System for comprehensively utilizing heat of phosphoric acid concentration device

Abstract

The invention relates to the technical field of phosphoric acid solution concentration, in particular to a system for comprehensively utilizing heat of a phosphoric acid concentration device. A raw material acid preheater; a first-stage evaporation separator; a first-stage circulating pump; a first-stage evaporator; a gas-liquid separator; a second-stage evaporator; a second-stage evaporation separator; and a two-section circulating pump is adopted, and the connection relationship among all equipment is limited. Circulating water for cooling finished phosphoric acid is omitted by using the feeding and discharging heat exchanger, so that heat utilization in the concentration process is more efficient and reasonable, and the economical efficiency of the device is improved. In the invention, all the devices can be effectively matched to act, heat in the concentration process is effectively and reasonably utilized, the steam consumption is reduced, and the economical efficiency of the device is improved.

Description

Technical Field

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

[0002] At present, in phosphoric acid preparation projects, low-pressure steam is generally used to evaporate and concentrate phosphoric acid solution with a mass concentration of about 34%, concentrating it to 44% or 75%. The concentrated phosphoric acid has a high temperature and is generally cooled to room temperature by circulating water before being sent to the tank area for storage. Therefore, the heat of the concentration process is not reasonably utilized, resulting in a huge 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 of 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 connected to the first phosphoric acid outlet of the first evaporation separator; a first branch inlet is arranged on the pipeline between the first evaporation separator and the first 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 arranged 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 through 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 connected to the phosphoric acid outlet of the second-stage evaporation separator; a second branch inlet is arranged 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 arranged 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 exchangers are shell and tube graphite heat exchangers.

[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 an inlet and outlet heat exchanger to eliminate the circulating water used for cooling the finished phosphoric acid, making the heat utilization in the concentration process more efficient and reasonable, and increasing the economic efficiency of the device. In the present invention, each device can effectively cooperate, the heat in the concentration process is effectively and reasonably utilized, reducing steam consumption and increasing the economic efficiency of the device. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0022] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] The present invention provides a system for comprehensive utilization of heat of 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] A 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 connected to the first phosphoric acid outlet of the first evaporation separator; a first branch inlet is arranged on the pipeline between the first evaporation separator and the first 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 through 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] A 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 connected to the phosphoric acid outlet of the second-stage evaporation separator; a second branch inlet is arranged 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 arranged 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 utilization of heat in a phosphoric acid concentration device provided for one embodiment of the present invention. 1 is raw phosphoric acid, 2 is phosphoric acid preheated by a raw acid preheater, 3 is a portion of phosphoric acid coming out of a first-stage circulating pump (entering a first-stage evaporator), 4 is phosphoric acid vapor discharged from a first-stage evaporator, 5 is another portion of phosphoric acid coming out of a first-stage circulating pump, 6 is phosphoric acid cooled by an inlet and outlet heat exchanger, 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 a second-stage circulating pump (entering a second-stage evaporator), 9 is phosphoric acid vapor from a second-stage evaporator (entering a second-stage evaporation separator), 10 is another portion of phosphoric acid coming out of a second-stage circulating pump (entering a pipeline 11), and the phosphoric acid in 5 and the phosphoric acid in 11 enter the inlet and outlet heat exchangers. 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 of 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 material 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 some embodiments of the present invention, the first stage circulation 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 heat-exchanged with another part of the finished phosphoric acid 5 (with a concentration of 42% to 46%) from the first-stage circulating pump or another part of the finished phosphoric acid 11 (with a concentration of 73% to 77%) from the second-stage circulating pump in the inlet and outlet heat exchanger 18, and is heated from room temperature to 45 to 55° C.; 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 from the first branch inlet on the pipeline between the first-stage evaporation separator 21 and the first-stage circulating pump 25, and is heated by the first-stage evaporation separator 21 and the second-stage circulating pump 25. A part of the phosphoric acid in the separator 21 passes through a first-stage circulating pump 25, a part of the phosphoric acid coming out of the first-stage circulating pump 25 enters a first-stage evaporator 20, and the other part enters the inlet and outlet heat exchanger 18 as the finished phosphoric acid 5; the heat source of the first-stage evaporator 20 is the low-pressure steam 15 (temperature is 145-155° C.), and the low-pressure steam enters the gas-liquid separator 23 for gas-liquid separation after condensation in the first-stage evaporator 20, and the separated steam condensate is used as the heat source of 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 of the low-pressure steam.

