Methods for treatment to remove chlorine-containing powder salts.

Abstract

Invention details;

Description

Method for desalination of chlorine-containing powder

[0001] The present invention relates to a desalination method for reducing the chlorine content of chlorine-containing powder such as incineration ash.

[0002] Ash generated during the incineration of municipal solid waste (MSW) such as general waste and industrial waste, and clinker dust generated from cement plants, are being effectively reused as cement raw materials from the perspective of resource conservation and environmental protection. However, these materials contain a large amount of chlorine, which can interfere with cement quality and the normal operation of cement manufacturing equipment. Therefore, they require desalination treatment before being used as cement raw materials. This process requires a large amount of wash water, and reducing this consumption has been an issue.

[0003] In relation to such problems, for example, Patent Document 1 (JP 2003-211129 A) discloses a method for washing ash in multiple stages, each stage comprising a mixer for mixing ash and water and a solid-liquid separator for separating the mixture from the mixer into ash and water, washing the ash in multiple stages, countercurrently flowing the ash and water, and dehydrating the ash separated into solid and liquid in the first-stage solid-liquid separator until the moisture content of the wet ash is less than 60%. It is claimed that this method enables efficient desalting from the ash using a small amount of washing water (paragraph 0021 of Patent Document 1).

[0004] Furthermore, for example, Patent Document 2 (JP 2005-246295 A) discloses an incineration ash treatment device that has multiple stages of drum filters for washing incineration ash, supplies new washing water to the final stage, and uses the recovered washing water sucked and recovered in each stage as washing water for the previous stage in order to wash the incineration ash sent from the first stage to the final stage, characterized in that the drum filters in each stage are equipped with recovered washing water supply means that supplies a portion of the recovered washing water sucked and recovered by the drum filters to the mixture held on the outer periphery of the filters at a position upstream of the washing water supply position of the corresponding stage in the drum rotation direction. Furthermore, it is claimed that, while achieving the same washing effect as conventional devices, the number of drum filter stages can be reduced, thereby reducing the amount of water used (paragraph 0014 of Patent Document 2).

[0005] Japanese Patent Application Laid-Open No. 2003-211129 Japanese Patent Application Laid-Open No. 2005-246295

[0006] In the above Patent Documents 1 and 2, when a chlorine-containing powder such as incineration ash is desalted, washing water is added to the powder to dissolve the chlorine into a liquid phase, and the resulting desalted cake is dewatered. In order to efficiently remove the chlorine remaining as a residue in the water content of the cake, multi-stage washing devices are provided to remove the residual chlorine, thereby reducing the amount of water used.

[0007] However, according to the findings of the present inventors, when washing a desalted cake by providing washing devices in multiple stages as in Patent Documents 1 and 2, there is a problem in that water consumption increases for washing residual dust adhering to the filter cloth and the device itself, making it impossible to suppress the amount of water consumption in the entire system.

[0008] Therefore, an object of the present invention is to provide a method for desalination of chlorine-containing powder that can effectively reduce the amount of water used in the entire system.

[0009] In order to achieve the above object, the present invention provides a method for producing a slurry by mixing a chlorine-containing powder with a first desalting wash liquid, a chlorine eluting step of eluting chlorine contained in the chlorine-containing powder in the slurry into a liquid phase, a desalted cake forming step of obtaining a first desalted cake and a first filtrate by dewatering the slurry from which the chlorine has been eluted, a first desalted cake washing step of washing the first desalted cake with a second desalting wash liquid different from the first desalting wash liquid to obtain a second desalted cake and a second filtrate, and a second desalted cake washing step of washing the second desalted cake with a third desalting wash liquid different from the first and second desalting wash liquids to obtain a third desalted cake and a third filtrate, the slurrying step, the chlorine eluting step, the desalted cake forming step, the first desalted cake washing step, and the second desalted cake washing step are repeated for each chlorine-containing powder to be supplied, and at least a part of the third filtrate obtained in the second desalted cake washing step is recovered and stored and reused as the second desalting wash liquor for the first desalted cake washing step, the third desalting wash liquor for the second desalted cake washing step, or both, corresponding to the chlorine-containing powder to be supplied subsequently, and after being reused one or more times, the third filtrate is recycled and reused as the first desalting wash liquor.

[0010] According to the above-described method for desalting a chlorine-containing powder, the chlorine-containing powder is mixed with a first desalting wash liquid to form a slurry, chlorine contained in the chlorine-containing powder is eluted into the liquid phase of the slurry, and the slurry is dewatered to obtain a first desalted cake and a first filtrate. The first desalted cake is washed with a second desalting wash liquid separate from the first desalting wash liquid to obtain a second desalted cake and a second filtrate. The second desalted cake is further washed with a third desalting wash liquid separate from the first and second desalting wash liquids to obtain a third desalted cake and a third filtrate. This provides a third desalted cake from which chlorine has been sufficiently removed. This method is therefore useful for converting chlorine-containing incineration ash and the like into a cement raw material. Furthermore, at least a portion of the third filtrate obtained in the second desalted cake washing step is recovered and stored, and therefore can be reused as a desalting wash liquid suitable for the chlorine-containing powder supplied to a subsequent stage, eliminating the need for multiple stages of desalted cake washing equipment. After one or more reuses, the washed solution is recycled as the first desalination wash solution, so that the amount of water used in the entire system can be reduced while maintaining the desalination effect of the desalination treatment of the chlorine-containing powder. Furthermore, the reduction in the amount of water used can suppress the amount of heavy metal elution.

