Direct heating type superphosphoric acid production device

Abstract

The invention relates to a direct heating type superphosphoric acid production device which comprises a body, the body is in a vertical olive-shaped closed tank shape, and a heating evaporation cavity, a gas-liquid separation cavity and a gas inlet and outlet cavity which are communicated with one another are sequentially formed in the body from bottom to top; the heating evaporation cavity is in an inverted cone shape, and a feeding pipe and a discharging pipe which are through inside and outside are arranged on the side walls of the bottom and the top of the heating evaporation cavity; the gas-liquid separation cavity is cylindrical, and the inner diameter of the gas-liquid separation cavity is the same as that of the upper end of the heating evaporation cavity; an air inlet pipe and an air outlet pipe are arranged on the side wall of the air inlet and outlet cavity; the air inlet pipe is arranged in the axial direction of the body, and the lower end of the air inlet pipe extends into the heating evaporation cavity. The wet-process phosphoric acid can be heated and evaporated to obtain the persulfuric acid, so that the process is shortened, the scaling of equipment is reduced, and the operating rate is increased.

Description

Technical Field

[0001] The invention relates to a chemical production device, in particular to a device for producing persulfuric acid, specifically to a direct heating superphosphoric acid production device. Background Art

[0002] Phosphoric acid produced by decomposing phosphate rock with sulfuric acid (hereinafter referred to as wet-process phosphoric acid) accounts for the vast majority of phosphoric acid production. Wet-process phosphoric acid contains a large amount of impurities. During transportation and storage, these impurities will precipitate out, causing a lot of trouble and causing the loss of P2O5. If wet-process phosphoric acid is further heated and concentrated to make superphosphoric acid, the polyphosphoric acid in it can chelate these impurities, so that they will no longer precipitate, and the product is more suitable for transportation and storage.

[0003] At present, the industrial production of superphosphoric acid usually adopts the following two methods: Method 1: Phosphate ore is melted in an electric furnace, and a reduction reaction is carried out with carbon to release a mixed gas of phosphorus (P4) and carbon monoxide (CO). The phosphorus vapor is condensed into yellow phosphorus, and the phosphorus pentoxide (P2O5) produced by the combustion of yellow phosphorus is absorbed by water to obtain superphosphoric acid. This method requires the use of electric furnaces, dust collectors, condensers, filters and other equipment. It is not only energy-intensive, but also highly polluting, and has been phased out.

[0004] Method 2: Wet-process phosphoric acid with a mass concentration of phosphorus pentoxide (P2O5) ≥40% is subjected to multi-stage concentration and dehydration to finally obtain superphosphoric acid with a mass concentration of phosphorus pentoxide (P2O5) ≥68%. However, this method requires more equipment, including heat exchangers, evaporation concentrators, circulation pumps, etc., resulting in high construction and maintenance costs. Moreover, the production process of this method is long. It is necessary to first indirectly circulate and heat the wet-process phosphoric acid with steam in the concentrated phosphoric acid heat exchanger, and then the hot phosphoric acid enters the concentrated phosphoric acid evaporation concentrator for cyclic evaporation and concentration. Then, the concentrated phosphoric acid is indirectly circulated and heated with a heat transfer unit in the superphosphoric acid heat exchanger, and then the hot concentrated phosphoric acid enters the superphosphoric acid evaporation concentrator for cyclic evaporation and concentration to produce superphosphoric acid. Therefore, the production control is complicated and the production cost is increased. Since there is a large temperature difference on both sides of the heat transfer surface of the concentrated phosphoric acid heat exchanger and the superphosphoric acid heat exchanger and the phosphoric acid contains impurities, scaling is easy to form on the phosphoric acid side of the heat transfer surface, which affects the production efficiency and increases the maintenance workload.

[0005] Therefore, it is urgently needed to be improved in order to better meet production needs. Summary of the invention

[0006] The purpose of the present invention is to provide a direct heating superphosphoric acid production device for the problems currently encountered in the production of persulfuric acid, which can heat and evaporate wet-process phosphoric acid to obtain persulfuric acid, shorten the process, reduce equipment scaling, and increase the operating rate.

