Sulfate-containing waste liquid treatment system for acrylonitrile and acrylonitrile combination device

Abstract

The utility model provides a sulfate-containing waste liquid treatment system for acrylonitrile and a combination device thereof, which comprises at least two sets of waste liquid treatment units and a set of flue gas treatment unit, sulfate waste liquid is divided into two strands to enter the two sets of waste liquid treatment units for combustion, waste heat utilization and quenching purification; the discharged sulfur-containing flue gas is collected and enters a set of flue gas treatment unit, the sulfur-containing flue gas subjected to deep cooling, demisting and drying can be directly used for producing high-purity sulfuric acid, and a two-end and one-tail mode is adopted, so that the operation flexibility of the system is improved, and the treatment pressure is reduced. In the waste liquid treatment unit, a high-temperature reaction device adopts segmented air distribution, so that sufficient combustion of waste liquid is ensured, and SO2 loss is reduced; a special temperature field and structural design in the waste heat boiler can prevent the heat exchange device from scaling and blocking; a venturi scrubber is adopted in the quenching purification device to quench the flue gas, and a protective liquid film is formed on the contact interface of the high-temperature flue gas and a liquid phase, so that the temperature of equipment is effectively reduced, and corrosion of the high-temperature flue gas is prevented.

Description

Technical Field

[0001] The utility model relates to the technical field of recovery and treatment of sulfate-containing waste liquid, and further relates to a sulfate-containing waste liquid treatment system for acrylonitrile and a combined device thereof. Background Art

[0002] Sulfuric acid is an important inorganic strong acid that reacts with most metals. It possesses strong acidity, oxidizing properties, and wide solubility. It can be used as an acid-base neutralizing agent, catalyst, solvent, electrolyte, dehydrating agent, and sulfonating agent, among other applications. It is widely used in the petrochemical industry as a key chemical raw material. For example, in acrylonitrile complexes, sulfuric acid is used as an acid-base neutralizing agent to remove residual ammonia after the reaction; in acetone cyanohydrin-based MMA production plants, sulfuric acid is used as a raw material in the amidation reaction to produce MMA products; and in alkylation plants, sulfuric acid is used as a catalyst to produce high-octane gasoline. However, during the production process in these plants, sulfuric acid is ultimately discharged as waste liquid containing sulfuric acid (salts). To treat this waste liquid containing sulfuric acid (salts), waste acid regeneration processes are widely used in industry. These processes convert the waste liquid containing sulfuric acid (salts) into sulfuric acid raw material that can be reused in production, achieving the recycling and resource recovery of sulfuric acid. This significantly improves raw material utilization efficiency and reduces environmental pollution, offering significant environmental, social, and economic benefits, making it a green development process.

[0003] The existing waste acid regeneration device uses sulfuric acid (salt) waste liquid as raw material and produces high-concentration sulfuric acid products through high-temperature cracking, waste heat recovery, rapid cooling purification, conversion and absorption process unit operations. Since the waste liquid contains a large amount of sulfur-containing compounds, nitrogen-containing compounds, catalyst particles and metal salts, there are many problems in the operation of the device, mainly including: (1) NO at the cracking furnace outlet xExcessive and large amounts of SO2 are converted into SO3, resulting in large sulfur losses and reduced device yields; (2) There is a certain amount of catalyst particles in the sulfuric acid (salt) waste liquid, which forms metal dust after incineration in the cracking furnace and enters the waste heat recovery system. The waste heat boiler adopts the form of a fire tube boiler, and the hot flue gas flows through the tube. The metal dust in the flue gas is molten after heat exchange and cooling with the boiler water, and adheres to the inner wall of the heat exchange tube, causing scaling or clogging of the furnace tube, reducing the heat transfer efficiency. After a period of operation, manual cleaning must be performed, seriously affecting the continuous operation cycle of the waste heat boiler system; (3) The flue gas after incineration contains a large amount of SO2 and SO3, which forms a high temperature environment and acid environment in the subsequent rapid cooling purification equipment, causing serious equipment corrosion. These directly or indirectly reduce the operating efficiency of the waste acid regeneration device and cause the device to stop frequently, increasing the operating cost of the device; as an environmental protection device, the waste acid regeneration device frequently stops and directly affects the continuous operation cycle of the upstream production device, bringing huge economic losses to the enterprise. At the same time, due to the limited scale of the waste acid regeneration device, it is unable to meet the needs of centralized treatment of sulfuric acid (salt) waste liquid in the entire plant. Existing industrial production often adopts a model of supporting the construction of upstream main devices and waste acid regeneration devices, resulting in huge waste of construction costs and production costs. With the large-scale development of chemical plants, the treatment volume of sulfuric acid (salt) waste liquid has increased sharply, and the problem of limited plant scale has become increasingly prominent. How to expand the treatment capacity of a single waste acid regeneration device is also an urgent problem that needs to be solved.

[0004] Patent CN103552992A discloses a system and method for dry acid production from sulfur-containing waste liquid. The system includes a sulfur-containing waste liquid incineration device, a furnace gas treatment device, a conversion device and an absorption device. The incineration device includes an incinerator, and the furnace gas treatment device includes a waste heat boiler, an adiabatic evaporation fully enclosed pickling device, a cooling device, an electrostatic precipitator and a drying tower connected in sequence. The conversion device includes a 3+2 five-stage conversion device or a 3+1 four-stage two-stage conversion device, and the absorption device includes a first absorption tower and a second absorption tower. This process can recycle and reuse sulfuric acid (salt) waste liquid, with huge environmental and economic benefits. The process method described in this patent is basically consistent with the existing waste acid regeneration process and can produce high-concentration sulfuric acid products, but it does not solve the problems of waste heat boiler blockage, quenching equipment corrosion, and limited device scale during device operation.

[0005] Patent CN106379868A discloses a method for producing sulfuric acid by incinerating sulfur-containing waste liquid, the sulfur-containing waste liquid is sent to the incinerator for incineration, the ammonia salt, elemental sulfur, organic matter and the like in the sulfur-containing waste liquid are decomposed and oxidized at high temperature, and the flue gas containing sulfur dioxide is used to produce commercial-grade sulfuric acid, the utility model is high in heat energy utilization rate by using the high-temperature gas generated after incineration of the waste liquid, recovering waste heat by the waste heat boiler, generating steam, and the gas after temperature reduction by the waste heat boiler then enters the two-stage air preheater, the flue gas after temperature reduction enters the purification section power wave scrubber, so as to reduce fuel consumption and effectively improve the SO2 concentration of the flue gas, which is more conducive to the production of sulfuric acid, the contact method is adopted to prepare sulfuric acid, the SO2 conversion rate is high, the process flow is short, and the operation is simple. The flue gas at the outlet of the incinerator is recovered by waste heat, reduced to 450 DEG C by the two-stage air preheater, and then enters the power wave scrubber, but in the running process, the waste heat boiler and the air preheater are prone to ash accumulation and corrosion of the heat exchange tube, which cannot guarantee long-period operation of the device; at the same time, the flue gas is cooled to 450 DEG C and enters the power wave scrubber, resulting in a large amount of heat loss; the power wave scrubber is used in the quenching and purification device, and the device has the problems of large occupation and high energy consumption. Utility model content

[0006] In view of the problems of easy ash accumulation and blockage, equipment corrosion, and large SO2 loss in the existing sulfur-containing waste liquid treatment system, the utility model aims to provide a sulfur-containing waste liquid treatment system for acrylonitrile and its combined device, which adopts a "two-head and one-tail" mode, that is, two independent waste liquid treatment units and one flue gas treatment unit, the two waste liquid treatment units can be flexibly switched and supplemented each other, the operation flexibility of the equipment is improved, and the treatment pressure is dispersed, the flue gas treatment unit effectively integrates the sulfur-containing flue gas generated in the treatment process, through deep cooling, demisting and drying treatment, the sulfur-containing gas can be directly used for producing high-purity sulfuric acid, remarkable effects are achieved in the resource utilization of waste liquid, the system has the advantages of long running period and high treatment efficiency, and has a wide application prospect.

[0007] In order to achieve the above-mentioned purpose, the utility model provides the following technical scheme:

[0008] The system for treating sulphate-containing waste liquid of acrylonitrile and its combined device comprises an oxygen-rich control distributor, a waste liquid treatment unit and a flue gas treatment unit, the waste liquid treatment unit is provided with at least two sets, the multiple sets of waste liquid treatment units are arranged in parallel, and the flue gas discharged from the multiple sets of waste liquid treatment units is collected and then enters the flue gas treatment unit; the waste liquid treatment unit comprises a high-temperature reaction device, a waste heat recovery device and a quenching and purification device connected in sequence; the oxygen-rich control distributor is used for delivering mixed gas of air and oxygen to each high-temperature reaction device; the high-temperature reaction device is used for burning sulphate-containing waste liquid and oxygen-rich gas; the waste heat recovery device is used for recovering waste heat of flue gas discharged from the high-temperature reaction device; the quenching and purification device is used for cooling and washing the flue gas; the flue gas treatment unit comprises a secondary cooling device, a demisting device and an absorption drying device connected in sequence with the outlet of the quenching and purification device, and is used for secondary cooling and dewatering, demisting and water removal of purified flue gas discharged from the quenching and purification device.