[0011] In order to achieve the above object, secondly, the present invention provides the above-mentioned desalting method for chlorine-containing powder, wherein the desalting cake forming step, the first desalting cake washing step, and the second desalting cake washing step are carried out in a solid-liquid separator utilizing a filter cloth, and at least a part of filter cloth washing wastewater obtained when washing the filter cloth is recycled and reused as the second desalting wash liquid, the third desalting wash liquid, or both.

[0012] According to the above-mentioned configuration, since a solid-liquid separator utilizing a filter cloth is used, it is possible to efficiently form a desalted cake from the slurry and wash it thereafter over a large volume of chlorine-containing powder supplied. Furthermore, in order to prevent clogging of the filter cloth of the solid-liquid separator used, constant washing is required throughout the operation period of the apparatus. However, since the washing wastewater is recycled and reused as the second desalting wash liquid, the third desalting wash liquid, or both, the amount of water used in the entire system can be further reduced.

[0013] In order to achieve the above object, the present invention thirdly provides the desalination method for chlorine-containing powder according to the second aspect, wherein the solid-liquid separator is a filter press or a belt filter.

[0014] According to the above configuration, an existing device system can be used as the solid-liquid separation device.

[0015] In order to achieve the above object, the present invention fourthly provides the desalination method for a chlorine-containing powder according to the second aspect, wherein the solid-liquid separation device is a filter press, and at least a part of the filter cloth washing wastewater is subjected to solid-liquid separation, and the resulting liquid part is recycled and reused as the second desalination wash liquid, the third desalination wash liquid, or both.

[0016] According to the above configuration, an existing system can be used as a solid-liquid separation device using a filter cloth. Furthermore, a filter press is a device capable of cake washing, and a typical cake washing mechanism involves passing water through the non-filtering side of the filter cloth. Therefore, using the filter cloth washing wastewater containing solids directly as cake wash water (using it as the wash liquid for the second and third desalination steps) can cause clogging of the filter cloth. Therefore, by subjecting the filter cloth washing wastewater to solid-liquid separation, it can be used favorably as the wash liquid for the second and third desalination steps.

[0017] In order to achieve the above object, the present invention fifthly provides the above-mentioned desalting method for a chlorine-containing powder, wherein the desalting cake forming step, the first desalting cake washing step, and the second desalting cake washing step are carried out in a solid-liquid separator utilizing a filter cloth, and at least a part of filter cloth washing wastewater obtained when washing the filter cloth is recycled and reused as the first desalting wash liquid.

[0018] According to the above-mentioned configuration, since a solid-liquid separator utilizing a filter cloth is used, it is possible to efficiently form a desalted cake from the slurry and then wash it over a large volume of supplied chlorine-containing powder. Furthermore, in order to prevent clogging of the filter cloth of the solid-liquid separator used, constant washing is required throughout the operation of the apparatus. However, since the washing wastewater is recycled and reused as the first desalting wash liquid, the amount of water used in the entire system can be further reduced.

[0019] To achieve the above object, the present invention sixthly provides the above-mentioned desalting method for chlorine-containing powder, wherein when the third filtrate obtained in the second desalting cake washing step is reused, whether or not the reuse is acceptable is determined by observing any one or more of the following (1) to (5) in a storage tank in which at least a portion of the third filtrate is recovered and stored: (1) Total time spent in the reuse treatment using the third filtrate, (2) Total amount of water reused using the third filtrate, (3) pH of the third filtrate, (4) Cl ion concentration of the third filtrate, and (5) Electrical conductivity of the third filtrate.

[0020] According to the above configuration, when the third filtrate is reused, it is possible to avoid using a washing liquid that is inappropriate for washing the desalted cake.

[0021] In order to achieve the above object, in a seventh aspect, the present invention provides the above-mentioned desalting method for a chlorine-containing powder, wherein at least a part of the second filtrate obtained in the first desalting cake washing step is recovered and stored, and reused as the second desalting wash liquid for the first desalting cake washing step corresponding to the chlorine-containing powder to be supplied to a subsequent stage, and after being reused one or more times, the second filtrate is recycled and reused as the first desalting wash liquid.

[0022] According to the above-mentioned configuration, the second filtrate obtained in the first desalted cake washing step is also reused, thereby ensuring a reduction in the amount of water used in the entire system. Furthermore, since at least a portion of the second filtrate is recovered and stored, it can be reused as a desalting wash liquid corresponding to the chlorine-containing powder supplied to the subsequent step, even without providing multiple stages of devices for washing the desalted cake.

