Waste incineration flue gas purification and waste heat gradient utilization system

Abstract

The invention relates to the technical field of waste incineration flue gas treatment, and discloses a waste incineration flue gas purification and waste heat gradient utilization system. The waste incineration flue gas purification and waste heat gradient utilization system comprises a waste heat boiler, a circulating type dry deacidification reaction tower, a bag-type dust collector and a flue gas waste heat recovery heat exchanger which are arranged in sequence. The circulating dry deacidification reaction tower is sequentially provided with a bottom flue gas inlet, a middle feeding section and a top flue gas outlet from bottom to top; a flue gas outlet of the waste heat boiler is connected with a bottom flue gas inlet of the circulating dry deacidification reaction tower; a top flue gas outlet of the circulating dry deacidification reaction tower is connected with a flue gas inlet of the bag-type dust collector; a flue gas outlet of the bag-type dust collector is connected with a flue gas inlet of the flue gas waste heat recovery heat exchanger; and a shell-and-tube flue gas-air preheater is arranged at the tail end of the waste heat boiler. According to the system, flue gas purification and gradient utilization of waste heat can be achieved, and remarkable economic and environmental benefits are brought.

Description

Technical Field

[0001] The present invention relates to the technical field of waste incineration flue gas treatment, and particularly relates to a waste incineration flue gas purification and waste heat gradient utilization system. Background Art

[0002] Waste incineration power generation, as the best way to "reduce, harmlessize and recycle" domestic waste, has developed rapidly. During the process of domestic waste incineration power generation, flue gas containing various pollutants (acid gases, dust particles, heavy metals, dioxins and nitrogen oxides) is generated. Against the background that ultra-low emissions have been implemented in coal-fired power plants, the steel industry, the cement industry and the coking industry, and the emission standards for atmospheric pollutants from domestic waste incineration are becoming stricter in many places, it is also an irresistible trend for the domestic waste incineration industry to achieve ultra-low emissions. In addition, the flue gas generated by waste incineration contains a large amount of waste heat. Rational utilization of it can not only improve the energy utilization efficiency, but also bring significant economic and environmental benefits. However, there are still many drawbacks in the current waste incineration flue gas treatment process.

[0003] The existing waste incineration flue gas purification generally adopts a combined process, which is mainly divided into a 5-step, 6-step and 7-step combined process. Specifically: ① 5-step process: in-furnace denitrification (SNCR) + semi-dry reaction tower + activated carbon injection + dry desulfurization + bag filter; ② 6-step process: in-furnace denitrification (SNCR) + semi-dry reaction tower + activated carbon injection + dry desulfurization + bag filter + out-of-furnace catalytic denitrification (SCR); ③ 7-step process: in-furnace denitrification (SNCR) + semi-dry reaction tower + activated carbon injection + dry desulfurization + bag filter + wet method + out-of-furnace catalytic denitrification (SCR). The semi-dry reaction tower in the above processes is generally a rotary spray drying tower (SDA). For the waste incineration flue gas treated by SDA, the unreacted slaked lime in the fly ash is more than 38wt%, the lime consumption is high, and the fly ash treatment cost is high.

[0004] In addition, although the content of acid gases (including HCl, HF, SO2, etc.) in the discharged flue gas can meet the requirements of the national standard GB18485-2014 after being treated by the combined process of semi-dry reaction tower + dry desulfurization, the desulfurization efficiency of the semi-dry method and the dry method can reach 85% and 50% respectively. However, for the rotary spray semi-dry desulfurization process, the inlet flue gas temperature of the reaction tower is generally required to be 190°C. During the semi-dry desulfurization process, the water carried in the sprayed lime slurry will reduce the temperature of the flue gas to about 150°C, a temperature drop of about 40°C, resulting in great heat loss; and the flue gas after the bag filter still has a high temperature, usually between 145-150°C. If directly discharged, it will cause a large amount of energy waste.

[0005] Therefore, in the current waste incineration flue gas treatment process, there are problems such as low matching degree between flue gas deacidification treatment and waste heat utilization, large heat loss during the deacidification process, and direct discharge of the low-temperature waste heat of the dust-removing flue gas without effective utilization, resulting in relatively large energy waste. Summary of the Invention

[0006] The present invention aims to at least solve the above technical problems existing in the prior art. To this end, one of the objectives of the present invention is to provide a waste incineration flue gas purification and waste heat gradient utilization system.

