JPH08199166A - Method for producing soil solidifying agent - Google Patents

Abstract

(57) [Summary] (Correction) [Purpose] Waste limestone used for desulfurization of combustion exhaust gas generated by burning fuel containing sulfur is effectively reused as a resource to produce a soil solidifying agent. [Structure] Scrap limestone used for desulfurization of combustion exhaust gas generated by burning a fuel containing sulfur in a combustion device is crushed, and crushed waste limestone is mixed with cement clinker and gypsum to produce a soil improvement agent. . In the manufacturing method, the combustion apparatus is a fluidized bed boiler 10 having a fluidized bed combustion bed 13 for burning fuel and a fluidized bed desulfurization bed 17 for desulfurizing exhaust gas on the downstream side of the combustion exhaust gas, and the fuel is industrial waste or the industrial waste or A solid fuel obtained by mixing and compression molding mainly industrial waste,
Waste limestone is used as waste limestone discharged from the fluidized bed desulfurization bed 17 of the fluidized bed boiler 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a soil-solidifying agent for soil-solidifying soft ground such as sludge dredging sites and landfills.

[0002]

2. Description of the Related Art Conventionally, soil solidifying agents are manufactured by mixing gypsum (CaSO ₄ ), quick lime (CaO), and cement clinker. On the other hand, in a fluidized bed boiler as a combustor, for example, when industrial waste, oil coke, coal, oil or the like is used as a fuel containing sulfur as a fuel, the fuel is used in the fluidized bed combustion bed provided in the lower stage. Is burned, and the combustion exhaust gas is desulfurized by using limestone in a fluidized bed desulfurization bed provided on the upper stage of the fluidized bed combustion bed through a gas dispersion plate to remove sulfur oxides in the exhaust gas. The limestone that has been subjected to this desulfurization, so-called waste limestone, may be disposed of as waste or reused, and the case disposed of as waste is considered to be final disposal, and as a reuse case, For example, it is mixed with cement raw material and used as a calcium raw material.

[0003]

When the final disposal of waste limestone as waste, it is desirable to reuse the waste limestone as a resource in view of the current problem that the absolute amount of the disposal site is insufficient. Be done. On the other hand, in the cement industry, when the waste limestone is reused as a calcium raw material in the process of manufacturing cement or cement-related products, it is necessary to collect the waste limestone, such as transportation costs, and to dispose of it. It is a fact that the percentage of the above is not necessarily negligible.

The present invention has been made in view of the above problems, and pays attention to a soil solidifying agent used for improving soft ground as a commercialized product with increased added value, and a fuel containing sulfur in a combustion device. It is intended to provide a method for producing a soil solidifying agent by effectively utilizing waste limestone used for desulfurization of combustion exhaust gas generated by burning methane as a raw material of the soil solidifying agent and reusing it as a resource.

[0005]

In order to achieve the above object, the method for producing a soil-solidifying agent of the present invention comprises:

(1) Soil limestone used for desulfurization of combustion exhaust gas generated by burning a fuel containing sulfur in a combustion device is crushed, and the crushed waste limestone is mixed with cement clinker and gypsum to improve soil quality. It is characterized by producing an agent.

(2) In the manufacturing method of (1), the combustion device has a fluidized bed combustion bed for burning fuel and a fluidized bed desulfurization bed for desulfurizing the exhaust gas downstream of the combustion exhaust gas. A fluidized bed combustion furnace, the fuel is industrial waste or a solid fuel obtained by mixing and compression molding mainly with the industrial waste, and the waste limestone is discharged from the fluidized bed desulfurization bed of the fluidized bed combustion furnace. It is characterized by being abandoned limestone.

[0008]

[Function] When the waste limestone after desulfurization is analyzed, as shown in FIG. 2, gypsum (CaSO ₄ ) is in the surface layer, quick lime (CaO) is in the middle layer, and the uncalcined part is in the center. It has calcium carbonate (CaCO ₃ ). The particle size is, for example, about 3 mm when discharged from the desulfurization bed of a fluidized bed boiler as a combustor, but the particle size is 1 mm or less, optimally 0.5 mm or less by a crusher or crusher such as a hammer crusher. Grind to diameter. As shown in Fig. 3 by this crushing, two-component gypsum (CaSO ₄ ) and quick lime (CaO), which are required as soil solidifying agents at once, are obtained.
Appears on the surface of abandoned limestone. Therefore, gypsum (CaSO ₄ ) and quick lime (CaO), and cement clinker are necessary for the production of the soil solidifying agent, and the crushed waste limestone is used as a component necessary for the production of the soil solidifying agent, or The waste limestone, which is a waste, can be made into a high-value-added recycled product by using it as a supplement for the component.

