Chlorine removal method and chlorine removal system

Abstract

To provide a chlorine removal method that is a simple method of removing deposits generated on a piping for supplying a carbon dioxide-containing gas, thereby preventing the piping from being blocked and achieving stable removal of chlorine components from chloride-containing ashes.SOLUTION: A chlorine removal method is a method of removing chlorine from chloride-containing ashes that includes: a slurry preparation step of blending chloride-containing ashes with water to obtain a primary slurry; a carbon dioxide gas supply step of obtaining a secondary slurry by supplying a carbon dioxide-containing gas to an inside of the primary slurry by using a carbon dioxide gas supply passage for supplying a carbon dioxide-containing gas to an inside of the primary slurry to elute chlorine components involved in chloride-containing ashes to water; and a deposit removal step of removing deposits deposited on an outlet vicinity of the carbon dioxide gas supply passage by circulating an acidic solution in an inside of the outlet vicinity of the carbon dioxide gas supply passage.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a chlorine removal method and system for removing chlorine from chloride-containing ash. [Background technology]

[0002] 2. Description of the Related Art Incineration ash generated during the incineration of municipal waste or industrial waste, and clinker dust generated in cement manufacturing plants, are effectively reused as cement raw materials from the viewpoints of recycling waste materials and protecting the environment. On the other hand, incineration ash, clinker dust, etc. may contain chlorine. Chlorine deteriorates the quality of cement and hinders the normal operation of cement manufacturing equipment, so it is necessary to perform a desalination process on the chloride-containing ash, such as chlorine-containing incineration ash, before using the chloride-containing ash as a raw material for cement. Here, the chlorine in the chloride-containing ash exists as chlorine soluble in water (for example, calcium chloride, potassium chloride, etc.) or chlorine sparingly soluble in water (for example, Friedel's salt, etc.). As a method for efficiently removing water-soluble and poorly water-soluble chlorine from chlorine-containing ash, Patent Document 1 describes a method for treating chlorine-containing ash, which comprises a washing step in which water is added to the chlorine-containing ash and the ash is stirred and washed; a concentrating step in which a polymer coagulant is added to the ash slurry that has undergone this washing step and the slurry is allowed to settle and separate; a first dehydration step in which the concentrated ash slurry discharged from this concentration step is dehydrated using a vacuum belt filter; an advanced desalination step in which the dehydrated cake of ash discharged from this dehydration step is dispersed in water, a carbon dioxide-containing gas is added, and the mixture is heated; and a second dehydration step in which the slurry that has undergone this advanced desalination step is dehydrated using a filter press to produce a washed ash cake.

[0003] Patent Document 2 describes a system for desalination of chlorine-containing ash, which includes a washing tank in which chlorine-containing ash is washed with water, a desalination tank in which the water-washed chlorine-containing ash is desalted, a desalination gas supply means for supplying desalination gas to the desalination tank, and a dehydration washer through which washing water flows to wash the desalted ash slurry discharged from the desalination tank, the desalination gas supply means having a carbon dioxide storage tank and a hydrochloric acid storage tank, and a desalination gas consisting of a mixed gas of hydrogen chloride and carbon dioxide gas at 2 vol% or more and 50 vol% or less is supplied to the desalination tank, and the desalination process of the chlorine-containing ash is performed while suppressing the deposition of scale around the inlet of the desalination gas. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6252653 [Patent Document 2] Patent No. 7234775 Summary of the Invention [Problem to be solved by the invention]

[0005] When a carbon dioxide-containing gas is supplied to a slurry containing chloride-containing ash for the purpose of removing chlorine from the chloride-containing ash, there is a problem that scale (deposits) such as calcium carbonate is formed in the piping for supplying the carbon dioxide-containing gas, resulting in the piping becoming clogged with scale, making stable operation difficult. An object of the present invention is to provide a chlorine removal method and a chlorine removal system which can remove deposits formed in a pipe for supplying a carbon dioxide-containing gas in a simple manner, prevent the pipe from being clogged, and stably remove chlorine from chloride-containing ash. [Means for solving the problem]

[0006] As a result of intensive research into solving the above-mentioned problems, the inventors have found that the above-mentioned object can be achieved by a method including the steps of mixing chloride-containing ash with water to obtain a first slurry, supplying a carbon dioxide-containing gas into the first slurry using a carbon dioxide gas supply channel to leach the chlorine components contained in the chloride-containing ash into the water, and removing deposits adhered to the vicinity of the outlet of the carbon dioxide gas supply channel by circulating an acidic solution inside the vicinity of the outlet of the carbon dioxide gas supply channel, and have completed the present invention. That is, the present invention provides the following [1] to