[0007] The technical solution of the present invention is: A direct heating superphosphoric acid production device comprises a main body, which is a vertical olive-shaped closed can, and is provided with a heating evaporation chamber, a gas-liquid separation chamber and an air inlet and outlet chamber which are interconnected from bottom to top in sequence; the heating evaporation chamber is an inverted cone, and a feed pipe and a discharge pipe which are interconnected are provided on the side walls of the bottom and top respectively; the gas-liquid separation chamber is cylindrical, and its inner diameter is the same as the inner diameter of the upper end of the heating evaporation chamber; the air inlet and outlet chamber is hemispherical, and an air inlet pipe and an air outlet pipe which are interconnected are provided on the side walls; the air inlet pipe is arranged along the axial direction of the main body, and its lower end extends into the heating evaporation chamber.

[0008] Furthermore, the side wall of the body includes an outer layer, a middle layer and an inner layer arranged from the outside to the inside; the outer layer is made of stainless steel; the middle layer is made of red shale bricks; and the inner layer is made of carbon bricks.

[0009] Furthermore, the middle layer is made of two layers of red shale bricks.

[0010] Furthermore, the angle between the side wall of the heating evaporation chamber and the horizontal plane is 60°.

[0011] Furthermore, the feed pipe and the discharge pipe are both arranged horizontally, and their inner ports are flush with the inner wall of the heating evaporation chamber.

[0012] Furthermore, the air outlet pipe is arranged obliquely upward, and the angle between its axis and the horizontal plane is 30°.

[0013] Furthermore, the air inlet pipe is located at the center of the body.

[0014] Furthermore, the feed pipe, the discharge pipe and the air outlet pipe are all made of carbon tubes, and the parts thereof located outside the side wall of the main body are wrapped with an outer sleeve made of a stainless steel tube.

[0015] Furthermore, the air intake pipe is a straight pipe, including an outer pipe and an inner pipe tightly fitted together; the outer pipe is a carbon pipe; the inner pipe is a stainless steel pipe; the upper end of the inner pipe is flush with the upper end of the outer pipe, and its lower end is located inside the lower end of the outer pipe and flush with the discharge pipe; the lower end of the outer pipe is located below the discharge pipe.

[0016] Furthermore, the portion of the air inlet pipe located outside the main body is wrapped with an outer sleeve made of a stainless steel pipe.

[0017] Beneficial effects of the present invention: 1. It has the functions of direct heating and evaporation, and can be used to heat the production of concentrated phosphoric acid and superphosphoric acid, and can be widely used in industrial production processes.

[0018] 2. The hot gas is in direct contact with the phosphoric acid solution, and no indirect heat exchanger is used. There is no heat transfer surface, which avoids scaling on the heat transfer surface. The hot gas and the phosphoric acid solution directly exchange heat, there is no temperature difference, and the heat transfer efficiency is high.

[0019] 3. The side walls of the main body are lined with two layers of red shale bricks and one layer of carbon bricks. Carbon bricks have good corrosion resistance while red shale bricks can reduce heat loss.

[0020] 4. The bottom of the body is conical to reduce the heating dead angle, which can reduce the heating volume and shorten the residence time of the phosphoric acid solution.

[0021] 5. The inner tube of the intake pipe is made of stainless steel and the outer tube is made of carbon tube, which can prevent the oxygen in the hot gas from directly contacting the carbon material, reduce the oxidation of the carbon material and extend the service life. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 It is a structural schematic diagram of the present invention.

[0022] Figure 2 Table 1 is the performance evaluation result table of 80 tons / day superphosphoric acid heating evaporation device.

[0023] Among them, 1-heating evaporation chamber; 2-outer sleeve; 3-feeding pipe; 4-outer layer; 5-middle layer; 6-inner layer; 7-air inlet and outlet chamber; 8-outer tube; 9-inner tube; 10-outlet pipe; 11-gas-liquid separation chamber; 12-discharging pipe. DETAILED DESCRIPTION

[0024] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0025] like Figure 1 and Figure 2 shown.

[0026] A direct heating superphosphoric acid production device includes a main body. The main body is in the shape of a vertical closed can, and is provided with a heating evaporation chamber 1, a gas-liquid separation chamber 11 and an air inlet and outlet chamber 7 that are interconnected from bottom to top. The side wall includes an outer layer 4, an intermediate layer 5 and an inner layer 6 that are arranged from outside to inside. The outer layer 4 is made of stainless steel and is strong and durable. The intermediate layer 5 is made of red shale bricks and has a heat-insulating effect. The inner layer 6 is made of carbon bricks and has good corrosion resistance. Preferably, the intermediate layer 5 is made of two layers of red shale bricks to improve its heat-insulating effect.

