Phosphoric acid preparation method

Abstract

The invention discloses a phosphoric acid preparation method, and relates to the technical field of phosphoric acid preparation. Comprising the following steps: S1, burdening; the method comprises the following steps: proportioning phosphorus-containing materials, pea coal and a flux according to a certain proportion; s2, mixing the materials; putting the prepared materials into a cylinder mixer for mixing; s3, smelting is conducted; the mixed materials are added into an oxygen-enriched side-blown furnace to be smelted, and molten liquid is obtained; s4, reduction is carried out; the molten liquid is subjected to reduction smelting treatment; s5, waste heat recovery; a waste heat boiler is adopted to recover heat in smoke exhausted by the oxygen-enriched side-blown furnace; s6, flue gas purification; the flue gas subjected to waste heat recovery treatment is subjected to dust removal treatment through a high-temperature dust collection device; s7, hydration of the absorption tower; and the dedusted and purified flue gas is absorbed by the absorption tower. The oxygen-enriched side-blown converter is adopted to extract the phosphorus-containing material, phosphorus-enriched gas can be directly obtained, high-quality and high-purity phosphoric acid can be obtained through hydration absorption of the absorption tower, and the process has the advantages of being low in investment, short in flow, more environmentally friendly, low in energy consumption and the like.

Description

Technical Field

[0001] The invention relates to the technical field of phosphoric acid preparation, and in particular to a method for preparing phosphoric acid. Background Art

[0002] At present, there are two main methods for producing phosphoric acid: wet process and thermal process. Among them, phosphoric acid produced by treating phosphate ore with sulfuric acid and other inorganic acids is wet process phosphoric acid, and phosphoric acid obtained by producing elemental phosphorus in an electric furnace or blast furnace and then burning and hydrating is called thermal process phosphoric acid. Compared with wet process phosphoric acid, thermal process phosphoric acid has less pollution and higher purity. It can effectively utilize low-grade phosphate ore and can be further used to prepare food-grade phosphoric acid and electronic-grade phosphate products. It has a wide range of applications and an increasing market demand. However, the current blast furnace production process of thermal phosphoric acid requires coke and sintering, and the energy consumption of electric furnace production is too high, resulting in poor production efficiency. Summary of the invention

[0003] The main purpose of the present invention is to provide a method for preparing phosphoric acid to solve the above problems.

[0004] To achieve the above object, the present invention provides a method for preparing phosphoric acid, comprising the following steps:

[0005] S1. batching: batching the phosphorus-containing material, granular coal and flux according to a certain proportion;

[0006] S2, mixing; putting the prepared materials into a drum mixer for mixing;

[0007] S3, smelting; adding the mixed materials into the oxygen-enriched side-blowing furnace, and blowing a certain proportion of reducing agent and oxygen-enriched air at the nozzle of the spray gun at the bottom layer of the oxygen-enriched side-blowing furnace to melt and partially reduce the materials to obtain a molten liquid; blowing air or oxygen-enriched air at the top layer of the nozzle of the oxygen-enriched side-blowing furnace to perform secondary combustion on the flue gas generated during the reduction process;

[0008] S4, reduction; adjusting the ratio of the reducing agent and the oxygen-enriched air to perform reduction smelting on the molten liquid; blowing air or oxygen-enriched air into the top nozzle of the oxygen-enriched side-blowing furnace to perform secondary combustion on the flue gas generated during the reduction process;

[0009] S5, waste heat recovery: waste heat boiler is used to recover the heat in the flue gas discharged from the oxygen-enriched side-blown furnace; after waste heat recovery treatment, the temperature of the flue gas drops to a certain temperature, but not less than 480℃;

[0010] S6, flue gas purification: the flue gas after waste heat recovery treatment is subjected to dust removal treatment by a high-temperature dust collecting device;

[0011] S7, hydration in absorption tower: the flue gas after dust removal and purification is absorbed by the absorption tower, the P2O5 in the flue gas is dissolved in water to form phosphoric acid, and the unabsorbed gas is discharged.

[0012] Furthermore, the phosphorus-containing material is selected from phosphate rock and / or high-phosphorus waste slag.

[0013] Furthermore, the reducing agent is one or more of natural gas, coal gas and pulverized coal; and the oxygen-enriched air is air with an oxygen volume concentration greater than 25%.

[0014] Furthermore, in step S1, the phosphorus-containing material, granular coal and flux are pretreated respectively, so that the particle sizes of the phosphorus-containing material, granular coal and flux are all ≤30 mm, and the water contents are all ≤10 wt%.

[0015] Furthermore, the processing temperature in step S3 is 1250-1650°C; and the processing temperature in step 4 is 1300-1600°C.

[0016] Furthermore, a temperature sensor is provided in the oxygen-enriched side-blowing furnace, and the mixing ratio of the reducing agent and the oxygen-enriched air is determined and adjusted through temperature detection.

[0017] Furthermore, step S3 and step S4 can be completed in the same oxygen-enriched side-blowing furnace, or can be completed separately in two oxygen-enriched side-blowing furnaces.

