JP4530702B2 - Landscape gravel and its manufacturing method - Google Patents

Description

  INDUSTRIAL APPLICABILITY The present invention has an excellent effect on measures against heat islands, mainly on the median strip of roads, on the green zone of parks, on paving stones, or on the ground as gardening gravel, etc., or on the roof of buildings, etc. The present invention relates to porous landscape gravel and its manufacturing method.

Landscape gravel, which is effective for heat island countermeasures, is required to be porous and to absorb and retain a large amount of water. Porous landscape gravel that can retain a large amount of moisture takes a large amount of heat of vaporization from the surroundings when vaporizing the retained moisture, and thus has a great cooling effect. For this reason, it is effective for heat island countermeasures by laying porous landscape gravel and replenishing water. In summer, the heat island phenomenon occurs in many places, making the living environment worse. For example, in cities where buildings are densely packed, asphalt and concrete such as rooftops, parks, gardens, and roads are heated by solar heat, and a heat island phenomenon occurs. In order to eliminate the temperature rise caused by the heat island phenomenon and make the living space comfortable, the interior of the building is cooled. However, since cooling exhausts heat that is greater than the amount of heat that it cools, the temperature outside the building rises further, causing the city temperature to rise. For this reason, a method for fundamentally eliminating the heat island phenomenon is required. Porous landscape gravel has a feature that makes the landscape beautiful while eliminating the heat island phenomenon. However, gravel produced by crushing ordinary stones cannot eliminate heat islands. Landscape gravel to eliminate the heat island phenomenon requires all of the following physical properties (1) to (4).
(1) It must be porous and contain a large amount of water
(2) Light
(3) Having strength not to be destroyed even if walking on
(4) Be inexpensive

  Landscape gravel has a large construction area, so no matter how excellent it is, it cannot be put into practical use if the heat island phenomenon cannot be solved economically and economically. Moreover, since it cools using the vaporization heat of water, if a large amount of water cannot be retained, a heat island cannot be eliminated efficiently for a long time. If it is not light, it cannot be laid on the roof of a building. Furthermore, since it is used in places where people walk on in many applications, the application is severely limited by the strength of walking and breaking.

The present inventor has succeeded in granulating fly ash containing unburned carbon for the purpose of realizing this, and firing it to produce porous landscape gravel (see Patent Document 1). .
Japanese Patent Application No. 2003-413822

  This landscape gravel is sintered in a porous state by eliminating unburned carbon contained in fly ash and providing innumerable fine voids. However, this landscape gravel is affected by the amount of unburned carbon contained in the porous state, and when fly ash with little unburned carbon is used, there is a drawback that the porosity becomes low. Furthermore, the void formed by burning off the unburned carbon is close to closed cells. Landscape gravel can smoothly enter and exit the water that has absorbed moisture, with a porous state close to open cells. However, since unburned carbon is a fine particle, the void formed by burning it out becomes a fine cavity, and there is a drawback that it cannot be brought into a state close to open cells where water can be taken in and out smoothly.

  As a result of repeating various experiments for the purpose of eliminating this drawback, the present inventor has found that the waste fibers contained in the papermaking sludge can be made porous in an ideal state. Papermaking sludge is a waste component that precipitates at the bottom of the dissolution tank when used paper is dissolved and recycled. Therefore, it contains fine short fibers which are not preferable as paper. When the fine short fibers contained in the papermaking sludge are burned off and a void is provided in the landscape gravel, it becomes a state close to open cells, and an ideal void that allows water to be taken in and out smoothly can be provided. Also, since paper sludge takes time and money to dispose of it, it can be used as a raw material to realize the feature that waste can be effectively reused while reducing the cost of landscape gravel. Furthermore, papermaking sludge contains inorganic substances in addition to organic components such as fibers. However, since these inorganic substances are silica, alumina, calcium oxide, etc., which are also contained in fly ash, they are used in fly ash. When added and fired, the inorganic material is sintered together with the fly ash inorganic material. For this reason, by mixing paper-making sludge with fly ash and sintering it, a truly ideal landscape gravel can be mass-produced at low cost.

