Improved method for large-scale production of phosphoric acid with rotary kiln

Abstract

The invention discloses an improved method for large-scale production of phosphoric acid with a rotary kiln. The reducing agent powder, phosphate rock powder and silica powder are mixed to make the inner ball; then the carbonaceous reducing agent powder and the silica powder are mixed to obtain the wrapping material; the inner ball and the wrapping material are mixed for wrapping treatment, dried and consolidated to obtain a composite pellet ; Send the composite pellets into the rotary kiln for reduction reaction; the high-temperature slag balls out of the rotary kiln are sent to the cooling equipment for comprehensive utilization; the kiln flue gas containing P2O5 and fluorine is passed into a hydration tower for hydration Absorb phosphorus, and then pass through the phosphoric acid mist collection tower and demist separation tower in turn, and the fluorine-containing flue gas discharged from the demist separation tower enters the subsequent fluorine recovery process. The technological process of the present invention is rationally optimized, the equipment investment is small, the economic added value is high, the whole technological process is energy-saving and environment-friendly, the operation is efficient, and the product quality is excellent.

Description

technical field [0001] The invention relates to a raw material pretreatment method and equipment in a phosphoric acid production process, in particular to a raw material pretreatment method and a pretreatment process system in a kiln phosphoric acid process (KPA). Background technique [0002] At present, there are two main methods for the industrial production of phosphoric acid in the world. (1) Phosphoric acid production by wet method: that is, using sulfuric acid to decompose phosphate rock to obtain dilute phosphoric acid and CaSO 4 ·nH 2 O is the main solid waste (referred to as phosphogypsum), and dilute phosphoric acid is concentrated to obtain wet-process phosphoric acid containing about 54% phosphoric acid. The main disadvantages of this process are: first, it consumes a large amount of sulfuric acid; second, the waste residue phosphogypsum cannot be effectively utilized, and the entrained sulfuric acid, phosphoric acid and soluble fluoride are all soluble in wat...

AI Technical Summary

Problems solved by technology

The main disadvantages of this process are: first, it consumes a large amount of sulfuric acid; second, the waste residue phosphogypsum cannot be effectively utilized, and the entrained sulfuric acid, phosphoric acid and soluble fluoride are all soluble in water, and are easily washed away by rain after natural stacking. It causes serious pollution to the environment; thirdly, the impurity content of phosphoric acid in the product is relatively high, and it is generally only used for the production of fertilizer; fourthly, in order to ensure the economy of the product, high-grade phosphate rock must be used

The main disadvantages of thermal phosphoric acid production: one is to consume a lot of electric energy; the other is to separate the P 4 The gas also contains a large amount of fluoride (SiF 4 and HF present) and a small amount of unprecipitated gas P 4 , which will cause serious pollution to the atmospheric environment; third, the gas containing a large amount of CO is directly burned and emptied, which is a great waste of energy; fourth, in order to ensure the economy of production, it is also necessary to use high-grade phosphate rock

[0005] However, our research shows that the above-mentioned kiln phosphoric acid process is difficult to realize in large-scale industrial application and practice, and its main defects are:

[0013] However, during our follow-up research, a series of new technical problems were discovered, including: 1) In the raw material pretreatment stage, the process cost and energy consumption are relatively high, and the composition of raw materials sent to the rotary kiln fluctuates Larger, the mixing of raw materials is not uniform enough, which will further aggravate the problem of high-temperature ring formation of powder in the rotary kiln; 2) The mechanical properties and mechanical strength of the composite pellets used as process raw materials are not stable enough, and there is no option for composite pellets to dry Industrial equipment and suitable drying methods, the pellet drying process is prone to bursting, and the bursting composite pellets enter the rotary kiln and pulverize and form rings in the high-temperature reduction zone of the rotary kiln; The dust reaction in the rotary kiln generates complex metaphosphate at the kiln tail of the rotary kiln, and gradually forms a kiln tail ring in the kiln tail body of the rotary kiln, which seriously reduces the operating efficiency of the rotary kiln; 4) During the cooling recovery stage, the released End P 2 o 5 The cooling effect of the final high-temperature slag ball needs to be improved, and the cooling heat energy has not been used reasonably and effectively, and the waste of resources and energy in the cooling process is serious; 5) In the subsequent phosphoric acid production stage, the flue gas volume of thermal phosphoric acid is small , the flue gas flow rate of the equipment is low, the equipment system is quite large, the structure is complex, and the investment and operation costs are high; the impurity content of the flue gas of kiln phosphoric acid is complex, and the flue gas from the kiln also contains fluorine-containing substances that are harmful to the human body (in the form of SiF 4 and HF forms), which need to be recycled while avoiding environmental pollution

[0014] Therefore, in order to solve a series of technical problems in the existing kiln-based phosphoric acid process, and to carry out long-term production in a more stable, more energy-saving, more environmentally friendly, low-cost and high-efficiency manner, the existing overall kiln-based phosphoric acid process still needs to be improved. Those skilled in the art carry out a large number of improvements and perfections

Images