride and a small amount of water vapor are evaporated to exchange heat and mass with the concentrated hydrochloric acid flowing downward from the top of the column. The hydrogen chloride gas is desorbed out. The hydrogen chloride gas enters the graphite primary cooler from the top of the tower, is cooled to room temperature by the external cooling water of the tube, enters the graphite secondary cooler, is cooled to 12-18 ° C with chilled brine, and is removed by the acid mist collector. The acid mist is further subjected to wet dehydration and solid drying to obtain a purity of hydrogen chloride gas of 99.99% or more. The dilute acid coming out from the bottom of the desorption column is 20-22% hydrogen chloride and water azeotrope. After heat exchange with dilute acid cooler or concentrated acid, it is cooled to below 40 °C, enters the dilute acid tank, and is pumped by dilute acid. Into the synthesis tower and then absorb the hydrogen chloride system to take concentrated acid, dilute acid recycling, no waste.
Fourth, the development prospects of technology and the development trend of technology
The preparation process of hydrogen chloride by desorption method and hydrochloric acid desorption method is simple and can be produced on a large scale, but the purity of the prepared hydrogen chloride gas is low, and it is increasingly unable to meet the requirements of the electronics industry, especially integrated circuits. The hydrogen chloride gas produced by the synthesis method has high purity, but the water content is high, the corrosion is serious, the equipment requirements are high, and the production cost is high. Considering environmental protection and recycling of industrial by-products, the purification of petrochemical by-products to produce high-purity hydrogen chloride is an irresistible trend, and this method does not require the addition of reaction medium, thereby avoiding the introduction of other impurities, and the operation is simple and the production cost is low. As the electronics industry is moving toward large size, high integration, high uniformity and high integrity, high-purity hydrogen chloride has been widely used in the preparation of large-scale integrated circuits, so we need to prepare and produce high-purity hydrogen chloride. Further research and improvement of the process
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