CN115899656A - Forced circulation evaporation device for concentrated sulfuric acid low-temperature-level waste heat recovery process - Google Patents
Forced circulation evaporation device for concentrated sulfuric acid low-temperature-level waste heat recovery process Download PDFInfo
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Abstract
The invention provides a forced circulation evaporation device for a concentrated sulfuric acid low-temperature level waste heat recovery process, and belongs to the technical field of concentrated sulfuric acid waste heat equipment utilization. The invention comprises a constant potential rectifier, a forced circulation heater and a flash tank which are communicated; the flash tank is communicated with the forced circulation heater; a circulating pump is communicated between an inlet of the forced circulation heater and an outlet of the flash tank; an anode protection device is arranged in a shell of the forced circulation heater, and a constant potential rectifier is used for applying current to the anode protection device to form a stable passive film on the surface of equipment contacted with sulfuric acid; the concentration of the sulfuric acid can fluctuate in the range of more than or equal to 98.5 percent, and the method is used under the working condition that the temperature of the sulfuric acid is 150-230 ℃. The invention can prevent the corrosion caused by the fluctuation of the concentration of the sulfuric acid, ensures the recovery and utilization of waste heat by arranging the flash tank outside the forced circulation heater, and ensures the temperature of the forced circulation heater to be stable by arranging the pressurizing valve and the pressure regulating valve on the pipeline, thereby avoiding the corrosion caused by the fluctuation of the concentration of the sulfuric acid due to the change of the temperature.
Description
Technical Field
The invention relates to the technical field of concentrated sulfuric acid waste heat equipment utilization, in particular to a forced circulation evaporation device used in a concentrated sulfuric acid low-temperature level waste heat recovery process.
Background
The steam generator is the core equipment of sulphuric acid low temperature position waste heat recovery technology, and prior art equipment form is kettle type steam generator, and this equipment area is big, improves cauldron inner upper evaporation space through increase equipment diameter and the tapering of enlarging, relies on tube bank length to realize heat transfer area, and the tube bank can reach 13m to the longest, and equipment length can reach 17m. The equipment is provided with a steam-water separation device, a safety valve and a pressure gauge, and a continuous sewage draining device and a liquid level meter are arranged near the liquid level. In the operation and use, the service life of the concentrated sulfuric acid kettle type steam generator is about 3-5 years, some service lives are about 1 year, and large-area leakage can occur when the operation of other equipment is less than 1 month.
In flue gas and acid preparation by smelting, the concentration of sulfuric acid changes along with the concentration of sulfur trioxide, so that the corrosion aggravated due to the fluctuation of the concentration of sulfuric acid is easy to occur, the requirement on the concentration of sulfuric acid in the process is more than 99.3% for safe production in industrial application, the corrosion to materials due to the fluctuation of the concentration of acid at high temperature is mainly reduced, and the concentration of acid is prevented from being lower than 99.0%. However, in actual operation, the fluctuation of acid concentration is inevitable, once the concentration is lower than the critical value of 99%, the process can only be adjusted as soon as possible, the corrosion area is doubled excessively by depending on the wall thickness of the equipment, if the corrosion rate is found to be untimely, the corrosion rate is fast, the corrosion rate is about 3.7 times of the corrosion rate under the normal process, the destructiveness is strong, large-area leakage can occur when some equipment runs for less than one month, and the design life is difficult to achieve.
The U-shaped tube bundle also has defects, so that plastic deformation exists during cold bending, large residual tensile stress exists at the outer edge of the bent tube, and stress corrosion cracking occurs at the bent tube and the horizontal section of the bent tube under the combined action of a tensile stress area and a sulfuric acid medium after the tensile stress is generated by temperature difference.
Secondly, in the prior art, the steam generator adopts a kettle type structure, heating and vaporization are completely finished in the equipment, a shell side liquid phase is heated by concentrated sulfuric acid in the tube bundle, a large amount of vaporization is carried out at a gas-liquid interface, and then steam is generated. When the equipment is operated, salt brought by the steam is much less than that brought by the water supply, so that the salt content of the water in the kettle is greater than that of the water supply; in addition, as the steam leaves through the water surface, the salt concentration near the water surface is the highest, and the salt concentration is found according to the damaged position of the field equipment: the heat exchange tube bundle is most prone to corrosion and damage, and the reason is that the upper heat exchange tubes are continuously arranged at the discharge positions of high-temperature concentrated acid and high-concentration brine, and stress corrosion cracking is easy to occur.
Meanwhile, the horizontal steam generator in the prior art is frequently damaged at the welding joint of the heat exchange tube bundle and the tube plate. The sulfuric acid has high temperature and large flow, and high-temperature fluid directly erodes the welding seam between the heat exchange tube and the tube plate to cause erosion corrosion and crack and leakage of the welding part, thereby reducing the service life of the equipment and causing the cracking phenomenon when the equipment with serious corrosion is used for less than one month. There has been no improvement over the above in the prior sulfuric acid heat recovery steam generator patents.
