A system for comprehensive utilization of heat from a phosphoric acid concentration device

Abstract

The present invention relates to the technical field of phosphoric acid solution concentration, and in particular to a system for comprehensive heat utilization in a phosphoric acid concentration device, comprising: an inlet and outlet heat exchanger; a raw acid preheater; a first-stage evaporation separator; a first-stage circulation pump; a first-stage evaporator; a gas-liquid separator; a second-stage evaporator; a second-stage evaporation separator; and a second-stage circulation pump, with defined connections between the various devices. The present invention utilizes an inlet and outlet heat exchanger to eliminate the need for circulating water for cooling finished phosphoric acid, making heat utilization in the concentration process more efficient and reasonable, thereby increasing the economic efficiency of the device. In the present invention, the various devices can effectively cooperate, effectively and reasonably utilizing the heat in the concentration process, reducing steam consumption and increasing the economic efficiency of the device.

Description

Technical Field

[0001] The present invention relates to the technical field of phosphoric acid solution concentration, in particular to a system for comprehensive utilization of heat of a phosphoric acid concentration device. Background Art

[0002] Currently, phosphoric acid production projects typically use low-pressure steam to evaporate and concentrate a 34% phosphoric acid solution to 44% or 75%. The concentrated phosphoric acid is relatively hot and is typically cooled to room temperature using circulating water before being transferred to a tank farm for storage. Consequently, the heat generated during the concentration process is not utilized effectively, resulting in significant waste of raw materials and energy. Summary of the Invention

[0003] In view of this, the technical problem to be solved by the present invention is to provide a system for comprehensive utilization of heat in a phosphoric acid concentration device, so that the heat in the concentration process is effectively and reasonably utilized, steam consumption is reduced, and the economy of the device is increased.

[0004] The present invention provides a system for comprehensive utilization of heat from a phosphoric acid concentration device, comprising:

[0005] Inlet and outlet heat exchangers;

[0006] A raw acid preheater; the raw phosphoric acid inlet of the raw acid preheater is connected to the raw phosphoric acid outlet of the inlet and outlet heat exchanger;

[0007] a first stage evaporation separator;

[0008] A circulating pump is connected to the first phosphoric acid outlet of the first evaporation separator; a first branch inlet is provided on the pipeline between the first evaporation separator and the circulating pump; the first branch inlet is connected to the raw phosphoric acid outlet of the raw acid preheater;

[0009] a first-stage evaporator; the reflux phosphoric acid inlet of the first-stage evaporator is connected to the phosphoric acid outlet of the first-stage circulating pump; a first branch outlet is provided on the pipeline between the first-stage evaporator and the first-stage circulating pump; the first branch outlet is connected to the finished phosphoric acid inlet of the inlet and outlet heat exchanger via a first valve; the phosphoric acid vapor outlet of the first-stage evaporator is connected to the phosphoric acid vapor inlet of the first-stage evaporation separator;

[0010] A gas-liquid separator connected to the low-pressure steam outlet of the first-stage evaporator; the condensate outlet of the gas-liquid separator is connected to the heat source inlet of the raw acid preheater; the raw acid preheater is provided with a condensate outlet;

[0011] A second-stage evaporator; the heat source inlet of the second-stage evaporator is connected to the gas outlet of the first-stage evaporation separator;

[0012] A two-stage evaporation separator; the phosphoric acid vapor inlet of the two-stage evaporation separator is connected to the phosphoric acid vapor outlet of the two-stage evaporator;

[0013] A second-stage circulation pump is connected to the phosphoric acid outlet of the second-stage evaporation separator; a second branch inlet is provided on the pipeline between the second-stage evaporation separator and the second-stage circulation pump; the second branch inlet is connected to the second phosphoric acid outlet of the first-stage evaporation separator; the outlet of the second-stage circulation pump is connected to the reflux phosphoric acid inlet of the second-stage evaporator; a second branch outlet is provided on the pipeline between the second-stage evaporator and the second-stage circulation pump; the second branch outlet is connected to the finished phosphoric acid inlet of the inlet and outlet heat exchanger through a second valve.

[0014] Preferably, the inlet and outlet heat exchanger is a shell and tube graphite heat exchanger.

[0015] Preferably, the raw acid preheater is a shell and tube graphite heat exchanger.

[0016] Preferably, the first stage evaporation separator is a graphite flash evaporator.

[0017] Preferably, the first stage evaporator is a vertical shell and tube heat exchanger.

