JP2008237948A - Stabilization treatment method and device for waste - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stabilization treatment method and device for waste, wherein fluorine and phosphoric acid in a filtrate of waste are reduced without requiring a large quantity of phosphoric acids and deteriorating filtering properties for the waste, the elution of fluorine from the waste can be securely reduced to a fixed standard value or below, and resource saving can be attained. <P>SOLUTION: To the slurry of waste stored in a slurry stirring tank 2, an alkali substance or an acid substance is added and stirred so that the hydrogen ion concentration index of the slurry reaches 7.0 to <8.6. The slurry to which the alkali substance or acid substance is added and stirred is dehydrated by a dehydrator 4, so as to form a dehydrated cake. A solution of phosphoric acids comprising phosphoric acids of 2 to 15 pts.wt. based on the weight equivalent to the weight of phosphoric acid adjusted in such a manner that the content of phosphorous is made the same to 1 pts.wt. of fluorine contained in the dehydrated cake and also prepared by 5 to <10 pts.wt. based on 10 pts.wt. of the dehydrated cake is fed to the formed dehydrated cake by a treatment liquid feed pump 21 from a treatment liquid storage tank 5, so as to be brought into contact with the dehydrated cake. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention is a method for stabilizing and stabilizing waste such as by-product gypsum, waste gypsum board (recycled gypsum), dewatered sludge, water sludge, sewage sludge, crushed stone / coagulated sand sludge, contaminated soil and dust collection dust. More specifically, the present invention relates to a waste stabilization treatment method and a stabilization treatment device that hardly dissolve fluorine, which is a trace amount of harmful substances contained in these wastes, and suppress elution into the environment. Is.

  Wastes often contain trace amounts of environmentally hazardous elements that are designated as environmentally regulated substances, which is problematic during effective use or landfill disposal. In particular, there is a problem when the amount of elution of fluorine or the like added to the soil environment standard in 2001 exceeds the regulation value. Wastes containing fluorine include byproduct gypsum, waste gypsum board and dewatered sludge.

  In general, gypsum is used in large quantities as a raw material for gypsum board and cement as a building material. In particular, gypsum board is inexpensive and excellent in fire resistance, so about 4.7 million tons (2003) is used as an interior material for buildings annually, and waste gypsum board at the time of building dismantling is 860,000 tons (2004) Most of them are landfilled along with other industrial waste. In particular, since most of the byproduct gypsum occupying about 40 to 50% of the raw material of gypsum board contains fluorine, development of a technique for making fluorine hardly soluble and stabilizing is desired.

  There is a technique in which a calcium compound such as slaked lime is added to a gypsum slurry to fix fluorine as calcium fluoride. However, the solubility of calcium fluoride as fluorine is about 8 ppm. In the case of fluorine, the amount of elution of fluorine from gypsum is reduced because the elution amount is set to 0.8 mg / L or less as the soil environment standard. This is not a sufficiently effective technology to do this.

  In view of such problems, there are conventional techniques such as the following (1) to (3) as a method for reducing the elution amount of fluorine with respect to gypsum as waste to 0.8 mg / L or less.

  (1) An alkali is added to a slurry of dihydrate gypsum or a slurry of hemihydrate gypsum to raise the pH to 9 or higher, and then a phosphoric acid and / or an acid is added to reduce the pH to 1 As described above, a technique of obtaining gypsum by filtering after reducing the eluted fluorine by adjusting the lowered pH to 6 or more (see, for example, Patent Document 1).

  (2) A technique in which filtered dihydrate gypsum is washed with weakly acidic wash water containing a sulfuric acid band, and fluorine is eluted and removed in the wash solution (see, for example, Patent Document 2).

  (3) Technology for reducing the fluorine elution amount of dihydrate gypsum by adding phosphoric acid and an alkaline agent to the filtered dihydrate gypsum and mechanically kneading and curing using a kneader (for example, Patent Document 3) reference).

JP 2003-206133 A Japanese Patent Application Laid-Open No. 2004-299962 Japanese Patent Application No. 2003-305833

In the above-described conventional technology, the following problems remain.
In the technique of Patent Document 1, since the pH of the gypsum slurry is increased to 9 by adding an alkali, a large amount of alkali is necessary, and then the pH is lowered to around 6 by adding phosphoric acids and / or acids. Therefore, in order to neutralize the alkali remaining in the gypsum slurry, a larger amount of phosphoric acid and / or acid is required, and the purity of the gypsum is lowered and the purity of the gypsum hardened body is also lowered. This is because when phosphoric acids and / or acids are added to the gypsum slurry, it reacts with calcium ions, magnesium ions and other cations dissolved in the gypsum slurry, requiring a lot of phosphoric acid and / or acid. This is because.

  In addition, in the gypsum slurry prepared by the method disclosed in Patent Document 1, fine particles such as calcium phosphate produced mainly by the added phosphoric acid and the alkaline substance are present, so when the gypsum slurry is filtered. In addition, moisture tends to stay in the gypsum, resulting in poor filtration characteristics.

  Furthermore, since a large amount of unreacted phosphoric acid remains in the filtrate produced by the method disclosed in Patent Document 1, the treatment becomes a problem.

  In the method disclosed in Patent Document 2, since fluorine is eluted and removed in the cleaning liquid, a large amount of fluorine remains in the cleaning liquid, and removal of fluorine from the cleaning liquid becomes a problem. Moreover, the aluminum fluoride produced | generated by reaction with a washing | cleaning liquid becomes high solubility in pH = 7-8.6, and cannot satisfy the elution amount reference value (0.8 mg / L).

  In the method disclosed in Patent Document 3, a large amount of power is required for mechanical stirring for dispersing phosphoric acid, an alkaline substance, and gypsum particles.

  The object of the present invention is to eliminate the need for large amounts of phosphoric acid, to reduce the fluorine and phosphoric acid in the waste filtrate without deteriorating the filtration characteristics of the waste, and to keep the elution of fluorine from the waste constant. It is an object of the present invention to provide a waste stabilization processing method and a stabilization processing apparatus that can be surely reduced below a reference value and can save resources.

The present invention stirs an alkaline substance or an acid substance into a slurry of waste so that the hydrogen ion concentration index of the slurry is 7.0 or more and less than 8.6,
The slurry in which the alkaline substance or acid substance is stirred is dehydrated to form a dehydrated cake,
2 parts by weight or more and less than 15 parts by weight of phosphoric acid equivalent in terms of phosphoric acid equivalent weight so that the phosphorus content is the same with respect to 1 part by weight of fluorine contained in the dehydrated cake, and the dehydrated cake 10 It is a waste stabilization method characterized in that a phosphoric acid solution of 5 parts by weight or more and less than 10 parts by weight is permeated through the produced dehydrated cake with respect to parts by weight.

  According to the present invention, first, the hydrogen ion concentration index of the slurry of waste is set to 7.0 or more and less than 8.6 with an alkali substance or an acid substance. The waste slurry may have any concentration as long as the hydrogen ion concentration index of the waste slurry can be adjusted, and the concentration of solid matter contained in the waste slurry is several tens of thousands. % Or several% or less. Further, as the dispersion medium for the waste slurry, for example, water is used, but a solvent such as an organic substance may be contained. If the hydrogen ion concentration index of the waste slurry is less than 7.0, the reaction between the substances contained in the waste slurry and the phosphoric acids contained in the phosphoric acid aqueous solution permeated through the dewatered cake becomes insufficient. When the hydrogen ion concentration index of the slurry is set to 8.6 or more, it is necessary to add an excessive alkaline substance. By setting the hydrogen ion concentration index of the slurry to 7.0 or more and less than 8.6, it is possible to minimize the amount of phosphoric acid and alkaline substance used for the stabilization treatment.

