JP5888720B2 - Fertilizer manufacturing method and rotary surface melting furnace used in fertilizer manufacturing method - Google Patents

Description

  The present invention is a fertilizer comprising: a melting process step for melting a melt containing phosphorus-containing sludge or phosphorus-containing incinerated ash; and a cooling process step for cooling and solidifying the slag melted in the melting process step. The present invention relates to a rotary surface melting furnace used in the manufacturing method and fertilizer manufacturing method.

  Recovering phosphorus resources from waste has become an important issue in Japan, which is 100% dependent on foreign countries for phosphorus ore, which is necessary for the production of phosphorus fertilizer and industrial phosphoric acid. In particular, phosphorus concentrated in sewage sludge may account for 30% or more of imported phosphorus ore, and various attempts have been made to produce fertilizers containing phosphorus from sewage sludge.

  For example, in Patent Document 1, the total phosphoric acid concentration of raw material incineration ash is measured, and when the total phosphoric acid concentration is lower than a predetermined target product concentration, the addition of high phosphorus-containing waste before melting treatment A method is disclosed in which a proportion is obtained, added to the raw material, melted, and then rapidly cooled to produce phosphorus fertilizer. According to this document, when the concentration of phosphoric acid contained in the sludge is low, the dissolution rate of phosphorus in the slag fertilizer becomes low. A method for producing a fertilizer that yields a rate is disclosed.

JP 2006-1819 A

  However, in the technique disclosed in Patent Document 1, it is necessary to mix other phosphorus raw materials into sludge so that the dissolution rate of the manufactured fertilizer falls within the target range, and the production cost of phosphorus fertilizer increases. There was a problem.

  In view of the above-described problems, an object of the present invention is a fertilizer capable of adjusting the dissolution rate of phosphorus contained in the produced fertilizer without mixing other phosphorus raw materials into the sludge as the fertilizer raw material. It exists in the point which provides the rotary surface melting furnace used for the manufacturing method and the manufacturing method of a fertilizer.

In order to achieve the above-mentioned object, the first characteristic configuration of the fertilizer manufacturing method according to the present invention is to melt a melt containing phosphorus-containing sludge or phosphorus-containing incinerated ash as described in claim 1 of the claims. A fertilizer manufacturing method comprising: a melting processing step to be processed; and a cooling processing step for cooling and solidifying the slag melted in the melting processing step, using optical basicity as an index for evaluating slag The amount of the skeletal conditioner obtained in this way is added to the melt, and the ratio of the soluble phosphorus weight to the total phosphorus weight contained in the slag solidified in the cooling treatment step is adjusted to exceed a predetermined value. The skeleton adjusting agent adding step is provided in a stage prior to the melting treatment step .

In the actual structure, silicic acid constituting the slag skeleton melted in the melting process step and solidified in the cooling process step is connected by a three-dimensional network in which the SiO ₄ tetrahedron is irregularly arranged with oxygen O as a bridge. ing. That is, four oxygen SiO _4, while making the SiO ₄ tetrahedra surrounds the orbits of the four vertices of silicon Si make, oxygen O is infinite network structure bonded with other another silicon Si is made . Such oxygen O that connects silicon Si is called bridging oxygen. Similarly, the phosphoric acid P ₂ O ₅ contained in the slag is bonded with phosphorus P to bridging oxygen to form an infinite network structure. When a cation such as a metal ion is contained in such a slag component, a part of the oxygen O to be bonded to silicon Si or phosphorus P is cut and is in an ionic balance with the cation. become. Such oxygen O is called non-bridging oxygen. When non-bridging oxygen increases in the slag, the slag skeleton strength becomes weak and easily collapses.

  As a result of intensive research, the inventors of the present application have found that when the number of non-bridging oxygen in the slag increases with respect to the slag mainly composed of a network structure of bridging oxygen, the solubility of phosphoric acid, which is a fertilizer component, increases. Confirmed the fact that it rises. And by adding a skeletal modifier to the phosphorus-containing sludge or phosphorus-containing incinerated ash in the previous stage of the melting treatment step, it becomes possible to adjust the number of non-crosslinked oxygen in the slag, and the amount of the skeleton modifier added As a result of the adjustment, a new finding has been obtained that the ratio of the soluble phosphorus weight to the total phosphorus weight contained in the slag solidified in the cooling treatment step can be adjusted to exceed a predetermined value.

That is, even if other phosphorus raw materials are not mixed in phosphorus-containing sludge or phosphorus-containing incinerated ash, if the skeleton modifier is simply added and melted, the skeletal structure of the slag solidified in the cooling process step becomes weak. The ratio of the soluble phosphorus weight to the total phosphorus weight contained in the slag can be increased .

The present gun inventors, as an indicator to further evaluate the slug has been found that it is possible to use optical basicity as an index. Optical basicity is an index found by Duffy and Ingram, focusing on the fact that the ultraviolet light absorption peak changes sensitively with respect to the glass composition. Is an index that is derived from the electronegativity of the cation constituting s based on the following formula.

Optical basicity Λ = 1−Σ (zi · ri / 2) · (1-1 / γi)
However, γi = 1.36 (χi−0.26)
Here, zi is the valence of the i-type cation, ri is the number of the i-type cation expressed per oxygen, and χi is the electronegativity of the i-type cation.

Optical basicity are the value obtained by analyzing the composition of the melt or slag containing Li down-containing sludge or phosphorus-containing ash, the ratio of click-soluble phosphorus weight relative to the total phosphorus weight contained in slag if Sadamare optically basicity to above a predetermined value, it is possible to adjust the amount of skeletal modifier to obtain optically basicity like it.

As described in claim 2 , the second feature configuration includes the amount of the skeleton modifier added in the skeleton modifier addition step in addition to the first feature configuration described above. The optical basicity of the slag solidified in step 1 is obtained by analyzing the composition of the melt beforehand so that the ratio of the soluble phosphorus weight to the total phosphorus weight contained in the slag exceeds a predetermined value. The value is adjusted based on the basicity .

The optical basicity is a value obtained by analyzing the composition of phosphorus-containing sludge or phosphorus-containing incinerated ash in advance, so that the ratio of the soluble phosphorus weight to the total phosphorus weight contained in the slag exceeds the predetermined value. Once the basic basicity is determined, it becomes possible to adjust the amount of the skeletal modifier for obtaining such optical basicity in advance. Therefore, it is not necessary to measure the optical basicity of the slag.

In the third feature configuration, as described in claim 3, in addition to the first feature configuration described above, the addition amount of the skeleton modifier added in the skeleton modifier addition step is the cooling treatment step. The optical basicity of the slag solidified in (1) is obtained by analyzing the composition of the melt in advance so that the ratio of the soluble phosphorus weight to the total phosphorus weight contained in the fertilizer containing the slag exceeds a predetermined value. The value is adjusted based on the optical basicity.

Not only when using the fertilizer which consists only of slag manufactured by the 1st characteristic structure mentioned above, but also the other fertilizer may be mixed and used for the said slag. In the latter case, it is necessary to adjust the ratio of the soluble phosphorus weight to the total phosphorus weight in the mixed fertilizer as a whole. Even in such a case, if found to phosphorus click溶率other fertilizers, by adjusting the amount of skeletal modifiers, adjusting the click溶率phosphorus of the total mixed fertilizers Will be able to.

In the fourth feature configuration, as described in claim 4, in addition to any one of the first to third feature configurations described above, the skeleton modifier adding step is executed before the melting processing step. In the point.