[0009] In some embodiments, the high-temperature reaction device comprises a cracking furnace, a burner and multiple air supply pipes for supplying oxygen-rich gas; the cracking furnace is used for high-temperature thermal oxidation reaction of sulphate-containing waste liquid and oxygen-rich gas, the inside of the cracking furnace comprises a reduction section and an oxidation section, the reduction section is communicated with the outlet of the burner; the burner is used for mixing the oxygen-rich gas and fuel and igniting to generate flame; the multiple air supply pipes are provided in scheme one or scheme two:

[0010] The scheme one: the multiple air supply pipes comprise at least one secondary air supply pipe communicated with the burner or the reduction section and at least one tertiary air supply pipe communicated with the oxidation section, so as to supply the oxygen-rich gas to the burner or the reduction section and the oxidation section respectively;

[0011] The scheme two: the multiple air supply pipes comprise at least one primary air supply pipe communicated with the burner, at least one secondary air supply pipe communicated with the reduction section and at least one tertiary air supply pipe communicated with the oxidation section, so as to supply the oxygen-rich gas to the burner, the reduction section and the oxidation section respectively.

[0012] In some embodiments, the waste heat recovery device comprises a waste heat boiler body, a steam drum, a boiler water booster pump, and a plurality of ash removal devices; the steam drum has a boiler water inlet, a saturated water outlet, a saturated steam outlet, and a gas-liquid mixture inlet; the waste heat boiler body has, in the inlet-to-outlet direction, a radiation section, a superheating section, and an evaporation section in sequence, the waste heat boiler body of the radiation section is a cavity with a water-cooled wall tube panel on the inner wall, the inlet and outlet of the water-cooled wall tube panel are in communication with the saturated water outlet and the gas-liquid mixture inlet respectively; the superheating section and the evaporation section are both provided with light tube heat exchangers, the inlet of the light tube heat exchanger of the superheating section is connected with the saturated steam outlet, and the outlet is used for outputting superheated steam heated by high-temperature flue gas; the inlet and outlet of the light tube heat exchanger of the evaporation section are in communication with the saturated water outlet and the gas-liquid mixture inlet respectively; the ash removal devices are arranged at the waste heat boiler bodies corresponding to the radiation section, the superheating section, and the evaporation section, for removing impurities inside the waste heat boiler body.

[0013] In some embodiments, the secondary cooling device comprises a cooling tower and a cooler, the cooling tower is provided with a spraying device and a filler layer; the tower kettle of the cooling tower, the cooler, and the spraying device are connected by pipelines to re-spray the tower kettle liquid of the cooling tower after cooling.

[0014] In some embodiments, the demisting device comprises a water trap and a plurality of demisters, the plurality of demisters are in series or parallel mode; the water trap is connected with the pipelines between the demisters and the drying device.

[0015] In some embodiments, the absorption drying device comprises a drying tower, a cooling sulfuric acid circulation pipeline, and an acid storage tank and an acid cooler arranged on the cooling sulfuric acid circulation pipeline; the inlet of the drying tower is in communication with the outlet of the demisting device; the tower kettle of the drying tower is in communication with the circulation liquid inlet at the top of the drying tower through the cooling sulfuric acid circulation pipeline, the acid storage tank is used for mixing and storing the tower kettle liquid of the drying tower with high-concentration sulfuric acid, and the acid cooler is used for cooling the circulation liquid in the cooling sulfuric acid circulation pipeline.

[0016] In some embodiments, the quenching purification device includes: a Venturi scrubber, the washing spray pipeline, a quenching tower and a cooling circulation pipeline. The Venturi scrubber includes a flue gas inlet, a reduced diameter section, a throat diameter, an expanded diameter section, and a sedimentation section from top to bottom. The flue gas inlet is connected to the outlet of the waste heat recovery device; the quenching tower is provided with a gas-liquid separation section, a liquid collector, a packing layer, a spray layer and a demister from bottom to top. The gas-liquid separation section is connected to the sedimentation section through a flue gas pipe, and the liquid collector is connected to the spray layer through the cooling circulation pipeline. The cooling circulation pipeline is used to cool the spray liquid collected by the liquid collector and re-input it into the spray layer for circulating spraying; the tower kettle of the quenching tower is connected to the bottom of the Venturi scrubber through the washing spray pipeline, and is connected to the flue gas inlet and the expanded diameter section together.

[0017] In some embodiments, a buffer tank and a circulating liquid cooler are provided on the cooling circulation pipeline. The buffer tank is connected to the outlet of the liquid collector for collecting the spray liquid, and the circulating liquid cooler is used to cool the spray liquid; the overflow port of the buffer tank is connected to the bottom of the quenching tower, and the overflow port is located in the middle of the buffer tank in the vertical direction.

[0018] In some embodiments, the high-temperature reaction device further includes: an air preheater, wherein the air preheater is used to heat air at room temperature, and the inlet of the oxygen enrichment control distributor is connected to the air preheater.

[0019] In some embodiments, the system further comprises: an oxygen input device disposed between the demisting device and the drying device, for adding oxygen to the undried flue gas to adjust the molar ratio of O2 and SO2 in the flue gas.

[0020] Compared with the prior art, the system and method for resource-based treatment of sulfate-containing wastewater provided by the present invention have the following beneficial effects:

[0021] 1. The sulfate-containing waste liquid treatment system provided by the present invention adopts a "two-end and one-tail" mode, namely, two independent waste liquid treatment units and one flue gas treatment unit. The two independent waste liquid treatment units can realize flexible switching and complementarity of waste liquid treatment, thereby enhancing the operational flexibility of the device. At the same time, this design also makes the system more convenient during maintenance and overhaul, and the overall operation will not be affected by the shutdown of a single unit. The two independent waste liquid treatment systems can also disperse the treatment load, and the operating pressure of each unit is reduced, which can extend the service life of the equipment and the operating cycle of the system. A set of special flue gas treatment units serves as the "tail end" treatment link, which effectively integrates the sulfur-containing flue gas generated in the waste liquid treatment process. The sulfur-containing gas after deep cooling, demisting and drying can directly produce high-purity sulfuric acid. The "two-end and one-tail" type sulfate-containing waste liquid system has efficient and stable treatment performance, has also achieved remarkable results in optimizing the utilization of waste liquid resources, and has broad application prospects.

[0022] 2. In the waste liquid treatment unit provided by the present invention, an oxygen enrichment control distributor is used to make the distribution of air and oxygen more uniform. The concentration unevenness of the oxygen-enriched air before entering the cracking furnace is less than 0.5%. The uniform oxygen-enriched air makes the temperature field in the cracking furnace more uniform, reduces the amount of semi-coke produced by uneven combustion, thereby alleviating the difficulty of the downstream waste heat boiler in treating high-temperature ash, and reduces the probability of furnace tube adhesion, thereby improving the operating efficiency and reliability of the entire system;

[0023] 3. The high temperature reaction device provided by the utility model adopts the design of segmented air distribution to strictly control the temperature, air excess coefficient and residence time of each section in the cracking furnace, ensuring the combustion effect while effectively reducing the loss of SO2 and NO x The production of.

[0024] 4. Different from traditional fire tube boilers, the waste heat boiler provided by this utility model adopts a unique temperature field and structural design in the radiation section, superheating section, and evaporation section, which solves the problems of heat exchange tubes being easily corroded, blocked, and difficult to clean in existing devices. Combined with the boiler water forced circulation process, the equipment welding process reduces the risk of equipment corrosion. This comprehensive improvement greatly extends the equipment operation cycle and improves the economic benefits of the device.

[0025] 6. The specially designed Venturi scrubber in the rapid cooling purification device provided by the present invention solves the problems of large floor space and high energy consumption of traditional dynamic wave scrubbing equipment. At the same time, the special structural design of the Venturi scrubber enables a protective liquid film to form at the interface between the high-temperature flue gas and the liquid phase, thereby reducing the surface temperature of the equipment, preventing high-temperature flue gas corrosion, extending the equipment operation cycle, and improving the equipment durability.

[0026] 7. The sulfuric acid salt-containing waste liquid treatment system provided by the utility model, the waste liquid containing sulfuric acid (salt) is divided into two streams and introduced into two sets of independently operated waste liquid treatment units, and sequentially undergoes combustion, waste heat utilization and quenching and washing treatment, the sulfur-containing flue gas discharged by the two sets of waste liquid treatment units is introduced into a set of flue gas treatment unit after being collected, and is subjected to secondary cooling, demisting and drying treatment, and the high-sulfur and dry gas phase obtained finally can be used for producing high-purity sulfuric acid, the sulfuric acid component in the waste liquid is effectively converted, the recycling of sulfuric acid is realized, and the regeneration of resources and the improvement of value are achieved. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 The structure schematic view of the waste liquid treatment unit provided by the utility model;

[0028] Figure 2 The structure schematic view of the flue gas treatment unit provided by the utility model;

[0029] Figure 3 The structure schematic view of the high-temperature reaction device provided by the utility model;

[0030] Figure 4 The structure schematic view of the waste heat recovery device provided by the utility model;

[0031] Figure 5 The structure schematic view of the quenching and purifying device provided by the utility model;

[0032] Figure 6 The structure schematic view of one specific embodiment of the flue gas treatment unit provided by the utility model.

