Industrial incinerator flue gas purification system and purification method

Abstract

The present invention relates to a flue gas purification system and a purification method for an industrial incinerator, belonging to the technical field of industrial incineration flue gas treatment. The system comprises a waste heat boiler, a primary dry treatment unit, a quenching treatment unit and a secondary dry treatment unit. The high-temperature flue gas of the incinerator is cooled and heat is recovered by the waste heat boiler, and the flue gas is preliminarily purified by the primary dry treatment unit. The flue gas is then rapidly cooled to below 200°C by the quenching treatment unit, thereby crossing the most suitable temperature range of 500-300°C for dioxin synthesis and avoiding the re-synthesis of dioxins. At the same time, the heat of the flue gas is recovered by the by-product saturated steam. Finally, the flue gas is thoroughly purified by the secondary dry treatment unit, and heat is further recovered by the economizer. High-altitude discharge is completed under the action of an induced draft fan and a chimney. This not only effectively avoids various problems caused by water spray quenching, but also improves the efficiency of flue gas catalytic denitrification, does not consume additional energy, and maximizes the recovery of heat generated in the flue gas purification process.

Description

Technical Field

[0001] The present invention relates to the technical field of industrial incineration flue gas treatment, and in particular to a flue gas purification system and a purification method for an industrial incinerator. Background Art

[0002] Dioxins are highly toxic polychlorinated biphenyl compounds with strong carcinogenic and teratogenic effects, causing serious secondary pollution to the air, soil, and water. Dioxins are primarily derived from industrial smelting and industrial waste incineration. In industrial smelting, such as scrap copper smelting, the cooling process of high-temperature flue gas (850°C) can produce dioxins if the cooling method is not properly selected. The generation of dioxins from waste incineration can be summarized as follows:

[0003] (1) High-temperature gas-phase synthesis. Due to the low calorific value of garbage, unstable feed, and the presence of high-chlorine-containing garbage (such as PVC and medical waste) in the incinerator feed, garbage combustion is incomplete and the furnace temperature is low (below 850°C). Chlorine-containing garbage decomposes at high temperatures to produce dioxin precursors, but the precursors cannot be completely decomposed and continue to polymerize to form larger molecules and more complex structures. If dioxin synthesis catalysts such as CuCl2 and FeCl3 are mixed into the garbage, dioxins will be produced in large quantities.

[0004] (2) Low-temperature heterogeneous catalytic synthesis. If the high-temperature flue gas cannot be rapidly cooled, when the exhaust temperature is cooled to 500-300°C, the chlorinated aromatic compounds in the garbage that are difficult to decompose, such as chlorobenzene, chlorophenol or polychlorinated biphenyls (chemical structure similar to dioxins), will polymerize with the unburned carbon residue in the flue gas to form dioxins. Especially when the flue gas contains transition metal chloride catalysts such as CuCl2 and FeCl3, the probability of dioxin regeneration is greatly increased.

[0005] See also Figure 1 In the conventional flue gas treatment process of industrial waste incinerators, high-temperature flue gas is first cooled to 550°C by a waste heat boiler and then rapidly cooled to 200°C by a spray quenching tower. However, spray quenching fails to utilize the flue gas's waste heat and consumes a large amount of spray water. More seriously, water spray quenching can easily cause fly ash agglomeration in the flue gas, corrosion of the quenching tower, and fouling and clogging, impacting flue gas emissions.

[0006] For incinerators that use waste feedstock with high nitrogen content or require incineration temperatures reaching 1100°C to ensure dioxin decomposition, flue gas purification requires the use of SNCR within the waste heat boiler and low-temperature SCR catalytic denitrification after the bag filter. However, due to the high reactivity requirements of the SCR low-temperature catalyst, the flue gas must be heated to approximately 250°C for the SCR to react effectively, which consumes additional fuel gas and increases the operating costs of the hazardous waste incinerator.

[0007] Furthermore, for waste incinerators with high halogen or sulfur content, conventional flue gas purification requires a primary dry deacidification (semi-dry tower) followed by an alkaline wet scrubber to ensure acceptable acid gas emissions. This inevitably introduces difficult-to-treat industrial wastewater, another shortcoming of conventional industrial incinerator flue gas purification.

[0008] In response to the problem that conventional industrial incinerator flue gas rapid cooling cannot utilize waste heat, subsequent industrial incinerator manufacturers and related companies have also proposed several methods for flue gas rapid cooling and utilization of waste heat:

[0009] Chinese patent CN110433643A discloses a highly efficient, energy-saving, and environmentally friendly quenching tower. High-temperature flue gas enters the bottom of the quenching tower laterally through a Venturi tube, and then flows upward through a waste heat recovery tower. The waste heat recovery tower has a waste heat recovery tube bundle on its outer wall to recover part of the waste heat of the flue gas, but a quenching spray head is still provided on its top.

