Analysis and Comparison of Vacuum Dechlorination Process of Light Salt Water
1 Overview Dilute brine dechlorination process is an important part of the ion-exchange membrane alkali plant, containing free complex dilute brine + corrosion only metal equipment and pipelines, but also damage the brine filter carbon sintering tube permanent toxic ion exchange resin, etc. Therefore, dechlorination must be performed before the heavy salt water is saturated. The equilibrium solubility of chlorine in dilute salt water 8 can be used as follows: 1 dl of the common phase for warm salt water, and also for dilute salt 1; it can be known from the formula 1 with the following simple formula. Chlorine in dilute brine solution in light salt water and chlorine in du light brine from the test of light salt water temperature 1 and light salt 1 value of the light salt water in the NaC content of N from the anode compartment of the electrolyzer tank salt water long-term performance by ion membrane Operational requirements. Its heart content needs to be controlled at 200 1.2 Dilute salt water temperature Ding-membrane electrolyzers To maintain a low cell voltage and long-term stable operation, the operating temperature must be controlled at 85 ± 3 1.3 Dilute brine directly in the anode compartment of the cell, chlorine dissolved in The following chemical reactions occur in dilute salt water. Since 0 is not easily removed in dilute brine, hydrochloric acid must be added to dilute brine, and the dilute salt water 1 value should be controlled at 20±0.25 to convert muscle 10 into easily dissociated 02 free chlorine. The above analysis. To reduce the equilibrium solubility of gas in dilute brine, that is, the free chlorine test, the method of reducing the partial pressure of chlorine should be used. 2 Light salt water dechlorination method Light salt water dechlorination method can be divided into physical methods and chemical methods. In actual production, dechlorination of dilute brine is to remove most of the free chlorine first by physical methods, and then to remove residual free chlorine by chemical methods. 2.1 Physical Methods The physical method is to remove most of the free chlorine in dilute brine by reducing the partial pressure of chlorine gas. It is divided into two types: positive pressure blowing method and vacuum stripping method. 2.1.1 Positive Pressure Blowing Method Positive Pressure Blowing Method Tower drum people clean air. In order to reduce the partial pressure of the gas phase in the column, and the solubility in free salt water, most of the free chlorine contained in the light salt water is blown out. Because the dechlorinated exhaust gas generated contains a large number of processes, the lye is absorbed and discharged after reaching the standard. Although this method has the advantages of short process, low investment, easy operation, etc., it needs to eliminate 1 Zheng Yuan senior engineer. Director. He graduated from Chengdu University of Science and Technology in 1982 and majored in inorganic chemistry. He was directly involved in design and management. He contacted 028 lye and increased the load of exhaust gas treatment. The disadvantages of the gas that cannot be recycled into the chlorine system, such as the escape of gas, are no longer used today. Especially in humans, ion waves are gradually eliminated in caustic soda devices. 2.1.2 Air Dechlorination At present, the dechlorination process of dilute brine in ion-exchange membrane caustic soda plant is commonly used vacuum dechlorination. The principle is that under the vacuum condition, the partial pressure of chlorine is reduced, thereby reducing the equilibrium solubility of chlorine in the dilute brine to achieve the purpose of removing most of the free chlorine contained in the dilute brine. Vacuum dechlorination method according to the preparation of vacuum can be divided into mechanical vacuum method and jet vacuum method. 1 mechanical vacuum method to mechanical vacuum pump to form a light salt water vacuum system, the process flow 1. In the electrolysis process, the agricultural pale water is transferred to the upper part of the dechlorination column at the acidification plant. The dechlorination tower has a vacuum of approximately 50. The free chlorine in the dilute brine is cooled in the air and cooled by the chlorine cooler. After being separated by a liquid ring vacuum pump and separated by a separation tank, the chlorine gas is sent to the chlorine main pipe for recovery. Chlorine water from the chlorine gas cooler and the separation tank overflows to the chlorine tank. After the dechlorinated dilute brine free chlorine is about 1 called from the bottom of the decoction tower directly into the dechlorinated brine by the tank, dechlorinated salt water pump in the pump before adding palpitation lye and control the pressure after the 9.010. Addition of 1233 to completely remove free chlorine in dilute brine = The advantage of adopting mechanical vacuum method is that vacuum system operation is relatively stable, and energy consumption is about 61 base is relatively low. However, since the liquid ring vacuum pump uses the chlorine water circulation as the working medium, the vacuum pump can easily be deflected and pollute the environment if the packing is sealed. If the mechanical seal is used, the mechanical sealing performance of the domestic titanium vacuum pump is not long enough to ensure long-term stability. Run, and 34 times, in addition to its long process, a larger area. The jet vacuum rule uses a jet vacuum pump as the motive force to form a vacuum system. The vacuum method using steam as the working medium is widely used. The process flow is controlled by the electrolyzer's light salt water