[0007] Another objective of the present invention is to provide a method for treating waste incineration flue gas.

[0008] In order to achieve the above objectives, the technical solutions adopted by the present invention are as follows:

[0009] The first aspect of the present invention provides a waste incineration flue gas purification and waste heat gradient utilization system, including a waste heat boiler 100, a circulating dry deacidification reaction tower 200, a bag filter 300, and a flue gas waste heat recovery heat exchanger 400 arranged in sequence;

[0010] The circulating dry deacidification reaction tower 200 is successively provided with a bottom flue gas inlet, a middle section feeding section, and a top flue gas outlet from bottom to top;

[0011] The flue gas outlet of the waste heat boiler 100 is connected to the bottom flue gas inlet of the circulating dry deacidification reaction tower 200;

[0012] The top flue gas outlet of the circulating dry deacidification reaction tower 200 is connected to the flue gas inlet of the bag filter 300;

[0013] The flue gas outlet of the bag filter 300 is connected to the flue gas inlet of the flue gas waste heat recovery heat exchanger 400;

[0014] A shell-and-tube flue gas-air preheater 110 is provided at the end of the waste heat boiler 100.

[0015] In some embodiments of the present invention, an atomizing water spraying device is provided at the bottom flue gas inlet of the circulating dry deacidification reaction tower 200.

[0016] In some embodiments of the present invention, the system further includes an activated carbon bin 500 and a hydrated lime bin 600, and the activated carbon bin 500 and the hydrated lime bin 600 are respectively connected to the middle section feeding section of the circulating dry deacidification reaction tower 200.

[0017] In some embodiments of the present invention, the system further includes an activated carbon blower 510, the activated carbon blower 510 is connected to the activated carbon bin 500, and the activated carbon bin 500 pneumatically conveys activated carbon to the circulating dry desulfurization reaction tower 200 through the activated carbon blower 510.

[0018] In some embodiments of the present invention, the system further includes a hydrated lime blower 610, the hydrated lime blower 610 is connected to the hydrated lime bin 600, and the hydrated lime bin 600 pneumatically conveys hydrated lime to the circulating dry desulfurization reaction tower 200 through the hydrated lime blower 610.

[0019] In some embodiments of the present invention, the system further includes a humidifying mixer 700; the bag filter 300 includes a plurality of dust removal chambers connected in series in sequence, a dust discharge hopper is provided at the lower part of the dust removal chamber, and a dust conveyor 310 is provided at the lower part of the dust discharge hopper; the ash discharge port of the dust conveyor 310 is connected to the feed port of the humidifying mixer 700; the discharge port of the humidifying mixer 700 is connected to the middle section feed section of the circulating dry desulfurization reaction tower 200.

[0020] In some embodiments of the present invention, the system further includes a process water tank 710 and a process water pump 720, the process water tank 710 is connected to the humidifying mixer 700, and the process water tank 710 conveys water source to the humidifying mixer 700 by power through the process water pump 720.

[0021] In some embodiments of the present invention, the system further includes an induced draft fan 800 and a chimney 900; the induced draft fan 800 is respectively connected to the flue gas outlet of the flue gas waste heat recovery heat exchanger 400 and the flue gas inlet of the chimney 900.

[0022] In some embodiments of the present invention, the system further includes a fly ash conveyor 1000; the fly ash conveyor 1000 is respectively connected to the circulating dry desulfurization reaction tower 200 and the bag filter 300, collects fly ash and conveys it to the fly ash stabilization system.

[0023] In some embodiments of the present invention, the circulating dry desulfurization reaction tower 200 is selected from a circulating fluidized bed single-stage reaction tower or a circulating fluidized bed double-stage reaction tower.

[0024] In some embodiments of the present invention, the flue gas waste heat recovery heat exchanger 400 is selected from a shell-and-tube surface heat exchanger or a phase change heat exchanger.