After the skeletal modifier added in the skeleton modifier adding step is homogeneously mixed with the melt, the melting treatment step is performed.

In addition to the fourth feature configuration described above, the fifth feature configuration is surplus sludge generated in a water treatment step in which the phosphorus-containing sludge is biologically treated to purify raw water. And the skeletal conditioner adding step is performed on the excess sludge extracted in the water treatment step.

By adding a skeletal modifier to the excess sludge extracted in the water treatment step, the skeleton modifier can be efficiently and uniformly dispersed in the sludge.

In addition to the fourth feature configuration described above, the sixth feature configuration is surplus sludge generated in a water treatment step in which the phosphorus-containing sludge is biologically treated to purify raw water. And the skeletal regulator addition step is performed on the raw water before being biologically treated in the water treatment step.

In the seventh characteristic configuration, as described in claim 7, in addition to the sixth characteristic configuration described above, the skeleton adjusting agent used in the skeleton adjusting agent adding step is a water-insoluble skeleton adjusting agent. In the point.

Since the water-insoluble skeleton modifier is added, the skeleton modifier is efficiently dispersed in the sludge without dissolving in the treated water.

In the eighth feature, as described in claim 8, in addition to any of the first to third features described above, the skeletal modifier addition step includes the phosphorus-containing sludge or the phosphorus-containing incineration. It is in a point that is performed against ash.

In the ninth feature configuration, as described in claim 9 , in addition to any of the first to eighth feature configurations described above, the skeleton modifier added in the skeleton modifier addition step is an alkali. One or more kinds of simple metals or metal compounds selected from metals, alkaline earth metals, and transition metals. Alkaline metals, alkaline earths as cations required to adjust the slag skeleton strength One kind or plural kinds of simple metals or metal compounds selected from a similar metal or a transition metal can be preferably used.

In the tenth feature, as described in claim 10 , in addition to any one of the first to ninth features described above, the skeleton modifier added in the skeleton modifier addition step is sodium. , Potassium, calcium, magnesium, iron, manganese, copper, zinc, or one or more kinds of simple metals or metal compounds.

  When using one or more kinds of simple metals or metal compounds selected from potassium, calcium, magnesium, iron, manganese, copper, and zinc as skeletal modifiers to weaken slag and promote phosphorus elution, they themselves Becomes an indispensable fertilizer component for plants, and a fertilizer with better quality can be obtained. For example, if sodium, potassium, calcium, or iron metal alone or a metal compound is used as a skeletal modifier, the melting point of sludge can be lowered in the melting step, and external energy such as fossil fuel and electric power for melting. Consumption can be reduced. Further, when an iron metal simple substance or a metal compound is used, it can be alloyed with phosphorus to raise its boiling point, and the phosphorus component can be effectively prevented from vaporizing during the melting treatment. Thus, the skeleton modifier has a role of a melting point controlling material, and the melting point can be controlled.

In the eleventh characteristic configuration, as described in claim 11 , in addition to any of the first to tenth characteristic configurations described above, iron is added to the skeleton adjusting agent added in the skeleton adjusting agent adding step. Alternatively, the compound is contained, and the melting step is performed in a reducing atmosphere or an oxidizing atmosphere .

When the framework modifier added in the framework modifier adding step contains iron or a compound thereof, the iron in the molten slag is in the form of Fe ₂ O ₃ when the melting treatment step is performed in an oxidizing atmosphere. Therefore, a slag having a high skeleton strength can be obtained. When the melting treatment step is performed in a reducing atmosphere, iron in the molten slag becomes a form of FeO, and a slag having a low skeleton strength can be obtained. That is, the dissolution rate of phosphorus contained in the slag can be adjusted depending on whether the atmosphere during melting is a reducing atmosphere or an oxidizing atmosphere.

In the twelfth feature, as described in claim 12, in addition to any one of the first to eleventh features described above, the melting treatment step may be performed at a slag temperature of 1000 ° C. to 1700 ° C. It is in the point which is performed under the condition adjusted in the range of ° C.

When melt processing is performed at a temperature higher than 1300 ° C., the viscosity of the slag is low, the slag skeleton approaches an energy-stable equilibrium state, and a slag having a high skeleton strength can be obtained. Since the slag skeleton does not reach an equilibrium state, a slag having a low skeleton strength can be obtained.

In the thirteenth feature configuration, as described in claim 13 , in addition to any of the first to thirteenth feature configurations described above, the melting treatment step may be configured such that the temperature of the slag is 1300 ° C. or lower. When it is melted at a temperature higher than 1300 ° C., the viscosity of the slag is low, the slag skeleton approaches an energy-stable equilibrium state, and the slag has a strong skeleton strength. When the melting treatment is performed at the following melting temperature, the slag has a high viscosity and the slag skeleton does not reach an equilibrium state, so that a slag having a low skeleton strength can be obtained.

In the fourteenth feature, as described in claim 14 , in addition to any one of the first to thirteenth features described above, the cooling treatment step is melted in the melting treatment step. The method includes a step of slowly cooling and solidifying the slag or a step of rapid cooling using a water cooling mechanism .

When the molten slag is cooled in the cooling process step, if the molten slag is rapidly cooled, such as by dropping it into a water tank, amorphous slag is obtained and phosphorus is incorporated into the amorphous skeleton, so the phosphorus elution rate Low slag. When the molten slag slow cooled by air cooling or the like, the slag crystalline entity is obtained, phosphorus because less likely to be taken in the crystalline framework, ing a high phosphorus dissolution rate slag.

The first characteristic configuration of the rotary surface melting furnace used in the method for producing a fertilizer according to the present invention is the fertilizer having any one of the first to fourteenth characteristic configurations described above, as described in claim 15. A rotary surface melting furnace used for the manufacturing method of the above, an inner cylinder standing around the ceiling portion where the combustor is disposed, and a bottomed outer cylinder having a bottom outlet formed in the center of the bottom portion, Is disposed around the common axis, and the melted material containing phosphorus-containing sludge or phosphorus-containing incinerated ash charged into the accumulating portion between the outer cylinder and the inner cylinder is disposed relative to the outer cylinder and the inner cylinder. By rotating, the inner cylinder is moved from the lower edge of the inner cylinder to the main combustion chamber in the lower space of the ceiling, the exposed surface is melted by the combustion flame of the combustor, and the molten slag is dropped and discharged from the outlet. The residence time is configured to adjust the residence time of the slag melted in the main combustion chamber There in that it includes an integer mechanism.

  By adjusting the residence time adjustment mechanism so that the residence time of slag becomes longer, the slag skeleton approaches an energy stable equilibrium state, and it becomes possible to produce fertilizers with a low dissolution rate and melting. The heavy metals contained in the slag can be sufficiently vaporized, and the heavy metal components contained in the fertilizer can be adjusted extremely low. Moreover, by adjusting so that the residence time of slag may become short with a residence time adjustment mechanism, a slag frame | skeleton will be in the weak state which does not reach an equilibrium state, and becomes a fertilizer with a high melt | dissolution rate.

In the second feature configuration, as described in claim 16 , in addition to the first feature configuration described above, the dwell time adjustment mechanism may cause the inner cylinder and the outer cylinder to move relative to each other in the common axis direction. It is realized by a distance adjusting mechanism that moves and adjusts the distance between the lower edge of the inner cylinder and the bottom of the outer cylinder.