[0033] BRIEF DESCRIPTION OF DRAWINGS

[0034] 1 - high-temperature reaction device 1;11 - cracking furnace;110 - reduction section;111 - oxidation section;12 - combustor;13 - primary air distribution pipeline;14 - secondary air distribution pipeline;15 - tertiary air distribution pipeline;16 - atomization medium pipeline;17 - air preheating device;18 - oxygen-enriched control distributor;

[0035] 2 - waste heat recovery device;21 - waste heat boiler body;210 - radiation section;211 - superheating section;212 - evaporation section;22 - steam drum;220 - boiler water inlet;221 - saturated water outlet;222 - saturated steam outlet;223 - gas-liquid mixture inlet;23 - boiler water booster pump;24 - ash removal device;

[0036] 3 - quenching and cleaning device; 31 - venturi scrubber; 310 - flue gas inlet; 311 - reduced diameter section; 312 - throat diameter; 313 - expanded diameter section; 314 - settling section; 315 - conical bottom; 316 - flue gas duct; 32 - quenching tower; 320 - liquid collector; 321 - liquid collection pipe; 322 - packing layer; 323 - spray layer; 324 - demister; 33 - cooling circulation pipeline; 34 - buffer tank; 340 - overflow; 35 - quenching tower circulation pump; 36 - circulating liquid cooler; 37 - scrubbing spray pipeline; 38 - scrubbing booster pump;

[0037] 4 - secondary cooling device; 41 - cooling tower; 42 - cooler; 43 - cooling tower circulation pump;

[0038] 5 - demisting device; 51 - demister; 52 - water trap;

[0039] 6 - absorption and drying device; 61 - drying tower; 62 - cooling sulfuric acid circulation pipeline; 63 - acid cooler; 64 - acid storage tank;

[0040] 7 - booster fan. DETAILED DESCRIPTION

[0041] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the specific embodiments of the present application will be described below with reference to the drawings. Obviously, the drawings described below are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained from these drawings without creative labor, and other embodiments can also be obtained.

[0042] In order to make the drawing simple, only the parts related to the present application are shown in each drawing, which does not represent the actual structure of the product. In addition, in order to make the drawing simple and easy to understand, in some drawings, only one of the parts with the same structure or function is shown, or only one of them is marked. In this paper, "one" not only means "only one", but also means "more than one".

[0043] It should be further understood that the term "and / or" used in the specification and the appended claims means one or more of the associated listed terms in any combination and all possible combinations, and includes these combinations.

[0044] In this article, it is necessary to point out that unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connecting" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected, it can be mechanically connected, or it can be electrically connected, it can be directly connected, or indirectly connected through an intermediate medium, it can be the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the utility model can be understood according to the specific circumstances.

[0045] In addition, in the description of the utility model, the terms "first", "second" and the like are only used for distinguishing description, and cannot be understood as indicating or implying relative importance.

[0046] Embodiment 1

[0047] The utility model provides a kind of system for processing sulphate-containing waste liquid, as shown in Figure 1 And Figure 2 The system includes waste liquid treatment unit and flue gas treatment unit, wherein waste liquid treatment unit is at least provided with two sets, multiple waste liquid treatment units are connected in parallel, and the flue gas discharged by multiple waste liquid treatment units is collected and then enters flue gas treatment unit for processing, specifically:

[0048] Waste liquid treatment unit includes high-temperature reaction device 1, waste heat recovery device 2 and quenching purification device 3 connected in sequence, wherein high-temperature reaction device 1 is used for high-temperature thermal oxidation reaction of sulphate-containing waste liquid and oxygen-rich gas, waste heat recovery device 2 is used for waste heat recovery of flue gas discharged by high-temperature reaction device 1, and quenching purification device 3 is used for cooling and washing of flue gas, and the structure of the above unit will be specifically described as follows: Figures 1 to 6 Specifically, the structure of the above unit is described as follows:

[0049] (I) high-temperature reaction device 1

[0050] As shown in Figure 1 And Figure 3 High-temperature reaction device 1 includes cracking furnace 11, burner 12 and multiple air supply pipes for supplying oxygen-rich gas.

[0051] Cracking furnace 11 is a hollow cavity, which can be used for combustion of sulphate-containing waste liquid and oxygen-rich gas, and fuel needs to be introduced for combustion support. The inside of cracking furnace 11 is divided into reduction section 110 and oxidation section 111, and the form of cracking furnace 11 can be selected as vertical furnace, horizontal furnace or L-shaped cracking furnace 11, and the cracking furnace 11 is a negative pressure furnace, which can effectively prevent toxic gas from leaking. Burner 12 is located at the top of cracking furnace 11, for example, L-shaped cracking furnace 11 shown in the figure, vertical section is reduction section 110, and horizontal section is oxidation section 111, and burner 12 is located at the top of reduction section 110.

[0052] As shown in Figure 3As shown, the reduction section 110 is communicated with waste liquid pipelines, the waste liquid containing sulfate in the utility model includes but is not limited to ammonium sulfate waste liquid, MMA acidic water, sulfuric acid solution, alkylated waste acid and other acidic waste liquid, is communicated with the top and middle part of reduction section 110 respectively through respective waste liquid pipelines, and enters the cracking furnace 11 to carry out the reaction.

[0053] Preferably, in order to improve the combustion effect of the waste liquid containing sulfate, the atomizing device for atomizing the waste liquid containing sulfate is increased, including a plurality of atomizing medium pipelines 16, one atomizing medium pipeline 16 is arranged corresponding to each waste liquid pipeline, and the atomizing medium can be selected from steam, air, nitrogen and the like, the waste liquid containing sulfate is atomized and then input into the reduction section 110, and the atomized waste liquid has a larger surface area, which makes it more fully contact with oxygen, thereby promoting more complete and efficient combustion.

[0054] The reduction section 110 is also communicated with the outlet of the burner 12, the fuel and part of the oxygen-rich gas are mixed in the burner 12, ignition produces flame, and heat is provided for the high-temperature thermal oxidation reaction of the waste liquid containing sulfate in the reduction section.

[0055] Preferably, when the cracking furnace 11 selects a vertical furnace or an L-shaped cracking furnace 11, the burner 12 is arranged at the top of the vertical reduction section 110, and when the cracking furnace 11 selects a horizontal furnace, the burner 12 can be arranged at the furnace head position.

[0056] Further, the burner is also provided with a fuel pipeline and a lance, and the above-mentioned fuel includes but is not limited to fuel gas, fuel oil, high-calorific-value tail gas, high-calorific-value waste liquid and the like, and the fuel pipeline should be matched with the above-mentioned atomizing steam pipeline.

[0057] The above-mentioned plurality of air distribution pipelines has two schemes:

[0058] Scheme one:

[0059] The plurality of air distribution pipelines includes at least one secondary air distribution pipeline 14 communicated with the burner 12 or the reduction section and at least one tertiary air distribution pipeline 15 communicated with the oxidation section, so as to supply the oxygen-rich gas to the burner 12 or the reduction section 110 and supply the oxygen-rich gas to the oxidation section 111 respectively.

[0060] Scheme two:

[0061] The plurality of air distribution pipes include at least one primary air distribution pipe 13 communicated with the burner 12, at least one secondary air distribution pipe 14 communicated with the reduction section, and at least one tertiary air distribution pipe 15 communicated with the oxidation section, so as to supply the oxygen-enriched gas to the burner 12, the reduction section 110 and the oxidation section 111 respectively. The primary air distribution pipe 13 supplies a part of the oxygen-enriched gas into the burner 12, and the oxygen-enriched gas is mixed with the fuel to generate a flame and release a large amount of heat, so that the temperature of the reduction section 110 in the cracking furnace 11 is increased to above 900-1400°C, and the heat is provided for the high-temperature thermal oxidation reaction of the waste liquid in the reduction section 110 with the oxygen-enriched gas supplied again by the secondary air distribution pipe 14. The tertiary air distribution pipe 15 supplies a part of the oxygen-enriched gas into the oxidation section 111, so as to ensure that the organic matter in the cracking furnace 11 can be completely combusted, and the oxygen content in the flue gas at the outlet of the cracking furnace 11 is controlled.

[0062] Regardless of the first scheme or the second scheme, according to the specific circumstances, a plurality of primary air distribution pipes 13, secondary air distribution pipes 14 and tertiary air distribution pipes 15 can be considered.

[0063] It should be noted that the "primary", "secondary" and "tertiary" are only used for differentiation and description, and cannot be understood as indicating or implying relative importance.

[0064] Further, the high-temperature reaction device 1 is further provided with an air preheating device 17 and an oxygen-enriched control distributor 18. The air preheating device 17 is used to heat the air at normal temperature to 300-700°C, so as to reduce the fuel consumption of the cracking furnace 11. The heating methods include but are not limited to incinerator, electric heating and steam heating.

[0065] The oxygen-enriched control distributor 18 is connected with the air preheating device 17, so as to mix the preheated air with pure oxygen to obtain oxygen-enriched air with uniform concentration. The oxygen content of the oxygen-enriched air is 22%-75%, and the temperature of the oxygen-enriched air after mixing is 300-700°C, preferably 450-650°C.

[0066] As shown in Figure 3 When two waste liquid treatment units are arranged, one air preheating device 17 and one oxygen-enriched control distributor 18 can be shared. The outlet of the oxygen-enriched control distributor 18 is divided into two paths, which are respectively connected with the three air distribution pipes (when the second scheme of air distribution pipe is adopted) in the high-temperature reaction device 1. The oxygen-enriched air is supplied into the primary air distribution pipe 13, the secondary air distribution pipe 14 and the tertiary air distribution pipe 15 according to the set oxygen-enriched flow.

