CN220572668U - Caustic solution evaporation apparatus - Google Patents
Caustic solution evaporation apparatus Download PDFInfo
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- CN220572668U CN220572668U CN202320823859.7U CN202320823859U CN220572668U CN 220572668 U CN220572668 U CN 220572668U CN 202320823859 U CN202320823859 U CN 202320823859U CN 220572668 U CN220572668 U CN 220572668U
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- Prior art keywords
- stage evaporator
- evaporator
- caustic solution
- stage
- heated
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- 239000003518 caustics Substances 0.000 title claims abstract description 61
- 238000001704 evaporation Methods 0.000 title claims abstract description 11
- 230000008020 evaporation Effects 0.000 title claims abstract description 11
- 238000007599 discharging Methods 0.000 claims abstract description 4
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 17
- 238000010438 heat treatment Methods 0.000 claims description 12
- 239000011552 falling film Substances 0.000 claims description 8
- 235000011121 sodium hydroxide Nutrition 0.000 claims description 6
- 239000000498 cooling water Substances 0.000 claims description 5
- 239000012141 concentrate Substances 0.000 claims description 3
- 238000009834 vaporization Methods 0.000 abstract description 3
- 230000008016 vaporization Effects 0.000 abstract description 3
- 239000000243 solution Substances 0.000 description 43
- 239000000047 product Substances 0.000 description 13
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 5
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 4
- OAKJQQAXSVQMHS-UHFFFAOYSA-N Hydrazine Chemical compound NN OAKJQQAXSVQMHS-UHFFFAOYSA-N 0.000 description 2
- 238000001816 cooling Methods 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- 239000012528 membrane Substances 0.000 description 2
- 229910052759 nickel Inorganic materials 0.000 description 2
- 235000011118 potassium hydroxide Nutrition 0.000 description 2
- LSNNMFCWUKXFEE-UHFFFAOYSA-M Bisulfite Chemical compound OS([O-])=O LSNNMFCWUKXFEE-UHFFFAOYSA-M 0.000 description 1
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 238000005868 electrolysis reaction Methods 0.000 description 1
- 239000003112 inhibitor Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 239000008188 pellet Substances 0.000 description 1
- 229910052700 potassium Inorganic materials 0.000 description 1
- 239000011591 potassium Substances 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 239000013589 supplement Substances 0.000 description 1
- 239000002351 wastewater Substances 0.000 description 1
Landscapes
- Vaporization, Distillation, Condensation, Sublimation, And Cold Traps (AREA)
Abstract
The present utility model relates to a caustic solution evaporation apparatus comprising: a caustic feed line, a first stage evaporator, a second stage evaporator, a third stage evaporator, and a fourth stage evaporator, wherein the first stage evaporator is heated by steam generated by the second stage evaporator, the second stage evaporator is heated by steam generated by the third stage evaporator, the third stage evaporator is heated by steam generated by the fourth stage evaporator, and the fourth stage evaporator is heated by hot oil, which is circulated by a pump through an electric heater in a closed loop. The caustic solution vaporization apparatus also includes a vapor condensing tank that collects vapor condensate from the first stage evaporator, the second stage evaporator, and the third stage evaporator; a water-cooled surface condenser condensing the vapor generated in the first stage evaporator; a pump for discharging the vapor condensing tank; and a product caustic solution discharge line.
Description
Technical Field
The present utility model relates to a caustic soda or potassium evaporation (hereinafter referred to as caustic solution evaporation) apparatus comprising: a caustic solution feed line; a first stage evaporator that receives a low strength caustic solution and operates at a reduced pressure of less than or equal to 0.15 bar; a second stage evaporator that receives the enriched caustic solution from the first evaporator and operates at a reduced pressure of less than or equal to 0.5 bar; a third stage evaporator receiving the further enriched caustic solution from the second stage evaporator and operating at a pressure greater than or equal to 1.1 bar; and a fourth stage evaporator receiving the further enriched caustic solution from the third stage evaporator and operating at a pressure greater than 4.0 bar, wherein the first stage evaporator is heated by steam generated by the second stage evaporator, the second stage evaporator is heated by steam generated by the third stage evaporator, the third stage evaporator is heated by steam generated by the fourth stage evaporator, and the fourth stage evaporator is heated by hot oil, the hot oil being circulated by a pump through an electric heater in the circuit; a vapor condensing tank that collects vapor condensate from the first stage evaporator, the second and the third stage evaporators; a water-cooled surface condenser condensing the steam generated in the first stage evaporator; a pump for discharging the steam condensing tank; and a product caustic solution discharge line.
