Boiler corrosion suppression device and method

Abstract

To provide a boiler corrosion inhibition device that protects a boiler against corrosion while rendering exhaust gases harmless.SOLUTION: A boiler corrosion inhibition device includes: a first dust collector 4 that removes soot present in the exhaust gases discharged from a boiler 2, which recovers heat from the exhaust gases of a waste incinerator 1; SOx separators 5, 6 that selectively separate SOx from the exhaust gases with the removed soot; a second dust collector 7 that removes at least one of HCl, mercury, and dioxins from the exhaust gases with the SOx removed through the SOx separators; and a blower 9 that blows the SOx separated through the SOx separators 5, 6 into the boiler 2 and / or the waste incinerator 1.SELECTED DRAWING: Figure 1

Description

Technical Field

[0003]

[0001] The present invention relates to a corrosion suppression device and method for a boiler that recovers heat from exhaust gas discharged from a waste incinerator.

Background Art

[0002] A waste incinerator for incinerating waste such as municipal waste is provided with a boiler that recovers heat from the exhaust gas discharged from the waste incinerator. The boiler includes a water-cooled wall that forms a flue and a superheater disposed in the flue. The water-cooled wall heats water to generate steam. The superheater superheats the steam to superheated steam. The superheated steam is supplied to a steam turbine.

[0003] Waste contains chlorine-containing resins such as plastics. Therefore, when the waste is burned, HCl gas and Cl2 gas are generated, and combustion ash containing chlorine components due to HCl gas and Cl2 gas accumulates on the surface of the heat transfer tube group of the superheater of the boiler. This combustion ash containing chlorine components has a problem of corroding the superheater of the boiler.

[0004] In order to suppress the corrosion of the superheater of the boiler, attempts have been made to increase the SOx concentration in the exhaust gas of the boiler. For example, Patent Document 1 discloses a technique in which SO2 stored in a SO2 cylinder is blown into the upstream side of the superheater of the boiler to increase the SO2 concentration. Since the blown-in SO2 is adsorbed by the combustion ash attached to the superheater, the corrosion of the superheater can be suppressed.

[0005] Also, Patent Document 2 discloses a technique for mixing waste tires containing sulfur into waste fuel to generate sulfides due to sulfur in the combustion ash in order to achieve the same purpose. By generating sulfides in the combustion ash, the concentration of chlorine components in the combustion ash decreases, so that the corrosion of the superheater can be suppressed.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

[0007] However, conventional boiler corrosion suppression systems involve adding sulfur-containing additives (SO2, waste tires) to the system, which increases the load on the treatment equipment, increases the amount of waste requiring special management such as fly ash, and increases the cost of securing the materials to be blown in, making them impractical.

[0008] This invention has been made in view of the above-mentioned problems, and aims to provide a boiler corrosion suppression device and method that can simultaneously suppress boiler corrosion and detoxify exhaust gas. [Means for solving the problem]

[0009] To solve the above problems, one aspect of the present invention provides a first dust collector for removing soot contained in exhaust gas discharged from a boiler that recovers heat from the exhaust gas of a waste incinerator, and a SOx separator for selectively separating SOx from the exhaust gas from which the soot has been removed. At least an alkaline agent was blown in, From the exhaust gas after SOx has been separated by the SOx separation device at least HC l This boiler corrosion suppression device comprises a second dust collector for removal and a blowing device for blowing the SOx separated by the SOx separation device into the boiler and / or the waste incinerator.

[0010] Another aspect of the present invention is a step of removing dust and ash discharged from a boiler that recovers heat from the exhaust gas of a waste incinerator, and a step of selectively separating SOx from the exhaust gas from which the dust and ash has been removed. At least spray in an alkaline agent, SOx is separated from the exhaust gas at least HC l A method for suppressing corrosion in a boiler, comprising the steps of removing SOx and blowing the separated SOx into the boiler and / or the waste incinerator. [Effects of the Invention]

[0011] According to the present invention, the SOx concentration of the exhaust gas in the boiler can be increased without adding sulfur-containing additives to the system, thereby simultaneously suppressing boiler corrosion and detoxifying the exhaust gas. [Brief explanation of the drawing]

[0012] [Figure 1] This is a system diagram of a waste incineration facility using a boiler corrosion suppression device according to one embodiment of the present invention. [Modes for carrying out the invention]

[0013] Hereinafter, an embodiment of the boiler corrosion suppression device of the present invention will be described based on the attached drawings. However, the boiler corrosion suppression device of the present invention can be embodied in various forms and is not limited to the embodiments described herein. This embodiment is provided with the intention that those skilled in the art will be able to fully understand the scope of the invention by making full disclosures in the specification.