[10] . [1] A method for removing chlorine from chloride-containing ash, comprising: a slurry preparation step of mixing the chloride-containing ash with water to obtain a first slurry; a carbon dioxide supply step of supplying a carbon dioxide-containing gas into the first slurry using a carbon dioxide supply path for supplying the gas into the first slurry, thereby causing the chlorine component contained in the chloride-containing ash to leach into the water to obtain a second slurry; and an adhesion removal step of removing adhesions adhered to the vicinity of the outlet of the carbon dioxide supply path by circulating an acidic solution inside the vicinity of the outlet of the carbon dioxide supply path.

[0007] [2] The chlorine removal method according to [1], further comprising a solid-liquid separation step of performing solid-liquid separation on the second slurry using a solid-liquid separator to obtain a solid fraction obtained by removing the chlorine components from the chloride-containing ash, and water containing the chlorine components. [3] The method for removing chlorine according to [2] above, further comprising: a washing step of washing the solid-liquid separation apparatus with an acidic washing liquid; and a waste washing liquid recovery step of recovering the washing liquid used for washing the solid-liquid separation apparatus as a waste washing liquid, wherein the waste washing liquid is used as at least a part of the acidic solution in the deposit removal step. [4] The chlorine removal method according to any one of [1] to [3], wherein in the deposit removal step, the flow of the acidic solution is adjusted based on at least one selected from the degree of blockage of the outlet of the carbon dioxide gas supply path, the supply amount of the carbon dioxide-containing gas per unit time, and the pressure of the carbon dioxide-containing gas. [5] The method for removing chlorine according to any one of [1] to [4] above, wherein exhaust gas is used as the carbon dioxide-containing gas.

[0008] [6] A chlorine removal system for removing chlorine from chloride-containing ash, comprising: a slurry tank for containing a first slurry containing the chloride-containing ash and water; a carbon dioxide gas supply line for supplying a carbon dioxide-containing gas into the first slurry to cause the chlorine component contained in the chloride-containing ash to leach into the water to obtain a second slurry; and an acidic solution supply device for removing deposits attached near the outlet of the carbon dioxide gas supply line by circulating an acidic solution inside the carbon dioxide gas supply line near an outlet. [7] The chlorine removal system according to [6], further comprising a solid-liquid separation device for performing solid-liquid separation on the second slurry to obtain a solid fraction obtained by removing chlorine components from the chloride-containing ash, and water containing the chlorine components. [8] The chlorine removal system according to [7], wherein the acidic solution supplying device includes a waste cleaning liquid storage tank for storing the acidic cleaning liquid used for cleaning the solid-liquid separation device as a waste cleaning liquid, and an acidic solution supplying path for supplying the waste cleaning liquid from the waste cleaning liquid storage tank to an inside area near an outlet of the carbon dioxide supplying path. [9] The chlorine removal system according to [8], further comprising a cleaning device having a cleaning liquid storage tank for storing an acidic cleaning liquid for cleaning the solid-liquid separation device and a cleaning liquid supply path for supplying the acidic cleaning liquid to the solid-liquid separation device.

[10] The chlorine removal system according to [9], further comprising a waste cleaning liquid supply line for supplying the waste cleaning liquid to the cleaning liquid storage tank. Effect of the Invention

[0009] According to the chlorine removal method and chlorine removal system of the present invention, it is possible to remove deposits formed in the piping for supplying a carbon dioxide-containing gas in a simple manner, prevent the piping from being blocked, and stably remove chlorine from chloride-containing ash. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram showing an example of a chlorine removal system of the present invention, including a waste cleaning liquid storage tank and a cleaning liquid storage tank. [Diagram 2] FIG. 2 is a schematic diagram illustrating an example of a chlorine removal system of the present invention that includes a waste cleaning solution storage tank and does not include a cleaning solution storage tank. [Diagram 3] FIG. 2 is a schematic diagram showing an example of a chlorine removal system of the present invention that does not include a waste cleaning liquid storage tank and a cleaning liquid storage tank. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The chlorine removal method of the present invention is a method for removing chlorine from chloride-containing ash, and includes a slurry preparation step of mixing chloride-containing ash with water to obtain a first slurry, a carbon dioxide supply step of supplying a carbon dioxide-containing gas into the first slurry using a carbon dioxide supply path for supplying a carbon dioxide-containing gas into the first slurry, thereby leaching the chlorine component contained in the chloride-containing ash into the water to obtain a second slurry, and an adhesion removal step of removing adhesions adhered to the vicinity of the outlet of the carbon dioxide supply path by circulating an acidic solution inside the vicinity of the outlet of the carbon dioxide supply path. Each step will be explained in detail below.

