Process and system for efficient oxidation of calcium-based semi-dry desulfurization ash and preparation of gypsum

Abstract

The present invention provides a process and system for efficiently oxidizing calcium-based semi-dry desulfurization ash and preparing gypsum. The process includes desulfurizing target flue gas to obtain coarse ash and desulfurized flue gas, then removing dust from the desulfurized flue gas to obtain fine ash. The process also includes conveying the coarse ash and fine ash to a coarse ash oxidation reactor and a fine ash oxidation reactor, respectively, adding water and introducing an oxygen-containing gas thereto, while simultaneously heating the coarse ash and fine ash, and oxidizing the coarse ash and fine ash separately under stirring conditions to obtain a limestone slurry after oxidation. The limestone slurry is then dehydrated in a dehydration device to obtain gypsum. This process allows the oxidation reactions of the coarse ash and fine ash to proceed under heating conditions, which is beneficial for improving the operating cycle. Separately oxidizing the coarse ash and fine ash generated by the flue gas desulfurization and dust removal device facilitates controlling the oxidation reaction time for calcium-based semi-dry desulfurization ash of different particle sizes, further improving the operating cycle and significantly improving the quality of the finished gypsum.

Description

Technical Field

[0001] The invention relates to a process and system for efficiently oxidizing calcium-based semi-dry desulfurization ash and preparing gypsum, belonging to the technical field of desulfurization and post-processing thereof. Background Art

[0002] Currently, there are three main methods for treating sulfur dioxide pollutants in this field: dry desulfurization, semi-dry desulfurization, and wet desulfurization. Wet desulfurization is widely used in coal-fired power plants due to its adaptability to various coal types and its high and stable desulfurization efficiency. However, this system is relatively complex, consumes a lot of water, and has high initial investment and operation and maintenance costs. It is prone to wear and corrosion of equipment and is prone to the formation of "white plume" near the chimney. Therefore, in the context of ultra-low emissions, most companies in the steel industry use semi-dry desulfurization. This desulfurization process has high desulfurization efficiency, is simple, consumes little water, and produces no wastewater or "white plume" during production. However, the desulfurization ash produced by this process is unstable and contains a large amount of calcium sulfite. Its main disposal method is landfill or external disposal. However, this treatment method is not only not conducive to the development of renewable resources, but also increases the risk of enterprises. Therefore, the reuse of desulfurization ash is an urgent problem to be solved in this field.

[0003] Prior art 1 related to the present invention:

[0004] Technical solution of prior art 1:

[0005] Chinese patent CN109876759A discloses a method and device for accelerating the oxidation of calcium sulfite in desulfurization ash using low-temperature exhaust gas, which is to pass low-temperature flue gas into calcium sulfite slurry to provide an oxygen source and the required heat for the oxidation of calcium sulfite.

[0006] Disadvantages of the prior art 1:

[0007] The method provided in the first prior art can achieve the purpose of utilizing low-temperature energy and thus saving energy consumption, but the reaction temperature of calcium sulfite in this process is low, and calcium sulfite cannot achieve a high oxidation rate in a short time, resulting in a prolonged reaction time and inability to discharge the reaction slurry in time.

[0008] The second prior art related to the present invention:

[0009] Technical solution of existing technology 2:

[0010] Chinese patent CN210286777U discloses a system for efficiently utilizing desulfurization by-products, which transports the ash at the bottom of the desulfurization tower and the desulfurization ash at the bottom of the bag dust collector to a gypsum preparation tank to prepare gypsum in the gypsum preparation tank. The system uses flue gas waste heat to heat the temperature of the reaction tank and simultaneously introduces ozone to achieve the purpose of oxidizing calcium sulfite.

[0011] Disadvantages of the second prior art:

[0012] The desulfurization by-product efficient utilization system and the desulfurization by-product efficient utilization process using the system disclosed in the second prior art can solve the problem of reusing desulfurization by-products, but the process does not treat the desulfurization tower ash and the ash storage ash separately. The particle sizes of the desulfurization tower ash and the ash storage ash are quite different. The desulfurization tower ash and the ash storage ash are oxidized at the same time during the preparation of gypsum. The reaction time of calcium sulfite with a large difference in particle size is inconsistent, which will cause part of the calcium sulfite to be discharged before the reaction is complete, thereby causing the quality of the finished gypsum to deteriorate; at the same time, the process uses the waste heat of flue gas as a heat source for heating, which will cause the reaction temperature of the calcium sulfite slurry to be low, the reaction rate to be slow, and the cycle to be long; and using ozone as an oxidant to oxidize calcium sulfite may cause partial decomposition of ozone before utilization, thereby affecting the oxidation rate and causing an increase in reaction time.

[0013] The third prior art related to the present invention:

[0014] Technical solution of existing technology three:

[0015] Chinese patent CN107126830A discloses a sodium-calcium-based combined desulfurization and dust removal (SDG) system and method for coke oven flue gas based on SDA. The system transports the desulfurization ash in the SDA desulfurization ash reservoir to a desulfurizer regeneration tank for regeneration. At the same time, slaked lime is added as a desulfurizer regeneration agent to obtain a more active NaOH desulfurizer. The desulfurizer is then transported to a desulfurizer liquid supply tank through a cyclone and then pumped into a desulfurization tower for desulfurization.

[0016] Disadvantages of the existing technology three:

[0017] Although the process in the third prior art can realize the reuse of sodium-based desulfurization ash and can greatly improve the utilization rate of by-products, this process is mainly aimed at sodium-based desulfurization, and the desulfurization ash is regenerated into a desulfurizer by reacting with slaked lime, while the circulating fluidized bed (CFB) mostly uses a calcium-based desulfurizer. Therefore, this process cannot be applied to the treatment of CFB semi-dry desulfurization ash.