[0027] The heating evaporation chamber 1 is inverted cone-shaped, and the side walls at the bottom and top thereof are provided with a feed pipe 3 and a discharge pipe 12 that are connected inside and outside. The feed pipe 3 and the discharge pipe 12 are both arranged horizontally, and their inner ports are flush with the inner wall of the heating evaporation chamber 1, so that the raw phosphoric acid and the target product persulfate can flow in and out smoothly. The feed pipe 3 and the discharge pipe 12 are both made of carbon tubes, which have good corrosion resistance. At the same time, the parts of the feed pipe 3 and the discharge pipe 12 located outside the side wall of the body are wrapped with an outer sleeve 2. The outer sleeve 2 is made of stainless steel pipe, which can increase the strength and facilitate the feed pipe 3 and the discharge pipe 12 to be connected to other equipment through flanges. The angle α between the inner wall of the heating evaporation chamber 1 and the horizontal plane is 30°~80°, preferably α=60°, which can reduce the heating dead angle and heating volume and shorten the residence time of the phosphoric acid solution.

[0028] The gas-liquid separation chamber 11 is cylindrical, and its inner diameter is the same as the inner diameter of the upper end of the heating evaporation chamber, so that the non-condensable gas, water vapor and superphosphoric acid contained in the steam generated by heating and evaporation in the heating evaporation chamber can be separated. Among them, the non-condensable gas and water vapor flow upward into the air inlet and outlet chamber, and the superphosphoric acid condenses into small droplets and flows downward back to the heating evaporation section. Preferably, the ratio of the inner diameter of the gas-liquid separation chamber 11 to its height is 10:13, ensuring that the gas-liquid mixture is effectively separated therein.

[0029] The air inlet and outlet cavity 7 is hemispherical, and its inner diameter is the same as that of the gas-liquid separation cavity. An air inlet pipe and an air outlet pipe 10 are provided on its side wall.

[0030] The air inlet pipe is in the shape of a straight tube, arranged along the axial direction of the body, and located in the center of the body. The air inlet pipe includes an outer tube 8 and an inner tube 9 that are tightly sleeved. The outer tube 8 is a carbon tube. The inner tube 9 is a stainless steel tube. The upper end of the inner tube 9 is flush with the upper end of the outer tube 8, and its lower end is located within the lower end of the outer tube 8 and is flush with the discharge pipe 12. The lower end of the outer tube 8 is located below the discharge pipe 12, so that the external hot gas flows from the air inlet pipe to below the phosphoric acid liquid level in the heating evaporation chamber 1, and the phosphoric acid liquid is fully heated. At the same time, the lower end of the inner tube 9 is flush with the phosphoric acid liquid level, which can avoid being corroded by phosphoric acid. Moreover, the hot gas can be prevented from directly contacting the outer tube 8, reducing the oxidation of the carbon material and extending the service life. Preferably, the height difference between the lower port of the outer tube 8 and the lower port of the inner tube is about 13 cm, which can ensure that the hot gas fully enters the phosphoric acid liquid. At the same time, the portion of the air inlet pipe located outside the side wall of the main body is wrapped with an outer sleeve 2 made of a stainless steel pipe, which improves its strength and facilitates its connection with external equipment through a flange.

[0031] The outlet pipe 10 is obliquely upward and throughly arranged on the side wall of the air inlet and outlet cavity, and the angle between its axis and the horizontal plane is β=0°~80°, preferably β=30°, which is convenient for the discharge of tail gas after gas-liquid separation. The outlet pipe 10 is made of carbon tube and has corrosion resistance. At the same time, the part of the outlet pipe 10 located outside the body is wrapped with an outer sleeve 2 made of stainless steel tube, which can improve its strength and facilitate its connection with external equipment through flanges.

