Method for concentrating waste sulfuric acid by utilizing waste heat of titanium dioxide calcinator

Abstract

The invention discloses a method for concentrating waste sulfuric acid by utilizing waste heat of a titanium dioxide calcinator, comprising the following steps: at normal temperature and pressure, proper amount of water absorbent is added to titanium dioxide waste acid, liquid water is dissolved out in the form of solid crystal water through the water absorbent, filtrate after solid-liquid separation is cooled, iron vitriol in the solution is crystallized and dissolved out, and the acid liquid is further concentrated; the two steps are repeatedly carried out until the concentration of sulfuric acid in the final filtrate reaches more than 60%, and then the final filtrate is utilized in the acid hydrolysis procedure; and the water absorbent is dehydrated and dried to be regenerated by taking dustproof tail gas of the calcinator, and the steam generated in the drying and regeneration is cooled and flows back to technological process as washing water in titanic acid rinsing or is drained. The method provided by the invention solves the problems of more equipment, long flow and easy blockage in the existing technology, and the equipment investment and operating cost are reduced; and the water absorbent is recycled after being regenerated, so that the energy is saved, the consumption is reduced, and the efficiency is obvious; no wastewater, waste gases and residues are generated in the whole technology, the operability is strong, the productivity of equipment is high, the flow is simple, the investment is less, the cost is low, energy is saved, emission is reduced, and the benefit is obvious.

Description

technical field [0001] The invention relates to a method for concentrating waste sulfuric acid by utilizing waste heat of a titanium dioxide roasting furnace. Background technique [0002] The production of titanium dioxide by the sulfuric acid method has the advantages of sufficient raw material sources and low cost, but every ton of titanium dioxide produced will produce about 6-8 tons of waste acid containing 20% ​​sulfuric acid. If the waste acid is not recycled, it will inevitably cause The waste of a large number of precious resources, improper handling will also cause secondary pollution and damage to the environment. [0003] At present, the treatment methods of titanium dioxide waste sulfuric acid mainly include the following: [0004] ① Directly return to the production line for diluting concentrated sulfuric acid. The advantage is that it can be reused directly without adding too much treatment and transportation equipment, but because the discharge of waste aci...

AI Technical Summary

Problems solved by technology

The disadvantages of these methods are: 1) using the rotary kiln exhaust gas in one stage of concentration, only paying attention to the utilization of heat, and ignoring the economic value of titanium dioxide in the exhaust gas; 2) the titanium dioxide dust brought out from the rotary kiln exhaust gas, It has a certain solubility in acid, and the unhydrolyzed titanyl sulfate remaining in the acid not only causes the viscosity of the acid to increase, but also brings more trouble to the subsequent evaporation and concentration; 3) it is used in the second-stage concentration The block type graphite heat exchanger is not conducive to the heat exchange of titanium dioxide waste acid containing scaling substances and a large amount of solid phase precipitates, and the cleaning of scaling is relatively frequent, which is costly and time-consuming; 4) in the third stage A silicon carbide evaporator is used in the concentration to further heat and concentrate the waste acid that has been concentrated to 70% to 80%, which not only requires a large investment in equipment, but also consumes a lot of energy for cooling and heating of the process.

In order to solve the above problems, the Chinese patent application "Prevent scaling method and special device of one-effect heating equipment for the concentration of titanium dioxide waste sulfuric acid" (CN102320580A) has increased the process flow and made its operation more complicated

[0009] Although the Chinese patent "Concentration and removal of impurities of dilute sulfuric acid in the production of titanium dioxide by sulfuric acid method" (CN101214931A) has amended the Chinese patent application "A Production Method of Concentration and Removal of Dilute Sulfuric Acid" (CN1376633), the replacement of graphite tubes is increased. The pipe diameter of the heater is used to facilitate the cleaning and regeneration of the scale layer, but the problem of scaling and preventing heat transfer has not been completely solved, and the equipment and its accessories have not been fully domesticated; each ton of concentrated sulfuric acid consumes 2.0 to 2.4 steam t (Research status and development direction of sulfuric acid titanium dioxide waste acid concentration technology [J], Inorganic Salt Industry, 2008, 40 (8): 1~3)

[0010] In addition, in the existing Chinese patent applications, there are many references to the application of waste heat at the kiln tail and the kiln head, but there is no literature report on the utilization of the heat energy brought by the high-temperature titanium dioxide at 700-900 °C when the kiln head is discharged.

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