JP2008073575A - Waste landfilling structure, slag sand for fine particle layer of waste landfilling structure, and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide ferronickel slag sand suitable for fine particle layers of multilayered cover soil. <P>SOLUTION: The slag sand for fine particle layers of the multilayered cover soil is manufactured by reduction-refining nickel ore at high temperature together with a reducing agent, pulverizing the obtained clinker, and ferronickel slag sand formed with broken faces on the particle surfaces is used for the fine particle layers of multilayered cover soil. The clinker is pulverized to a particle size of at least 5 mm. The pulverized ferronickel slag sand is charged into a water tank, subjected to floating separation of fine particles, and classified for size control. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention particularly relates to a waste landfill structure for draining permeated water penetrating a waste landfill to the side, a slag sand for a fine particle layer of the waste landfill structure, and a method for producing the same.

  There is a problem that water permeating into the landfill of waste becomes sewage and pollutes the surrounding environment. In order to prevent this problem, there is a waste landfill structure using multi-layer cover soil. FIG. 5 shows a schematic configuration of the multi-layer cover. As shown in the figure, the multi-layer covering soil forms a capillary barrier layer 5 formed by covering the waste 1 with the viscous soil layer 2 and then laying the reki layer 3 and subsequently the fine grain layer 4, and finally the whole Is covered with the viscous soil 6 having good water shielding properties. Here, the layer boundary between the reki layer 3 and the fine grain layer 4 is given a gradient. This is because the fine particle layer 4 having a large water content and composed of small particles is provided on the upper layer of the large particle layer 3 constituting the capillary barrier layer 5 so that the permeated water due to rainfall or the like is stopped by the fine particle layer 4. In addition, a capillary barrier effect is used, in which a water guide gradient is applied to the covering soil to flow down to the side along the boundary surface between the reki layer 3 and the fine grain layer 4.

  As a result, the permeated water that has passed through the surface of the multi-layered soil and infiltrated into the fine-grained layer and moved downward is changed in the direction of the flow along the gradient in the vicinity of the boundary with the revitalized layer, and is retained in the fine-grained layer. While flowing down, water is removed. It is possible to reduce the amount of rainwater penetrating water of landfill waste (for example, shown in Patent Document 1).

  By the way, it is the property or material of sand that has the greatest influence on the performance of the capillary barrier layer (drainage, retention of permeated water). Sand suitable for the fine-grained layer of the capillary barrier layer is required to have a large amount of permeated water staying in the unsaturated region and excellent drainage. Thereby, a large amount of water permeating from the surface layer can be drained to the side. If the capillary force of the fine-grained layer is small, the amount of water that has permeated into the fine-grained layer is reduced, and even a small amount of rainfall may cause the infiltrated water to reach the waste layer and promote groundwater contamination. Therefore, it is desirable that the capillary force of the fine particle layer is large.

On the other hand, the coarse-grained layer has a higher saturated water permeability than sand, but has a low water permeability in the unsaturated region and a weak force for sucking moisture. Since the vicinity of the boundary between the fine-grained layer and the leech layer is always unsaturated, the water that has passed through the cohesive soil is retained in the fine-grained layer by the capillary force of the sand, and laterally due to the gradient of the boundary between the sand and the leech layer. Moved to and eliminated. In recent years, using such a principle, there are increasing cases of applying multi-layer cover soil to a landfill site for waste.
JP 2001-17933 A

  In a waste burial structure using multi-layered soil, a capillary barrier layer with a gradient layer consisting of a bleed layer and a fine-grained layer on top of the burial waste protective layer and a topsoil layer above it is formed. It is formed. When forming this capillary barrier layer, it is necessary to find sand suitable for the fine-grained layer. The sand used in the conventional fine-grained layer is first sampled from the sand near the site and subjected to a performance test to form a fine-grained layer. It was determined whether or not it had suitable water retention and drainage.

  However, in order to satisfy the capillary barrier layer having the lateral drainage, it is necessary to impart the contradictory properties that the fine-grained layer has good water permeability and good water retention capability. There are few local sands of good quality and there is a problem that it is difficult to find such sand at present. In addition, depending on the properties of the sand constituting the fine-grained layer, there was a risk that the gap could be clogged due to overconsolidation due to secular change, and the drainage could not be secured due to the local reverse gradient.

  In order to improve the above-mentioned problems of the prior art, an object of the present invention is to provide an optimum fine-grained layer constituting a capillary barrier layer in a waste landfill.

  The waste landfill structure of the present invention is a ferronickel obtained by reducing and refining nickel ore at a high temperature together with a reducing agent on the fine particle layer of the capillary barrier layer formed of the fine particle layer and the leech layer formed on the upper surface of the landfill waste. It is characterized by using ferronickel slag sand in which a slag clinker is crushed to form a fracture surface with water retention on the grain surface.