[0010] However, it's clear that the high-temperature flue gas passes through the waste heat recovery tower's cavity, and the limited outer tube bundles don't allow for efficient and economical recovery of waste heat. Furthermore, the water droplets sprayed on the top of the quench tower inevitably adhere to the fly ash at the bottom, making it difficult to discharge and affecting equipment operation. Therefore, this patent differs little from conventional spray quench towers.

[0011] Chinese patent CN108006686A discloses a quenching waste heat boiler, comprising a flue gas inlet pipe, a combustion settling chamber, a quenching heat exchanger and a flue gas outlet pipe connected in sequence along the direction of flue gas flow. The quenching heat exchanger is vertically connected to the top of the combustion settling chamber. The flue gas inlet pipe is arranged on the same side as the quenching heat exchanger relative to the combustion settling chamber. The quenching heat exchanger is provided with at least one Laval nozzle at the bottom connected to the combustion settling chamber for evenly distributing the flue gas.

[0012] Similar to Chinese patent CN110433643A, the actual high-temperature flue gas flows through a hollow cylinder without heat exchange tubes, and only an upward-slanting cooling water pipe is provided on the outer wall of the cylinder. The cooling water pipe not only does not generate steam, but also makes it difficult to effectively utilize the waste heat of the high-temperature flue gas and the rapid cooling effect is difficult to ensure.

[0013] See also Figure 2 As shown in the 2017 issue 5 (total issue 416) of the industrial journal Energy Conservation, a flue gas rapid cooling device using a heat pipe heat exchanger was introduced to suppress dioxin formation. Tests showed that using this heat pipe heat exchanger, the flue gas temperature dropped from 600°C to 200°C in 1.35 seconds. However, heat pipe heat exchangers are limited to an arrangement where the cooling medium flows inside the tubes and the high-temperature flue gas flows outside. The heat transfer coefficient on the high-temperature flue gas side is low, and even the use of finned tubes offers little benefit. This makes rapid cooling of the flue gas to suppress dioxin formation very unfavorable.

[0014] See also Figure 3As shown, Chinese patent CN102492456B discloses a quench heat exchanger for an ethylene cracking furnace, wherein the high temperature cracking gas flows through the tube side, and the heat exchanger shell is divided into two shell sides by a tube sheet ( Figure 3 13 and 14), the first shell side uses high-pressure boiler water to generate high-pressure steam, and the second shell side uses boiler feed water.

[0015] However, the arrangement of the two-section shell and one bundle of tubes of the quench heat exchanger does not take into account the volume shrinkage problem caused by the rapid cooling of the cracked gas. The cracked gas flow rates in the two sections of the tubes are extremely different, making it difficult to ensure that the cracked gas reaches the necessary flow rate in the second section of the shell and tube bundle, thereby making it difficult to ensure the heat transfer coefficient on the gas side in the second section of the shell and the required quenching efficiency.

[0016] Therefore, the above-mentioned improvement method actually fails to solve the contradiction between rapid cooling of flue gas to jump over the sensitive temperature zone of dioxin formation and taking into account the required high heat transfer coefficient and necessary heat transfer area on the flue gas side to achieve waste heat recovery.

[0017] In addition, there are two problems with the flue gas purification of conventional industrial incinerators: the low-temperature SCR is set after the bag filter, and additional gas heating or steam heating is required to raise the flue gas temperature to the temperature required for the SCR catalytic reaction; secondly, the first-stage dry deacidification (semi-dry tower) + alkaline wet deacidification produces a large amount of discharged wastewater. This type of wastewater may dissolve fine powder and heavy metal chlorides that adsorb dioxins, and is more difficult to treat than a small amount of fine powder that only adsorbs dioxins and heavy metal chlorides. Summary of the Invention

[0018] In order to overcome the shortcomings of the existing technology, the present invention provides a flue gas purification system and purification method for an industrial incinerator. After the high-temperature flue gas from the incinerator is cooled to below 560°C through a waste heat boiler, the flue gas is purified through a primary dry treatment unit, a quenching treatment unit, and a secondary dry treatment unit. This not only effectively limits the synthesis of dioxins, but also improves the efficiency of catalytic denitrification of the flue gas, while effectively recovering heat energy, making it more environmentally friendly.

[0019] The technical solution to achieve the above purpose is:

[0020] The present invention provides a flue gas purification system for an industrial incinerator, comprising a waste heat boiler, which cools the high-temperature flue gas of the incinerator to below 560°C and recovers heat, and further comprising a primary dry treatment unit, a quenching treatment unit, and a secondary dry treatment unit located downstream of the waste heat boiler for sequential processing;

[0021] The primary dry treatment unit includes a primary dry deacidification mixer, a primary dry dust collector, and a medium- and high-temperature SCR reactor connected in sequence. The unit is used to remove dust that may adsorb heavy metals from flue gas cooled to less than 560°C, remove excess dry powder deacidification agent, and reduce NOx in the flue gas. The flue gas is then cooled to ~550°C, eliminating the need for a flue gas heater required in a conventional low-temperature SCR reactor, improving the efficiency of flue gas catalytic denitrification, and consuming no additional energy.