[0018] Therefore, providing a new process and system for the efficient oxidation of calcium-based semi-dry desulfurization ash and preparation of gypsum has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0019] In order to solve the above-mentioned shortcomings and deficiencies, an object of the present invention is to provide a process for efficiently oxidizing calcium-based semi-dry desulfurization ash and preparing gypsum.

[0020] Another object of the present invention is to provide a system for efficiently oxidizing calcium-based semi-dry desulfurization ash and preparing gypsum.

[0021] To achieve the above objectives, the present invention provides, on the one hand, a process for efficiently oxidizing calcium-based semi-dry desulfurization ash and preparing gypsum, comprising: desulfurizing target flue gas in a desulfurization tower to obtain coarse ash and desulfurized flue gas; and then removing dust from the desulfurized flue gas in a dust collector to obtain fine ash and purified flue gas. The process further comprises:

[0022] (1) transporting coarse ash and fine ash to a coarse ash oxidation reactor and a fine ash oxidation reactor, respectively, then adding water and introducing oxygen-containing gas into the coarse ash oxidation reactor and the fine ash oxidation reactor, respectively, heating the coarse ash oxidation reactor and the fine ash oxidation reactor, and oxidizing the coarse ash and the fine ash under stirring conditions, respectively, to obtain limestone slurry after the oxidation is completed;

[0023] (2) The limestone slurry is dehydrated in a dehydrating device to obtain gypsum.

[0024] As a specific embodiment of the above process of the present invention, the process further comprises:

[0025] The coarse ash and the fine ash are mixed and then put into a vibrating screen for separation, and the coarse ash and the fine ash are obtained after separation. The particle size of the coarse ash is greater than 0.15 mm, and the particle size of the fine ash is less than 0.15 mm.

[0026] The coarse ash particles and the fine ash particles are then transported to the coarse ash oxidation reactor and the fine ash oxidation reactor respectively to be oxidized.

[0027] As a specific embodiment of the process described above, step (1) further comprises: adding a pH regulator to the coarse ash oxidation reactor and the fine ash oxidation reactor, respectively, so that the oxidation is carried out at a pH value of 4-5.

[0028] In some embodiments of the present invention, the pH adjuster may be, for example, dilute sulfuric acid.

[0029] As a specific embodiment of the process described above, step (1) further comprises: adding a catalyst to the coarse ash oxidation reactor and the fine ash oxidation reactor respectively, and the concentration of the catalyst is 0.0008-0.001 mol / L.

[0030] In the present invention, the concentration of the catalyst is calculated based on the total volume of the liquid solution formed after adding water into the reactor.

[0031] In some embodiments of the present invention, the catalyst may be a conventional catalyst used in the art, and may be reasonably selected according to the actual operation requirements on site; for example, the catalyst may be Mn 2+ 、Fe 3+ 、Cu 2+ wait.

[0032] As a specific embodiment of the process described above of the present invention, in step (1), the oxidation is carried out at a temperature greater than 300°C, an oxygen content in the solution (i.e., a liquid solution formed after adding water to the reactor) of greater than 20v%, the coarse ash oxidation time is 60-90 minutes, and the fine ash oxidation time is 40-60 minutes.

[0033] In the present invention, oxidation of calcium-based semi-dry desulfurization ash at a higher temperature helps to increase the oxidation reaction rate and shorten the reaction period.

[0034] As a specific embodiment of the above process of the present invention, in step (1), the oxygen-containing gas includes target flue gas and / or air.

[0035] As a specific embodiment of the process described above, step (2) further comprises: spraying an acidic medium into the dehydration device to perform acid washing on the limestone slurry while dehydrating, thereby removing heavy metals and obtaining high-quality gypsum.

[0036] In some embodiments of the present invention, the acidic medium may be, for example, hydrochloric acid.

[0037] In the present invention, the coarse ash and fine ash are both calcium-based semi-dry desulfurization ash.

[0038] On the other hand, the present invention also provides a system for efficiently oxidizing calcium-based semi-dry desulfurization ash and preparing gypsum, which is used to achieve the above-mentioned process of efficiently oxidizing calcium-based semi-dry desulfurization ash and preparing gypsum, comprising a flue gas desulfurization and dust removal device, the flue gas desulfurization and dust removal device comprising a desulfurization tower and a dust collector, the purified gas outlet of the desulfurization tower being connected to the inlet of the dust collector, wherein the system further comprises: a coarse ash storage tank, a fine ash storage tank, a coarse ash oxidation reactor, a fine ash oxidation reactor, a heating device, a dehydration device and a gypsum storage tank;

[0039] The coarse ash outlet and fine ash outlet of the desulfurization tower and dust collector are respectively connected to the inlets of the coarse ash storage tank and the fine ash storage tank through pipelines. The outlets of the coarse ash storage tank and the fine ash storage tank are respectively connected to the inlets of the coarse ash oxidation reactor and the fine ash oxidation reactor through pipelines. The slurry outlets of the coarse ash oxidation reactor and the fine ash oxidation reactor are respectively connected to the inlet of the dehydration device through slurry conveying pipes. The outlet of the dehydration device is connected to the inlet of the gypsum storage tank through a discharge pipe.

