Emission Of Tail Gas From Acid Hydrolysis Reaction In Titanium Dioxide Production

In the current acid hydrolysis reaction of titanium dioxide produced by the sulfuric acid method, a large amount of exhaust gas is produced as a source of pollution that has not yet been effectively controlled in the domestic titanium dioxide industry. China’s titanium dioxide enterprises have greater environmental pressure and higher processing costs.
In the production of titanium dioxide by the sulfuric acid process, the acidolysis reaction is a fierce exothermic reaction, which is characterized by a short main reaction time, a high reaction temperature, and a large exhaust volume per unit time. The composition is that the suddenly vaporized water vapor entrains a large amount of acid mist and a small amount of SO3, SO2, and mineral dust.The treatment of the exhaust gas has special requirements for the equipment, pipelines and machinery in the treatment device due to the explosiveness, instantaneousness and corrosivity. Increased equipment investment costs and governance difficulties. In order to solve the above problems, our company’s acid digestion pot (acid digestion pot ¢ 6 m × 11 m, diameter of the lower half of the chimney ¢ 2 m, diameter of the upper half ¢ 1.2 m) is taken as an example to transform from the following aspects.
1. Acid digestion pot and equipment
Because the acidolysis conditions in the acidolysis pot are very harsh and the corrosion is serious, in order to prevent equipment corrosion and perforation, leakage and pollution of the environment and endanger the health of the operator, the effect of improving the insulation layer of the acidolysis pot and enhancing the impermeability of the water glass cement is extended The key to equipment life. The compound anticorrosion scheme of rubber lining combined with KPI cement lining porcelain can prolong the service life of acid digester equipment. The treatment method of acid hydrolysis tail gas is the alkali water spray method, which mainly relies on a large amount of alkali water to condense the condensable water vapor and absorb acid mist, which consumes a lot of water, so the equipment modification requirements for acid hydrolysis tail gas are as follows: Install an inspection and maintenance platform at the outlet of the chimney of the acid digestion pot at 2 meters and 4 meters, and install 4 sets of sprinkler heads (2 nozzles per group) at 1.5 meters and 3 meters. Two 500m3 / h and one 300m3 / h circulating water pump are connected to feed water. After the transformation, the spray volume basically covers the chimney outlet, so that a large amount of acidic high-temperature exhaust gas cannot be directly discharged, and its concentration is diluted to achieve the standard discharge. After the equipment renovation is completed, the number of repairs of the equipment itself is reduced; corrosion of the surrounding equipment, workshops, and pipelines is also reduced, which greatly reduces the maintenance workload for them; and saves hundreds of thousands of yuan in maintenance costs for the enterprise every year.
Second, circulating water temperature
In order to reduce costs, the spray water used is circulating water, because the higher temperature of the circulating water in the acid hydrolysis tail gas tank (80 ℃ -90 ℃) will not achieve the cooling and neutralizing effect; therefore, the secondary return after treatment by this unit water treatment company The water (35 ℃ -40 ℃) is led to the low temperature pool, and the return water of the gas stove (20 ℃ -25 ℃) is also introduced into the low temperature pool. The circulating water is pumped to each sprinkler for spraying, which makes a large amount of acidic high-temperature tail gas fall back when it meets cold, and the neutralization reaction between the alkali in the circulating water and the acid in the tail gas reduces the harmful substances in the discharged water vapor To the purpose of energy saving and reducing environmental pollution. The yellow smoke above the factory area was turned into white smoke, and the surrounding villages could no longer smell bad odors, which significantly improved the production and ecological environment in and around the factory area.
III. Recovery of spray water
In order to save costs, the sprayed falling water first falls into the recovery tank at the bottom of the chimney, and then is sent into the high-temperature tank by the pipeline, and then sent to the water treatment company through the high-temperature tank for treatment. In order to prevent the diffusion of harmful gases in the high-temperature pool, we added a triangular cover to the high-temperature pool to avoid the emission of harmful water vapor in the pool and ensure that the recovery rate of acid water reaches 98%; another overflow port is made between the low-temperature pool and the high-temperature pool So that the water levels between the two pools complement each other to maintain balance. In this way, almost all of the water is added to the cycle, which can save more than 300,000 tons of water for enterprises every year. This alone can save more than 700,000 yuan for enterprises.
The operation results show that the pollutants of the exhaust gas after treatment can reach the national emission standard, the sulfuric acid mist emission concentration is 260mg / m3, the exhaust temperature is 47 ℃, and the efficiency of the purification system reaches 96%