[0022] The quenching treatment unit includes a quenching boiler to quickly cool the flue gas to 200°C to prevent the re-synthesis of dioxins. The quenching boiler is an integrated shell and tube heat exchanger with upper and lower sections, including an upper heat exchanger, a lower heat exchanger, and a connecting cylinder connecting the upper and lower heat exchangers.

[0023] The secondary dry treatment unit includes a secondary dry deacidification reactor and a secondary dry dust collector connected in sequence. The downstream of the secondary dry dust collector is connected in sequence to an economizer, an induced draft fan and a chimney. After the flue gas is further purified and the heat is recovered, it is discharged to the sky through the induced draft fan and the chimney. The economizer, quenching boiler and waste heat boiler constitute a complete flue gas waste heat recovery system.

[0024] Furthermore, the first-stage dry deacidification mixer is a pipeline mixer, and the deacidifying agent in the first-stage dry deacidification mixer is CaO dry powder or Ca(OH)2 slurry.

[0025] Furthermore, the primary dry dust collector is a ceramic filter or a cyclone separator, which is used to separate the dust adsorbing heavy metals and the excess deacidifying agent in the flue gas.

[0026] Furthermore, an upper end cap is provided at one end of the upper heat exchanger away from the connecting cylinder, and the upper end cap is provided with a flue gas inlet. The upper heat exchanger includes an upper cylinder and upper tube sheets fixedly provided at both ends of the upper cylinder, and an upper heat exchanger tube bundle connecting the upper end cap and the connecting cylinder is provided between the upper tube sheets at both ends. The upper heat exchanger tube bundle is composed of a plurality of evenly distributed upper heat exchange tubes, and the upper cylinder is provided with a saturated boiler water inlet and a saturated steam and boiler water outlet.

[0027] The lower heat exchanger is provided with a lower head at one end away from the connecting cylinder, and the lower head is provided with a flue gas outlet. The lower heat exchanger includes a lower cylinder and lower tube sheets fixedly provided at both ends of the lower cylinder, and a lower heat exchanger tube bundle is provided between the lower tube sheets at both ends to connect the connecting cylinder and the lower head. The lower heat exchanger tube bundle is composed of a plurality of evenly distributed lower heat exchange tubes, the number of the lower heat exchange tubes being less than the number of the upper heat exchange tubes, and the lower cylinder is provided with a boiler water supply inlet and a boiler water supply outlet after preheating;

[0028] The flue gas enters the connecting cylinder from the flue gas inlet through the upper heat exchange tube, is redistributed in the connecting cylinder, and then flows out from the flue gas outlet through the lower heat exchange tube. The saturated boiler water and the supplementary boiler water respectively go through the shell side of the upper heat exchanger and the lower heat exchanger to complete the rapid cooling of the flue gas, generate saturated steam, and recover heat.

[0029] Furthermore, the upper heat exchange tube and the lower heat exchange tube have the same diameter, which facilitates the production or procurement of the upper heat exchange tube and the lower heat exchange tube. The ratio of the number of the upper heat exchange tube to the lower heat exchange tube is 1.2 to 1.8:1, so that after the flue gas is rapidly cooled through the upper heat exchanger, it can maintain a higher flow rate in the lower heat exchange tube of the lower heat exchanger, thereby shortening the overall time of rapid cooling of the flue gas.

[0030] Furthermore, the top ends of the upper and lower heat exchange tubes are both sheathed with wear-resistant sleeves to protect the upper and lower heat exchange tubes and increase their service life, and the upper and lower heat exchange tubes are both embedded with internal fins or deflectors to enhance the heat transfer coefficient on the flue gas side of the tubes.

[0031] Furthermore, the upper tube sheet is a flexible tube sheet, and a refractory castable is cast on the side of the upper tube sheet close to the upper head and close to the flue gas inlet, and the lower tube sheet is a flexible tube sheet or a fixed tube sheet.

[0032] Furthermore, the sum of the thicknesses of the upper tube plate and the refractory castable is 10 to 40 mm, preferably 20 to 30 mm.

[0033] Furthermore, the secondary dry deacidification reactor is a semi-dry tower, and the secondary dry dust collector is a bag dust collector. The semi-dry tower is sprayed with activated carbon and powdered baking soda or slaked lime. The activated carbon adsorbs possible small amounts of dioxins in the flue gas, and the powdered baking soda or slaked lime further removes acidic gases in the flue gas. Excess baking soda or slaked lime in the semi-dry tower and activated carbon adsorbed with dioxins are filtered and intercepted by the bag dust collector.