[0018] Preferably, the second-stage evaporator is a vertical shell and tube heat exchanger.

[0019] Preferably, the second stage evaporation separation is a graphite flash evaporator.

[0020] The present invention uses inlet and outlet heat exchangers to eliminate the need for circulating water for cooling finished phosphoric acid, making heat utilization during the concentration process more efficient and reasonable, thereby increasing the economic efficiency of the device. In the present invention, the various devices effectively cooperate to effectively and rationally utilize heat during the concentration process, reducing steam consumption and increasing the economic efficiency of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A system diagram of comprehensive heat utilization in a phosphoric acid concentration device provided in one embodiment of the present invention. DETAILED DESCRIPTION

[0022] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0023] The present invention provides a system for comprehensive utilization of heat from a phosphoric acid concentration device, comprising:

[0024] Inlet and outlet heat exchanger; the inlet and outlet heat exchanger is provided with a raw phosphoric acid inlet, a finished phosphoric acid inlet, a raw phosphoric acid outlet, and a finished phosphoric acid outlet;

[0025] Raw acid preheater; the raw acid preheater is provided with a raw phosphoric acid inlet, a raw phosphoric acid outlet, a heat source inlet, and a condensate outlet; the raw phosphoric acid inlet of the raw acid preheater is connected to the raw phosphoric acid outlet of the inlet and outlet heat exchanger;

[0026] a first stage evaporation separator; the first stage evaporation separator is provided with a first phosphoric acid outlet, a second phosphoric acid outlet, a gas outlet, and a phosphoric acid vapor inlet;

[0027] A circulating pump is connected to the first phosphoric acid outlet of the first evaporation separator; a first branch inlet is provided on the pipeline between the first evaporation separator and the circulating pump; the first branch inlet is connected to the raw phosphoric acid outlet of the raw acid preheater;

[0028] A first-stage evaporator; the first-stage evaporator is provided with a reflux phosphoric acid inlet, a low-pressure steam inlet, a low-pressure steam outlet, and a phosphoric acid vapor outlet; the reflux phosphoric acid inlet of the first-stage evaporator is connected to the phosphoric acid outlet of the first-stage circulating pump; a first branch outlet is provided on the pipeline between the first-stage evaporator and the first-stage circulating pump; the first branch outlet is connected to the finished phosphoric acid inlet of the inlet and outlet heat exchanger via a first valve; the phosphoric acid vapor outlet of the first-stage evaporator is connected to the phosphoric acid vapor inlet of the first-stage evaporation separator;

[0029] A gas-liquid separator connected to the low-pressure steam outlet of the first-stage evaporator; the condensate outlet of the gas-liquid separator is connected to the heat source inlet of the raw acid preheater; the raw acid preheater is provided with a condensate outlet;

[0030] Two-stage evaporator; the two-stage evaporator is provided with a heat source inlet, a condensate outlet, a phosphoric acid vapor outlet, and a reflux phosphoric acid inlet; the heat source inlet of the two-stage evaporator is connected to the gas outlet of the one-stage evaporation separator;

[0031] Two-stage evaporation separator; the two-stage evaporation separator is provided with a phosphoric acid outlet, a phosphoric acid vapor inlet, and a gas outlet; the phosphoric acid vapor inlet of the two-stage evaporation separator is connected to the phosphoric acid vapor outlet of the two-stage evaporator;

[0032] A second-stage circulation pump is connected to the phosphoric acid outlet of the second-stage evaporation separator; a second branch inlet is provided on the pipeline between the second-stage evaporation separator and the second-stage circulation pump; the second branch inlet is connected to the second phosphoric acid outlet of the first-stage evaporation separator; the outlet of the second-stage circulation pump is connected to the reflux phosphoric acid inlet of the second-stage evaporator; a second branch outlet is provided on the pipeline between the second-stage evaporator and the second-stage circulation pump; the second branch outlet is connected to the finished phosphoric acid inlet of the inlet and outlet heat exchanger through a second valve.