  By adjusting the distance adjustment mechanism so that the distance between the lower edge of the inner cylinder and the bottom of the outer cylinder is narrowed, the amount of sludge, etc. that is the melt to be moved from the lower edge of the inner cylinder to the main combustion chamber is reduced. As a result, the slag melted from the surface can be secured for a long time until it flows out from the tap. Further, when the interval adjusting mechanism is adjusted so that the interval between the lower edge portion of the inner cylinder and the bottom portion of the outer cylinder is increased, the sludge that is a melted material moving from the lower edge portion of the inner cylinder to the main combustion chamber, etc. The amount of the slag melted from the surface can be adjusted to be short, and the time until the molten slag flows out from the spout is shortened.

The third characteristic configuration is a rotary surface melting furnace used in the method for manufacturing a fertilizer having any one of the first to fourteenth characteristic configurations as described in claim 17 , An inner cylinder erected around the ceiling where the combustor is disposed, and a bottomed outer cylinder with a tap hole formed in the center of the bottom are arranged around a common axis, and the outer cylinder and the inner cylinder The molten material containing phosphorus-containing sludge or phosphorus-containing incinerated ash charged into the accumulation part between the cylinder is moved from the lower edge of the inner cylinder to the lower part of the ceiling by the relative rotation of the outer cylinder and the inner cylinder It is configured to move to the space, melt the exposed surface by the combustion flame of the combustor, and drop and discharge the molten slag from the outlet, and phosphorus-containing sludge or phosphorus-containing incineration charged into the accumulation unit It is in the point provided with the addition mechanism which adds the skeleton adjusting agent to ash.

  With the addition mechanism provided in the melting furnace, an appropriate amount of skeletal conditioner can be added to the phosphorus-containing sludge or phosphorus-containing incinerated ash charged in the accumulator immediately before the melting treatment and stirred by rotation of the outer cylinder. It is not necessary to provide an additional stirring mechanism separate from the furnace.

  As described above, according to the present invention, a fertilizer manufacturing method that can adjust the dissolution rate of phosphorus contained in the manufactured fertilizer without mixing other phosphorus raw materials into the sludge that is the fertilizer raw material. And a rotary surface melting furnace used in a method for producing a fertilizer can be provided.

Block diagram of fertilizer manufacturing equipment Illustration of fertilizer manufacturing method It is explanatory drawing of the rotary surface melting furnace by this invention, Comprising: (a) is explanatory drawing which shows the structure of each part, (b) Explanatory drawing when an inner cylinder moves upwards (A) is explanatory drawing of the composition of a base sample and a comparative sample, (b) is explanatory drawing of a sample. Chart showing the main composition of each sample Chart showing optical basicity of each sample Chart showing elution concentration and eluate pH of each element in dissolution test Chart showing elution ratio of each element in dissolution test Chart showing the relationship between optical basicity and elution ratio of each element (A) is explanatory drawing of each sample, (b) is explanatory drawing of the experimental condition of each sample. Chart showing optical basicity and phosphorus dissolution rate in dissolution test Chart showing elution ratio of each element in dissolution test Chart showing elution ratio of each element in dissolution test Chart showing elution ratio of each element in dissolution test

Hereinafter, embodiments will be described.
FIG. 1 shows a fertilizer manufacturing plant 10 in which the fertilizer manufacturing method according to the present invention is executed, that is, a fertilizer manufacturing plant 10 using phosphorus-containing sludge or phosphorus-containing incinerated ash as a raw material.

  The manufacturing plant 10 includes a water treatment mechanism 11 for biologically treating sewage sludge flowing into the biological treatment tank from the outside using an activated sludge method, a membrane separation activated sludge method, and the like, and a pump P from the water treatment mechanism 11. From the dehydration mechanism 12 for dewatering the excess sludge extracted, the drying mechanism 13 for drying the dewatered sludge dehydrated by the dehydration mechanism 12, the melting mechanism 14 for melting the dried sludge dried by the drying mechanism 13, and the melting mechanism 14. A cooling mechanism 15 that cools the molten slag that flows out, and a sizing mechanism 17 that regulates the slag obtained by the cooling mechanism 15 and conveyed by the conveyor mechanism 16 to a preferable particle size as a fertilizer are provided.

  In the biological treatment tank provided in the water treatment mechanism 11, organic substances in the sewage are decomposed and removed by activated sludge and purified. In the process of aerobic treatment of sewage in the biological treatment tank, phosphorus in the sewage is taken into the activated sludge, and the phosphorus-containing sludge that has taken in the phosphorus from the biological treatment tank or the sedimentation tank placed at the subsequent stage of the biological treatment tank It is pulled out and conveyed to the dehydrating mechanism 12.

  By adding an iron-based flocculant to a sedimentation tank or the like and precipitating the phosphorus component contained in the sewage, the concentration of the phosphorus component contained in the sludge extracted from the water treatment mechanism 11 can be increased.

  The sludge is dehydrated to a water content of about 80% by a screw press type dewatering device provided in the dewatering mechanism 12, the water content is dried to about 20 to 40% by the subsequent drying mechanism 13, and then transported to the melting mechanism 14. The

  In addition to the screw press type dehydrator, any dehydrator such as a rotary press type, a filter press type, a centrifugal separation type, or a belt press type can be adopted as the dehydrating unit.

  The drying mechanism 13 is a screw-type transport that transports the dewatered sludge input from the sludge input section provided on the upstream side of the main casing while stirring the main casing toward the sludge discharge section provided on the downstream side of the main casing. It has a mechanism. By supplying steam or high-temperature air generated using the retained heat of the exhaust gas from the melting mechanism 14 as a heat source to the shaft cavity provided in the screw-type transport mechanism, the dewatered sludge being transported in the main body casing is indirectly heated. And dried.

  The sludge melted by the melting mechanism 14 to become slag is cooled and solidified by the subsequent cooling mechanism 15 and further conveyed to the particle size adjusting mechanism 17 by the belt type conveying mechanism 16 to be adjusted to a desired particle size.

  That is, as shown in FIG. 2, in the manufacturing plant 10, a water treatment step (SA 1) for purifying sewage sludge by the water treatment mechanism 11, and surplus sludge generated in the water treatment step is drawn and dewatered by the dewatering mechanism 12. A dehydrating step (SA2), a drying step (SA3) for drying the dehydrated cake with the drying mechanism 13, a melting processing step (SA4) for melting the dried sludge with the melting mechanism 14, and a cooling mechanism for the slag melted in the melting processing step The fertilizer manufacturing method includes a cooling process step (SA5) in which the slag is cooled and solidified in 15 and a slag solidified in the cooling process step is pulverized by the sizing mechanism 17 to adjust the particle size (SA6). Is done. Moreover, depending on the fertilizer, other fertilizer raw materials may be mixed after the sizing step to obtain a fertilizer.

  In addition, although this embodiment mainly demonstrates the method of melt | dissolving phosphorus containing sludge and manufacturing a fertilizer, after dehydrating sewage sludge, the phosphorus containing incinerated ash obtained by incineration with an incinerator is used with the melting mechanism 14. It is applicable also to the method of manufacturing a fertilizer by melt-processing.

  In the fertilizer manufacturing method, a skeletal phosphate is added to the total phosphorus weight contained in the slag solidified in the cooling treatment step by adding a skeletal conditioner to the phosphorus-containing sludge or phosphorus-containing incinerated ash before the melting treatment step. A skeletal regulator addition step for adjusting the weight ratio to exceed a predetermined value is provided.