[0040] The coarse ash oxidation reactor and the fine ash oxidation reactor are respectively provided with a stirrer, a water supply pipe and a gas outlet are respectively provided on the top, and a gas delivery pipe is respectively provided on the bottom;

[0041] The heating device is used to heat the coarse ash oxidation reactor and the fine ash oxidation reactor.

[0042] As a specific embodiment of the above-mentioned system of the present invention, the system further includes a vibrating screen, and the coarse ash outlet and fine ash outlet of the desulfurization tower and the dust collector are respectively connected to the inlet of the vibrating screen through pipes, and the coarse particle ash outlet and fine particle ash outlet of the vibrating screen are respectively connected to the inlets of the coarse ash storage tank and the fine ash storage tank through pipes.

[0043] As a specific embodiment of the above system of the present invention, an acid spraying pipe is provided on the top of the dehydration device for spraying the acidic medium into the dehydration device.

[0044] In some embodiments of the present invention, the dehydration device may be, for example, a gypsum dehydrator.

[0045] When the system is used to efficiently oxidize calcium-based semi-dry desulfurization ash and prepare gypsum, an acidic medium can be sprayed into the dehydration device through an acid spray pipe to perform acid washing on the product obtained after dehydration, thereby reducing the heavy metal content therein and improving the quality of the gypsum.

[0046] As a specific embodiment of the above system of the present invention, heating resistors or ceramic heating plates are laid on the inner wall surfaces of the coarse ash oxidation reactor and the fine ash oxidation reactor respectively.

[0047] When utilizing the system for the efficient oxidation of calcium-based semi-dry desulfurization ash and the preparation of gypsum, the temperature within the reactor can be varied by adjusting the resistance and number of the heating resistors or ceramic heating plates to ensure that the oxidation reaction proceeds at the target temperature, thereby accelerating the reaction rate of the solution and shortening the reaction time and operating cycle. Furthermore, the present invention does not impose specific requirements on the location and specific arrangement of the heating resistors or ceramic heating plates on the reactor inner wall. These can be reasonably adjusted based on actual on-site operational needs, as long as the oxidation reaction proceeds at the target temperature.

[0048] As a specific embodiment of the above-mentioned system of the present invention, the tops of the coarse ash oxidation reactor and the fine ash oxidation reactor are respectively provided with regulating pipes.

[0049] When the system is used to efficiently oxidize calcium-based semi-dry desulfurization ash and prepare gypsum, a pH regulator and a catalyst can be added to the coarse ash oxidation reactor and the fine ash oxidation reactor respectively through the regulating pipe to adjust the pH value of the solution in the reactor so that an acidic environment suitable for the oxidation reaction is achieved in the reactor; and the added catalyst can accelerate the oxidation reaction rate and shorten the operating cycle of the reactor.

[0050] As a specific embodiment of the above-mentioned system of the present invention, an aeration device is respectively provided at the bottom air inlet position in the coarse ash oxidation reactor and the fine ash oxidation reactor, and the gas delivery pipe is connected to the aeration device.

[0051] When the system is used to efficiently oxidize calcium-based semi-dry desulfurization ash and prepare gypsum, oxygen-containing gas can be transported to the coarse ash oxidation reactor and the fine ash oxidation reactor through a gas delivery pipe. The oxygen-containing gas is released into the reactor after passing through an aeration device, which can increase the contact area between the gas and the slurry, accelerate the reaction process, speed up the oxidation reaction rate, shorten the reaction time, and improve the cycle operation capacity.

[0052] As a specific embodiment of the above-mentioned system of the present invention, the outlets of the coarse ash storage tank and the fine ash storage tank are connected to the inlets of the coarse ash oxidation reactor and the fine ash oxidation reactor respectively through pipelines via the coarse ash delivery pump and the fine ash delivery pump.

[0053] As a specific embodiment of the above system of the present invention, the slurry outlets of the coarse ash oxidation reactor and the fine ash oxidation reactor are connected to the inlet of the dehydration device through a slurry delivery pipe via a slurry delivery pump.

[0054] As a specific embodiment of the above-mentioned system of the present invention, the coarse ash oxidation reactor and the fine ash oxidation reactor can be arranged separately or side by side, that is, they share the same side wall.

[0055] As a specific embodiment of the above system of the present invention, the dust collector is a bag dust collector.

[0056] The process and system for the efficient oxidation of calcium-based semi-dry desulfurization ash and preparation of gypsum provided by the present invention heat the coarse ash oxidation reactor and the fine ash oxidation reactor respectively so that the oxidation reaction of the coarse ash and the fine ash is carried out under heating conditions, which is beneficial to improving the operation cycle, and the coarse ash and fine ash generated by the flue gas desulfurization and dust removal device are oxidized separately in the coarse ash oxidation reactor and the fine ash oxidation reactor respectively, which is beneficial to control the oxidation reaction time for calcium-based semi-dry desulfurization ash with different particle sizes, can further improve the operation cycle, and to a certain extent, can better improve the quality of the finished gypsum.

[0057] The process and system for efficiently oxidizing calcium-based semi-dry desulfurization ash and preparing gypsum provided by the present invention classify the calcium-based semi-dry desulfurization ash and then efficiently oxidize it separately, and then prepare high-quality finished gypsum from the limestone slurry obtained by oxidation. Therefore, the present invention can realize the recycling and reuse of calcium-based semi-dry desulfurization ash, achieving the purpose of economic efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0059] Figure 1 This is a schematic structural diagram of the system for efficiently oxidizing calcium-based semi-dry desulfurization ash and preparing gypsum provided in Example 1 of the present invention.