  The phosphoric acid may be an acidic phosphate produced by a reaction between phosphoric acid and a cation, or phosphoric acid itself. Phosphoric acids may be acid substances such as hypophosphorous acid, phosphorous acid, phosphoric acid, pyrophosphoric acid, polyphosphoric acid and metaphosphoric acid, and may be calcium hydrogen phosphate and aluminum hydrogen phosphate. Also good. As the phosphoric acid, an acid that dissolves in water as phosphating water is desirable. Particularly effective is phosphoric acid.

  As the alkaline substance, any alkali calcium compound may be used. For example, slaked lime (calcium hydroxide), calcium carbonate, dolomite, cement, and steel blast furnace slag powder can be applied.

  The acid substance may be the aforementioned inorganic acids such as phosphoric acids, sulfuric acid and nitric acid, or may be an organic acid such as acetic acid.

  After dewatering the slurry of waste whose hydrogen ion concentration index is adjusted to 7.0 or more and less than 8.6, the phosphoric acid solution is permeated through the dehydrated cake generated by dehydration, and the phosphoric acid solution is added to the dehydrated cake. Since it is contacted, the waste slurry is dehydrated before the product produced by the reaction of phosphoric acids is generated. Can be obtained.

  In a slurry of waste containing fluorine, the alkaline substance is agitated so that the hydrogen ion concentration index is 7.0 or more and less than 8.6, and then the dehydrated cake produced by dehydration has a solid content of waste. When the phosphoric acid solution is permeated through the dehydrated cake, the phosphoric acid solution comes into contact with the dehydrated cake, so that the phosphoric acid contained in the phosphoric acid solution reacts with the alkaline material, thereby Calcium hydrogen hydrogen dihydrate (dibasic calcium phosphate) is synthesized, and fluorine and calcium hydrogen phosphate dihydrate react to produce calcium fluorophosphate, thereby fixing fluorine to the waste. It is possible to reduce the amount of fluorine contained in the waste that elutes from the waste particles to the outside.

  2 parts by weight or more and less than 15 parts by weight of phosphoric acid equivalent in terms of phosphoric acid equivalent weight so that the phosphorus content is the same with respect to 1 part by weight of fluorine contained in the dehydrated cake, and the dehydrated cake 10 By allowing a phosphoric acid solution of 5 parts by weight or more and less than 10 parts by weight to permeate the dehydrated cake, the phosphoric acid solution reduces the phosphoric acid contained in the filtrate obtained by permeating the dehydrated cake. be able to. Moreover, compared with the method disclosed in Patent Document 2, the amount of fluorine eluted into the filtrate can be reduced, so that the filtrate can be easily treated. When phosphoric acids contain less than 2 parts by weight of phosphoric acid equivalent weight in terms of phosphoric acid equivalent weight with respect to 1 part by weight of fluorine contained in the dehydrated cake, fluorine Reduction of the amount of elution is not sufficient. In addition, when 1 part by weight of fluorine contained in the dehydrated cake contains 15 parts by weight or more of phosphoric acid in an equivalent weight of phosphoric acid converted so that the phosphorus content is the same, it was generated after the treatment. The hydrogen ion concentration index of the dehydrated cake will be 6.5 or less. Therefore, the amount of phosphoric acid contained in the phosphoric acid solution is determined by the fluorine content and the hydrogen ion concentration index of the product produced by the stabilization treatment, and the stabilization treatment according to the fluorine content in the waste slurry. In the case of treating waste having a low hydrogen ion concentration index of the product generated by performing the above, the amount of phosphoric acid contained in the phosphoric acid solution is reduced.

  A phosphoric acid solution containing 2 parts by weight or more and less than 15 parts by weight of phosphoric acid in terms of equivalent weight of phosphoric acid so that the phosphorus content is the same with respect to 1 part by weight of fluorine contained in the dehydrated cake, By setting the amount to 5 parts by weight or more and less than 10 parts by weight with respect to 10 parts by weight of the dehydrated cake, the hydrogen ion concentration index of the product formed by the stabilization treatment becomes 6.5 to 8.5. Fluorine can be stabilized without shortage.

  Further, the present invention is characterized in that the filtrate obtained by allowing the phosphoric acid solution to permeate the dehydrated cake permeates the dehydrated cake.

  According to the present invention, the filtrate containing phosphoric acid obtained by allowing the phosphoric acid solution to permeate the dehydrated cake is stored, and before the phosphoric acid solution permeates the dehydrated cake or after the phosphoric acid solution permeates the dehydrated cake. Since the filtrate is permeated through the dehydrated cake, the phosphorus component remaining in the filtrate can be brought into contact with the dehydrated cake again, and the opportunities for the phosphoric acids to contact the dehydrated cake can be increased. The concentration of phosphoric acid contained in can be reduced to further save resources.

The present invention also includes a stirring tank,
First supply means for supplying an alkaline substance or an acid substance to the stirring tank so that the hydrogen ion concentration index of the slurry of the waste put in the stirring tank is 7.0 or more and less than 8.6;
Dehydrating means for dewatering the slurry of the waste material stirred by the alkaline substance or acid substance supplied by the first supplying means to produce a dehydrated cake;
2 parts by weight or more and less than 15 parts by weight of phosphoric acid equivalent in terms of phosphoric acid equivalent weight so that the phosphorus content is the same with respect to 1 part by weight of fluorine contained in the dehydrated cake, and the dehydrated cake 10 A waste stabilization treatment apparatus comprising: a second supply unit that supplies a phosphoric acid solution of 5 parts by weight or more and less than 10 parts by weight to the dehydrated cake with respect to parts by weight.

  According to the present invention, the above-described waste stabilization method can be realized by the stirring layer, the first supply unit, the dehydration unit, and the second supply unit. In these apparatuses, in order to realize the stabilization method described above, no special equipment is required, and the apparatus can be manufactured using existing equipment for washing and dewatering waste. The dehydrating means may be realized by, for example, a vacuum belt filter type dehydrator.

The present invention also includes a filtrate storage tank for storing a filtrate obtained by allowing the phosphoric acid solution to permeate the dehydrated cake,
The dehydrating cake includes third supply means for supplying the filtrate stored in the filtrate storage tank.

  According to the present invention, the filtrate obtained by permeating the dehydrated cake is stored in the filtrate storage tank, and the stored filtrate is supplied again to the dehydrated cake by the third supply means, and the phosphate solution supply means is used. Before or after allowing the phosphate solution to permeate the dehydrated cake, the filtrate can permeate the dehydrated cake, and the phosphoric acid remaining in the filtrate permeated through the dehydrated cake is brought into contact with the dehydrated cake again. In addition, since it is possible to increase the chances that phosphoric acids come into contact with the dehydrated cake, the concentration of phosphoric acids contained in the phosphoric acid solution can be reduced to further save resources.

  According to the present invention, an alkali substance or an acid substance is added to a slurry of waste and stirred, so that the hydrogen ion concentration index of the slurry is 7.0 or more and less than 8.6, the slurry is dehydrated, A dehydrated cake is produced, and 2 parts by weight or more and less than 15 parts by weight in terms of phosphoric acid equivalent weight so that the phosphorus content is the same with respect to 1 part by weight of fluorine contained in the dehydrated cake. The amount of phosphoric acid to be used is minimized by contacting the phosphoric acid solution containing 5 parts by weight or more and less than 10 parts by weight with 10 parts by weight of the dehydrated cake. The waste that is a dehydrated cake in which the amount of fluorine elution is reduced can be efficiently generated by reducing the phosphoric acids contained in the filtrate produced in the course of treatment without deteriorating the properties.

  In addition, the present invention does not require a large amount of chemicals to stabilize fluorine, minimizes additional equipment and obtains waste with reduced fluorine elution, and is economical and environmentally friendly. Can be reduced.