Moreover, steam generator's temperature fluctuation also can cause sulphuric acid equipment's corruption, consequently, it is especially important in order to improve its corrosion resistance to steam generator's temperature control, and do not have at present to carry out recycle to the waste heat of concentrated sulfuric acid, improve heat exchange efficiency through forced circulation's mode, reduce the indirect heating equipment volume, utilize relief pressure valve, pressure regulating valve's flash distillation operation, make forced circulation heater's temperature remain stable, so that the fluctuation that reduces the temperature leads to the fluctuation of sulphuric acid concentration, the aggravation of the corrosion phenomenon that leads to.
There has been no improvement over the above in the prior sulfuric acid heat recovery steam generator patents.
Whatever the corrosion reason, the damage degree of the steam heat exchanger is reduced to the minimum by timely finding. For the particularity of sulfuric acid media, patent numbers 201220108564.3, 201820281825.9 and 201921550558.1 regularly inspect leakage conditions through a liquid outlet of an isolation cavity, but a 'blind spot' of maintenance and management is easy to occur. Therefore, higher requirements are required for the timeliness of finding the acid leakage of the waste heat recovery equipment.
Disclosure of Invention
In view of the above, in order to solve the corrosion situation of the sulfuric acid equipment caused by the fluctuation of the sulfuric acid concentration, the invention provides a forced circulation evaporation device used in the concentrated sulfuric acid low-temperature waste heat recovery process, which applies current to an anode protection device in a shell of a forced circulation heater through a potentiostat to form a stable passivation film on the surface of the equipment contacted with sulfuric acid so as to prevent corrosion caused by the fluctuation of the sulfuric acid concentration, a flash tank is arranged outside the forced circulation heater to ensure waste heat recovery, a pressure reducing valve and a pressure regulating valve are arranged in a pipeline to stabilize the temperature of the forced circulation heater, and the corrosion caused by the fluctuation of the sulfuric acid concentration due to the change of the temperature is avoided.
In order to solve the technical problems, the invention provides the following technical scheme:
the forced circulation evaporation device used in the concentrated sulfuric acid low-temperature level waste heat recovery process comprises a constant potential rectifier, a forced circulation heater and a flash tank, wherein the forced circulation heater and the flash tank are communicated through a pipeline;
the liquid phase outlet of the flash tank is communicated with the inlet of the forced circulation heater;
a circulating pump is communicated between a tube box inlet of the forced circulation heater and a liquid phase outlet of the flash tank;
an anode protection device is arranged in a shell of the forced circulation heater, and the potentiostat is used for applying current to the anode protection device to form a stable passive film on the surface of equipment contacted with sulfuric acid;
the flash tank is used for controlling the forced circulation heater to be in a preset pressure and temperature range;
the flash tank is arranged outside the forced circulation heater;
the sulfuric acid concentration can fluctuate in the range of more than or equal to 98.5 percent, and the device is used under the working condition that the sulfuric acid temperature is 150-230 ℃.
Preferably, the heat exchange tube bundles in the shell are fully distributed and are composed of a plurality of straight-tube-shaped heat exchange tubes.
Preferably, an expansion joint is arranged on the shell.
Preferably, an impingement plate with small holes is arranged at the acid inlet on the shell.
Preferably, the acid inlet on the shell is in the form of a flaring.
Preferably, a pressure reducing valve is arranged between the outlet of the header of the forced circulation heater and the inlet of the flash tank.
Preferably, the outlet of the flash tank is provided with a pressure regulating valve.
Preferably, the steam outlet of the flash tank is provided with a wire mesh demister.
Preferably, a continuous sewage draining outlet is arranged near the liquid level of the flash tank.
Preferably, an outlet of a tube box of the forced circulation heater is provided with an acid leakage electrode, and the acid leakage electrode is connected with the potentiostat through an electric signal line.
Compared with the prior art, the invention has the following beneficial effects:
(1) The invention provides a forced circulation evaporation device for a concentrated sulfuric acid low-temperature-level waste heat recovery process, which applies current to an anode protection device in a shell of a forced circulation heater through a constant potential rectifier to form a stable passivation film on the surface of equipment contacted with sulfuric acid so as to prevent corrosion caused by fluctuation of the concentration of the sulfuric acid.