  In this case, the clinker is preferably pulverized to at least a particle size of 5 mm. The particle size distribution of the ferronickel slag sand is as follows: the passing mass percentage is 10-30% when the particle size is 0.15 mm, 25-60% when the particle size is 0.3 mm, 60-90% when the particle size is 0.6 mm, It is good to comprise 1.2mm with 85-100%. Further, the pulverized ferronickel slag sand may be put into a water tank to float and separate fine powder.

  The waste landfill slag sand of the present invention is a crushed ferronickel slag clinker made by reducing and refining nickel ore with a reducing agent at a high temperature to form a fracture surface with water retention on the grain surface. The fine powder is floated and separated to adjust the particle size to provide water permeability.

  The method for producing slag sand for a fine-grained layer of the waste landfill structure of the present invention comprises refining nickel ore together with a reducing agent at a high temperature, crushing the resulting clinker to form a fracture surface on the grain surface. The ferronickel slag sand that has been crushed is put into a water tank, and fine particles are removed by a floating separation means to adjust the particle size.

  In addition to ferronickel obtained by reducing and refining nickel oxide ore and a reducing agent, there is ferronickel slag sand as a by-product. Ferronickel slag sand is used for aggregates and filling materials for concrete, and has low water absorption and relatively high specific gravity. Therefore, the inventor pays attention to the physical properties of ferronickel slag sand, and obtains ferronickel slag sand that can perform effective lateral drainage of the capillary barrier layer. That is, the ferronickel slag sand of the present invention crushes the clinker obtained after reductive refining of nickel ore and a reducing agent to at least a particle size of 5 mm. Therefore, ferronickel slag sand having a particle size of 5 mm or less has irregularities on the surface and has an angular shape. For this reason, ferronickel slag sand has a large contact area with water on the surface, and has higher water retention and water absorption than spherical sand. Therefore, drainage and osmotic water retention are improved by using it for the fine-grained layer of the multi-layer covering soil.

  The particle size distribution of the ferronickel slag sand is as follows: the passing mass percentage is 10-30% when the particle size is 0.15 mm, 25-60% when the particle size is 0.3 mm, 60-90% when the particle size is 0.6 mm, and 1 particle size. .2mm is adjusted to 85-100%. For this reason, the fine-grained layer has water permeability and water retention, has the drainage required for the capillary barrier layer and the retentivity of the permeated water, and can promote the side drainage of the permeated water.

  The crushed ferronickel slag sand contains fine powder having a fine particle size. When slag sand containing fine powder is used for the fine-grained layer of the multi-layered soil, the fine powder is drained laterally together with the permeated water, causing sewage. Moreover, the fine powder contained in the slag sand becomes an obstacle to the permeated water that permeates the fine-grained layer, and the drainage performance may be impaired. Therefore, fine powder can be removed by floating and separating in a water tank.

  In the production of ferronickel, slag sand produced as a by-product is used effectively as a fine-grained layer in the capillary barrier layer to stabilize quality, reduce costs, and improve workability and drainage. The application range of excellent ferronickel slag sand can be expanded.

  The waste landfill structure and the waste land slag sand of the waste landfill structure according to the present invention and the manufacturing method thereof will be described in detail below with reference to the accompanying drawings. Drawing 1 is an explanatory view of the manufacturing method of the slag sand for fine grain layers of the waste landfill structure concerning an embodiment. FIG. 2 is an explanatory view of a classification process of ferronickel slag sand.

  First, the manufacturing method of the ferronickel slag sand used as a raw material is demonstrated below. As shown in FIG. 1, nickel oxide ore (S100) and anthracite / limestone (S110) are used as raw materials for ferronickel, and the mixing ratio is 100-150 kg of anthracite coal per ton of nickel oxide ore as an example. 30-80 kg is added and mixed.

  The mixed raw materials are charged into a heating furnace such as a rotary kiln. In the rotary kiln, the nickel oxide and iron oxide content in the ore are reduced to form a clinker by reducing and refining while rolling in an oxidizing combustion stream at a maximum temperature of 1400 ° C. (S120). The rotary kiln is a circular long heating furnace that rotates around an axis at a constant speed. Moreover, since the raw material supply port of the rotary kiln is set slightly higher than the discharge port, the rotary kiln is inclined from the upper raw material supply port toward the lower discharge port. A heating burner is provided at the outlet of the rotary kiln. The heating burner heats the inside of the kiln from the lower discharge port toward the upper raw material supply port. The raw material supplied to the raw material supply port is baked inside the rotary kiln and moves toward the discharge port. The internal temperature is set to about 1400 ° C., which is optimal for firing, by a heating burner provided at the discharge port. The raw material heated in the furnace is fired to become a clinker.