  The present invention can be applied to a wide variety of wastes, because the amount of phosphoric acid and an agent that is an alkali substance or acid substance is adjusted according to the fluorine content and the hydrogen ion concentration index in the waste.

  BEST MODE FOR CARRYING OUT THE INVENTION The best mode for carrying out the present invention will be described below, but the present invention is not limited to the following embodiment, and can be implemented with appropriate modifications.

  FIG. 1 is a diagram schematically showing a stabilization processing apparatus 1 according to a first embodiment of the present invention. In the following, a description will be given by taking, as an example, gypsum that collectively refers to byproduct gypsum and waste gypsum board. The stabilization processing apparatus 1 is adapted to a vacuum belt filter type dehydrator.

  In this embodiment, the waste slurry is a gypsum slurry, and the gypsum contained in this gypsum slurry may be either natural or artificially synthesized. There are various types of synthetic gypsum, such as phosphate gypsum produced as a by-product during phosphoric acid production, flue gas desulfurization gypsum derived from flue gas desulfurization from power plants, etc., and titanium gypsum produced as a by-product during titanium production. Waste gypsum (recycled gypsum) separated from paper from gypsum board for the purpose of recycling such as building waste. The present invention can be applied to byproduct gypsum containing fluorine, and natural gypsum can be similarly applied as long as it contains fluorine. The gypsum includes dihydrate gypsum, hemihydrate gypsum and anhydrous gypsum depending on the crystal form, but the present invention can be applied to any gypsum containing fluorine.

The slurry of the gypsum before treatment may be any concentration as long as the hydrogen ion concentration index (pH) of the gypsum can be adjusted. It may be a dispersed state of several wt% or less. As the dispersion medium, water (H ₂ O) is usually used, but it may contain by-products and contaminants generated in the gypsum production process, and may contain a solvent such as an organic substance. In this embodiment, industrial water is used as a dispersion medium for the gypsum slurry.

  The stabilization processing apparatus 1 includes a slurry stirring tank 2, a first supply machine 3, a dehydrator 4, a treatment liquid storage tank 5, a second supply machine 6, and a third supply machine 7.

  The slurry agitation tank 2 contains gypsum slurry. The slurry agitation tank 2 is provided with an agitation device for agitating the gypsum slurry, and the stored gypsum slurry is agitated, so that sedimentation of solids in the slurry agitation tank 2 is prevented. In this Embodiment, the density | concentration of the slurry of the gypsum supplied to the slurry stirring tank 2 is about 20 to 30 weight percent (wt%). The hydrogen ion concentration index (pH) of the gypsum slurry supplied to the slurry agitation tank 2 is about 5.5 to 7.0.

  The first supply machine 3 supplies an alkaline substance or an acid substance to the slurry agitation tank 2 via the first supply pipe 11. In this embodiment, since the hydrogen ion concentration index (pH) of the gypsum slurry is about 5.5 to 7.0, the first supply unit 3 supplies the alkaline substance to the slurry agitation tank 2. The alkaline substance from the first supply machine 3 is supplied to the slurry agitation tank 2 through a pipe line formed by the first supply pipe 11. The alkaline substance supplied to the slurry agitation tank 2 is agitated by the gypsum slurry accommodated in the slurry agitation tank 2 to mix the gypsum slurry and the alkaline substance. The slurry agitation tank 2 is provided with a pH measuring device for measuring the pH of the gypsum slurry accommodated in the slurry agitation tank 2. Based on the measurement result of the pH measuring device, the first supply device 3 supplies the alkaline substance so that the pH of the gypsum slurry stored in the slurry agitation tank 2 is 7.0 or more and less than 8.6. Supply gypsum slurry.

  When raising the pH of the gypsum slurry, that is, when increasing the pH value of the gypsum slurry, the alkaline substance may be added to the gypsum slurry as it is, or diluted with water and added to the gypsum slurry. May be. It is necessary to sufficiently stir after adding the alkaline substance. The supply amount of the alkaline substance from the first feeder 3 is basically controlled by the pH value of the gypsum slurry in the slurry agitation tank 2, but the properties of the gypsum slurry and the supplied alkaline substance are stable. In this case, it may be a fixed ratio with respect to the gypsum slurry.

  In the slurry agitation tank 2, when the alkali substance is supplied from the first supply unit 3, the slurry of the gypsum to which the alkali substance has been added is agitated for a predetermined time so that the concentration of the gypsum slurry becomes uniform. The predetermined time is selected to be about 30 minutes, for example. In the gypsum slurry stored in the slurry agitation tank 2, the amount of fluorine eluted in the gypsum slurry liquid is very small.

  As the alkaline substance, any alkali calcium compound may be used. For example, slaked lime (calcium hydroxide), calcium carbonate, dolomite, cement, and steel blast furnace slag powder can be applied.

  The gypsum slurry whose pH is adjusted so that the pH is 7.0 or more and less than 8.6 is supplied to the dehydrator 4 via the slurry supply pipe 13 by the slurry supply pump 12. The gypsum slurry is supplied to the dehydrator 4 from a slurry supply nozzle 30 provided in the dehydrator 4 through a pipe line formed by the slurry supply pipe 13. If the hydrogen ion concentration index of the gypsum slurry is less than 7.0, the reaction between the substance contained in the gypsum slurry and the phosphoric acid contained in the phosphoric acid aqueous solution permeated through the dehydrated cake becomes insufficient. When the hydrogen ion concentration index is set to 8.6 or more, it is necessary to add an excessive alkaline substance. By setting the hydrogen ion concentration index of the gypsum slurry to 7.0 or more and less than 8.6, it is possible to minimize the amount of phosphoric acid and alkaline substance used for the stabilization treatment.

  The dehydrator 4 dehydrates the gypsum slurry supplied from the slurry agitation tank 2 with the alkaline substance stirred and separates it into a dehydrated cake layer 14 and a filtrate 15. In the present embodiment, the dehydrator 4 includes a vacuum pump 16, a transport unit 31 that loads and transports a gypsum slurry, and a filtrate tank 61, and a gypsum slurry by a vacuum belt filter system. Dehydrate.

  FIG. 2 is a plan view schematically illustrating the transport unit 31 of the dehydrator 4 in the stabilization processing apparatus 1, and FIG. 3 is a cross-sectional view schematically illustrating the transport unit 31 of the dehydrator 4 in the stabilization processing apparatus 1. It is. The transport unit 31 includes a housing 32, a roller 33, a belt 34, and a drive unit 45. A plurality of rollers 33 are provided in the casing 32 with a predetermined interval in a state where the rotation axes thereof are parallel to each other. The plurality of rollers 33 are held by the housing 32 so as to be rotatable around its rotation axis. A belt 34 is stretched around the plurality of rollers 33. The belt 34 is formed with fine holes. The belt 34 is realized by a filter cloth. The coarseness of the filter cloth is selected so that the gypsum contained in the gypsum slurry mounted on the belt 34 does not permeate. The belt 34 is circulated and rotated by rotationally driving the roller by the driving unit 45. The drive unit 45 includes an air cylinder 47 that is a drive source capable of pushing the roller 46 at the end portion on the downstream side in the transport direction out of the plurality of rollers 33 from the reference position toward the downstream side in the transport direction. Consists of. The belt 36 is provided with a displacement allowing portion 48 that allows the belt 34 to be displaced when the air cylinder 47 pushes out the roller 46. The displacement allowance portion 48 is provided in the vicinity of the air cylinder 47 at the end on the downstream side in the transport direction. The displacement allowance portion 48 includes a pair of support rollers 49 that support the lower stretch portion 36 from below, and a weight roller that presses the lower stretch portion 36 downward between the pair of support rollers 49 in the transport direction. 71. The rotation axes of the support roller 49 and the weight roller 71 extend parallel to the rotation axis of the roller 33. The support roller 49 is rotatably held on the rotation axis of the casing 32, and the weight roller 71 is displaceable in the vertical direction, that is, the direction in which gravity acts, and is rotatable on the casing 32 around the rotation axis. Provided. Of the support rollers 49, the support roller 49 on the downstream side in the conveying direction, that is, the support roller 49 on the right side in FIG. 2 can rotate only in one direction, thereby moving the belt 34 only in one direction of rotation. It is possible to prevent 34 from rotating in the reverse direction. When the roller 46 is pushed toward the downstream side in the transport direction by the air cylinder 47, the belt 34 is pushed out to the downstream side in the transport direction as indicated by the phantom line in FIG. 3, and the belt is supported by the support roller 49 that can rotate only in one direction. Since the reverse rotation of the belt 34 is prevented, the overhanging portion 35 of the belt 34 moves downstream in the conveying direction, and the weight roller 71 moves upward accordingly. When the air cylinder 47 returns the roller 46 to the reference position, the weight roller 71 moves downward and the belt 34 is stretched. In the conveyance unit 31, the belt 34 can be rotationally driven by repeating the operation in which the air cylinder 47 pushes out the roller 46 and returns it.