[0012] [Slurry preparation process] This step is a step of mixing chloride-containing ash with water to obtain a first slurry (slurry containing chloride-containing ash and water: slurry before carbonation treatment). Examples of chloride-containing ash that can be treated by the present invention include incineration ash discharged from the bottom of an incineration facility when general waste or industrial waste is burned, and soot and dust in the exhaust gas generated when general waste or industrial waste is burned, which contains chlorides. Specific examples of incineration ash include city waste incineration ash, sludge incineration ash, chicken droppings incineration ash, etc. Specific examples of soot and dust include clinker dust generated in cement factories. The amount of water per 100 parts by mass of chloride-containing ash is preferably 100 to 500 parts by mass, more preferably 120 to 450 parts by mass, and particularly preferably 150 to 400 parts by mass. If the amount is 100 parts by mass or more, the chlorine contained in the chloride-containing ash can be more easily leached into the water. If the amount is 500 parts by mass or less, the equipment can be prevented from becoming excessively large.

[0013] [Carbon dioxide gas supply process] This process is a process in which a carbon dioxide-containing gas is supplied into the first slurry obtained in the slurry preparation process using a carbon dioxide gas supply line for supplying a carbon dioxide-containing gas into the first slurry, thereby leaching the chlorine components contained in the chloride-containing ash into the water, thereby obtaining a second slurry (a slurry after carbonation process containing a solid component obtained by removing the chlorine components from the chloride-containing ash and water (aqueous solution) obtained by leaching the chlorine components). The carbon dioxide-containing gas passes through the carbon dioxide gas supply passage and is supplied into the slurry from an outlet of the carbon dioxide gas supply passage located below the liquid surface of the slurry. Chloride-containing ash contains water-soluble chlorine components such as CaCl2, NaCl, and KCl, as well as poorly water-soluble chlorine components such as Friedel's salt. Although sparingly soluble chlorine components such as Friedel's salt are difficult to leach into water, by supplying a carbon dioxide-containing gas into the slurry, the sparingly soluble chlorine components can be decomposed and chlorine can be leached (dissolved) into the water. The decomposition reaction of Friedel's salt by a carbon dioxide-containing gas (a gas containing carbon dioxide in the form of gas (hereinafter also referred to as "carbon dioxide")) is represented by the following reaction formula. 3CaO Al2O3 CaCl2 10H2O+3CO2→3CaCO3+2Al(OH)3+CaCl2+7H2O

[0014] The carbon dioxide-containing gas may be a gas consisting of only carbon dioxide gas, but from the standpoint of availability and the like, it may be a gas containing carbon dioxide gas and other gases (for example, nitrogen). The ratio of carbon dioxide gas in the carbon dioxide-containing gas is preferably 5% by volume or more, more preferably 10% by volume or more, even more preferably 20% by volume or more, even more preferably 50% by volume or more, even more preferably 80% by volume or more, and particularly preferably 90% by volume or more. If the ratio is 5% by volume or more, the time for leaching chlorine contained in the chloride-containing ash into water can be shortened, and chlorine can be efficiently removed. The supply amount of the carbon dioxide-containing gas per unit time varies depending on the shape of the carbon dioxide gas supply passage, the amount of the slurry, the mass ratio of the chloride-containing ash to water, etc., but is preferably 0.1 to 5 liters / minute, more preferably 0.5 to 4 liters / minute, and particularly preferably 0.8 to 3 liters / minute, per 1 kg of the slurry. If the supply amount is 0.1 liters / minute or more, the time required for the chlorine contained in the chloride-containing ash to be leached into the water can be shortened, and the chlorine can be efficiently removed. If the supply amount is 5 liters / minute or less, excessive supply of the carbon dioxide-containing gas can be prevented.

[0015] Examples of the carbon dioxide-containing gas include liquefied carbon dioxide, exhaust gas, and gas separated and recovered from exhaust gas (carbon dioxide concentration: about 100% by volume). Among these, flue gas is preferred from the viewpoints of ease of availability and of immobilizing carbon dioxide gas contained in the flue gas to reduce the amount of carbon dioxide gas discharged from the flue gas. Examples of exhaust gas include exhaust gas generated in a cement manufacturing process (carbon dioxide concentration: about 20% by volume), exhaust gas generated in an iron and steelmaking process (carbon dioxide concentration: about 20% by volume), exhaust gas generated in a thermal power generation process (carbon dioxide concentration: about 10% by volume), etc. Among them, exhaust gas generated in a cement manufacturing process is preferable from the viewpoint of being able to utilize exhaust gas generated when chloride-containing ash after chlorine removal is reused as a raw material for cement. Examples of exhaust gases generated in the cement manufacturing process include exhaust gases generated in cement kilns and exhaust gases generated in chlorine bypass facilities.