Background
Caustic soda solution (NaOH solution) is mainly obtained by electrolysis in a membrane method, and is a 30% to 33% aqueous solution. It is known to concentrate such a solution in an evaporation apparatus to a NaOH concentration of 50% by weight or more. It is common practice to further concentrate this solution in a concentration apparatus with a falling film concentrator into a practically anhydrous melt for further processing into flakes, pellets or spheres. The same applies to caustic potash solutions (KOH solutions).
Known evaporation equipment for caustic solutions typically operates in a "single pass" mode with three falling film evaporators and an integrated vapor separator. The first two of the three falling film evaporators are usually operated under vacuum and the third at elevated pressure. The low strength caustic solution is fed to a first evaporator that is heated by steam generated by a second evaporator. The enriched caustic solution from the first evaporator is fed to a second evaporator for further concentration, the second evaporator being heated by steam generated by a third evaporator. The product caustic solution from the second evaporator is fed to a third evaporator, which is heated by pressurized steam. The product caustic solution, steam, and generated steam are passed through a heat exchanger to retain heat within the apparatus.
The pressurized steam used in the third evaporator requires that the shell side is safe at pressures up to at least 16 bar. In addition, steam at temperatures exceeding 200 ℃ must be provided. This requires a steam generator if no steam source is available in the device. High pressure steam requires expensive safety and sealing devices. In particular, where no inherent source of steam is available in the apparatus, a steam independent heating system may be an option. However, this would require new designs for many of the components and lines within the device.
Disclosure of Invention
It is an object of the present utility model to provide a caustic concentrating apparatus that can be operated independently of steam, thereby avoiding the provision of a high pressure resistant evaporator. Furthermore, such an apparatus should efficiently use/recover energy from the heating system and the production line. This object is achieved by a caustic evaporation apparatus according to the utility model.
The caustic evaporation apparatus of the present utility model comprises four evaporators arranged in series. Preferably, at least one of the evaporators is a falling film evaporator, in particular, all four evaporators are falling film evaporators, which have been shown to be most effective for heating caustic solution.
A low strength caustic solution (typically a membrane cell solution having a concentration of 30 to 33 wt%) is added to the first stage evaporator. The first evaporator is operated on the tube side at a reduced pressure of less than or equal to 0.15 bar, preferably at about 85 to 100 mbar. The first stage evaporator is heated by the vapor exiting from the second stage evaporator. The condensed heated steam leaving the first stage evaporator is collected in a steam condensing tank. The steam produced from the caustic solution in the first stage evaporator is cooled in a condenser and may be vented with cooling water or transferred to a steam condensate tank.
The 35 to 36% of the enriched caustic solution from the first stage evaporator is passed to the second stage evaporator where it is heated by the steam produced in the third stage evaporator. The second stage evaporator is operated at a reduced pressure of less than or equal to 0.5 bar, preferably about 320 to 400 mbar. The condensed heated steam leaving the second stage evaporator is collected in a steam condensing tank. The steam generated in the second stage evaporator is used to heat the first stage evaporator.
38 to 40% of the further enriched caustic solution from the second stage evaporator is passed to the third stage evaporator where it is heated by the steam produced in the fourth stage evaporator. The third stage evaporator is operated at an elevated pressure of greater than or equal to 1.1 bar, preferably 1.1 to 1.2 bar. The condensed heated steam leaving the third stage evaporator is collected in a steam condensing tank. The steam generated in the third stage evaporator is used to heat the second stage evaporator.
The 43 to 45% further concentrated caustic solution from the third stage evaporator is passed to the fourth stage evaporator where it is heated by hot oil to a temperature of at least 230 c, preferably about 210 to 240 c. The fourth stage evaporator is operated at a pressure of 4.8 to 5.3 bar, preferably about 5.0 bar. The hot oil is heated by an electric heater and is run in a circuit by a pump. The hot oil leaving the fourth stage evaporator is still hot enough (175 to 190 ℃) for use in the heat exchanger to partially heat the product caustic solution leaving the third, second and first stage evaporators prior to being recycled to the electric heater. The product caustic solution exiting the fourth stage evaporator has a caustic concentration of 50 wt% or greater and exits the apparatus after transferring its heat to the product exiting the third, second and first evaporators. The steam generated in the fourth stage evaporator is used to heat the third stage evaporator.
The condensed heating steam leaving the third, second and first stage evaporators is collected in a common steam condensing tank. If the exiting heating vapors are still hot enough, they can be used in part to supplement the heating vapors of the low-stage evaporator.
As described above, if the condensate is not discharged together with the cooling water, the steam condensing tank may also receive the condensed steam generated in the first-stage evaporator after proper cooling.
The hot oil heating system for the fourth stage evaporator was operated at ambient pressure. It is therefore not necessary to provide a pressure-safe shell side for heating the product in the fourth-stage evaporator.