[0033] Figure 1 A system diagram for comprehensive heat utilization of a phosphoric acid concentration device provided in one embodiment of the present invention. In it, 1 is raw phosphoric acid, 2 is phosphoric acid preheated by the raw acid preheater, 3 is a portion of phosphoric acid coming out of the first-stage circulating pump (entering the first-stage evaporator), 4 is phosphoric acid vapor discharged from the first-stage evaporator, 5 is another portion of phosphoric acid coming out of the first-stage circulating pump, 6 is phosphoric acid cooled by the inlet and outlet heat exchangers, 7 is the second portion of phosphoric acid discharged from the first-stage evaporation separator, 8 is a portion of phosphoric acid coming out of the second-stage circulating pump (entering the second-stage evaporator), 9 is phosphoric acid vapor from the second-stage evaporator (entering the second-stage evaporation separator), 10 is another portion of phosphoric acid coming out of the second-stage circulating pump (entering pipeline 11), and the phosphoric acid in 5 and the phosphoric acid in 11 enter the inlet. Discharge heat exchanger; 12 is the condensate outlet of the second-stage evaporator, 13 is the gas discharged from the first-stage evaporation separator (entering the second-stage evaporator, serving as the heat source of the second-stage evaporator), 14 is the gas obtained by gas-liquid separation in the second-stage evaporation separator, 15 is the heat source of the first-stage evaporator (low-pressure steam), 16 is the low-temperature and low-pressure steam discharged from the first-stage evaporator, 17 is the condensate discharged from the gas-liquid separator, 18 is the inlet and outlet heat exchanger, 19 is the raw acid preheater, 20 is the first-stage evaporator, 21 is the first-stage evaporation separator, 22 is the second-stage evaporation separator, 23 is the gas-liquid separator, 24 is the second-stage evaporator, 25 is the first-stage circulation pump, and 26 is the second-stage circulation pump.

[0034] In certain embodiments of the present invention, the mass concentration of the raw phosphoric acid entering the inlet and outlet heat exchanger is 30% to 38%, such as 34%.

[0035] In certain embodiments of the present invention, the inlet and outlet heat exchanger 18 is a shell and tube graphite heat exchanger.

[0036] In certain embodiments of the present invention, the raw acid preheater 19 is a shell and tube graphite heat exchanger.

[0037] In certain embodiments of the present invention, the first stage evaporation separator 21 is a graphite flash evaporator.

[0038] In certain embodiments of the present invention, the first stage circulating pump 25 is a variable frequency centrifugal pump.

[0039] In certain embodiments of the present invention, the first stage evaporator 20 is a vertical shell and tube heat exchanger.

[0040] In certain embodiments of the present invention, the gas-liquid separator 23 is a commonly available gas-liquid separator on the market.

[0041] In certain embodiments of the present invention, the second-stage evaporator 24 is a vertical shell and tube heat exchanger.

[0042] In certain embodiments of the present invention, the second-stage evaporation separator 22 is a graphite flash evaporator.

[0043] In certain embodiments of the present invention, the second-stage circulation pump 26 is a variable frequency centrifugal water pump.

[0044] In the present invention, the raw material phosphoric acid 1 with a mass concentration of 30% to 38% is heated from room temperature to 45 to 55°C by heat exchange with another part of the finished phosphoric acid 5 (with a concentration of 42% to 46%) from the first stage circulation pump or another part of the finished phosphoric acid 11 (with a concentration of 73% to 77%) from the second stage circulation pump in the inlet and outlet heat exchanger 18; then enters the raw material acid preheater 19, where it is heated by the steam condensate 17 from the gas-liquid separator 23 to further increase the temperature to 65 to 75°C; then enters the first branch inlet of the pipeline between the first stage evaporation separator 21 and the first stage circulation pump 25, and is heated by the steam condensate 17 from the first stage evaporation separator 23. A portion of the phosphoric acid in the separator 21 passes through a first-stage circulating pump 25. A portion of the phosphoric acid from the first-stage circulating pump 25 enters a first-stage evaporator 20, and the remaining portion enters the inlet and outlet heat exchanger 18 as finished phosphoric acid 5. The heat source for the first-stage evaporator 20 is low-pressure steam 15 (temperature 145-155°C). After condensation in the first-stage evaporator 20, the low-pressure steam enters the gas-liquid separator 23 for gas-liquid separation. The separated steam condensate serves as the heat source for the raw acid preheater 19, where heat is further recovered. The steam is then transported to the heat source inlet pipeline of the first-stage evaporator 20 and reused as supplementary steam for the low-pressure steam.