  The upper suspension portion 35 of the belt 34 extends horizontally. A slurry supply nozzle portion 30 is provided in the housing 32 so as to supply a gypsum slurry to the end of the upper stretch portion 35 on the upstream side in the conveying direction. The nozzle portion 30 discharges gypsum slurry between both widthwise end portions of the belt 34, and the gypsum slurry is placed on the overhanging portion 35 across both widthwise end portions of the belt 34. Inclined members 72 that incline upward as they move away from the upper stretch portion 35 are provided on both sides of the upper stretch portion 35 of the belt 34 in the direction perpendicular to the conveying direction and the thickness direction of the belt 34. The inclined member 72 is fixed to the vacuum tray portion 37. The inclined member 72 extends from the upstream side in the transport direction with respect to the slurry supply nozzle portion 30 to the downstream end portion in the transport direction of the upper stretch portion 35 of the belt 34. The inclined member 72 prevents the gypsum slurry and the dehydrated cake layer 14 mounted on the belt 34 from dropping from the transport unit 31 during transport.

  Further, the end portion on the upstream side in the transport direction of the upper stretch portion 35 is inclined upward as it goes toward the upstream side in the transport direction. This prevents the gypsum slurry supplied from the slurry supply nozzle portion 30 from falling from the upstream end of the upper stretch portion 35 in the transport direction. In addition, the end portion on the downstream side in the transport direction of the upper stretch portion is inclined downward as it goes toward the downstream side in the transport direction. As a result, the dehydrated cake layer 14 on the belt 34 can be easily carried out of the transport unit 31.

  The transport unit 31 is provided with a cleaning unit 73 for cleaning the belt 34. The cleaning unit 73 is provided on the downstream side of the belt 34 in the transport direction, and cleans the lower stretcher 36 with water.

  A vacuum tray portion 37 for receiving the filtrate separated from the gypsum slurry is provided between the upper stretch portion 35 and the lower stretch portion 36 of the belt 34. The vacuum tray unit 37 is provided in contact with the overhanging unit 35. The vacuum tray portion 37 is provided between both end portions in the width direction of the belt 34 and extends from the upstream side in the transport direction with respect to the slurry supply nozzle portion 30 in the transport direction to the downstream side in the transport direction with respect to the processing liquid supply nozzle portion 41. The suction force is guided to the vacuum tray portion 37 via the filtrate suction pipe 17 that guides the suction force from the vacuum pump 16. As a result, the gypsum slurry mounted on the overhanging portion 35 is subjected to suction filtration to be separated into a dehydrated cake layer 14 and a filtrate 15. The filtrate 15 sucked by the vacuum pump 16 is stored in the filtrate tank 61 via the filtrate suction pipe 17. The filtrate tank 61 is provided to separate the filtrate 15 sucked by the vacuum pump 16 from the air. The filtrate 15 from the filtrate suction pipe 17 is stored in the filtrate tank 61, and a vacuum pump suction pipe 62 is connected to guide the suction force from the vacuum pump 16. The vacuum pump 16 sucks the air inside the filtrate tank 61 through the vacuum pump suction pipe 62. The vacuum pump suction pipe 62 and the filtrate suction pipe 17 are provided above the liquid level of the filtrate 15 stored in the filtrate tank 61, and the vacuum pump suction pipe 62 is more filtered than the filtrate suction pipe 17. The liquid tank 61 is provided above. As a result, the vacuum pump 16 can suck only the air in the filtrate tank 61. By sucking the air in the filtrate tank 61, a suction force can be guided to the filtrate suction pipe 17.

  A filtrate discharge pipe 63 is connected to the lower part of the filtrate tank 61, and the filtrate discharge pipe 63 is connected to the filtrate storage tank 18. The filtrate 15 in the filtrate tank 61 is transferred to the filtrate storage tank 18 via the filtrate discharge pipe 63, and the filtrate 15 is stored in the filtrate storage tank 18. A lower tray 38 for receiving the liquid remaining on and attached to the lower stretch portion 36 is provided below the lower stretch portion 36.

  A processing liquid supply nozzle portion 41 is provided facing the upper stretch portion 35 at an intermediate portion of the upper stretch portion 35 in the transport direction, in this embodiment, at a central portion in the transport direction. The processing liquid supply nozzle unit 41 is provided apart from the placement surface of the belt 34 by a predetermined distance T1. The predetermined distance T1 is selected so as to be larger than the thickness of the dehydrated cake layer 14 on the placement surface of the overhanging portion 35. The thickness of the dehydrated cake layer 14 is selected from 20 to 30 mm. This thickness is determined by the amount of gypsum slurry discharged from the slurry supply nozzle unit per unit time and the moving speed of the belt 34.

  A processing liquid is supplied to the processing liquid supply nozzle section 41 via a processing liquid supply pipe 22 described later, and the processing liquid supply nozzle section 41 discharges the supplied processing liquid vertically downward. The processing liquid supply nozzle unit 41 discharges the supplied processing liquid across both end portions in the width direction of the belt 34. As a result, the treatment liquid can be transmitted through the dehydrated cake layer 14 over the entire region in the width direction of the dehydrated cake layer 14 mounted on the belt 34.

  The processing liquid supply nozzle portion 41 and the slurry supply nozzle portion 30 are provided at a predetermined distance T2 in the transport direction. The predetermined distance T2 is selected so that the moisture content of the dehydrated cake layer 14 at the position where the processing liquid is supplied from the processing liquid supply nozzle 41 is about 20%. The gypsum slurry supplied from the slurry supply nozzle part 30 is conveyed while being dehydrated, and the processing liquid is supplied from the processing liquid supply nozzle part 41 to a position where the water content becomes about 20%. As described above, in the present apparatus, the dehydration process and the process of supplying the treatment liquid to the dehydrated cake can be performed continuously. In the dehydrated cake layer 14, the moisture content of the portion on the downstream side in the transport direction from the position where the treatment liquid is supplied is about 10%. On the downstream side in the transport direction, the dehydrated cake layer 14 is unloaded from the end of the belt 34 on the downstream side in the transport direction, so that the processed dehydrated cake is obtained.

  Referring to FIG. 1 again, the second supply machine 6 supplies industrial water, which is water, to the treatment liquid storage tank 5. The third supply machine 7 supplies phosphoric acids to the processing liquid storage tank 5. The treatment liquid storage tank 5 is provided with a stirring device, and contains water supplied from the second supply device 6 and phosphoric acids supplied from the third supply device 7, and these are stirred and mixed. The phosphoric acids diluted and mixed with water are supplied to the processing liquid supply nozzle 41 by the processing liquid supply pump 21 via the processing liquid supply pipe 22.