[0034] The present invention also provides a flue gas purification method using the above flue gas purification system, comprising the following steps:

[0035] S1, cools the high-temperature flue gas from the industrial incinerator to below 560°C through a waste heat boiler and recovers the heat;

[0036] In S2, the cooled flue gas passes through a primary dry deacidification mixer, a primary dry dust collector, and a medium- and high-temperature SCR reactor in sequence to remove dust that may adsorb heavy metals in the flue gas, excess dry powder deacidification agent, and reduce NOx in the flue gas;

[0037] S3, the flue gas is cooled to less than 200°C within 1 second through a quenching boiler, while saturated steam of 0.5-2.0 MPaG is produced as a by-product to recover the heat of the flue gas;

[0038] S4, the flue gas after cooling again passes through the secondary dry deacidification reactor, the secondary dry dust collector and the economizer to further purify the flue gas and preheat the boiler feed water;

[0039] S5, the purified flue gas is discharged to high altitude through the induced draft fan and chimney.

[0040] Furthermore, in step S3, the flow rate of the flue gas in the upper heat exchanger and the lower heat exchanger of the quenching boiler is controlled to be 10 to 20 m / s, so that the flue gas can be quickly quenched (<1.0s), achieving the same effect as spray quenching, but avoiding problems such as equipment scaling and corrosion caused by spray quenching.

[0041] Beneficial effect: Compared with the prior art, the present invention is different in that the flue gas purification system and purification method of the industrial incinerator provided by the present invention include a waste heat boiler, a primary dry treatment unit, a quenching treatment unit and a secondary dry treatment unit. The high-temperature flue gas of the incinerator is cooled and heat is recovered by the waste heat boiler, and the flue gas is preliminarily purified by the primary dry treatment unit to reduce the probability of dioxin formation. The medium and high temperature SCR reactor partially catalytically decomposes possible dioxin precursors in the flue gas, and then the flue gas is rapidly cooled to less than 200°C by the quenching treatment unit, thereby crossing the most suitable temperature range of 500-300°C for dioxin synthesis, avoiding the re-synthesis of dioxins. The by-product saturated steam is used to recover the heat of the flue gas, and finally the flue gas is thoroughly purified through the secondary dry treatment unit, and the heat is further recovered through the economizer. The high-altitude discharge is completed under the action of the induced draft fan and the chimney. The flue gas purification system and purification method of this industrial incinerator effectively avoid the various problems caused by water spray rapid cooling. The efficiency of flue gas catalytic denitrification is improved by setting a medium and high temperature SCR reactor before rapid cooling without consuming additional energy. At the same time, the complete flue gas waste heat recovery system is composed of the waste heat boiler, rapid cooling treatment unit and economizer, which maximizes the recovery of the heat generated in the flue gas purification process and reduces the operating cost of the flue gas purification. It is a green and energy-saving flue gas purification technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a flow chart of flue gas treatment for conventional industrial waste incinerators in the prior art.

[0043] Figure 2 This is a schematic diagram of a prior art rapid cooling device for cooling flue gas to inhibit dioxins.

[0044] Figure 3 The figure is a schematic structural diagram of a quench heat exchanger for an ethylene cracking furnace in the prior art.

[0045] Figure 4 This is a flow chart of a flue gas purification system for an industrial incinerator according to a preferred embodiment of the present application.

[0046] Figure 5 This is a schematic diagram of the structure of the quenching boiler in this application.

[0047] Figure 6 This is a schematic diagram of the distribution of the upper heat exchange tube bundle in the quench boiler in this application.

[0048] Figure 7 This is a schematic diagram of the distribution of the upper heat exchange tubes in this application.

[0049] Figure 8 This is a schematic diagram of the distribution of the lower heat exchange tubes in this application.

[0050] Among them, 1-waste heat boiler, 2-first-stage dry deacidification mixer, 3-first-stage dry dust collector, 4-medium and high temperature SCR reactor, 5-quenching boiler, 11-upper heat exchanger, 111-upper head, 112-flue gas inlet, 113-upper cylinder, 114-upper tube sheet, 115-upper heat exchanger tube bundle, 116-upper heat exchange tube, 117-saturated boiler water inlet, 118-saturated steam and boiler water outlet Port, 12-connecting cylinder, 13-lower heat exchanger, 131-lower head, 132-flue gas outlet, 133-lower cylinder, 134-lower tube sheet, 135-lower heat exchanger tube bundle, 136-lower heat exchange tube, 137-boiler feed water inlet, 138-boiler feed water outlet after preheating, 14-refractory castable, 6-semi-dry tower, 7-bag dust collector, 8-economizer, 9-induced draft fan, 10-chimney. DETAILED DESCRIPTION

