A method for producing sulfuric acid by vacuum concentration of waste sulfuric acid

Abstract

The invention discloses a method for producing sulfuric acid by vacuum concentrating waste sulfuric acid, and specifically relates to the technical field of chemical industry. The invention adopts a double acid-acid heat exchanger to recover heat, uses a heat tracing pipe system to preheat a glass-lined pipeline, reduces the temperature difference of the glass-lined pipeline to less than 100 DEG C, protects the glass-lined pipeline, adopts a hot and cold acid mixer to control the acid temperature entering the acid-acid heat exchanger, ensures that the acid temperature rises steadily, avoids the equipment from being damaged by a sudden temperature change, adopts a liquid level-flow control combined control technology, realizes double feeding, realizes automatic control and continuous operation of simultaneously or alternately producing sulfuric acid products with a concentration of 91% and a concentration of 96%, and the whole process is simple to operate. The sulfuric acid concentration is increased from an average of 95.5% to an average of 96.2%, can meet the production needs of two products, mononitrotoluene and polynitrotoluene, and reduce the production cost, thereby eliminating the problem of frequent shutdowns due to brushing of a waste sulfuric acid vacuum concentrator and extending the service life of the device.

Description

Technical Field

[0001] The present invention relates to the field of chemical technology, and more specifically, to a method for producing sulfuric acid by vacuum concentrating waste sulfuric acid. Background Art

[0002] In the production process of mononitrotoluene production line and common nitration production line, two specifications of waste sulfuric acid are generally produced. In order to facilitate unified treatment, the two specifications of waste sulfuric acid often share a set of waste sulfuric acid vacuum concentration treatment device. After treatment, the waste sulfuric acid can obtain concentrated sulfuric acid with a concentration of about 95.5%. In order to meet the use requirements of sulfuric acid concentration of the two nitration production lines, the waste sulfuric acid vacuum concentration production device has been producing concentrated sulfuric acid with a concentration of 95.5%. When the required finished sulfuric acid concentration is 96%, the forced circulation section of the waste sulfuric acid vacuum concentration device that produces 96% sulfuric acid needs to be shut down for 1.5 days for every 10 days of production, and the production is shut down 30 times a year.

[0003] At present, there are three main technical routes for vacuum concentration treatment of waste sulfuric acid. One is the treatment technology introduced from Germany's PLINKE company, which uses spraying mononitrotoluene as an anti-coagulant, high vacuum, and a relatively high terminal temperature; one is the treatment technology introduced from Germany's DDPS company, which uses warm water cooling to prevent condensation, ultra-high vacuum, and a relatively low terminal temperature (180°C-185°C); and the other is domestic waste sulfuric acid treatment technology. The product sulfuric acid concentration obtained by the above devices is one of 88%-96.5%, with 88% and 93% being the most common concentration specifications.

[0004] The above processing device and method have the following problems in actual use:

[0005] 1. The mononitrotoluene production line generally uses concentrated sulfuric acid with a concentration of more than 88% to meet the nitration production requirements. The mononitrotoluene production line uses 96% sulfuric acid for nitration, which, on the one hand, causes excess sulfuric acid concentration. On the other hand, due to the high sulfuric acid concentration, the local ￠ value of the nitration process is too high, which is prone to over-nitration, making it difficult to control the content of dinitrotoluene in the mononitrotoluene, and increasing the cost of distillation separation of mononitrotoluene;

[0006] 2. A set of equipment can only produce concentrated sulfuric acid of a certain concentration at the same time, and it is difficult to produce sulfuric acid with a concentration of more than 96% by the waste sulfuric acid vacuum concentration treatment device. Generally, the concentration is kept stable at about 95.5%. When the required sulfuric acid concentration is higher than 95.5%, it is necessary to add a heat transfer oil concentration device on the basis of the 96% waste sulfuric acid vacuum concentration device, which makes the production cost rise sharply;

[0007] 3. The waste sulfuric acid vacuum concentration device produces sulfuric acid with a concentration of more than 91%, which increases the production cost by more than 20% compared with 96% sulfuric acid, causing a significant increase in production costs;

[0008] 4. The forced circulation section of the waste sulfuric acid vacuum concentration device that produces 96% sulfuric acid needs to be shut down for 1.5 days for cleaning every 10 days of production, with 30 starts and stops per year. Frequent starts and stops cause damage to the device, which needs to be cleaned for 45 days each year, seriously reducing the production capacity of the waste sulfuric acid vacuum concentration device.

[0009] In view of this, it is of great significance to study a new method for vacuum concentrating waste sulfuric acid to produce sulfuric acid to solve the above problems. Summary of the invention

[0010] In order to overcome the above-mentioned defects of the prior art, the present invention provides a method for producing sulfuric acid by vacuum concentrating waste sulfuric acid. The technical problem to be solved by the present invention is that a set of waste sulfuric acid treatment equipment in the prior art can only produce concentrated sulfuric acid of a certain concentration at the same time, and it is difficult to produce sulfuric acid with a concentration of more than 96%, and the production cost will also rise sharply. In addition, when producing sulfuric acid with two concentrations, it needs to be scrubbed for 45 days each year, which seriously reduces the production capacity of the waste sulfuric acid vacuum concentrator.

[0011] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a method for producing sulfuric acid by vacuum concentration of waste sulfuric acid, comprising a waste sulfuric acid treatment device, wherein the waste sulfuric acid treatment device comprises a first acid-acid heat exchanger, the first acid-acid heat exchanger and the second acid-acid heat exchanger are both connected to the upper left side of a denitrification tower by connecting pipelines on the right side, the upper side of the denitrification tower is connected to a gas pipeline, the lower right side of the denitrification tower is connected to the lower left side of a secondary concentrator, the upper right side of the secondary concentrator is connected to a secondary gas phase processor, and the lower right side of the secondary concentrator is connected to a high-temperature sulfuric acid tank.

[0012] The high-temperature sulfuric acid tank is connected to a high-temperature hand pump on the right side, the high-temperature hand pump is connected to the first high-temperature automatic regulating valve on the right side, the first high-temperature automatic regulating valve is connected to the first high-temperature pipeline on the upper side, the first high-temperature pipeline is a glass-lined pipe, the first high-temperature pipeline is connected to the fourth temperature transmitter on the left side, and a heating pipe is arranged on the right side and the upper side of the first high-temperature pipeline, and the left side of the heating pipe is connected to the mixed acid tank.

[0013] The lower side of the mixed acid tank is connected to the second acid-acid heat exchanger, and the lower side of the second acid-acid heat exchanger is connected to the low-temperature sulfuric acid tank; the lower left side of the low-temperature sulfuric acid tank is connected to a low-temperature sulfuric acid pump, and the right side of the low-temperature sulfuric acid pump is connected to the second cooler.