[0045] The phosphoric acid in the first evaporator is heated to 105-115°C, phosphoric acid vapor 4 is discharged, and enters the first evaporation separator 21 for gas-liquid separation. The gas phase (gas discharged from the first evaporation separator) 13 is used as the heat source of the second evaporator 24, and the condensed liquid after heat recovery in the second evaporator 24 enters the subsequent recovery system. The liquid phase (the second part of phosphoric acid discharged from the first evaporation separator) 7 enters from the second branch inlet on the pipeline between the second evaporation separator and the second circulation pump, and passes through the second circulation pump 26 together with a part of phosphoric acid in the second evaporation separator 22. A part of the phosphoric acid coming out of the second circulation pump 26 enters the second evaporator 24, and the other part enters the pipeline 11 as the finished phosphoric acid and enters the inlet and outlet heat exchanger 18; the phosphoric acid in the second evaporator 24 is heated to 95-105°C, phosphoric acid vapor 9 is discharged, and enters the second evaporation separator 22 for gas-liquid separation, and the gas phase (gas obtained by gas-liquid separation in the second evaporation separator) 14 enters the subsequent condensation system.

[0046] The finished phosphoric acid 5 (with a concentration of 42% to 46%) from the first-stage circulation pump 25 and another part of the finished phosphoric acid 11 (with a concentration of 73% to 77%) from the second-stage circulation pump can enter the inlet and outlet heat exchanger 18 through the valve switch for final heat recovery. The temperature of the phosphoric acid 6 cooled by the inlet and outlet heat exchanger drops to 43 to 47° C. and enters the subsequent storage system. At this point, the heat gradient utilization of the entire concentration system is completed.

[0047] In order 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 in conjunction with embodiments, but it 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 material phosphoric acid 1 with a mass concentration of 34% exchanges heat with another part of the finished phosphoric acid 5 (with a concentration of 44%) from the first-stage circulating pump or another part of the finished phosphoric acid 11 (with a concentration of 75%) from the second-stage circulating pump in the inlet and outlet heat exchanger 18, and is heated from room temperature to 50° C.; 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 70° C.; then enters from the first branch inlet on the pipeline between the first-stage evaporation separator 21 and the first-stage circulating pump 25, and is heated by one part of the first-stage evaporation separator 21. Part of the phosphoric acid passes through a first-stage circulation pump 25, and part of the phosphoric acid coming out of the first-stage circulation pump 25 enters a first-stage evaporator 20, and the other part enters the inlet and outlet heat exchanger 18 as a finished phosphoric acid 5; the heat source of the first-stage evaporator 20 is low-pressure steam 15 (temperature is 150°C), and the low-pressure steam enters the gas-liquid separator 23 for gas-liquid separation after condensation in the first-stage evaporator 20. The separated steam condensate is used as the heat source of 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 of the low-pressure steam.

[0051] The phosphoric acid in the first evaporator is heated to 110°C, phosphoric acid vapor 4 is discharged, and enters the first evaporation separator 21 for gas-liquid separation. The gas phase (gas discharged from the first evaporation separator) 13 is used as the heat source of the second evaporator 24, and the condensed liquid after heat recovery in the second evaporator 24 enters the subsequent recovery system. The liquid phase (the second part of phosphoric acid discharged from the first evaporation separator) 7 enters from the second branch inlet on the pipeline between the second evaporation separator and the second circulation pump, and passes through the second circulation pump 26 together with a part of phosphoric acid in the second evaporation separator 22. A part of the phosphoric acid coming out of the second circulation pump 26 enters the second evaporator 24, and the other part enters the pipeline 11 as the finished phosphoric acid and enters the inlet and outlet heat exchanger 18; the phosphoric acid in the second evaporator 24 is heated to 100°C, phosphoric acid vapor 9 is discharged, and enters the second evaporation separator 22 for gas-liquid separation, and the gas phase (gas obtained by gas-liquid separation in the second evaporation separator) 14 enters the subsequent condensation system.

[0052] The finished phosphoric acid 5 (with a concentration of 44%) from the first-stage circulation pump 25 and another part of the finished phosphoric acid 11 (with a concentration of 75%) from the second-stage circulation pump can enter the inlet and outlet heat exchangers 18 through valve switches for final heat recovery. The temperature of the phosphoric acid 6 cooled by the inlet and outlet heat exchangers drops to 45° C. and enters the subsequent storage system. At this point, the heat gradient utilization of the entire concentration system is completed.

[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 evaporation separator 21 is a graphite flash evaporator. The first stage circulation 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 generally commercially available gas-liquid separator. The second stage evaporator 24 is a vertical shell and tube heat exchanger. The second stage evaporation separator 22 is a graphite flash evaporator. The second stage circulation 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 replenishment in the concentration system is achieved.

[0056] The description of the above embodiments is only used to help understand the method of the present invention and its core idea. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will conform to the widest range 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; One stage evaporation separator; A circulating pump connected to the first phosphoric acid outlet of the first evaporation separator; a first branch inlet is arranged on the pipeline between the first evaporation separator and the first 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 arranged 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 through 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 connected to the phosphoric acid outlet of the second-stage evaporation separator; a second branch inlet is arranged 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 arranged 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, characterized in that The inlet and outlet heat exchangers are shell and tube graphite heat exchangers.

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

4. The system according to claim 1, characterized in that The first stage evaporation separator is a graphite flash evaporator.

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

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

7. The system according to claim 1, characterized in that The second stage evaporation separation is a graphite flash evaporator.

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