(2) The forced circulation evaporation device for the concentrated sulfuric acid low-temperature waste heat recovery process provided by the invention has the advantages that the anode protection device is applied to high-temperature sulfuric acid corrosion-resistant equipment with the temperature of 150-230 ℃ and the acid concentration of more than or equal to 98.5% and less than or equal to 100%, and the corrosion-resistant effect is obvious. Compared with the prior art, the acid concentration fluctuation range is improved, after the anode protection device is applied to the shell of the forced circulation heater at the same high temperature, the corrosion resistance effect of acid concentration of 98.5 percent or more and less than 99 percent is achieved, the corrosion resistance effect of acid concentration of 99 percent or more in the prior art can be achieved, and the corrosion rate is reduced by 86.7 percent; compared with the annual corrosion rate of more than or equal to 99% acid concentration in the prior art at the same temperature, the annual corrosion rate is obviously reduced by about 50% after anodic protection is applied; the forced circulation evaporation device can enlarge the fluctuation range of the acid concentration when the concentration is more than or equal to 98.5% and less than or equal to 100%, the corrosion rate is less than or equal to 0.02mm/a, and the forced circulation evaporation device has the characteristics of low corrosion rate, long service life and large circulation multiplying power, has large elasticity in the concentration range, is easy to operate, and can reasonably utilize the waste heat of concentrated sulfuric acid at a low temperature.
In the actual use of the horizontal steam generator in the prior art, the annual corrosion rate can be reduced only by strictly controlling the concentration of sulfuric acid to be more than or equal to 99%. According to the experimental results, the following components are shown: under the condition of high temperature, the annual corrosion rate of 98.5 percent to 99 percent of acid concentration is increased by nearly 3.7 times compared with the annual corrosion rate of more than or equal to 99 percent of acid concentration, and after the anode protection device is applied, the annual corrosion rate of less than 99 percent of acid concentration can be reduced to the original annual corrosion rate, namely, the corrosion resistance and long-term stable operation of equipment can be ensured even if the absorption rate of sulfur trioxide is reduced and the concentration of sulfuric acid is lower than 99 percent.
(3) The forced circulation evaporation device for the concentrated sulfuric acid low-temperature-level waste heat recovery process provided by the invention realizes forced circulation through the circulating pump arranged on the pipeline communicated with the forced circulation heater through the flash tank, improves the circulation multiplying power, realizes control on the circulation pressure and the steam pressure through the pressure reducing valve and the pressure regulating valve arranged on the pipeline, enlarges the fluctuation range of the concentrated sulfuric acid, and has the advantages of low corrosion rate and long service life.
(4) The forced circulation evaporation device for the concentrated sulfuric acid low-temperature-level waste heat recovery process provided by the invention has the advantages that saturated liquid with a certain pressure is formed in a pipe through heat release of sulfuric acid on the shell side, the pressure is reduced through the pressure reducing valve arranged on the pipeline, the boiling point of the saturated liquid is reduced, then the saturated liquid enters the flash tank, the fluid is rapidly boiled and vaporized in the flash tank due to the fact that the temperature of the fluid is higher than the boiling point under the pressure, two phases are separated, the heating and vaporizing processes are realized in a split mode in the whole process, and compared with a horizontal steam generator in the prior art, the highest salt concentration position is arranged in the flash tank, and stress corrosion cracking of a pipe bundle is avoided.
Compared with the horizontal steam generator in the prior art, the forced circulation heater does not vaporize, does not need to consider the vaporization space, and does not need to consider the impact of vapor bubbles generated by vaporization to the outer wall of the heat exchange tube; the diameter-variable cylinder of the horizontal steam generator is not needed, the equipment manufacturing difficulty is reduced, and the equipment manufacturing period is shortened; the problem of stress corrosion caused by concentration of chloride ions due to evaporation of desalted water is not considered. The heater is fully provided with the pipes, so that the heat exchange efficiency is effectively improved, the equipment structure is compact, and the occupied area is small.
The flash tank can be arranged in a vertical or horizontal mode according to site requirements, the material is preferably carbon steel, and the large volume of the flash tank provides space for rapid vaporization of fluid and vapor-liquid separation. Compared with the prior art, the evaporation space is separated into independent equipment, the overall dimension of the forced circulation heater can be effectively reduced, and the equipment cost is reduced.
The circulating pump ensures the pressure of saturated liquid, and forms forced circulation between the forced circulation heater and the flash tank to reach a certain circulation rate, and the circulation rate is far greater than that of the horizontal steam generator, so that the acid flow rate and the shell pass convection heat transfer coefficient can be improved. Furthermore, the convection heat transfer coefficient of the tube side is effectively improved, and the total heat transfer coefficient can be improved by 10-25%, so that the overall dimension of the shell-and-tube forced circulation heater is greatly reduced, the occupied area is saved, the equipment investment is reduced, and the recovery and utilization of waste heat are realized.