[0025] The basic principle of the present invention is described as follows:

[0026] (1) The waste incineration flue gas purification and waste heat gradient utilization system provided by the present invention uses a circulating dry desulfurization reaction tower 200 for flue gas desulfurization. Compared with the semi-dry desulfurization process, the flue gas discharge temperature of the waste heat boiler 100 can be reduced to 140 - 160 °C. Therefore, a shell-and-tube flue gas-air preheater 110 is arranged at the end of the waste heat boiler 100, making it one of the heat exchange surfaces of the waste heat boiler 100. It not only has the advantages of compact layout, large heat exchange area and less floor area, but also can use the heat of the high-temperature flue gas discharged from the waste heat boiler 100 to heat the air entering the incinerator, thereby realizing the recovery and reuse of energy, improving the overall thermal efficiency of the system, reducing heat loss while realizing flue gas purification;

[0027] (2) The flue gas inlet of the circulating dry desulfurization reaction tower 200 is provided with an atomizing water spraying device, which can be selectively used to reduce the flue gas temperature in the reaction tower and make the temperature in the reaction tower reach the optimal reaction temperature; the flue gas in the circulating dry desulfurization reaction tower 200 is fully mixed and reacted with the hydrated lime provided by the hydrated lime silo 600 for desulfurization, and the activated carbon provided by the activated carbon silo 500 is used as an adsorbent to adsorb heavy metals and dioxins and other toxic substances, realizing the synchronous removal of acidic gases (such as HCl, HF and SO2), heavy metals and dioxins, and avoiding air pollution;

[0028] (3) The flue gas discharged from the circulating dry desulfurization reaction tower 200 enters the bag filter 300. The bag filter 300 is provided with a plurality of dust removal chambers connected in series in sequence, which can capture the unreacted hydrated lime and store it in the ash discharge hopper, and then it is transported to the humidifying mixer 700 by the ash conveyor 310. Under the water source provided by the process water tank 710, the hydrated lime is humidified, stirred and mixed, and then sent into the circulating dry desulfurization reaction tower 200 for reuse, thereby reducing the consumption of hydrated lime, reducing the content of unreacted hydrated lime in the fly ash, and reducing the fly ash treatment cost;

[0029] (4) After the dust removal flue gas discharged from the bag filter 300 enters the flue gas waste heat recovery heat exchanger 400 to recover the flue gas energy, it is discharged into the chimney 900 through the induced draft fan 800. The recovered flue gas energy is used for heating domestic water, heating the main condensate water of the steam turbine, etc., realizing the deep utilization of the flue gas waste heat, and overcoming the problem of large energy waste caused by the direct discharge of the low-temperature waste heat of the dust removal flue gas without effective utilization;

[0030] (5) The circulating dry desulfurization reaction tower 200 and the bag filter 300 are also externally connected to a fly ash conveyor 1000. After the fly ash is collected by the fly ash conveyor 1000, it is sent to the fly ash stabilization system for treatment and disposal.

[0031] The second aspect of the present invention provides a method for treating waste incineration flue gas, including using the waste incineration flue gas purification and waste heat gradient utilization system described in the first aspect of the present invention for flue gas purification and waste heat gradient utilization.

[0032] In some embodiments of the present invention, the treatment method specifically includes the following steps:

[0033] The exhaust gas from the waste heat boiler enters the circulating dry desulfurization reaction tower after initially recovering heat through a shell-and-tube flue gas-air preheater. Activated carbon in the activated carbon bin and hydrated lime in the hydrated lime bin respectively enter the circulating dry desulfurization reaction tower to perform desulfurization treatment on the flue gas and adsorb dioxins and heavy metals, obtaining desulfurized flue gas.

[0034] The desulfurized flue gas enters a bag filter. Unreacted hydrated lime is collected in the ash discharge hopper and transported to a humidifying mixer through an ash conveyor. After humidifying and mixing, it enters the circulating dry desulfurization reaction tower for recycling. The dust-removed flue gas enters a flue gas waste heat recovery heat exchanger to recover the energy of the flue gas, and then is discharged into the chimney through an induced draft fan.

[0035] In some embodiments of the present invention, the atomizing water spraying device at the flue gas inlet of the circulating dry desulfurization reaction tower controls the water spraying amount according to the actual concentrations of HCl and SO2 in the flue gas and the emission limit values, specifically: when the HCl content in the raw flue gas is greater than or equal to 600 mg / m 3 and / or the SO2 content is greater than or equal to 400 mg / m 3 , the atomizing water spraying device is turned on to improve the desulfurization efficiency.

[0036] In some embodiments of the present invention, the physical and chemical parameters of the waste incineration flue gas include: the dust concentration is 10000 - 15000 mg / Nm 3 , the SO2 concentration is 200 - 600 g / Nm 3 , the HCl concentration is 400 - 800 mg / Nm 3 , and the flue gas temperature is 160 - 190 °C.