[0067] (2) Waste heat recovery device 2

[0068] As shown in Figure 4As shown, the waste heat recovery device 2 is provided in one-to-one correspondence with the cracking furnace 11, and includes a waste heat boiler body 21, a steam drum 22, and a boiler water booster pump 23. The waste heat boiler body 21 is in the form of a water tube boiler, and in the waste heat boiler body 21 in the direction from the inlet to the outlet, there are provided, in sequence, a radiation section 210, a superheating section 211, and an evaporation section 212. The steam drum 22 has a saturated water outlet 221, a saturated steam outlet 222, and a gas-liquid mixture inlet 223.

[0069] Preferably, the steam drum 22 is in a cylindrical structure and is located at the top of the waste heat boiler. The various inlets and outlets of the steam drum 22 are connected, through steam-water pipelines, to the heat exchange devices in the radiation section 210, the superheating section 211, and the evaporation section 212. The boiler water (and steam) enters the heat exchange devices in the respective sections and exchanges heat with the high-temperature flue gas. The mixture of saturated steam / water after being heated returns to the steam drum 22, where liquid-vapor separation is performed.

[0070] The steam drum 22 also has a boiler water inlet 220 through which the boiler water directly enters the steam drum 22 to provide cooling medium for the heat exchange devices in the respective sections of the waste heat boiler body 21.

[0071] The connection structure between the radiation section 210, the superheating section 211, and the evaporation section 212 and the steam drum 22 will be described below in connection with specific heat exchange devices:

[0072] The radiation section 210 is in a hollow structure, and the inner wall of the waste heat boiler body 21 where the radiation section 210 is located is provided with a water-cooled wall tube screen. The inlet and outlet of the water-cooled wall tube screen are in communication with the saturated water outlet 221 and the gas-liquid mixture inlet 223, respectively. The boiler water stored in the steam drum 22 flows into the water-cooled wall tube screen, absorbs the heat of the flue gas flowing through the radiation section 210, reduces the temperature of the flue gas, and ensures that the molten salt in the flue gas solidifies into powdery dust, preventing the molten salt from adhering to the heat exchange tubes, causing corrosion and blockage of the heat exchange tubes, and affecting the heat exchange efficiency. The boiler water after absorbing heat is converted into saturated steam, which returns to the steam drum 22 through the gas-liquid mixture inlet 223. After heat exchange, the temperature of the flue gas at the outlet of the radiation section 210 is 550-700°C.

[0073] The above-mentioned superheating section 211 and evaporation section 212 are each provided with a light tube heat exchanger. The light tube heat exchanger of the superheating section 211 is preferably in a U-shaped light tube structure. The inlet of the light tube heat exchanger is connected to the saturated steam outlet 222. The saturated steam from the steam drum 22 exchanges heat with the high-temperature flue gas, heats the saturated steam to a specific specification of superheated steam, and further reduces the temperature of the flue gas. These superheated steam is sent to a designated receiving position outside the device through the outlet. After heat exchange, the temperature of the flue gas at the outlet of the evaporation section 212 is 250-350°C.

[0074] The light pipe heat exchanger of the evaporation section 212 preferably adopts a U-shaped light pipe or finned tube structure, the inlet of the light pipe heat exchanger is communicated with the saturated water outlet 221 through the boiler water booster pump 23, and the outlet is communicated with the gas-liquid mixture inlet 223,

[0075] A part of the saturated water from the steam drum 22 is subjected to pressurization and flows into the light pipe heat exchanger of the evaporation section 212, where the saturated water exchanges heat with the flue gas, and after being heated to a gas-liquid mixed state, the saturated water returns to the steam drum 22 through the gas-liquid mixture inlet 223 for liquid-vapor separation. In the steam drum 22, the separated steam is combined with the steam returned from the radiation section 210, and then enters the superheating section 211 for superheating. Such a forced circulation mechanism ensures the flow of the boiler water inside the waste heat boiler, ensures that the fillet weld of the furnace tube in the design of the waste heat boiler is located on the outside of the furnace body, avoids the risk of acid corrosion of the fillet weld inside the furnace, and prolongs the operation cycle of the waste heat boiler.

[0076] The high-temperature flue gas from the high-temperature reaction device 1 exchanges heat with the boiler water or steam in sequence through the radiation section 210, the superheating section 211 and the evaporation section 212, and then enters the downstream quenching and purification device 3.

[0077] In some embodiments, the waste heat recovery device 2 further comprises a plurality of ash removal devices 24, which are arranged at the waste heat boiler body 21 corresponding to the radiation section 210, the superheating section 211 and the evaporation section 212, and are used for removing impurities inside the waste heat boiler body 21. The form of the ash removal device 24 includes but is not limited to shock wave blowing, steam blowing, mechanical vibration, etc., or multiple blowing devices are used simultaneously, and mechanical vibration or shock wave blowing is preferably used.

[0078] (Three) Quenching and Purification Device 3

[0079] As shown in Figure 5 , the quenching and purification device 3 is also arranged one by one corresponding to the waste heat recovery device 2, which includes a Venturi scrubber 31, a scrubbing spray pipeline 37 and a quenching device, the quenching device includes a quenching tower 32, a cooling circulation pipeline 33, a buffer tank 34 and a circulating liquid cooler 36, and specifically:

[0080] Venturi scrubber 31 includes from top to bottom flue gas inlet 310, diameter-reducing section 311, throat diameter 312, diameter-increasing section 313, settling section 314 and conical bottom 315, flue gas inlet 310 is communicated with the outlet of waste heat boiler body 21, quench tower 32 is provided with gas-liquid separation section, liquid collector 320, filler layer 322, spraying layer 323 and demister 324 from bottom to top, gas-liquid separation section is communicated with settling section 314 of venturi scrubber 31 through flue gas pipeline 316, and liquid collector 320 is a liquid collecting pan provided with a steam riser cap, flue gas rises to filler layer 322 through the steam riser cap and contacts with spraying liquid, the falling spraying liquid is collected by the liquid collecting pan and is sent into cooling circulation pipeline 33 through liquid collecting pipe 321, cooling circulation pipeline 33 is provided with buffer tank 34, quench tower circulating pump 35 and circulating liquid cooler 36, buffer tank 34 is connected with the outlet of liquid collector 320 and stores the spraying liquid collected by liquid collector 320, circulating liquid cooler 36 is used for cooling the spraying liquid, the outlet of cooling circulation pipeline 33 is communicated with spraying layer 323, and the cooled spraying liquid reenters quench tower 32 after being pressurized by quench tower circulating pump 35 to perform circulating spraying.

[0081] The tower kettle of quench tower 32 and the conical bottom 315 of venturi scrubber 31 are communicated through scrubbing spraying pipeline 37 and are communicated with flue gas inlet 310 and diameter-increasing section 313 together, the liquid phase in the tower kettle and the conical bottom 315 is used as scrubbing liquid to spray the flue gas passing through flue gas inlet 310 first, the flue gas contacts with the scrubbing liquid to form a gas-liquid contact surface liquid film, then the flue gas enters throat diameter 312 to increase the flow rate, so that the flue gas has enough kinetic energy to make the gas and liquid mix quickly and form turbulence, under the action of gas-liquid contact surface drag force, the liquid phase is atomized to form small liquid droplets to collide with the gas phase, so that the rapid cooling and washing of the quenching and purifying equipment are realized, the function of breaking the aerosol absorption of SO3 is realized, and the corrosion risk of subsequent equipment is reduced, and a certain amount of scrubbing liquid is also sprayed into diameter-increasing section 313, so that a liquid phase covering area is formed in diameter-increasing section 313 and settling section 314, and the liquid phase small droplets and the gas phase further contact and collide in the area to realize the further quenching and washing of the gas phase, then the flue gas enters the gas-liquid separation section of quench tower 32 through horizontal flue gas pipeline 316, continues to rise through filler layer 322, spraying layer 323 and finally is demisted by demister 324 and is discharged.

[0082] Preferably, the buffer tank 34 is further provided with overflow port 340 in the middle part in the vertical direction, the overflow port 340 is communicated with the tower kettle of quench tower 32, and the excessive spraying liquid in the circulating tank enters the tower kettle and enters the scrubbing spraying pipeline together with the tower kettle liquid as scrubbing liquid.

[0083] Preferably, scrubbing pressurizing pump 38 is further arranged on scrubbing spraying pipeline 37 to pressurize the scrubbing liquid.

[0084] Preferably, the washing spray pipeline 37 also communicates with the acid water treatment device, and the remaining liquid phase used for spraying flue gas is sent to the acid water treatment device for treatment.

[0085] The flue gas treatment unit comprises, in sequence, a secondary cooling device, a mist removal device and an absorption drying device connected with the outlet of the above-mentioned quenching and cleaning device, so as to perform secondary cooling and dehydration, mist removal and water removal on the cleaned flue gas discharged from the quenching and cleaning device.

