Process and gas-film air tower for treating hydrazine contained sewage generated in production of azodimethylamide

Abstract

A process for treating the hydrazine-contained sewage generated during production of azodimethylamide features use of a gas-film air tower, and includes such steps as deposition, introducing supernatant to a pre-treater, adding calcium carbide dregs or lime, blowing-oxidizing in the gas-film tower, defoaming tail gas, cyclone separation, heat exchange, adsorbing by sulfuric acid in an absorption tower, exhausting tail gas, press-filtering of oxidizing liquid from the said gas-film tower, biochemical homogenizing, mixing with city sewage, anaenbic biochemical treating, depositing, and aerobic biochemical treating. Its advantages are no environmental pollution, and low cost.

Description

technical field [0001] The invention relates to a method for treating hydrazine-containing wastewater produced in the production of azodicarbonamide and a gas film stripping oxidation tower. Background technique [0002] Azodicarbonamide (AC) foaming agent and modified compound products are foaming aids used for foaming various plastic and rubber products such as PVC, PE, ABS, and SBS. Because it is non-toxic, odorless, and pollution-free, it can be used for all kinds of soft and hard plastics, so it has become the most important foaming agent for plastic and rubber products today. The production of azodicarbonamide foaming agent in my country began in the 1960s. So far, there are more than 30 manufacturers, covering Jiangsu, Shanghai, Zhejiang, Fujian, Guangzhou and Yunnan. In 2000, the national production of azodicarbonamide was about About 60,000 tons, it is the country with the largest output in the world, accounting for about a quarter of the w...

AI Technical Summary

Problems solved by technology

The advantage is: the treatment process is simple and the investment is low; the disadvantage is: in the process of wastewater treatment, due to the release of chlorine gas, it is easy to cause secondary pollution and equipment corrosion. In addition, a large amount of sulfate radicals still remain in the water, so that the wastewater cannot be discharged up to the standard, and it is not easy to biochemically treat

This method is developed by Nanjing University, and only simulated wastewater treatment test is carried out. The test results show that the removal rate of ammonia nitrogen can reach 97%. The problem is that the actual azodicarbonamide (AC) wastewater test has not been carried out, and the CODcr The treatment of pollutants such as hydrazine and hydrazine is basically ineffective, and the salinity of the effluent is higher, so further treatment is required. In addition, a large amount of sodium carbonate is consumed and ammonia water is added, so the treatment cost is high

The disadvantages are: long recycling process, large investment, high energy consumption, high operating cost, and no market for recycled products

The main problem is: the effluent cannot directly meet the standard, basically has no effect on the salt and sulfate radicals in the water, and the cost of small-scale treatment is as high as more than 100 yuan per ton of water

Its advantages are: the process is simple, and the existing biochemical sewage treatment plant can be used for treatment; its disadvantages are: the dilution factor of wastewater is too large, and the cost of engineering bacteria is very high at one time and needs to be continuously replenished

Problems in this method: 1. The gas-liquid ratio is very high, which not only consumes a lot of energy, but also has high processing costs, and also brings difficulties in the absorption of tail gas. The ammonia nitrogen discharged from the tail gas increases, and the total removal rate decreases; 2. The effluent has not yet reached the standard. , the further treatment measures are not pointed out in the text; 3, the text points out that the sieve plate column has an amplification effect, so it can be predicted that if a multi-stage sieve plate column is used, the stripping effect will be further reduced; 4, the test water and azo The actual wastewater produced by diformamide has a big discrepancy. There is no research on hydrazine hydrate, sulfate and salt. If the above method is used to treat azodicarbonamide nitrogen-containing wastewater, the ammonia nitrogen in the effluent is still as high as several hundred milliliters or more. , the CODcr geometry has not been reduced, it is necessary to carry out secondary treatment on the effluent, but due to the presence of hydrazine and salt, etc., biochemical treatment is almost impossible

5. Since the mass transfer and heat transfer are very different between the first-stage sieve tray tower and the multi-stage sieve tray tower, for the multi-stage sieve tray, the higher the upper layer of the sieve tray, the higher the concentration of ammonia in the gas phase, which promotes The smaller the force is, as the concentration of ammonia in the wastewater increases, the concentration of ammonia in the outlet gas at the top of the tower will also increase, and the gas-liquid ratio must be greatly increased. However, due to the limitation of the space velocity of the tower, the air volume cannot be greatly increased, which will cause treatment effects. seriously deteriorated

[0021] method Principle of action advantage There is a problem bleaching powder oxidation Law using bleaching powder or bleaching powder hypochlorite in water acid, and release new eco-oxygen and chlorine, so that organic matter untie 1. Treat waste with waste, low processing cost 2. CODcr removal up to 78% 1. The effluent cannot meet the standard 2. Easy to cause secondary pollution 3. The equipment is easy to corrode 4. Removal rate of ammonia nitrogen, salt, etc. Low handling is more difficult Pipeline lowering device for oil drilling

Absorption - stripping Law Using Modified High Energy High Score subabsorbent and air stripping Combined desulfation and ammonia 1. Simulation test off Ammonia rate up to 97% 2. Recyclable sulfuric acid Ammonium 1. To remove CODcr and hydrazine Basically no effect, the water is still not up to standard 2. Higher salt content, biochemical possible 3. Extensive consumption of sodium carbonate and Ammonia, high processing cost Crystallization - Concentration Law Production of Chlorine by Alkali Process The principle of ammonium chloride, for hydrazine Various inorganic substances in wastewater 1. Recycling waste water sodium sulfate, sulfuric acid ammonium, sodium chloride 1. Recycling process length and investment Large, high energy consumption, processing costs expensive salt for recycling 2. Wastewater closed loop the ring 2. Recycled products have no market 3. Waste water return system to product The impact of quality cannot be ignored No diaphragm solution Using electrolysis and electrolytic production Raw hypochlorous acid and nascent Oxygen Degradation Wastewater of organic matter 1. The equipment is simple and easy to operate for convenience 2. Small test results, CODcr and ammonia nitrogen drop The solution rate can reach 90% 1. The effluent cannot be discharged up to the standard, still needs further processing 2. Expensive treatment costs, tons of water More than 100 yuan photocatalytic oxygen chemical method Excited by near-ultraviolet light Generated hole-electron pair Reacts with organic matter in wastewater should, so as to achieve the degradation of Purpose 1. The process is simple 2. Degradation effect on threat better results 3. Low processing cost 1. For CODcr, ammonia nitrogen, salt The degradation effect is not good, and the water Unable to meet the standard, still need a second treatment reason 2. The response time is long, and the equipment Large investment H·S·B Worker Bacteria biochemistry Law using specially engineered bacteria to In addition to ammonia nitrogen, hydrazine, CODcr Wait 1. The process is simple and easy to operate convenient 2. A certain concentration , the removal rate is higher 1. Wastewater requires dilution multiples larger 2. One-time cost and compensation of engineering bacteria high charging cost 3. The effluent is not up to standard air stripping Law Using a pair of sieve tray columns Nitrogenous wastewater for stripping The removal rate of ammonia can reach 90% 1. The effluent cannot meet the standard 2. Cannot adapt to high concentration wastewater 3. High gas-liquid ratio, high energy consumption

[0022] To sum up, the existing problems of the prior art are mainly: 1. The treatment effect is single, and discharge up to the standard cannot be achieved; complex, high investment

3. The above-mentioned technologies often only work on one or two kinds of pollutants, and cannot change the difficult biochemical properties of wastewater, and cannot use biochemical methods for secondary treatment

Images