after acidification. In addition to the free chlorine in the light salt water, the dechlorination vacuum degree is about 50, and the chlorine gas passes through the chlorine gas. After the cooler is cooled, it is pumped by steam and pumped to the steam condenser. In the steam condenser, the chlorine and steam are cooled and separated by the cooling water. The chlorine is sent to the chlorine manifold for recovery, and the chlorine cooler and steam condenser are Chlorine water overflows back to the chlorine tank. After the dechlorinated dilute brine contains about 30 free, called from the bottom of the dechlorination tower directly into the dechlorinated salt tank by the tank, the dechlorination salt water pump in the pump before adding lye 0 and control 庳 = 9.010 pressurization, then add The advantages of using the steam injection method to remove the free water from the brine in a thorough manner in the treatment of 12,3 are the compact equipment layout. Less floor space. However, this method requires a working steam pressure of about 3921 and a stable flow rate. Because the operating temperature of the steam condenser is about 130140, the material requirements 1 and 1 alloy, and the steam injection pump is made of titanium, the total investment is large, and the energy consumption is about chlorine water. Vacuum process process for working medium 3. Chlorine water jetting method is a new process in domestic demineralization process of dilute brine. Our company is responsible for the engineering design of Shandong Binhua, and all the technical indicators have reached the design requirements. The light salt water from the Sui Jun process is used to acidify the yang! 20 from the upper part of the dechlorination tower, under vacuum conditions to remove light salt water free chlorine dechlorination vacuum about mountain helium directly from the water jet pump suction and then into the chlorine sink. Palm, Chlorine sink separated into chlorine total bamboo to be collected. The water is cooled by chlorine, cooled by the chlorine water cooler and recycled to the chlorine water jet pump as the working medium. The dechlorinated dilute brine containing free chlorine was 10 mg of dechlorinated salt water before adding the lye to the pump before the pump, and 1 helium; Yang = 9.00 after the pressurization, and then adding 8,3 to completely remove the free chlorine from the dilute brine. In the gas system, there is a gas return line and pressure regulating valve whose main function is to adjust the amount of chlorine in the hydrophobic injection pump under the condition of no operation load. To detect the degree of stability. The advantage of using the chlorine water jet method is to allow the use of a caustic soda unit to treat the chlorine tip and the chlorine water pump dislocation of the D-sequence. 1 The order is arranged in the same frame, the floor area is the minimum, the process flow is short, the equipment operating conditions are mild, the structure of the chlorine water injector made of titanium is simple, and the total investment is easy to operate. The disadvantages are that the energy consumption is relatively high. 2.2 Chemical methods Chemical methods Chemical methods Physical methods Add melamine-like lye after bleaching and make it technically speaking = 9.5 soil 0.5. Into the mouth as excessive 2 times the theoretical amount of reducing agent as he 25, 3 and pale In the salt water, the free enthalpy is lower than the free enthalpy in the dilute salt water. The mechanical vacuum method uses the liquid helium as a power source for vacuum. Although the degree of vacuum is stable, the energy consumption is relatively low, but its The process flow is longer, the area is larger, and the investment in equipment is higher. There are also promotional values ​​in larger installations. The steam injection method is powered by steam injection. During operation, the vacuum fluctuates with fluctuations in the steam pressure and flow rate, and the instability of the vacuum affects the dechlorination effect, adding difficulty to the subsequent treatment of free chlorine, and increasing the consumption of sodium sulfite. At the same time, the energy consumption of this method is the highest, the consumption of steam per ton of alkali is about 50, the material requirement of the steam injection pump is high and the working temperature of the steam condenser is higher at about 130,140. The alloy material used requires a high total investment. Therefore, the law does not promote it. Chlorine water jet method is powered by chlorine water jet, and the vacuum degree is stable. The method has a simple process flow, a small footprint, and easy operation control. Ji Ji times investment is low, and the full amount of advanced receipts will reach the end of the 40th page. 4 Conclusion 851 Urea equipment can be used as a base lotion, in addition to the stripper scale. The best cleaning conditions are temperature 120140 detergent concentration 15, initial acidity 1 of the cleaning solution, and amount of umbrella additive (1). Using the above-mentioned cleaning conditions, the equipment descaling rate reached 0.01. It was far lower than the 1012 standard set by the Ministry of Labor and the Ministry of Labor's Low 1 Silver Oven Chemical Cleaning Rule. The cost of cleaning 1 scale method. It can be used in various types of prime equipment. In particular, leg-sole sings are compiled. Large Nitrogen Fertilizer Supplement, 1983, 57, 60 2 Pan Yukang. Chemical cleaning of urea plant fouling, the 7th Annual Technical Conference of the National Large-scale Urea Plant, 199382, 84 Corrosion rate of equipment during the cleaning process was 0.002.
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