[0051] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0052] See Figure 4 and Figure 5 As shown, the present invention provides a flue gas purification system for an industrial incinerator, comprising a waste heat boiler 1, and further comprising a primary dry treatment unit, a quenching treatment unit and a secondary dry treatment unit located downstream of the waste heat boiler 1 for sequential processing;

[0053] Industrial waste DMF residue, sludge, waste resin, grinding powder, waste activated carbon and desorption condensation waste liquid are mixed and fed to the test rotary kiln incinerator and secondary combustion chamber through a screw feeder. The combustion air volume of the test rotary kiln and secondary combustion chamber is 840Nm 3 / hr;

[0054] Among them, the following chart 1 shows the feed amount and composition of solid waste and hazardous waste in the experiment:

[0055] DMF residue microdermabrasion powder sewage treatment sludge Waste resin Waste activated carbon Desorption condensate Mass flow rate, kg / hr 17.50 41.70 4.20 7.80 0.30 10.00 Heat, KW ～124.00 ～330.00 ～10.00 ～55.00 0.00 ～15.00 LHV, kcal / kg 6,090.00 6,831.00 1,760.00 6,010.00 6,831.00 2,663.00 Received base Received base Received base Received base Received base Received base All water 14.30 6.00 60.30 16.70 20.00 80.00 Ash A 5.50 1.50 11.60 10.00 0.00 0.00 Carbon C 53.70 59.50 14.00 54.00 53.70 15.00 Hydrogen 7.10 8.30 3.00 6.40 9.00 5.00 Oxygen 12.80 16.40 8.00 9.50 5.90 0.00 Nitrogen 6.40 8.30 2.20 3.20 11.20 0.00 Sulfur S 0.10 0.00 0.80 0.10 0.10 0.00 Chlorine 0.10 0.00 0.10 0.10 0.10 0.00

[0056] The high-temperature flue gas from the incinerator is cooled to below 560°C by the waste heat boiler 1, and the heat is recovered;

[0057] The first-stage dry treatment unit includes a first-stage dry deacidification mixer 2, a first-stage dry dust collector 3 and a medium-high temperature SCR reactor 4 connected in sequence, wherein

[0058] The primary dry deacidification mixer 2 is a pipeline mixer with or without mixing elements, preferably a pipeline mixer without mixing elements. The deacidification agent is CaO dry powder or Ca(OH)2 slurry, preferably CaO dry powder. Quicklime CaO dry powder is sprayed into the mixer at 0.5 kg / hr by pneumatic conveying. The carrier gas is 3.0 barg, 5 Nm 3 / hr of compressed air, CaO powder particle size of 50μm, the nozzle is inserted into the center of the mixing tube, and the injection direction is consistent with the direction of flue gas flow;

[0059] The first-stage dry dust collector 3 is a ceramic filter or a cyclone separator, preferably a ceramic filter, the filtration accuracy of the ceramic filter is 10 μm, the windward speed is 1.0 m / min, and the filtration area is 50 m 2 Within, the dust removal efficiency is 95%, and the fly ash obtained at the cone bottom is 2.7 kg / hr;

[0060] The medium and high temperature SCR reactor 4 is injected with NH3-H2O at 3.85 kg / hr (30 wt% ammonia water), and the injection carrier gas is 3.0 barg, 10 Nm 3 / hr of compressed air, the catalyst is an iron-based molecular sieve with TiO2, V2O5, and WO3 as the main active components. The catalytic reaction temperature is 300-550°C. This catalyst also catalyzes the decomposition of chlorobenzene and chlorophenol dioxin precursors. Compared with the low-temperature SCR reactor, the medium- and high-temperature SCR reactor 4 not only has a higher denitrification efficiency, but also does not require additional gas combustion or steam heating of the flue gas, saving energy and operating costs;

[0061] Table 2 shows the flue gas volume and composition at the outlet of the secondary combustion chamber of the test rotary kiln, the outlet of the waste heat boiler, the flue gas inlet, the flue gas outlet and the economizer outlet:

[0062]

[0063] The quenching treatment unit includes a quenching boiler 5 to quickly cool the flue gas to 200°C to prevent the re-synthesis of dioxins. The quenching boiler 5 is an integrated shell-and-tube heat exchanger with upper and lower sections, including an upper heat exchanger 11, a lower heat exchanger 13, and a connecting cylinder 12 connecting the upper and lower heat exchangers 11 and 13. The upper heat exchanger 11 serves as a fire-tube shell-and-tube evaporator, and the lower heat exchanger 13 serves as a fire-tube shell-and-tube economizer.