[0037] In some embodiments of the present invention, the exhaust gas volume of the waste heat boiler is 65000 - 90000 Nm 3 / h.

[0038] In some embodiments of the present invention, in the circulating dry desulfurization reaction tower, the Ca / S molar ratio of hydrated lime is 1.1 - 1.4.

[0039] In some embodiments of the present invention, the conveying amount of activated carbon (activated carbon mass / waste mass) is 0.5 - 0.7.

[0040] In some embodiments of the present invention, the conveying flow rate of activated carbon is 15 - 25 m / s.

[0041] In some embodiments of the present invention, the physical and chemical parameters of the activated carbon include at least one of the following parameters:

[0042] Ash content ≤ 10%; Moisture content ≤ 10%; Particle size of over 95% is less than 250 mesh; Specific surface area ≥ 800 m 2 / g; Combustion temperature 700 °C; Fuming temperature 450 °C; Loose bag density 490 kg / m 3 ; Methylene blue decolorization power ≥ 190 mg / g; Iodine adsorption value ≥ 1000 mg / g.

[0043] In some embodiments of the present invention, the delivery rate of the slaked lime (slaked lime mass / garbage mass) is 18 - 22.

[0044] In some embodiments of the present invention, the delivery flow rate of the slaked lime is 15 - 25 m / s.

[0045] In some embodiments of the present invention, the physical and chemical parameters of the slaked lime include at least one of the following parameters:

[0046] Purity ≥ 90%; Particle size of over 90% is less than 200 mesh; Specific surface area ≥ 14 m 2 / g; Hydrochloric acid insoluble content ≤ 0.15%; Fe content ≤ 0.04%; Mg and alkali metal content (calculated as Mg) ≤ 0.5%.

[0047] In some embodiments of the present invention, the temperature of the waste incineration flue gas is 160 - 190 °C.

[0048] In some embodiments of the present invention, the exhaust gas temperature of the waste heat boiler is 140 - 160 °C.

[0049] In some embodiments of the present invention, the exhaust gas temperature of the bag filter is 145 - 150 °C.

[0050] In some embodiments of the present invention, the exhaust gas temperature of the chimney is greater than 120 °C.

[0051] In some embodiments of the present invention, the energy recovered by the shell and tube flue gas - air preheater is used for heating the primary air of the boiler and / or heating the secondary air of the boiler.

[0052] In some embodiments of the present invention, the energy recovered by the flue gas waste heat recovery heat exchanger is used for heating domestic water and / or heating the main condensate of the steam turbine.

[0053] In some embodiments of the present invention, the main condensate water volume is 30 - 45 t / h; The temperature before heating is 85 - 95 °C.

[0054] In some embodiments of the present invention, the temperature of the air before heating by the shell and tube flue gas - air preheater is 25 - 30 °C; The air volume is 12000 - 20000 Nm 3 / h.

[0055] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0056] 1) The waste incineration flue gas purification and waste heat gradient utilization system provided by the present invention uses a circulating dry desulfurization reaction tower to replace the "semi-dry reaction tower + activated carbon injection + dry desulfurization" treatment process for conventional waste incineration flue gas purification. It can not only complete flue gas desulfurization and the adsorption of heavy metals and dioxins, but also reduce the exhaust gas temperature of the waste heat boiler. The shell-and-tube flue gas-air preheater set at the rear end of the waste heat boiler is used to recover this part of heat and is used for waste incineration, reducing heat loss during the flue gas desulfurization and purification process and improving the overall thermal efficiency of the system; a flue gas waste heat recovery heat exchanger is set at the rear end of the bag filter to recover and reuse the flue gas energy, which can reduce the energy waste caused by the direct discharge of the low-temperature waste heat of the dust-removing flue gas. The gradient utilization of the flue gas waste heat can effectively improve the overall thermal efficiency of the whole plant, bringing significant economic and environmental benefits;