Silica, which is the main component of the slag skeleton melted in the melting step and solidified in the cooling step, is a three-dimensional structure in which the SiO ₄ tetrahedron is irregularly arranged with oxygen O as a bridge in the actual structure. It is connected by the mesh. That is, four oxygen SiO _4, while making the SiO ₄ tetrahedra surrounds the orbits of the four vertices of silicon Si make, oxygen O is infinite network structure bonded with other another silicon Si is made . Such oxygen O that connects silicon Si is called bridging oxygen. Similarly, the phosphoric acid P ₂ O ₅ contained in the slag is bonded with phosphorus P to bridging oxygen to form an infinite network structure. When a cation such as a metal ion is contained in such a slag component, a part of the oxygen O to be bonded to silicon Si or phosphorus P is cut and is in an ionic balance with the cation. become. Such oxygen O is called non-bridging oxygen. When non-bridging oxygen increases in the slag, the slag skeleton strength becomes weak and easily collapses. Conversely, when non-bridging oxygen decreases in the slag, the slag skeleton strength increases.

  When the number of non-bridging oxygen in the slag increases with respect to the slag mainly composed of a network structure by bridging oxygen, the solubility of phosphoric acid, which is a fertilizer component, increases.

  Therefore, by adding a skeletal modifier to the phosphorus-containing sludge or phosphorus-containing incinerated ash before the melting treatment step, it becomes possible to adjust the number of non-crosslinked oxygen in the slag, and the amount of skeleton modifier added can be reduced. By adjusting, it becomes possible to adjust so that the ratio of the soluble phosphorus weight with respect to the total phosphorus weight contained in the slag solidified in the cooling step exceeds a predetermined value. Conceptually, the ratio of the soluble phosphorus weight to the total phosphorus weight contained in the slag solidified in the cooling step is adjusted to a desired ratio by adjusting the amount of the skeletal modifier added. Can do.

  In the skeletal modifier addition step, the optical basicity of the slag solidified in the cooling treatment step is adjusted so that the ratio of the soluble phosphorus weight to the total phosphorus weight contained in the slag solidified in the cooling treatment step exceeds a predetermined value. Preferably, the step of adjusting.

  As an index for evaluating the skeletal strength of slag, optical basicity can be used as an index. Optical basicity is an index found by Duffy and Ingram, focusing on the fact that the ultraviolet light absorption peak changes sensitively with respect to the glass composition. Is an index that is derived from the electronegativity of the cation constituting s based on the following formula.

Optical basicity Λ = 1−Σ (zi · ri / 2) · (1-1 / γi)
However, γi = 1.36 (χi−0.26)
Here, zi is the valence of the i-type cation, ri is the number of the i-type cation expressed per oxygen, and χi is the electronegativity of the i-type cation.

  The optical basicity is a value obtained by analyzing the composition of phosphorus-containing sludge or phosphorus-containing incinerated ash in advance, so that the ratio of the soluble phosphorus weight to the total phosphorus weight contained in the slag exceeds the predetermined value. If the optical basicity for realizing the strength is determined, the amount of the skeleton adjusting agent for obtaining such optical basicity can be adjusted in advance. According to the experiment, by adjusting the optical basicity to 0.57 or more, the dissolution rate of phosphorus, that is, the ratio of the soluble phosphorus weight to the total phosphorus weight contained in the slag can be effectively increased. It has been found that the same or better than commercially available slow-release fertilizers can be produced.

  The optical component of the slag solidified in the cooling treatment step so that the ratio of the soluble phosphorus weight to the total phosphorus weight contained in the fertilizer containing the slag solidified in the cooling treatment step exceeds the predetermined value in the skeletal conditioner addition step. It may be a step of adjusting the basicity. In some cases, other fertilizers may be mixed with the slag, and in that case, the ratio of the soluble phosphorus weight to the total phosphorus weight as the whole mixed fertilizer needs to be adjusted. Even in such a case, if the phosphorus dissolution rate of other fertilizers is known, the phosphorus dissolution rate of the entire mixed fertilizer is adjusted by adjusting the addition amount of the skeleton regulator. Will be able to.

  The skeletal modifier added in the skeletal modifier adding step is preferably one or more kinds of simple metals or metal compounds selected from alkali metals, alkaline earth metals, or transition metals. Sodium, potassium, calcium More preferably, it is one or more kinds of simple metals or metal compounds selected from magnesium, iron, manganese, copper, and zinc.

  When using one or more kinds of simple metals or metal compounds selected from potassium, calcium, magnesium, iron, manganese, copper, and zinc as skeletal modifiers to weaken slag and promote phosphorus elution, they themselves Becomes an indispensable fertilizer component for plants, and a fertilizer of better quality with multiple fertilizer components can be obtained.

  As shown in FIG. 2, when the skeletal regulator to be added is a calcium or iron-based water-insoluble metal compound or the like, the skeletal regulator addition step is performed on the raw water before biological treatment. If it is (SA71), the skeleton adjusting agent is dispersed by the water treatment mechanism 11 and can be uniformly dispersed in the sludge.

  When the skeletal regulator to be added is a water-soluble metal compound such as sodium or potassium, the skeletal regulator is drawn out from the biological treatment tank etc. so that the skeleton regulator dissolves in water and is not drained, and immediately before being dehydrated. The skeletal modifier addition step may be executed on the sludge (SA72), and the skeleton modifier addition step may be executed in any step up to the melt treatment step (SA73). Of course, a calcium or iron-based water-insoluble metal compound may be added to the sludge at any stage between step SA72 and step SA73. In this way, the skeleton modifier can be uniformly dispersed in the sludge by changing the input location of the skeleton modifier.

It should be noted that only one of the above-described skeleton modifier addition steps (SA71, SA72, SA73) may be executed or may be executed in combination.

  For example, if sodium, potassium, calcium, or iron metal alone or a metal compound is used as a skeletal modifier, the melting point of sludge can be lowered in the melting step, and external energy such as fossil fuel and electric power for melting. Consumption can be reduced.

  When melt processing is performed at a temperature higher than 1300 ° C., the viscosity of the slag is low, the slag skeleton approaches an energy-stable equilibrium state, and the slag has a strong skeleton strength. Since the slag skeleton does not reach an equilibrium state, it is possible to obtain a slag having a low skeleton strength. In addition, the melting temperature itself can be lowered by adding sodium, potassium, calcium, and iron metal simple substance or metal compound, so that the melting energy of fossil fuel and the like can be saved.

  Furthermore, it is possible to combine the two effects of weakening the skeleton strength by the skeleton modifier and weakening the slag by setting the melting temperature to 1300 ° C. or less. be able to.

  In the melting step, dioxins, which are harmful substances contained in sludge, are thermally decomposed and heavy metals with low boiling point such as mercury are evaporated, and heavy metals with high boiling point such as copper are trapped in slag and made harmless. Is done. Therefore, the safety of the fertilizer using slag is maintained.

  Further, when an iron metal simple substance or a metal compound is used, it can be alloyed with phosphorus to raise its boiling point, and the phosphorus component can be effectively prevented from vaporizing during the melting treatment. That is, the phosphorus content in the slag can be increased.

If iron or a compound thereof is used as a skeletal modifier added in the skeletal modifier addition step and the melting treatment step is performed in a reducing atmosphere, iron becomes FeO in the slag, and the skeleton strength can be weakened. . Conversely, when the melt treatment step is performed in an oxidizing atmosphere, iron becomes Fe ₂ O _{3 in} the slag, and the amount of cross-linking oxygen increases, resulting in a slag with strong skeleton strength. That is, the dissolution rate of phosphorus contained in the slag can be adjusted depending on whether the atmosphere during melting is a reducing atmosphere or an oxidizing atmosphere.