[0064] The secondary dry treatment unit includes a secondary dry deacidification reactor and a secondary dry dust collector connected in sequence, wherein the secondary dry deacidification reactor is preferably a semi-dry tower 6, and the secondary dry dust collector is preferably a bag dust collector 7. The semi-dry tower 6 is sprayed with activated carbon and powdered baking soda or slaked lime. The activated carbon adsorbs possible small amounts of dioxins in the flue gas, and the powdered baking soda or slaked lime further removes acidic gases in the flue gas. Excess baking soda or slaked lime in the semi-dry tower 6 and the activated carbon adsorbed with dioxins are filtered and intercepted by the bag dust collector 7.

[0065] The downstream of the secondary dry dust collector is connected in sequence to an economizer 8, an induced draft fan 9, and a chimney 10. After the flue gas is further purified and heat is recovered, it is discharged to the sky through the induced draft fan 9 and the chimney 10. The economizer 8, the quenching boiler 5, and the waste heat boiler 1 constitute a complete flue gas waste heat recovery system. The economizer 8 can provide saturated boiler water to the steam drum of the waste heat boiler 1, and can also provide boiler feed water to the lower heat exchanger 13 of the quenching boiler 5.

[0066] Table 3 shows the process conditions for testing the waste heat recovery system in this application:

[0067]

[0068] It can be seen from Table 3 that the waste heat recovered by the quenching boiler 5 is equivalent to 57.5% of the heat recovered by the conventional waste heat boiler, which is of great significance for the overall flue gas waste heat recovery.

[0069] As a preferred embodiment of the present application, an upper head 111 is provided at one end of the upper heat exchanger 11 away from the connecting cylinder 12, and the upper head 111 is provided with a flue gas inlet 112. The upper heat exchanger 11 includes an upper cylinder 113 and upper tube sheets 114 fixedly provided at both ends of the upper cylinder 113, and an upper heat exchanger tube bundle 115 connecting the upper head 111 and the connecting cylinder 12 is vertically provided between the upper tube sheets 114 at both ends. The upper heat exchanger tube bundle 115 is composed of a plurality of evenly distributed upper heat exchange tubes 116. The upper cylinder 113 is provided with a saturated boiler water inlet 117 and a saturated steam and boiler water outlet 118. The saturated boiler water required for the saturated boiler water inlet 117 can be replenished by the steam drum at the top of the waste heat boiler 1. The saturated boiler water produced by the saturated boiler water outlet 118 can be returned to the steam drum, and the saturated steam outlet is used to recover flue gas heat.

[0070] The lower heat exchanger 13 is provided with a lower head 131 at one end away from the connecting cylinder 12, and the lower head 131 is provided with a flue gas outlet 132. The lower heat exchanger 13 includes a lower cylinder 133 and lower tube sheets 134 fixedly provided at both ends of the lower cylinder 133, and a lower heat exchanger tube bundle 135 connecting the connecting cylinder 12 and the lower head 131 is provided between the lower tube sheets 134 at both ends. The lower heat exchanger tube bundle 135 is composed of a plurality of evenly distributed lower heat exchange tubes 136, and the number of the lower heat exchange tubes 136 is less than the number of the upper heat exchange tubes 116. The lower cylinder 133 is provided with a boiler feed water inlet 137 and a preheated boiler feed water outlet 138. The boiler feed water required by the boiler feed water inlet 137 can be replenished by the economizer 8, and the boiler water produced by the preheated boiler feed water outlet 138 can be replenished to the steam drum;

[0071] The diameter of the upper cylinder 113 on the upper heat exchanger 11 and the diameter of the lower cylinder 131 on the lower heat exchanger 13 depend on the number of their respective tube bundles and the requirements of the pipe layout. The diameters of the respective cylinders may be different. Preferably, they are integrated, segmented shells with reduced diameters to adapt to the volume flow rate of the flue gas cooling and shrinking, but keep the average flow rate of the flue gas in the upper and lower heat exchanger tubes unchanged. Specifically, the inner diameter of the upper cylinder 113 is 440mm, the outer diameter is 450mm, the cylinder length is 3358mm, and the average flow rate of the flue gas in the cylinder is 15m / s. Therefore, in the process of the flue gas passing through the upper heat exchanger 11, the flue gas temperature is rapidly cooled from 550℃ to 320℃, and the rapid cooling time is 0.22s; the inner diameter of the lower cylinder 133 is 360mm, the outer diameter is 450mm, and the cylinder length is 3358mm. The diameter of the flue gas is 370 mm, the length of the tube is 2440 mm, and the average flow rate of the flue gas in the tube is 16 m / s. Therefore, in the process of the flue gas passing through the lower heat exchanger 13, the flue gas temperature is rapidly cooled from 320°C to 200°C, and the rapid cooling time is 0.15s. In addition, the length of the connecting cylinder 12 is 1000 mm, and the time for the flue gas to pass through is only 0.07s. In summary, the flue gas passage time of the rapid cooling boiler 5 tested in this application is only 0.22+0.15+0.07=0.44s, which is much less than 1.0s. The flue gas is rapidly cooled from 550°C to 200°C, which fully meets the flue gas rapid cooling requirements of the industrial incinerator. The rapid cooling boiler 5 replaces the conventional spray rapid cooling tower, and also solves the problems of scaling and corrosion of the conventional spray rapid cooling equipment.

