Novel method for performing vacuum crystallization on ferrous sulfate from titanium liquid in titanium dioxide production process

Abstract

The invention discloses a novel method for performing vacuum crystallization on ferrous sulfate from titanium liquid in titanium dioxide production. According to the method, the conventional ferrous sulfate vacuum crystallization process and equipment are innovated. The process innovation refers to the operation of replacing the conventional method for generating vacuum by virtue of steam jet by a method for condensing water vapor above titanium liquid in a crystallization kettle so as to generate vacuum by virtue of cryogenic refrigeration. The equipment innovation refers to the operation of replacing the conventional secondary steam jet equipment and circulating cooling water equipment for cooling high-temperature acid containing liquid by the complete refrigerating equipment generating a certain low temperature. According to the method disclosed by the invention, ferrous sulfate is separated from the titanium liquid in the crystallization kettle, lots of high-temperature high-pressure steam can be saved, and the production cost of titanium dioxide by sulfuric acid method is greatly reduced. In addition, the acidic condensate extracted from the crystallization kettle by vacuum can return to be used for an ilmenite powder sulfuric acid dissolving process, so that the amount of sulfuric acid in the process of generating titanium dioxide by a sulfuric acid method is reduced, the emission amount of acid waste liquid is greatly reduced, and clean production is realized.

Description

Technical field: [0001] The invention belongs to the field of chemical engineering and chemical equipment, in particular to a method for obtaining high vacuum degree in chemical production, in particular to a new method for vacuum crystallization of by-product ferrous sulfate from titanium liquid in the process of producing titanium dioxide by sulfuric acid method and related chemical equipment. Background technique: [0002] The scientific name of titanium dioxide is titanium dioxide. Its chemical properties are stable, non-toxic and harmless. It is currently recognized as the best white pigment in the world. It is widely used in coatings, plastics, rubber, inks, paper, chemical fibers, ceramics, Japan Chemical, pharmaceutical, food and other industries, among which coatings, plastics and papermaking are the three industries with the largest consumption of titanium dioxide, accounting for more than 80% of the total consumption of titanium dioxide; compared with other white ...

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Problems solved by technology

[0005] 2. The ferrous sulfate crystallization system uses pressurized steam injection to generate vacuum, which only uses the kinetic energy of steam, and the temperature of saturated steam with a pressure of 0.5-0.8MPa reaches 152-170°C. Although such steam injection still has a high Waste heat energy, but because of the mixing of acidic water vapor, acid corrosion and safety issues need to be solved for the use of waste heat. At present, this part of waste heat has basically not been effectively utilized, resulting in a serious waste of steam heat energy; according to statistics, the current sulfuric acid process titanium dioxide The total steam consumption per ton of product is about 1.3-1.5 tons, and most of the steam consumed is used in the ferrous sulfate vacuum crystallization section. The current status is that the steam used in this section is sprayed to form acidic steam, which contains Not only the thermal energy and the remaining kinetic energy cannot be utilized, but another set of circulating cooling water system needs to be established to cool and discharge them, so the cost of sulfuric acid titanium dioxide production remains high

[0006] 3. It is difficult to maintain the operating pressure of the system at 1500Pa (absolute pressure) for a long time in the ferrous sulfate crystallization system in the existing high-pressure steam secondary injection and water ring vacuum pump to generate vacuum, because the process has a high impact on the external temperature. The change is relatively sensitive. When the ambient temperature is high, the cooling effect of the cooling water on the sprayed steam will decrease due to the increase of the temperature of the circulating cooling water, which will reduce the vacuum degree of the system and reduce the evaporation of water in the titanium liquid, resulting in production failure. Efficiency fluctuates

However, steam condensed into liquid+vacuum pump combination according to the present invention produces the required high vacuum method and related complete equipment for ferrous sulfate crystallization, and the method for reclaiming and reusing acidic condensed water has no public reports so far

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