CN114455551A - Concentration and reuse device for chlorine gas drying waste acid and control method thereof - Google Patents
Concentration and reuse device for chlorine gas drying waste acid and control method thereof Download PDFInfo
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- CN114455551A CN114455551A CN202210127047.9A CN202210127047A CN114455551A CN 114455551 A CN114455551 A CN 114455551A CN 202210127047 A CN202210127047 A CN 202210127047A CN 114455551 A CN114455551 A CN 114455551A
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- 239000002253 acid Substances 0.000 title claims abstract description 131
- 239000002699 waste material Substances 0.000 title claims abstract description 50
- 238000000034 method Methods 0.000 title claims abstract description 35
- 238000001035 drying Methods 0.000 title claims abstract description 22
- KZBUYRJDOAKODT-UHFFFAOYSA-N Chlorine Chemical compound ClCl KZBUYRJDOAKODT-UHFFFAOYSA-N 0.000 title claims abstract description 10
- 238000004064 recycling Methods 0.000 claims abstract description 28
- 238000005406 washing Methods 0.000 claims abstract description 25
- 239000012071 phase Substances 0.000 claims abstract description 22
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 claims abstract description 18
- 229910052801 chlorine Inorganic materials 0.000 claims abstract description 18
- 239000000460 chlorine Substances 0.000 claims abstract description 18
- 239000002994 raw material Substances 0.000 claims abstract description 16
- 239000007921 spray Substances 0.000 claims abstract description 12
- 239000007791 liquid phase Substances 0.000 claims abstract description 9
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 108
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 44
- 239000002351 wastewater Substances 0.000 claims description 16
- 239000007788 liquid Substances 0.000 claims description 13
- 238000009833 condensation Methods 0.000 claims description 8
- 230000005494 condensation Effects 0.000 claims description 8
- 238000002347 injection Methods 0.000 claims description 7
- 239000007924 injection Substances 0.000 claims description 7
- 229910052715 tantalum Inorganic materials 0.000 claims description 7
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 claims description 7
- 230000002378 acidificating effect Effects 0.000 claims description 6
- 238000001816 cooling Methods 0.000 claims description 6
- 239000006260 foam Substances 0.000 claims description 5
- 238000010438 heat treatment Methods 0.000 claims description 5
- 239000000110 cooling liquid Substances 0.000 claims description 4
- 239000000203 mixture Substances 0.000 claims description 4
- 238000005086 pumping Methods 0.000 claims description 3
- 238000000926 separation method Methods 0.000 claims description 3
- 238000005507 spraying Methods 0.000 claims description 3
- 239000012224 working solution Substances 0.000 claims description 3
- 230000006835 compression Effects 0.000 claims description 2
- 238000007906 compression Methods 0.000 claims description 2
- 238000001704 evaporation Methods 0.000 claims description 2
- 230000008020 evaporation Effects 0.000 claims description 2
- 238000002156 mixing Methods 0.000 claims description 2
- 230000007613 environmental effect Effects 0.000 abstract description 4
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 18
- 239000000047 product Substances 0.000 description 17
- 238000011084 recovery Methods 0.000 description 8
- 235000011121 sodium hydroxide Nutrition 0.000 description 6
- 238000004519 manufacturing process Methods 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- 239000003513 alkali Substances 0.000 description 4
- 238000009835 boiling Methods 0.000 description 3
- 238000005485 electric heating Methods 0.000 description 3
- 238000004134 energy conservation Methods 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 239000012530 fluid Substances 0.000 description 3
- 239000003595 mist Substances 0.000 description 3
- 239000010453 quartz Substances 0.000 description 3
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 3
- 239000000243 solution Substances 0.000 description 3
- 239000012809 cooling fluid Substances 0.000 description 2
- 238000005868 electrolysis reaction Methods 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 239000012528 membrane Substances 0.000 description 2