[0086] (Four) Secondary cooling device 4

[0087] As shown in Figure 6 , the secondary cooling device 4 comprises a cooling tower 41, a cooler 42 and a cooling tower circulating pump 43, the cooling tower 41 is provided with a spraying device and a filler layer, when two sets of waste liquid treatment units are arranged, the cleaned flue gas discharged from the two quenching towers 32 is collected and then enters the cooling tower 41 together, the cleaned flue gas is reversely contacted with low-temperature cooling liquid in the cooling tower 41 to realize deep cooling, the circulating liquid of the cooling tower 41 is cooled to reduce the temperature of flue gas in the tower, and saturated water in the flue gas is precipitated with the reduction of temperature, thereby reducing the water content in the flue gas and realizing dehydration.

[0088] The tower kettle of the cooling tower 41, the cooler 42 and the spraying device are connected through pipelines, part of the kettle liquid (cooling liquid) of the cooling tower 41 is pressurized by the cooling tower circulating pump 43 and then sent to the cooler 42 for cooling, and then returns to the cooling tower 41 for spraying, and the other part is sent to the acid water treatment device together with the acid tower kettle liquid discharged from the above-mentioned quenching and cleaning device 3.

[0089] The above-mentioned cooler 42 also has a cooling water inlet and a cooling water return, and the cooling water continuously flows in the cold side flow channel of the cooler 42 through the inlet and the return to absorb the heat of the cooling liquid in the hot side flow channel.

[0090] (Five) Mist removal device 5

[0091] As shown in Figure 6 , the mist removal device 5 comprises a plurality of mist eliminators 51, the inlet of the mist eliminator 51 communicates with the outlet of the cooling tower 41, the outlet of the mist eliminator 51 communicates with the downstream drying device, and the plurality of mist eliminators 51 can be arranged in series or in parallel.

[0092] The mist removal device 5 further comprises a water trap 52, the gas phase pipeline of the water trap 52 communicates with the outlet of the mist eliminator 51, and by controlling the liquid level in the water trap 52, the stability of the pressure in the system is ensured.

[0093] (Six) Absorption drying device 6

[0094] As shown in Figure 6As shown, the absorption drying device 6 includes a drying tower 61, a cooling sulfuric acid circulating pipeline 62, and an acid cooler 63 and a circulating acid pump arranged on the cooling sulfuric acid circulating pipeline 62, and the acid cooler 63 can cool the circulating liquid in the cooling sulfuric acid circulating pipeline 62.

[0095] The outlet of the demisting device 5 is communicated with the inlet of the drying tower 61, and the demisted purified flue gas is sent into the drying tower 61 for water removal.

[0096] The tower kettle of the drying tower 61 is communicated through the cooling sulfuric acid circulating pipeline 62 and the circulating liquid inlet at the top of the drying tower 61, the tower kettle liquid containing sulfuric acid is cooled through the acid cooler 63 on the sulfuric acid circulating pipeline, and after being pressurized by the circulating acid pump, it returns to the drying tower 61, and is reversely contacted with the ascending purified flue gas to absorb the moisture in the purified flue gas, and the dried purified gas enters the downstream traditional conversion absorption device through the booster fan 7 for producing sulfuric acid products.

[0097] Further, the absorption drying device 6 further includes a storage tank 64 arranged on the cooling sulfuric acid circulating pipeline 62 between the tower kettle of the drying tower 61 and the acid cooler 63, and the storage tank 64 can store the tower kettle liquid of the drying tower 61, and can also mix the tower kettle liquid with the externally input high-concentration sulfuric acid.

[0098] In some embodiments, the system further includes an oxygen input device arranged between the demisting device 5 and the drying device, for adding oxygen to the undried purified flue gas to adjust the molar ratio of O2 and SO2 in the purified flue gas.

[0099] In summary, the operation process of the system is briefly described as follows:

[0100] The sulfuric acid (salt) containing waste liquid from the upstream device includes, but is not limited to, ammonium sulfate waste liquid of the acrylonitrile main device, waste acid water of the MMA device, sulfuric acid solution, and alkylation waste acid of the alkylation device.

[0101] The sulfuric acid (salt) containing waste liquid is respectively transported to two sets of independently operated waste liquid treatment units through respective waste liquid pipelines, and after being atomized by air, it enters the reduction section 110 of the cracking furnace 11. The normal temperature air is preheated by the air preheating device 17, uniformly mixed with oxygen through the oxygen control distributor to form oxygen-enriched air, and divided into primary air, secondary air and tertiary air which respectively enter the burner, the reduction section 110 and the oxidation section 111 of the cracking furnace 11. The fuel and the primary air are mixed and heated by the burner, and then enter the reduction section 110 of the cracking furnace 11 to release a large amount of heat through high-temperature thermal oxidation reaction, thereby providing heat for the reaction of the reduction section 110. The above-mentioned sulfuric acid salt containing waste liquid atomized by air is mixed with the secondary air in the reduction section 110 and undergoes cracking and high-temperature thermal oxidation reaction, thereby converting sulfur-containing, nitrogen-containing compounds and other organic matters into CO, CO2, N2, SO2, H2O, a small amount of SO3, NO xand part of the unreacted organic matter, then the flue gas enters the oxidation section 111, the unreacted organic matter and CO in the flue gas further react with the third air to generate CO2, N2, SO2, H2O, and a small amount of SO2 will react to generate SO3. By controlling the ratio of the first air, the second air and the third air, adjusting the temperature and the excess air coefficient of different regions of the cracking furnace 11, and cooperating with sufficient residence time, it can be ensured that the reaction in the cracking furnace 11 is complete, and the loss and generation of SO2 and NO x are reduced.

[0102] The main reaction equations are as follows:

[0103] Cracking reaction:

[0104] (NH 4)2 SO4→NH3+SO2+H2O

[0105] NH4HSO4→NH3+SO2+H2O

[0106] H2SO4→H2O+SO2+O2

[0107] Oxidation reaction:

[0108] SO2+O2→SO3

[0109] NH3+O2→H2O+N2+NO x

[0110] C m H n N x O y +O2→H2O+N2+NO x +CO2

[0111] The high-temperature flue gas after the reaction contains a small amount of SO3, NOx and metal salts, which directly enters the waste heat boiler for waste heat recovery. The high-temperature flue gas exchanges heat with the boiler water in the water cooling wall pipe screen in the radiation section 210, and the temperature of the flue gas is reduced to 550-700°C by the heat absorption of the boiler water, so as to ensure that the molten salt in the flue gas solidifies into powdery dust, prevent the molten salt from adhering to the heat exchange pipe and causing corrosion of the heat exchange pipe, and affect the heat exchange efficiency. Then the flue gas flows through the heat section 211 and the evaporation section 212 in turn, is further cooled, and the saturated steam is heated into medium-pressure superheated steam. The temperature of the flue gas at the outlet of the waste heat boiler is reduced to 250-350°C, so as to ensure that the temperature of the flue gas and the heat exchange pipe wall in the waste heat boiler is higher than the dew point temperature of the flue gas, preventing equipment corrosion. At the same time, according to the pressure drop of the waste heat boiler and the outlet temperature of the flue gas, regular ash removal operation is carried out to prevent corrosion of the heat exchange pipe and ensure long-period stable operation of the waste heat boiler.

[0112] The high-temperature flue gas from the outlet of the waste heat boiler firstly enters the Venturi scrubber 31 of the quenching and purifying device 3, enters from the flue gas inlet 310 of the Venturi scrubber 31, and is quenched, dusted and washed, and the aerosol is broken to absorb SO3 through the spraying of the reduced-diameter section 311 and the expanded-diameter section 313. Then, the high-temperature flue gas enters the bottom of the quenching tower 32, and is further quenched and washed by being reversely contacted with the falling spray liquid. After the demisting by the demister 324, the quenched flue gas is discharged from the top of the quenching tower 32. The kettle liquid of the quenching tower 32 is mixed with the liquid phase discharged from the conical bottom of the Venturi scrubber 31, and then is pressurized by the Venturi circulating pump. Part of the pressurized liquid phase is sprayed into the flue gas inlet 310 and the expanded-diameter section 313 of the Venturi scrubber 31 to spray the high-temperature flue gas. The remaining liquid phase of the two sets of quenching and purifying devices 3 is collected and sent to the acidic water treatment equipment for recycling.

[0113] The purified flue gas from the top of the two quenching towers 32 is collected and sent into a set of flue gas treatment unit. The purified flue gas is firstly cooled in the secondary cooling device 4, then is demisted in the demisting device 5, and then is sent into the drying and absorbing device to absorb the moisture in the purified flue gas by using high-concentration sulfuric acid. The dried purified flue gas is pressurized by the booster fan 7 and then is sent into the conversion and absorption unit to produce sulfuric acid.