[0060] Figure 2 This is a schematic structural diagram of the system for efficiently oxidizing calcium-based semi-dry desulfurization ash and preparing gypsum provided in Example 2 of the present invention.

[0061] Description of main figures:

[0062] 1. Target flue gas;

[0063] 2. Desulfurization tower;

[0064] 3. Bag dust collector;

[0065] 4. Coarse ash storage tank;

[0066] 5. Fine ash storage tank;

[0067] 6. Coarse ash conveying pump;

[0068] 7. Fine ash conveying pump;

[0069] 8. Coarse ash oxidation reactor;

[0070] 81. First gas delivery pipe;

[0071] 82. First electric stirrer;

[0072] 83. First air outlet;

[0073] 84. First water pipe;

[0074] 85. First regulating tube;

[0075] 9. Fine ash oxidation reactor;

[0076] 91. Second gas delivery pipe;

[0077] 92. Second electric stirrer;

[0078] 93. Second air outlet;

[0079] 94. Second water pipe;

[0080] 95. Second regulating tube;

[0081] 10. Heating resistor;

[0082] 16. Slurry delivery pump;

[0083] 17. Acid spray pipe;

[0084] 18. Dehydration device;

[0085] 19. Gypsum storage tank;

[0086] 20. Vibrating screen;

[0087] 21. Butterfly valve. DETAILED DESCRIPTION

[0088] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below in conjunction with the accompanying drawings and Examples. The following embodiments are part of the present invention, rather than all of the embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. If specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0089] It should be noted that the term "comprise" and any variations thereof in the specification and claims of the present invention and the above-mentioned drawings are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or are inherent to these processes, methods, products or devices.

[0090] In the present invention, terms such as "upper," "lower," "inner," "outer," "middle," "top," and "bottom" indicate positions or locations based on the positions or locations shown in the accompanying drawings. These terms are primarily intended to better describe the present invention and its embodiments and are not intended to limit the devices, elements, or components indicated to specific positions, or to their construction or operation in a specific orientation.

[0091] Moreover, some of the above terms may be used to express other meanings in addition to indicating orientation or positional relationships. For example, the technical term “on” may also be used to indicate a dependency or connection relationship in certain circumstances.

[0092] For those skilled in the art, the specific meanings of these terms in the present invention can be understood according to specific circumstances.

[0093] Furthermore, the terms "disposed" and "connected" should be interpreted broadly. For example, "connected" can mean a fixed connection, a removable connection, or an integral structure; it can also be a mechanical connection or an electrical connection; it can also be a direct connection, an indirect connection through an intermediary, or an internal communication between two devices, elements, or components. Those skilled in the art will understand the specific meanings of these terms in the present invention based on specific circumstances.

[0094] The "range" disclosed in the present invention is given in the form of a lower limit and an upper limit. It can be one or more lower limits, and one or more upper limits respectively. A given range is defined by selecting a lower limit and an upper limit. The selected lower limit and upper limit define the boundaries of a particular range. All ranges defined in this way are combinable, i.e., any lower limit can be combined with any upper limit to form a range. For example, a range of 60-120 and 80-110 is listed for a particular parameter, and it is understood that a range of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​listed are 1 and 2, and the maximum range values ​​listed are 3, 4, and 5, then the following ranges can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5.

[0095] In the present invention, unless otherwise specified, the numerical range "ab" is an abbreviation for any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" are listed in this invention, and "0-5" is merely an abbreviation for these numerical combinations.

[0096] In the present invention, unless otherwise specified, all embodiments and preferred embodiments mentioned in the present invention can be combined with each other to form a new technical solution.

[0097] In the present invention, unless otherwise specified, all technical features and preferred features mentioned in the present invention can be combined with each other to form a new technical solution.

[0098] Example 1

[0099] This embodiment provides a system for efficiently oxidizing calcium-based semi-dry desulfurization ash and preparing gypsum, the structural diagram of which is shown in FIG. Figure 1 As shown, from Figure 1 As can be seen, the system includes:

[0100] Flue gas desulfurization and dust removal device, coarse ash storage tank 4, fine ash storage tank 5, coarse ash oxidation reactor 8, fine ash oxidation reactor 9, heating device (not shown in the figure), dehydration device 18 and gypsum storage tank 19;

[0101] The flue gas desulfurization and dust removal device includes a desulfurization tower 2 and a bag dust collector 3. The target flue gas 1 enters the desulfurization tower 2 from the bottom flue gas inlet of the desulfurization tower 2 through a pipeline. The purified gas outlet of the desulfurization tower 2 is connected to the inlet of the bag dust collector 3.

[0102] The coarse ash outlet and the fine ash outlet of the desulfurization tower 2 and the bag filter 3 are respectively connected to the inlets of the coarse ash storage tank 4 and the fine ash storage tank 5 through pipelines. The bottom outlets of the coarse ash storage tank 4 and the fine ash storage tank 5 are respectively connected to the inlets of the coarse ash oxidation reactor 8 and the fine ash oxidation reactor 9 through pipelines via the coarse ash delivery pump 6 and the fine ash delivery pump 7. The slurry outlets of the coarse ash oxidation reactor 8 and the fine ash oxidation reactor 9 are respectively connected to the inlet of the dehydration device 18 through the first slurry delivery pipe and the second slurry delivery pipe located at the bottom via the slurry delivery pump 16. The outlet of the dehydration device 18 is connected to the inlet of the gypsum storage tank 19 through a discharge pipe.

