As a manufacturer of mineral processing of inorganic chemical products, titanium white powder, it should be said from the beginning of 1918 sulfuric acid method, chloride method to study industrial production until 1958, always accompanied by a large number of sub-processing of the waste problem. Regardless of the sulfuric acid process or the chlorination process, the separation process is the essence of inorganic chemicals. As we all know, the international standards corresponding to quality, environmental protection and health are ISO 9000, ISO 14000 and ISO 18000; this is the inevitable result of social progress. In the 1980s, the quality of sulphuric acid titanium dioxide and chlorinated titanium dioxide production in developed countries has satisfied the development of applications and synchronized with them. In the 1990s, green movements, environmental regulations forced producers to progress, and waste disposal and emissions must meet regulatory requirements. Advances in technology have also made such problems always easy to solve. The waste gas, waste residue, and waste water have been discharged to the standard or processed into other products. For the treatment and processing of waste acid, the cost of successful foreign methods is relatively high, around 100-180$/t titanium dioxide; and most of the former domestic untreated, the only equipment introduced by a factory is only compared with foreign countries. At its lower limit, but not continuous production, it can not meet its waste acid production.
(1) Wastewater The acid-decomposing tail gas absorbs wastewater, and the titanic acid-washed dilute acid is neutralized with lime to produce gypsum for building materials.
(2) Waste acid After pretreatment, iron is concentrated, returned to production, or used in other chemical production requiring sulfuric acid raw materials.
(3) Waste slag Ferrous sulfate heptahydrate is processed into a water purifying agent, a feed additive, an iron red pigment, a magnetic ferrite or a sulfuric acid.
(4) Exhaust gas The acid-depleted tail gas is absorbed by water or alkali solution, and the calcined tail gas is absorbed by water or alkali solution, and then defoamed by static electricity.
1. Global sulfuric acid method Titanium dioxide waste acid treatment and comprehensive utilization overview Sulfuric acid method Titanium dioxide production process has been more than 80 years from 1918 to the present, long-term research and improvement has made its process more perfect, except for the operation process The main processes of each company are basically the same, the control methods and equipment are different. The sulfuric acid method is characterized by abundant resources (ilmenite, sulfuric acid), low cost and easy availability; mature technology, simple equipment and easy operation and management. The disadvantages are long process flow, intermittent operation, and large discharge of waste (ferrous sulfate, dilute sulfuric acid and acid sewage). In the late 1980s and early 1990s, the process of producing titanium dioxide by sulfuric acid method introduced different improvement methods, and comprehensively developed and treated waste acid, waste water and waste gas, so that the sulfuric acid method and the chlorination method no longer have more environmental protection. Great difference.
When the titanium dioxide is produced by the sulfuric acid method, a large amount of dilute sulfuric acid is generated regardless of whether titanium concentrate is used as a raw material or titanium nitride is used as a raw material to produce titanium dioxide. The amount and amount of dilute sulfuric acid produced varies depending on the process separation technique. For each production of It titanium dioxide, the average concentration of spent sulfuric acid is about 8-8 tons, and its typical composition is shown in Table 1.
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2. Overview of waste acid treatment of titanium dioxide produced by major sulfuric acid in foreign countries. The treatment and treatment of waste acid produced by titanium dioxide in the main sulfuric acid process abroad are shown in Table 2.
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3. Representative waste acid concentration process (1) Finnish technology Finland Ruma-Repola company is a large national engineering company in Finland. The company's five divisions, Rosenlew Engineering is committed to industrial environmental engineering technology, specializing in the treatment of industrial wastewater and waste acid. It is said that the evaporation equipment they provide accounts for 50% of the world's evaporation, ranking first in the world.
Rauma's concentrating unit has been used in titanium dioxide production plants in Germany and Finland. According to reports, in 1981 in Germany (formerly West Germany) Bayer company to establish a pilot plant, using forced circulation, the end point concentration of waste acid is 65%. In 1982, according to the pilot process, a three-stage evaporation concentrating unit was built, which processed 30 tons per hour and produced 78% acid.
In 1987, Bayer was again provided with a larger waste acid concentrating unit with an evaporation capacity of 58 t/h, and the equipment materials were greatly updated. The glass-reinforced concrete was used for the production of chloroethylene. The unit was put into operation in 1989.
In 1989, a set of waste acid concentrating devices was established for the Finnish Chemila company in Pori.
In China, Rauma has negotiated the supply of waste acid concentrating equipment to the sputum workshop of Zibo Linyi Organic Chemical Plant and Baoding Second Chemical Plant. It is said that it also supplies titanium liquid concentration and vacuum crystallization equipment for the 15 OOOt/a titanium white workshop of Gansu 404 Factory. Not implemented for other reasons.
In 1990, Finnish Rauma Company exchanged information on waste acid concentration technology in Nanjing and Nanjing Oil Chemical Plant. They introduced a 20% scented acid that was concentrated by evaporation to 70% and 20% of spent acid was evaporated to 70%. In the case of a section of the evaporation of the two lines and the three sections of the evaporation of the line, the price is only more than 200,000 US dollars, and the evaporation of the water is about 1. 2t. . Therefore, the Nanjing Grease Chemical Plant had planned to introduce the technology, and the feasibility study report of the Third Institute of Chemicals, the l0kt/a titanium dioxide expansion and reconstruction project was not implemented.
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