  The clinker discharged from the rotary kiln is air cooled and then water cooled (S130). Then, the cooled clinker is pulverized with a tube mill until the particle size becomes at least 5 mm (S140). The clinker after pulverization is subjected to specific gravity selection and magnetic selection, and clinker having a large particle size is selected to make the particle size uniform (S150). Further, the particle size of the clinker is adjusted by a classification process (S160). As shown in FIG. 2, the clinker after sorting is introduced into the floating separation apparatus 10. The levitation separation device 10 has a basic configuration of a water tank 12, a bubble generation means 14, and a levitation separation means 16.

  The obtained pulverized product is put into the water tank 12 and subjected to a floating separation process. The water tank 12 used for floating separation is a funnel-shaped water tank 12 that stores a predetermined amount of water. The water tank 12 has an upper water surface open, and a discharge opening 18 is provided at the center of the lower part of the water tank 12. The clinker crushed from the upper part of the floating separator 10 is put in. The clinker descends the funnel-shaped side surface in the water tank toward the bottom. A plurality of bubble generating means 14 are attached to the slope in the water tank. The bubble generating means 14 is connected to a compressor via a distributor, and can arbitrarily adjust the amount of bubbles generated. Bubbles are generated in the tank by the bubble generating means 14, and the clinker descending in the tank and the bubbles are mixed. At this time, the fine powder in the clinker separates from the slag sand and floats on the water surface together with the bubbles. Floating separation means 16 having a baffle plate is arranged on the water surface, and the floating material (scum) is pushed out to the discharge port 22 on the water surface to overflow to the outside. The slag sand separated from the fine powder is drawn out from the opening / closing port 18 at the bottom of the tank by a certain amount and sent to the classifier 30.

  The classifier 30 according to the present embodiment will be described by using an Akins classifier as an example. The classifier 30 is basically composed of a settling tank 32 and a screw 34. The slag sand drawn out from the floating separation device 10 is introduced into the settling tank 32 of the classifier 30. A lower end portion of a screw 34 is inserted in the settling tank 32, and slag sand having a predetermined particle size precipitated in the tank is pulled upward by a screw 34 that rotates at a predetermined rotation speed.

  The physical property of the ferronickel slag sand obtained by the said manufacturing method is demonstrated using FIG. FIG. 1 (1) shows the permeability test in the unsaturated region, where the vertical axis indicates the unsaturated hydraulic conductivity k (cm / sec) and the horizontal axis indicates the negative pressure head Ψ (cm). Further, (2) is a water retention test, where the vertical axis represents volume water content θ−minimum volume water content θr (−), and the horizontal axis represents negative pressure head Ψ (cm). White circles indicate ferronickel slag sand of the present invention, and black circles indicate natural sand. Here, the natural sand according to the embodiment has been adjusted in particle size produced in Chiba Prefecture, which has shown high performance (water retention and water permeability) as a fine-grained layer of the Caprary barrier layer so far in the construction results and research results of the capillary barrier layer. Mountain sand is used.

  The water permeability test in the unsaturated region is an index indicating the lateral drainage of the fine-grained layer of the capillary barrier layer. The larger the value of the unsaturated water permeability test, the better the lateral drainage. The water retention test is an index indicating the amount of water that has permeated into the fine-grained layer (volume water content θ−minimum volume water content θr).

  The permeability test of the unsaturated region in the examples shows that when the pressure head is 20 cm, ferronickel slag sand is 7.5 times natural sand, and when the pressure head is 40 cm, ferronickel slag sand is 80 times natural sand. It always exceeded natural sand regardless of the water head.

  In the water retention test of the examples, when the pressure head is 20 cm, the ferronickel slag sand is 1.5 times the natural sand, and when the pressure head is 40 cm, the ferronickel slag sand is 3.7 times the natural sand. Regardless of always surpassed natural sand. This property can be influenced by the particle size distribution, the shape of the sand material grains, and the surface roughness.

  As shown in FIG. 4, the particle size distribution of the obtained ferronickel slag sand of the present invention is such that the passing mass percentage is 10-30% when the particle size is 0.15 mm, 25-60% when the particle size is 0.3 mm, and 0% when the particle size is 0. .6 mm is composed of 60-90%, and the particle diameter of 1.2 mm is composed of 85-100%, and the particle diameter of 0.075 mm is 20% or less. Thereby, drainage and stagnation water retention can be combined. Ferro-nickel slag sand has a low water absorption rate and has excellent drainage as a sand layer material for multi-layered soil. Moreover, the rolling workability is improved, and the rolling frequency can be reduced by 60 to 30% as compared with natural sand.