  When the molten slag is cooled in the cooling process step, if the molten slag is rapidly cooled, such as by dropping it into a water tank, amorphous slag is obtained and phosphorus is incorporated into the amorphous skeleton, so the phosphorus elution rate Low slag. When the molten slag is slowly cooled by air cooling or the like, a slag mainly composed of a crystal is obtained, and phosphorus is difficult to be taken into the crystalline skeleton, so that a slag having a high phosphorus elution rate is obtained.

  Regardless of the cooling method, there is an effect of weakening the skeleton strength by adding the skeleton adjusting agent. That is, slag with a higher phosphorus elution rate can be obtained by slow cooling.

  Although slow cooling is preferable from the viewpoint of increasing phosphorus solubility, a mechanism for that purpose, that is, a complex mechanism for slow cooling such as an air cooling mechanism is required. In this respect, when the molten slag is rapidly cooled by dropping it into a water tank to obtain a granulated slag, there are advantages that the cooling mechanism can be simplified and that the production amount per unit time can be earned.

  As described above, the fertilizer having the skeletal conditioner addition step for adjusting the ratio of the soluble phosphorus weight to the total phosphorus weight contained in the slag solidified in the cooling treatment step to be higher than a predetermined value before the melting treatment step. Although the invention in terms of the manufacturing method has been described, the present invention relates to the ratio of the soluble phosphorus weight to the total phosphorus weight contained in the slag solidified in the cooling treatment step between the melt treatment step and the cooling treatment step. It is also an invention from the viewpoint of a method for producing a fertilizer provided with a soluble phosphorus adjusting treatment step for adjusting.

  Also in this case, since the ratio of the slag soluble phosphorus weight to the total phosphorus weight contained in the slag can be adjusted by the slag soluble phosphorus adjustment processing step, not only when fertilizing the slag alone as a fertilizer, but also with other fertilizers. Even when fertilized as a mixed mixed fertilizer, the ratio of the soluble phosphorus weight to the total phosphorus weight contained in the slag solidified in the cooling step can be adjusted.

  The soluble phosphorus adjusting treatment step is preferably a skeleton adjusting agent adding step for adding a skeleton adjusting agent to the melt containing phosphorus-containing sludge or phosphorus-containing incinerated ash, before the melting treatment step. As already explained, when the number of non-bridging oxygen in the slag increases with respect to the slag mainly composed of a network structure with bridging oxygen, the solubility of phosphoric acid, which is a fertilizer component, increases. And it becomes possible to adjust the number of non-bridging oxygen in the slag by providing a skeletal modifier addition step of adding a skeleton modifier to phosphorus-containing sludge or phosphorus-containing incinerated ash in the previous stage of the melting treatment step, By adjusting the addition amount of the skeleton adjusting agent, the ratio of the soluble phosphorus weight to the total phosphorus weight contained in the slag solidified in the cooling treatment step can be adjusted.

  That is, the slag phosphorus dissolution rate as a fertilizer can be adjusted to the desired dissolution rate, so even when manufacturing fertilizers mixed with other fertilizers, the slag dissolution rate is adjusted as a whole fertilizer. It becomes possible to produce a slag that can be made.

  Moreover, it is preferable that a frame | skeleton adjusting agent addition step is a step which adjusts the optical basicity of the slag solidified at the said cooling process step by adding a frame | skeleton adjusting agent to phosphorus containing sludge or phosphorus containing incinerated ash.

  As already explained, since the optical basicity is a value obtained by analyzing the composition of phosphorus-containing sludge or phosphorus-containing incinerated ash in advance, the ratio of the soluble phosphorus weight to the total phosphorus weight contained in the slag is predetermined. If the optical basicity for realizing such a skeleton strength is determined, the addition amount of the skeleton adjusting agent for obtaining such optical basicity can be adjusted in advance.

  The skeleton modifier added in the skeleton modifier addition step is preferably one or more kinds of simple metals or metal compounds selected from alkali metals, alkaline earth metals, or transition metals, particularly sodium, potassium, One or more kinds of simple metals or metal compounds selected from calcium, magnesium, iron, manganese, copper, and zinc are preferable.

  When one or more kinds of simple metals or metal compounds selected from potassium, calcium, magnesium, iron, manganese, copper, and zinc are used as a skeletal modifier for controlling phosphorus elution from slag, they themselves It becomes an essential fertilizer component for plants, and a fertilizer with better quality including multiple fertilizer components can be obtained.

  For example, if sodium, potassium, calcium, or iron metal alone or a metal compound is used as a skeletal modifier, the melting point of sludge can be lowered in the melting step, and external energy such as fossil fuel and electric power for melting. Consumption can be reduced. Further, when an iron metal simple substance or a metal compound is used, it can be alloyed with phosphorus to raise its boiling point, and the phosphorus component can be effectively prevented from vaporizing during the melting treatment.

  It is preferable that the skeleton adjusting agent added in the skeleton adjusting agent adding step includes iron or a compound thereof, and the melting treatment step is performed in either a reducing atmosphere or an oxidizing atmosphere.

When the framework modifier added in the framework modifier adding step contains iron or a compound thereof, the iron in the molten slag is in the form of Fe ₂ O ₃ when the melting treatment step is performed in an oxidizing atmosphere. Therefore, a slag having a high skeleton strength can be obtained. When the melting treatment step is performed in a reducing atmosphere, iron in the molten slag becomes a form of FeO, and a slag having a low skeleton strength can be obtained.

  In the melting treatment step, when the slag is melted at a temperature higher than 1300 ° C., the viscosity of the slag is low, the slag skeleton approaches an energy stable equilibrium state, and a slag having a high skeleton strength can be obtained. When the melting treatment is performed at a melting temperature of slag, since the viscosity of the slag is high and the slag skeleton does not reach an equilibrium state, a slag having a low skeleton strength can be obtained.

  Furthermore, the cooling process step preferably includes a step of slowly cooling and solidifying the slag melted in the melting process step using an air cooling mechanism or a heat retaining mechanism, or a step of rapidly cooling using a water cooling mechanism.

  When the molten slag is cooled in the cooling step, if the molten slag is cooled slowly and solidified using an air cooling mechanism or a heat retaining mechanism, a crystalline-based slag is obtained, and phosphorus is not easily incorporated into the crystalline skeleton. It becomes slag with high phosphorus elution rate. In addition, when the water cooling mechanism is used for rapid cooling, amorphous slag is obtained, and since phosphorus is incorporated into the amorphous skeleton, the slag has a low phosphorus elution rate.

  The adjustment of the slag temperature and the change of the cooling treatment method can be performed in accordance with the adjustment of the addition amount of the skeleton adjusting agent, and the adjustment of the phosphorus dissolution rate can be achieved more widely.

  In this way, by adding a skeletal modifier to the phosphorus-containing sludge and melting it, the skeletal structure of the slag is weakened and the ratio of the soluble phosphorus weight to the total phosphorus weight contained in the slag solidified in the cooling treatment step Can be adjusted to a desired value, so that it is possible to produce a fertilizer with high added value in which the fertilizer effect suitable for the purpose is adjusted.