- 238000012546 transfer Methods 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 1
- 238000010793 Steam injection (oil industry) Methods 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 238000010306 acid treatment Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- FFBHFFJDDLITSX-UHFFFAOYSA-N benzyl N-[2-hydroxy-4-(3-oxomorpholin-4-yl)phenyl]carbamate Chemical compound OC1=C(NC(=O)OCC2=CC=CC=C2)C=CC(=C1)N1CCOCC1=O FFBHFFJDDLITSX-UHFFFAOYSA-N 0.000 description 1
- 239000013064 chemical raw material Substances 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
- 238000007710 freezing Methods 0.000 description 1
- 230000008014 freezing Effects 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 238000006386 neutralization reaction Methods 0.000 description 1
- 238000012946 outsourcing Methods 0.000 description 1
- 238000005192 partition Methods 0.000 description 1
- 238000000746 purification Methods 0.000 description 1
- 239000013589 supplement Substances 0.000 description 1
- 238000007738 vacuum evaporation Methods 0.000 description 1
- 238000004065 wastewater treatment Methods 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B17/00—Sulfur; Compounds thereof
- C01B17/69—Sulfur trioxide; Sulfuric acid
- C01B17/88—Concentration of sulfuric acid
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Vaporization, Distillation, Condensation, Sublimation, And Cold Traps (AREA)
- Drying Of Gases (AREA)
- Heat Treatment Of Water, Waste Water Or Sewage (AREA)
Abstract
The invention discloses a concentration and reuse device for chlorine gas dried waste acid and a control method thereof, wherein the concentration and reuse device comprises an acid-acid heat exchanger, a cold side inlet of the acid-acid heat exchanger is connected with a raw material acid head tank, a cold side outlet is connected with a feed inlet of a first-stage concentration kettle, and a hot side outlet is connected with a hot side inlet of a finished product acid cooler; the primary concentrating kettle liquid phase outlet is connected with a feed inlet of a secondary concentrating kettle, the secondary concentrating kettle liquid phase outlet is connected with a hot side inlet of an acid-acid heat exchanger, the primary concentrating kettle gas phase outlet is directly connected with a defoaming tower, the defoaming tower outlet is connected with a spray condenser, the secondary concentrating kettle gas phase outlet is connected with a washing tower gas phase inlet, and the washing tower gas phase outlet is connected with an inlet of a steam spray pump; a primary heater is arranged in the primary concentration kettle, and a secondary heater is arranged in the secondary concentration kettle. The invention can effectively solve the problem of recycling the chlorine drying waste acid, and has the advantages of stability, reliability, energy saving, environmental protection and low comprehensive cost.
Description
Technical Field
The invention relates to a concentration and recycling device for waste acid and a control method thereof, in particular to a concentration and recycling device for chlorine drying waste acid and a control method thereof.
Background
Caustic soda is an important basic chemical raw material, and the production method of the caustic soda in China at present is mainly an ion membrane electrolysis method. In the production process of the caustic soda by the ion membrane electrolysis method, the generated chlorine is generally dried by a sulfuric acid method, and the process consumes about 12kg of 98 percent sulfuric acid per ton of caustic soda. In 2020, the total production of caustic soda in China is 3673.9 ten thousand tons, and the produced waste acid (75%) is about 58.8 ten thousand tons. At present, chlorine gas drying waste acid treatment modes of chlor-alkali enterprises are mainly outsourcing downstream enterprises or adopting a neutralization method for treatment.
In developed economic bodies in Europe and America, almost all waste acid in the chlor-alkali industry is concentrated and recycled. With the increasing requirements of the nation on energy conservation, environmental protection and resource utilization, the concentration and recycling of waste acid is becoming a consensus of more and more chlor-alkali enterprises, and the recycling is a mainstream development direction.