[0114] Embodiment 2

[0115] Based on the embodiment 1, the utility model also provides a method for treating the waste liquid containing sulfate by using the above system. The specific structure of the above system is not repeated. The waste liquid containing sulfate from the upstream is sent into two waste liquid treatment units to generate flue gas by high-temperature heat reaction. The flue gas is quenched and washed after waste heat utilization. The purified flue gas discharged from each waste liquid treatment unit is collected and then is sent into the flue gas treatment unit to be secondarily cooled, dried and dehydrated. Finally, the purified flue gas is sent into the downstream conversion and absorption device to produce sulfuric acid. The specific steps and process parameters are as follows:

[0116] (1) Combustion reaction: air at normal temperature is heated to 300-700°C by air preheating device 17, the preheated air is uniformly mixed with oxygen in the oxygen-rich control distributor 18, the oxygen content in the oxygen-rich air entering the cracking furnace 11 is 22%-75%, then the oxygen-rich air is uniformly divided into two streams and enters two cracking furnaces 11 respectively, if scheme two of air distribution pipeline is adopted, the oxygen-rich air is divided into primary air, secondary air and tertiary air before entering each cracking furnace 11, and enters the combustor 12, the reduction section 110 and the oxidation section 111 through three air distribution pipelines, the flow ratio of the primary air, the secondary air and the tertiary air is controlled by the regulating valve on the air distribution pipeline, which is (5-8):(1-3):(1-2); if scheme one of air distribution pipeline is adopted, the oxygen-rich air is divided into secondary air and tertiary air before entering each cracking furnace 11, and enters the reduction section 110 and the oxidation section 111 through two air distribution pipelines, the flow ratio of the secondary air and the tertiary air is controlled by the regulating valve on the air distribution pipeline, which is (6-9):(1-4), and the following takes scheme two as an example:

[0117] At the same time, the fuel reacts with the primary air in the combustor 12 to generate a flame, releasing a large amount of heat, heating the reduction section 110 of the cracking furnace 11 to 900-1400°C, the sulfur-containing salt waste liquid (ammonium sulfate waste liquid of acrylonitrile device, waste acid water of MMA device, waste acid water) is input into the waste liquid treatment unit through the respective waste liquid pipeline (ammonium sulfate waste liquid pipeline, MMA waste acid water pipeline, waste acid water pipeline), atomized into small droplets, and then enters the reduction section 110 of the cracking furnace 11, uniformly mixed with the secondary air and reacts at high temperature, and the residence time of the flue gas in the reduction section 110 is 2-4s, converting the sulfur-containing, nitrogen-containing compounds and other organic matter into CO, CO2, N2, SO2, H2O, a small amount of SO3, NO x and unreacted organic matter, preferably, the above-mentioned atomized medium is generally compressed air or steam, and the liquid phase after atomization is more easily oxidized completely.

[0118] Then the flue gas enters the oxidation section 111, the unreacted organic matter and CO in the flue gas further react with the oxygen in the tertiary air to generate CO2, N2, SO2, H2O, and a small amount of SO2 will react to generate SO3, the temperature in the oxidation section 111 is 800-1200°C, preferably 900-1100°C, and the residence time of the flue gas in the oxidation section 111 is 2-6s. By controlling the flow of the tertiary air, the oxygen content in the flue gas in the oxidation section 111 is 1%-6% mol, preferably 1.2%-2.5% mol, to ensure complete reaction.

[0119] (2) Waste heat utilization: The high-temperature flue gas discharged from the oxidation section 111 directly enters the waste heat boiler body 21 in the waste heat recovery unit, and flows through the radiation section 210, the superheating section 211 and the evaporation section 212 in the waste heat boiler body 21 in sequence. A part of the boiler water in the steam drum 22 enters the water-cooled wall tube screen of the radiation section 210 to exchange heat with the high-temperature flue gas, so that the flue gas is cooled to 550-700°C. The remaining boiler water is pressurized by the boiler water booster pump 232 and then enters the light tube heat exchanger of the evaporation section 212 to exchange heat with the flue gas. The flue gas at the outlet of the waste heat boiler body 21 is reduced to 250-350°C after being cooled, and then enters the quenching and purifying device 3. The temperature of the flue gas in the waste heat boiler body 21 and the temperature of the heat exchange tube wall are higher than the dew point temperature of the flue gas, so as to prevent equipment corrosion. The gas-liquid mixture of saturated steam / water generated by the radiation section 210 and the evaporation section 212 returns to the steam drum 22 for liquid-vapor separation. The saturated steam directly enters the light tube heat exchanger of the superheating section 211 and is heated by the flue gas to medium-pressure superheated steam, which is discharged from the waste heat boiler body 21.

[0120] The arrangement of the waste heat recovery system effectively reduces the flue gas temperature and increases the economic benefit of the system. The molten metal salt in the high-temperature flue gas is fully cooled to solid powder in the radiation section 210, preventing adhesion to the outer wall of the heat exchange tube when entering the superheating section 211. At the same time, the ash removal device 24 is regularly opened to clean the metal salt adhered to the heat exchange tube from the tube wall, which can effectively prevent the deterioration of heat exchange efficiency or tube wall corrosion caused by ash accumulation, and improve the equipment operation cycle.

[0121] (3) Quenching and washing: The flue gas discharged from the waste heat boiler body 21 enters the quenching and purifying device 3, first enters the Venturi scrubber 31 from the flue gas inlet 310, and then flows through the reduced diameter section 311, the throat diameter 312, the expanded diameter section 313 and the settling section 314. At the flue gas inlet 310, the flue gas is in contact with the washing spray liquid. The ratio of the spraying amount of the washing spray liquid to the evaporation amount is 7-14, preferably 8-12, which ensures the formation of a liquid film on the gas-liquid contact surface to protect the equipment from corrosion. Subsequently, the gas phase enters the reduced diameter section 311, the flow rate is accelerated, and the flow rate reaches 35-100 m / s, preferably 45-80 m / s, at the throat diameter 312, which ensures that the flue gas has sufficient kinetic energy to rapidly mix the gas and liquid and form turbulence. Under the action of the drag force on the gas-liquid contact surface, the liquid phase is atomized to form small droplets, which collide with the gas phase to achieve rapid cooling, washing and breaking of the aerosol to absorb SO3, thereby reducing the corrosion risk of subsequent equipment.

[0122] At the same time, a certain amount of washing spray liquid is sprayed into the expanded diameter section 313, and a liquid phase coverage area is formed in the expanded diameter section 313 and the settling section 314. The liquid phase spraying density is 40-120 m 3 / (m 2 ·h), preferably 50-90 m 3 / (m 2• h) The flue gas flows into the liquid phase coverage area formed by the diameter expansion section 313 and the settling section 314, and further contacts and collides with the liquid phase droplets, further achieving the quenching and washing of the gas phase.

[0123] The flue gas then enters the lower part of the quenching tower 32 through the horizontal flue gas pipeline 316, and sequentially passes through the gas-liquid separation section, the steam cap, and the packing layer 322 from bottom to top. In the process of the flue gas fully contacting the spray liquid sprayed down by the spray layer 323 at the packing layer 322, the flue gas completes effective cooling and purification. Then, the flue gas continues to rise, passes through the mist eliminator 324 to remove residual mist droplets in the flue gas, and finally escapes from the top of the tower.

[0124] The spray liquid collected by the collecting tray is sent to the buffer tank 34 through the collecting pipe 321. Part of the spray liquid in the buffer tank 34 returns to the gas-liquid separation section through the overflow port 340, and then flows out from the tower kettle of the quenching tower 32. After mixing with the liquid phase discharged from the conical bottom 315 of the Venturi scrubber 31, the liquid phase is pressurized by the washing booster pump 38. Part of the pressurized liquid phase is sprayed into the flue gas inlet 310 of the Venturi scrubber 31, and the other part is sprayed into the diameter expansion section 313, which cools and washes the high-temperature flue gas. The remaining liquid phase is collected and sent to the acidic water treatment equipment for recycling.

[0125] The other part of the spray liquid in the buffer tank 34 is sent to the circulating liquid cooler 4236 by the quenching tower circulating pump 35, cooled to 35-50°C, and then returned to the spray layer 323 to realize circulating spraying.

[0126] (4) Secondary cooling: The purified flue gas from the top of the two quenching towers 32 is collected and then enters a set of secondary cooling device 4 for deep cooling. The purified flue gas first enters the bottom of the cooling tower 41 and is in countercurrent contact with the low-temperature cooling liquid for cooling and dewatering. The cooled purified flue gas enters the downstream mist removal device 5.

[0127] The kettle liquid (cooling liquid) of the cooling tower 41 is pressurized by the cooling tower circulating pump 43. Part of the circulating liquid is cooled to 20-40°C by the cooler 42 and then returned to the cooling tower 41. The other part of the cooling liquid is mixed with the discharged acidic water of the two sets of quenching and purification devices 3 and then sent to the acidic water treatment equipment for recycling.

[0128] (5) Mist removal: The purified flue gas after secondary cooling is mixed with a large amount of acidic small droplets and a small amount of fine dust particles, which are further removed in the mist removal device 5. The mist eliminator 51 is preferably a wet electrostatic mist eliminator 51, which is connected in parallel or series with one or more mist eliminators 51 to ensure that the removal efficiency of the acid mist and dust is ≥99.5%. Figure 2 and 6Two mist eliminators 51 are shown in series, the inlet of the first mist eliminator 51 is communicated with the outlet of the upstream cooling tower 41, the outlet of the last mist eliminator 51 is communicated with the gas phase pipeline of the seal water device 52, by controlling the liquid level in the seal water device 52, the pressure stability in the system is ensured.

[0129] (6) Absorption drying: the purified flue gas from the mist eliminator 5 is mixed with a certain amount of air at room temperature and then enters the absorption drying device 6, in the mixed gas formed by the purified flue gas and the air, the molar ratio of oxygen and SO2 is 0.8-2, preferably 0.9-1.3, which can ensure that SO2 can be completely converted into SO3 in the subsequent sulfuric acid production.