(5) The forced circulation evaporation device for the concentrated sulfuric acid low-temperature level waste heat recovery process provided by the invention has the advantages that the high-temperature concentrated sulfuric acid is fed on the shell side (in the shell), and the desalted water is fed on the tube side. Under the normal operation condition, the temperature difference of the metal wall of the tube shell pass is less than 10 ℃, so that the temperature difference stress of the tube shell pass of the equipment is effectively reduced; compared with the prior art, the concentrated sulfuric acid runs in the shell pass, so that the corrosion caused by direct scouring of the pipe head of the heat exchange pipe due to the large fluid acid amount of the horizontal steam generator is avoided; the heat exchange tube adopts a straight tube, so that the material defects possibly occurring in a U-shaped heat exchange tube bundle are completely avoided, for example, the U-shaped heat exchange tube has plastic deformation during cold bending, the outer edge of the bent tube has large residual tensile stress, and the tensile stress is generated due to temperature difference, and the tensile stress areas are easy to generate stress corrosion cracking under the combined action of sulfuric acid media; the flow form of the horizontal steam generator is half parallel flow and half counter flow, and the forced circulation heater with the anode protection device (the forced circulation heater in the invention is preferably a shell-and-tube heater) is a full counter flow heat transfer structure, so that the heat transfer efficiency can be effectively improved by 2-5%, and the volume of the equipment is reduced; the heat exchange tube bundle completely avoids the continuous sewage outlet position with higher sewage concentration, and avoids the occurrence of stress corrosion caused by chloride ion concentration, thereby prolonging the service life of equipment, having flexible operation, stability and controllability, facilitating the manufacture of system equipment and reducing the production period of the equipment.
(6) According to the forced circulation evaporation device for the concentrated sulfuric acid low-temperature-level waste heat recovery process, the cathodes are preferably alloy rods, and the number of the cathodes is multiple, and the number of the cathodes and the anodes of equipment and the concentrated sulfuric acid in the equipment form a current circulation loop; the anode is a metal wall surface contacted with the sulfuric acid, namely a shell of the forced circulation heater, a heat exchange tube bundle, a tube plate of the forced circulation heater, an impingement baffle and the like; the reference electrode is divided into a control reference electrode and a monitoring reference electrode and is respectively arranged on the acid inlet side and the acid outlet side of the shell through insulation sealing; the constant potential rectifier provides direct current to the anode protection device, so that the anode of the equipment is in a passivation state, and strong corrosion of high-temperature concentrated sulfuric acid to a contact surface is avoided.
The surface of the cathode is preferably coated with an insulating sleeve which has a certain number of small holes and is resistant to concentrated sulfuric acid at 230 ℃, and the material is resistant to corrosion of the concentrated sulfuric acid and cannot be dissolved and deformed at high temperature.
The control reference electrode is used for reading a change value relative to the surface of the anode, the monitoring reference electrode is used for monitoring the potential condition in the equipment, the front ends of the control reference electrode and the reference electrode are only contacted with concentrated sulfuric acid but not contacted with the shell, the insulating sealing material of the control reference electrode and the reference electrode needs to resist the corrosion of the concentrated sulfuric acid at 230 ℃, the material resists the corrosion of the concentrated sulfuric acid, and the material cannot be dissolved and deformed at high temperature.
The potentiostat is used for outputting direct current to the concentrated sulfuric acid forced circulation heater and automatically controlling the anode to be in a passivation state; the control potential range of the potentiostat is an E1-E2 passivation interval taking a reference electrode as a reference, and the current and the potential in the passivation area are characterized in that the current is basically unchanged and the potential is rapidly increased; the stable potentials of the reference electrodes made of different materials in sulfuric acid are different, and the reference electrodes made of different materials are selected, so that the relative change of the E1-E2 interval based on the reference electrode is realized (for example, if the reference electrode A is selected, the E1-E2 interval is-200-400 mV, and if the reference electrode B is selected, the E1-E2 interval is 100-700 mV).
(7) The forced circulation evaporation device for the concentrated sulfuric acid low-temperature-level waste heat recovery process can form a stable passivation film, and can generate anodic polarization by applying a certain current to an anode protection concentrated sulfuric acid device, rapidly pass to a passivation potential, enter a passivation area and maintain the potential in the area, so that the surface of the device contacted with sulfuric acid forms the stable passivation film. The layer of passive film can slow down the erosion corrosion and the uniform corrosion of the sulfuric acid with certain flow velocity to equipment, the anti-scouring effect is completely superior to that of a horizontal steam generator in the prior art, and the protection to the heat exchange tube bundle part is particularly obvious.
(8) The forced circulation evaporation device for the concentrated sulfuric acid low-temperature-level waste heat recovery process provided by the invention is characterized in that an expansion joint is arranged on the shell. Cold, hot-fluid temperature, pressure are different, make the temperature, the pressure of shell side and pipe wall have the difference, when both difference in temperature, pressure differential are great, the problem that this type of difference initiation can effectively be avoided in the setting of expansion joint, prevent because the heat exchange tube that the thermal expansion volume difference of shell side and pipe caused twists, destroys even.