[0045] The phosphoric acid in the primary evaporator is heated to 105-115°C, and phosphoric acid vapor 4 is discharged. The phosphoric acid enters the primary evaporator separator 21 for gas-liquid separation. The gas phase (gas discharged from the primary evaporator separator) 13 serves as a heat source for the secondary evaporator 24. The condensate, after heat is recovered in the secondary evaporator 24, enters the subsequent recovery system. The liquid phase (the second portion of phosphoric acid discharged from the primary evaporator separator) 7 enters the second branch inlet of the pipeline between the secondary evaporator separator and the secondary circulation pump. Together with a portion of the phosphoric acid in the secondary evaporator separator 22, it passes through the secondary circulation pump 26. Part of the phosphoric acid discharged from the secondary circulation pump 26 enters the secondary evaporator 24, while the remaining portion enters the pipeline 11 as finished phosphoric acid and enters the feed-discharge heat exchanger 18. The phosphoric acid in the secondary evaporator 24 is heated to 95-105°C, and the phosphoric acid vapor 9 is discharged. The phosphoric acid enters the secondary evaporator separator 22 for gas-liquid separation. The gas phase (gas obtained from the gas-liquid separation in the secondary evaporator separator) 14 enters the subsequent condensation system.

[0046] Finished phosphoric acid 5 (42%-46% concentration) from the first-stage circulation pump 25 and another portion of finished phosphoric acid 11 (73%-77% concentration) from the second-stage circulation pump can be fed into the inlet and outlet heat exchangers 18 through valves for final heat recovery. After cooling in the inlet and outlet heat exchangers, the temperature of the phosphoric acid 6 drops to 43-47°C before entering the subsequent storage system. This completes the heat gradient utilization of the entire concentration system.

[0047] To further illustrate the present invention, a system for comprehensive utilization of heat in a phosphoric acid concentration device provided by the present invention is described in detail below with reference to examples, but this should not be construed as limiting the scope of protection of the present invention.

[0048] Example 1

[0049] Use Figure 1 The system for comprehensive utilization of heat from a phosphoric acid concentration device shown in the figure performs comprehensive utilization of heat from a phosphoric acid concentration device:

[0050] The raw phosphoric acid 1 with a mass concentration of 34% is heated from room temperature to 50°C by heat exchange in the inlet and outlet heat exchanger 18 with another portion of finished phosphoric acid 5 (with a concentration of 44%) from the first stage circulation pump or another portion of finished phosphoric acid 11 (with a concentration of 75%) from the second stage circulation pump; then enters the raw acid preheater 19, where it is heated by the steam condensate 17 from the gas-liquid separator 23 to further increase its temperature to 70°C; then enters the first branch inlet of the pipeline between the first stage evaporation separator 21 and the first stage circulation pump 25, and is heated by the steam condensate 17 in the first stage evaporation separator 21. Part of the phosphoric acid passes through a first-stage circulating pump 25. A portion of the phosphoric acid discharged from the first-stage circulating pump 25 enters a first-stage evaporator 20, and the remaining portion enters the inlet and outlet heat exchanger 18 as finished phosphoric acid 5. The heat source of the first-stage evaporator 20 is low-pressure steam 15 (temperature of 150°C). After condensation in the first-stage evaporator 20, the low-pressure steam enters the gas-liquid separator 23 for gas-liquid separation. The separated steam condensate is used as the heat source for the raw acid preheater 19 to further recover heat. The steam is transported to the heat source inlet pipeline of the first-stage evaporator 20 and reused as supplementary steam for the low-pressure steam.

[0051] The phosphoric acid in the primary evaporator is heated to 110°C, and phosphoric acid vapor 4 is discharged. It then enters the primary evaporator separator 21 for gas-liquid separation. The gas phase (gas discharged from the primary evaporator separator) 13 serves as a heat source for the secondary evaporator 24. The condensate, after heat is recovered in the secondary evaporator 24, enters the subsequent recovery system. The liquid phase (the second portion of phosphoric acid discharged from the primary evaporator separator) 7 enters the second branch inlet of the pipeline between the secondary evaporator separator and the secondary circulation pump. Together with a portion of the phosphoric acid in the secondary evaporator separator 22, it passes through the secondary circulation pump 26. Part of the phosphoric acid discharged from the secondary circulation pump 26 enters the secondary evaporator 24, while the remaining portion enters the pipeline 11 as finished phosphoric acid and enters the feed-discharge heat exchanger 18. The phosphoric acid in the secondary evaporator 24 is heated to 100°C, and the phosphoric acid vapor 9 is discharged. It then enters the secondary evaporator separator 22 for gas-liquid separation. The gas phase (gas obtained from the gas-liquid separation in the secondary evaporator separator) 14 enters the subsequent condensation system.

