Anti-corrosion device of super heater of waste boiler and method

Abstract

To provide an anti-corrosion device of a super heater of a waste boiler which can achieve more anticorrosive effect.SOLUTION: An anti-corrosion device 12 alternately blows a sulfur compound and hydrogen chloride into a radiant heat transfer chamber 6 or / and a convective heat transfer chamber 7 of a waste boiler 3 having a super heater 10.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a corrosion protection device and method for a superheater of a waste boiler. [Background technology]

[0002] Waste incinerators burn waste such as garbage as fuel. Waste boilers recover the thermal energy of the waste incinerator's exhaust gas. A waste boiler is equipped with a superheater in its convection heat transfer chamber, which uses the heat of the incinerator's exhaust gas to superheat steam. The high-temperature, high-pressure superheated steam produced by the superheater is used to generate electricity.

[0003] A characteristic of waste incinerators is that the waste used as fuel contains a high concentration of chlorine. Chlorine reacts with alkali metals such as K and Na to form chlorides. Fly ash containing these chlorides is scattered from the incinerator to the downstream waste boiler and adheres to the heat transfer tubes of the waste boiler's superheater. The chlorides in the ash cause high-temperature corrosion of the superheater's heat transfer tubes.

[0004] In order to prevent corrosion of the heat transfer tubes of the superheater, Patent Documents 1 and 2 disclose a corrosion prevention method in which a probe for monitoring corrosion of the heat transfer tubes of the superheater is installed in the convection heat transfer chamber of a waste boiler, and a sulfur compound (SO2, SO3, H2SO4, NaHSO3, ZnSO4, etc.) is injected as a corrosion inhibitor into problem areas where corrosion is confirmed based on the amount of corrosion monitored.

[0005] As in the inventions described in Patent Documents 1 and 2, by injecting a sulfur compound, chlorides are converted into sulfates, which are less likely to cause corrosion, as shown in Equation 1, thereby suppressing corrosion of the superheater. (Formula 1) 2XCl (chlorides) + SO3 (sulfur compounds) + H2O → X2SO4 (sulfates) + 2HCl X is a metal cation including alkali metals such as K and Na. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 5165556 [Patent Document 2] Patent No. 5406895 Summary of the Invention [Problem to be solved by the invention]

[0007] However, conventional corrosion prevention methods have a limited corrosion prevention effect because they do not work on CuSO4, which is known to cause severe corrosion. In other words, even if sulfur compounds are injected to convert Cu into the sulfate CuSO4, the CuSO4 still causes severe corrosion.

[0008] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a corrosion prevention device and method for a superheater of a waste boiler that can obtain a stronger corrosion prevention effect. [Means for solving the problem]

[0009] In order to solve the above problems, one aspect of the present invention is a corrosion prevention device for a superheater of a waste boiler, which alternately injects a sulfur compound and hydrogen chloride into the radiant heat transfer chamber and / or the convective heat transfer chamber of the waste boiler equipped with a superheater.

[0010] Another aspect of the present invention is a method for preventing corrosion in a superheater of a waste boiler, which comprises alternately injecting a sulfur compound and hydrogen chloride into a radiant heat transfer chamber and / or a convective heat transfer chamber of the waste boiler equipped with a superheater. [Effects of the Invention]

[0011] According to the present invention, a sulfur compound and hydrogen chloride are alternately injected into the radiant heat transfer chamber and / or the convective heat transfer chamber of a waste boiler equipped with a superheater, thereby promoting the sulfation of chlorides in ash adhering to the heat transfer tubes of the superheater and the volatilization of chlorides in CuSO4 in the ash, thereby achieving a stronger corrosion prevention effect. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is an overall view of a waste-to-energy plant to which a corrosion prevention device according to an embodiment of the present invention is applied. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, a corrosion prevention apparatus and method for a superheater of a waste boiler according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. However, the corrosion prevention apparatus and method for a superheater of a waste boiler according to the present invention can be embodied in various forms and is not limited to the embodiments described in the specification. The present embodiment is provided with the intention of enabling those skilled in the art to fully understand the invention by fully disclosing the specification.