As the waste limestone, for example, a fluidized bed combustion furnace is used as a combustion device, and an industrial waste such as waste plastics or an industrial waste such as coal ash or waste plastics is a main component as a fuel containing sulfur. As a solid fuel obtained by compression molding with addition of water or waste oil, or a fuel such as oil coke, coal, oil, etc., is burned in the lower fluidized bed combustion bed, and this combustion exhaust gas is the next upper fluidized bed. It is used as waste limestone after flowing into the desulfurization bed and using particles of limestone with a particle size of, for example, 3 mm or less in the desulfurization bed as a desulfurizing agent to remove sulfur oxides such as sulfur dioxide in combustion exhaust gas. To be

In particular, the combustion apparatus is a fluidized bed combustion furnace such as a fluidized bed boiler, and as a fuel containing sulfur, industrial waste such as waste plastics, or combustion ash such as coal ash and industrial wastes such as waste plastics. Using pelletized solid fuel obtained by mixing waste oil and water as industrial waste and compressing it, and burning it in the combustion bed of a fluidized bed boiler to incinerate it. When the waste limestone after being subjected to desulfurization of the combustion exhaust gas generated by the combustion in the desulfurization bed downstream of the combustion bed is used, the waste is effectively used as an industrial waste thermal recycling system and By recycling the waste limestone discharged from the system, it becomes useful as a total recycling system for industrial waste.

By using a fluidized bed combustion furnace as the combustion apparatus in the above, efficient combustion can be performed even if the fuel is waste having various shapes, and a low NO _X (low nitrogen oxide) operation is possible. It is possible to perform combustion with low pollution, and even if the fuel contains water, it can be burned in the combustion bed as it is without any special dehydration treatment. Is advantageous to.

[0012]

EXAMPLE FIG. 1 is a diagram showing a schematic structure of an apparatus for producing a soil solidifying agent attached to a fluidized bed combustion furnace applied to the method for producing a soil solidifying agent of the present invention, and FIG. 2 is for burning a fuel containing sulfur. FIG. 3 is a diagram showing a state before crushing, which is an enlarged view of a distribution state of components inside the waste limestone particles used for desulfurization of combustion exhaust gas that occurs at a time, and FIG. 3 is a state after crushing the waste limestone in FIG. FIG. 4 is an enlarged view showing the relationship between the addition amount of the soil solidifying agent produced by using the crushed waste limestone of the present invention to the soil and the uniaxial compressive strength of the soil to which the soil solidifying agent is added. FIG. 6 is a graph showing a comparison with a soil solidifying agent manufactured using waste limestone that is not ground.

First, an apparatus for producing a soil solidifying agent attached to a fluidized bed combustion furnace applied to the method for producing a soil solidifying agent of the present invention will be described. In FIG. 1, 10 is a fluidized bed boiler as a fluidized bed combustion furnace, the fluidized bed boiler 10 is provided with an air chamber 11 at the lowermost stage, and a combustion chamber 12 is provided above the air chamber 11 via an air dispersion plate. Further, a desulfurization chamber 16 is provided on the upper part of the chamber through a gas dispersion plate. A waste supply pipe 1 as a fuel supply pipe in the combustion chamber 12
5, a heat transfer tube (water tube) 14 is installed inside. Although not shown, the heat transfer pipe 14 is connected to a steam separator by water supply and return pipes. Heat transfer tube 1
No. 4 is heated by contact with a high temperature fluidized bed combustion bed and the water flowing inside is heated to generate steam.

A limestone supply pipe 18 for supplying limestone as a desulfurizing agent is provided in the desulfurization chamber 16, and a waste limestone discharge pipe 20 for discharging the waste limestone used for desulfurization on a side wall opposite to the limestone supply pipe 18.
Is installed. An exhaust gas discharge port 19 is formed in the upper part of the desulfurization chamber 16. Although not shown, an exhaust gas waste heat recovery device such as an exhaust heat boiler and an air preheater and a dust collector are sequentially installed downstream of the exhaust gas discharge port 19 via an exhaust gas duct.

On the other hand, a waste limestone cooler 30 around which a water cooling jacket is attached is attached to the end of the waste limestone discharge pipe 20, and a waste limestone hopper 40 is installed downstream thereof via a transportation pipe. . A crusher 4 consisting of a hammer crusher is attached to the lower discharge port of the waste limestone hopper 40 through a pipe having a rotary feeder 41 for cutting out the waste limestone.
2 is installed, and a sieving machine 43, which is an oscillating screen, is installed downstream of it via a transport pipe. A pipe for returning the oversized particles to the waste limestone hopper 40 is attached to the particle discharge side of the sieving machine 43, and a hopper 43a for temporarily storing the undersized particles is attached to the lower part thereof, and the hopper 43a is mixed with the hopper 43a. A transport pipe with a metering feeder 44 for feeding to the machine 70 is attached. Mixer 70
Consists of a paddle mixer. A rotary valve or a screw feeder is used as the quantitative feeder 44. Further, a gypsum hopper 50 and a cement clinker hopper 60 are installed alongside the waste limestone hopper 40,
Between the lower discharge ports of the respective hoppers and the mixer 70, transport pipes having the same fixed amount feeders 62 and 61 as described above are attached.