  The phosphoric acid may be an acidic phosphate produced by a reaction between phosphoric acid and a cation, or phosphoric acid itself. Phosphoric acids may be acid substances such as hypophosphorous acid, phosphorous acid, phosphoric acid, pyrophosphoric acid, polyphosphoric acid and metaphosphoric acid, and may be calcium hydrogen phosphate and aluminum hydrogen phosphate. Also good. As the phosphoric acid, an acid that dissolves in water as phosphating water is desirable. Particularly effective is phosphoric acid.

When the treatment liquid is supplied to the dehydrated cake layer 14, the treatment liquid contacts the dehydrated cake layer 14 while passing through the dehydrated cake layer 14. Inside the dehydrated cake layer 14, the alkaline substance contained in the dehydrated cake layer 14 reacts with phosphoric acids contained in the treatment liquid to generate calcium hydrogen phosphate dihydrate (CaHPO ₄ .2H ₂ O). The This calcium hydrogen phosphate dihydrate reacts with fluorine contained in gypsum to produce calcium fluorophosphate (Ca ₁₀ F ₂ (PO ₄ ) ₆ ), so that fluorine is fixed to gypsum and stabilizes fluorine. That is, the amount of fluorine eluted is reduced. The filtrate that has passed through the dehydrated cake layer 14 out of the treatment liquid is sucked by the vacuum pump 16 and stored in the filtrate storage tank 18.

  The amount of phosphoric acid supplied to the treatment liquid storage tank 5 by the third supply machine 7 is necessary depending on the fluorine content contained in the dehydrated cake layer 14 supplying this phosphoric acid and the pH of the treated gypsum. Supply in proportions. The concentration of the treatment liquid containing phosphoric acids is determined according to the treatment performance with respect to the weight of the gypsum contained in the dehydrated cake layer 14 when the properties and flow rate of the gypsum slurry are both stable. When either the quality or flow rate of the gypsum slurry fluctuates, the concentration of the treatment liquid containing phosphoric acids is adjusted according to the weight of gypsum contained in the dehydrated cake layer 14, the pH of the filtrate, and the like.

  Phosphoric acids are supplied to the processing liquid storage tank 5 by the third supply unit 7. About the method of supplying phosphoric acids to the processing liquid storage tank 5, desirably, the pH of the processing liquid in the processing liquid storage tank 5 is detected, and the phosphoric acids are set so that the pH value falls within a predetermined value range. Is supplied to the processing liquid storage tank 5 by the third supply machine 7. In addition, about the range of the predetermined value of pH of a process liquid, it changes with the kind of waste, and the kind of phosphoric acid.

  In the case of liquid phosphoric acids, the 3rd supply machine 7 may supply as it is to the process liquid storage tank 5, or may supply it as aqueous solution. In the case of solid phosphoric acids, it may be supplied as it is, or may be supplied as an aqueous solution or slurry.

  When a vacuum belt filter system is used for the gypsum separator of the flue gas evacuation device, it is common to use wash water for the purpose of washing impurities of by-product gypsum. Phosphoric acids are supplied to this wash water. However, the effect of the present invention can be obtained by using it. This method is effective in the sense that it uses existing equipment and does not add special equipment for stabilization.

  A second supply means is realized including the processing liquid storage tank 5, the second supply machine 6, the third supply machine 7, the processing liquid supply pump 21, the processing liquid supply pipe 22, and the processing liquid supply nozzle part 41 described above. By the second supply means, the dehydrated cake layer 14 is 2 parts by weight or more and 15% by weight in terms of phosphoric acid equivalent so that the phosphorus content is the same with respect to 1 part by weight of fluorine contained in the dehydrated cake. The phosphoric acid solution containing 5 parts by weight or more and less than 10 parts by weight can be permeated with respect to 10 parts by weight of the dehydrated cake. Thereby, the phosphoric acid contained in the filtrate 15 obtained by allowing the phosphoric acid solution to permeate the dehydrated cake layer 14 can be reduced. Moreover, since the fluorine contained in the filtrate 15 is a trace amount, the post-treatment of the filtrate 15 becomes easy. When phosphoric acid contains less than 2 parts by weight of phosphoric acid equivalent weight converted so that the phosphorus content is the same with respect to 1 part by weight of fluorine contained in dehydrated cake layer 14 , The amount of fluorine elution is not sufficiently reduced. In addition, when 1 part by weight of fluorine contained in the dehydrated cake layer 14 contains 15 parts by weight or more of phosphoric acid in terms of equivalent weight of phosphoric acid so that the phosphorus content is the same, a stabilization treatment is performed. After that, the hydrogen ion concentration index of the produced dehydrated cake becomes 6.5 or less. Therefore, the amount of phosphoric acid contained in the phosphoric acid solution is determined by the fluorine content and the hydrogen ion concentration index of the product produced by the stabilization treatment, and the stabilization treatment is performed according to the fluorine content in the gypsum slurry. In the case of treating waste having a low hydrogen ion concentration index of the product produced by the operation, the amount of phosphoric acid contained in the phosphoric acid solution is reduced.

  The pH of the filtrate stored in the filtrate storage tank 18 is 4.5 or less, preferably 4.0 or less, and phosphoric acids are added to the treatment liquid storage tank 5 by the third feeder 7. By supplying, the knowledge that the amount of fluorine elution from the dehydrated cake could be reduced to the soil environmental standard value or less was obtained.

  Moreover, in the stabilization apparatus 1, after dehydrating the gypsum slurry whose hydrogen ion concentration index is adjusted to 7.0 or more and less than 8.6, the phosphoric acid solution is permeated through the dehydrated cake layer 14 generated by dehydration. Then, since the phosphoric acid solution is brought into contact with the dehydrated cake layer 14, the gypsum slurry is dehydrated before the product produced by the reaction of the phosphoric acids is generated, so that moisture remains in the gypsum. Is suppressed, and good dehydrating properties can be obtained. The dehydrated cake layer 14 has 2 parts by weight or more and less than 15 parts by weight with respect to 1 part by weight of fluorine contained in the dehydrated cake layer 14 in terms of phosphoric acid equivalent weight so that the phosphorus content is the same. The amount of phosphoric acid to be used can be minimized by bringing phosphoric acid solution into contact with 10 parts by weight of the dehydrated cake and 5 parts by weight or more and less than 10 parts by weight of the phosphoric acid solution. The gypsum that is a dehydrated cake with reduced fluorine elution amount can be efficiently produced by reducing the phosphoric acids contained in the filtrate produced in the above process. Moreover, the stabilization apparatus 1 can obtain a gypsum with reduced fluorine elution amount by minimizing new additional equipment without stabilizing the fluorine with many chemicals, and is economical and reduces the environmental load. be able to. Furthermore, since the addition amount of the chemicals which are phosphoric acids and alkaline substances or acid substances is adjusted by the fluorine content and hydrogen ion concentration index in gypsum, it can be applied to a wide variety of wastes.

  In the present embodiment, a vacuum belt filter type is used as the dehydrator 4, but in another embodiment of the present invention, after adding an alkaline substance, the water in the gypsum slurry is removed to obtain a solid liquid. About the system to isolate | separate, the system using a centrifugal force may be sufficient as long as it is a system which removes moisture effectively.

  In the present embodiment, the slurry of waste is a gypsum slurry, but the slurry of waste may be, for example, dewatered sludge and dust collection dust slurry, and these wastes are similarly stabilized. That is, the amount of fluorine eluted can be reduced. When the acid substance is supplied to the slurry agitation tank 2 by the first supply unit 3, the acid substance may be the aforementioned inorganic acids such as phosphoric acids, sulfuric acid and nitric acid, or may be an organic acid such as acetic acid. Good.