[0014] FIG. 1 shows a waste-to-energy plant 1 to which a corrosion prevention device for a superheater of a waste-to-energy boiler according to one embodiment of the present invention is applied. The waste-to-energy plant 1 includes a waste incinerator 2 and a waste boiler 3. The waste incinerator 2 is typically a stoker furnace. The incineration method of the waste incinerator 2 may be a fluidized bed furnace or a gasification melting furnace. The waste incinerator 2 combusts waste such as garbage fed into a hopper 4 in a combustion chamber 5. The exhaust gas generated in the combustion chamber 5 passes through the waste boiler 3 for heat recovery and is then guided to an exhaust gas treatment system 8. The exhaust gas treatment system 8 purifies the exhaust gas through environmental measures such as exhaust gas treatment and dust removal. The purified exhaust gas is discharged from a chimney (not shown).

[0015] A waste boiler 3 that obtains energy from waste such as garbage includes a radiant heat transfer chamber 6 and a convective heat transfer chamber 7. The radiant heat transfer chamber 6 includes a water-cooled wall that receives radiant heat from the exhaust gas to generate steam. An evaporator 9, a superheater 10, and other components are disposed in the convective heat transfer chamber 7. The evaporator 9 exchanges heat with the exhaust gas to generate steam. The superheater 10 exchanges heat with the exhaust gas to superheat the steam generated in the water-cooled wall of the radiant heat transfer chamber 6 or the evaporator 9. The evaporator 9 may be omitted, or an economizer may be disposed in the convective heat transfer chamber 7. The superheater 10 may also be disposed in the radiant heat transfer chamber 6.

[0016] Reference numeral 11 denotes an ash removal device such as a soot blower that injects an injection medium such as steam or air onto the heat transfer tubes of the superheater 10 to remove ash adhering to the heat transfer tubes of the superheater 10. The ash removal device 11 may be a hammering device such as an air knocker that applies an impact to the heat transfer tubes of the superheater 10 to remove ash, or a device that removes ash by using shock waves.

[0017] Reference numeral 12 denotes a corrosion prevention device that alternately injects a sulfur compound and hydrogen chloride into the convection heat transfer chamber 7. The corrosion prevention device 12 may alternately inject a sulfur compound and hydrogen chloride into the radiant heat transfer chamber 6, or may alternately inject a sulfur compound and hydrogen chloride into the radiant heat transfer chamber 6 and the convection heat transfer chamber 7. Sulfur compounds include S, SO2, SO3, H2SO4, NaHSO3, and ZnSO4. The sulfur compound may be injected into the convection heat transfer chamber 7 in a gaseous state, a liquid state, or a solid state. Hydrogen chloride (HCl) may be injected into the convection heat transfer chamber 7 in a gaseous state or a liquid state.

[0018] The corrosion prevention device 12 includes a nozzle for alternately injecting a sulfur compound and hydrogen chloride, a supply source for the sulfur compound and hydrogen chloride, and a conduit for guiding the sulfur compound and hydrogen chloride to the nozzle. The nozzle may be a nozzle for both the sulfur compound and hydrogen chloride, or a dedicated nozzle for each, as long as it can alternately inject the sulfur compound and hydrogen chloride. It is preferable that the nozzle alternately inject the sulfur compound and hydrogen chloride upstream of the superheater 10.

[0019] When the corrosion prevention device 12 injects sulfur compounds into the convection heat transfer chamber 7, the chlorides in the ash are converted into sulfates, which are less likely to cause corrosion, as shown in Equation 2. This makes it possible to suppress corrosion of the heat transfer tubes of the superheater 10. (Formula 2) 2XCl (chlorides) + SO3 (sulfur compounds) + H2O → X2SO4 (sulfates) + 2HCl X is a metal cation including alkali metals such as K and Na.

[0020] However, CuSO4, a sulfate of Cu, is an exceptional case that causes severe corrosion. When sulfur compounds are blown into the ash, elemental Cu, CuO, is converted to CuSO4. When sulfur compounds are blown into the ash, CuSO4 does not react and remains as it is. This CuSO4 causes severe corrosion.