[0018] Furthermore, the smoke collected in step S5 and step S6 is returned to step S1.

[0019] Furthermore, a spiral tube heat exchanger is provided on the outside of the drum of the drum mixer, one end of the spiral tube heat exchanger is connected to the absorption tower, and the other end is an exhaust end.

[0020] The present invention has the following beneficial effects:

[0021] The present invention adopts an oxygen-enriched side-blowing furnace to refine phosphorus-containing materials, and phosphorus-rich gas can be directly obtained. After hydration and absorption in an absorption tower, high-quality and high-purity phosphoric acid can be obtained. No supporting sintering plant, pelletizing plant and coking plant are required. The process has the characteristics of low investment, short process, more environmental protection, low energy consumption, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The present invention is a flow chart of a method for preparing phosphoric acid. DETAILED DESCRIPTION

[0023] In order to achieve the above-mentioned purpose and effect, the technical means and structures adopted by the present invention are described in detail with reference to the accompanying drawings for the features and functions of the preferred embodiments of the present invention.

[0024] like Figure 1 As shown, the present invention provides a method for preparing phosphoric acid, comprising the following steps:

[0025] S1, batching; pre-treating the phosphorus-containing material, granular coal and flux respectively, so that the particle size of the phosphorus-containing material, granular coal and flux are all ≤30mm, and the water content is all ≤10wt%; batching the phosphorus-containing material, granular coal and flux according to a certain proportion; the phosphorus-containing material is selected from phosphate rock and / or high-phosphorus waste slag, etc.;

[0026] S2, mixing; putting the prepared materials into a drum mixer for mixing;

[0027] S3, smelting; adding the mixed materials into the oxygen-enriched side-blowing furnace, and blowing a certain proportion of reducing agent and oxygen-enriched air at the nozzle of the spray gun at the bottom layer of the oxygen-enriched side-blowing furnace to melt and partially reduce the materials to obtain a molten liquid; in order to improve the heating intensity and capacity utilization rate, blowing air or oxygen-enriched air at the top layer of the nozzle of the oxygen-enriched side-blowing furnace to carry out secondary combustion of the flue gas generated during the reduction process, and oxidize the reduced product single substance P into P2O5 gas; the reducing agent is one or more of natural gas, coal gas and pulverized coal; the oxygen-enriched air is air with a volume concentration of oxygen greater than 25%, and the processing temperature of the smelting process is controlled at 1250-1650°C;

[0028] S4, reduction; adjusting the ratio of the reducing agent and the oxygen-enriched air, and subjecting the molten liquid to reduction smelting treatment; in order to improve the heating intensity and capacity utilization rate, air or oxygen-enriched air is blown into the top nozzle of the oxygen-enriched side-blowing furnace to secondary combustion of the flue gas generated during the reduction process, and the reduced product single substance P is oxidized into P2O5 gas; the treatment temperature of the reduction process is controlled at 1300-1600°C;

[0029] S5, waste heat recovery: waste heat boiler is used to recover the heat in the flue gas discharged from the oxygen-enriched side-blown furnace; after waste heat recovery treatment, the temperature of the flue gas drops to a certain temperature, but not less than 480℃, which can be adjusted according to the requirements of the subsequent process;

[0030] S6, flue gas purification; the flue gas after waste heat recovery treatment is subjected to dust removal treatment by a high-temperature dust collecting device; preferably, the high-temperature dust collecting device can be a high-temperature bag dust collector;

[0031] S7, hydration in absorption tower: the flue gas after dust removal and purification is absorbed by the absorption tower, the P2O5 in the flue gas is dissolved in water to form phosphoric acid, and the unabsorbed gas is discharged.

[0032] The present invention adopts an oxygen-enriched side-blown furnace for refining, and reduces energy consumption by heat coupling between the smelting section and the reduction section. A part of the oxygen-enriched air blown in from the nozzle of the bottom spray gun oxidizes C and P in the material to produce CO and P2O5 gas, and a part of the oxygen-enriched air directly burns the granular coal to release heat. At the slag-iron interface of the molten pool, the C in the molten iron continuously reduces the calcium phosphate in the slag. A part of the reducing agent blown in from the nozzle of the bottom spray gun directly burns with oxygen to release heat, and a part of the reducing agent directly enters the molten iron to carburize the molten iron, thereby replenishing the C consumed by the molten iron due to the reduction of calcium phosphate and a small amount of iron oxide in the slag. The smelting section is mainly oxidative, releasing heat, and the reduction section is mainly reduction, absorbing heat. The smelting and reduction processes make full use of the chemical energy of coal, and the energy utilization rate is very high. The process uses coal to replace electricity, coal to replace coke, and flue gas waste heat is recovered, which greatly reduces the total energy consumption of the system. The purified flue gas adopts a mature absorption tower hydration process to obtain high-quality and high-purity phosphoric acid.

[0033] In another embodiment, a temperature sensor is provided in the oxygen-enriched side-blowing furnace, and the mixing ratio of the reducing agent and the oxygen-enriched air is determined and adjusted through temperature detection.