  FIG. 4 is a diagram systematically illustrating the configuration of the stabilization processing apparatus 40 according to the second embodiment of the present invention. The stabilization processing apparatus 40 of this embodiment is adapted to a vacuum belt filter type dehydrator. In the stabilization processing apparatus 40, the same components as those of the stabilization processing apparatus 1 of the embodiment shown in FIG. 1 described above are denoted by the same reference numerals, and the description thereof may be omitted. In addition to the configuration of the stabilization processing apparatus 1 shown in FIG. 1, the stabilization processing apparatus 40 includes a filtrate supply pump 81 for supplying the filtrate once permeated through the dewatering cake layer 14 to the dehydrator 4. The second filtrate storage tank 18b for storing the filtrate that has passed through the dewatered cake layer 14 again is configured.

  FIG. 5 is a plan view schematically illustrating the transport unit 31 of the dehydrator 4 in the stabilization processing apparatus 40, and FIG. 6 is a cross-sectional view schematically illustrating the transport unit 31 of the dehydrator 4 in the stabilization processing apparatus 40. It is. In the present embodiment, the dehydrator 4 is provided with a filtrate supply nozzle portion 51. The filtrate is supplied to the filtrate supply nozzle section 51 via the filtrate supply pipe 52, and the filtrate supply nozzle section 51 discharges the supplied filtrate vertically downward. The filtrate supply nozzle 51 is provided at a predetermined distance T3 upward from the placement surface of the belt 34. The predetermined distance T3 is selected so as to be larger than the thickness of the dehydrated cake layer 14 on the placement surface of the overhanging portion 35. The filtrate supply nozzle 51 discharges the supplied filtrate over both ends of the belt 34 in the width direction. As a result, the filtrate can permeate the dehydrated cake layer 14 over the entire region in the width direction of the dehydrated cake layer 14 mounted on the belt 34.

  In the present embodiment, the vacuum tray unit 37 includes a first vacuum tray unit 37a and a second vacuum tray unit 37b. The first vacuum tray portion 37a is provided between both end portions in the width direction of the belt 34, and from the position where the processing liquid supply nozzle 41 is provided in the transport direction to the downstream side in the transport direction from the processing liquid supply nozzle portion 41. Extend. The second vacuum tray 37b is provided between both end portions in the width direction of the belt 34, and in the transport direction from the upstream in the transport direction to the downstream in the transport direction of the filtrate supply nozzle 51 from the slurry supply nozzle unit 30. It extends to the vicinity of the processing liquid supply nozzle 41.

  A suction force is guided to the first vacuum tray 37a via a first filtrate suction pipe 17a that guides a suction force from the first vacuum pump 16a. As a result, the dehydrated cake layer 14 to which the processing liquid discharged from the processing liquid supply nozzle 41 is supplied is filtered by suction, and the dehydrated cake and the filtrate 15a obtained by passing the processing liquid through the dehydrated cake layer 14 are obtained. Solid-liquid separation. The suction force is guided to the second vacuum tray 37b via the second filtrate suction pipe 17b that guides the suction force from the second vacuum pump 16b. Thus, the dehydrated cake layer 14 supplied with the filtrate discharged from the filtrate supply nozzle 51 together with the liquid contained in the gypsum slurry is suction filtered, and supplied from the dehydrated cake and the filtrate supply nozzle 51. The filtrate is solid-liquid separated into a filtrate 15b obtained by passing through the dehydrated cake layer 14.

  The filtrate supply nozzle part 51 is provided between the slurry liquid supply nozzle part 30 and the processing liquid supply nozzle part 41 in the transport direction. The filtrate supply nozzle 51 and the slurry supply nozzle 30 are separated by a predetermined distance T4, and the filtrate supply nozzle 51 and the treatment liquid supply nozzle 41 are separated by a predetermined distance T5. The predetermined distance T4 is selected so that the moisture content of the dehydrated cake layer 14 at the position where the filtrate is supplied from the filtrate supply nozzle 51 is about 20%. The slurry of gypsum supplied from the slurry supply nozzle unit 30 is conveyed while being dehydrated, and the filtrate is supplied from the filtrate supply nozzle unit 51 to a position where the moisture content is about 20%. The predetermined distance T5 is such that the water content of the dehydrated cake layer 14 at the position where the processing liquid is supplied from the processing liquid supply nozzle 41 is about 20%, and the filtrate supplied from the filtrate supply nozzle 51 is The processing liquid supplied from the processing liquid supply nozzle unit 41 is selected so as not to be mixed as much as possible. Thus, also in this apparatus, the dehydration process and the process of supplying the treatment liquid to the dehydrated cake can be performed continuously. In the dehydrated cake layer 14, the moisture content of the portion on the downstream side in the transport direction from the position where the treatment liquid is supplied is about 10%. On the downstream side in the transport direction, the dehydrated cake layer 14 is unloaded from the end of the belt 34 on the downstream side in the transport direction, so that the processed dehydrated cake is obtained.

  Referring to FIG. 4 again, the filtrate 15a sucked by the first vacuum pump 16a is stored in the first filtrate tank 61a via the first filtrate suction pipe 17a. The first filtrate tank 61a is provided to separate the filtrate 15a sucked by the first vacuum pump 16a from the air. In the first filtrate tank 61a, the filtrate 15a from the first filtrate suction pipe 17a is stored, and the first vacuum pump suction pipe 62a is connected, and the suction force from the first vacuum pump 16a is guided. It is burned. The first vacuum pump 16a sucks the air inside the first filtrate tank 61a through the first vacuum pump suction pipe 62a. The first vacuum pump suction pipe 62a and the first filtrate suction pipe 17a are provided above the liquid level of the filtrate 15a stored in the first filtrate tank 61a, and the first vacuum pump suction pipe 62a is The first filtrate tank 61a is provided above the one filtrate suction pipe 17a. Thereby, the first vacuum pump 16a can suck only the air in the first filtrate tank 61a. By sucking the air in the first filtrate tank 61a, a suction force can be guided to the first filtrate suction pipe 17a.

  A first filtrate discharge pipe 63a is connected to the lower part of the first filtrate tank 61a, and the first filtrate discharge pipe 63a is connected to the first filtrate storage tank 18a. The filtrate 15a in the first filtrate tank 61a is transferred to the first filtrate storage tank 18a via the first filtrate discharge pipe 63a and stored in the first filtrate storage tank 18a.

  The filtrate 15b sucked by the second vacuum pump 16b is stored in the second filtrate tank 61b via the second filtrate suction pipe 17b. The second filtrate tank 61b is provided to separate the filtrate 15b sucked by the second vacuum pump 16b from the air. In the second filtrate tank 61b, the filtrate 15b from the second filtrate suction pipe 17b is stored, and a second vacuum pump suction pipe 62b is connected, and the suction force from the second vacuum pump 16b is guided. It is burned. The second vacuum pump 16b sucks the air inside the second filtrate tank 61b via the second vacuum pump suction pipe 62b. The second vacuum pump suction pipe 62b and the second filtrate suction pipe 17b are provided above the liquid level of the filtrate 15b stored in the second filtrate tank 61b, and the second vacuum pump suction pipe 62b is The second filtrate tank 61b is provided above the second filtrate suction pipe 17b. As a result, the second vacuum pump 16b can suck only the air in the second filtrate tank 61b. By sucking the air in the second filtrate tank 61b, a suction force can be guided to the second filtrate suction pipe 17b.

  A second filtrate discharge pipe 63b is connected to the lower part of the second filtrate tank 61b, and the second filtrate discharge pipe 63b is connected to the second filtrate storage tank 18b. The filtrate 15b in the second filtrate tank 61b is transferred to the second filtrate storage tank 18b via the second filtrate discharge pipe 63b and stored in the second filtrate storage tank 18b.

  The filtrate 15 a stored in the first filtrate storage tank 18 a is provided to the filtrate supply nozzle unit 51 by a filtrate supply pump 81 through a conduit formed by the filtrate supply pipe 52.