[0021] To prevent severe corrosion caused by CuSO4, the corrosion prevention device 12 injects hydrogen chloride into the convection heat transfer chamber 7, converting the CuSO4 in the ash into gaseous CuCl2 and volatilizing it as shown in Equation 3. The amount of CuSO4 in the ash decreases as CuCl2 is volatilized, thereby suppressing severe corrosion caused by CuSO4. (Formula 3) CuSO4 + 2HCl → CuCl2↑ (evaporation) + H2SO4

[0022] If the corrosion prevention device 12 injects the sulfur compound and hydrogen chloride simultaneously, the reaction of Equation 3 will not proceed as easily because sulfate is thermodynamically more stable. To prevent this, the corrosion prevention device 12 injects the sulfur compound and hydrogen chloride alternately.

[0023] It is desirable that the corrosion prevention device 12 be able to cooperate with the ash removal device 11, which removes ash adhering to the superheater 10. For example, the control device 14 operates the corrosion prevention device 12 in accordance with the operation timing of the ash removal device 11, which operates approximately once every few hours. By coordinating the ash removal device 11 and the corrosion prevention device 12, it is possible to reduce the amount of ash adhering to the heat transfer tubes of the superheater 10 and alternately supply a sulfur compound and hydrogen chloride to the ash near the heat transfer tubes, thereby effectively suppressing corrosion of the heat transfer tubes.

[0024] Hydrogen chloride is known to cause corrosion, and injecting too much hydrogen chloride may actually accelerate corrosion. Furthermore, sulfur compounds are environmentally harmful substances and must be removed in the downstream exhaust gas treatment system 8. By linking the ash removal device 11 and the corrosion prevention device 12 and shortening the operating time of the corrosion prevention device 12, the amounts of hydrogen chloride and sulfur oxides injected can be reduced.

[0025] It is desirable that the corrosion prevention device 12 be able to adjust the amount of hydrogen chloride injected depending on the amount of Cu in the ash. Reference numeral 13 denotes a measuring device that measures the amount of Cu in the ash. The measuring device 13 collects ash adhering to the heat transfer tubes of the superheater 10 or catches fly ash in the convection heat transfer chamber 7 and samples the ash. The sampled ash is sent to an analyzing device (not shown), and the amount of Cu in the ash is calculated. Note that the measuring device 13 may also directly measure the amount of Cu in the ash adhering to the heat transfer tubes of the superheater 10.

[0026] The amount of Cu in the ash measured by the measuring device 13 is sent to the control device 14. The control device 14 controls the corrosion prevention device 12 and adjusts the amount of hydrogen chloride injected depending on the amount of Cu in the ash. For example, the control device 14 increases the amount of hydrogen chloride injected when the amount of Cu in the ash increases, and decreases the amount of hydrogen chloride injected when the amount of Cu in the ash decreases. [Explanation of symbols]

[0027] 3...Waste boiler 6...Radiant heat transfer chamber 7...Convection heat transfer chamber 10…Superheater 11...Ash removal device 12...Corrosion prevention device

Claims

1. A corrosion prevention device for a superheater of a waste boiler, which alternately injects a sulfur compound and hydrogen chloride into the radiant heat transfer chamber and / or the convective heat transfer chamber of the waste boiler equipped with a superheater.

2. 2. The corrosion prevention device for a superheater of a waste boiler according to claim 1, wherein the corrosion prevention device is capable of cooperating with an ash removal device that removes ash adhering to the superheater.

3. 3. The corrosion prevention device for a superheater of a waste boiler according to claim 1, wherein the corrosion prevention device is capable of adjusting the amount of hydrogen chloride injected depending on the amount of Cu in the ash.

4. A method for preventing corrosion of a superheater of a waste boiler, comprising alternately injecting a sulfur compound and hydrogen chloride into a radiant heat transfer chamber and / or a convective heat transfer chamber of the waste boiler equipped with a superheater.

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