Harmless treatment process for flue gas generated after waste incineration

Abstract

The invention discloses a harmless treatment process for flue gas generated after waste incineration. The harmless treatment process for the flue gas generated after waste incineration comprises the following steps that firstly, flue gas in an incinerator is introduced into a preheating pipeline preset in the furnace wall of a preheating furnace to heat to-be-treated waste in the preheating furnace; secondly, the flue gas led out of the preheating furnace is connected into a water-cooling cyclone separator to be subjected to gas-solid separation, and the separated flue gas continuously passes through a deacidification treatment section, an activated carbon adsorption treatment section and a filtering section on a flue and then is connected into an SCR treatment system; the deacidification treatment section comprises two volute type alkali powder mixers, the activated carbon adsorption section comprises an activated carbon spraying mechanism arranged along the circumferential section of the flue, and the filtering section is provided with a bag-type dust collector. By means of the mode, the temperature of inlet air entering the SCR system can be increased, the denitration efficiency is improved, waste water needing to be treated cannot be additionally generated, and the overall treatment cost is low.

Description

Technical Field

[0001] The present invention relates to the technical field of flue gas treatment, and in particular to a harmless treatment process for flue gas after garbage incineration. Background Art

[0002] The flue gas from waste incineration contains a variety of harmful substances and therefore cannot be discharged directly into the air. The current conventional flue gas treatment method is to discharge harmless gases into the atmosphere after deacidification treatment, small molecule adsorption treatment and denitrification treatment according to the types of harmful substances in the flue gas. Denitrification treatment is usually a customized SCR system, and flue gas deacidification treatment is generally carried out by wet or dry treatment. Although the wet treatment has a good absorption effect, on the one hand, it will produce wastewater that needs to be treated separately, and on the other hand, the heat loss is large, and it needs to be reheated before entering the SCR system, otherwise the reaction efficiency will be insufficient. The dry method is to directly spray alkaline powder in the flue. The powder has a short air time and poor absorption efficiency for acidic substances. Summary of the Invention

[0003] The main technical problem solved by the present invention is to provide a harmless treatment process for flue gas after garbage incineration, which can improve the treatment efficiency of the SCR system, reduce the generation of wastewater in the process, and improve the environmental friendliness of the treatment process.

[0004] In order to solve the above technical problems, a technical solution adopted by the present invention is: to provide a harmless treatment process for flue gas after garbage incineration, and the harmless treatment process for flue gas generated after garbage incineration includes the following steps: step 1, introducing the flue gas in the incinerator into a preset preheating pipe in the furnace wall of the preheating furnace to heat the garbage to be treated in the preheating furnace; step 2, connecting the flue gas drawn out from the preheating furnace to a water-cooled cyclone separator to perform gas-solid separation on the flue gas, and the separated flue gas continuously passes through the deacidification treatment section, activated carbon adsorption treatment section and filtration section on the flue and is then connected to the SCR treatment system; the deacidification treatment section includes two volute-type alkali powder mixers, the activated carbon adsorption section includes an activated carbon spraying mechanism arranged along the circumferential section of the flue, and the filtration section is provided with a bag dust collector.

[0005] In a preferred embodiment of the present invention, a first heat exchange pipe is provided between the water-cooled cyclone separator and the preheating furnace, and a second heat exchange pipe is provided between the water-cooled cyclone separator and the first volute-type alkali powder mixer.

[0006] In a preferred embodiment of the present invention, the heat exchange medium in the first heat exchange pipe is water, and the heat exchange medium in the second heat exchange pipe is flue gas before entering the SCR system.

[0007] In a preferred embodiment of the present invention, the temperature of the flue gas when entering the second heat exchange pipe through the water-cooled cyclone separator is 350-400°C, and the temperature of the flue gas when entering the SCR system after being heated by the heat exchange pipe is 250-300°C.

[0008] In a preferred embodiment of the present invention, the hot water drawn out from the water-cooled cyclone separator and the first heat exchange pipe is introduced into the previous garbage fermentation process and used as a heating medium for the fermentation environment.

[0009] In a preferred embodiment of the present invention, the mixing time of the flue gas in each volute mixer is not less than 10 seconds.

[0010] In a preferred embodiment of the present invention, the alkaline powder sprayed in the volute-type alkali powder mixer is calcium hydroxide or sodium bicarbonate. The average particle size of the alkaline powder and the activated carbon particles sprayed by the activated carbon spraying mechanism are both less than 50 μm.

[0011] In a preferred embodiment of the present invention, the dust filtered out by the bag filter is collected and sent to an incinerator for secondary incineration.

[0012] In a preferred embodiment of the present invention, the solid matter separated in the water-cooled cyclone separator is collected and sent to an incinerator for secondary incineration.

[0013] The beneficial effects of the present invention are as follows: the present invention further optimizes the existing flue gas harmless treatment system. On the one hand, a multi-channel volute mixer is added to the flue, and the traditional method of directly spraying alkaline powder into the flue to absorb acidic substances is changed to spraying in a dedicated volute mixer, thereby effectively increasing the mixing time between the powder and the flue gas and enhancing the overall absorption efficiency. On the other hand, the heat loss in the process is reduced, so that the flue gas can still maintain a high temperature after preliminary treatment and enter the SCR system, thereby reducing the flue gas heating requirements and improving the denitrification efficiency. Moreover, no additional wastewater that needs to be treated is generated as a whole, and the overall treatment cost is low. DETAILED DESCRIPTION

[0014] The preferred embodiments of the present invention are described in detail below so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more precise definition of the protection scope of the present invention.