[0023] To achieve the above object, the present invention provides, in an eighth aspect, the method for desalting a chlorine-containing powder according to claim 7, wherein, when the second filtrate obtained in the first desalting cake washing step is reused, whether or not the second filtrate can be reused is determined by observing any one or more of the following (1) to (5) in a storage tank in which at least a portion of the second filtrate is recovered and stored: (1) A total time spent reusing the second filtrate, (2) A total amount of water reusing the second filtrate, (3) A pH of the second filtrate, (4) A chloride ion concentration of the second filtrate, and (5) An electrical conductivity of the second filtrate.

[0024] According to the above configuration, when the second filtrate is reused, it is possible to avoid using a washing liquid that is inappropriate for washing the desalted cake.

[0025] In order to achieve the above object, in a ninth aspect, the present invention provides the above-mentioned method for desalting a chlorine-containing powder, wherein in the first desalting cake washing step, washing of the first desalted cake with the second desalting wash liquid is performed a plurality of times with the second desalting wash liquid, and / or in the second desalting cake washing step, washing of the second desalted cake with the third desalting wash liquid is performed a plurality of times with the third desalting wash liquid.

[0026] According to the above configuration, the desalting process can be reliably carried out by washing the cake multiple times.

[0027] In order to achieve the above object, in a tenth aspect, the present invention provides the above-mentioned desalination method for chlorine-containing powder, wherein the amount of water used is 1.5 to 4 parts by mass per part by mass of the dry weight of the chlorine-containing powder to be desalted.

[0028] According to the above-mentioned configuration, the amount of water used in the desalination process of chlorine-containing powder such as incineration ash can be significantly reduced. Furthermore, the reduction in the amount of water used can suppress the amount of heavy metal elution.

[0029] In order to achieve the above object, in an eleventh aspect, the present invention provides the above-mentioned desalting method for chlorine-containing powder, wherein the desalting cake forming step, the first desalting cake washing step, and the second desalting cake washing step are carried out in a single solid-liquid separator.

[0030] The above configuration simplifies the device configuration, thereby reducing initial and running costs, and also minimizes the amount of water used to wash off residual dust adhering to the filter cloth and the device itself.

[0031] 2A shows an embodiment of a method for desalting chlorine-containing powder according to the present invention. It is a flow chart illustrating an embodiment in which washing in the desalting cake washing step is performed multiple times with a desalting wash liquid in one example of the method for desalting chlorine-containing powder according to the present invention. Fig. 2A shows an embodiment in which washing of the second desalted cake with the third desalting wash liquid is performed multiple times with the third desalting wash liquid. Fig. 2B shows an embodiment in which washing of the first desalted cake with the second desalting wash liquid is performed multiple times with the second desalting wash liquid. Fig. 2C shows an embodiment in which both washing with the second desalting wash liquid multiple times and washing with the third desalting wash liquid multiple times are performed. It is a flow chart illustrating an embodiment in another example of the method for desalting chlorine-containing powder according to the present invention, in which the desalting cake forming step, the first desalting cake washing step, and the second desalting cake washing step are performed in a single solid-liquid separation device. 9A is a flow chart illustrating an embodiment of another example of a method for desalting chlorine-containing powder according to the present invention, in which the desalted cake forming step, the first desalted cake washing step, and the second desalted cake washing step are performed in a single solid-liquid separator, and the solid-liquid separator uses a filter cloth.

[0034] FIG. 9B is a flow chart illustrating an embodiment of Comparative Examples 1 to 7 performed in Test Example 1.

[0035] FIG. 9C is a flow chart illustrating an embodiment of Examples 1 to 5 performed in Test Example 1.

[0036] FIG. 9D is a flow chart illustrating an embodiment of Example 6 performed in Test Example 1.

[0037] FIG. 9C is a flow chart illustrating an embodiment of Example 6 performed in Test Example 1.

[0038] FIG. 9D is a flow chart illustrating an embodiment of Example 6 performed in Test Example 1.

[0039] FIG. 9E is a flow chart illustrating an embodiment of Example 6 performed in Test Example 1.

[0039] FIG. 9F is a flow chart illustrating an embodiment of Example 6 performed in Test Example 1.

[0039] FIG. 9G is a flow chart illustrating an embodiment of Example 6 performed in Test Example 1.

[0039] FIG. 9H ...10A is a flow chart illustrating an embodiment of Example 6 performed in Test Example 1.

[0039] 1 is a graph showing the relationship between the difference obtained by dividing the chlorine concentration of a desalted cake by the new water ratio, obtained as a result of Test Example 1, and the corresponding new water ratio, obtained by subtracting the value of an Example from the value of a Comparative Example at the same new water ratio.

[0032] The target of the desalination treatment method for chlorine-containing powder according to the present invention is not particularly limited, as long as it is a powder containing chlorine. Examples include incineration fly ash, molten fly ash, and chlorine bypass dust. These are wastes that have traditionally been effectively utilized as cement raw materials after desalination treatment. Typical municipal waste incineration fly ash, i.e., fly ash generated during the incineration of household waste ("incineration fly ash"), generally contains chlorine (Cl) at a concentration of approximately 10% to 30% by mass. Furthermore, fly ash generated from a gasification melting furnace ("molten fly ash") generally contains chlorine at a concentration of approximately 10% to 40% by mass. Meanwhile, chlorine bypass dust, which is dust contained in cement kiln bleed gas, generally contains chlorine at a concentration of approximately 10% to 40% by mass.