  Therefore, the first important object of the present invention is to provide a paper sludge that is not effectively used as industrial waste, while providing innumerable fine voids inside the paper sludge. An object of the present invention is to provide a porous landscape gravel having a high porosity, which can be in an open-celled state where water can smoothly enter and exit the void, and a method for producing the same.

  Furthermore, the second object of the present invention is to provide a porous landscape gravel which can be controlled to an optimum porosity and strength by adjusting the mixing ratio of fly ash and papermaking sludge and a method for producing the same.

  In the method for producing landscape gravel according to claim 1 of the present invention, unfired papermaking sludge containing 10% by weight or more of organic components containing fibers and 40% to 70% by weight of water is contained in fly ash. Granulation step of adding and further granulating into unsintered particles having an average particle size of 2 mm to 30 mm using both the water contained in the papermaking sludge and the added water as binders And a sintering step of sintering the unsintered particles obtained in this granulation step to a temperature at which the compressive strength is 50 N or more and the water absorption is 35% by weight or more.

  In the method for producing landscape gravel according to claim 2 of the present invention, 10 to 500 parts by weight of papermaking sludge is mixed with 100 parts by weight of fly ash.

  The manufacturing method of landscape gravel of the present invention uses fly ash containing unburned carbon for fly ash.

The method for producing landscape gravel according to claim 3 of the present invention uses a raw material comprising paper sludge and fly ash containing 2% by weight or more of iron oxide. Furthermore, the manufacturing method of the landscape gravel of Claim 4 of this invention makes the calcination temperature in a baking process 1000-1300 degreeC.

The porous landscape gravel according to claim 5 of the present invention includes fly ash, an unfired papermaking sludge containing 10% by weight or more of organic components including fibers, and containing 40% to 70% by weight of water. The mixture with water is granulated into particles having an average particle diameter of 2 mm to 30 mm using both water contained in the papermaking sludge and added water as a binder, and has a compressive strength of 50 N or more, water absorption Is sintered at a temperature of 35 wt% or more.

The porous landscape gravel according to claim 6 of the present invention is granulated with 100 parts by weight of fly ash and 10 to 500 parts by weight of papermaking sludge.

The porous landscape gravel according to claim 7 of the present invention has a water absorption rate of 40% by weight or more. Furthermore, the porous landscape gravel according to claim 8 of the present invention contains 2% by weight or more of iron oxide, and the surface is colored with iron oxide.

  The landscape gravel of the present invention and the method for producing the same have the feature that an infinite number of fine voids are provided inside, and an open cell state that allows smooth entry and exit of water into the void is provided. This is because the landscape gravel of the present invention and the method for producing the same include the addition of paper sludge containing 10% by weight or more of organic components such as fibers to fly ash, or 10% by weight or more of organic components such as fibers. Water is added to the baked paper sludge as a binder and granulated into unsintered particles having an average particle size of 2 mm to 30 mm. The unsintered particles have a compressive strength of 50 N or more and a water absorption of 35% by weight. This is because sintering is performed at the above temperature. The landscape gravel manufactured as described above can provide innumerable fine voids inside by the short fibers of the papermaking sludge. In particular, the short fibers of the paper sludge have a fluffy surface raised on the surface, so that the short fibers can form a porous state in which large voids and small voids are continuously mixed. Therefore, it is possible to provide an ideal space that can realize a porous state close to open cells and allow water to flow in and out smoothly.

  Furthermore, the landscape gravel of the present invention and the method for producing the same also have an advantage that an ideal void can be provided while effectively utilizing papermaking sludge, which is an industrial waste that has conventionally been time-consuming and expensive to dispose of. Since paper sludge is time-consuming and expensive to dispose of, it is meaningful that waste can be reused effectively while reducing the cost of landscape gravel by using it as a raw material. Furthermore, paper sludge contains inorganic substances such as silica, alumina, and calcium oxide contained in fly ash in addition to organic components such as fibers. Sintered together with fly ash minerals and mixed with paper ash to sinter the fly ash and sinter, it also has the advantage of being able to mass produce the ideal landscape gravel at low cost.