[0014] The right side of the high-temperature hand pump is connected to the second high-temperature automatic regulating valve, the upper side of the second high-temperature automatic regulating valve is connected to the second high-temperature pipeline, the upper side of the second high-temperature pipeline is connected to the forced circulation heater, the upper left side of the forced circulation heater is respectively connected to the second temperature transmitter and the forced circulation flash evaporator, the lower side of the forced circulation flash evaporator is connected to the forced circulation pump, and the upper left side of the forced circulation flash evaporator is connected to the forced circulation gas phase processor.

[0015] The lower left side of the forced circulation flash evaporator is connected to the third high-temperature pipeline, the lower side of the third high-temperature pipeline is connected to the first acid-acid heat exchanger, and the lower side of the first acid-acid heat exchanger is connected to the hand-transfer tank; the lower left side of the third automatic regulating valve is connected to the first hand-transfer pump.

[0016] The waste sulfuric acid vacuum concentration treatment method comprises the following steps:

[0017] S1. Filling of equipment materials.

[0018] S2. The device establishes a vacuum.

[0019] S3. The device is preheated.

[0020] S4, waste sulfuric acid is added and 96% concentration sulfuric acid is produced.

[0021] S5, produces 91% concentration sulfuric acid.

[0022] S6. Automatic control of device operation.

[0023] S7. The device is forced to clean the circulation section without stopping.

[0024] S8: Reproduction of the forced circulation section without stopping the device.

[0025] As a further solution of the present invention: the left side of the first acid-acid heat exchanger is connected to a second waste sulfuric acid flow meter, and the left side of the second waste sulfuric acid flow meter is connected to a second automatic regulating valve.

[0026] The left side of the second acid-acid heat exchanger is connected to the first waste sulfuric acid flow meter, the left side of the first waste sulfuric acid flow meter is connected to the first automatic regulating valve, and the left sides of the second automatic regulating valve and the first automatic regulating valve are both connected to the waste sulfuric acid feed pipe through pipelines.

[0027] The upper right side of the secondary concentrator is connected to the first pressure transmitter, the lower left side is connected to the first temperature transmitter, the upper side of the high-temperature sulfuric acid tank is connected to the third liquid level meter, and the left side is connected to the second start-up valve.

[0028] The mixed acid tank is connected to the third temperature transmitter on the left side and the mixed acid valve on the lower right side. The lower left pipeline of the low-temperature sulfuric acid pump is connected to the second flushing valve, and the right side is respectively connected to the low-temperature automatic regulating valve and the mixed acid valve.

[0029] As a further solution of the present invention: a first liquid level meter is connected to the upper side of the low-temperature sulfuric acid tank.

[0030] The right side of the second cooler is connected to the left side of the low-temperature automatic regulating valve, the right side of the low-temperature automatic regulating valve is connected to the low-temperature flowmeter, the low-temperature flowmeter is associated with the first high-temperature automatic regulating valve signal, and the second automatic regulating valve is associated with the third liquid level meter signal.

[0031] The lower left side of the forced circulation pump is connected to the first brush valve, and the upper left side of the forced circulation flash evaporator is connected to the second pressure transmitter.

[0032] The upper right side of the forced circulation gas phase processor is connected to a vacuum breaking valve and a switch valve respectively, the left side of the switch valve is connected to a first vacuum pump, the left side of the first vacuum pump is connected to the left side of the secondary gas phase processor, and the upper right side of the secondary gas phase processor is connected to a second vacuum pump.

[0033] The upper side of the hand-transfer trough is connected to a second liquid level meter, and the upper right side is connected to a third automatic regulating valve. The second liquid level meter is signal-correlated with the third automatic regulating valve.

[0034] The lower left side of the first hand pump is connected to the third brushing valve, the lower right side of the third automatic regulating valve is connected to the first start-up valve, and the right side of the first start-up valve is connected to the second start-up valve.

[0035] As a further solution of the present invention: the specific method of filling the device with materials is:

[0036] Through the second automatic regulating valve, the first automatic regulating valve and related pipelines, the first acid-acid heat exchanger, the second acid-acid heat exchanger, the transfer tank, the first cooler, the first transfer pump, the low-temperature sulfuric acid tank, the low-temperature sulfuric acid pump, the denitrification tower, the secondary concentrator, the high-temperature sulfuric acid tank, the high-temperature transfer pump, the forced circulation heater, the forced circulation pump and the forced circulation flash evaporator are filled with 91% concentration of sulfuric acid, and the equipment is sealed to establish a high vacuum to isolate the air.

[0037] The specific method of establishing vacuum in the device is:

[0038] Start the first vacuum pump and the second vacuum pump, so that the value of the first pressure transmitter is between 6.5KPa and 8.5KPa, and the value of the second pressure transmitter is between 1.1KPa and 1.2KPa.

[0039] As a further solution of the present invention: the specific method of preheating the device is:

[0040] Open the first start-up valve and the second start-up valve, start the forced circulation pump and the forced circulation heater, and the forced circulation pump, the forced circulation flash evaporator and the connecting pipelines for forced circulation. At the same time, start the first transfer pump, the low-temperature sulfuric acid pump and the high-temperature transfer pump to circulate 91% sulfuric acid from the high-temperature sulfuric acid tank through the second high-temperature automatic regulating valve, the forced circulation heater, the forced circulation flash evaporator, the third high-temperature pipeline, the first acid-acid heat exchanger, the transfer tank, the first cooler, the first start-up valve, and the second start-up valve to the high-temperature sulfuric acid tank, and heat the denitrification tower to 90℃-100℃, the secondary concentrator to 120℃-130℃, the forced circulation heater, the forced circulation pump and the forced circulation flash evaporator to 120℃-130℃, so that the thermal shock temperature of the device is lower than 70℃.

[0041] As a further solution of the present invention: the specific method of feeding waste sulfuric acid and producing 96% concentration sulfuric acid is:

[0042] Close the first start-up valve and the second start-up valve, open the second automatic regulating valve, and the waste sulfuric acid enters the first acid-acid heat exchanger, denitrification tower, secondary concentrator and high-temperature sulfuric acid tank after being measured by the second waste sulfuric acid flowmeter, and enters the forced circulation system composed of forced circulation pump, forced circulation flash evaporator and forced circulation gas phase processor through the second high-temperature automatic regulating valve and the second high-temperature pipeline. The concentrated sulfuric acid enters the transfer tank after heat exchange with the waste sulfuric acid through the third high-temperature pipeline and the first acid-acid heat exchanger, and is sent to the finished product tank area after being cooled to below 40°C by the first transfer pump and the first cooler.

[0043] Adjust the second automatic regulating valve to make the waste sulfuric acid flow rate measured by the second waste sulfuric acid flow meter gradually increase, and the increase every 30 minutes is ≤1m 3 / h, gradually increase the temperature of the denitrification tower, increase the first temperature transmitter value of the secondary concentrator to 185℃-187℃, and increase the outlet temperature transmitter value of the forced circulation heater to 182℃-185℃.