(9) According to the forced circulation evaporation device for the concentrated sulfuric acid low-temperature-level waste heat recovery process, the acid leakage electrode is arranged at the outlet of the pipe box, when leakage occurs, a certain potential signal is sent out through the self-corrosion potential of metal, and a constant potential instrument is connected to the signal wire to give an alarm for liquid leakage in real time.
(10) According to the forced circulation evaporation device for the concentrated sulfuric acid low-temperature waste heat recovery process, the acid inlet of the shell is of a flaring structure, the anti-impact plate is arranged in the shell, and the small holes are formed in the anti-impact plate, so that the impact of large acid on the heat exchange tube bundle can be reduced, the flowing direction of fluid is changed, the impact of large fluid is dispersed, the fluid uniformly and slowly flows through the tube bundle, and the erosion corrosion of sulfuric acid entering the shell on the heat exchange tube is reduced. Through the comparison of the prior art, the damper structure rho v is added 2 The method can reduce about 35 percent, and is beneficial to reducing the scouring force of the heat exchange tube bundle.
The combination of the electrochemical corrosion prevention and the shell side scouring-resistant structure can effectively improve the overall corrosion resistance of the equipment. When a pipe orifice welding seam, a bulging joint position or a pipe wall are corroded and leaked, the acid leakage electrode can alarm leaked liquid in time, the consequences caused by management blind spots and untimely discovery are avoided, and the safety of equipment is improved.
(11) Compared with the prior art, the anode protection concentrated sulfuric acid forced circulation evaporation system shell has the advantages that the heat exchange tubes in the shell are fully distributed in straight tubes, the length of the heat exchange tubes is 9m at most, the length of equipment can reach 11m, the whole equipment is compact, the heat exchange efficiency is high, and the occupied area is small.
(12) The forced circulation evaporation device for the concentrated sulfuric acid low-temperature waste heat recovery process has the advantages that the stable passivation film, the additionally-arranged flaring structure and the anti-scouring plate structure are adopted, and the scouring force and the corrosion rate of a heat exchange tube bundle can be greatly reduced. The combined use of the electrochemical corrosion prevention, the forced circulation evaporation device and the acid leakage detection structure increases an effective corrosion-resistant protective film for the whole equipment, enlarges the fluctuation range of the sulfuric acid concentration, avoids the corrosion aggravation phenomenon caused by temperature fluctuation to the equipment through accurate pressure control, and ensures that the forced circulation device has the characteristics of low corrosion rate, large circulation multiplying power, compact equipment structure, high safety factor and the like.
Drawings
FIG. 1 is a schematic view of the structure of the present invention;
FIG. 2 is a schematic view of a low temperature waste heat recovery system according to the present invention;
in the figure, 1, a potentiostat; 2. a cathode; 3. sealing the end; 4. a pipe box; 5. an exhaust port; 6. a tube sheet; 7. an acid outlet; 8. a housing; 9. an expansion joint; 10. a heat exchange tube bundle; 11. a fender; 12. an acid inlet; 13. a pressure reducing valve; 14. a water supply port; 15. a flash tank; 16. a safety valve; 17. a continuous sewage draining outlet; 18. a steam outlet; 19. a pressure regulating valve; 20. a circulation pump; 21. a periodic sewage draining outlet; 22. an acid leakage electrode; 23. controlling the reference electrode; 24. a saddle; 25. an acid discharge port; 26. monitoring the reference electrode; 27. a channel inlet; 28. a wire mesh demister; 29. and a liquid phase outlet.
Detailed Description
The technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the invention without making creative efforts; all fall within the scope of protection of the present invention.
In the description of the present invention, it should be noted that the terms "upper", "lower", "inner", "outer", "top/bottom", and the like indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of description and simplification of description, but do not indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and thus should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "disposed," "sleeved/connected," "connected," and the like are to be construed broadly, e.g., "connected," which may be fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
As shown in FIG. 1, the invention provides a forced circulation evaporation plant for concentrated sulfuric acid low-temperature waste heat recovery process, which comprises a potentiostat 1, a forced circulation heater and a flash tank 15, wherein the forced circulation heater and the flash tank are communicated;
a liquid phase outlet of the flash tank 15 is communicated with a tube box inlet of the forced circulation heater;
a circulating pump 20 is communicated between a channel inlet 27 of the forced circulation heater and a liquid phase outlet 29 of the flash tank 15;
an anode protection device is arranged in a shell 8 of the forced circulation heater, and the potentiostat 1 is used for applying current to the anode protection device to form a stable passive film on the surface of equipment contacted with sulfuric acid;
the flash tank 15 is used for controlling the forced circulation heater to be in a preset pressure and temperature range;
the flash tank 15 is disposed outside the forced circulation heater.
In the invention, the flash tank 15 can be arranged in a horizontal or vertical structure, and the upper layer in the tank is an evaporation space.