[0057] 2) The method for treating waste incineration flue gas provided by the present invention can not only purify the flue gas to meet the ultra-low emission requirements, but also reduce the consumption of slaked lime, lower the chemical agent cost and fly ash treatment cost, and can effectively recover the flue gas heat energy and be used for waste incineration, domestic water heating, main condensate heating of steam turbines, etc., saving energy consumption and reducing resource waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 It is a schematic diagram of the waste incineration flue gas purification and waste heat gradient utilization system in the embodiment. Among them, 100 - waste heat boiler, 110 - shell-and-tube flue gas-air preheater, 200 - circulating dry desulfurization reaction tower, 300 - bag filter, 400 - flue gas waste heat recovery heat exchanger, 500 - activated carbon bin, 510 - activated carbon fan, 600 - slaked lime bin, 610 - slaked lime fan, 700 - humidifying mixer, 710 - process water tank, 720 - process water pump, 800 - induced draft fan, 900 - chimney, 1000 - fly ash conveyor. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0059] The content of the present invention will be further described in detail through specific embodiments below. Unless otherwise specified, the raw materials, reagents or devices used in the embodiments can be obtained from conventional commercial channels or can be obtained by existing technical methods. Unless otherwise specified, the test or measurement methods are all conventional methods in the art.

[0060] Embodiment

[0061] Figure 1 It is a schematic diagram of the waste incineration flue gas purification and waste heat gradient utilization system in the embodiment, which consists of Figure 1It can be known that in the embodiment, the waste incineration flue gas purification and waste heat gradient utilization system is sequentially provided with a waste heat boiler 100, a circulating dry desulfurization reaction tower 200, a bag filter 300, a flue gas waste heat recovery heat exchanger 400, a induced draft fan 800 and a chimney 900 from left to right; a shell and tube flue gas-air preheater 110 is arranged at the end of the waste heat boiler 100, and the heat reduced by the waste heat boiler 100 during flue gas exhaust is recovered by the shell and tube flue gas-air preheater 110 and exchanges heat with air. The heated air enters the incinerator to participate in waste incineration, and the cooled flue gas enters the reaction tower from the bottom flue gas inlet of the circulating dry desulfurization reaction tower 200;

[0062] An atomizing water spraying device is arranged at the bottom flue gas inlet of the circulating dry desulfurization reaction tower 200 to reduce the flue gas temperature in the reaction tower and make the temperature in the reaction tower reach the optimal reaction temperature; the activated carbon bin 500 pneumatically transports activated carbon to the circulating dry desulfurization reaction tower 200 through the activated carbon fan 510, and the hydrated lime bin 600 pneumatically transports hydrated lime to the circulating dry desulfurization reaction tower 200 through the hydrated lime fan 610. In the reaction tower, the flue gas is fully mixed with the hydrated lime for desulfurization, and the activated carbon adsorbs heavy metals and dioxins; the desulfurized flue gas is discharged from the top flue gas outlet of the circulating dry desulfurization reaction tower 200 and enters from the flue gas inlet of the bag filter 300;

[0063] Inside the bag filter 300, 4 series-connected dust removal chambers are provided, and a dust discharge hopper is arranged at the lower part of each dust removal chamber. The unreacted hydrated lime is captured and collected in the dust discharge hopper, and then transported to the humidifying mixer 700 by the ash conveyor 310 at the lower part of the dust discharge hopper. The process water tank 710 transports water source to the humidifying mixer 700 through the process water pump 720 for humidifying the hydrated lime. The stirred and mixed hydrated lime is transported to the circulating dry desulfurization reaction tower 200 again for circulation. The dust-removed flue gas is discharged from the flue gas outlet of the bag filter 300, enters the flue gas waste heat recovery heat exchanger 400 for waste heat recovery, and is then discharged into the chimney 900 through the induced draft fan 800. The recovered waste heat is used for heating the main condensate water of the steam turbine;

[0064] The fly ash conveyor 1000 collects the fly ash from the circulating dry desulfurization reaction tower 200 and the bag filter 300 and transports it to the fly ash stabilization system.

[0065] Using the above waste incineration flue gas purification and waste heat gradient utilization system to treat waste incineration flue gas, the treatment capacity of the waste incinerator is 400 t / d, and the SO2 concentration in the flue gas is 400 g / Nm 3 and the HCl concentration is 600 mg / Nm 3 , and the flue gas temperature is 160 - 190 °C.