[0103] An acid spraying pipe 17 is provided on the top of the dehydration device 18 for spraying an acidic medium into the dehydration device 18;

[0104] The coarse ash oxidation reactor 8 is provided with a first electric stirrer 82, a first water supply pipe 84, a first regulating pipe 85 and a first gas outlet 84 are provided on the top, and a first gas delivery pipe 81 is provided on the bottom;

[0105] The fine ash oxidation reactor 9 is provided with a second electric stirrer 92, a second water supply pipe 94, a second regulating pipe 95 and a second gas outlet 93 are provided on the top, and a second gas delivery pipe 91 is provided on the bottom;

[0106] In this embodiment, the coarse ash oxidation reactor 8 and the fine ash oxidation reactor 9 share the same side wall, and a certain number of heating resistors 10 are laid on the inner wall surfaces of the coarse ash oxidation reactor 8 and the fine ash oxidation reactor 9 respectively;

[0107] The target flue gas 1 pipeline is also connected to one end of the first gas delivery pipe 81 and the second gas delivery pipe 91 via a butterfly valve 21;

[0108] The coarse ash oxidation reactor 8 and the fine ash oxidation reactor 9 are provided with a first aeration device and a second aeration device at the bottom air inlet position, respectively. The other ends of the first gas delivery pipe 81 and the second gas delivery pipe 91 are connected to the first aeration device and the second aeration device, respectively.

[0109] The heating device is used to heat the coarse ash oxidation reactor 8 and the fine ash oxidation reactor 9.

[0110] In this embodiment, the desulfurization tower 2 is a circulating fluidized bed (CFB) desulfurization tower commonly used in the art. A certain number of Venturi tube accelerators are arranged inside the desulfurization tower 2. The target flue gas 1 and the desulfurizer are accelerated by the Venturi to complete desulfurization in the desulfurization tower 2.

[0111] Example 2

[0112] This embodiment provides a system for efficiently oxidizing calcium-based semi-dry desulfurization ash and preparing gypsum, the structural diagram of which is shown in FIG. Figure 2 As shown, from Figure 2 As can be seen, the system includes:

[0113] Flue gas desulfurization and dust removal device, coarse ash storage tank 4, fine ash storage tank 5, coarse ash oxidation reactor 8, fine ash oxidation reactor 9, heating device (not shown in the figure), dehydration device 18, gypsum storage tank 19 and vibrating screen 20;

[0114] The flue gas desulfurization and dust removal device includes a desulfurization tower 2 and a bag dust collector 3. The target flue gas 1 enters the desulfurization tower 2 from the bottom flue gas inlet of the desulfurization tower 2 through a pipeline. The purified gas outlet of the desulfurization tower 2 is connected to the inlet of the bag dust collector 3.

[0115] The coarse ash outlet and the fine ash outlet of the desulfurization tower 2 and the bag filter 3 are respectively connected to the inlet of the vibrating screen 20 through pipes. The coarse particle ash outlet and the fine particle ash outlet of the vibrating screen 20 are respectively connected to the inlets of the coarse ash storage tank 4 and the fine ash storage tank 5 through pipes. The bottom outlets of the coarse ash storage tank 4 and the fine ash storage tank 5 are respectively connected to the inlets of the coarse ash oxidation reactor 8 and the fine ash oxidation reactor 9 through pipes via the coarse ash delivery pump 6 and the fine ash delivery pump 7. The slurry outlets of the coarse ash oxidation reactor 8 and the fine ash oxidation reactor 9 are respectively connected to the inlet of the dehydration device 18 through the first slurry delivery pipe and the second slurry delivery pipe located at the bottom via the slurry delivery pump 16. The outlet of the dehydration device 18 is connected to the inlet of the gypsum storage tank 19 through a discharge pipe.

[0116] An acid spraying pipe 17 is provided on the top of the dehydration device 18 for spraying an acidic medium into the dehydration device 18;

[0117] The coarse ash oxidation reactor 8 is provided with a first electric stirrer 82, a first water supply pipe 84, a first regulating pipe 85 and a first gas outlet 84 are provided on the top, and a first gas delivery pipe 81 is provided on the bottom;

[0118] The fine ash oxidation reactor 9 is provided with a second electric stirrer 92, a second water supply pipe 94, a second regulating pipe 95 and a second gas outlet 93 are provided on the top, and a second gas delivery pipe 91 is provided on the bottom;

[0119] In this embodiment, the coarse ash oxidation reactor 8 and the fine ash oxidation reactor 9 share the same side wall, and a certain number of heating resistors 10 are laid on the inner wall surfaces of the coarse ash oxidation reactor 8 and the fine ash oxidation reactor 9 respectively;

[0120] The target flue gas 1 pipeline is also connected to one end of the first gas delivery pipe 81 and the second gas delivery pipe 91 via a butterfly valve 21;

[0121] The coarse ash oxidation reactor 8 and the fine ash oxidation reactor 9 are respectively provided with a first aeration device and a second aeration device at the bottom air inlet position, and the other ends of the first gas delivery pipe 81 and the second gas delivery pipe 91 are respectively connected to the first aeration device and the second aeration device; the heating device is used to heat the coarse ash oxidation reactor 8 and the fine ash oxidation reactor 9.

[0122] In this embodiment, the desulfurization tower 2 is a circulating fluidized bed (CFB) desulfurization tower commonly used in the art. A certain number of Venturi tube accelerators are arranged inside the desulfurization tower 2. The target flue gas 1 and the desulfurizer are accelerated by the Venturi to complete desulfurization in the desulfurization tower 2.