[0072] The number of upper heat exchange tubes 116 in the upper heat exchanger tube bundle 115 and the number of lower heat exchange tubes 136 in the lower heat exchanger tube bundle 135 depend on the flow rate of the flue gas in each fire tube and the heat exchange area of ​​each fire tube, respectively. Figures 5 to 8As shown, the ratio of the number of the upper heat exchange tubes 116 to the lower heat exchange tubes 136 is 1.2 to 1.8:1. The upper heat exchanger tube bundle 115 is composed of 57 upper heat exchange tubes 116, and the lower heat exchanger tube bundle 135 is composed of 40 lower heat exchange tubes 136. The diameters of the upper heat exchange tubes 116 and the lower heat exchange tubes 136 are both 38 mm, and the center-to-center spacing of the tubes is 47 mm. This facilitates the production or procurement of heat exchange tubes and saves costs. The heat exchange tubes are distributed in an equilateral triangle, and can also be arranged in a quadrilateral or diamond shape. No specific limitation is made here.

[0073] The flue gas enters the connecting cylinder 12 from the flue gas inlet 112 through the upper heat exchange tube 116, and is redistributed in the connecting cylinder 12 before flowing out from the flue gas outlet 132 through the lower heat exchange tube 136. The saturated boiler water and the supplementary boiler water respectively flow through the shell side of the upper heat exchanger 11 and the lower heat exchanger 13 to complete the rapid cooling of the flue gas, generate saturated steam, and recover heat.

[0074] Preferably, the top ends of the upper heat exchange tube 116 and the lower heat exchange tube 136 are both sheathed with wear-resistant sleeves to protect the upper heat exchange tube 116 and the lower heat exchange tube 136 and increase their service life, and the upper heat exchange tube 116 and the lower heat exchange tube 136 are both embedded with internal fins or deflectors to enhance the heat transfer coefficient on the flue gas side of the tube.

[0075] Preferably, the upper tube sheet 114 is a flexible tube sheet, and a refractory castable 14 is cast on the side of the upper tube sheet 114 close to the flue gas inlet 112, and the lower tube sheet 134 is a flexible tube sheet or a fixed tube sheet, more preferably a fixed tube sheet.

[0076] Preferably, the sum of the thicknesses of the upper tube plate 114 and the refractory castable 14 is 10 to 40 mm, preferably 20 to 30 mm.

[0077] The present invention also provides a flue gas purification method using the above flue gas purification system, comprising the following steps:

[0078] S1, cools the high-temperature flue gas from the industrial incinerator to below 560°C through a waste heat boiler and recovers the heat;

[0079] In S2, the cooled flue gas passes through a primary dry deacidification mixer, a primary dry dust collector, and a medium- and high-temperature SCR reactor in sequence to remove dust that may adsorb heavy metals in the flue gas, excess dry powder deacidification agent, and reduce NOx in the flue gas;

[0080] S3, the flue gas is cooled to less than 200°C within 1 second through a quenching boiler, while saturated steam of 0.5-2.0 MPaG is produced as a by-product to recover the heat of the flue gas;

[0081] S4, the flue gas after cooling again passes through the secondary dry deacidification reactor, the secondary dry dust collector and the economizer to further purify the flue gas and preheat the boiler feed water;

[0082] S5, the purified flue gas is discharged to high altitude through the induced draft fan and chimney.

[0083] Preferably, in step S3, the flow rate of the flue gas in the upper heat exchanger and the lower heat exchanger of the quenching boiler is controlled to be 10 to 20 m / s, so that the flue gas can be quickly quenched (<1.0s), achieving the same effect as spray quenching, but avoiding problems such as equipment scaling and corrosion caused by spray quenching.

[0084] The above specific implementation methods are only preferred embodiments of this creation and are not intended to limit this creation. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of this creation should be included in the scope of protection of this creation.