[0130] The mixed gas enters from the bottom of the drying tower 61, and 92%-98% concentrated sulfuric acid is used to absorb the water in the purified gas, so that the water content in the purified gas at the top of the tower is ≤100 mg / Nm 3 After drying, the purified gas enters the downstream traditional conversion absorption device through the booster fan 7, the molar ratio of O2 and SO2 in the purified flue gas discharged from the booster fan 7 is 0.8-2, preferably 0.9-1.3, the water content is ≤100 mg / Nm 3 , the SO2 concentration is 2.5%-14% mol, the dust content is ≤1.2 mg / Nm 3 , the acid mist concentration is <5 mg / Nm 3 , which can be used for producing 98% sulfuric acid, 100% sulfuric acid and nicotinic acid products.

[0131] The liquid in the drying tower 61 enters the acid storage tank and is mixed with a high-concentration sulfuric acid liquid to make the concentration of concentrated sulfuric acid in the acid storage tank 92%-98% wt, after being pressurized by a circulating acid pump, the concentrated sulfuric acid enters the acid cooler 63 and exchanges heat with circulating cooling water, and the concentrated sulfuric acid is cooled to 30-60°C and returned to the drying tower 61, so as to ensure the absorption efficiency of water in the flue gas, at this time, the temperature of the gas phase at the top of the drying tower 61 is ≤60°C, the temperature of the tower kettle is ≤75°C, and the difference between the acid concentration at the outlet of the tower kettle and the inlet of the circulating acid is less than 0.5% wt.

[0132] The system and method for resourceful treatment of sulfuric acid salt-containing waste liquid provided by the utility model will be further described in detail in combination with specific embodiments.

[0133] Example 3

[0134] On the basis of examples 1 and 2, in this embodiment, the ammonium sulfate waste liquid from the upstream device and the MMA waste acid water are composed as follows:

[0135] Ammonium sulfate waste liquor composition Mass fraction % MMA waste acid water composition Mass fraction % Ammonium sulfate 38.0 Sulfuric acid 17.4 Water 47.49 Water 24.0 Heavy components 14.5 Ammonium bisulfate 53.0 Acrylonitrile 0.01 Methacrylic acid 0.19 Acetonitrile 0 Acetonedicarboxylate 4.13 Methanol 0.19 Methyl methacrylate 0.75 Dimethyl ether 0.34 Mass flow kg / h 29916 Mass flow kg / h 60275

[0136] Two streams of waste liquid containing sulphate enter two sets of waste liquid treatment units in Example 1. In each set of waste liquid treatment unit, the ammonium sulphate waste liquid from the acrylonitrile unit is 14958 kg / h, the MMA waste acid water is 30137.5 kg / h, and the 98% waste sulphuric acid liquid is 2250 kg / h, which enter the top of the L-shaped cracking furnace 11 and the reduction section 110 through the ammonium sulphate waste liquid pipeline, the MMA waste acid water pipeline and the acid water pipeline respectively, the fuel is methane, which directly enters the burner at the top of the cracking furnace 11, and the atomizing medium is compressed air. The air at normal temperature is preheated to 510°C by the air preheating device 17, and then mixed with oxygen at normal temperature, the oxygen content in the mixed oxygen-enriched air is 30%, and the temperature is 450°C, which is divided into three times into the cracking furnace 11, the flow rate ratio of the primary air distribution: the secondary air distribution: the tertiary air distribution is 7:2:1, at this time, the temperature of the reduction section 110 is 1100°C, the residence time of the flue gas in the reduction section 110 is 2.2s, the temperature of the oxidation section 111 is 1065°C, and the residence time is 4.4s, the oxygen content in the flue gas is 1.5%, which ensures the complete reaction of the organic matter and reduces the generation of SO2 and NO x .

[0137] Subsequently, the flue gas enters the waste heat boiler body 21, by controlling the water inlet amount of the boiler, the steam production and the liquid level in the steam drum 22, the temperature of the flue gas after passing through the radiation section 210 is about 650°C, the flue gas temperature at the outlet of the waste heat boiler is 320°C, and 4.2MPaG, 390°C superheated steam of 98.4t / h is by-produced. The radiation section 210 of the waste heat boiler is selected to be a water-cooled wall tube screen, the superheating section 211 and the evaporation section 212 are selected to be U-shaped light tubes, and the soot blowing device 24 adopts shock wave soot blowing to prevent the equipment corrosion and the heat exchange efficiency deterioration caused by the ash deposition on the heat exchange tubes.

[0138] The flue gas at the outlet of the waste heat boiler enters the Venturi scrubber 31, the ratio of the spray amount of the circulating scrubbing liquid at the flue gas inlet 310 to the evaporation amount is controlled to be 9, the flue gas flow rate at the throat diameter 312 is 63m / s, and the liquid phase spray density in the liquid phase coverage area of the expansion section 313 and the settling section 314 is 55-82m 3 / (m 2 ·h), at this time, the flue gas temperature at the outlet of the Venturi scrubber 31 is 83°C, the flue gas enters the bottom of the quenching tower 32, and is in countercurrent contact with the spray liquid in the quenching tower 32 to realize further quenching and washing, and the temperature of the purified flue gas at the top of the quenching tower 32 is reduced to 40°C.

[0139] The purified gas at the outlets of the two sets of quenching and purification devices 3 is collected together and then enters a set of flue gas treatment unit, first enters the bottom of the cooling tower 41, is further cooled to 30°C, and then is sent to the mist removal device 5. The total amount of the acid water discharged from the two sets of quenching and purification devices 3 and the cooling device is 75t / h, which is sent to the acid water treatment equipment together for recycling.

[0140] The purified flue gas from the secondary cooling device 4 enters the electrostatic precipitator 324. The system is provided with four electrostatic precipitators 324, which are connected in series and then connected in parallel. The removal efficiency of acid mist and dust is 99.8%.

[0141] The purified gas then enters the absorption and drying device 6. The drying tower 61 uses 96%wt concentrated sulfuric acid to absorb the moisture in the purified gas. The 96%wt concentrated sulfuric acid is pressurized by a circulating acid pump and then enters the acid cooler 63 to be cooled to 50°C and returned to the drying tower 61 to absorb the moisture in the purified flue gas. At this time, the gas phase temperature at the top of the drying tower 61 is 50°C, the tower kettle temperature is 59.9°C, and the acid concentration at the tower kettle outlet is 95.6%wt. A stream of 98%wt sulfuric acid is added to the acid storage tank to mix with the kettle liquid of the drying tower 61, ensuring that the concentration of the circulating acid in the acid storage tank is 96%wt.

[0142] After the dried purified flue gas is mixed with air at room temperature, the air flow is controlled so that the molar ratio of O2 to SO2 in the mixed gas discharged by the booster fan 7 is 1, the water content is 82 mg / Nm 3 , the dust content is 1 mg / Nm 3 , and the acid mist concentration is 4 mg / Nm 3 . At this time, the SO2 concentration in the purified gas is 8.06%mol, which enters the subsequent conversion and absorption equipment, and about 400,000 tons / year of sulfuric acid (calculated as 100% sulfuric acid) can be produced.

[0143] Example 4

[0144] On the basis of Examples 1 and 2, the waste liquid containing sulfuric acid (salt) from the upstream device in this example is composed as follows:

[0145]

[0146] The three waste streams in the table are fed into two sets of waste treatment units in Example 1. In each set of waste treatment units, the ammonium sulfate waste stream from the acrylonitrile unit is 23859 kg / h, the MMA waste acid stream is 14964 kg / h, and the alkylation waste acid stream is 4115 kg / h, which are fed into the L-shaped cracking furnace 11 at the top and the reduction section 110 through the ammonium sulfate waste stream pipeline, the MMA waste acid stream pipeline, and the acid water pipeline, respectively. The fuel is methane, which is directly fed into the burner at the top of the cracking furnace 11, and the atomizing medium is compressed air. The air at room temperature is preheated to 730°C by the air preheating device 17, mixed with oxygen at room temperature, and the oxygen content in the mixed oxygen-enriched air is 50%, and the temperature is 650°C. The oxygen-enriched air is divided into three times of feeding into the cracking furnace 11, and the flow rate ratio of the primary air, the secondary air, and the tertiary air is 7:2:1. At this time, the temperature of the reduction section 110 is 1065°C, the residence time of the flue gas in the reduction section 110 is 2.5s, the temperature of the oxidation section 111 is 1065°C, and the residence time is 4.2s. The oxygen content in the flue gas is 1.5%, which ensures the complete reaction of organic matter and reduces the loss of SO2 and the generation of NO x .

[0147] Subsequently, the flue gas enters the waste heat boiler body 21, and by controlling the amount of boiler water, the amount of steam produced, and the liquid level in the steam drum 22, the temperature of the flue gas after passing through the radiation section 210 is about 650°C, the flue gas temperature at the outlet of the waste heat boiler is 315°C, and 4.2MPaG, 400°C superheated steam is produced at a rate of 73.4t / h. The radiation section 210 of the waste heat boiler is selected to be a water-cooled wall tube screen, the superheating section 211 and the evaporation section 212 are selected to be U-shaped light tubes, and the radiation section 210 of the waste heat boiler adopts mechanical rapping for ash removal, while the superheating section 211 and the evaporation section 212 both adopt shock wave blowing for ash removal, to prevent equipment corrosion and heat exchange efficiency deterioration caused by ash accumulation on the heat exchange tubes.