[0016] [Deposit removal process] This step is a step of removing deposits adhering to the vicinity of the outlet of the carbon dioxide gas supply passage by circulating an acidic solution inside the vicinity of the outlet of the carbon dioxide gas supply passage. After starting to supply carbon dioxide-containing gas into the slurry through the carbon dioxide gas supply passage, calcium carbonate and the like produced during decomposition of Friedel's salt adheres to the vicinity of the outlet (the outlet for carbon dioxide-containing gas) of the carbon dioxide gas supply passage as an adhesion. The adhesion blocks the piping (particularly the portion near the outlet) which is the carbon dioxide gas supply passage, making it difficult to stably supply the carbon dioxide-containing gas. In this process, by circulating an acidic solution inside the carbon dioxide gas supply channel near the outlet, it is possible to remove any deposits that have adhered to the carbon dioxide gas supply channel near the outlet and to suppress the formation of deposits near the outlet of the carbon dioxide gas supply channel.

[0017] Examples of the acid contained in the acidic solution include hydrochloric acid (HCl), sulfuric acid (H2SO4), etc. Among them, hydrochloric acid is preferable from the viewpoint of availability and the like. The pH of the acidic solution is preferably 3.0 or less, more preferably 2.8 or less, even more preferably 2.5 or less, still more preferably 2.3 or less, and particularly preferably 1.5 or less. If the pH is 3.0 or less, deposits adhering to the vicinity of the outlet of the carbon dioxide gas supply passage can be removed more efficiently. In this step, a waste cleaning solution, which will be described later, may be used as at least a part of the acidic solution. The flow rate of the acidic solution is preferably an amount sufficient to sufficiently cover the inner wall of the carbon dioxide gas supply channel when the acidic solution flows inside the carbon dioxide gas supply channel near the outlet. The amount of acid solution flowing per unit time varies depending on the shape and cross-sectional area of ​​the carbon dioxide gas supply passage, but is preferably 1 to 20 volume %, more preferably 3 to 15 volume %, and particularly preferably 5 to 10 volume % relative to 100 volume % of the carbon dioxide-containing gas supply per unit time. If the amount is 1 volume % or more, the deposits adhering to the vicinity of the outlet of the carbon dioxide gas supply passage can be removed more efficiently. If the amount is 20 volume % or less, the amount of acid solution can be prevented from becoming excessive.

[0018] This step may be carried out after stopping the supply of the carbon dioxide-containing gas in the carbon dioxide gas supplying step, but is usually carried out simultaneously with the carbon dioxide gas supplying step (while supplying the carbon dioxide-containing gas into the slurry). The flow of the acidic solution may be carried out periodically at any determined time interval and flow rate, but from the viewpoint of efficiently removing the deposits, the flow rate may be adjusted based on at least one selected from the degree of blockage of the carbon dioxide gas supply passage outlet, the supply amount of the carbon dioxide-containing gas per unit time, and the pressure of the carbon dioxide-containing gas. The adjustment of the distribution of the acidic solution includes the adjustment of the timing of the distribution of the acidic solution and the adjustment of the amount of the acidic solution distributed.

[0019] The adjustment using the degree of blockage at the outlet of the carbon dioxide gas supply passage means that the degree of blockage at the outlet of the carbon dioxide gas supply passage is confirmed at any time by calculating the blockage rate or by visual inspection, and the flow of the acidic solution is adjusted. The blockage rate can be calculated using the following formula (1). Blockage rate (%) = area of ​​deposits on the inside of the inner diameter of the carbon dioxide gas supply passage outlet / area of ​​the inside of the inner diameter of the carbon dioxide gas supply passage outlet without deposits × 100 (1) In formula (1), the "area of ​​the deposits" refers to the area of ​​the region to which the deposits are attached out of the area of ​​the inner part of the inner diameter of the carbon dioxide gas supply passage outlet (blowing port) to which the deposits are attached. For example, when the carbon dioxide supply passage is cylindrical (when the outlet of the carbon dioxide supply passage is circular), "the part inside the inner diameter of the carbon dioxide supply passage outlet when no deposits are attached" means "the circular part inside the inner diameter of the carbon dioxide supply passage outlet when no deposits are attached." More specifically, an example of a method for adjusting the blockage rate is to circulate an acidic solution when the blockage rate is equal to or greater than a specific value determined arbitrarily (e.g., 50%), and to not circulate an acidic solution when the blockage rate is less than the specific value determined arbitrarily (e.g., 50%). In this specification, the terms "above a specific value" and "below a specific value" are used for convenience to divide the specification into two categories based on a specific value (threshold value), and therefore can be replaced with the terms "exceeding a specific value" and "below a specific value", respectively.