[0044] As a further solution of the present invention: the specific steps of producing 91% concentration sulfuric acid are:

[0045] S51. Start the heating pipe to raise the temperature of the first high-temperature pipeline to a value of 100°C-120°C on the temperature transmitter.

[0046] S52, open the mixed acid valve, and the cold 91% sulfuric acid from the second cooler enters the mixed acid tank, and enters the low-temperature sulfuric acid tank through the second acid-acid heat exchanger, and circulates to the second cooler through the low-temperature sulfuric acid pump.

[0047] S53, set the value of the first liquid level meter to 50%, set the value of the low-temperature flow meter according to the product quantity, the numerical signal is associated with the first high-temperature automatic regulating valve, slowly adjust the opening of the mixed acid valve, control the value of the third temperature transmitter of the mixed acid tank, and when the value reaches 100°C, close the mixed acid valve.

[0048] S54, calculating and setting the value of the first waste sulfuric acid flow meter according to the value of the low-temperature flow meter, and the value of the first waste sulfuric acid flow meter is associated with the first automatic regulating valve.

[0049] S55, 91% sulfuric acid is cooled to below 40°C in the second cooler and then discharged into the 91% sulfuric acid storage tank.

[0050] As a further solution of the present invention: the automatic control of the operation of the device includes the following method:

[0051] According to the needs of the waste sulfuric acid treatment amount, the value of the second waste sulfuric acid flowmeter is set, the value of the second waste sulfuric acid flowmeter is associated with the second automatic regulating valve, the liquid level of the third liquid level gauge of the high-temperature sulfuric acid tank is set to 50%, the third liquid level gauge is associated with the second high-temperature automatic regulating valve, and the high-temperature 91% sulfuric acid enters the forced circulation heater, the forced circulation pump and the forced circulation flash evaporator according to the liquid level automatic adjustment, the system is concentrated into 96% sulfuric acid, the 96% sulfuric acid enters the transfer tank through the first acid-acid heat exchanger, the second liquid level gauge is set to 50%, the second liquid level gauge signal is associated with the third automatic regulating valve, and the 96% sulfuric acid is cooled to below 40°C by the first cooler and then discharged into the 96% sulfuric acid storage tank.

[0052] As a further solution of the present invention: the specific method of brushing the forced circulation section of the device without stopping is:

[0053] When it is necessary to scrub the forced circulation system composed of the forced circulation heater, forced circulation pump, forced circulation flash evaporator, first acid-acid heat exchanger, transfer tank, first cooler and first transfer pump, stop the system that needs to be scrubbed, turn off the first vacuum pump and the switch valve, open the vacuum breaking valve, drain the sulfuric acid in the system from the first scrubbing valve and the third scrubbing valve, and inject scrubbing water through the first scrubbing valve and the third scrubbing valve for scrubbing. After the scrubbing is completed, drain the scrubbing water through the first scrubbing valve and the third scrubbing valve to complete the scrubbing.

[0054] As a further solution of the present invention: the specific method of reproducing the non-stop forced circulation section of the device is:

[0055] Inject cold 91% sulfuric acid through the first brush valve and the third brush valve, close the vacuum breaker, open the switch valve and the first vacuum pump until the value of the second pressure transmitter reaches 1.2KPa, slowly start the forced circulation heater, forced circulation pump and forced circulation flash evaporator system, control the temperature rise value of the second temperature transmitter to ≤1℃ / min, until the temperature value of the second temperature transmitter reaches above 180℃, open the second high-temperature automatic regulating valve, forced circulation heater, forced circulation pump and forced circulation flash evaporator, and put the system into normal operation.

[0056] The beneficial effects of the present invention are:

[0057] The present invention uses a double acid-acid heat exchanger to recover heat, uses a heat tracing pipe system to preheat the glass-lined pipeline, reduces the temperature difference of the glass-lined pipeline to less than 100° C., protects the glass-lined pipeline, and uses a hot and cold acid mixer to control the acid temperature entering the acid-acid heat exchanger, ensures that the acid temperature rises steadily, and avoids damage to the equipment due to sudden temperature changes. The liquid level-flow control combined control technology is used to achieve double feeding, and automatic control and continuous operation of simultaneously or alternately producing sulfuric acid products with a concentration of 91% and 96%. The whole process is easy to operate, and the sulfuric acid concentration is increased from an average of 95.5% to an average of 96.2%. The production needs of both mononitrotoluene and polynitrotoluene can be met at the same time, and the production cost can be reduced, thereby eliminating the problem of frequent shutdowns due to brushing of a waste sulfuric acid vacuum concentration device and extending the service life of the device.

[0058] The present invention solves the problems of discontinuous production, high equipment failure rate and reduced production capacity of the waste sulfuric acid vacuum concentration device caused by ferric sulfate scaling and frequent brushing, so that the waste sulfuric acid vacuum concentration device can increase the production capacity by 15%, thereby improving the profitability of upstream nitration products, and achieving an annual comprehensive economic benefit of more than 5 million yuan. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 It is a schematic diagram of the structure of the device used in the method for producing waste sulfuric acid of the present invention;

[0060] In the figure: 1, the first acid-acid heat exchanger; 2, the second acid-acid heat exchanger; 3, the hand transfer tank; 4, the first cooler; 5, the first hand transfer pump; 6, the low-temperature sulfuric acid tank; 7, the second cooler; 8, the low-temperature sulfuric acid pump; 9, the secondary concentrator; 10, the secondary gas phase processor; 11, the high-temperature sulfuric acid tank; 12, the high-temperature hand transfer pump; 13, the forced circulation heater; 14, the forced circulation pump; 15, the forced circulation flash evaporator; 16, the forced circulation gas phase processor; 17, the first automatic regulating valve; 18, the first waste sulfuric acid flow meter; 19, the second automatic regulating valve; 20, the second waste sulfuric acid flow meter; 21, the first liquid level meter; 22, the low-temperature automatic regulating valve; 23, the low-temperature flow meter; 24, the first high-temperature automatic regulating valve; 25, the first 2. High-temperature automatic regulating valve; 26. First high-temperature pipeline; 27. Second high-temperature pipeline; 28. Third high-temperature pipeline; 29. ​​Second liquid level gauge; 30. Third automatic regulating valve; 31. First pressure transmitter; 32. First temperature transmitter; 33. Second pressure transmitter, 34. Second temperature transmitter; 35. First flushing valve; 36. Second flushing valve; 37. Third flushing valve; 38. Switch valve; 39. First vacuum pump; 40. Second vacuum pump; 41. Denitration tower; 42. First start-up valve; 43. Second start-up valve; 44. Mixed acid valve; 45 Mixed acid tank; 46. Third temperature transmitter; 47. Fourth temperature transmitter; 48. Heat tracing pipe; 49 Third liquid level gauge; 50. Vacuum breaking valve. DETAILED DESCRIPTION

[0061] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. 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.