[0034] In another embodiment, step S3 and step S4 can be completed in the same oxygen-enriched side-blowing furnace, or can be completed separately in two oxygen-enriched side-blowing furnaces. When the processing volume is small, the same oxygen-enriched side-blowing furnace can be used, and the furnace is divided into two stages of smelting and reduction, that is, the production operation is intermittent in cycles. When the processing volume is large, two oxygen-enriched side-blowing furnaces can be used, and the smelting and reduction stages are respectively carried out continuously in the two oxygen-enriched side-blowing furnaces, and the two oxygen-enriched side-blowing furnaces are connected by a molten liquid hot delivery chute.

[0035] In another embodiment, the smoke collected in step S5 and step S6 is returned to step S1 and used as phosphorus-containing material ingredients to reduce material loss and improve material utilization.

[0036] In another embodiment, a spiral tube heat exchanger is provided on the outside of the drum of the drum mixer, one end of the spiral tube heat exchanger is connected to the absorption tower, and the other end is the exhaust end. After being processed by the absorption tower, the temperature of the flue gas is still lowered to a certain extent, and the heat is transferred to the material in the drum mixer through the spiral tube heat exchanger. On the one hand, the remaining temperature can be reused, and on the other hand, the material can be preheated to reduce the moisture content of the material and fuel consumption. In addition, the rotating drum of the drum mixer cooperates with the stationary spiral tube heat exchanger to make the material heated more evenly.

[0037] The above descriptions are only preferred embodiments of the present invention, not all embodiments. Anyone should be aware that any structural changes made under the inspiration of the present invention, and any technical solutions that are the same or similar to the present invention, belong to the protection scope of the present invention.

Claims

1. A method for preparing phosphoric acid, characterized in that: The following steps are involved: S1. batching: batching the phosphorus-containing material, granular coal and flux according to a certain proportion; S2, mixing; putting the prepared materials into a drum mixer for mixing; S3, smelting; adding the mixed materials into the oxygen-enriched side-blowing furnace, and blowing a certain proportion of reducing agent and oxygen-enriched air at the nozzle of the spray gun at the bottom layer of the oxygen-enriched side-blowing furnace to melt and partially reduce the materials to obtain a molten liquid; blowing air or oxygen-enriched air at the top layer of the nozzle of the oxygen-enriched side-blowing furnace to perform secondary combustion on the flue gas generated during the reduction process; S4, reduction; adjusting the ratio of the reducing agent and the oxygen-enriched air to perform reduction smelting on the molten liquid; blowing air or oxygen-enriched air into the top nozzle of the oxygen-enriched side-blowing furnace to perform secondary combustion on the flue gas generated during the reduction process; S5, waste heat recovery: waste heat boiler is used to recover the heat in the flue gas discharged from the oxygen-enriched side-blown furnace; after waste heat recovery treatment, the temperature of the flue gas drops to a certain temperature, but not less than 480℃; S6, flue gas purification: the flue gas after waste heat recovery treatment is subjected to dust removal treatment by a high-temperature dust collecting device; S7, hydration in absorption tower: the flue gas after dust removal and purification is absorbed by the absorption tower, the P2O5 in the flue gas is dissolved in water to form phosphoric acid, and the unabsorbed gas is discharged.

2. A method for preparing phosphoric acid according to claim 1, characterized in that: The phosphorus-containing material is selected from phosphate rock and / or high-phosphorus waste slag.

3. A method for preparing phosphoric acid according to claim 2, characterized in that: The reducing agent is one or more of natural gas, coal gas and pulverized coal; the oxygen-enriched air is air with an oxygen volume concentration greater than 25%.

4. A method for preparing phosphoric acid according to claim 3, characterized in that: In step S1, the phosphorus-containing material, granular coal and flux are pretreated respectively, so that the particle sizes of the phosphorus-containing material, granular coal and flux are all ≤30 mm, and the water contents are all ≤10 wt%.

5. A method for preparing phosphoric acid according to claim 3, characterized in that: The processing temperature in step S3 is 1250-1650°C; the processing temperature in step 4 is 1300-1600°C.

6. A method for preparing phosphoric acid according to claim 5, characterized in that: A temperature sensor is installed in the oxygen-enriched side-blowing furnace to determine and adjust the mixing ratio of the reducing agent and oxygen-enriched air through temperature detection.

7. A method for preparing phosphoric acid according to any one of claims 1 to 6, characterized in that: Step S3 and step S4 can be completed in the same oxygen-enriched side-blowing furnace, or can be completed separately in two oxygen-enriched side-blowing furnaces.

8. A method for preparing phosphoric acid according to any one of claims 1 to 6, characterized in that: The smoke collected in step S5 and step S6 is returned to step S1.

9. A method for preparing phosphoric acid according to any one of claims 1 to 6, characterized in that: The outer sleeve of the drum of the drum mixer is provided with a spiral tube heat exchanger, one end of the spiral tube heat exchanger is connected to the absorption tower, and the other end is an exhaust end.

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