Prior art 1: sulfuric acid concentration technology (see the application of sulfuric acid concentration technology in the production process of caustic soda at the 1 st stage of volume 57 of chlor-alkali industry). In order to realize the recycling of waste acid, the waste acid is preheated and then sent into a primary concentration rectifying tower to be in countercurrent contact with secondary steam, so that the acid content of the secondary steam is reduced, and low-pressure steam is used as a heat source in primary concentration; and (4) overflowing the concentrated acid into a second-stage concentration, wherein the second-stage concentration adopts an immersed electric heating rod, and secondary steam also enters a first-stage rectifying tower. The two-stage concentration is operated under the same vacuum, gas-phase water vapor is condensed and recovered through chilled water, and non-condensable gas enters a vacuum pump and then is discharged into an absorption device. The advantage of this technique is that equipment configuration is succinct, make full use of secondary steam heat energy, and the shortcoming is that the second grade concentration adopts multiunit quartz electric heating rod on the one hand, and the quartz rod is easy to split, and fail safe nature reduces, and on the other hand the same vacuum is adopted in the two-stage concentration, and the secondary steam temperature is low, needs to use low temperature refrigerated water condensation recovery in a large number. Therefore, this technique has a drawback of high production cost.
Prior art 2: patent document CN108358176A discloses a dilute sulfuric acid vacuum concentration device and method, wherein dilute sulfuric acid is preheated and then concentrated to about 96% by two-stage vacuum concentration, and the generated secondary steam is directly fed into a condenser for condensation and recovery. According to the partial pressure data of sulfuric acid on the sulfuric acid solution, secondary steam generated by secondary concentration in the technology contains more acid, the direct condensation and recovery result in the reduction of the acid recovery rate, the acidity of wastewater is higher, and the difficulty is increased for wastewater treatment.
Disclosure of Invention
The invention aims to solve the technical problem of providing a concentration and recycling device for chlorine gas drying waste acid and a control method thereof, which can effectively solve the problem of cyclic utilization of the chlorine gas drying waste acid and have the advantages of stability, reliability, energy conservation, environmental protection and low comprehensive cost.
The invention provides a concentration and recycling device for chlorine drying waste acid, which solves the technical problems and adopts the technical scheme that the concentration and recycling device comprises an acid-acid heat exchanger, wherein a cold side inlet of the acid-acid heat exchanger is connected with a raw material acid head tank, a cold side outlet of the acid-acid heat exchanger is connected with a feed inlet of a primary concentration kettle, and a hot side outlet of the acid-acid heat exchanger is connected with a hot side inlet of a finished product acid cooler; the primary concentrating kettle liquid phase outlet is connected with a feed inlet of a secondary concentrating kettle, the secondary concentrating kettle liquid phase outlet is connected with a hot side inlet of an acid-acid heat exchanger, the primary concentrating kettle gas phase outlet is directly connected with a defoaming tower, the defoaming tower outlet is connected with a spray condenser, the secondary concentrating kettle gas phase outlet is connected with a washing tower gas phase inlet, and the washing tower gas phase outlet is connected with an inlet of a steam spray pump; a primary heater is arranged in the primary concentration kettle, and a secondary heater is arranged in the secondary concentration kettle.
Furthermore, the primary heater and the secondary heater both adopt tantalum heaters, and a plurality of baffles are arranged in the tantalum heaters.
Further, a concentration condenser is arranged between the gas phase outlet of the gas washing tower) and the inlet of the steam jet pump, and the outlet of the concentration condenser is connected with the waste water intermediate tank.
Further, an outlet of the finished product acid cooler is connected with a finished product acid intermediate tank.