[0033] According to the method for desalination of chlorine-containing powder of the present invention, the chlorine concentration of the chlorine-containing powder can be reduced to about 3% by mass or less, more typically about 2% by mass or less, and the powder can be effectively used, for example, as a cement raw material. The chlorine concentration of the chlorine-containing powder can be measured by well-known methods, such as potentiometric titration according to JIS A 1154 "Test method for chloride ions contained in hardened concrete," ion chromatography, and the fundamental parameter method using X-ray fluorescence analysis.

[0034] The present invention will be described in more detail below with reference to the drawings.

[0035] FIG. 1 shows a flow diagram illustrating one embodiment of the method for desalination of chlorine-containing powder according to the present invention.

[0036] As shown in this embodiment, the method for desalting a chlorine-containing powder according to the present invention comprises: a slurrying step of mixing a chlorine-containing powder with a first desalting wash liquid to form a slurry; a chlorine eluting step of eluting chlorine contained in the chlorine-containing powder into a liquid phase in the slurry; a desalted cake forming step of obtaining a first desalted cake and a first filtrate by dewatering the slurry from which chlorine has been eluted; a first desalted cake washing step of washing the obtained first desalted cake with a second desalting wash liquid different from the first desalting wash liquid to obtain a second desalted cake and a second filtrate; and a second desalted cake washing step of washing the obtained second desalted cake with a third desalting wash liquid different from the first and second desalting wash liquids to obtain a third desalted cake and a third filtrate.

[0037] Mixing the chlorine-containing powder with the first desalting wash liquid to form a slurry and dissolving the chlorine contained in the chlorine-containing powder into the liquid phase in the slurry can be carried out using a predetermined dissolution tank or the like known to those skilled in the art. Dehydrating the slurry and adding the desalting wash liquid to the desalted cake formed by dehydration to wash it can be carried out using a predetermined mixing tank or dehydration device or the like known to those skilled in the art. Transferring the slurry or liquid can be carried out using a fluid supply device / supply tank, fluid supply pipe, predetermined storage tank or the like known to those skilled in the art.

[0038] The above-mentioned slurrying step, chlorine elution step, desalting cake forming step, first desalting cake washing step, and second desalting cake washing step are repeated for each chlorine-containing powder supplied (repeated in the first, second, and third stages in FIG. 1 ). At this time, at least a portion of the third filtrate obtained in the second desalting cake washing step is recovered and stored, and reused as a desalting wash liquid corresponding to the chlorine-containing powder supplied to the subsequent stage. More specifically, the third filtrate is reused as the second desalting wash liquid for the first desalting cake washing step, the third desalting wash liquid for the second desalting cake washing step, or both. After the third filtrate has been reused once or multiple times, it is recycled and reused as the first desalting wash liquid.

[0039] Here, the "chlorine-containing powder to be supplied to a subsequent stage" means that the chlorine-containing powder is different from the chlorine-containing powder that has been present in the same process earlier in time. Thus, for example, in the embodiment shown in Fig. 1, desalination treatment is repeated in the first, second, and third stages in chronological order, and the third filtrate from the first stage is reused in the second stage, but this filtrate may be reused as the second desalination washing liquid, the third desalination washing liquid, or both, corresponding to the chlorine-containing powder to be supplied to the third stage or thereafter.

[0040] Furthermore, the desalted cake washing step in which the formed desalted cake is further washed is divided into first and second steps in the order of the process time of the treatment, but it may be further divided into multiple steps, and further desalted cake washing steps may be provided corresponding to these steps, for example, a third desalted cake washing step, a fourth desalted cake washing step, a fifth desalted cake washing step, and subsequent desalted cake washing steps, etc. In this case, it is preferable that the filtrate from a desalted cake washing step assigned an arbitrary number is numbered in the order of the process time for the chlorine-containing powder supplied to the subsequent step, and is reused in a desalted cake washing step assigned the same number or an earlier number.

[0041] In the embodiment shown in Fig. 1, at least a portion of the second filtrate obtained in the first desalting cake washing step is also recovered and stored, and is reused as a second desalting wash liquid for the first desalting cake washing step corresponding to the chlorine-containing powder supplied to a subsequent stage. After the second filtrate is reused once or a plurality of times, it is recycled and reused as the first desalting wash liquid.

[0042] Here, as described above, the "chlorine-containing powder supplied to a subsequent stage" means a powder different from the chlorine-containing powder present in the same step earlier in time. Therefore, for example, in the embodiment shown in FIG. 1 , the second filtrate from the first stage is reused in the second stage, but this filtrate may be reused as a second desalting wash liquid corresponding to the chlorine-containing powder supplied to the third stage or thereafter. The desalting cake washing step may be further provided in multiple stages, such as a third desalting cake washing step. Even in this case, the first step of washing the desalted cake formed by dehydrating the slurry is the first desalting cake washing step, and the desalting wash liquid used therein is the second desalting wash liquid.