[0020] An example of adjustment using the supply amount of carbon dioxide-containing gas per unit time is a method in which, when the supply amount of carbon dioxide-containing gas per unit time in a state where no adhesion is present is taken as 100%, an acidic solution is circulated when the ratio of the supply amount of carbon dioxide-containing gas per unit time is equal to or less than a specific value determined arbitrarily (e.g., 50%), and the acidic solution is not circulated when the ratio exceeds the specific value determined arbitrarily (e.g., 50%). An example of adjustment using the pressure of the carbon dioxide-containing gas is a method in which, when the pressure value of the carbon dioxide-containing gas in a state where no adhesion is present is taken as 100%, an acidic solution is circulated when the ratio of the pressure value of the carbon dioxide-containing gas to an arbitrarily determined specific value (e.g., 150%) or more, and when the ratio is less than the arbitrarily determined specific value (e.g., 150%), the acidic solution is not circulated. The pressure of the carbon dioxide-containing gas can be measured, for example, by using a pressure gauge disposed in the carbon dioxide-containing gas supply device.

[0021] [Solid-liquid separation process] After the carbon dioxide gas supplying step, a step may be carried out in which solid-liquid separation is performed on the second slurry using a solid-liquid separator to obtain a solid content obtained by removing chlorine components from the chloride-containing ash, and water containing chlorine components. Examples of the solid-liquid separator include a filter press, a centrifuge, a belt filter, etc. Among them, a solid-liquid separator using a filter cloth such as a filter press or a belt filter is preferred from the viewpoint that the acidic washing solution used for washing the solid-liquid separator can be reused as the acidic solution used in the deposit removal step. The solid fraction obtained by removing chlorine components from the chloride-containing ash in this process has a low chlorine content and can be suitably used as a cement raw material, etc.

[0022] [Cleaning process] This step is an optional step in which the solid-liquid separation device is washed with an acidic washing liquid. An example of the cleaning method is a method in which an acidic cleaning liquid is supplied into the solid-liquid separator to clean the filter cloth and the like of the solid-liquid separator. The acidic cleaning liquid may be any acidic cleaning liquid generally used for cleaning filter cloths such as filter presses and belt filters. From the viewpoint of being able to reuse the cleaning liquid (waste cleaning liquid) after cleaning as an acidic solution to be used in the deposit removal step, it is preferable to use an acidic solution similar to that described above. [Waste cleaning solution recovery process] This step is an optional step that is performed after the washing step, and is a step of recovering the washing liquid used in washing the solid-liquid separation device as a waste washing liquid. The waste washing liquid recovered in this step may be reused as at least a part of the acidic solution used in the above-mentioned deposit removal step. In cases where the recovered waste cleaning liquid has a pH value exceeding 3.0 or is insufficient in amount, making it difficult to use the waste cleaning liquid as is as the acidic solution, the waste cleaning liquid may be appropriately mixed with another acidic solution (e.g., HCl) and the like, and then used as the acidic solution.

[0023] Hereinafter, an example of a chlorine removal system for carrying out the above-mentioned chlorine removal method will be specifically described with reference to Figs. 1 to 3. FIG. 1 is a schematic diagram of a chlorine removal system 1 for removing chlorine from chloride-containing ash, comprising a waste scrubbing liquid reservoir 7 and a scrubbing liquid reservoir 9. The slurry tank 2 contains a slurry 16 containing chloride-containing ash and water. The slurry 16 is prepared in advance by mixing a chlorine-containing material with water using a mixing means (not shown) such as an agitator. The prepared slurry (first slurry: slurry before carbonation treatment) passes through a slurry supply passage 13 and is contained in the slurry tank 2 for containing the slurry 16 containing chloride-containing ash and water. In order to efficiently leach chlorine into the water, a mixing means (not shown) such as an agitator may be provided in the slurry tank 2. In addition, after the chlorine-containing material and water are charged into the slurry tank 2, the chlorine-containing material and water may be mixed using a mixing means (not shown) such as a stirring blade to prepare a slurry 16 containing chloride-containing ash and water.