To reduce the nickel corrosion of the equipment, and thus the increase in nickel in 50% lye, a corrosion inhibitor solution, such as borohydride, bisulfite, hydrazine, is metered into the feed caustic.
Drawings
The utility model is further illustrated by the attached flow chart.
FIG. 1 is a flow chart of the operation of the caustic solution vaporization apparatus of the present utility model.
Detailed Description
In the preferred embodiment of FIG. 1, the caustic solution vaporization apparatus of the present utility model includes four falling film evaporators EV-1101, 1201, 1301 and 1401. The evaporators are arranged in a line, the first stage evaporator EV-1101 is heated by steam generated in the second stage evaporator EV-1201 by line 12, the second stage evaporator EV-1201 is heated by steam generated in the third stage evaporator EV-1301 by line 19, and the third stage evaporator EV-1301 is heated by steam generated in the fourth stage evaporator EV-1401 by line 26. The fourth stage evaporator EV-1401 is heated via line 31 and exits the fourth stage evaporator EV-1401 via line 32. The spent condensed heating steam exits the evaporator EV-1301 via line 36, exits the evaporator EV-1201 via line 41, and exits the evaporator EV-1101 via line 45. All of the spent condensed heating steam is eventually collected in tank T-7101 and then exits the apparatus via pump P-7101 and line 47.
Evaporators EV-1101 and 1201 were operated at reduced pressures of 100 mbar and 400 mbar, respectively, while evaporators EV-1301 and 1401 were operated at elevated pressures of 1.2 bar and 5.0 bar, respectively. While all evaporators are falling film evaporators.
The feed is passed through line 1 to first stage evaporator EV-1101 where it is concentrated to a 33% caustic content. The concentrated caustic solution from EV-1101 continues to pass via line 2 and pump P-1101 to evaporator EV-1201, via line 10, to the second stage evaporator. On its way to the second stage evaporator, the caustic exiting the first stage evaporator passes through heat exchanger HE-1511 via line 4 and/or heat exchanger HE-1521 via line 5 and/or heat exchanger HE-1581 via line 6 before entering line 10 via lines 7, 8 or 9, respectively. Heat exchanger HE-1511 is fed by product exiting first stage evaporator EV-1401, heat exchanger HE-1581 is fed by spent steam exiting third stage evaporator EV-1301 via line 36, tank T-1301, line 37 and pump P-1302, and heat exchanger HE-1521 is fed by hot oil exiting the shell side of evaporator EV-1401.
The concentrated caustic solution leaving the second stage evaporator EV-1201 has a 36% concentration and is passed to the third stage evaporator EV-1301 via line 11 and pump P-1201 (to the third stage evaporator EV-1301). On its way to the third stage evaporator, the caustic solution is fed via line 13 to heat exchanger HE-1541 and/or via line 14 to heat exchanger HE-1551 where it absorbs heat provided by all of the product exiting the fourth stage evaporator or the hot oil from the fourth stage evaporator, respectively. The concentrated caustic solution is then passed via lines 15 and 16 and then via line 17 to a third stage evaporator EV-1301.
In evaporator EV-1301, the caustic content of the caustic solution was concentrated from 36% to 45%. The concentrated caustic solution is fed to the fourth stage evaporator EV-1401 via line 18 and pump P-1301. To absorb heat, the caustic solution is fed through lines 20 and 21 to heat exchangers HE-1561 and HE-1571, respectively, and then through lines 22 and 23 to line 24 and fourth stage evaporator EV-1401, respectively. Heat exchanger HE-1561 is heated by the product caustic solution exiting the fourth stage evaporator via line 25, while heat exchanger HE-1571 is heated by the hot oil exiting the first stage evaporator via line 32. The product caustic solution leaving the fourth evaporator had a concentration of 50% caustic.
In this preferred embodiment of the apparatus according to the utility model, the heat from the used steam as well as the hot oil and the product leaving the fourth stage evaporator is largely recovered in the heat exchanger. The vapor leaving the first stage evaporator via line 3 is cooled in cooler C-7101 by cooling via lines 48 and 49 and the product caustic leaves the apparatus via line 29/30 to heat exchanger HE-1531.
Alternatively, a hybrid condenser may also be used, in which steam is condensed directly into the cooling water and directed as a mixed water stream to a plant area (tank). Inert material is drawn off by a closed or open loop water ring vacuum pump P-7102 or a steam ejector vacuum system. Closed loop water loop vacuum systems are typically selected to minimize the amount of wastewater. The circulating water will be cooled in the plate heat exchanger by cold water.