  In the skeletal modifier addition step, the optical basicity Λ of the slag solidified in the cooling treatment step is set so that the ratio of the soluble phosphorus weight to the total phosphorus weight contained in the slag solidified in the cooling treatment step exceeds a predetermined value. Adjust. There is a positive correlation between the optical basicity and the phosphorus elution ratio from the fertilizer. By adding a skeletal modifier so that the optical basicity Λ is generally less than 0.57, the skeleton has a strong fertilizer effect. By adding a skeletal modifier so that the low slag has an optical basicity Λ of 0.57 or more, a slag having a weak skeleton and a high fertilizer effect can be produced.

  As the melting mechanism 14 used in the fertilizer manufacturing method according to the present invention, a rotary surface melting furnace or an electric furnace can be used. The rotary surface melting furnace will be described below.

  As shown in FIGS. 3 (a) and 3 (b), the rotary surface melting furnace 20 includes an inner cylinder 23 erected around the ceiling portion 22 where the combustor 21 is disposed, and an outlet at the center of the bottom portion. And a bottomed outer cylinder 25 formed with a base 24 is arranged around a common axis, and includes a rotation mechanism that rotates the outer cylinder 25 around the axis, and the outer cylinder 25 is configured to be rotatable with respect to the inner cylinder 23. Has been.

  The combustor 21 is composed of a burner that mixes and burns fuel supplied from a fuel tank and air supplied from a blower. The temperature of the molten slag is adjusted to 1000 ° C. to 1700 ° C. by adjusting the amount of fuel supplied. The temperature in the main combustion chamber 26 is adjusted so as to be in the range, and the atmosphere in the main combustion chamber 26 is adjusted to be a reducing atmosphere or an oxidizing atmosphere by adjusting the supply amount of air.

  The dried sludge charged into the hopper is quantitatively charged into the accumulating portion 27 formed between the inner cylinder 23 and the outer cylinder 25, and the ceiling from the lower edge of the inner cylinder 23 by the relative rotation of the inner cylinder 23 and the outer cylinder 25. It is supplied to the main combustion chamber 26 in the lower space of the section 22. The exposed surface of the sludge is melted by the combustion flame of the combustor 21 and is dropped and discharged as molten slag from the tap outlet 24 formed at the center of the bottom surface of the main combustion chamber 26. The molten slag that has fallen from the tap outlet 24 is rapidly cooled in a water tank as a cooling and solidifying mechanism 15 disposed below to become a granulated slag.

  The exhaust gas discharged from the flue 28 branching laterally from the tap outlet 24 is discharged from the chimney after being treated by the exhaust gas treatment facility. As an exhaust gas treatment facility, a post-combustion device that completely combusts exhaust gas discharged from the furnace, an air preheater that preheats combustion air supplied to the combustor 21 and the post-combustion device with the retained heat of the exhaust gas after post-combustion, and drying A waste heat boiler for generating steam for drying to the mechanism 13, an air heater for heating white smoke prevention air, a temperature reducing tower, an exhaust gas purification device, a bag filter, an induction fan, and the like are arranged along the flue. .

  In order to adjust the distance between the lower edge of the inner cylinder 23 and the bottom of the outer cylinder 25, a gear type or crane type that raises and lowers the inner cylinder 23 and the ceiling portion 22 integrally with the outer cylinder 25 in the vertical direction. An interval adjusting mechanism including an elevating mechanism is provided.

  As shown in FIG. 3A, when the inner cylinder 23 is lowered, the interval between the lower edge of the inner cylinder 23 and the bottom of the outer cylinder 25 is narrow, and the sludge introduced from the accumulator 27 to the main combustion chamber 26 is reduced. Since the amount is reduced, the time for the molten slag to flow down from the surface to the outlet 24 becomes longer, and a sufficient residence time of the slag can be secured.

  As shown in FIG. 3B, when the inner cylinder 23 is raised, the interval between the lower edge of the inner cylinder 23 and the bottom of the outer cylinder 25 is widened, and the sludge guided from the accumulation section 27 to the main combustion chamber 26. Therefore, the slag melted from the surface immediately flows down to the spout 24 and the slag residence time is shortened.

  In other words, the residence time adjusting mechanism that adjusts the residence time of the slag melted in the main combustion chamber 26 moves the inner cylinder 23 and the outer cylinder 25 relative to each other in the common axial direction so that the lower edge of the inner cylinder 23 and the outer This is realized by an interval adjusting mechanism that adjusts an interval between the bottom of the tube 25.

  In addition to the above-described interval adjusting mechanism, a dwell is provided around the spout 24 and an adjusting mechanism for adjusting the height of the weir is provided to variably adjust the residence time of the molten slag in the main combustion chamber. May be.

  In addition to the dry sludge hopper, a single or a plurality of hoppers containing a skeletal conditioner for addition to the sludge are installed on the upper portion of the doughnut-shaped accumulating portion 27 in plan view, and are provided at the bottom of the hopper The added amount of the skeleton adjusting agent is adjusted by the cut-out mechanism. That is, the addition mechanism is constituted by the hopper for the skeleton adjusting agent and the cutting mechanism.

  Thus, the rotary surface melting furnace is a melting furnace suitable for the production of fertilizer because it is easy to adjust the oxygen concentration in the furnace, to adjust the residence time of the slag, and to input and agitate the skeletal regulator.

  In any of the above-described embodiments, the configuration in which the phosphorus-containing sludge fed from the drying mechanism 13 is input to the melting mechanism 14 has been described. However, instead of the drying mechanism 13, combustion for burning dehydrated sludge A furnace may be provided to perform the dewatered sludge combustion step, and the obtained phosphorus-containing incinerated ash may be conveyed to the melting mechanism 13 and melted.

  Each of the above-described embodiments is an example of the present invention, and the present invention is not limited by the description, and the specific configuration of each part such as material and size is within the range where the effects of the present invention are exhibited. Needless to say, the design can be changed as appropriate.

A first experimental example showing the correlation between optical basicity and slag skeleton structure will be described below.
As described above, the elution behavior of various elements from the molten slag is governed by the slag skeleton structure. If it is close to the ideal SiO ₂ tetrahedral structure, the skeleton structure is strong and the elution concentration of various elements is low, but if there are many components such as CaO, Na ₂ O, K ₂ O and the proportion of defect structure parts is high, the skeleton structure is weak. The elution concentration of fertilizer components such as P and Ca increases.

Therefore, by adding sodium carbonate Na ₂ CO ₃ or calcium carbonate CaCO ₃ as a skeleton adjusting agent to the base sample slag and remelting it, a sample slag with low slag skeleton strength is produced, and phosphorus elution is caused by a decrease in skeleton strength. Compared to confirm that is promoted.

  FIG. 4A shows the composition of the sewage sludge molten slag that is the base sample of the test. The sewage sludge molten slag tends to have lower CaO concentration and heavy metal concentration and higher iron and phosphorus concentrations than the municipal waste molten slag shown in the lower part of the table.

As shown in the table of FIG. 4 (b), the base sample alone is sample 1, the base sample and Na ₂ CO ₃ mixed at a ratio of 8: 2 is sample 2, and the base sample and CaCO ₃ are mixed. The following experiment was conducted using Sample 3 mixed at a ratio of 8: 2.

  Samples 1 to 3 were filled in a graphite crucible of φ80 mm × H100 mm with a thickness of about 8 cm (weight: about 250 g) and held for 1 h in an electric muffle furnace adjusted to a temperature of 1400 ° C. to prepare a slag. During the heating, the gas atmosphere in the electric furnace was not adjusted. Thereafter, the graphite crucible was removed from the electric furnace, and the slag was rapidly cooled in room temperature air while being placed in the graphite crucible.