[0024] A carbon dioxide gas supply line 3 is provided in the slurry tank 2 to supply a carbon dioxide-containing gas into the slurry 16, thereby leaching the chlorine contained in the chloride-containing ash into the water and removing the chlorine from the chloride-containing ash. The carbon dioxide gas supply line is usually a tubular member. The carbon dioxide-containing gas is supplied from a carbon dioxide-containing gas supplying device 4 through a carbon dioxide gas supplying passage 3 and from an opening (outlet) at the end of the carbon dioxide gas supplying passage 3 into the slurry 16 . By supplying a carbon dioxide-containing gas into the slurry 16, the chlorine contained in the chloride-containing ash can be leached into the water to obtain a second slurry (slurry after carbonation treatment). The carbon dioxide gas supply passage 3 is disposed so that the opening (outlet) is located below the liquid surface of the slurry 16.

[0025] The second slurry (a slurry containing solids obtained by removing chlorine components from chloride-containing ash and water resulting from leaching of the chlorine components) obtained by supplying a carbon dioxide-containing gas into the slurry 16 is supplied to the solid-liquid separation device 6 through the slurry discharge line 14. In the solid-liquid separator 6, the second slurry is separated into a solid component obtained by removing chlorine components from the chloride-containing ash, and water containing chlorine components. The solid content is discharged through a solid content discharge channel 15 and is reused as a raw material for cement, etc. The water is discharged through a liquid content discharge channel (not shown).

[0026] The cleaning device 11 has a cleaning liquid storage tank 9 for storing an acidic cleaning liquid 18 for cleaning the filter cloth of the solid-liquid separation device 6, and a cleaning liquid supply path 10 for supplying the acidic cleaning liquid 18 to the solid-liquid separation device 6. When the solid-liquid separation ability of the solid-liquid separator is reduced, for example, when solids adhere to the filter cloth, the solid-liquid separator 6 is appropriately washed with a washing liquid supplied through a washing liquid supply passage 10. The acidic washing liquid used for washing the solid-liquid separator 6 is discharged (recovered) as a waste washing liquid through a waste washing liquid discharge passage 12, and then stored in a waste washing liquid storage tank 7. The acidic solution supplying device 5 has a waste cleaning liquid storage tank 7 for storing the acidic cleaning liquid used for cleaning the solid-liquid separation device 6 as a waste cleaning liquid 17, and an acidic solution supplying path 8 for supplying the waste cleaning liquid 17 from the waste cleaning liquid storage tank 7 to the inside near the outlet of the carbon dioxide gas supplying path 3 as at least a part of the acidic solution. The acidic solution supplying device 5 may have a supply path (not shown) for supplying an acidic solution to at least one of the waste cleaning liquid storage tank 7 and the acidic solution supply path 8 when the pH of the waste cleaning liquid 17 exceeds 3.0 or when the amount of the waste cleaning liquid is insufficient. The waste cleaning liquid supply path 19 is arranged so as to branch off from the acid solution supply path 8, and serves to supply a part of the acid solution (waste cleaning liquid) flowing through the acid solution supply path 8 to the cleaning liquid storage tank 9. The waste cleaning liquid introduced through the waste cleaning liquid supply path 19 can be used as the cleaning liquid 18. 1, the waste cleaning liquid supply path 19 branches off from the acidic solution supply path 8, but a waste cleaning liquid supply path may be provided separately from the acidic solution supply path 8 so that the waste cleaning liquid can be directly introduced from the waste cleaning liquid storage tank 7 into the cleaning liquid storage tank 9. The waste cleaning liquid supply path 19 is an optional component.