[0043] In the method for desalting a chlorine-containing powder according to the present invention, the reuse of the second filtrate is not an essential component. In the embodiment shown in Fig. 1, the first filtrate obtained in the desalting cake forming step is treated as wastewater, but it can also be reused as the first desalting wash liquid corresponding to the chlorine-containing powder to be supplied to a subsequent stage, if necessary.

[0044] In the embodiment shown in Fig. 1, fresh water is used as the desalination wash liquid in the first-stage desalination treatment of the chlorine-containing powder, which means water newly supplied to the system. This fresh water may be water other than seawater, such as industrial water (fresh water), or chlorine-containing water to which a chloride ion concentration adjuster such as NaCl or KCl has been added as needed to adjust the chloride ion concentration. However, in areas where a large amount of industrial water (fresh water) cannot be used or where the use of industrial water (fresh water) is restricted due to cost or other reasons, it is convenient to dilute seawater with industrial water (fresh water) before use.

[0045] Although the chloride ion concentration of the desalting wash liquid introduced into the system may increase with reuse, it is preferable to keep it within a range of 3% by mass to 15% by mass for the first desalting wash liquid, 0.5% by mass to 6% by mass for the second desalting wash liquid, and 0% by mass to 2% by mass for the third desalting wash liquid.

[0046] Fig. 2 shows an embodiment of the desalting method for chlorine-containing powder according to the present invention, in which the desalting cake is washed multiple times with the desalting wash liquid. That is, in the desalting method according to the present invention, for example, as shown in Fig. 2A, the second desalting cake may be washed multiple times with the third desalting wash liquid. Alternatively, as shown in Fig. 2B, the first desalting cake may be washed multiple times with the second desalting wash liquid. Alternatively, as shown in Fig. 2C, washing with the second desalting wash liquid may be performed multiple times, and washing with the third desalting wash liquid may be performed multiple times. After any number of uses, the wastewater may be treated as wastewater, or may be reused for the chlorine-containing powder to be supplied to a subsequent stage.

[0047] FIG. 3 shows an embodiment of the desalting method for chlorine-containing powder according to the present invention, in which the desalting cake forming step, the first desalting cake washing step, and the second desalting cake washing step are performed using a single solid-liquid separation device. Specifically, the solid-liquid separation device may be, for example, a filter press or a belt filter. In the example shown in FIG. 3, the slurry that has undergone the chlorine leaching step is introduced into the solid-liquid separation device 1 and dehydrated according to the normal specifications of the device to obtain a first filtrate. The dehydrated cake retained in the device is washed according to the normal washing specifications of the device, and a second desalting wash liquid is introduced thereto to obtain a second filtrate. The cake that has been washed with the second desalting wash liquid retained in the device is washed according to the normal washing specifications of the device, and a third desalting wash liquid is introduced thereto to obtain a third filtrate. The second filtrate and the third filtrate are stored in storage tanks 2 and 3, respectively, and can be supplied at a desired timing as washing liquid for the chlorine-containing powder to be supplied to the subsequent stage.

[0048] In the example shown in Figure 3, the storage tank 2 and the storage tank 3 are equipped with measuring devices 4 and 5, respectively, to enable observation of the properties of the liquid in the tanks. The observations are not limited to, but may be, for example, the following (1) to (5): (1) Total time recycled using the second or third filtrate: Measure the operating time of the recycled pump using a timer meter; (2) Total amount of water recycled using the second or third filtrate: Measure the amount of water using a flow meter; (3) pH of the second or third filtrate: Measure the pH of the liquid in the tank using a pH meter; (4) Chloride ion concentration of the second or third filtrate: Measure the chloride ion concentration of the liquid in the tank using ion chromatography or potentiometric titration; (5) Electrical conductivity of the second or third filtrate: Measure the electrical conductivity of the liquid in the tank using an electrical conductivity meter.

[0049] As a guideline for the chloride ion concentration in the above (4), for example, it is preferable to keep it within the range of 0.5% by mass to 6% by mass in the case of the second filtrate, as in the case of the second desalting wash liquid and the third desalting wash liquid, and it is preferable to keep it within the range of 0% by mass to 2% by mass in the case of the third filtrate.

[0050] On the other hand, for example, as a guideline for the total time of (1) above, it is preferable to keep it within the range of 0 to 10 minutes in the case of the second filtrate, and it is preferable to keep it within the range of 0 to 20 minutes in the case of the third filtrate.

[0051] As a guideline for the total amount of water in (2) above, for example, the amount of water used is preferably limited to a range of 0 to 3.5 parts by mass for the second filtrate and 0 to 3.5 parts by mass for the third filtrate, per part by mass of the dry weight of the chlorine-containing powder to be desalted.

[0052] As a guideline for the pH of the above (3), for example, the second filtrate is preferably kept within the range of pH 7 to pH 13. For the third filtrate, the pH is preferably kept within the range of pH 7 to pH 12.5.

[0053] For example, the electric conductivity of the second filtrate in (5) above is preferably controlled to a range of 3 S / m to 30 S / m, and for the third filtrate, it is preferably controlled to a range of 0 S / m to 10 S / m.