The invention also provides a control method of the concentration and recycling device for chlorine drying waste acid, which aims to solve the technical problems and comprises the following steps: s1), the raw material waste acid outside the boundary area enters a raw material acid elevated tank, part of the waste acid overflows out of the boundary area, and the rest waste acid enters a primary concentration kettle after being subjected to heat exchange with hot finished product sulfuric acid through an acid-acid heat exchanger through flow control; s2), primarily heating and concentrating the dilute sulfuric acid entering a primary concentration kettle by a primary heater under a vacuum condition to reach the concentration of 83-88%; the sulfuric acid after primary concentration automatically flows into a secondary concentration kettle, and is continuously heated and concentrated by a secondary heater under the vacuum condition until the concentration of the sulfuric acid is more than 96 percent; s3), removing foams from the water vapor obtained by primary concentration and evaporation through a foam removing tower, and then directly cooling the water vapor in a jet condenser; the water vapor evaporated by the second-stage concentration is sprayed and washed by a washing tower to remove sulfuric acid in the water vapor, and the spraying liquid part and the raw material waste acid are mixed and returned to the first-stage concentration kettle; s4), water vapor from the washing tower enters a concentration condenser, the condensed water is used for condensation and cooling, non-condensable gas and a small amount of water vapor are pumped out by a steam jet pump, and the water vapor discharged by the steam jet pump is mixed with secondary steam discharged by a primary concentration kettle and enters the jet condenser.
Further, the raw material waste acid is dilute sulfuric acid with the concentration of 70-80%.
Further, in the step S2, the primary heater is heated and concentrated to a sulfuric acid concentration of 83-88% by using low-pressure steam of 0.8-1.0 MPa, and the secondary heater is heated and concentrated to a sulfuric acid concentration of more than 96% by using steam of 1.6-2.0 MPa.
Further, the vacuum in the primary concentration process in the step S2 is generated by a vacuum pump, and the generated absolute pressure is 65-75 mmHg; the vacuum in the secondary concentration process is generated by a steam jet pump and a vacuum pump together, and the absolute pressure is 12-20 mmHg; and (S4) condensing the acidic water vapor subjected to acid removal and temperature reduction in the washing tower by using a concentration condenser, compressing the acidic water vapor by using a vapor injection pump, then condensing the acidic water vapor by using an injection condenser, and allowing the non-condensable gas to enter a working solution buffer tank for gas-liquid separation in a gas-liquid mixture form under the action of a vacuum pump.
Further, the hot sulfuric acid after the secondary heating and concentration in the step S2 exchanges heat with the raw material waste acid, is mixed with the cooled high-concentration sulfuric acid, enters a finished product acid cooler, is cooled to below 45 ℃, and enters a finished product acid intermediate tank.
Further, the finished product acid cooler and the spray condenser adopt circulating water as cooling liquid, and the concentration condenser adopts 0 ℃ chilled water as cooling liquid.
Compared with the prior art, the invention has the following beneficial effects: the concentration and recycling device for chlorine drying waste acid provided by the invention adopts two-stage horizontal vacuum evaporation to evaporate water in dilute sulfuric acid under different vacuum degrees, so that the concentration of liquid-phase sulfuric acid is improved. The method has the following specific advantages: firstly, the boiling point of sulfuric acid is greatly reduced by high vacuum, so that the operation temperature of equipment is reduced, and the range of the type selection and material selection of the equipment is wider; the boiling point is reduced, the heat transfer temperature difference is increased under the condition of the same specification of steam, the heat exchange area is further reduced, and the investment is saved; thirdly, a tantalum bayonet tube type heater is adopted, a plurality of baffles are arranged, material backflow is reduced, the material backflow is in countercurrent contact with steam, and the heat transfer driving force is large; a gas phase outlet of the first-stage concentration kettle is provided with a defoaming tower to reduce material foam entrainment, and gas phase of the second-stage concentration kettle is washed to remove sulfuric acid, so that high recovery rate of the sulfuric acid is ensured; a process of condensation and compression is adopted, secondary steam is condensed and then provides high vacuum for the device through a steam jet pump, and steam consumption is saved; sixthly, the primary concentration vacuum degree is lower, the secondary steam can be directly cooled by circulating water, and high-cost chilled water is not needed as a medium.
Drawings
FIG. 1 is a schematic structural view of a concentration and recycling device for chlorine drying waste acid.