[0123] Example 3

[0124] This embodiment provides a process for efficiently oxidizing calcium-based semi-dry desulfurization ash and preparing gypsum, which is implemented using the system for efficiently oxidizing calcium-based semi-dry desulfurization ash and preparing gypsum provided in Example 1. The process includes the following specific steps:

[0125] (1) The target flue gas 1 from the main exhaust fan enters the desulfurization tower from the bottom of the desulfurization tower through the pipeline. In the desulfurization tower, it is accelerated by the venturi tube accelerator and the target flue gas and desulfurizer are sent to the desulfurization reaction zone. Under the action of the target flue gas and gravity, the desulfurizer repeatedly moves up and down irregularly in the desulfurization reaction zone so that the target flue gas and the desulfurizer are fully in contact and a desulfurization reaction occurs, thereby removing sulfur dioxide from the flue gas. At the same time, the treated flue gas is discharged from the top of the desulfurization tower. A part of the large particles, namely, coarse ash, flows out from the bottom of the desulfurization tower and is transported to the coarse ash storage tank through the pipeline. Another part of the fine ash particles enters the downstream bag filter through the pipeline along with the treated flue gas. After the treated flue gas is dust-removed in the bag filter, it enters the downstream for post-processing or is sent to the chimney and discharged outdoors. The fine ash particles collected by the bag filter, namely, fine ash, enter the fine ash storage tank;

[0126] (2) The coarse ash and fine ash stored in the coarse ash storage tank and the fine ash storage tank are transported to the coarse ash oxidation reactor and the fine ash oxidation reactor respectively, and the water supply pipes and electric stirrers of the two reactors are opened at the same time; dilute sulfuric acid is added to the two reactors through the regulating pipe to maintain the pH value of the solution in the reactor at about 4-5; after adjusting the pH value of the solution, MnO2 catalyst is added to the solution in the two reactors through the regulating pipe, and its concentration is controlled at 0.0008-0.001 mol / L; at the same time, a mixed gas of target flue gas 1 and oxygen is introduced into the bottom of the two reactors respectively, and the mixed gas enters the reactor from the bottom of the reactor through the aeration device, and the oxygen content inside the solution in the reactor is made to be above 20v%; the heating resistor is operated to heat the solutions in the two reactors so that their temperatures are both greater than 300°C. Under these conditions, the coarse ash and fine ash undergo oxidation reactions, wherein, The oxidation reaction time in the coarse ash oxidation reactor is 60-90 minutes, and the oxidation reaction time in the fine ash oxidation reactor is 40-60 minutes. After the oxidation reaction is completed, limestone slurry is obtained;

[0127] (3) The limestone slurry obtained from the coarse ash oxidation reactor and the fine ash oxidation reactor is respectively fed into a dehydration device through a first slurry delivery pipe and a second slurry delivery pipe via a first slurry delivery pump and a second slurry delivery pump. At the same time, hydrochloric acid is sprayed into the dehydration device through an acid spraying pipe to perform acid washing on the limestone slurry during dehydration, thereby removing heavy metals. After the dehydration and acid washing treatments are completed, a finished gypsum is obtained, and the finished gypsum is transported to a gypsum storage tank through a discharge pipe for storage.

[0128] Example 4

[0129] This embodiment provides a process for efficiently oxidizing calcium-based semi-dry desulfurization ash and preparing gypsum, which is implemented using the system for efficiently oxidizing calcium-based semi-dry desulfurization ash and preparing gypsum provided in Example 2. The process includes the following specific steps:

[0130] (1) The target flue gas from the main exhaust fan enters the desulfurization tower from the bottom of the desulfurization tower through the pipeline. In the desulfurization tower, the target flue gas and the desulfurizer are accelerated by the venturi tube accelerator, and are sent to the desulfurization reaction zone. Under the action of the target flue gas and gravity, the desulfurizer repeatedly moves up and down irregularly in the desulfurization reaction zone, so that the target flue gas and the desulfurizer are fully in contact and a desulfurization reaction occurs, thereby removing sulfur dioxide from the flue gas. At the same time, the treated flue gas is discharged from the top of the desulfurization tower, and a part of the large particles, namely coarse ash, flows out from the bottom of the desulfurization tower, and the other part of the fine ash particles enter the downstream bag dust collector through the pipeline with the treated flue gas. After the treated flue gas is dust-removed in the bag dust collector, it enters the downstream for post-processing or is sent to the chimney and discharged outdoors, and the fine ash particles, namely fine ash, are collected from the bottom of the bag dust collector;

[0131] (2) mixing the coarse ash and the fine ash and separating them in a vibrating screen to obtain coarse ash and fine ash, wherein the particle size of the coarse ash is greater than 0.15 mm and the particle size of the fine ash is less than 0.15 mm; and then transporting the coarse ash and the fine ash to a coarse ash storage tank and a fine ash storage tank respectively through a pipeline;

[0132] (3) The coarse ash and fine ash stored in the coarse ash storage tank and the fine ash storage tank are transported to the coarse ash oxidation reactor and the fine ash oxidation reactor respectively, and the water supply pipes and electric stirrers of the two reactors are opened at the same time; dilute sulfuric acid is added to the two reactors through the regulating pipe to maintain the pH value of the solution in the reactor at about 4-5; after adjusting the pH value of the solution, MnO2 catalyst is added to the solution in the two reactors through the regulating pipe, and the concentration thereof is controlled at 0.0008-0.001 mol / L; at the same time, a mixed gas of target flue gas 1 and oxygen is introduced into the bottom of the two reactors respectively, and the mixed gas enters the reactor from the bottom of the reactor through the aeration device. and ensuring that the oxygen content of the solution in the reactor is greater than 20v%; operating the heating resistor to heat the solutions in the two reactors to a temperature greater than 300°C. Under these conditions, oxidation reactions of the coarse ash and the fine ash occur separately. The oxidation reaction time in the coarse ash oxidation reactor is 60-90 minutes, and the oxidation reaction time in the fine ash oxidation reactor is 40-60 minutes. After the oxidation reaction is completed, a limestone slurry is obtained.