[0066] The physical and chemical property parameters of the activated carbon in the activated carbon bin and the hydrated lime in the hydrated lime bin are shown in Table 1 below:

[0067] Table 1 Physicochemical property parameters of activated carbon in the activated carbon bin and slaked lime in the slaked lime bin

[0068]

[0069]

[0070] The specific steps of flue gas treatment are as follows:

[0071] The exhaust gas from the waste heat boiler (75300 Nm 3 / h) enters the shell-and-tube flue gas-air preheater (the temperature before secondary air heating is 30 °C, and the air volume is 15500 Nm 3 / h) to recover heat preliminarily and then enters the circulating dry desulfurization reaction tower (140 - 160 °C). The heated air enters the incinerator to participate in waste incineration; a spray water device is installed at the flue gas inlet at the bottom of the circulating dry desulfurization reaction tower. The set water spray volume is 0.4 t / h to improve the desulfurization efficiency, and the temperature is controlled above the dew point of the original flue gas by 20 °C, and the desulfurization efficiency is above 90%; the activated carbon in the activated carbon bin is pneumatically transported to the circulating dry desulfurization reaction tower by an activated carbon blower, and the activated carbon addition amount is 10 kg / h. The slaked lime in the slaked lime bin is pneumatically transported to the circulating dry desulfurization reaction tower by a slaked lime blower, and the slaked lime addition amount is 330 kg / h. The Ca / S molar ratio is controlled between 1.1 - 1.4. The flue gas in the reaction tower is fully mixed with the slaked lime to remove SO2 and HCl, and the activated carbon adsorbs heavy metals and dioxins to obtain desulfurized flue gas;

[0072] The desulfurized flue gas enters the bag filter, and the unreacted slaked lime is collected in the ash hopper and transported to the humidifying mixer by the ash conveyor. After humidifying and stirring, it enters the circulating dry desulfurization reaction tower for recycling. The dust-removing flue gas (145 - 150 °C) enters the flue gas waste heat recovery heat exchanger to recover the flue gas energy. The temperature after heat exchange is kept not lower than 120 °C. The flue gas after heat exchange is discharged into the chimney through the induced draft fan. The recovered energy is used for main condensate heating. The main condensate water volume is 37 t / h, the initial temperature is 90 °C, and the temperature is raised to 100 - 105 °C after heating. At the same time, a main condensate water regulation bypass is set to adjust the flue gas temperature.

[0073] After being treated by the above method, the contents of SO2, HCl, heavy metals and dioxins in the discharged flue gas all meet the requirements of GB18485 - 2014 "Pollution Control Standard for Municipal Solid Waste Incineration", realizing ultra-low emission of flue gas.

[0074] Compared with the prior art, the method for treating waste incineration flue gas provided by the present invention adopts a waste incineration flue gas purification and waste heat gradient utilization system. In the system, a circulating dry desulfurization reaction tower is used to replace the conventional flue gas treatment process of "semi-dry reaction tower + activated carbon injection + dry desulfurization", so that the exhaust gas temperature of the waste heat boiler can be reduced to about 140 - 160 °C. This part of the heat is recovered by a shell-and-tube flue gas-air preheater arranged at the end of the waste heat boiler, and the heated air is supplied to the incinerator to provide more sufficient heat for waste incineration, making the incineration process more complete and stable, and greatly improving the overall thermal efficiency of the system. Research shows that for every 15 °C reduction in the exhaust gas temperature, the boiler thermal efficiency increases by about 1%. The temperature of the flue gas after being treated by the bag filter can reach 145 - 150 °C. Direct discharge will cause a large amount of energy waste. By setting a flue gas waste heat recovery heat exchanger at the back end of the bag filter to recover the flue gas energy and using it for heating domestic water or the main condensate of the steam turbine, it can reduce the energy consumption of using gas water heaters or electric water heaters, or reduce the amount of deaeration steam used in the deaerator, reduce the fuel cost, and thus reduce the overall operating cost of the waste incineration power generation project and improve the economic benefits.

[0075] The waste incineration flue gas purification and waste heat gradient utilization system and the method for treating waste incineration flue gas provided by the present invention can not only reduce the consumption of desulfurization absorbent, improve the desulfurization efficiency, remove heavy metals and dioxins, and meet the requirements of ultra-low flue gas emissions, but also realize the gradient utilization of flue gas waste heat, effectively improve the overall thermal efficiency of the whole plant, and bring significant economic and environmental benefits.