In the figure:
1-raw acid elevated tank, 2-acid heat exchanger, 3-first level concentration kettle, 4-first level heater, 5-defoaming tower, 6-second level concentration kettle, 7-second level heater, 8-washing tower, 9-washing circulating pump, 10-concentration condenser, 11-steam jet pump, 12-jet condenser, 13-vacuum pump, 14-finished acid cooler, 15-finished acid pump, 16-waste water pump, 17-waste water intermediate tank, 18-finished acid intermediate tank.
Detailed Description
The invention is further described below with reference to the figures and examples.
FIG. 1 is a schematic structural view of a concentration and recycling device for chlorine drying waste acid.
Referring to fig. 1, the concentration and recycling device for chlorine drying waste acid provided by the invention comprises an acid-acid heat exchanger 2, wherein a cold side inlet of the acid-acid heat exchanger 2 is connected with a raw material acid head tank 1, a cold side outlet of the acid-acid heat exchanger 2 is connected with a feed inlet of a primary concentration kettle 3, and a hot side outlet of the acid-acid heat exchanger 2 is connected with a hot side inlet of a finished product acid cooler 14; the liquid phase outlet of the first-stage concentration kettle 3 is connected with the feed inlet of the second-stage concentration kettle 6, the liquid phase outlet of the second-stage concentration kettle 6 is connected with the hot side inlet of the acid-acid heat exchanger 2, the gas phase outlet of the first-stage concentration kettle 3 is directly connected with the defoaming tower 5, the outlet of the defoaming tower 5 is connected with the injection condenser 12, the gas phase outlet of the second-stage concentration kettle 6 is connected with the gas phase inlet of the washing tower 8, and the gas phase outlet of the gas washing tower 8 is connected with the inlet of the steam injection pump 11;
a primary heater 4 is arranged in the primary concentration kettle 3, and a secondary heater 7 is arranged in the secondary concentration kettle 6; the spray condenser 12 is used as a first-stage condenser, the concentration condenser 10 is used as a second-stage condenser and is positioned between the gas phase outlet of the scrubber tower 8 and the inlet of the steam spray pump 11, and the outlet of the concentration condenser 10 is connected with the waste water intermediate tank 17.
The process treatment flow of the invention is as follows:
raw material waste acid outside the boundary area enters a raw material acid elevated tank 1, part of the waste acid overflows out of the boundary area, and the rest waste acid enters a primary concentration kettle 3 after exchanging heat with hot finished product sulfuric acid through an acid-acid heat exchanger 2 through flow control.
The dilute sulfuric acid entering the primary concentration kettle 3 is heated and concentrated to a process concentration, such as 83-88%, by a primary heater 4 under a vacuum condition; the concentrated sulfuric acid automatically flows into a second-stage concentration kettle 6, and is heated and concentrated to the sulfuric acid concentration of more than 96% by a second-stage heater 7 under the vacuum condition. The 96% hot acid exchanges heat with the raw waste acid, then is mixed with the cooled high-concentration sulfuric acid (more than 96%), enters a finished product acid cooler 14, is cooled to below 45 ℃, and enters a finished product acid intermediate tank. Part of the cooled high-concentration sulfuric acid is mixed with 96% hot acid after heat exchange by controlling the inlet temperature of a finished product acid cooler 14, and the rest is sent out of a battery limit by controlling the liquid level of a finished product acid intermediate tank 18 by a finished product acid pump 15.