The hot oil used to heat the evaporator EV-1401 operates in a closed loop beginning at heater HE-6101, entering the fourth stage evaporator via line 31 and exiting via line 32. The hot oil is passed through heat exchanger HE-5071 and line 33 to heat exchanger HE-1551 to transfer heat to the caustic solution exiting the third and second stage evaporators, respectively, before being recycled to heater HE-6101. Thereafter, the oil is fed through line 34 to heat exchanger HE-1521 to heat the caustic solution exiting the first stage evaporator EV-1101 and then recycled to heater HE-6101 via pump P-6301. Tank T-6301 and pump P-6302 feed hot oil to the oil heating circuit when necessary, while tank T-6302 serves as an oil overflow tank.
In heater H-6101, the hot oil is heated to a temperature of 210 to 235 ℃ during circulation. After passing through the fourth stage evaporator and heat exchanger, the temperature of the hot oil has been reduced to 175 to 190 ℃.
The product caustic solution exiting fourth evaporator EV-1401 via line 25 is then passed through heat exchanger HE-1561, pump P-1401, line 27, heat exchanger HE-1541, line 28, heat exchanger HE-1511 and line 29 to heat exchanger HE-1531 connected to cooling water lines 50 and 51 before exiting the plant via line 30.
Claims (9)
1. A caustic solution evaporation apparatus, comprising
-a caustic solution feed line,
a first stage evaporator (EV-1101) receiving a low strength caustic solution and operating at a reduced pressure of less than or equal to 0.15 bar,
a second stage evaporator (EV-1201) receiving the enriched caustic solution from the first stage evaporator (EV-1101) and operating at a reduced pressure of less than or equal to 0.5 bar,
a third stage evaporator (EV-1301) receiving the further enriched caustic solution from the second stage evaporator (EV-1201) and operating at a pressure of greater than or equal to 1.1 bar,
-a fourth stage evaporator (EV-1401) receiving the further enriched caustic solution from the third stage evaporator (EV-1301) and operating at a pressure of greater than 4.0 bar,
the first stage evaporator (EV-1101) is heated by steam generated by the second stage evaporator (EV-1201), the second stage evaporator (EV-1201) is heated by steam generated by the third stage evaporator (EV-1301), the third stage evaporator (EV-1301) is heated by steam generated by the fourth stage evaporator (EV-1401), and the fourth stage evaporator (EV-1401) is heated by hot oil which is circulated by a first pump (P-6301) through an electric heater (HE-6101) in a closed loop,
-a steam condensing tank (T-7101) collecting steam condensate from said first stage evaporator (EV-1101), said second stage evaporator (EV-1201) and said third stage evaporator (EV-1301),
a water-cooled surface condenser (C-7101) which condenses the vapor generated in the first-stage evaporator (EV-1101),
-a second pump (P7101) for discharging said vapor condensing tank (T-7101), and
-a product caustic solution discharge line.
2. The apparatus of claim 1, characterized in that the temperature of the oil leaving the electric heater (HE-6101) is 210 to 235 ℃.
3. The apparatus according to claim 1 or 2, characterized in that at least one evaporator (EV-1101, 1201, 1301, 1401) is a falling film evaporator.
4. The apparatus of claim 3, wherein the caustic solution exiting the fourth stage evaporator (EV-1401) passes through at least one heat exchanger (HE-1571, 1551, 1521) to preheat the intermediate caustic solution exiting the first stage evaporator (EV-1101), second stage evaporator (EV-1201) and/or third stage evaporator (EV-1301).
5. The apparatus of claim 1 or 2, wherein the caustic solution exiting the fourth stage evaporator (EV-1401) is continuously passed through heat exchangers (HE-1571, 1551, 1521) for heating the products exiting the third, second and first stage evaporators.
6. The plant according to claim 1, characterized in that the steam condensate from the first-stage evaporator (EV-1101) is discharged together with cooling water.
7. The apparatus according to claim 1, characterized in that the surface condenser (C-7101) is connected to the steam condensing tank (T-7101) for discharging condensate from the surface condenser (C-7101).
8. The apparatus of claim 1, wherein the hot oil of the fourth stage evaporator (EV-1401) is heated at ambient pressure.
9. The apparatus of claim 1, wherein the caustic solution evaporation apparatus is operable to concentrate caustic soda solution from 32% or less to 50% or more.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202320823859.7U CN220572668U (en) | 2023-04-14 | 2023-04-14 | Caustic solution evaporation apparatus |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202320823859.7U CN220572668U (en) | 2023-04-14 | 2023-04-14 | Caustic solution evaporation apparatus |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN220572668U true CN220572668U (en) | 2024-03-12 |
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ID=90117395
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202320823859.7U Active CN220572668U (en) | 2023-04-14 | 2023-04-14 | Caustic solution evaporation apparatus |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN220572668U (en) |
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2023
- 2023-04-14 CN CN202320823859.7U patent/CN220572668U/en active Active
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