  In the case of the vacuum belt filter type dehydrator 4, when the moving speed of the belt 34 is high and the thickness of the dehydrated cake layer 14 is thin, the phosphorus contained in the process liquid is passed through the dehydrated cake 14. Due to the short residence time of the acids in the dehydrated cake layer 14 and the short permeation time, the contact between the treatment liquid and the dehydrated cake layer 14 becomes insufficient. As a result, the reaction time between the phosphoric acid contained in the treatment liquid and the alkaline substance contained in the dehydrated cake layer 14 is not sufficient, so that the phosphoric acid remains in the filtrate, that is, phosphorus is added to the filtrate that has passed through the dehydrated cake layer 14. Acids may remain. In this case, simply passing the phosphoric acid solution once through the dehydrated cake layer 14 leaves unreacted phosphoric acid in the filtrate, and the supplied phosphoric acid is wasted. Therefore, the filtrate obtained by the treatment liquid supplied from the treatment liquid supply nozzle 41 to the dehydrated cake layer 14 once passing through the dehydrated cake layer 14 is temporarily stored in the first filtrate storage tank 18a. The filtrate stored in one filtrate storage tank 18a is repeatedly permeated through the dehydrated cake layer. Thereby, the amount of chemicals can be reduced, that is, the amount of phosphoric acids used in the treatment can be reduced. In addition, the stabilization processing apparatus 40 can achieve the same effect as that of the stabilization processing apparatus 1 described above, and performs the process of repeatedly allowing the filtrate to permeate the dehydrated cake layer 14, so that the phosphor used for the processing can be obtained. The amount of acids can be further reduced. The treatment of allowing the filtrate to permeate the dehydrated cake layer 14 is also effective for suppressing the phosphates from remaining in the filtrate, and the phosphates remain in the second filtrate storage tank 18b. Since this can be suppressed, the waste liquid can be easily treated. A third supply means is realized including the first filtrate storage tank 18a, the filtrate supply pump 81, the filtrate supply pipe 52, and the filtrate supply nozzle portion 51.

  The pH of the filtrate stored in the first filtrate storage tank 18a is 5.5 or less, desirably 5.0 or less, and the filtrate stored in the second filtrate storage tank 18b. By supplying the phosphoric acid treatment liquid storage tank 5 by the third supply unit 7 so that the pH value of the liquid is 6.5 or less, preferably 6.0 or less, the amount of fluorine elution from the dehydrated cake is reduced. The knowledge that it can be below the soil environmental standard value was obtained.

  Moreover, in the stabilization processing apparatus 40 of this Embodiment, if a process liquid is not supplied to the dewatering cake layer 14, a filtrate will not be produced | generated, but until a filtrate is stored by the 1st filtrate storage tank 18a, A dehydrated cake similar to that of the stabilization processing apparatus 1 of the above-described embodiment can be generated.

  In another embodiment of the present invention, the filtrate obtained by permeating the dehydrated cake layer 14 may be repeatedly permeated through the dehydrated cake layer 14. Since the treatment of allowing the filtrate to permeate the dehydrated cake layer 14 is also effective for preventing the phosphates from remaining in the filtrate, the number of repetitions is not limited to two. There may be times or more.

  Hereinafter, the present invention will be described in detail by way of examples. FIG. 7 and FIG. 8 are diagrams showing a batch-type confirmation test procedure performed to confirm the stabilization processing method of the present invention.

  As the gypsum slurry, a gypsum slurry having the properties shown in Table 1 was used. Table 1 shows the concentration of gypsum slurry, the pH of the filtrate obtained by filtering the gypsum slurry, and the fluorine content, elution amount, and pH of gypsum.

  In Table 1, the fluorine content in gypsum is that in gypsum dried at 45 ° C. for 24 hours. The fluorine elution amount was in accordance with the dissolution test (Environmental Agency Notification No. 46). The fluorine content in gypsum is based on JIS R 9101, using a distillate of steam distillation, adding a buffer solution (total ionic strength adjusting solution), and adjusting to pH = 5.0 to 5.5, The potential was measured using a fluoride ion electrode.

  The amount of fluorine dissolved in gypsum conformed to the dissolution test (Environment Agency Notification No. 46). The sample is 50 g or more with 500 mL or more (pH = 5.8 to 6.3) using pure water as a solvent, and placed in a 1 L plastic container. Shake horizontally (shaking width 4 cm to 5 cm, room temperature about 20 ° C.) for 6 hours about 200 times per minute, let stand for 10-30 minutes, centrifuge at about 3000 rpm for 20 minutes, and supernatant The liquid was suction filtered using a membrane filter having a filter paper pore diameter of 0.45 μm. The fluorine concentration in the filtrate was measured with a fluorine ion electrode. The ion electrode method was in accordance with JIS R 9101.

Example 1
In Example 1, gypsum stabilization processing was performed by the stabilization processing method of the first embodiment.

  Gypsum slurry produced by stirring gypsum (160 g) in water (about 600 g) (slurry concentration 21.0 wt%, about 760 g) is placed in a 1 L beaker and stirred against gypsum contained in the gypsum slurry. 0.40 wt% (0.64 g) of slaked lime was added, and the mixture was sufficiently stirred until pH = 8.3. The stirring time was about 10 minutes. Next, it moves to the filtration a step, and the slurry of gypsum stirred with slaked lime is suction filtered over about 10 minutes, so that the water content becomes about 8%, and gypsum (gypsum a) and filtrate (filter) Solid-liquid separation into liquid a). Next, washing water (pH = 1.84) in which 0.78 wt% phosphoric acid (about 1.25 g) is diluted with distilled water to 100 mL with respect to gypsum (gypsum a) contained in the gypsum slurry, The mixture was passed through gypsum a, moved to the filtration b step, washed with suction filtration, and solid-liquid separated into filtrate (filtrate b) and gypsum (gypsum b). After gypsum b was left in a dryer at 45 ° C. for 24 hours to dry, the elution test (Environment Agency Notification No. 46) was conducted. As a result, the elution amount of fluorine was 0.5 [mg / L]. The pH of this was 6.6. The results are shown in Table 2.

(Example 2)
In Example 2, the gypsum stabilization process was performed by the stabilization process method of the first embodiment.

  Gypsum slurry produced by stirring gypsum (160 g) in water (about 600 g) (slurry concentration 21.0 wt%, about 760 g) is placed in a 1 L beaker and stirred against gypsum contained in the gypsum slurry. 0.27 wt% (0.43 g) of slaked lime was added, and the mixture was sufficiently stirred until pH = 8.1. The stirring time was about 10 minutes. Next, it moves to the filtration a step, and the gypsum slurry in which the slaked lime is stirred is subjected to suction filtration for about 10 minutes, so that the water content becomes about 8% and the gypsum (gypsum a) and the filtrate (filtrate). Solid-liquid separation into a). Next, with respect to the gypsum (gypsum a) contained in the gypsum slurry, washing water (pH = 2.28) obtained by diluting 0.51 wt% phosphoric acid (0.82 g) with distilled water to 100 mL is used. Then, the process moves to the filtration step b, and is washed while being suction filtered. The filtrate is filtrated (filtrate b) and gypsum (gypsum b). After gypsum b was left in a dryer at 45 ° C. for 24 hours to dry, the elution test (Environment Agency Notification No. 46) was conducted. As a result, the elution amount of fluorine was 0.7 [mg / L]. PH was 7.5. The results are shown in Table 2. In Example 2, since the concentration of phosphoric acid was lower than that in Example 1, the amount of elution of fluorine was higher than that in Example 1.

(Example 3)
In Example 3, the gypsum stabilization process was performed by the stabilization process method of the second embodiment.