In the present invention, the forced circulation heater is preferably a shell-and-tube heat exchanger, which comprises a tube box 4, a shell 8, a tube plate 6 and a heat exchange tube bundle 10;
the tube box 4 is divided into a front tube box and a rear tube box, the tube plate 6 is divided into a front tube plate and a rear tube plate, the front tube box is provided with an air outlet, a tube box inlet 27 and a seal head 3, the tube box 4 is fixedly connected with the tube plate 6 through a flange, the bottom of the right tube box is provided with a drain outlet, the cathode 2 is arranged on the seal head 3, the shell 8 is respectively welded with the front tube plate and the rear tube plate, the heat exchange tube bundle 10 is arranged in the shell 8 and welded with the front tube plate and the rear tube plate, and the shell 8 is provided with an acid inlet 12, an acid outlet 7 and an acid outlet 25.
The forced circulation evaporation device for the concentrated sulfuric acid low-temperature-level waste heat recovery process provided by the invention controls the pressure of hot desalted water carrying energy in the forced circulation heater through the pressure reducing valve 13, so that the desalted water is ensured not to be vaporized and flashed in the front pipelines of the heat exchanger and the pressure reducing valve 13, the desalted water enters the flash tank 15 after the pressure reducing valve to be flashed with corresponding saturated steam, the steam-liquid separation is carried out after the saturated steam passes through the wire mesh demister 28, and the saturated steam is led out from the outlet at the top of the tank. The saturated steam outlet is provided with a pressure regulating valve 19 for controlling the pressure of the flash steam to meet the production and use requirements of a heat user device, so that the comprehensive utilization of the heat energy of the whole system is realized. The conveying of the desalted water is mainly realized by a circulating pump 20, and the desalted water after flash evaporation is led to a forced circulation heater for circulation by the device, so that the low-temperature waste heat of concentrated sulfuric acid is taken away.
In the present invention, the anode protection device includes an anode and a cathode 2 respectively provided in the case 8 of the forced circulation heater, and the anode is a metal wall surface in contact with concentrated sulfuric acid.
In the present invention, the anode protection device further includes a control reference electrode 23 disposed on the acid inlet 12 side of the housing 8 and a monitoring reference electrode 26 disposed on the acid outlet 7 side of the housing 8 in an insulating and sealing manner, respectively, and the control reference electrode 23 and the monitoring reference electrode 26 are electrically connected to the potentiostat 1, respectively.
In the invention, a plurality of cathodes 2 are arranged in parallel heat exchange tube bundles 10 in multiple rows and columns, and the cathodes 2 are externally provided with an insulating sleeve with openings, so that the cathodes 2 cannot be contacted with an anode, the opening density is uniform, and the uniform current distribution is ensured; the cathode insulating sleeve needs not to deform and corrode under the working condition of concentrated sulfuric acid at 230 ℃. The front ends of the control reference electrode 23 and the monitoring reference electrode 26 are only contacted with concentrated sulfuric acid and are not contacted with the shell body 8, the monitoring reference electrode 26 is used for monitoring the potential condition in the device, and the control reference electrode 23 is used for reading a change value relative to the surface of the anode.
The potentiostat 1 is used for outputting direct current to the concentrated sulfuric acid forced circulation heater and automatically controlling the anode to be in a passivation state; the control potential range of the potentiostat 1 is an E1-E2 passivation interval taking a reference electrode as a reference, and the current and the potential in the passivation area are characterized in that the current is basically unchanged and the potential is rapidly increased; the stable potentials of the reference electrodes made of different materials in sulfuric acid are different, and the reference electrodes made of different materials are selected, so that the interval from E1 to E2 based on the reference electrode is relatively changed (for example, if the reference electrode A is selected, the interval from E1 to E2 is-200-400 mV, and if the reference electrode B is selected, the interval from E1 to E2 is 100-700 mV).
In the invention, the heat exchange tube bundle 10 in the shell 8 is composed of a plurality of straight-tube-shaped heat exchange tubes, and the tube diameter of the tube bundle can be adopted considering that the acid speed meets the erosion corrosion resistant rate of the anode protection passivation film
Heat exchange tubes with different tube diameters are equal, so that the arrangement mode of the tube spacing meets the flow velocity of sulfuric acid required by anode protection, and the passive film on the surface of the heat exchange tube bundle is prevented from being damaged by sulfuric acid scouring; contrast prior art, the heat exchange tube adopts full stringing in the casing, avoids the liquid level fluctuation condition, causes the too high condition of local heat exchanger tube bank temperature.
In the invention, the heat exchange tube is provided with a baffle plate.
In the invention, the shell 8 is provided with an expansion joint 9, and further, the bottom of the expansion joint 9 is provided with a drain port.
