SU1411275A1 - Method of producing phosphoric acid - Google Patents

Abstract

This invention relates to a process for the processing of phosphorus sludge formed during the production of phosphorus. The aim of the invention is to reduce the content of phosphoric anhydride in the exhaust gases. The method consists in burning the crushed sludge at 1500-1800 s and an air excess factor of 1.1-1.5, supplying water to the stage of separating the mineral part of the sludge in an amount that ensures the temperature of the gas phase 1200-. 1300 ° C, cooling the gas phase to 800-900 ° C, hydration of phosphoric anhydride, followed by purification of the discharge basins in the electrostatic precipitator. 2 tab. with "(L

Description

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The invention relates to a process for the processing of phosphorus-containing sludges formed during the production of yellow phosphorus to thermal phosphoric acid.

The aim of the invention is to reduce the content of phosphoric anhydride in the waste gases after its hydration,

Example. Phosphoric sludge containing, in wt.%: Phosphorus 70, mineral impurities 5, water 25, with a flow rate of 3570 kg / h is fed for incineration into the furnace, where it is sprayed with a nozzle. Combustion is carried out in an air flow at its consumption of 1f) 136, which ensures its excess 1.5 times. During the combustion process, the temperature reaches, the Combustion Products from the furnace are tangentially fed to the separator, where in the swirling flow the separation of the molten mineral part of psham from the gas phase occurs with the formation of a melt. Here

however, water is supplied to the separator at a flow rate of 800 kg / h, which is also sprayed with a nozzle. The temperature of the gas-vapor mixture at the same time decreases to. Melt temperature in the separator 1220 s. The melt is hardened. The gas-vapor mixture from the separator is fed through a gas duct, in which it is cooled to 800 ° C, into the hydration tower. In the hydration tower, 85% of the phosphoric anhydride contained in the gases is captured with irrigating acid, after which the gases are sent to an electrostatic precipitator and then to the atmosphere. The content of phosphoric anhydride in. Waste gas 60 mg / m.

According to a known method, the content of phosphoric anhydride in the exhaust gases is at least 150 mg / m.

In the table. Figure 1 shows the dependence of the content of phosphoric anhydride in the exhaust gases on the water consumption at the stage of melt separation of the mineral part of the sludge.

Table 1

ABOUT

200

400

500

600

700

800

900

000

100

200

1450 1400 1380 1350 1300 1280 1250 1230 1200 1180 1100

Overheated

Fluid flow

Viscous

Razm gchenny, does not follow

3k

The dependence of the content of phosphoric anhydride in the exhaust gases on the temperature of the gas-vapor mixture supplied for hydration is given in table 2.

table 2

The treatment of combustion products with water at the stage of separation of the mineral part allows the process of hydration of phosphoric anhydride in the gas phase to be carried out. The water-vapor-vapor mixture after separation of the liquid melt due to rotation on the walls of the apparatus is subjected to cooling in the gas duct. At the same time, it is cooled to 800-900 ° C, when acid condensation begins, and saturated water is supplied to the hydration tower.

12734

a mixture that undergoes opoineHui co-centrio 1} oh (70%) phosphorus acid.

Conducting hydration of phosphorus anhydride in the gas phase and a gradual decrease in the temperature of the vapor-gas mixture prior to the onset of condensation can significantly reduce the amount of oxygen

0 acid vapor. In addition, hydration with water vapor allows increasing the concentration of irrigating acid without altering the circulation in general. Water vapor pressure

5 with an increase in its concentration decreases, which leads to a decrease in the amount of mist formed and an increase in the degree of absorption.

0 This allows you to increase the efficiency of the hydration process, reduce fogging and get a phosphoric acid mist with a larger droplet size (more

5 1.0 μm). Consolidation of fog drops

contributes to its better capture. and thereby reducing emissions to the environment.

Claims (1)

0 claims The method of obtaining phosphoric acid, including the burning of crushed phosphorus sludge at 1500-1800 - C 25 and an air excess factor of 1.1–1.5, water flow, separation of the molten mineral part of the sludge from the gas phase containing phosphoric anhydride, its hydration and purification from. 0 running gases in the electrostatic precipitator, which is due to the fact that, in order to reduce the content of phosphoric anhydride in the exhaust gases, water is supplied to the amount of separation of the mineral part of the sludge in the amount of 1200-1300 ° C, which is cooled to 800–900 ° C before hydration.