  Gypsum slurry produced by stirring gypsum (160 g) in water (about 600 g) (slurry concentration 21.0 wt%, about 760 g) is placed in a 1 L beaker and stirred against gypsum contained in the gypsum slurry. 0.27 wt% (0.43 g) of slaked lime was added, and the mixture was sufficiently stirred until pH = 8.1. The stirring time was 10 minutes. Next, it moves to the filtration c step, and the gypsum slurry in which the slaked lime is stirred is subjected to suction filtration over about 10 minutes, so that the water content becomes about 8%, and the gypsum (gypsum c) and the filtrate (filtrate). c).

  The filtrate (filtrate b) (pH = 5.19, 100 mL) once permeated through the gypsum cake is passed through the gypsum (gypsum c) and treated with suction filtration. The filtrate (filtrate d) and gypsum Solid-liquid separation into (gypsum d). Next, wash water (pH = 2.28) obtained by diluting 0.51 wt% phosphoric acid (0.82 g) with distilled water to 100 mL was obtained with respect to the gypsum (gypsum d) separated into solid and liquid. The mixture was permeated through d), treated with suction filtration, solid-liquid separated into filtrate (filtrate e) and gypsum (gypsum e), and gypsum e washed twice in total. The gypsum e obtained by the treatment of this example was left to dry in a dryer at 45 ° C. for 24 hours, and then subjected to a dissolution test (Environment Agency Notification No. 46). .2 [mg / L] or less, the pH of gypsum was 7.1. The results are shown in Table 2. Despite the small amounts of phosphoric acid and slaked lime used compared to Example 1, the elution amount of fluorine was lower than that of Example 1.

Example 4
In Example 4, the papermaking sludge was used as the waste slurry, and the stabilization method of the second embodiment was performed.

  Paper sludge ash (fluorine content: 259 mg / kg, fluorine elution amount: 2.4 mg / L) 760 g of slurry (slurry concentration: 20 wt%) was placed in a 1 L beaker and stirred for 10 minutes, pH = 11.0. Therefore, 40 g of sulfuric acid was added, and the mixture was stirred for 10 minutes to adjust the pH to 8.4 and suction filtered. Thereafter, 0.26 wt% phosphoric acid (0.40 g) was diluted with distilled water to make 100 mL of washing water (pH = 4.1) with respect to the paper sludge ash, and further passed through the dehydrated cake. The filtrate again passed through the dehydrated cake. As a result of leaving and drying in a dryer at 45 ° C. for 24 hours and conducting a dissolution test (Environment Agency Notification No. 46), the amount of fluorine dissolution was 0.2 [mg / L] or less, and the pH of the papermaking sludge ash Was 8.3.

  The dehydrated cake obtained by adding the alkaline substance to about half the amount of phosphoric acid and the pH of about 8.0 by the procedure of Example 1 described above was dried at 45 ° C. for 24 hours. After leaving it to dry and performing a dissolution test (Environment Agency Notification No. 46) and measuring the amount of fluorine eluted, it was about 2 to 15 times the fluorine content contained in the dehydrated cake It was found that the solution containing the phosphoric acid of the above could be passed through this dehydrated cake. That is, 2 parts by weight or more and less than 15 parts by weight of phosphoric acid equivalent to the phosphoric acid equivalent weight converted so that the phosphorus content is the same with respect to 1 part by weight of fluorine contained in the dehydrated cake. It was found that the permeation amount of fluorine can be reduced below the environmental standard value by permeation.

It is a figure which shows systematically the stabilization processing apparatus 1 of the 1st Embodiment of this invention. It is a top view which shows typically the conveyance part 31 of the dehydrator 4 in the stabilization processing apparatus 1. FIG. It is sectional drawing which shows typically the conveyance part 31 of the dehydrator 4 in the stabilization processing apparatus 1. FIG. It is a figure which shows systematically the structure of the stabilization processing apparatus 40 of the 2nd Embodiment of this invention. FIG. 3 is a plan view schematically showing a transport unit 31 of the dehydrator 4 in the stabilization processing device 40. 3 is a cross-sectional view schematically showing a transport unit 31 of the dehydrator 4 in the stabilization processing apparatus 40. FIG. It is a figure which shows the confirmation test procedure of the batch system implemented in order to confirm the stabilization processing method of this invention. It is a figure which shows the confirmation test procedure of the batch system implemented in order to confirm the stabilization processing method of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,40 Stabilization apparatus 2 Slurry stirring tank 3 1st supply machine 4 Dehydrator 5 Process liquid storage tank 6 2nd supply machine 7 3rd supply machine 11 1st supply pipe 12 Slurry supply pump 13 Slurry supply pipe 14 Dehydration cake Layers 15, 15a, 15b Filtrate 16 Vacuum pump 16a First vacuum pump 16b Second vacuum pump 17 Filtrate suction tube 17a First filtrate suction tube 17b Second filtrate suction tube 18 Filtrate storage tank 18a First filtrate Reservoir 18b Second filtrate reservoir 21 Treatment liquid supply pump 22 Treatment liquid supply pipe 30 Slurry supply nozzle part 31 Conveying part 32 Housing 33, 46 Roller
34 Belt 35 Upper tension part 36 Lower tension part 37 Vacuum tray part 37a First vacuum tray part 37b Second vacuum tray part 38 Lower tray 41 Treatment liquid supply nozzle part 45 Drive part 47 Air cylinder 48 Displacement allowance part 49 Support roller 51 Filtrate supply nozzle section 52 Filtrate supply pipe 61 Filtrate tank 61a First filtrate tank 61b Second filtrate tank 62 Vacuum pump suction pipe 62a First vacuum pump suction pipe 62b Second vacuum pump suction pipe 63 Filtrate discharge Pipe 63a First filtrate discharge pipe 63b Second filtrate discharge pipe 71 Weight roller 72 Inclined member 73 Washing part 81 Filtrate supply pump

Claims (4)

Stir alkaline substance or acid substance into the slurry of waste so that the hydrogen ion concentration index of the slurry is 7.0 or more and less than 8.6,
The slurry in which the alkaline substance or acid substance is stirred is dehydrated to form a dehydrated cake,
2 parts by weight or more and less than 15 parts by weight of phosphoric acid equivalent in terms of phosphoric acid equivalent weight so that the phosphorus content is the same with respect to 1 part by weight of fluorine contained in the dehydrated cake, and the dehydrated cake 10 A waste stabilization method, wherein 5 parts by weight or more and less than 10 parts by weight of a phosphoric acid solution is permeated through the generated dehydrated cake with respect to parts by weight.   2. The waste stabilization method according to claim 1, wherein a filtrate obtained by allowing the phosphoric acid solution to permeate the dehydrated cake is permeated through the dehydrated cake. A stirring tank;
First supply means for supplying an alkaline substance or an acid substance to the stirring tank so that the hydrogen ion concentration index of the slurry of the waste put in the stirring tank is 7.0 or more and less than 8.6;
Dehydrating means for dewatering the slurry of the waste material stirred by the alkaline substance or acid substance supplied by the first supplying means to produce a dehydrated cake;
2 parts by weight or more and less than 15 parts by weight of phosphoric acid equivalent in terms of phosphoric acid equivalent weight so that the phosphorus content is the same with respect to 1 part by weight of fluorine contained in the dehydrated cake, and the dehydrated cake 10 A waste stabilization treatment apparatus comprising: a second supply unit configured to supply a phosphoric acid solution of 5 parts by weight or more and less than 10 parts by weight to the dehydrated cake with respect to parts by weight. A filtrate storage tank for storing a filtrate obtained by allowing the phosphoric acid solution to permeate the dehydrated cake;
The waste stabilization processing apparatus according to claim 3, further comprising a third supply unit that supplies the dehydrated cake with the filtrate stored in the filtrate storage tank.

Images