The water vapor evaporated by the first-stage concentration is defoamed by a defoaming tower 5 and then is directly sent to a jet condenser 12 for condensation and cooling; the water vapor evaporated from the second-stage concentration is sprayed and washed by circulating washing liquid provided by a washing circulating pump 9 through a washing tower 8, and acid mist carried in the vapor is collected and returned to the first-stage concentration kettle 3. The acidic water vapor after being deacidified and cooled by the washing tower 8 is condensed by a concentration condenser 10, and then is condensed by a vapor injection pump 11 after being compressed by vapor and then is sent to an injection condenser 12. The condensed water enters a waste water intermediate tank 17; the non-condensable gas enters the working solution buffer tank in a gas-liquid mixture form for gas-liquid separation under the action of a vacuum pump 13, and the gas is sent to the outside of the battery compartment for treatment; the working fluid is cooled and recycled by a working fluid cooler (not shown). The vacuum of the primary concentration process is generated by a vacuum pump 13, and the vacuum of the secondary concentration process is generated by the steam jet pump 11 and the vacuum pump 13 together. The acid wastewater is partially used as make-up water for the vacuum pump 13, and the rest is sent out of the battery limit area for treatment by the wastewater pump 16 through controlling the liquid level of the wastewater intermediate tank 17.
The finished product acid cooler 14, the spray condenser 12 and the working fluid cooler adopt circulating water as cooling fluid, and the concentration condenser 10 adopts 0 ℃ chilled water as cooling fluid.
The primary heater 4 and the secondary heater 7 both adopt tantalum heaters, wherein the primary heater 4 is heated by 0.8-1.0 MPa steam; the secondary heater 7 is heated by 1.6-2.0 MPa steam, preferably 1.6-1.8 MPa steam, and condensed water is sent out of a boundary area for comprehensive utilization.
(5) Example of the implementation
Pumping 70-80% dilute sulfuric acid into a raw acid elevated tank 1 by a raw acid pump outside a boundary area, exchanging heat with high-temperature finished acid discharged from a secondary concentration kettle 6 by utilizing the potential difference to automatically flow into an acid heat exchanger 2, and automatically flowing the preheated raw acid into a primary concentration kettle 3; under the condition of 65-75 mmHg of absolute pressure, raw material acid sequentially flows through a plurality of concentration chambers in a concentration kettle, the acid liquor backflow is prevented by the concentration chambers due to the existence of partition plates, the acid concentration in the concentration chambers is sequentially improved, and the raw material acid is concentrated to 83-88% under the heating of low-pressure steam of 0.8-1.0 MPa (G);
acid from the first-stage concentration kettle 3 automatically flows into a second-stage concentration kettle 6, the structure of the second-stage concentration kettle 6 is similar to that of the first-stage concentration kettle 3, the concentration kettle is divided into a plurality of concentration chambers, the acid concentration is sequentially improved, finally, the sulfuric acid reaches more than 96% under the condition of absolute pressure of 12-20 mmHg, and the sulfuric acid is discharged out of the second-stage concentration kettle 6;
removing mist from the secondary steam generated by the primary concentration kettle 3 through a mist removing tower 5, mixing the secondary steam with the gas from a steam jet pump 11, feeding the mixture into a jet condenser 12, condensing the steam, feeding the condensed steam into a waste water intermediate tank 17, pumping out non-condensable gas, a small amount of steam and the like through a vacuum pump 13, and finally discharging the condensed steam to a tail gas purification tower (not shown in the figure) for treatment; acid-containing steam generated by the second-stage concentration kettle 6 is sprayed and washed through the washing tower 8 to remove sulfuric acid in the steam, a part of spray liquid is mixed with raw material acid to enter the first-stage concentration kettle 3, acid wastewater is used as spray circulating liquid for water supplement, the steam coming out of the washing tower 8 enters the concentration condenser 10, freezing water is used for condensation and cooling, non-condensable gas, a small amount of steam and the like are pumped out by the steam jet pump 11, and the steam discharged by the steam jet pump 11 is mixed with secondary steam discharged by the first-stage concentration kettle 3 to enter the jet condenser 12.