[0148] The flue gas at the outlet of the waste heat boiler enters the Venturi scrubber 31, and the ratio of the spray amount of the circulating scrubbing liquid to the evaporation amount at the flue gas inlet 310 is controlled to be 8.5, the flue gas flow rate at the throat diameter 312 is 61m / s, and the liquid phase spray density in the liquid phase coverage area of the expansion section 313 and the settling section 314 is 57-84m 3 / (m 2 ·h). At this time, the flue gas temperature at the outlet of the Venturi scrubber 31 is 81°C, the flue gas enters the quenching tower 32 at the bottom, and is further quenched and washed by countercurrent contact with the spray liquid in the quenching tower 32. The purified flue gas at the top of the quenching tower 32 is cooled to a temperature of 40°C.

[0149] The purified gas at the outlet of the two sets of quenching and purification devices 3 is collected and then fed into one set of flue gas treatment unit, first into the cooling tower 41 at the bottom, further cooled to 30°C, and then sent to the mist removal device 5. The total amount of acid water discharged from the two sets of quenching and purification devices 3 and the secondary cooling device 4 is 54.6t / h, which is sent to the acid water treatment equipment for recycling.

[0150] The purified gas from the secondary cooling device 4 enters the electrostatic precipitator 324, and the system is provided with four electrostatic precipitators 324, which are connected in series and then connected in parallel, and the removal efficiency of acid mist and dust is 99.8%.

[0151] Subsequently, the purified gas enters the absorption and drying device 6, and the drying tower 61 uses 93.5%wt concentrated sulfuric acid to absorb the moisture in the purified gas, and the 93.5%wt concentrated sulfuric acid is pressurized by a circulating acid pump and then enters the acid cooler 63 to cool the circulating sulfuric acid to 50°C and return to the drying tower 61 to absorb the moisture in the purified flue gas, at this time the gas phase temperature at the top of the drying tower 61 is 50°C, the tower kettle temperature is 62°C, and the acid concentration at the tower kettle outlet is 92.9%wt. A 99.2%wt sulfuric acid is supplemented in the acid storage tank and mixed with the kettle liquid of the drying tower 61 to ensure that the concentration of the circulating acid in the acid storage tank is 93.5%wt.

[0152] After the dried purified flue gas is mixed with air at room temperature, by controlling the air flow, the molar ratio of O2 to SO2 in the mixed gas discharged by the booster fan 7 is 1.1, the water content is 87mg / Nm 3 , the dust content is 1mg / Nm 3 , and the acid mist concentration is 4.3mg / Nm 3 , at this time the SO2 concentration in the purified gas is 10.6%mol, which enters the subsequent conversion and absorption equipment, and about 440,000 tons / year of sulfuric acid (calculated according to 100% sulfuric acid) can be produced.

[0153] The above is only the preferred embodiment of the present application, and it should be pointed out that for ordinary skilled persons in the technical field, some improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A sulfate-containing waste liquid treatment system for acrylonitrile and its combined device, characterized in that: include: An oxygen enrichment control distributor, a waste liquid treatment unit and a flue gas treatment unit, wherein at least two waste liquid treatment units are provided, and multiple waste liquid treatment units are arranged in parallel, and the flue gas discharged from the multiple waste liquid treatment units is collected and enters the flue gas treatment unit; The waste liquid treatment unit includes a high temperature reaction device, a waste heat recovery device and a rapid cooling purification device connected in sequence; The oxygen enrichment control distributor is used to deliver a mixed gas of air and oxygen to each of the high-temperature reaction devices respectively; The high-temperature reaction device is used to burn the sulfate-containing waste liquid with oxygen-rich gas; The waste heat recovery device is used to recover waste heat from the flue gas discharged from the high-temperature reaction device; The quenching and purification device is used to cool and wash the flue gas; The flue gas treatment unit includes a secondary cooling device, a demisting device and an absorption drying device connected in sequence to the outlet of the quenching purification device, and is used to perform secondary cooling, dehydration, demisting and dehydration on the purified flue gas discharged from the quenching purification device.

2. The sulfate-containing wastewater treatment system according to claim 1, characterized in that: The high-temperature reaction device includes a cracking furnace, a burner, and a plurality of air distribution pipelines for supplying oxygen-rich gas; The cracking furnace is used for high-temperature thermal oxidation reaction of sulfate-containing waste liquid with oxygen-rich gas. The interior of the cracking furnace includes a reduction section and an oxidation section. The reduction section is connected to the outlet of the burner. The burner is used to mix the oxygen-rich gas and fuel and ignite to generate flame; The arrangement of the plurality of air distribution pipes includes scheme 1 or scheme 2: The first solution: the plurality of air distribution pipelines include at least one secondary air distribution pipeline connected to the burner or the reduction section and at least one tertiary air distribution pipeline connected to the oxidation section, so as to supply the oxygen-rich gas to the burner or the reduction section and the oxidation section respectively; The second option: the multiple air distribution pipelines include at least one primary air distribution pipeline connected to the burner, at least one secondary air distribution pipeline connected to the reduction section, and at least one tertiary air distribution pipeline connected to the oxidation section, so as to supply the oxygen-rich gas to the burner, the reduction section and the oxidation section respectively.

3. The sulfate-containing wastewater treatment system according to claim 1, characterized in that: The waste heat recovery device includes: a waste heat boiler body, a steam drum, a boiler water booster pump and several ash cleaning devices; The steam drum has a boiler water inlet, a saturated water outlet, a saturated steam outlet, and a gas-liquid mixture inlet; The waste heat boiler body is provided with a radiation section, a superheating section and an evaporation section in sequence from the inlet to the outlet. The waste heat boiler body where the radiation section is located is a cavity with a water-cooled wall tube panel provided on the inner wall, and the inlet and outlet of the water-cooled wall tube panel are respectively connected to the saturated water outlet and the gas-liquid mixture inlet; The superheating section and the evaporation section are both provided with a bare tube heat exchanger. The inlet of the bare tube heat exchanger of the superheating section is connected to the saturated steam outlet, and the outlet is used to output superheated steam heated by the high-temperature flue gas. The inlet and outlet of the bare tube heat exchanger of the evaporation section are respectively connected to the saturated water outlet and the gas-liquid mixture inlet; The cleaning device is provided at the waste heat boiler body corresponding to the radiation section, the superheating section and the evaporation section, and is used to remove impurities inside the waste heat boiler body.

4. The sulfate-containing wastewater treatment system according to claim 1, characterized in that: The secondary cooling device includes: a cooling tower and a cooler, The cooling tower is provided with a spray device and a filler layer; The tower bottom of the cooling tower, the cooler and the spraying device are connected through pipelines, so that the tower bottom liquid of the cooling tower is cooled and then sprayed again.

5. The sulfate-containing wastewater treatment system according to claim 1, characterized in that: The demisting device includes a water sealer and a plurality of demisters, wherein the plurality of demisters are connected in series or in parallel; The water sealer is connected to the pipeline between the demister and the drying device.

6. The sulfate-containing wastewater treatment system according to claim 1, characterized in that: The absorption drying device includes a drying tower, a cooling sulfuric acid circulation pipeline, and an acid storage tank and an acid cooler arranged on the cooling sulfuric acid circulation pipeline; The inlet of the drying tower is connected to the outlet of the demisting device; The bottom of the drying tower is connected to the circulating liquid inlet at the top of the drying tower through the cooling sulfuric acid circulation pipeline. The acid storage tank is used to mix and store the bottom liquid of the drying tower with high-concentration sulfuric acid. The acid cooler is used to cool the circulating liquid in the cooling sulfuric acid circulation pipeline.

7. The sulfate-containing wastewater treatment system according to claim 1, characterized in that: The quenching and purification device includes: a venturi scrubber, the washing spray pipeline, a quenching tower and a cooling circulation pipeline. The venturi scrubber includes, from top to bottom, a flue gas inlet, a reduced diameter section, a throat diameter, an expanded diameter section, and a settling section. The flue gas inlet is connected to the outlet of the waste heat recovery device. The quenching tower is provided with a gas-liquid separation section, a liquid collector, a packing layer, a spray layer and a demister from bottom to top. The gas-liquid separation section is connected to the settling section through a flue gas duct. The liquid collector is connected to the spray layer through the cooling circulation pipeline. The cooling circulation pipeline is used to cool the spray liquid collected by the liquid collector and re-input it into the spray layer for circulating spraying. The tower kettle of the quenching tower is connected to the bottom of the venturi scrubber through the scrubbing spray pipeline, and is also connected to the flue gas inlet and the expanded diameter section.

8. The sulfate-containing wastewater treatment system according to claim 7, characterized in that: The cooling circulation pipeline is provided with a buffer tank and a circulating liquid cooler. The buffer tank is connected to the outlet of the liquid collector and is used to collect the spray liquid, and the circulating liquid cooler is used to cool the spray liquid; The overflow port of the buffer tank is communicated with the kettle of the quenching tower, and the overflow port is located in the middle of the buffer tank in the vertical direction.

9. The sulfate-containing wastewater treatment system according to claim 2, characterized in that: The high temperature reaction device further comprises: an air preheater, The air preheater is used to heat air at normal temperature, and the inlet of the oxygen enrichment control distributor is connected to the air preheater.

10. The sulfate-containing wastewater treatment system according to claim 1, characterized in that: It also includes: an oxygen input device arranged between the demisting device and the drying device, for adding oxygen to the undried flue gas to adjust the molar ratio of O2 and SO2 in the flue gas.

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