[0062] A method for producing sulfuric acid by vacuum concentrating waste sulfuric acid, comprising a waste sulfuric acid treatment device, the waste sulfuric acid treatment device comprising a first acid-acid heat exchanger 1, the first acid-acid heat exchanger 1 and the second acid-acid heat exchanger 2 are both connected to the upper left side of a denitrification tower 41, the upper side of the denitrification tower 41 is connected to a gas pipeline, the lower right side of the denitrification tower 41 is connected to the lower left side of a secondary concentrator 9, the upper right side of the secondary concentrator 9 is connected to a secondary gas phase processor 10, and the lower right side of the secondary concentrator 9 is connected to a high-temperature sulfuric acid tank 11.

[0063] The high-temperature sulfuric acid tank 11 is connected to the high-temperature hand pump 12 on the right side, and the high-temperature hand pump 12 is connected to the first high-temperature automatic regulating valve 24 on the right side. The first high-temperature automatic regulating valve 24 is connected to the first high-temperature pipeline 26 on the upper side. The first high-temperature pipeline 26 is a glass-lined pipe. The first high-temperature pipeline 26 is connected to the fourth temperature transmitter 47 on the left side. A heating pipe 48 is provided on the right side and the upper side of the first high-temperature pipeline 26. The left side of the heating pipe 48 is connected to the mixed acid tank 45. The heating pipe 48 is provided to heat the cold glass-lined pipe to 100°C-120°C to meet the sudden delivery of 180°C sulfuric acid by the first high-temperature pipeline 26, ensuring that the first high-temperature pipeline 26 is not exploded by thermal shock. The mixed acid tank 45, the first high-temperature pipeline 26, and the mixed acid valve 44 constitute a mixed acid system, which is used to slowly and steadily increase the temperature of 91% sulfuric acid in the mixed acid tank 45 to prevent the second acid-acid heat exchanger 2 from being damaged by thermal shock.

[0064] The lower side of the mixed acid tank 45 is connected to the second acid-acid heat exchanger 2, and the lower side of the second acid-acid heat exchanger 2 is connected to the low-temperature sulfuric acid tank 6; the lower left side of the low-temperature sulfuric acid tank 6 is connected to the low-temperature sulfuric acid pump 8, and the right side of the low-temperature sulfuric acid pump 8 is connected to the second cooler 7. The low-temperature sulfuric acid tank 6, the second cooler 7, the low-temperature sulfuric acid pump 8, the mixed acid tank 45, the first high-temperature automatic regulating valve 24 and connecting pipelines, the first pressure transmitter 31, the first temperature transmitter 32, the second pressure transmitter 33, the second temperature transmitter 34, the third temperature transmitter 46 and the fourth temperature transmitter 47 constitute a 91% sulfuric acid product system for simultaneously producing 91% sulfuric acid.

[0065] The right side of the high-temperature transfer pump 12 is connected to the second high-temperature automatic regulating valve 25, the upper side of the second high-temperature automatic regulating valve 25 is connected to the second high-temperature pipeline 27, the upper side of the second high-temperature pipeline 27 is connected to the forced circulation heater 13, the upper left side of the forced circulation heater 13 is respectively connected to the second temperature transmitter 34 and the forced circulation flash evaporator 15, the lower side of the forced circulation flash evaporator 15 is connected to the forced circulation pump 14, the upper left side of the forced circulation flash evaporator 15 is connected to the forced circulation gas phase processor 16, the forced circulation heater 13, the forced circulation pump 14, the forced circulation flash evaporator 15, the first acid-acid heat exchanger 1, the transfer tank 3, the first cooler 4 and the first transfer pump 5 constitute a forced circulation system for producing 96% sulfuric acid.

[0066] The lower left side of the forced circulation flash evaporator 15 is connected to the third high-temperature pipeline 28, the lower side of the third high-temperature pipeline 28 is connected to the first acid-acid heat exchanger 1, and the lower side of the first acid-acid heat exchanger 1 is connected to the transfer tank 3; the lower left side of the third automatic regulating valve 30 is connected to the first transfer pump 5.

[0067] The left side of the first acid-acid heat exchanger 1 is connected to the second waste sulfuric acid flow meter 20 , and the left side of the second waste sulfuric acid flow meter 20 is connected to the second automatic regulating valve 19 .

[0068] The left side of the second acid-acid heat exchanger 2 is connected to the first waste sulfuric acid flow meter 18, the left side of the first waste sulfuric acid flow meter 18 is connected to the first automatic regulating valve 17, and the second automatic regulating valve 19 and the left side of the first automatic regulating valve 17 are both connected to the waste sulfuric acid feed pipe through pipelines.

[0069] The upper right side of the secondary concentrator 9 is connected to the first pressure transmitter 31, the lower left side is connected to the first temperature transmitter 32, the upper side of the high-temperature sulfuric acid tank 11 is connected to the third liquid level gauge 49, and the left side is connected to the second start-up valve 43. The third liquid level gauge 49 feeds back the liquid level signal to the high-temperature hand pump 12 outlet to the second high-temperature automatic regulating valve 25 of the last section 96%. The second high-temperature automatic regulating valve 25 automatically adjusts to the 91% sulfuric acid amount of the last section 96% according to the set liquid level. The second liquid level gauge 29 feeds back the liquid level signal to the third automatic regulating valve 30. The third automatic regulating valve 30 automatically adjusts according to the liquid level setting value. The waste sulfuric acid from the second automatic regulating valve 19 exchanges heat with the high-temperature 96% concentration sulfuric acid to recover heat. The flow value of the second waste sulfuric acid flow meter 20 is set according to the product 96% sulfuric acid flow value. The flow signal of the second waste sulfuric acid flow meter 20 is fed back to the second automatic regulating valve 19 to automatically complete the production of 96% sulfuric acid products.

[0070] The left side of the mixed acid tank 45 is connected to the third temperature transmitter 46, and the lower right side is connected to the mixed acid valve 44. The lower left pipeline of the low-temperature sulfuric acid pump 8 is connected to the second flushing valve 36, and the right side is respectively connected to the low-temperature automatic regulating valve 22 and the mixed acid valve 44.

[0071] The upper side of the low-temperature sulfuric acid tank 6 is connected to a first liquid level meter 21 .

[0072] The right side of the second cooler 7 is connected to the left side of the low-temperature automatic regulating valve 22, and the right side of the low-temperature automatic regulating valve 22 is connected to the low-temperature flowmeter 23. The low-temperature flowmeter 23 is associated with the signal of the first high-temperature automatic regulating valve 24. The automatic regulating valve 2 is associated with the signal of the third liquid level meter 49. The low-temperature flowmeter 23 sets the flow value, and the flow signal is fed back to the first high-temperature automatic regulating valve 24. The automatic regulating valve automatically adjusts, and the first liquid level meter 21 feeds back the liquid level signal to the low-temperature automatic regulating valve 22. The low-temperature automatic regulating valve 22 automatically adjusts according to the liquid level setting value. The waste sulfuric acid from the first automatic regulating valve 17 exchanges heat with hot 91% concentration sulfuric acid to recover heat. The flow value of the waste acid first waste sulfuric acid flowmeter 18 is set according to the conversion of the product 91% sulfuric acid flow value. The flow signal of the waste acid first waste sulfuric acid flowmeter 18 is fed back to the first automatic regulating valve 17 to automatically complete the production of 91% sulfuric acid products.