[0133] (4) The limestone slurry obtained from the coarse ash oxidation reactor and the fine ash oxidation reactor is respectively fed into a dehydration device through a first slurry delivery pipe and a second slurry delivery pipe via a first slurry delivery pump and a second slurry delivery pump. At the same time, hydrochloric acid is sprayed into the dehydration device through an acid spraying pipe to perform acid washing treatment on the limestone slurry during dehydration, thereby removing heavy metals. After the dehydration and acid washing treatments are completed, a finished gypsum is obtained, and the finished gypsum is transported to a gypsum storage tank through a discharge pipe for storage.

[0134] Comparative Example 1

[0135] This comparative example provides a process for oxidizing calcium-based semi-dry desulfurization ash and preparing gypsum, which differs from Example 3 only in that:

[0136] In step (3), the limestone slurry is not subjected to acid washing treatment while being dehydrated.

[0137] By comparing the finished gypsum obtained in Example 3 and this comparative example, it can be seen that, compared with the finished gypsum obtained in this comparative example, the quality of the finished gypsum obtained in Example 3 after the limestone slurry is acid-washed while being dehydrated can be improved by about 10%.

[0138] Comparative Example 2

[0139] This comparative example provides a process for oxidizing calcium-based semi-dry desulfurization ash and preparing gypsum, which differs from Example 3 only in that:

[0140] In step (2), the coarse ash oxidation reactor and the fine ash oxidation reactor are not heated, that is, the coarse ash oxidation reaction and the fine ash oxidation reaction in the coarse ash oxidation reactor and the fine ash oxidation reactor are carried out without heating. In this case, the oxidation reaction time in the coarse ash oxidation reactor is 130-200 minutes, and the oxidation reaction time in the fine ash oxidation reactor is 90-140 minutes.

[0141] By comparing the experimental data in Example 3 and Comparative Example 2, it can be seen that compared with the operation without heating the coarse ash oxidation reactor and the fine ash oxidation reactor, the coarse ash oxidation reactor and the fine ash oxidation reactor are heated in Example 3, so that the coarse ash oxidation reaction and the fine ash oxidation reaction in the coarse ash oxidation reactor and the fine ash oxidation reactor are carried out under heating conditions, which can increase the operating cycle by about 50%, that is, reduce the oxidation reaction time by about 50%.

[0142] Comparative Example 3

[0143] This comparative example provides a process for oxidizing calcium-based semi-dry desulfurization ash and preparing gypsum, which differs from Example 3 only in that:

[0144] In step (2), the coarse ash and fine ash stored in the coarse ash storage tank and the fine ash storage tank are simultaneously transported to the same oxidation reactor, where the coarse ash and fine ash are simultaneously oxidized. In this case, the oxidation time is 62.5-94 minutes.

[0145] By comparing the experimental data in Example 3 and Comparative Example 3 and the finished gypsums obtained by the two, it can be seen that compared with Comparative Example 3, in Example 3 of the present invention, the calcium-based semi-dry desulfurization ash is classified and then efficiently oxidized, which can improve the quality of the obtained finished gypsum by about 10% and shorten the operation cycle by about 4%.

[0146] Comparative Example 4

[0147] This comparative example provides a process for oxidizing calcium-based semi-dry desulfurization ash and preparing gypsum, which differs from Example 3 only in that:

[0148] In step (3), flue gas with a temperature of about 120° C. is introduced into the coarse ash oxidation reactor and the fine ash oxidation reactor respectively to heat them. The coarse ash oxidation reactor and the fine ash oxidation reactor can be heated to about 150° C. respectively. Under this condition, the coarse ash and the fine ash undergo oxidation reactions respectively, wherein the oxidation reaction time in the coarse ash oxidation reactor is 180-250 min, and the oxidation reaction time in the fine ash oxidation reactor is 130-150 min.

[0149] By comparing the experimental data of Example 3 and Comparative Example 4, it can be seen that in this comparative example, the coarse ash oxidation reactor and the fine ash oxidation reactor are heated by introducing flue gas into the two oxidation reactors respectively. The temperature of the oxidation reaction is low, and a high oxidation rate cannot be achieved in a short time, resulting in a longer reaction time. Compared with Example 3, the operation cycle in Comparative Example 4 is significantly longer.

[0150] In summary, the process and system for the efficient oxidation of calcium-based semi-dry desulfurization ash and preparation of gypsum provided in the embodiments of the present invention heat the coarse ash oxidation reactor and the fine ash oxidation reactor respectively so that the oxidation reactions of the coarse ash and the fine ash are carried out under heating conditions, which is beneficial to improving the operation cycle, and the coarse ash and fine ash generated by the flue gas desulfurization and dust removal device are oxidized separately in the coarse ash oxidation reactor and the fine ash oxidation reactor respectively, which is beneficial to controlling the oxidation reaction time of calcium-based semi-dry desulfurization ash with different particle sizes, which can further improve the operation cycle and, to a certain extent, can better improve the quality of the finished gypsum.