[0027] FIG. 2 is a schematic diagram of a chlorine removal system 101 for removing chlorine from chloride-containing ash, including a waste scrubbing liquid reservoir 107 and no scrubbing liquid reservoir. The slurry tank 102, the carbon dioxide gas supply passage 103, the carbon dioxide-containing gas supply device 104, the solid-liquid separation device 106, the waste washing liquid discharge passage 110, the slurry supply passage 111, the slurry discharge passage 112, the solid content discharge passage 113, and the slurry containing chloride-containing ash and water 114 are similar to the slurry tank 2, the carbon dioxide gas supply passage 3, the carbon dioxide-containing gas supply device 4, the solid-liquid separation device 6, the waste washing liquid discharge passage 12, the slurry supply passage 13, the slurry discharge passage 14, the solid content discharge passage 15, and the slurry containing chloride-containing ash and water 16 in Figure 1, respectively. In FIG. 2, the acidic solution supplying device 105 includes a waste cleaning liquid storage tank 107 for storing the acidic cleaning liquid used for cleaning the solid-liquid separation device 106 as a waste cleaning liquid 115, an acidic solution supplying path 108 for supplying the waste cleaning liquid 115 from the waste cleaning liquid storage tank 107 to the inside near the outlet of the carbon dioxide gas supplying path 103 as at least a part of the acidic solution, and a cleaning liquid supplying path 109 for supplying the waste cleaning liquid 115 to the solid-liquid separation device 106 as a cleaning liquid. In the chlorine removal system 101, the acidic solution supplying device 105 also serves as a cleaning device for the solid-liquid separation device. The acidic solution supplying device 105 may have a supply path (not shown) for supplying an acidic solution to at least one of the waste cleaning liquid storage tank 107 and the acidic solution supply path 108 when the pH of the waste cleaning liquid 115 exceeds 3.0 or when the amount of the waste cleaning liquid is insufficient.

[0028] FIG. 3 is a schematic diagram of a chlorine removal system 201 for removing chlorine from chloride-containing ash that does not include a waste wash solution reservoir and a wash solution reservoir. The slurry tank 202, the carbon dioxide gas supply passage 203, the carbon dioxide-containing gas supply device 204, the solid-liquid separator 206, the slurry supply passage 208, the slurry discharge passage 209, the solid discharge passage 210, and the slurry containing chloride-containing ash and water 212 are similar to the slurry tank 2, the carbon dioxide gas supply passage 3, the carbon dioxide-containing gas supply device 4, the solid-liquid separator 6, the slurry supply passage 13, the slurry discharge passage 14, the solid discharge passage 15, and the slurry containing chloride-containing ash and water 16 in Figure 1, respectively. In FIG. 3, the acid solution supplying device 205 has an acid solution storage tank 211 for storing an acid solution 213, and an acid solution supplying channel 207 for supplying the acid solution from the acid solution storage tank 211 to the inside near the outlet of the carbon dioxide gas supplying channel 203. EXAMPLES

[0029] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. [Example 1] 200 g of municipal waste incineration ash generated from a waste incineration plant and 300 g of tap water were placed in a beaker and stirred using a stirrer to prepare a slurry containing chloride-containing ash and water (first slurry: slurry before carbonation treatment). A SUS pipe (stainless steel pipe) with an inner diameter of 5 mm was installed so that the end portion (the outlet of the carbon dioxide-containing gas) of the SUS pipe was below the liquid surface of the slurry, and a carbon dioxide-containing gas with a carbon dioxide (carbonic acid gas) content of 100% by volume was supplied into the slurry for 2 hours using the SUS pipe to obtain a carbonation-treated slurry (second slurry). The supply amount of carbon dioxide gas per unit time was set to 500 ml / min. After the carbon dioxide gas was supplied, the SUS pipe was removed, and the clogging rate of the end portion (outlet) of the SUS pipe was calculated using the following formula. Blockage rate (%) = Area of ​​the circular part of the inside diameter of the stainless steel pipe outlet with deposits / Area of ​​the circular part of the inside diameter of the stainless steel pipe outlet without deposits × 100 After measuring the clogging rate, dilute hydrochloric acid (5% hydrochloric acid concentration: pH 1.0 or less) was passed through the SUS tube at a supply rate of 35 ml / min for 3 minutes while supplying carbon dioxide gas through the SUS tube. After passing the dilute hydrochloric acid, the SUS tube was removed and the clogging rate of the SUS tube was calculated in the same manner. In addition, the removal rate was calculated by subtracting the clogging rate after the dilute hydrochloric acid was passed through from the clogging rate before the dilute hydrochloric acid was passed through.

[0030] [Example 2] The clogging rate of the SUS pipe was measured in the same manner as in Example 1, except that a waste washing liquid (pH 2.0 or less) generated when a filter cloth of a solid-liquid separator (filter press) was washed with dilute hydrochloric acid (hydrochloric acid concentration 5%) was used instead of dilute hydrochloric acid. [Comparative Example 1] The clogging rate of the SUS pipe after the carbon dioxide gas was supplied was calculated in the same manner as in Example 1, except that dilute hydrochloric acid was not circulated through the SUS pipe. [Comparative Example 2] The clogging rate and other parameters of the SUS pipe were measured in the same manner as in Example 1, except that tap water was used instead of dilute hydrochloric acid. The results are shown in Table 1.