[0014] Figure 1 shows a system diagram of a waste incineration facility using a boiler corrosion suppression device according to one embodiment of the present invention. 1 is the waste incinerator, 2 is the boiler, 3 is the economizer, 4 is the first dust collector, 5 and 6 are SOx separators, 7 is the second dust collector, 8 is the chimney, and 9 is the blowing device. The boiler corrosion suppression device of this embodiment comprises a first dust collector 4, SOx separators 5 and 6, a second dust collector 7, and a blowing device 9. The configuration of each part is described below.

[0015] The waste incinerator 1 is, for example, a stoker-type incinerator. The waste incinerator 1 comprises a furnace body 11 for drying and burning waste, and a hopper 12 for feeding waste into the furnace body 11. A stoker 13 is provided at the bottom of the furnace body 11 to supply combustion air for burning the waste and to transport the waste. Above the stoker 13 are a primary combustion chamber 15 and a secondary combustion chamber 16. Exhaust gas flows from bottom to top through the primary combustion chamber 15 and the secondary combustion chamber 16. Incinerated ash is transported by the stoker 13 to the discharge port 14 and discharged from the discharge port 14. The type of waste incinerator 1 is not particularly limited, and may be, for example, a fluidized bed incinerator.

[0016] Downstream of the waste incinerator 1, a boiler 2 is provided to recover heat from the exhaust gas of the waste incinerator 1. The flue of the boiler 2 includes a radiant heat transfer chamber 21 and a convection heat transfer chamber 22. The exhaust gas flowing from bottom to top through the secondary combustion chamber 16 of the waste incinerator 1 has its flow direction changed by the first deflection section 23 and flows from top to bottom through the radiant heat transfer chamber 21 of the boiler 2, and then its flow direction is changed by the second deflection section 24 and flows from bottom to top through the convection heat transfer chamber 22. The inner walls of the radiant heat transfer chamber 21 and the convection heat transfer chamber 22 are made of water-cooled walls. The water-cooled walls heat water to generate steam.

[0017] Multiple superheaters 25 are arranged in the convection heat transfer chamber 22. Each superheater 25 is equipped with a group of heat transfer tubes that exchange heat with the exhaust gas and superheats the steam to generate superheated steam. The superheater 25 may consist of, for example, a first-stage superheater, a middle-stage superheater, and a final-stage superheater, starting from the downstream side of the exhaust gas.

[0018] An economizer 3 is installed downstream of boiler 2. Economizer 3 is equipped with a group of heat transfer tubes that exchange heat with exhaust gas and heat water to generate heated water.

[0019] On the downstream side of the economizer 3, a first dust collector 4 is provided. The first dust collector 4 is an electrostatic precipitator, a filtration type dust collector, etc., and removes the dust contained in the exhaust gas. Since the first dust collector 4 removes dust at a slightly high temperature (for example, 200°C), an electrostatic precipitator is desirable, but a filtration type dust collector may also be used. The first dust collector 4 also has the role of preventing the adsorbents of the SOx separation devices 5 and 6 from being clogged by dust.

[0020] On the downstream side of the first dust collector 4, SOx separation devices 5 and 6 that selectively separate SOx are provided. SOx is a sulfur oxide and is at least one of SO2, SO3, H2SO4 gas, etc. The SOx separation device 5 may selectively separate SOx by an adsorbent such as a ceramic filter, an inorganic adsorbent, a metal organic framework (MOF), or may selectively separate SOx by blowing in a peroxide. Also, the SOx separation devices 5 and 6 may selectively separate only SOx, or may selectively separate SOx together with NOx (nitrogen oxides) and HCl (hydrogen chloride).

[0021] When the SOx separation devices 5 and 6 are provided with an adsorbent, it is desirable that the adsorbent be regenerable, that is, SOx can be detached from the adsorbent. For example, by blowing hot air into the adsorbent, treating the adsorbent, or vibrating the adsorbent, SOx can be detached from the adsorbent.

[0022] The two SOx separation devices 5 and 6 are alternately used by switching the flue. That is, when the SOx separation device 5 adsorbs SOx, the SOx separation device 6 detaches SOx. Also, when the SOx separation device 6 adsorbs SOx, the SOx separation device 5 detaches SOx. Note that, without switching the flue, the adsorbent of the SOx separation device 5 may be taken out and incorporated into the SOx separation device 6.