  The dissolution test was carried out by an operation according to the Environmental Agency Notification Method No. 46 (slag: distilled water = 1: 10, stirring for 6 hours). In order to remove the influence of the physical shape of the sample, the slag was crushed to 1-2 mm, and the slag having a 1-2 mm shape was used.

FIG. 5 shows the main compositions of Samples 1 to 3 after the heating test. Since Na ₂ CO ₃ added to the sample 2 and CaCO ₃ added to the sample 3 undergo thermal decomposition during heating to release CO _2, they are taken into the molten slag as Na ₂ O and CaO. Therefore, the increasing concentrations of Na ₂ O and CaO in the slag by adding 20% of Na ₂ CO ₃ and CaCO ₃ are 11.7% and 11.2%, respectively. It was confirmed that Na ₂ O in Sample 2 and CaO in Sample 3 were about 10% higher than Sample 1 with only the base sample, and the composition was as expected.

FIG. 6 shows the optical basicity of each sample as an index representing the skeleton strength. The photochemical basicity can be obtained from the mathematical formula already described. As in Samples 2 and 3, by adding Na ₂ CO ₃ and CaCO ₃ , the optical basicity increases and the skeletal strength of the slag decreases. The order is the order of Sample 2> Sample 3> Sample 1. Monovalent Na ions added to Sample 2 have a higher degree of lowering the skeleton strength than divalent Ca ions added to Sample 3.

  FIG. 7 shows the phosphorus (P) elution concentration from each sample in the elution test. At the same time, the elution concentrations of the main constituent element (Si) of slag and the main essential elements for plant growth were also investigated. In addition, the main composition element (Si) of slag is an element having an effect of improving resistance to rice diseases and lodging resistance as silicic acid.

The elution concentration of phosphorus (P) was higher in the elution concentrations of sample 2 and sample 3 to which Na ₂ CO ₃ and CaCO ₃ were added than in sample 1 having only the base sample. The same tendency was observed for main elements such as Si, Ca, Fe, Mg, and S. Contrary to K, Samples 2 and 3 were lower, and Zn, Cl, Mo, B, and Mo were less than the lower limit of quantification.

FIG. 8 shows the elution ratio of each element in the elution test. The dissolution rate was calculated from the composition analysis results and dissolution test results according to the following mathematical formula. As a result, the sample 2 and sample 3 to which Na ₂ CO ₃ and CaCO ₃ were added were also compared for the elution rate for phosphorus (P), Si, Ca, Fe, Mg, and S as compared to the sample 1 without addition. Was higher.

  Elution ratio (mg / kg) = (Amount of eluted metal (mg) / Amount of metal contained (mg)) × 1000000

  FIG. 9 shows the relationship between optical basicity and elution ratio. For phosphorus (P), Si, Ca, and Fe whose elution ratio increased by the addition of the skeleton modifier, a positive correlation was observed between the optical basicity and the elution ratio. Therefore, by controlling the optical basicity of the slag, it is possible to intentionally increase the release amount (elution amount) of several fertilizer components (P, Si, Ca, Fe) including phosphorus. Indicated.

  As described above, using the sewage sludge melted slag as a base sample, the phosphorus elution concentration was investigated with the slag whose slag skeleton strength was changed by adding each reagent, and the following results were obtained.

By adding Na ₂ CO ₃ and CaCO ₃ , the optical basicity of the slag increases (the slag's skeleton strength decreases), and the order is the sample 2 to which Na ₂ CO ₃ is added> the sample to which CaCO ₃ is added 3. Sample 1 with only base sample.

  There was a positive correlation between optical basicity and phosphorus elution rate, therefore intentionally increasing the amount of phosphorus released (elution amount) by controlling the optical basicity of the slag It was shown that

  Next, a second experimental example regarding the influence of the skeletal modifier on the soluble phosphorus will be described.

  The composition of the sewage sludge molten slag and the municipal waste molten slag, which are the base samples for the test, is the same as the table shown in FIG.

As shown in the table of FIG. 10 (a), the following experiment was conducted with the base sample alone as sample 4 and the base sample mixed with Na ₂ CO ₃ at a ratio of 8: 2 as sample 5.

  Samples 4 and 5 were filled in a graphite crucible of φ80 mm × H100 mm with a thickness of about 8 cm (weight: about 250 g) and held for 1 h in an electric muffle furnace adjusted to 1400 ° C. to prepare a slag. During the heating, the gas atmosphere in the electric furnace was not adjusted. Thereafter, the graphite crucible was removed from the electric furnace, and the slag was rapidly cooled in room temperature air while being placed in the graphite crucible. The obtained slag was subjected to a soluble phosphorus elution test, and the dissolution behavior of the soluble phosphorus was compared.

  In order to remove the influence of the physical shape of the sample, the slag-soluble phosphorus elution test was performed by crushing the slag to 1-2 mm and using a 1-2 mm-shaped slag. The soluble phosphorus elution test is an elution test in an aqueous acid solution (pH 2 to 3) using citric acid as a solvent. Since plant roots release citric acid, fertilizer at a stage where plant growth has progressed to some extent. It is used as an index indicating the effect (slow effect).

  FIG. 11 shows the relationship between the phosphorus elution ratio and the optical basicity in the soluble phosphorus elution test. The soluble elution ratio was calculated from the composition analysis result and the dissolution test result according to the following formula.

  Soluble elution ratio (%) = (eluted metal amount (mg) / contained metal amount (mg)) × 100

  As a result, a positive correlation was found between the optical basicity and the soluble phosphorus elution ratio.Therefore, by controlling the optical basicity of the slag (weakening of the slag skeleton), It was shown that the release amount (elution amount) of phosphorus can be intentionally increased.

  Next, a third experimental example relating to the influence of slag melting time and melting temperature will be described.

  The composition of the sewage sludge molten slag as the base sample for the test is the same as the table shown in FIG.

As shown in the table of FIG. 10 (b), _three samples, sample 6, sample 6 and sample 7, prepared by mixing the base sample and Na ₂ CO ₃ at a ratio of 8: 2, are prepared in FIG. 10 (b). As shown, the experiment was conducted under different melting conditions.

  Sample 5 was filled in a graphite crucible of φ80 mm × H100 mm with a thickness of about 8 cm (weight: about 250 g) and held in an electric muffle furnace adjusted to a temperature of 1400 ° C. for 1 h to prepare a slag.

  Sample 6 was filled in a graphite crucible of φ80 mm × H100 mm with a thickness of about 8 cm (weight: about 250 g), and held in an electric muffle furnace adjusted to a temperature of 1400 ° C. for 4 hours to prepare a slag.

  Sample 7 was filled in a graphite crucible of φ80 mm × H100 mm with a thickness of about 8 cm (weight: about 250 g) and held in an electric muffle furnace adjusted to 1250 ° C. for 1 h to prepare a slag.

  During the heating of any of Samples 5 to 7, the gas atmosphere in the electric furnace was not adjusted. Thereafter, the graphite crucible was removed from the electric furnace, and the slag was rapidly cooled in room temperature air while being placed in the graphite crucible.