[0052] Finished phosphoric acid 5 (44% concentration) from the first-stage circulation pump 25 and another portion of finished phosphoric acid 11 (75% concentration) from the second-stage circulation pump are then fed into the inlet and outlet heat exchangers 18 via valves for final heat recovery. After cooling in the inlet and outlet heat exchangers, the temperature of the phosphoric acid 6 drops to 45°C before entering the subsequent storage system. This completes the heat gradient utilization of the entire concentration system.

[0053] The inlet and outlet heat exchanger 18 is a shell and tube graphite heat exchanger.

[0054] The raw acid preheater 19 is a shell-and-tube graphite heat exchanger. The first-stage evaporator separator 21 is a graphite flash evaporator. The first-stage circulating pump 25 is a variable-frequency centrifugal pump. The first-stage evaporator 20 is a vertical shell-and-tube heat exchanger. The gas-liquid separator 23 is a commercially available gas-liquid separator. The second-stage evaporator 24 is a vertical shell-and-tube heat exchanger. The second-stage evaporator separator 22 is a graphite flash evaporator. The second-stage circulating pump 26 is a variable-frequency centrifugal water pump.

[0055] Compared with the technical solution of using circulating water to cool the concentrated phosphoric acid to room temperature, after the implementation of Example 1, the steam heat consumption index is reduced from the original 915tce standard coal to 875tce standard coal, the circulating water energy consumption is 90% of the original value, and self-circulating supply is achieved within the concentration system.

[0056] The above embodiments are intended only to facilitate understanding of the methods and core concepts of the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein, but is intended to be construed in the widest manner consistent with the principles and novel features disclosed herein.

Claims

1. A system for comprehensive utilization of heat from a phosphoric acid concentration device, comprising: Inlet and outlet heat exchangers; A raw acid preheater; the raw phosphoric acid inlet of the raw acid preheater is connected to the raw phosphoric acid outlet of the inlet and outlet heat exchanger; a first stage evaporation separator; A circulating pump is connected to the first phosphoric acid outlet of the first evaporation separator; a first branch inlet is provided on the pipeline between the first evaporation separator and the circulating pump; the first branch inlet is connected to the raw phosphoric acid outlet of the raw acid preheater; a first-stage evaporator; the reflux phosphoric acid inlet of the first-stage evaporator is connected to the phosphoric acid outlet of the first-stage circulating pump; a first branch outlet is provided on the pipeline between the first-stage evaporator and the first-stage circulating pump; the first branch outlet is connected to the finished phosphoric acid inlet of the inlet and outlet heat exchanger via a first valve; the phosphoric acid vapor outlet of the first-stage evaporator is connected to the phosphoric acid vapor inlet of the first-stage evaporation separator; A gas-liquid separator connected to the low-pressure steam outlet of the first-stage evaporator; the condensate outlet of the gas-liquid separator is connected to the heat source inlet of the raw acid preheater; the raw acid preheater is provided with a condensate outlet; A second-stage evaporator; the heat source inlet of the second-stage evaporator is connected to the gas outlet of the first-stage evaporation separator; A two-stage evaporation separator; the phosphoric acid vapor inlet of the two-stage evaporation separator is connected to the phosphoric acid vapor outlet of the two-stage evaporator; A second-stage circulation pump is connected to the phosphoric acid outlet of the second-stage evaporation separator; a second branch inlet is provided on the pipeline between the second-stage evaporation separator and the second-stage circulation pump; the second branch inlet is connected to the second phosphoric acid outlet of the first-stage evaporation separator; the outlet of the second-stage circulation pump is connected to the reflux phosphoric acid inlet of the second-stage evaporator; a second branch outlet is provided on the pipeline between the second-stage evaporator and the second-stage circulation pump; the second branch outlet is connected to the finished phosphoric acid inlet of the inlet and outlet heat exchanger through a second valve.

2. The system according to claim 1, wherein: The inlet and outlet heat exchangers are shell and tube graphite heat exchangers.

3. The system according to claim 1, wherein: The raw acid preheater is a shell and tube graphite heat exchanger.

4. The system according to claim 1, wherein: The first stage evaporation separator is a graphite flash evaporator.

5. The system according to claim 1, wherein: The first stage evaporator is a vertical shell and tube heat exchanger.

6. The system according to claim 1, wherein: The second-stage evaporator is a vertical shell and tube heat exchanger.

7. The system according to claim 1, wherein: The second stage evaporation separation is a graphite flash evaporator.

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