[0151] The process and system for efficiently oxidizing calcium-based semi-dry desulfurization ash and preparing gypsum provided in the embodiments of the present invention classify the calcium-based semi-dry desulfurization ash and then efficiently oxidize it separately, and then prepare high-quality finished gypsum from the limestone slurry obtained by oxidation. Therefore, the present invention can realize the recycling and reuse of calcium-based semi-dry desulfurization ash, achieving the purpose of economic efficiency.

[0152] The above description is merely a specific embodiment of the present invention and should not be construed as limiting the scope of the invention. Therefore, substitutions of equivalent components, or equivalent changes and modifications made within the scope of patent protection, should still fall within the scope of this patent. Furthermore, the technical features of this invention may be freely combined with one another, with other technical inventions, and with other technical inventions.

Claims

1. A process for efficiently oxidizing calcium-based semi-dry desulfurization ash and preparing gypsum, comprising: The target flue gas is desulfurized in a desulfurization tower to obtain coarse ash and desulfurized flue gas, and the desulfurized flue gas is then dedusted in a dust collector to obtain fine ash and purified flue gas. The process is characterized in that it further comprises: (1) transporting coarse ash and fine ash to a coarse ash oxidation reactor and a fine ash oxidation reactor, respectively, then adding water and introducing oxygen-containing gas into the coarse ash oxidation reactor and the fine ash oxidation reactor, respectively, heating the coarse ash oxidation reactor and the fine ash oxidation reactor, and oxidizing the coarse ash and the fine ash under stirring conditions, respectively, to obtain limestone slurry after the oxidation is completed; (2) The limestone slurry is dehydrated in a dehydrating device to obtain gypsum.

2. The process according to claim 1, characterized in that The process further comprises: The coarse ash and the fine ash are mixed and then put into a vibrating screen for separation to obtain coarse ash particles and fine ash particles, wherein the particle size of the coarse ash particles is greater than 0.15 mm and the particle size of the fine ash particles is less than 0.15 mm; The coarse ash particles and the fine ash particles are then transported to the coarse ash oxidation reactor and the fine ash oxidation reactor respectively to be oxidized.

3. The process according to claim 1 or 2, characterized in that Step (1) further comprises: adding a pH regulator to the coarse ash oxidation reactor and the fine ash oxidation reactor respectively, so that the oxidation is carried out at a pH value of 4-5.

4. The process according to claim 1 or 2, characterized in that Step (1) further includes: adding a catalyst into the coarse ash oxidation reactor and the fine ash oxidation reactor respectively, and the concentration of the catalyst is 0.0008-0.001 mol / L.

5. The process according to claim 1 or 2, characterized in that In step (1), the oxidation is carried out at a temperature greater than 300° C. and an oxygen content in the solution greater than 20v%, the oxidation time of coarse ash is 60-90 min, and the oxidation time of fine ash is 40-60 min.

6. The process according to claim 1 or 2, characterized in that Step (2) further includes: spraying an acidic medium into the dehydration device to perform acid washing on the limestone slurry during dehydration to obtain gypsum.

7. A system for efficiently oxidizing calcium-based semi-dry desulfurization ash and preparing gypsum according to any one of claims 1 to 6, comprising a flue gas desulfurization and dust removal device, the flue gas desulfurization and dust removal device comprising a desulfurization tower and a dust collector, the purified gas outlet of the desulfurization tower being connected to the inlet of the dust collector, characterized in that: The system further comprises: a coarse ash storage tank, a fine ash storage tank, a coarse ash oxidation reactor, a fine ash oxidation reactor, a heating device, a dehydration device and a gypsum storage tank; The coarse ash outlet and fine ash outlet of the desulfurization tower and dust collector are respectively connected to the inlets of the coarse ash storage tank and the fine ash storage tank through pipelines. The outlets of the coarse ash storage tank and the fine ash storage tank are respectively connected to the inlets of the coarse ash oxidation reactor and the fine ash oxidation reactor through pipelines. The slurry outlets of the coarse ash oxidation reactor and the fine ash oxidation reactor are respectively connected to the inlet of the dehydration device through slurry conveying pipes. The outlet of the dehydration device is connected to the inlet of the gypsum storage tank through a discharge pipe. The coarse ash oxidation reactor and the fine ash oxidation reactor are respectively provided with a stirrer, a water supply pipe and a gas outlet are respectively provided on the top, and a gas delivery pipe is respectively provided on the bottom; The heating device is used to heat the coarse ash oxidation reactor and the fine ash oxidation reactor.

8. The system according to claim 7, characterized in that The system also includes a vibrating screen. The coarse ash outlet and fine ash outlet of the desulfurization tower and dust collector are connected to the inlet of the vibrating screen through pipes respectively. The coarse particle ash outlet and fine particle ash outlet of the vibrating screen are connected to the inlets of the coarse ash storage tank and the fine ash storage tank respectively through pipes.

9. The system according to claim 7 or 8, characterized in that An acid spraying pipe is provided on the top of the dehydration device for spraying acidic medium into the dehydration device.

10. The system according to claim 7 or 8, characterized in that The inner wall surfaces of the coarse ash oxidation reactor and the fine ash oxidation reactor are respectively paved with heating resistors or ceramic heating plates.

11. The system according to claim 7 or 8, characterized in that The tops of the coarse ash oxidation reactor and the fine ash oxidation reactor are respectively provided with regulating pipes.

12. The system according to claim 7 or 8, characterized in that Aeration devices are respectively provided at the bottom air inlet positions in the coarse ash oxidation reactor and the fine ash oxidation reactor, and the gas delivery pipe is connected to the aeration device.

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