[0054] FIG. 4 shows another example of the desalting method for chlorine-containing powder according to the present invention. That is, in the desalting method according to the present invention, for example, as illustrated in FIG. 3, the desalting cake forming step, the first desalting cake washing step, and the second desalting cake washing step may be performed in a single solid-liquid separator 1, and a solid-liquid separator using a filter cloth may be used in these steps. Specifically, the solid-liquid separator 1 may be, for example, a filter press or a belt filter. Typically, in solid-liquid separators using a filter cloth, constant cleaning is required throughout the operation period of the apparatus to prevent clogging of the filter cloth. This generates a large amount of filter cloth washing wastewater, which is stored in a storage tank 6 and can be supplied at a desired timing as a wash liquid for the chlorine-containing powder. In this case, the filter cloth washing wastewater contains insoluble matter washed off the used filter cloth. Therefore, the filter cloth washing wastewater may be treated in a solid-liquid separator 7, and the resulting liquid may be used as a wash liquid for the chlorine-containing powder. In particular, in the case of a filter press, using the solid-containing filter cloth washing wastewater directly as cake washing water (use as the wash liquid for the second and third desalting steps) may cause clogging of the filter cloth, so that after solid-liquid separation, the wastewater can be suitably used as the wash liquid for the second and third desalting steps or as the wash liquid for cleaning the filter cloth. The solid-liquid separation device 7 can be, for example, a filter press, a belt filter, a belt press, a vacuum drum filter, a settling tank, or the like.

[0055] In the method for desalting chlorine-containing powder according to the present invention, the amount of water used is, although not limited to, 1.5 to 4 parts by mass per part by mass of the dry weight of the chlorine-containing powder to be desalted. Here, a preferred range of the "amount of water used" can be calculated by dividing the amount of water newly supplied to the entire system by the dry weight of the chlorine-containing powder supplied to the system per hour. The breakdown of water used in each step, including recycled water, is approximately 1.5 to 7.0 parts by mass for the slurrying step, approximately 0.5 to 5.0 parts by mass for the first desalted cake washing step, and approximately 0.5 to 5.0 parts by mass for the second desalted cake washing step. Furthermore, if necessary, the amount of water used in the filter cloth washing step is approximately 0.1 to 2 parts by mass.

[0056] The present invention is not limited to the above-described embodiments, and various combinations and modifications within the scope of the disclosure in this specification are possible, and such embodiments are also included in the technical scope of the present invention.

[0057] The present invention will be explained in more detail below by way of test examples, although the scope of the present invention is not limited to these test examples.

[0058] Test Example 1: Chlorine bypass dust discharged from a cement factory (chlorine concentration: 20.94% as determined by the fundamental parameter method for X-ray fluorescence analysis) was subjected to the processes of slurrying, chlorine elution, desalting cake formation, and desalting cake washing using the predetermined amounts of water shown in Table 1. The effects of recycling the wastewater from the desalting cake washing process were investigated. A beaker, a propeller-type agitator, and a Buchner funnel were used for the test. Specifically, a predetermined amount of water and a predetermined amount of dust were mixed in a beaker to form a slurry. The slurry was passed through a Buchner funnel equipped with filter paper (quantitative filter paper No. 5c) and a filtrate receiving bottle. The pressure in the bottle was reduced using a vacuum pump to draw air, thereby dehydrating the slurry placed on the filter paper. The desalting cake was washed by spraying the wash liquid onto the desalted cake while it was still on the filter paper of the Buchner funnel. Thereafter, the desalted cake was separated from the filter paper to obtain a desalted cake. The filter paper was then attached to the Buchner funnel again, and while the pressure inside the bottle was reduced with a vacuum pump, the wash liquid was sprayed onto the filter paper to wash the filter paper and simultaneously perform solid-liquid separation.

[0059]

[0060] More specifically, as shown in FIG. 5 , in Comparative Examples 1 to 7, 1.5 to 5.0 parts by mass of fresh water was added per 1 part by mass of the dry weight of the chlorine bypass dust to be subjected to the first-stage treatment to form a slurry (hereinafter, this water ratio relative to the dry weight of the chlorine bypass dust will be abbreviated as "1.5 equivalents," etc.), and the desalted cake after dehydration was washed with 3.5 equivalents, 3 equivalents, 2.5 equivalents, 2 equivalents, 1.25 equivalents, or 1 equivalent of fresh water. Separately, 1.5 equivalents of fresh water was used to wash the filter paper, and 3.5 equivalents, 3 equivalents, 2 equivalents, 1.25 equivalents, or 1 equivalent of the second filtrate discharged from the first stage and 1.5 equivalents of the solid-free filter paper washing wastewater discharged from the first stage were used to form a slurry of the chlorine bypass dust to be subjected to the second-stage treatment. Note that in Comparative Example 7, the desalted cake was not washed.