[0073] The lower left side of the forced circulation pump 14 is connected to the first flushing valve 35 , and the upper left side of the forced circulation flash evaporator 15 is connected to the second pressure transmitter 33 .

[0074] The upper right side of the forced circulation gas phase processor 16 is connected to the vacuum breaking valve 50 and the switch valve 38 respectively, the left side of the switch valve 38 is connected to the first vacuum pump 39, the left side of the first vacuum pump 39 is connected to the left side of the secondary gas phase processor 10, and the upper right side of the secondary gas phase processor 10 is connected to the second vacuum pump 40.

[0075] The upper side of the hand-transfer tank 3 is connected to the second liquid level meter 29 , and the upper right side is connected to the third automatic regulating valve 30 . The second liquid level meter 29 is signal-linked to the third automatic regulating valve 30 .

[0076] The lower left side of the first hand pump 5 is connected to the third brushing valve 37 , the lower right side of the third automatic regulating valve 30 is connected to the first start-up valve 42 , and the right side of the first start-up valve 42 is connected to the second start-up valve 43 . Example

[0077] The waste sulfuric acid vacuum concentration treatment method comprises the following steps:

[0078] S1. Material filling of the device: through the second automatic regulating valve 19, the first automatic regulating valve 17 and related pipelines, the first acid-acid heat exchanger 1, the second acid-acid heat exchanger 2, the transfer tank 3, the first cooler 4, the first transfer pump 5, the low-temperature sulfuric acid tank 6, the low-temperature sulfuric acid pump 8, the denitrification tower 41, the secondary concentrator 9, the high-temperature sulfuric acid tank 11, the high-temperature transfer pump 12, the forced circulation heater 13, the forced circulation pump 14 and the forced circulation flash evaporator 15 are filled with 91% concentration of sulfuric acid, and the equipment is sealed to establish a high vacuum to isolate the air.

[0079] S2. The device establishes vacuum: the first vacuum pump 39 and the second vacuum pump 40 are started to make the value of the first pressure transmitter 31 between 6.5 KPa and 8.5 KPa, and the value of the second pressure transmitter 33 between 1.1 KPa and 1.2 KPa.

[0080] S3, preheating and heating of the device: open the first start-up valve 42 and the second start-up valve 43, start the forced circulation pump 14 and the forced circulation heater 13, and the forced circulation pump 14, the forced circulation flash evaporator 15 and the connecting pipelines for forced circulation, and at the same time start the first transfer pump 5, the low-temperature sulfuric acid pump 8 and the high-temperature transfer pump 12, so that 91% sulfuric acid is circulated from the high-temperature sulfuric acid tank 11 through the second high-temperature automatic regulating valve 25, the forced circulation heater 13, the forced circulation flash evaporator 15, the third high-temperature pipeline 28, the first acid-acid heat exchanger 1, the transfer tank 3, the first cooler 4, the first start-up valve 42, and the second start-up valve 43 to the high-temperature sulfuric acid tank 11, and the denitrification tower 41 is heated to 90℃-100℃, the secondary concentrator 9 is heated to 120℃-130℃, the forced circulation heater 13, the forced circulation pump 14 and the forced circulation flash evaporator 15 are all heated to 120℃-130℃, so that the thermal shock temperature of the device is lower than 70℃.

[0081] S4, feeding of waste sulfuric acid and production of 96% concentration sulfuric acid: close the first start-up valve 42 and the second start-up valve 43, open the second automatic regulating valve 19, the waste sulfuric acid is measured by the second waste sulfuric acid flowmeter 20 and enters the first acid-acid heat exchanger 1, the denitrification tower 41, the secondary concentrator 9 and the high-temperature sulfuric acid tank 11, and enters the forced circulation system composed of the forced circulation pump 14, the forced circulation flash evaporator 15 and the forced circulation gas phase processor 16 through the second high-temperature automatic regulating valve 25 and the second high-temperature pipeline 27. The concentrated sulfuric acid is heat exchanged with the waste sulfuric acid through the third high-temperature pipeline 28 and the first acid-acid heat exchanger 1 and enters the transfer tank 3, and is cooled to below 40°C by the first transfer pump 5 and the first cooler 4 and then sent to the finished product tank area.

[0082] The second automatic regulating valve 19 is adjusted to gradually increase the measured flow rate of waste sulfuric acid through the second waste sulfuric acid flowmeter 20, with the increase of ≤1m3 / h every 30 minutes, gradually increase the temperature of the denitrification tower 41, increase the value of the first temperature transmitter 32 of the secondary concentrator 9 to 185℃-187℃, and increase the value of the outlet temperature transmitter of the forced circulation heater 13 to 182℃-185℃.

[0083] S5. Produce 91% sulfuric acid: S51. Start the heat tracing pipe 48 to raise the temperature of the first high-temperature pipeline 26 to a value of 100° C. to 120° C. on the temperature transmitter.

[0084] S52, open the mixed acid valve 44, the cold 91% sulfuric acid from the second cooler 7 enters the mixed acid tank 45, and enters the low-temperature sulfuric acid tank 6 through the second acid-acid heat exchanger 2, and circulates to the second cooler 7 through the low-temperature sulfuric acid pump 8.

[0085] S53, set the value of the first liquid level meter 21 to 50%, set the value of the low-temperature flow meter 23 according to the product quantity, the numerical signal is associated with the first high-temperature automatic regulating valve 24, slowly adjust the opening of the mixed acid valve 44, control the value of the third temperature transmitter 46 of the mixed acid tank 45, and when the value reaches 100°C, close the mixed acid valve 44.

[0086] S54 , calculating and setting the value of the first waste sulfuric acid flow meter 18 according to the value of the low-temperature flow meter 23 , and the value of the first waste sulfuric acid flow meter 18 is associated with the first automatic regulating valve 17 .

[0087] S55, 91% sulfuric acid is cooled to below 40°C by the second cooler 7 and then discharged into the 91% sulfuric acid storage tank.

[0088] S6. Automatic control of device operation: according to the needs of the waste sulfuric acid treatment amount, the value of the second waste sulfuric acid flow meter 20 is set, the value of the second waste sulfuric acid flow meter 20 is associated with the second automatic regulating valve 19, the liquid level of the third liquid level gauge 49 of the high-temperature sulfuric acid tank 11 is set to 50%, the third liquid level gauge 49 is associated with the second high-temperature automatic regulating valve 25, and the high-temperature 91% sulfuric acid is automatically adjusted to enter the forced circulation heater 13, the forced circulation pump 14 and the forced circulation flash evaporator 15 according to the liquid level, and the system is concentrated into 96% sulfuric acid. The 96% sulfuric acid enters the transfer tank 3 through the first acid-acid heat exchanger 1, the second liquid level gauge 29 is set to 50%, and the signal of the second liquid level gauge 29 is associated with the third automatic regulating valve 30. The 96% sulfuric acid is cooled to below 40° C. by the first cooler 4 and then discharged into the 96% sulfuric acid storage tank.