[0031] [Table 1]

[0032] From Table 1, it can be seen that the removal rates of Examples 1 and 2 (88-90%) are greater than the removal rate of Comparative Example 2 (39%), and that Examples 1 and 2 are able to remove deposits formed on the piping for supplying a carbon dioxide-containing gas and prevent the piping from becoming clogged. [Explanation of symbols]

[0033] 1,101,201 Chlorine removal system 2,102,202 Slurry tank 3,103,203 Carbon dioxide supply line 4,104,204 Carbon dioxide-containing gas supply device 5,105,205 Acidic solution supply equipment 6,106,206 Solid-liquid separation equipment 7,107 Waste cleaning fluid storage tank 8,108,207 Acidic solution supply path 9. Cleaning fluid storage tank 10,109 Cleaning fluid supply path 11 Cleaning equipment 12,110 Waste cleaning fluid discharge passage 13,111,208 Slurry supply line 14,112,209 Slurry discharge channel 15,113,210 Solids discharge channel 16,114,212 Slurry (slurry containing chloride-containing ash and water) 17,115 Waste cleaning fluid 18 Cleaning Solution 19 Waste cleaning fluid supply line 211 Acid solution storage tank 213 Acid Solution

Claims

1. 1. A method for removing chlorine from chloride-containing ash, comprising: a slurry preparation step of mixing the chloride-containing ash with water to obtain a first slurry; a carbon dioxide gas supplying step of supplying a carbon dioxide gas containing gas into the first slurry using a carbon dioxide gas supplying line for supplying the carbon dioxide gas into the first slurry, thereby leaching the chlorine component contained in the chloride-containing ash into the water to obtain a second slurry; an adhesion removing step of removing adhesions adhered to the vicinity of the outlet of the carbon dioxide gas supply passage by circulating an acidic solution through the inside of the vicinity of the outlet of the carbon dioxide gas supply passage; A method for removing chlorine, comprising:

2. 2. The method for removing chlorine according to claim 1, further comprising a solid-liquid separation step of performing solid-liquid separation on the second slurry using a solid-liquid separation device to obtain a solid fraction obtained by removing the chlorine components from the chloride-containing ash, and water containing the chlorine components.

3. a cleaning step of cleaning the solid-liquid separation device with an acidic cleaning solution; A waste cleaning liquid recovery step of recovering the cleaning liquid used for cleaning the solid-liquid separation device as a waste cleaning liquid, 3. The method for removing chlorine according to claim 2, wherein the waste cleaning liquid is used as at least a part of the acidic solution in the deposit removing step.

4. 2. The chlorine removal method according to claim 1, wherein in the deposit removal step, the flow of the acidic solution is adjusted based on at least one selected from the degree of blockage of the outlet of the carbon dioxide gas supply passage, the supply amount of the carbon dioxide-containing gas per unit time, and the pressure of the carbon dioxide-containing gas.

5. 2. The method for removing chlorine according to claim 1, wherein exhaust gas is used as the carbon dioxide-containing gas.

6. 1. A chlorine removal system for removing chlorine from chloride-containing ash, comprising: the chlorine removal system comprising: a slurry vessel for containing a first slurry comprising the chloride-containing ash and water; a carbon dioxide gas supply line for supplying a carbon dioxide-containing gas into the first slurry to cause the chlorine component contained in the chloride-containing ash to leach into the water to obtain a second slurry; A chlorine removal system comprising an acid solution supply device for removing deposits adhering to the vicinity of the outlet of the carbon dioxide gas supply line by circulating an acid solution inside the vicinity of the outlet of the carbon dioxide gas supply line.

7. The chlorine removal system according to claim 6, further comprising a solid-liquid separation device for performing solid-liquid separation on the second slurry to obtain a solid fraction obtained by removing chlorine components from the chloride-containing ash, and water containing the chlorine components.

8. a waste cleaning liquid storage tank for storing the acidic cleaning liquid used by the acidic solution supply device for cleaning the solid-liquid separation device as a waste cleaning liquid; 8. The chlorine removal system according to claim 7, further comprising an acid solution supply passage for supplying the waste cleaning liquid from the waste cleaning liquid storage tank to an inside of the carbon dioxide gas supply passage near an outlet thereof.

9. 9. The chlorine removal system according to claim 8, further comprising a cleaning device having a cleaning liquid storage tank for storing an acidic cleaning liquid for cleaning the solid-liquid separation device, and a cleaning liquid supply path for supplying the acidic cleaning liquid to the solid-liquid separation device.

10. 10. The chlorine removal system according to claim 9, further comprising a waste cleaning liquid supply line for supplying the waste cleaning liquid to the cleaning liquid storage tank.

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