[0032] The working process of the present invention is: The raw phosphoric acid (containing 54.1% P2O5 mass concentration and room temperature) from the boundary zone is fed into the heating evaporation chamber from the feed pipe. At the same time, the hot gas (temperature of about 921°C) from the boundary zone is fed into the liquid phase in the heating evaporation chamber from the air inlet pipe, with a flow rate of 10m / s~40m / s and a temperature of 210°C~1000°C, so that the phosphoric acid in the heating evaporation chamber is heated and its water evaporates. The phosphoric acid that loses a lot of water becomes superphosphoric acid (containing 74.5% P2O5 mass concentration and temperature of 283°C) and flows out of the boundary zone from the discharge port. At the same time, the steam formed by the evaporation of phosphoric acid in the heating evaporation chamber rises into the gas-liquid separation chamber. The steam contains non-condensable gas and water, as well as some small droplets of superphosphoric acid taken out by the steam. As the steam rises, the small droplets of superphosphoric acid gradually gather into larger droplets and drip into the heating evaporation chamber under the action of gravity. The rest of the tail gas containing non-condensable gas and water continues to rise to the air inlet and outlet chambers and is discharged from the air outlet pipe to the boundary zone.

[0033] An embodiment of the present invention is as follows: the height of the heating evaporation chamber is 0.6m, and α=60°. The inner diameter of the gas-liquid separation chamber is 1.2m, and its height is 1.56m. The operation results of this embodiment are shown in Table 1. Therefore, the present invention can directly heat and evaporate wet-process phosphoric acid to obtain persulfuric acid, shorten the production process, reduce equipment scaling, and increase the operating rate.

[0034] The parts not involved in the present invention are the same as the prior art or can be implemented by using the prior art.

Claims

1. A direct heating superphosphoric acid production device, comprising a body, characterized in that: The main body is in the shape of a vertical olive-shaped closed can, and a heating evaporation chamber, a gas-liquid separation chamber, and an air inlet and outlet chamber are provided in sequence from bottom to top. The heating evaporation chamber is in the shape of an inverted cone, and a feed pipe and a discharge pipe are provided on the side walls of the bottom and top respectively. The gas-liquid separation chamber is in the shape of a cylinder, and its inner diameter is the same as that of the upper end of the heating evaporation chamber. The air inlet and outlet chamber is in the shape of a hemispherical cavity, and an air inlet pipe and an air outlet pipe are provided on the side walls. The air inlet pipe is arranged along the axial direction of the main body, and its lower end extends into the heating evaporation chamber.

2. The direct heating superphosphoric acid production device according to claim 1, characterized in that: The side wall of the body includes an outer layer, a middle layer and an inner layer arranged from the outside to the inside; the outer layer is made of stainless steel; the middle layer is made of red shale bricks; and the inner layer is made of carbon bricks.

3. The direct heating superphosphoric acid production device according to claim 2, characterized in that: The middle layer is made of two layers of red shale bricks.

4. The direct heating type superphosphoric acid production device according to claim 1 is characterized in that: The angle between the side wall of the heating evaporation chamber and the horizontal plane is 60°.

5. The direct heating superphosphoric acid production device according to claim 1, characterized in that: The feed pipe and the discharge pipe are both arranged horizontally, and the inner ports thereof are both flush with the inner wall of the heating evaporation chamber.

6. The direct heating superphosphoric acid production device according to claim 1 is characterized in that: The air outlet pipe is arranged obliquely upward, and the angle between its axis and the horizontal plane is 30°.

7. The direct heating superphosphoric acid production device according to claim 1 is characterized in that: The air inlet pipe is located at the center of the body.

8. The direct heating superphosphoric acid production device according to claim 1 is characterized in that: The feed pipe, the discharge pipe and the air outlet pipe are all made of carbon tubes, and the parts thereof located outside the side wall of the body are wrapped with an outer sleeve made of a stainless steel tube.

9. The direct heating superphosphoric acid production device according to claim 1 is characterized in that: The air inlet pipe is a straight pipe, including an outer pipe and an inner pipe tightly fitted together; the outer pipe is a carbon pipe; the inner pipe is a stainless steel pipe; the upper end of the inner pipe is flush with the upper end of the outer pipe, and its lower end is located inside the lower end of the outer pipe and flush with the discharge pipe; the lower end of the outer pipe is located below the discharge pipe.

10. The direct heating superphosphoric acid production device according to claim 1, characterized in that: The portion of the air inlet pipe located outside the body is wrapped with an outer sleeve made of a stainless steel pipe.

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