In the invention, the acid inlet 12 on the shell 8 is provided with an anti-scouring buffer device.
In the invention, the anti-scouring buffer device is an anti-scouring plate 11 provided with small holes, and a plurality of small holes are formed according to the calculation of the flow area.
In the invention, the acid inlet 12 on the shell 8 is welded on the shell 8 in a flaring manner, a reinforcing ring is added at the joint to increase the strength, the large acid flow rate of the acid inlet pipe is slowed down, furthermore, the acid inlet 12 is preferably set to be an elliptical flaring structure, the anti-scouring plate 11 is arranged right below the acid inlet, the central line of the anti-scouring plate coincides with the central line of the acid inlet pipe, a plurality of openings are arranged on the baffle, the side wall of the anti-scouring plate is firmly welded with the inner wall of the pipe, and the phenomenon that the anti-scouring structure falls off due to large impact force and is irregularly scurried to cause the failure of the anti-scouring structure is avoided.
In the invention, the passive film formed by the anode protection device is matched with the flaring form of the acid inlet 12 and the impingement baffle with a small hole, so that the erosion and corrosion of the heat exchange tube bundle 10 caused by large acid amount in the acid inlet 12 can be further reduced and prevented.
In the present invention, a pressure reducing valve 13 is provided between the outlet of the header of the forced circulation heater and the inlet of the flash tank 15.
In the present invention, the outlet of the flash tank 15 is provided with a pressure regulating valve 19.
In the invention, an acid leakage electrode 22 is arranged at the outlet of the tube box of the shell 8, and the acid leakage electrode 22 is connected with the potentiostat 1 through an electric signal line and is used for DCS signal transmission. When leakage occurs, a certain potential signal is sent out through the self-corrosion potential of the metal, and the signal line is connected to the constant potential rectifier 1 of the anode protection system to carry out real-time sound control alarm on the acid leakage phenomenon.
In the present invention, the steam outlet 18 of the flash tank 15 is provided with a wire mesh demister 28.
In the present invention, a safety valve 16 and a pressure gauge are provided on the top of the flash tank 15.
In the present invention, a continuous drain outlet 17 is provided near the liquid level of the flash tank 15.
In the present invention, the flash tank 15 and the forced circulation heater are disposed at upper and lower positions.
In the invention, the flash tank 15 is also provided with a water supply port 14, and the bottom of the flash tank is provided with a regular sewage draining port 21.
In the invention, a saddle 24 for supporting the forced circulation heater is arranged at the bottom end of the forced circulation heater, and further, the saddle 24 is arranged in a bilateral symmetry manner, the left saddle is a fixed saddle, and the right saddle is a sliding saddle. An acid discharge port 25 is arranged in the middle of the two saddles.
In the invention, a flash tank 15 is connected with a shell-and-tube forced circulation heater with an anode protection device through a tube group, a liquid phase outlet of the flash tank 15 is connected with a tube box inlet connecting tube of the forced circulation heater, a tube box outlet of the forced circulation heater is connected with an inlet of the flash tank 15, a pressure reducing valve 13 and a circulating pump 20 are arranged in a pipeline, and a large volume of the flash tank 15 provides a space for rapid vaporization of fluid and vapor-liquid separation.
A steam outlet 18 is arranged above the flash tank, a safety valve 16 and a pressure gauge are arranged at the top of the flash tank, a wire mesh demister 28 is arranged in front of the steam outlet 18, a continuous sewage draining outlet 17 and a liquid level meter are arranged near the liquid level of the tank body, and an acid draining outlet 25 is arranged at the bottom of the shell 8. Contrast prior art equipment, with continuous waste fitting discharging from equipment tube bank district, shift to the 15 liquid level districts of flash tank, guarantee that heat exchanger tube bundle 10 avoids the highest continuous drain of sewage concentration to set for the position, avoid local stress corrosion's emergence to the life of extension equipment.
The circulating pump 20 needs to satisfy the circulating pressure of the saturated liquid, and forms forced circulation of the fluid between the forced circulation heater and the flash tank 15, so that a certain circulation rate is achieved, the heat exchange efficiency is effectively improved, the acid concentration fluctuation range is enlarged, and the corrosion resistance is improved.
As shown in fig. 2, the forced circulation evaporation apparatus for concentrated sulfuric acid low-temperature waste heat recovery process provided by the present invention uses the anode protection concentrated sulfuric acid forced circulation evaporation apparatus as a core device, and forms a sulfuric acid waste heat system recovery apparatus together with a heat recovery tower, a circulating acid pump, a concentrated acid diluter, and other devices. The diluted concentrated sulfuric acid absorbs sulfur trioxide in a heat recovery tower, forms concentrated sulfuric acid with the temperature of less than or equal to 230 ℃ and the concentration of more than or equal to 98.5 percent at the bottom of the tower, and then sends the concentrated sulfuric acid to an anode protection concentrated sulfuric acid forced circulation evaporation device through a circulating acid pump to produce saturated steam with the pressure of 0.6-1.0 MPa. Absorption of SO by sulfuric acid 3 The concentration is increased, water is added again through the diluter to maintain the concentration, and the circulating acid after water is added returns to the heat recovery tower for absorption, namelyThe waste heat recovery of the primary sulfuric acid is realized.