[0015] The embodiments of the present invention include:

[0016] A process for harmless treatment of flue gas after waste incineration, comprising the following steps:

[0017] Step 1: Introduce the flue gas from the incinerator into the preheating pipe preset in the furnace wall of the preheating furnace to heat the garbage to be processed in the preheating furnace;

[0018] In step 2, the flue gas drawn out from the preheating furnace is connected to a water-cooled cyclone separator to perform gas-solid separation on the flue gas. The separated flue gas is continuously passed through the deacidification treatment section, the activated carbon adsorption treatment section and the filtration section on the flue and then connected to the SCR treatment system; the deacidification treatment section includes two volute-type alkali powder mixers, the activated carbon adsorption section is provided with an activated carbon spraying mechanism arranged along the circumferential section of the flue, and the filtration section is provided with a bag dust collector. The solid matter separated in the water-cooled cyclone separator and the dust filtered out by the bag dust collector are collected and sent together to the incinerator for incineration.

[0019] The temperature of the flue gas drawn out from the preheating furnace is relatively high, generally not less than 600°C. Therefore, a first heat exchange pipe is set between the water-cooled cyclone separator and the preheating furnace, and a second heat exchange pipe is set between the water-cooled cyclone separator and the first volute-type alkali powder mixer. The heat exchange medium in the first heat exchange pipe is water, and the heat exchange medium in the second heat exchange pipe is the flue gas before entering the SCR system. By controlling the flow rate of cooling water in the water-cooled cyclone separator and the first heat exchange pipe, the temperature of the flue gas entering the second heat exchange pipe from the water-cooled cyclone separator can be indirectly controlled, so that the temperature of the flue gas entering the second heat exchange pipe is 350-400°C. The flue gas temperature at this point is then used to heat the flue gas, whose temperature has been reduced due to continuous deacidification and adsorption treatment, through the heat exchange pipe, so that the flue gas can be maintained in the optimal reaction temperature range, that is, between 250°C and 300°C, when it finally enters the SCR system. This improves the working efficiency of the SCR system while eliminating the need for additional heating of the flue gas. Moreover, the hot water drawn out from the water-cooled cyclone separator and the first heat exchange pipe is introduced into the previous garbage fermentation process, and can be used as an environmental heating medium, making full use of waste heat, further reducing heat loss in the system, and reducing resource waste.

[0020] The alkaline powder sprayed in the first volute-type alkali powder mixer is calcium hydroxide, while the alkaline powder sprayed in the second volute-type alkali powder mixer is sodium bicarbonate. The combined use of these two alkaline powders effectively removes acidic substances from the flue gas. Furthermore, the average particle size of both alkaline powders and the activated carbon particles sprayed in the activated carbon adsorption section described later is less than 50 μm. Furthermore, the flue gas retention time in each unit is 10 seconds. This small particle size and large specific surface area effectively adsorb harmful substances from the flue gas, improving purification efficiency.

[0021] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A process for harmless treatment of flue gas after garbage incineration, characterized in that: The harmless treatment process of flue gas generated after garbage incineration comprises the following steps: Step 1: introducing the flue gas in the incinerator into a preheating pipe preset in the furnace wall of the preheating furnace to heat the garbage to be processed in the preheating furnace; Step 2: The flue gas drawn out from the preheating furnace is connected to a water-cooled cyclone separator to separate the flue gas from solids. The separated flue gas is continuously passed through a deacidification treatment section, an activated carbon adsorption treatment section and a filtration section on the flue before being connected to an SCR treatment system. The deacidification treatment section includes two volute-type alkali powder mixers, the activated carbon adsorption section includes an activated carbon spraying mechanism arranged along the circumferential section of the flue, and the filtering section is provided with a bag dust collector.

2. The process for harmless treatment of flue gas after waste incineration according to claim 1 is characterized in that: A first heat exchange pipeline is arranged between the water-cooled cyclone separator and the preheating furnace, and a second heat exchange pipeline is arranged between the water-cooled cyclone separator and the first volute-type alkali powder mixer.

3. The process for harmless treatment of flue gas after waste incineration according to claim 2 is characterized in that: The heat exchange medium in the first heat exchange pipe is water, and the heat exchange medium in the second heat exchange pipe is flue gas before entering the SCR system.

4. The process for harmless treatment of flue gas after waste incineration according to claim 3 is characterized in that: The temperature of the flue gas when entering the second heat exchange pipe through the water-cooled cyclone separator is 350-400°C, and the temperature of the flue gas when entering the SCR system after being heated by the heat exchange pipe is 250-300°C.

5. The process for harmless treatment of flue gas after waste incineration according to claim 1 is characterized in that: The hot water drawn out from the water-cooled cyclone separator and the first heat exchange pipe is introduced into the previous garbage fermentation process and used as a heating medium for the fermentation environment.

6. The process for harmless treatment of flue gas after waste incineration according to claim 1 is characterized in that: The mixing time of the flue gas in each volute mixer is not less than 10 seconds.

7. The process for harmless treatment of flue gas after waste incineration according to claim 1, characterized in that: The alkaline powder sprayed in the volute type alkali powder mixer is calcium hydroxide or sodium bicarbonate.

8. The process for harmless treatment of flue gas after waste incineration according to claim 7 is characterized in that: The average particle size of the alkaline powder and the activated carbon particles sprayed by the activated carbon spraying mechanism are both less than 50um.

9. The process for harmless treatment of flue gas after waste incineration according to claim 1, characterized in that: The dust filtered out by the bag filter is collected and sent to the incinerator for secondary incineration.

10. The process for harmless treatment of flue gas after waste incineration according to claim 1, characterized in that: The solid matter separated in the water-cooled cyclone separator is collected and sent to an incinerator for secondary incineration.