[0089] S7. Washing the forced circulation section without stopping the device: When it is necessary to wash the forced circulation system consisting of the forced circulation heater 13, the forced circulation pump 14, the forced circulation flash evaporator 15, the first acid-acid heat exchanger 1, the transfer tank 3, the first cooler 4 and the first transfer pump 5, stop the system that needs to be washed, turn off the first vacuum pump 39 and the switch valve 38, open the vacuum breaking valve 50, drain the sulfuric acid in the system from the first washing valve 35 and the third washing valve 37, and inject washing water through the first washing valve 35 and the third washing valve 37 for washing. After the washing is completed, drain the washing water through the first washing valve 35 and the third washing valve 37 to complete the washing.

[0090] S8. Reproduction of the forced circulation section without stopping the device: inject cold 91% sulfuric acid through the first brush valve 35 and the third brush valve 37, close the vacuum breaker 50, open the switch valve 38 and the first vacuum pump 39 until the value of the second pressure transmitter 33 reaches 1.2KPa, slowly start the forced circulation heater 13, forced circulation pump 14 and forced circulation flash evaporator 15 system, control the temperature rise value of the second temperature transmitter 34 to ≤1℃ / min, until the temperature value of the second temperature transmitter 34 reaches above 180℃, open the second high-temperature automatic regulating valve 25, forced circulation heater 13, forced circulation pump 14 and forced circulation flash evaporator 15, and put the system into normal operation. Example

[0091] The low-temperature flowmeter 23 sets the flow value, and the flow signal is fed back to the first high-temperature automatic regulating valve 24, and the automatic regulating valve automatically adjusts. The first liquid level meter 21 feeds back the liquid level signal to the low-temperature automatic regulating valve 22, and the low-temperature automatic regulating valve 22 automatically adjusts according to the liquid level setting value. The waste sulfuric acid from the first automatic regulating valve 17 exchanges heat with hot 91% concentration sulfuric acid to recover heat. The flow value of the waste acid first waste sulfuric acid flowmeter 18 is set according to the product 91% sulfuric acid flow value. The flow signal of the waste acid first waste sulfuric acid flowmeter 18 is fed back to the first automatic regulating valve 17, and the production of 91% sulfuric acid product is automatically completed. Example

[0092] The third liquid level meter 49 feeds back the liquid level signal to the second high temperature automatic regulating valve 25 from the outlet of the high temperature hand pump 12 to the last section 96%. The second high temperature automatic regulating valve 25 automatically adjusts to the 91% sulfuric acid amount of the last section 96% according to the set liquid level. The second liquid level meter 29 feeds back the liquid level signal to the third automatic regulating valve 30. The third automatic regulating valve 30 automatically adjusts according to the liquid level setting value. The waste sulfuric acid from the second automatic regulating valve 19 exchanges heat with the high temperature 96% concentration sulfuric acid to recover heat. The flow value of the second waste sulfuric acid flow meter 20 is set according to the conversion of the product 96% sulfuric acid flow value. The flow signal of the second waste sulfuric acid flow meter 20 is fed back to the second automatic regulating valve 19 to automatically complete the production of 96% sulfuric acid products. Example

[0093] When it is necessary to scrub the 96% sulfuric acid forced circulation system consisting of the forced circulation heater 13, the forced circulation pump 14, the forced circulation flash evaporator 15, the first acid-acid heat exchanger 1, the transfer tank 3, the first cooler 4 and the first transfer pump 5, the system that needs to be scrubbed is stopped, the first vacuum pump 39 and the switch valve 38 are turned off, and the vacuum breaking valve 50 is opened to allow the 91% sulfuric acid product to continue to be produced, and the forced circulation system is scrubbed to ensure that the waste sulfuric acid vacuum concentrator continues to treat the waste sulfuric acid. Example

[0094] When it is necessary to restore the production of 96% sulfuric acid, cold 91% sulfuric acid is injected through the first brush valve 35 and the third brush valve 37, the vacuum breaker 50 is closed, the switch valve 38 and the first vacuum pump 39 are opened until the value of the second pressure transmitter 33 reaches 1.2KPa, and then the forced circulation heater 13, the forced circulation pump 14 and the forced circulation flash evaporator 15 system are slowly started, and the temperature rise value of the second temperature transmitter 34 is controlled to be ≤1°C / min. When the temperature value of the second temperature transmitter 34 reaches above 180°C, the second high-temperature automatic regulating valve 25 is opened to restore the production of 96% sulfuric acid in the waste sulfuric acid forced circulation system.

[0095] In summary, the present invention uses a dual acid-acid heat exchanger to recover heat, uses a heat tracing pipe 48 system to preheat the glass-lined pipeline, reduces the temperature difference of the glass-lined pipeline to less than 100° C., protects the glass-lined pipeline, and uses a hot and cold acid mixer to control the acid temperature entering the acid-acid heat exchanger, ensures that the acid temperature rises steadily, and avoids damage to the equipment due to sudden temperature changes. The liquid level-flow control combined control technology is used to achieve dual feeding, and automatic control continuous operation of simultaneously or alternately producing 91% and 96% sulfuric acid products is achieved. The whole process is easy to operate, and the sulfuric acid concentration is increased from an average of 95.5% to an average of 96.2%. The needs of the production of two products, mononitrotoluene and polynitrotoluene, can be met at the same time, and the production cost can be reduced, thereby eliminating the frequent shutdown problem of the waste sulfuric acid vacuum concentration device for brushing, and extending the service life of the device. At the same time, the waste sulfuric acid vacuum concentration treatment device can simultaneously produce 91% sulfuric acid and sulfuric acid with a concentration of more than 96%, or continuously and alternately produce 91% sulfuric acid or 96% sulfuric acid.

[0096] The problem of discontinuous production, high equipment failure rate and reduced production capacity caused by ferric sulfate scaling and frequent cleaning in the waste sulfuric acid vacuum concentration unit has been solved. The production capacity of the waste sulfuric acid vacuum concentration unit can be increased by 15%, thereby improving the profitability of upstream nitration products and achieving an annual comprehensive economic benefit of more than 5 million yuan.