Concentrated sulfuric acid with the temperature of less than or equal to 230 ℃ and the concentration of more than or equal to 98.5 percent is formed at the bottom of the tower and is sent to a concentrated sulfuric acid forced circulation heater applying an anode protection device through a circulating acid pump, so that the high temperature resistance and the sulfuric acid corrosion resistance with certain concentration in the saturated steam production process are improved. The safe and stable circulation process for realizing the recovery of the waste heat of the sulfuric acid is ensured.
The above description is only a preferred embodiment of the present invention, but the scope of the present invention is not limited thereto. Any person skilled in the art can substitute or change the technical solution of the present invention and its modified concept equally or differently within the technical scope of the present disclosure; are intended to be covered by the scope of the present invention.
Claims (10)
1. The forced circulation evaporation device for the concentrated sulfuric acid low-temperature-level waste heat recovery process is characterized by comprising a constant potential rectifier, a forced circulation heater and a flash tank which are communicated with each other;
the liquid phase outlet of the flash tank is communicated with the inlet of the forced circulation heater;
a circulating pump is communicated between a tube box inlet of the forced circulation heater and a liquid phase outlet of the flash tank;
an anode protection device is arranged in a shell of the forced circulation heater, and the potentiostat is used for applying current to the anode protection device to form a stable passive film on the surface of equipment contacted with sulfuric acid;
the flash tank is used for controlling the forced circulation heater to be in a preset pressure and temperature range;
the flash tank is arranged outside the forced circulation heater;
the concentration of the sulfuric acid can fluctuate in the range of more than or equal to 98.5 percent, and the method is used under the working condition that the temperature of the sulfuric acid is 150-230 ℃.
2. The forced circulation evaporation device for concentrated sulfuric acid low-temperature waste heat recovery process as claimed in claim 1, wherein the heat exchange tube bundle in the shell is fully distributed and is composed of a plurality of heat exchange tubes in a straight tube shape.
3. The forced circulation evaporation device for concentrated sulfuric acid low-temperature residual heat recovery process according to claim 1, wherein an expansion joint is arranged on the shell.
4. The forced circulation evaporation device for concentrated sulfuric acid low-temperature waste heat recovery process as claimed in claim 1, wherein the acid inlet on the shell is provided with an impingement plate with small holes.
5. The forced circulation evaporation device for the concentrated sulfuric acid low-temperature residual heat recovery process according to claim 1, wherein the acid inlet on the shell is in a flaring form.
6. The forced circulation evaporation device for concentrated sulfuric acid low-temperature-level waste heat recovery process as claimed in claim 1, wherein a pressure reducing valve is arranged between the outlet of the tube box of the forced circulation heater and the inlet of the flash tank.
7. The forced circulation evaporation device for concentrated sulfuric acid low-temperature-level waste heat recovery process as claimed in claim 1, wherein the outlet of the flash tank is provided with a pressure regulating valve.
8. The forced circulation evaporation device for the concentrated sulfuric acid low-temperature-level waste heat recovery process as claimed in claim 1, wherein a wire mesh demister is arranged at a steam outlet of the flash tank.
9. The forced circulation evaporation device for the concentrated sulfuric acid low-temperature level waste heat recovery process as claimed in claim 1, wherein a continuous sewage draining outlet is arranged near the liquid level of the flash tank.
10. The forced circulation evaporation device for concentrated sulfuric acid low-temperature-level waste heat recovery process as claimed in claim 1, wherein an outlet of a tube box of the forced circulation heater is provided with an acid leakage electrode, and the acid leakage electrode is connected with the potentiostat through an electric signal line.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211297453.6A CN115899656A (en) | 2022-10-21 | 2022-10-21 | Forced circulation evaporation device for concentrated sulfuric acid low-temperature-level waste heat recovery process |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211297453.6A CN115899656A (en) | 2022-10-21 | 2022-10-21 | Forced circulation evaporation device for concentrated sulfuric acid low-temperature-level waste heat recovery process |
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| Publication Number | Publication Date |
|---|---|
| CN115899656A true CN115899656A (en) | 2023-04-04 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202211297453.6A Pending CN115899656A (en) | 2022-10-21 | 2022-10-21 | Forced circulation evaporation device for concentrated sulfuric acid low-temperature-level waste heat recovery process |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN115899656A (en) |
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2022
- 2022-10-21 CN CN202211297453.6A patent/CN115899656A/en active Pending
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