  Furthermore, the landscape gravel according to the present invention and the method for producing the same also have an advantage that the optimum porosity and strength can be controlled by adjusting the mixing ratio of fly ash and paper sludge.

  Examples of the present invention will be described below. However, the Example shown below illustrates the landscape gravel and its manufacturing method for materializing the technical idea of this invention, Comprising: This invention does not specify landscape gravel and its manufacturing method below.

The landscape gravel of this invention is manufactured in the following processes.
(1) Granulation step In this step, papermaking sludge that is not fired is mixed with fly ash, or undried papermaking sludge that is not fired is granulated using water as a binder to form unsintered particles. As the papermaking sludge, one containing 10% by weight or more, preferably 15% by weight or more, more preferably 20% by weight or more of organic components such as fibers is used. Further, the papermaking sludge is dehydrated with a filter press or the like, and is not dried or fired. This papermaking sludge contains 40 wt% to 70 wt% water. Using this moisture content as a binder, a mixture of fly ash and paper sludge is granulated, or paper sludge is granulated. This papermaking sludge contains water in fine short fibers and inorganic components. In the present invention, the burned ash of paper sludge is not mixed with fly ash and granulated. In the present invention, since the dewatered paper sludge is granulated and fired without drying and without firing, the processing cost can be remarkably reduced and landscape gravel with ideal physical properties can be obtained.

  Also, the fibers contained in the papermaking sludge are very thin and short. This fiber is burnt down to create countless fine voids inside the landscape gravel. Therefore, by using a raw material papermaking sludge having a high content of organic components such as fibers, the porosity of the sintered landscape gravel can be increased, that is, the water absorption rate can be increased. In particular, voids due to organic components such as fibers are not in the form of closed cells as in unburned carbon, but are in the form of open cells and become innumerable fine voids that are continuous with each other. The voids of this structure retain a large amount of water in a state where it can easily enter and exit smoothly.

  When there are too many organic components, such as a fiber, contained in papermaking sludge, the porosity of the landscape gravel which sintered this will become high and the whole intensity | strength will fall. Therefore, the papermaking sludge having an excessive content of organic components such as fibers is mixed with fly ash to adjust the porosity. Further, by using fly ash containing unburned carbon, the porosity of landscape gravel can be controlled with unburned carbon of fly ash and organic components such as fibers of paper sludge.

  Further, as fly ash and paper sludge, one containing iron oxide in one or both is used. Iron oxide becomes a pigment that colors the surface of landscape gravel in a beautiful natural color.

  Water is used as a binder to granulate by combining papermaking sludge and fly ash, but synthetic resin binders that are burned off during the firing process, such as synthetic resin binders such as vinyl acetate resin and PVA, are added to water. You can also In the granulation step, fly ash and papermaking sludge are sufficiently kneaded to uniformly disperse organic components such as fibers contained in the papermaking sludge. The fly ash and papermaking sludge containing moisture are filled in the molding chamber, and the molding chamber is closed and granulated into unsintered particles. When the amount of fly ash for papermaking sludge is increased and the amount of water necessary for granulation is reduced, water is added so that the water content is 40 wt% to 70 wt%, and organic components such as fibers are added. Knead until uniformly dispersed.

  The present invention does not specify a method of granulating fly ash and papermaking sludge as a method of filling a molding chamber. For example, extrude fly ash or papermaking sludge into a cylindrical or prismatic shape, cut it into a predetermined length to make it a short cylindrical shape or prismatic shape, and then roll it by sandwiching it between two plates. It can also be molded and granulated into a shape approximating a sphere. The unsintered particles are preferably granulated into a spherical shape. However, it is not formed into a perfect sphere, but is formed into a shape close to a sphere and a shape such as a polyhedron or a polyhedron with rounded corners. Moreover, it can also granulate in the shape where various shapes are mixed so that it may be close to natural gravel. In the granulation step, the particles are granulated into unsintered particles having an average particle diameter of 2 to 30 mm, preferably 3 to 20 mm, more preferably 5 to 15 mm.