[0061] 6, in Examples 1 to 5, 1.5 to 5.0 equivalents of fresh water were added to the chlorine bypass dust to be subjected to the first-stage treatment to form a slurry, and 3.5 equivalents, 2.5 equivalents, 1.5 equivalents, 1.25 equivalents, or 1 equivalent of fresh water was added to the desalted cake after dehydration to wash the desalted cake (first desalted cake washing), and the desalted cake was further washed repeatedly with the same equivalent of fresh water (second desalted cake washing). Similarly to Comparative Examples 1 to 7, 1.5 equivalents of fresh water was used to wash the filter paper, and 3.5 equivalents, 2.5 equivalents, 1.5 equivalents, 1.25 equivalents, or 1 equivalent of the second filtrate discharged from the first stage and 1.5 equivalents of the filter paper washing wastewater discharged from the first stage were used to form a slurry of the chlorine bypass dust to be subjected to the second-stage treatment. However, in Examples 1 to 5, the third filtrate discharged from washing the second desalting cake in the first stage was used in an amount of 3.5 equivalents, 2.5 equivalents, 1.5 equivalents, 1.25 equivalents, or 1 equivalent to wash the first desalting cake in the second stage desalting treatment.

[0062] On the other hand, as shown in FIG. 7 , in Example 6, slurrying, first desalted cake washing, second desalted cake washing, and filter paper washing were all carried out with 1.5 equivalents of water, except that the second filtrate discharged from the washing of the first desalted cake in the first stage was used for slurrying the chlorine bypass dust to be subjected to the second-stage treatment, the third filtrate discharged from the washing of the second desalted cake in the first stage was used for the first desalted cake washing, and the filter paper washing wastewater discharged from the first stage was used for the second desalted cake washing.

[0063] The chlorine concentration of the washed water after the treatment was measured by the fundamental parameter method using X-ray fluorescence analysis. In addition, the first filtrate discharged from the wastewater during the formation of the desalted cake was analyzed by ICP analysis (Pb, Zn) and ion chromatography (Cl).

[0064] Table 2 shows the total amount of fresh water used for treating chlorine bypass dust per stage, the chlorine concentration of the washed matter, and the results of component analysis of the wastewater.

[0065]

[0066] As a result, the following became clear:

[0067] As shown in Figure 8, the chlorine concentration of the dehydrated cake after washing increased as the fresh water ratio decreased in both the comparative example and the example. However, by recycling the wash water as in the example, it was possible to reduce the fresh water ratio (wastewater treatment volume) while maintaining the same chlorine concentration of the dehydrated cake as in the comparative example. For example, in comparative example 3, the total amount of fresh water used to treat the chlorine bypass dust per stage was 4 equivalents, and the chlorine concentration at this time was 0.59%-dry, whereas in example 1, a total amount of fresh water of 3 equivalents was sufficient to achieve a chlorine concentration of 0.57%-dry, the same as in comparative example 3.

[0068] On the other hand, the Pb and Zn components in the wastewater decreased in both the comparative example and the working example due to an increase in the Cl concentration in the wastewater caused by a decrease in the new water ratio (Figure 9). Furthermore, by recycling the wash water as in the working example, it is possible to lower the chlorine concentration in the dehydrated cake (while maintaining desalination performance) and reduce the Pb and Zn concentrations in the wastewater (Figure 10). This shows that it is possible to reduce the cost of wastewater treatment chemicals required for treating Pb and Zn.

[0069] FIG. 11 shows the relationship between the chlorine concentration of the dehydrated cake divided by the new water ratio, i.e., the residual chlorine concentration per unit amount of water, calculated by subtracting the value of the Example from the value of the Comparative Example at the same new water ratio, and the corresponding new water ratio.

[0070] As a result, as shown in FIG. 11, the effect of desalination treatment by circulating cleaning water in the Example was more pronounced when the new water ratio was smaller than in the Comparative Example when the new water ratio was the same.

[0071] From the above, it can be seen that by recycling the wash water, the amount of water used in the entire system required to achieve the purpose of desalination treatment can be reduced.

[0072] 1... solid-liquid separator (for dehydrating slurry or cake), 2, 3, 6... storage tank, 4, 5... measuring device, 7... solid-liquid separator (for removing cleaning residue from filter cloth)

Claims

DEPCT671. Treatment method for desalination of chlorinated powders consisting of: a turbidity suspension step for mixing chlorinated powders with a primary desalination liquid to obtain a turbidity suspension; a chlorination step for removing chlorine present in the liquid phase of the turbidity suspension; a desalination clumping step for removing chlorine from the turbidity suspension to obtain primary desalination clumps and primary filter liquid; a purification step for the primary desalination clumps to be purified with a second desalination liquid different from the primary desalination liquid to obtain second desalination clumps and secondary filter liquid.And the second desalination step for desalination of the second desalination block is performed with a third desalination liquid different from the first and second desalination liquids to obtain the third desalination block and the third filter liquid; here: the turbidity suspension step, the chlorine leaching step, the desalination block formation step, the first desalination block purification step, and the second desalination block purification step are repeated for each type of chlorinated powder to be delivered; and at least a portion of the third filter liquid obtained in the second desalination block purification step is collected and stored.It is reused for chlorinated powder to be delivered to the next step as one or both types of desalination fluids: the second desalination fluid for the first desalination block rinsing step and the third desalination fluid for the second desalination block rinsing step, and is reused as the first desalination fluid after one or more reuses; and the desalination block formation step, the first desalination block rinsing step, and the second desalination block rinsing step are performed using a solid-liquid separator that makes use of the filter cloth and at least the portion of the filter cloth rinsing wastewater obtained by filter cloth rinsing is reused as one or both types of desalination fluids: the second and third desalination fluids.