The waste acid is required to be concentrated to more than 93% for recycling when being dried by the chlorine, and according to the data of the water feeding and the sulfuric acid partial pressure of the sulfuric acid solution, the secondary steam contains more sulfuric acid, and if the secondary steam enters a condenser, the secondary steam has stronger corrosivity, the waste water has high acid content, and the waste of the sulfuric acid is caused. Therefore, the invention removes the sulfuric acid by adopting a spray washing mode to the secondary steam, reduces the acid content of the wastewater and improves the recovery rate of the sulfuric acid. The two-stage concentration has different vacuum degrees, proper operation pressure is selected according to the relation between the boiling point of the material and the pressure, and the primary concentrated secondary steam can be condensed by circulating water, so that the defect that high-cost chilled water must be adopted under high vacuum is overcome. The invention can effectively solve the problem of recycling of chlorine drying waste acid, and provides a stable and reliable solution with energy conservation, environmental protection and low comprehensive cost. The method has the following specific advantages:
(1) the entrainment phenomenon of secondary steam is reduced by arranging the defoaming tower 5, the secondary steam contains higher sulfuric acid steam due to high acid concentration in the secondary concentration, the washing tower 8 for spraying can effectively wash away the sulfuric acid in the secondary steam, the acid content of the wastewater is reduced, the use safety of subsequent equipment is protected, the sulfuric acid recovery rate of the device is further ensured, and the device is more environment-friendly;
(2) the device adopts middle and low pressure steam as a heat source, and the heater adopts a tantalum bayonet tube type with high reliability, so that the device has stable operation and high reliability compared with a quartz electric heating tube which is easy to crack.
(3) The process device only consumes steam and electricity, and is provided with the high-temperature acid heat exchanger, so that the heat energy of high-quality products is fully utilized; the circulating water replenishing of the vacuum system adopts process condensate water, so that the wastewater discharge is reduced; the vacuum system adopts a standard device, namely a water ring vacuum pump, so that the vacuum degree is stable, and the maintenance and the replacement are convenient.
(4) The concentration of sulfuric acid in the product acid is more than or equal to 96 percent, and the content of chloride ions is less than or equal to 10ppm, so that the recycling requirement of a chlorine drying procedure is completely met; the recovery rate of waste acid is high, only a small amount of fresh 98 percent sulfuric acid is needed to be supplemented every year to meet the requirement of recycling, and a large amount of purchasing cost of sulfuric acid is saved.
(5) The process of the invention has obvious advantages in energy saving and consumption reduction, and according to public data, the utility consumption ratio of several processes is shown in the following table. Process 1 is prior art 1 of the background section and process 2 is prior art 2 of the background section.
Although the present invention has been described with respect to the preferred embodiments, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (10)
1. A concentration and recycling device for chlorine drying waste acid comprises an acid-acid heat exchanger (2), and is characterized in that a cold side inlet of the acid-acid heat exchanger (2) is connected with a raw material acid elevated tank (1), a cold side outlet of the acid-acid heat exchanger (2) is connected with a feed inlet of a first-stage concentration kettle (3), and a hot side outlet of the acid-acid heat exchanger (2) is connected with a hot side inlet of a finished product acid cooler (14); the liquid phase outlet of the first-stage concentration kettle (3) is connected with the feed inlet of the second-stage concentration kettle (6), the liquid phase outlet of the second-stage concentration kettle (6) is connected with the hot side inlet of the acid-acid heat exchanger (2), the gas phase outlet of the first-stage concentration kettle (3) is directly connected with the defoaming tower (5), the outlet of the defoaming tower (5) is connected with the jet condenser (12), the gas phase outlet of the second-stage concentration kettle (6) is connected with the gas phase inlet of the washing tower (8), and the gas phase outlet of the washing tower (8) is connected with the inlet of the steam jet pump (11);
a primary heater (4) is arranged in the primary concentration kettle (3), and a secondary heater (7) is arranged in the secondary concentration kettle (6).
2. The concentration and recycling device of chlorine gas drying waste acid as claimed in claim 1, wherein the primary heater (4) and the secondary heater (7) both adopt tantalum heaters, and a plurality of baffles are arranged in the tantalum heaters.
3. The apparatus for concentrating and recycling chlorine gas dried waste acid as claimed in claim 1, wherein a concentration condenser (10) is arranged between the gas phase outlet of the scrubber tower (8) and the inlet of the steam jet pump (11), and the outlet of the concentration condenser (10) is connected with the waste water intermediate tank (17).