Claims

1. A flue gas purification system for an industrial incinerator, comprising a waste heat boiler, characterized in that: It also includes a primary dry treatment unit, a quenching treatment unit and a secondary dry treatment unit located downstream of the waste heat boiler for sequential processing; The primary dry treatment unit includes a primary dry deacidification mixer, a primary dry dust collector and a medium-high temperature SCR reactor connected in sequence; The quenching treatment unit includes a quenching boiler, which is an integrated shell and tube heat exchanger with upper and lower sections, including an upper heat exchanger, a lower heat exchanger, and a connecting cylinder connecting the upper and lower heat exchangers; The secondary dry treatment unit comprises a secondary dry deacidification reactor and a secondary dry dust collector connected in sequence, and the downstream of the secondary dry dust collector is connected in sequence to an economizer, an induced draft fan and a chimney; The first-stage dry deacidification mixer is a pipeline mixer without mixing elements. The deacidification agent is CaO dry powder, which is sprayed with quicklime CaO dry powder at 0.5 kg / hr by pneumatic conveying. The carrier gas is 3.0 barg, 5 Nm 3 / hr of compressed air, CaO powder particle size of 50μm, the nozzle is inserted into the center of the mixing tube, and the injection direction is consistent with the direction of flue gas flow; The first-stage dry dust collector is a ceramic filter with a filtration accuracy of 10 μm, a headwind speed of 1.0 m / min, and a filtration area of ​​50 m 2 Within, the dust removal efficiency is 95%, and the fly ash obtained at the cone bottom is 2.7 kg / hr; The medium- and high-temperature SCR reactor is sprayed with NH3·H2O, which is 30 wt% ammonia water at 3.85 kg / hr, and the injection carrier gas is 3.0 barg, 10 Nm 3 / hr of compressed air, the catalyst is an iron-based molecular sieve with TiO2, V2O5, and WO3 as active components, and the catalytic reaction temperature is 300-550℃; The upper heat exchanger is provided with an upper head at one end away from the connecting cylinder, and the upper head is provided with a flue gas inlet. The upper heat exchanger includes an upper cylinder and upper tube sheets sealed at both ends of the upper cylinder, and an upper heat exchanger tube bundle connecting the upper head and the connecting cylinder is provided between the upper tube sheets at both ends. The upper heat exchanger tube bundle is composed of a plurality of evenly distributed upper heat exchange tubes. The upper cylinder is provided with a saturated boiler water inlet and a saturated steam and boiler water outlet. The lower heat exchanger is provided with a lower head at one end away from the connecting cylinder, and the lower head is provided with a flue gas outlet. The lower heat exchanger includes a lower cylinder and lower tube plates sealed at both ends of the lower cylinder, and a lower heat exchanger tube bundle connecting the connecting cylinder and the lower head is provided between the lower tube plates at both ends. The lower heat exchanger tube bundle is composed of a plurality of evenly distributed lower heat exchange tubes, the number of the lower heat exchange tubes is less than the number of the upper heat exchange tubes, and the lower cylinder is provided with a boiler water supply inlet and a boiler water supply outlet after preheating.

2. The flue gas purification system for an industrial incinerator according to claim 1, characterized in that: The upper heat exchange tube and the lower heat exchange tube have the same diameter, and the ratio of the number of the upper heat exchange tube to the number of the lower heat exchange tube is 1.2 to 1.8:

1.

3. The flue gas purification system for an industrial incinerator according to claim 2, characterized in that: The top ends of the upper heat exchange tube and the lower heat exchange tube are both sheathed with wear-resistant sleeves, and the upper heat exchange tube and the lower heat exchange tube are both embedded with inner fins or deflectors.

4. The flue gas purification system for an industrial incinerator according to claim 2, characterized in that: The upper tube sheet is a flexible tube sheet, and a side of the upper tube sheet close to the upper head and close to the flue gas inlet is cast with refractory castables, and the lower tube sheet is a flexible tube sheet or a fixed tube sheet.

5. The flue gas purification system for an industrial incinerator according to claim 4, characterized in that: The total thickness of the upper tube plate and the refractory castable is 20 to 30 mm.

6. The flue gas purification system for an industrial incinerator according to claim 1, characterized in that: The secondary dry deacidification reactor is a semi-dry tower, the secondary dry dust collector is a bag dust collector, and the semi-dry tower is sprayed with activated carbon and powdered baking soda or slaked lime.

7. A flue gas purification method using the flue gas purification system according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1, cools the high-temperature flue gas from the industrial incinerator to below 560°C through a waste heat boiler and recovers the heat; In S2, the cooled flue gas passes through a primary dry deacidification mixer, a primary dry dust collector, and a medium- and high-temperature SCR reactor in sequence to remove dust that may adsorb heavy metals in the flue gas, excess dry powder deacidification agent, and reduce NOx in the flue gas; S3, the flue gas is cooled to less than 200°C within 1 second through a quenching boiler, while producing 0.5-2.0 MPaG saturated steam as a by-product; S4, the flue gas after cooling again passes through the secondary dry deacidification reactor, the secondary dry dust collector and the economizer to further purify the flue gas and preheat the boiler feed water; S5, the purified flue gas is discharged to high altitude through the induced draft fan and chimney.

8. The flue gas purification method according to claim 7, characterized in that: In step S3, the flue gas is controlled to flow into the quenching boiler. The flow rate in the upper heat exchanger and the lower heat exchanger of the furnace is 10 to 20 m / s.

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