Claims

1. A waste incineration flue gas purification and waste heat gradient utilization system, characterized in that: It comprises a waste heat boiler (100), a circulating dry deacidification reaction tower (200), a bag filter (300) and a flue gas waste heat recovery heat exchanger (400) which are arranged in sequence; The circulating dry deacidification reaction tower (200) is provided with a bottom flue gas inlet, a middle feeding section and a top flue gas outlet in sequence from bottom to top; The flue gas outlet of the waste heat boiler (100) is connected to the bottom flue gas inlet of the circulating dry deacidification reaction tower (200); The top flue gas outlet of the circulating dry deacidification reaction tower (200) is connected to the flue gas inlet of the bag filter (300); The flue gas outlet of the bag filter (300) is connected to the flue gas inlet of the flue gas waste heat recovery heat exchanger (400); A shell and tube type flue gas-air preheater (110) is provided at the end of the waste heat boiler (100).

2. The waste incineration flue gas purification and waste heat gradient utilization system according to claim 1 is characterized in that: The system further comprises an activated carbon bin (500) and a slaked lime bin (600), wherein the activated carbon bin (500) and the slaked lime bin (600) are respectively connected to the middle feeding section of the circulating dry deacidification reaction tower (200).

3. The waste incineration flue gas purification and waste heat gradient utilization system according to claim 1 is characterized in that: The bottom flue gas inlet of the circulating dry deacidification reaction tower (200) is provided with an atomizing water spraying device.

4. The waste incineration flue gas purification and waste heat gradient utilization system according to claim 1 is characterized in that: The system also includes a humidifying mixer (700); the bag filter (300) includes a plurality of dust removal chambers connected in series, an ash discharge hopper is provided at the lower portion of the dust removal chamber, and an ash conveyor (310) is provided at the lower portion of the ash discharge hopper; the ash outlet of the ash conveyor (310) is connected to the feed inlet of the humidifying mixer (700); the discharge outlet of the humidifying mixer (700) is connected to the middle feed section of the circulating dry deacidification reaction tower (200).

5. The waste incineration flue gas purification and waste heat gradient utilization system according to claim 1 is characterized in that: The system further comprises an induced draft fan (800) and a chimney (900); the induced draft fan (800) is respectively connected to the smoke outlet of the smoke waste heat recovery heat exchanger (400) and the smoke inlet of the chimney (900).

6. The waste incineration flue gas purification and waste heat gradient utilization system according to claim 1 is characterized in that: The system further comprises a fly ash conveyor (1000); the fly ash conveyor (1000) is respectively connected to the circulating dry deacidification reaction tower (200) and the bag filter (300), collects fly ash and conveys it to a fly ash stabilization system.

7. A method for treating waste incineration flue gas, characterized in that: The invention comprises adopting the waste incineration flue gas purification and waste heat gradient utilization system as described in any one of claims 1 to 6 to perform flue gas purification and waste heat gradient utilization.

8. The processing method according to claim 7, characterized in that: The processing method specifically comprises the following steps: The exhaust gas from the waste heat boiler enters the circulating dry deacidification reaction tower after the heat is initially recovered by the shell and tube flue gas-air preheater. The activated carbon in the activated carbon bin and the slaked lime in the slaked lime bin enter the circulating dry deacidification reaction tower respectively to deacidify the flue gas and adsorb dioxins and heavy metals to obtain deacidified flue gas. The deacidified flue gas enters the bag filter, captures unreacted slaked lime and collects it in the ash hopper, and is transported to the humidifying mixer through the ash conveyor. After humidification and mixing, it enters the circulating dry deacidification reaction tower for further circulation. The dust-removed flue gas enters the flue gas waste heat recovery heat exchanger to recover the flue gas energy, and is then discharged into the chimney through the induced draft fan.

9. The processing method according to claim 8, characterized in that: In the circulating dry deacidification reaction tower, the Ca / S molar ratio of slaked lime is 1.1-1.

4.

10. The processing method according to claim 8, characterized in that: The temperature of the waste incineration flue gas is 160-190°C; And / or, the exhaust gas temperature of the waste heat boiler is 140-160°C; and / or, the exhaust gas temperature of the bag filter is 145-150°C; and / or, the exhaust temperature of the chimney is greater than 120°C; and / or, the energy recovered by the shell and tube flue gas-air preheater is used for boiler primary air heating and / or boiler secondary air heating; And / or, the energy recovered by the flue gas waste heat recovery heat exchanger is used for heating domestic water and / or heating main condensate of steam turbine.

Images