[0023] The blowing device 9 injects the SOx separated by the SOx separators 5 and 6 into the boiler 2. The blowing device 9 is equipped with a blower and injects air and heat (hot air) into the SOx separators 5 and 6. When the blowing device 9 injects hot air into the SOx separators 5 and 6, SOx is separated from the SOx separators 5 and 6. The separated SOx is injected upstream of the superheater 25 of the boiler 2 via piping. Injecting SOx into the boiler 2 is effective in suppressing corrosion of the superheater 25, but SOx may also be injected into the waste incinerator 1, or into both the boiler 2 and the waste incinerator 1.

[0024] A second dust collector 7 is provided downstream of the SOx separators 5 and 6. The second dust collector 7 removes HCl, mercury, and dioxins from the exhaust gas after SOx has been separated by the SOx separators 5 and 6. It is desirable to use a filtration type dust collector to remove HCl, mercury, and dioxins at low temperatures (e.g., 140°C). It is also desirable to blow an alkaline agent to remove HCl and activated carbon to remove mercury and dioxins into the second dust collector 7. The alkaline agent includes at least one of slaked lime, baking soda, or dolomite. Since the alkaline agent and activated carbon also remove SOx, the second dust collector 7 is placed downstream of the SOx separator 5. Alternatively, only the alkaline agent may be blown into the second dust collector 7 to remove HCl, or only the activated carbon may be blown into the second dust collector 7 to remove mercury and dioxins. Alternatively, the second dust collector 7 may be a wet-type fume scrubber to remove HCl, mercury, and dioxins.

[0025] The exhaust gas, from which impurities have been removed, is released into the atmosphere through the chimney 8. If it is necessary to remove NOx, a denitrification device for removing NOx from the exhaust gas may be installed downstream of the second dust collector 7.

[0026] The effects of the boiler corrosion suppression device of this embodiment will be explained below. Since the SOx concentration of the exhaust gas in boiler 2 can be increased without adding sulfur-containing additives to the system, corrosion of boiler 2 and detoxification of the exhaust gas can be achieved simultaneously.

[0027] The corrosion occurring on the surface of the heat transfer tubes in the superheater 25 is chlorination-oxidation corrosion caused by HCl and the Cl content in the corroded incinerator ash. By increasing the SOx concentration in the exhaust gas inside the boiler 2, the exchange reaction between Cl and S in the incinerator ash is promoted. As a result, chlorination-oxidation corrosion is suppressed.

[0028] Since the first dust collector 4 is installed upstream of the SOx separators 5 and 6, clogging of the adsorbent in the SOx separators 5 and 6 can be prevented. In addition, since the second dust collector 7 is installed downstream of the SOx separators 5 and 6, SOx can be prevented from being removed from the exhaust gas by the second dust collector 7 before the SOx separators 5 and 6 separate SOx from the exhaust gas.

[0029] Since the SOx separators 5 and 6 are equipped with regenerative adsorbents, it is easy to separate SOx from exhaust gas and to blow the separated SOx into the boiler 2 and / or waste incinerator 1. [Explanation of Symbols]

[0030] 1…Waste incinerator 2… Boiler 3…Economizer 4…First dust collector 5,6…SOx separation equipment 7…Second dust collector 8... Chimney 9... Blowing device

Claims

1. A first dust collector removes soot and dust contained in the exhaust gas discharged from a boiler that recovers heat from the exhaust gas of a waste incinerator, SOx separation device for selectively separating SOx from exhaust gas from which soot and dust have been removed, A second dust collector that blows in at least an alkaline agent and removes at least HCl from the exhaust gas after SOx has been separated by the SOx separation device, A boiler corrosion suppression device comprising: a blowing device for blowing SOx separated by the SOx separation device into the boiler and / or the waste incinerator.

2. The boiler corrosion suppression device according to claim 1, characterized in that the SOx separation device comprises a regenerative adsorbent.

3. A process to remove soot and dust discharged from a boiler that recovers heat from the exhaust gas of a waste incinerator, A process for selectively separating SOx from exhaust gas from which soot and dust have been removed, The process includes at least blowing in an alkaline agent and removing at least HCl from the exhaust gas from which SOx has been separated, A method for suppressing corrosion in a boiler, comprising the step of blowing the separated SOx into the boiler and / or the waste incinerator.

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