(2) Firing step After the unsintered particles are dried, they are sintered to burn off organic components such as fibers contained in the papermaking sludge and sinter into an open-celled porous state. The firing temperature is 1000 ° C. to 1300 ° C., preferably 1000 to 1200 ° C., more preferably 1050 ° C. to 1200 ° C., and the firing time at the set firing temperature is 1 to 5 hours. If the firing temperature is low or the firing time is short, sufficient strength cannot be obtained by sintering. On the other hand, if it is too high, the inorganic component is melted and the voids are reduced, resulting in a decrease in water absorption and water retention. In the firing step, the organic particles such as fibers contained in the unsintered particles are burned away and become a porous state. In addition, the unsintered particles in which paper sludge is mixed with fly ash containing unburned carbon also burns away the unburned carbon of fly ash to form fine voids. The landscape gravel is a landscape gravel that contains a large amount of moisture by providing open-cell voids due to organic components such as fibers and closed-cell voids due to unburned carbon.

  FIG. 1 is an electron micrograph showing a state where the interior of landscape gravel is sintered and becomes porous. As shown in this figure, a lot of extremely fine continuous voids are formed inside the landscape gravel, and the absorbed water is retained here. The landscape gravel that retains water in the fine voids inside in this state realizes extremely excellent water retention and retains water for a long period of time.

Landscape gravel is manufactured in the following process.
(1) Granulation process 100 parts by weight of fly ash and 100 parts by weight of papermaking sludge are thoroughly mixed to form a burned material mixed inorganic material in a state where organic components such as fibers of the papermaking sludge are uniformly dispersed. Grain. Fly ash contains 30% by weight of unburned carbon. Papermaking sludge contains 30% by weight of organic components such as fibers. Papermaking sludge contains water, but fly ash contains almost no water, so water is added so that the total water content is 50% by weight, and water is granulated as a binder. This papermaking sludge is dehydrated with a filter press and used without being dried or fired. The papermaking sludge contains 50% water by weight. The average particle diameter of the unsintered particles to be granulated is about 10 mm.

(2) Firing step After the unsintered particles are dried, they are carried into a firing furnace and fired at a firing temperature of 1200 ° C. for 2 hours. The firing furnace raises the temperature in the furnace with a temperature gradient of 200 ° C./hour, holds it at 1200 ° C. for 2 hours, naturally cools, and takes out landscape gravel from the firing furnace.

  The landscape gravel produced in the above process has an extremely high water absorption rate of about 61% by weight. Landscape gravel having a water absorption rate of 61% by weight holds 61 g of water in 100 g of landscape gravel. This landscape gravel absorbs water in extremely fine voids, thus realizing extremely good water retention. In particular, the landscape gravel is provided in a state where a closed-cell void due to unburned carbon and an open-cell void due to organic components such as fibers communicate with each other. Therefore, the landscape gravel produced in this embodiment retains water for a long time in a state where a large amount of water can be smoothly taken in and out. For example, when measuring a state in which moisture decreases in a room at a temperature of 40 ° C. and a humidity of 80%, the landscape gravel of this example is extremely excellent in retaining 38% by weight of water even after 400 hours (16.7 days). Water retention.

  When the void distribution of the landscape gravel obtained in this example is measured by the mercury injection method, 2-20 μm and very fine voids occupy most.

  In addition, the landscape gravel produced was laid on concrete and the ground, and it was strong enough to not be destroyed even when walking on it. In order to measure the breaking strength, the scenic gravel sintered into a spherical shape is sandwiched between parallel metal surfaces that do not deform, and even if it is locally pressed, it is not broken until it is pressed with a pressure of about 150 N. In this destructive test, landscape gravel is pressed locally in a very narrow area, so if a rubber-like elastic body is placed between the landscape gravel and the pressing surface and the area to be pressed is increased, the fracture strength is extremely high. growing. In reality, this is the situation when you step on the landscape gravel with your shoes. This is because the bottom of the shoe is elastically deformed. In addition, when the landscape gravel is stepped on the sole, many landscape gravel steps on the sole together, so the pressure acting on one landscape gravel is smaller than the weight, and the above-mentioned landscape gravel steps on and breaks down. It will never be done.