  It is preferable that the sand layer used for the multi-layer covering has a Mohs hardness of 5 or more. The ferronickel slag sand of the present invention has a Mohs hardness of 4.5 to 6.5. As a result, it is possible to prevent the grains from being broken and finely divided at the time of rolling and closing the voids in the sand layer to deteriorate the drainage.

Chemical components of ferronickel slag sand of the present _{invention, SiO 2; 50-60%, MgO} ; 40-20%, CaO; 10-2%, FeO; a 12-5%. SiO ₂ , MgO, and FeO are components derived from nickel ore, and most of the mineral composition is a dense aggregate of Enstatite (MgO · SiO ₂ ), in addition to Forsterite (2MgO · SiO ₂ ) and a small amount of SiO _2. Both are extremely stable crystal structures and are equivalent to natural minerals. CaO is added to lower the softening point temperature of the insert in the ferronickel refining process.

  Thus, according to the ferronickel slag sand according to the present invention, the water absorption rate is low, the density is large, the cost is low, and the ferronickel slag sand is effectively used as a substitute for natural sand and as a reuse of ferronickel slag. can do. The ferronickel slag sand used for the fine particle layer of the Caprary barrier layer can have water permeability suitable for the fine particle layer by the particle size distribution in which the classification process is controlled. In addition, the grains may be destroyed during crushing and the fine-grained layer may be clogged, but such problems can be eliminated by controlling the composition of the ferronickel slag sand and the heating process to ensure the hardness of the sand grains. . The above-mentioned material having a larger capillary force than natural sand can be obtained by making the particle size distribution appropriate, and making the surface rough particles with an angular shape. These are possible by controlling the crushing / classifying process. Furthermore, the above-mentioned material with less turbidity of waste water can be obtained by controlling the classification process. There is a possibility that fine powder that may be taken out by the waste water passing through the fine-grained layer is removed in the classification process, and unburned coal remaining in the material after refining may be mixed. These foreign substances having a light specific gravity are removed by floating separation by aeration.

  As a result of conducting a performance test of the capillary barrier layer, it was confirmed that a larger amount of permeated water could be drained laterally than the natural sand used in the comparative example, and it was excellent as a material for the fine layer of the capillary barrier layer. It is also robust and has excellent workability.

It is explanatory drawing of the manufacturing method of the slag sand for fine particle layers of the waste landfill structure which concerns on embodiment. It is explanatory drawing of the classification process of ferronickel slag sand. It is explanatory drawing which shows the physical property of the slag sand of the fine grain layer of the multilayer covering soil of this invention. It is a figure which shows the particle size accumulation curve of the ferronickel slag sand which concerns on embodiment. It is a figure which shows the structure outline of a multilayer covering soil.

Explanation of symbols

1 ……… Waste 2 ……… Viscous soil layer 3 ……… Reki layer 4 ……… Fine grain layer 5 ……… Capillary barrier layer 6 ……… Viscous soil 10 ……… Left Separation device, 12 ......... Water tank, 14 ......... Bubble generating means, 16 ......... Floating separation means, 18 ......... Opening and closing port, 22 ......... Discharge port, 30 ......... Classifier, 32 ......... Precipitation tank, 34 ... Screw.

Claims (6)

  The fine particle layer of the capillary barrier layer consisting of the fine particle layer and the leki layer formed on the upper surface of the landfill waste is crushed with ferronickel slag clinker obtained by reducing and refining nickel ore with a reducing agent at high temperature. Waste landfill structure characterized by using ferronickel slag sand having a fracture surface with water retention.   2. The waste landfill structure according to claim 1, wherein the clinker is pulverized to at least a particle size of 5 mm.   The particle size distribution of the ferronickel slag sand is such that the passing mass percentage is 10-30% when the particle size is 0.15 mm, 25-60% when the particle size is 0.3 mm, 60-90% when the particle size is 0.6 mm, and 1 particle size. The waste landfill structure according to claim 1 or 2, wherein 2 mm is constituted by 85 to 100%.   The waste landfill structure according to any one of claims 1 to 3, wherein the pulverized ferronickel slag sand is put into a water tank to float and separate fine powder.   The ferronickel slag clinker made by reducing and refining nickel ore with a reducing agent at high temperature was crushed to form a fracture surface with water retention on the particle surface, fine powder was floated and separated to adjust the particle size and have water permeability Slag sand for fine-grained layers with a waste landfill structure. Reducing and refining nickel ore with reducing agent at high temperature,
Crush the resulting clinker to form a fracture surface on the grain surface,
A method for producing slag sand for a fine-grained layer of a waste landfill structure, characterized in that crushed ferronickel slag sand is put into a water tank and fine particles are removed by floating separation means to adjust the particle size.

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