2. Treatment method for desalination of chlorinated powder according to claim 1,Here, the solid-liquid separator is a compressed air filter or a belt filter.

3. Treatment method for desalination of chlorinated powder according to claim 1, here, the solid-liquid separator is a compressed air filter and at least the portion of wastewater used to rinse the filter cloth is subjected to solid-liquid separation and the liquid portion obtained is reused to one or both types of desalination liquids and tertiary desalination liquids.

4. Treatment method for desalination of chlorinated powder consisting of: a turbidity suspension step for mixing the chlorinated powder with the first desalination liquid to obtain a turbidity suspension; a chlorination step for leaching chlorine present in the chlorinated powder in the liquid phase of the turbidity suspension; a desalination coagulation step for removing the turbidity suspension in which chlorine is leached to obtain the first type of desalination coagulation and the first type of filter liquid.The first purification step involves purifying the first type of degaling block using a second degaling liquid different from the first to obtain the second type of degaling block and the second type of filter liquid. The second purification step then involves purifying the second type of degaling block using a third degaling liquid different from the first and second to obtain the third type of degaling block and the third type of filter liquid. Here, the steps include: turbidity suspension step, chlorine leaching step, degaling block formation step, and first purification step.And the second desalination filtration step is repeated for each type of chlorinated powder to be delivered; and at least a portion of the third filtration liquid obtained in the second desalination filtration step is collected and stored, reused for the chlorinated powder to be delivered to the next step as one or both types of the second desalination filtration liquid for the first desalination filtration step and the third desalination filtration liquid for the second desalination filtration step, and reused as the first desalination filtration liquid after one or more reuse; and the desalination block formation step, the first desalination block filtration step,And the second desalination step of the desalination block is carried out using a solid-liquid separator that utilizes filter cloth and at least a portion of the filter cloth rinsing wastewater obtained by filter cloth rinsing is reused as a desalination liquid for the first desalination.

5. Treatment method for desalination of chlorinated powders according to claim 3, where at least a portion of the filter cloth rinsing wastewater obtained by filter cloth rinsing is reused as one or both types of desalination liquid for the second desalination and desalination liquid for the third desalination.

6. Treatment method for desalination of chlorinated powders according to claim 3 or 4, where the solid-liquid separator is a compressed air filter or a belt filter.

7. Treatment method for desalination of chlorinated powders according to claim 3 or 4,Here, the solid-liquid separator is a sludge filter press, and at least a fraction of the wastewater used to rinse the filter cloth is introduced into the solid-liquid separator, and the liquid fraction obtained from this is reused as one or both of the secondary desalination liquids and tertiary desalination liquids.

8. The desalination treatment method for chlorinated powders under any of claims 1 to 6, here, when the reuse time of the tertiary filter liquid obtained in the secondary desalination step, whether or not the tertiary filter liquid is used, is analyzed by observing at least one of the following (1) to (5) in the holding tank in which at least a fraction of the tertiary filter liquid is collected and retained: (1) the total time for treatment for reuse with the tertiary filter liquid, (2) the total volume of water for treatment for reuse with the tertiary filter liquid, (3) the pH of the tertiary filter liquid, (4) the chlorine ion concentration of the tertiary filter liquid,and (5) the electrical conductivity of the third filter liquid.

9. Any of the treatments for desalination of chlorinated powders under claims 1 through 7, herein at least a portion of the second filter liquid obtained in the first desalination step is collected and retained, reused for chlorinated powders to be delivered to the next step as the second desalination liquid for the first desalination step, and reused as the first desalination liquid after one or more reuses.

10. Any of the treatments for desalination of chlorinated powders under claim 8, herein at the time of reuse of the second filter liquid obtained in the first desalination step,Whether or not a second-stage filtration fluid is used, analysis is performed by making at least one of the following observations in (1) to (5) in the storage tank in which at least a portion of the second-stage filtration fluid is collected and retained: (1) total time for reuse treatment with the second-stage filtration fluid, (2) total volume of water for reuse treatment with the second-stage filtration fluid, (3) pH of the second-stage filtration fluid, (4) chlorine ion concentration of the second-stage filtration fluid, and (5) electrical conductivity of the second-stage filtration fluid.

11. Any of the desalination treatment methods under claims 1 to 9 herein: the purification of the first-stage desalinated block with the second-stage desalination fluid in the purification step of the first-stage desalinated block is performed multiple times with the second-stage desalination fluid,and / or the purification of the second desalinated solid with the third desalination liquid in the second desalination solid purification step is performed multiple times with the third desalination liquid.

12. Any of the desalination treatment methods for chlorinated powders under claims 1 to 10, herein: the amount of water used is 1.5 parts by mass to 4 parts by mass based on 1 part by mass of the dry weight of the chlorinated powder to be brought to desalination treatment.

13. Any of the desalination treatment methods for chlorinated powders under claims 1 to 11, herein: the desalination solid formation step, the first desalination solid purification step, and the second desalination solid purification step are performed in a single solid-liquid separator;

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