  Landscape gravel is produced in the same manner as in Example 1 except that the firing temperature in the firing step (2) is changed from 1200 ° C to 1150 ° C. The landscape gravel produced in this example has a water absorption of about 63% by weight. Landscape gravel having a water absorption rate of 63% by weight holds 63 g of water in 100 g of landscape gravel. Since this landscape gravel also absorbs water into extremely fine voids, it achieves extremely excellent water retention, just like the landscape gravel of Example 1, and retains about 40% of water after 400 hours (16.7 days). Keep water.

  In addition, the landscape gravel produced was laid on concrete and the ground, and it was strong enough to not be destroyed even when walking on it. When landscape gravel sintered in a spherical shape is sandwiched between parallel metal surfaces that do not deform and pressed locally and the fracture strength is measured, it is not destroyed until it is pressurized at a pressure of about 130 N.

  Porous landscape gravel is produced in the same manner as in Example 1 except that the burned-material mixed inorganic material used in the granulation step is only papermaking sludge containing organic components such as 30% by weight of fibers. The landscape gravel produced in this example has a water absorption of about 51% by weight. Landscape gravel having a water absorption rate of 51% by weight holds 51 g of water in 100 g of landscape gravel. Since this landscape gravel also absorbs water into extremely fine voids, it achieves extremely excellent water retention, just like the landscape gravel of Example 1, with about 30% moisture after 400 hours (16.7 days). Keep water.

  In addition, the landscape gravel produced was laid on concrete and the ground, and it was strong enough to not be destroyed even when walking on it. When the gravel-sintered landscape gravel is sandwiched between parallel metal surfaces that do not deform and pressed locally to measure the breaking strength, it is not destroyed until it is pressed at a pressure of about 118 N.

  In the firing step, porous landscape gravel is produced in the same manner as in Example 3 except that the firing temperature is changed from 1200 ° C to 1060 ° C. The landscape gravel produced in this example has a water absorption of about 60% by weight. Since this landscape gravel also absorbs water in extremely fine voids, it achieves extremely excellent water retention, just like the landscape gravel of Example 1, and retains about 35% of moisture after 400 hours (16.7 days). Keep water.

  In addition, the landscape gravel produced was laid on concrete and the ground, and it was strong enough to not be destroyed even when walking on it. When landscape gravel sintered in a spherical shape is sandwiched between parallel metal surfaces that are not deformed and pressed locally to measure the breaking strength, it is not broken until it is pressed at a pressure of about 110 N.

It is an electron micrograph of the porous landscape gravel concerning one Example of this invention.

Claims (8)

  Add unburned paper sludge containing 10% by weight or more of organic components containing fibers to fly ash containing unburned carbon and 40 to 70% by weight of water, and then add water. A granulation step of granulating into unsintered particles having an average particle diameter of 2 to 30 mm using both water contained in the papermaking sludge and added water as a binder, and unsintered obtained in this granulation step A method for producing porous landscape gravel comprising a sintering step of sintering particles to a temperature at which the compressive strength is 50 N or more and the water absorption is 35% by weight or more.   The method for producing porous landscape gravel according to claim 1, wherein 10 to 500 parts by weight of papermaking sludge is mixed with 100 parts by weight of fly ash.   2. The method for producing porous landscape gravel according to claim 1, wherein the raw material comprising papermaking sludge and fly ash contains 2% by weight or more of iron oxide.   The method for producing porous landscape gravel according to claim 1, wherein the firing temperature in the firing step is 1000 to 1300 ° C.   A mixture of fly ash containing unburned carbon, unburned paper sludge containing 10% by weight or more of organic components containing fibers and 40% to 70% by weight of water, and water It is granulated into particles having an average particle size of 2 mm to 30 mm using both the water contained in the sludge and the added water as a binder, and baked at a temperature that gives a compressive strength of 50 N or more and a water absorption of 35 wt% or more. Porous landscape gravel that is tied. The porous landscape gravel according to claim 5 , wherein 100 parts by weight of fly ash and 10 to 500 parts by weight of papermaking sludge are granulated. The porous landscape gravel according to claim 5 , wherein the water absorption is 40% by weight or more. The porous landscape gravel according to claim 5 , comprising 2% by weight or more of iron oxide and having its surface colored with iron oxide.