[0097] Finally, a few points should be explained: Although the present invention has been described in detail above with general descriptions and specific embodiments, on the basis of the present invention, the above embodiments are only used to illustrate the technical solution of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the aforementioned embodiments, ordinary technicians in this field should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for producing sulfuric acid by vacuum concentrating waste sulfuric acid, comprising a waste sulfuric acid treatment device, characterized in that: The waste sulfuric acid treatment device comprises a first acid-acid heat exchanger (1), the first acid-acid heat exchanger (1) and the second acid-acid heat exchanger (2) are both connected to the upper left side of a denitrification tower (41), the upper side of the denitrification tower (41) is connected to a gas pipeline, the lower right side of the denitrification tower (41) is connected to the lower left side of a secondary concentrator (9), the upper right side of the secondary concentrator (9) is connected to a secondary gas phase processor (10), and the lower right side of the secondary concentrator (9) is connected to a high-temperature sulfuric acid tank (11); The high-temperature sulfuric acid tank (11) is connected to a high-temperature hand pump (12) on the right side, the high-temperature hand pump (12) is connected to a first high-temperature automatic regulating valve (24) on the right side, the first high-temperature automatic regulating valve (24) is connected to a first high-temperature pipeline (26) on the upper side, the first high-temperature pipeline (26) is a glass-lined pipe, the first high-temperature pipeline (26) is connected to a fourth temperature transmitter (47) on the left side, the first high-temperature pipeline (26) is provided with a heat tracing pipe (48) on the right side and the upper side, and the heat tracing pipe (48) is connected to the mixed acid tank (45) on the left side; The lower side of the mixed acid tank (45) is connected to the second acid-acid heat exchanger (2), and the lower side of the second acid-acid heat exchanger (2) is connected to the low-temperature sulfuric acid tank (6); the lower left side of the low-temperature sulfuric acid tank (6) is connected to a low-temperature sulfuric acid pump (8), and the right side of the low-temperature sulfuric acid pump (8) is connected to a second cooler (7); The right side of the high-temperature hand pump (12) is connected to a second high-temperature automatic regulating valve (25), the upper side of the second high-temperature automatic regulating valve (25) is connected to a second high-temperature pipeline (27), the upper side of the second high-temperature pipeline (27) is connected to a forced circulation heater (13), the upper left side of the forced circulation heater (13) is respectively connected to a second temperature transmitter (34) and a forced circulation flash evaporator (15), the lower side of the forced circulation flash evaporator (15) is connected to a forced circulation pump (14), and the upper left side of the forced circulation flash evaporator (15) is connected to a forced circulation gas phase processor (16); The lower left side of the forced circulation flash evaporator (15) is connected to the third high-temperature pipeline (28), the lower side of the third high-temperature pipeline (28) is connected to the first acid-acid heat exchanger (1), and the lower side of the first acid-acid heat exchanger (1) is connected to the hand-transfer tank (3); the lower left side of the third automatic regulating valve (30) is connected to the first hand-transfer pump (5); The upper side of the low-temperature sulfuric acid tank (6) is connected to a first liquid level meter (21); The right side of the second cooler (7) is connected to the left side of the low-temperature automatic regulating valve (22), the right side of the low-temperature automatic regulating valve (22) is connected to the low-temperature flow meter (23), the low-temperature flow meter (23) is associated with the signal of the first high-temperature automatic regulating valve (24), and the second automatic regulating valve is associated with the signal of the third liquid level meter (49); The lower left side of the forced circulation pump (14) is connected to a first flushing valve (35), and the upper left side of the forced circulation flash evaporator (15) is connected to a second pressure transmitter (33); The upper right side of the forced circulation gas phase processor (16) is respectively connected to a vacuum breaking valve (50) and a switch valve (38); the left side of the switch valve (38) is connected to a first vacuum pump (39); the left side of the first vacuum pump (39) is connected to the left side of the secondary gas phase processor (10); and the upper right side of the secondary gas phase processor (10) is connected to a second vacuum pump (40); The upper side of the hand-transfer trough (3) is connected to a second liquid level meter (29), and the upper right side is connected to a third automatic regulating valve (30), and the second liquid level meter (29) is signal-linked to the third automatic regulating valve (30); The lower left side of the first hand pump (5) is connected to a third scrubbing valve (37), the lower right side of the third automatic regulating valve (30) is connected to a first start-up valve (42), and the right side of the first start-up valve (42) is connected to a second start-up valve (43); The waste sulfuric acid vacuum concentration treatment method comprises the following steps: S1, device material filling; S2, the device establishes a vacuum; S3, preheating the device; S4, waste sulfuric acid feeding and production of 96% concentration sulfuric acid; S5, producing 91% concentration sulfuric acid; S6. Automatic control of device operation; S7, the device is not stopped and the forced circulation section is brushed; S8: Reproduction of the forced circulation section without stopping the device.

2. The method for producing sulfuric acid by vacuum concentration of waste sulfuric acid according to claim 1, characterized in that: The left side of the first acid-acid heat exchanger (1) is connected to a second waste sulfuric acid flow meter (20), and the left side of the second waste sulfuric acid flow meter (20) is connected to a second automatic regulating valve (19); The left side of the second acid-acid heat exchanger (2) is connected to the first waste sulfuric acid flow meter (18), the left side of the first waste sulfuric acid flow meter (18) is connected to the first automatic regulating valve (17), and the left sides of the second automatic regulating valve (19) and the first automatic regulating valve (17) are both connected to the waste sulfuric acid feed pipe through pipelines; The upper right side of the secondary concentrator (9) is connected to a first pressure transmitter (31), the lower left side is connected to a first temperature transmitter (32), the upper side of the high-temperature sulfuric acid tank (11) is connected to a third liquid level gauge (49), and the left side is connected to a second start-up valve (43); The mixed acid tank (45) is connected to the third temperature transmitter (46) on the left side and the mixed acid valve (44) on the lower right side. The low-temperature sulfuric acid pump (8) is connected to the second scrubbing valve (36) on the lower left side of the pipeline and is respectively connected to the low-temperature automatic regulating valve (22) and the mixed acid valve (44) on the right side.

3. The method for producing sulfuric acid by vacuum concentration of waste sulfuric acid according to claim 2, characterized in that: The specific method of filling the device with materials is: The first acid-acid heat exchanger (1), the second acid-acid heat exchanger (2), the hand-transfer tank (3), the first cooler (4), the first hand-transfer pump (5), the low-temperature sulfuric acid tank (6), the low-temperature sulfuric acid pump (8), the denitrification tower (41), the secondary concentrator (9), the high-temperature sulfuric acid tank (11), the high-temperature hand-transfer pump (12), the forced circulation heater (13), the forced circulation pump (14) and the forced circulation flash evaporator (15) are filled with sulfuric acid with a concentration of 91% through the second automatic regulating valve (19), the first automatic regulating valve (17) and the related pipelines, and the equipment is sealed to establish a high vacuum to isolate the air; The specific method of establishing vacuum in the device is: The first vacuum pump (39) and the second vacuum pump (40) are started so that the value of the first pressure transmitter (31) is between 6.5 KPa and 8.5 KPa, and the value of the second pressure transmitter (33) is between 1.1 KPa and 1.2 KPa.