  First, in order to investigate the change in the dissolution rate of phosphorus due to the melting time when slag was melted, a dissolution test and a soluble phosphorus dissolution test were conducted on Sample 5 and Sample 6 by the operation of the Environment Agency Notification No. 46. In order to remove the influence of the physical shape of the sample, the slag was crushed to 1-2 mm, and the slag having a 1-2 mm shape was used. The soluble phosphorus elution test is an elution test in an aqueous acid solution (pH 2 to 3) using citric acid as a solvent. Since plant roots release citric acid, fertilizer at a stage where plant growth has progressed to some extent. It is used as an index indicating the effect (slow effect). Compared with the dissolution test by the Environment Agency Notification No. 46 method, which is a dissolution test in neutral to weakly alkaline aqueous solution, it is a dissolution test in a harsh atmosphere, and the dissolution level is high. To do.

  As shown in FIGS. 13 and 14, in both the dissolution test by the Environment Agency Notification No. 46 method operation and the soluble phosphorus dissolution test, the dissolution rate of sample 6 for all the elements containing phosphorus decreased compared to sample 5. . Even if the skeleton composition is the same, it is considered that by extending the melting time, the skeleton structure approaches an energy stable equilibrium state, and the slag skeleton is strengthened.

  Next, in order to investigate the change in the dissolution rate of phosphorus depending on the melting temperature at the time of slag melting, a dissolution test was conducted on Sample 5 and Sample 7 by the operation of the Environment Agency Notification No. 46.

  As shown in FIG. 14, Sample 7 resulted in an exponentially increasing elution ratio for many elements including phosphorus, compared to Sample 5. When the melting temperature is low, the viscosity of the molten slag is low, and it takes time to reach an equilibrium state. Therefore, it is considered that the elution rate has increased.

10: Fertilizer production plant 11: Water treatment mechanism 12: Dehydration mechanism 13: Drying mechanism 14: Melting mechanism 15: Cooling mechanism 16: Conveyor mechanism 17: Granulating mechanism 20: Rotary surface melting furnace 21: Combustor 22: Ceiling Part 23: Inner cylinder 24: Outlet 25: Outer cylinder 26: Main combustion chamber 27: Accumulator 28: Flue

Claims (17)

A method for producing a fertilizer, comprising: a melting treatment step for melting a melt containing phosphorus-containing sludge or phosphorus-containing incinerated ash; and a cooling treatment step for cooling and solidifying the slag melted in the melting treatment step. There,
An addition amount of a skeleton adjusting agent obtained by using optical basicity as an index for evaluating slag is added to the melt, and soluble phosphorus with respect to the total phosphorus weight contained in the slag solidified in the cooling treatment step. skeletal modifier added step of the ratio of the weight is adjusted to exceed the predetermined value, producing how fertilizers are provided in a stage preceding the melt-processing step. The amount of the skeletal modifier added in the skeleton modifier adding step is such that the optical basicity of the slag solidified in the cooling treatment step is the ratio of the soluble phosphorus weight to the total phosphorus weight contained in the slag. The method for producing a fertilizer according to claim 1, wherein the fertilizer is a value adjusted based on optical basicity obtained by analyzing the composition of the melt beforehand so as to exceed a predetermined value . The amount of the skeletal modifier added in the skeletal modifier addition step is such that the slag optical basicity solidified in the cooling treatment step is the soluble phosphorus weight relative to the total phosphorus weight contained in the fertilizer containing the slag. The method for producing a fertilizer according to claim 1, wherein the fertilizer is a value adjusted based on optical basicity obtained by analyzing the composition of the melt beforehand so that the ratio exceeds a predetermined value . The manufacturing method of the fertilizer in any one of Claim 1 to 3 with which the said frame | skeleton adjustment agent addition step is performed before a fusion | melting process step. The phosphorus-containing sludge is surplus sludge generated in a water treatment step of biologically treating raw water to purify the raw water, and the skeletal modifier addition step is performed on the surplus sludge extracted in the water treatment step. The manufacturing method of the fertilizer of description. The phosphorus-containing sludge is surplus sludge generated in a water treatment step for biologically treating and purifying raw water, and the skeletal regulator addition step is performed on raw water before being biologically treated in the water treatment step. Item 5. A method for producing a fertilizer according to Item 4. The method for producing a fertilizer according to claim 6, wherein the skeleton adjusting agent used in the skeleton adjusting agent adding step is a water-insoluble skeleton adjusting agent. The manufacturing method of the fertilizer in any one of Claim 1 to 3 with which the said frame | skeleton adjustment agent addition step is performed with respect to the said phosphorus containing sludge or the said phosphorus containing incinerated ash. Skeletal modifier to be added in the previous SL backbone modifier addition step, an alkali metal, one of claims 1 to 8 of an alkaline earth metal or one kind or more kinds of single metal or metal compound selected from transition metals, The manufacturing method of the fertilizer of crab. The skeleton modifier added in the skeleton modifier adding step is one or more kinds of simple metals or metal compounds selected from sodium, potassium, calcium, magnesium, iron, manganese, copper, and zinc. The method for producing a fertilizer according to any one of 9 . The fertilizer according to any one of claims 1 to 10 , wherein the skeleton modifier added in the skeleton modifier addition step contains iron or a compound thereof, and the melting treatment step is performed in a reducing atmosphere or an oxidizing atmosphere. Manufacturing method. The method for producing a fertilizer according to any one of claims 1 to 11, wherein the melting step is performed under a condition in which a temperature of the slag is adjusted in a range of 1000 ° C to 1700 ° C. The method for producing a fertilizer according to claim 12 , wherein the melting step is performed under a condition in which a temperature of the slag is adjusted to 1300 ° C or lower. The fertilizer production according to any one of claims 1 to 13 , wherein the cooling processing step includes a step of slowly cooling and solidifying the slag melted in the melting processing step or a rapid cooling using a water cooling mechanism. mETHODS. A rotary surface melting furnace used in a method of manufacturing a fertilizer as claimed in any one of 請 Motomeko 1 14,
An inner cylinder erected around the ceiling where the combustor is disposed, and a bottomed outer cylinder with a tap hole formed in the center of the bottom are arranged around a common axis, and the outer cylinder and the inner cylinder The molten material containing phosphorus-containing sludge or phosphorus-containing incinerated ash charged into the accumulation part between the cylinder is moved from the lower edge of the inner cylinder to the lower part of the ceiling by the relative rotation of the outer cylinder and the inner cylinder Moved to the main combustion chamber of the space, the exposed surface is melted by the combustion flame of the combustor, and the molten slag is dropped and discharged from the outlet.
A rotary surface melting furnace provided with a residence time adjusting mechanism for adjusting a residence time of the slag melted in the main combustion chamber. The dwell time adjustment mechanism is embodied by an interval adjustment mechanism that adjusts the interval between the lower edge of the inner cylinder and the bottom of the outer cylinder by relatively moving the inner cylinder and the outer cylinder in the common axis direction. The rotary surface melting furnace according to claim 15 , wherein the rotary surface melting furnace is made. A rotary surface melting furnace used in the method for producing a fertilizer according to any one of claims 1 to 14 ,
An inner cylinder erected around the ceiling where the combustor is disposed, and a bottomed outer cylinder with a tap hole formed in the center of the bottom are arranged around a common axis, and the outer cylinder and the inner cylinder The molten material containing phosphorus-containing sludge or phosphorus-containing incinerated ash charged into the accumulation part between the cylinder is moved from the lower edge of the inner cylinder to the lower part of the ceiling by the relative rotation of the outer cylinder and the inner cylinder It is configured to move to the space, melt the exposed surface by the combustion flame of the combustor, and drop and discharge the molten slag from the outlet, and phosphorus-containing sludge or phosphorus-containing incineration charged into the accumulation unit A rotary surface melting furnace provided with an addition mechanism for adding the skeleton modifier to ash.

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