4. The apparatus for concentrating and recycling chlorine gas dried waste acid as claimed in claim 1, wherein the outlet of the finished acid cooler (14) is connected to the finished acid intermediate tank (18).
5. A control method of a concentration and recycling device of chlorine gas dried waste acid as claimed in any one of claims 1 to 4, characterized by comprising the following steps:
s1), raw material waste acid outside a boundary area enters a raw material acid elevated tank (1), part of waste acid overflows out of the boundary area, and the rest waste acid enters a primary concentration kettle (3) after being subjected to heat exchange with hot finished product sulfuric acid through an acid-acid heat exchanger (2) through flow control;
s2), primarily heating and concentrating the dilute sulfuric acid entering the primary concentration kettle (3) by a primary heater (4) under a vacuum condition to reach the concentration of 83-88%; the primarily concentrated sulfuric acid automatically flows into a secondary concentration kettle (6), and is continuously heated and concentrated by a secondary heater (7) under the vacuum condition until the concentration of the sulfuric acid is more than 96 percent;
s3), removing foams from the water vapor obtained by primary concentration and evaporation through a foam removing tower (5), and then directly sending the water vapor to a jet condenser (12) for condensation and cooling; the water vapor evaporated by the second-stage concentration is sprayed and washed by a washing tower (8) to remove sulfuric acid in the water vapor, and the spraying liquid part is mixed with raw waste acid and returns to the first-stage concentration kettle (3);
s4), introducing the steam from the washing tower (8) into a concentration condenser (10), condensing and cooling by using chilled water, pumping out non-condensable gas and a small amount of steam by using a steam jet pump (11), mixing the steam discharged by the steam jet pump (11) with secondary steam discharged by a primary concentration kettle (3), and introducing the mixed steam into a jet condenser (12).
6. The control method of the concentration and recycling device for chlorine drying waste acid as claimed in claim 5, wherein the raw waste acid is dilute sulfuric acid with a concentration of 70-80%.
7. The control method of the concentration and recycling device for chlorine drying waste acid as claimed in claim 5, wherein in the step S2, the primary heater (4) is heated and concentrated to a sulfuric acid concentration of 83-88% by using low-pressure steam of 0.8-1.0 MPa, and the secondary heater (7) is heated and concentrated to a sulfuric acid concentration of more than 96% by using steam of 1.6-2.0 MPa.
8. The control method of the concentration and recycling device for chlorine drying waste acid as claimed in claim 5, wherein the vacuum of the primary concentration process in the step S2 is generated by a vacuum pump (13), and the absolute pressure generated is 65-75 mmHg; the vacuum of the secondary concentration process is generated by a steam jet pump (11) and a vacuum pump (13) together, and the absolute pressure is 12-20 mmHg; and (2) condensing the acidic water vapor subjected to acid removal and temperature reduction in the washing tower (8) in the step (S4) by a concentration condenser (10), condensing the acidic water vapor by a vapor injection pump (11) through a vapor compression injection condenser (12), and allowing the non-condensable gas to enter a working solution buffer tank for gas-liquid separation in a gas-liquid mixture form under the action of a vacuum pump (13).
9. The method for controlling the apparatus for concentrating and recycling chlorine drying waste acid as claimed in claim 5, wherein the hot sulfuric acid after the secondary heating and concentration in step S2 exchanges heat with the raw waste acid, then is mixed with the cooled high-concentration sulfuric acid, and then enters the finished acid cooler (14), and is cooled to below 45 ℃ to enter the finished acid intermediate tank (18).
10. The control method of the concentration and recycling device for chlorine drying waste acid as claimed in claim 5, characterized in that the finished product acid cooler (14) and the spray condenser (12) use circulating water as cooling liquid, and the concentration condenser (10) uses 0 ℃ chilled water as cooling liquid.
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