4. The method for producing sulfuric acid by vacuum concentration of waste sulfuric acid according to claim 3, characterized in that: The specific method of preheating the device is as follows: The first start-up valve (42) and the second start-up valve (43) are opened, and the forced circulation pump (14) and the forced circulation heater (13) are started. The forced circulation pump (14), the forced circulation flash evaporator (15) and the connecting pipelines are forced to circulate. At the same time, the first transfer pump (5), the low-temperature sulfuric acid pump (8) and the high-temperature transfer pump (12) are started to allow 91% sulfuric acid to flow from the high-temperature sulfuric acid tank (11) through the second high-temperature automatic regulating valve (25), the forced circulation heater (13), the forced circulation flash evaporator (15), the third ... The hot pipeline (28), the first acid-acid heat exchanger (1), the transfer tank (3), the first cooler (4), the first start-up valve (42), and the second start-up valve (43) are circulated to the high-temperature sulfuric acid tank (11), and the denitrification tower (41) is heated to 90°C-100°C, the secondary concentrator (9) is heated to 120°C-130°C, and the forced circulation heater (13), the forced circulation pump (14) and the forced circulation flash evaporator (15) are all heated to 120°C-130°C, so that the thermal shock temperature of the device is lower than 70°C.

5. The method for producing sulfuric acid by vacuum concentration of waste sulfuric acid according to claim 4, characterized in that: The specific method of feeding the waste sulfuric acid and producing 96% concentration sulfuric acid is as follows: The first start-up valve (42) and the second start-up valve (43) are closed, and the second automatic regulating valve (19) is opened. The waste sulfuric acid is metered by the second waste sulfuric acid flow meter (20) and enters the first acid-acid heat exchanger (1), the denitrification tower (41), the secondary concentrator (9) and the high-temperature sulfuric acid tank (11). It enters the forced circulation system consisting of the forced circulation pump (14), the forced circulation flash evaporator (15) and the forced circulation gas phase processor (16) through the second high-temperature automatic regulating valve (25) and the second high-temperature pipeline (27). The concentrated sulfuric acid is exchanged with the waste sulfuric acid through the third high-temperature pipeline (28) and the first acid-acid heat exchanger (1) and then enters the transfer tank (3). It is cooled to below 40° C. by the first transfer pump (5) and the first cooler (4) and then sent to the finished product tank area. The second automatic regulating valve (19) is adjusted so that the waste sulfuric acid flows through the second waste sulfuric acid flow meter (20) so that the measured waste sulfuric acid flow rate gradually increases, and the increase is ≤1m every 30 minutes. 3 / h, gradually increase the temperature of the denitrification tower (41), increase the value of the first temperature transmitter (32) of the secondary concentrator (9) to 185°C-187°C, and increase the value of the outlet temperature transmitter of the forced circulation heater (13) to 182°C-185°C.

6. The method for producing sulfuric acid by vacuum concentration of waste sulfuric acid according to claim 5, characterized in that: The specific steps of producing 91% concentration sulfuric acid are: S51, starting the heating pipe (48) to raise the temperature of the first high-temperature pipeline (26) to a value of 100° C. to 120° C. on the temperature transmitter; S52, opening the mixed acid valve (44), allowing the cold 91% sulfuric acid from the second cooler (7) to enter the mixed acid tank (45), and then enter the low-temperature sulfuric acid tank (6) through the second acid-acid heat exchanger (2), and then circulate to the second cooler (7) through the low-temperature sulfuric acid pump (8); S53, setting the value of the first liquid level meter (21) to 50%, setting the value of the low-temperature flow meter (23) according to the product quantity, the value signal is associated with the first high-temperature automatic regulating valve (24), slowly adjusting the opening of the mixed acid valve (44), controlling the value of the third temperature transmitter (46) of the mixed acid tank (45), and when the value reaches 100° C., closing the mixed acid valve (44); S54, calculating and setting the value of the first waste sulfuric acid flow meter (18) according to the value of the low temperature flow meter (23), wherein the value of the first waste sulfuric acid flow meter (18) is associated with the first automatic regulating valve (17); S55, 91% sulfuric acid is cooled to below 40°C by the second cooler (7) and then discharged into the 91% sulfuric acid storage tank.

7. The method for producing sulfuric acid by vacuum concentration of waste sulfuric acid according to claim 6, characterized in that: The automatic control of the operation of the device includes the following methods: According to the need of the waste sulfuric acid treatment amount, the value of the second waste sulfuric acid flow meter (20) is set, and the value of the second waste sulfuric acid flow meter (20) is associated with the second automatic regulating valve (19). The liquid level of the third liquid level meter (49) of the high-temperature sulfuric acid tank (11) is set to 50%, and the third liquid level meter (49) is associated with the second high-temperature automatic regulating valve (25). According to the liquid level, the high-temperature 91% sulfuric acid is automatically adjusted to enter the forced circulation heater (13), the forced circulation pump (14) and the forced circulation flash evaporator (15). The system is concentrated into 96% sulfuric acid. The 96% sulfuric acid enters the transfer tank (3) through the first acid-acid heat exchanger (1). The second liquid level meter (29) is set to 50%, and the signal of the second liquid level meter (29) is associated with the third automatic regulating valve (30). The 96% sulfuric acid is cooled to below 40° C. through the first cooler (4) and then discharged into the 96% sulfuric acid storage tank.

8. The method for producing sulfuric acid by vacuum concentration of waste sulfuric acid according to claim 7, characterized in that: The specific method of brushing the forced circulation section of the device without stopping is: When it is necessary to scrub the forced circulation system composed of the forced circulation heater (13), the forced circulation pump (14), the forced circulation flash evaporator (15), the first acid-acid heat exchanger (1), the hand-transfer tank (3), the first cooler (4) and the first hand-transfer pump (5), the system to be scrubbed is stopped, the first vacuum pump (39) and the switch valve (38) are turned off, the vacuum breaking valve (50) is opened, the sulfuric acid in the system is drained from the first scrubbing valve (35) and the third scrubbing valve (37), and scrubbing water is injected through the first scrubbing valve (35) and the third scrubbing valve (37) for scrubbing. After the scrubbing is completed, the scrubbing water is drained through the first scrubbing valve (35) and the third scrubbing valve (37), and the scrubbing is completed.

9. The method for producing sulfuric acid by vacuum concentration of waste sulfuric acid according to claim 8, characterized in that: The specific method of reproducing the non-stop forced circulation section of the device is: Cold 91% sulfuric acid is injected through the first brush valve (35) and the third brush valve (37), the vacuum breaker valve (50) is closed, the switch valve (38) and the first vacuum pump (39) are opened until the value of the second pressure transmitter (33) reaches 1.2 KPa, the forced circulation heater (13), the forced circulation pump (14) and the forced circulation flash evaporator (15) system are slowly started, the temperature rise value of the second temperature transmitter (34) is controlled to be ≤1°C / min, until the temperature value of the second temperature transmitter (34) reaches above 180°C, the second high temperature automatic regulating valve (25), the forced circulation heater (13), the forced circulation pump (14) and the forced circulation flash evaporator (15) are opened, and the system is put into normal operation.

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