In the soil solidifying agent manufacturing apparatus attached to the fluidized bed combustion furnace having the above-mentioned structure, the fluidized medium such as sand is fluidized by the high temperature air supplied from the air chamber 11 in the combustion chamber 12 of the fluidized bed boiler 10. Temperature is 800-900
A fluidized bed combustion bed 13 at a high temperature of ° C is formed. Waste materials such as waste plastics as a fuel containing sulfur from the waste supply pipe 15 or a fuel as a fuel to a combustion furnace can be smoothly and easily supplied, and a combustion speed, a calorific value, and a combustion temperature can be set. In order to make it suitable as a fuel, and to prevent the melt sticking to the furnace wall of the combustion furnace and the obstruction of the fluidization of the fluidized medium, the main components are waste coal ash and waste plastics. The solid fuel formed by adding water and waste oil to the mixture and compression-molding the mixture to form a pellet-shaped compression-molded body is burned and incinerated.

On the other hand, in the upper desulfurization chamber 16, limestone particles as a desulfurizing agent having a particle size of 3 mm or less are continuously supplied from a limestone supply pipe 18, and the limestone is blown up through a gas dispersion plate to a combustion bed 13 of the combustion chamber 12. 800 emitted from
The fluidized bed desulfurization bed 17 is fluidized by the combustion exhaust gas at ˜900 ° C. By fluidizing the fluidized bed desulfurization bed 17, sulfur oxides such as sulfur dioxide in the combustion exhaust gas are desulfurized by the limestone particles and removed. In the desulfurization bed 17, limestone (CaCO ₃ ) is calcined (decarbonated) by the high-temperature exhaust gas at the above temperature to produce quicklime (CaO), and this quicklime acts as an adsorbent for sulfur oxides. The desulfurized combustion exhaust gas is led out of the furnace from the exhaust gas discharge port 19 at the upper part of the desulfurization chamber 16 and passed through an exhaust heat boiler, an air preheater and a dust collector (not shown) to absorb and collect residual heat of the exhaust gas. Receives dust effect. The steam obtained by the heat transfer tube 14 or the exhaust heat boiler is taken out by the steam separator,
By driving the steam turbine to drive the generator,
Recovered as electrical energy.

From the desulfurization chamber 16, the high temperature waste limestone particles (particle size of 3 mm or less) used for the desulfurization are taken out of the furnace through the discharge pipe 20 and sent to the waste limestone cooler 30 where they are cooled to a predetermined temperature. To be done. Then, the waste limestone is stored in the waste limestone hopper 40. Then, the waste limestone stored in the waste limestone hopper 40 is cut out from the hopper 40 by the rotary feeder 42 and put into the crusher 42 to be crushed. The crushed waste limestone is put into a sieving machine 43, and particles having a particle size of 0.5 mm or less pass through the screen and are stored in a temporary storage hopper 43a below the sieving machine 43. 0.5 mm particle size
The above particles are returned to the waste limestone hopper 40 and used again for grinding.

However, the gypsum hopper 50 and the cement clinker hopper 60 respectively store gypsum [grain size of about 3000 branes (cm ² / g)] and cement clinker [grain size of about 3000 branes (cm ² / g)]. . Then, from the temporary storage hopper 43a of the waste limestone, the gypsum hopper 50, and the cement clinker hopper 60, waste limestone is provided in predetermined proportions by quantitative feeders 44, 62, 61, respectively.
Gypsum and cement clinker are taken out and the mixer 70
Is supplied to. The ratio of the raw materials supplied to the mixer 70 is, for example, 20 to 50% by weight of waste limestone and 10 to 20 of gypsum.
% By weight, and 40-60% by weight of cement clinker.
The soil solidifying agent is obtained by supplying the respective raw materials to the mixer 70 in such a ratio and mixing them. In addition,
Waste limestone with a particle size of 0.5 mm or less is optimal, but
It is also possible to use one having a size of 1 mm or less.

As the soil solidifying agent, gypsum (CaSO ₄ ), quick lime (CaO) and cement clinker are required as mentioned above, but in the present invention, quick lime (CaO) content is waste limestone, gypsum and cement clinker. It can be compensated by setting the mixing ratio as follows, and quick lime does not need to be prepared separately.

Thus, the limestone particles to be desulfurized in the desulfurization chamber 16 take in a sulfur oxide such as sulfurous acid gas in the form of gypsum to perform a desulfurization action. As shown in Fig. 2, waste limestone has gypsum (CaSO ₄ ) in the surface layer, and calcium carbonate in the uncalcined portion in the center.
The interior except for (CaCO ₃ ) is in the state of quick lime (CaO), and by crushing or crushing this with a crusher 42, as shown in FIG. (CaSO ₄ ) and quicklime (CaO) appear on the surface of waste limestone. Gypsum (CaSO ₄ ), quicklime as ingredients of soil solidifying agent
(CaO) and a cement clinker are required, but the crushed waste limestone is added as a component necessary for the production of a soil-solidifying agent, or by adding the waste limestone as a waste. It can be a high-value reuse product.

In the soil solidifying agent manufacturing apparatus attached to the fluidized bed combustion furnace of this embodiment, the combustion of coal ash and the like collected by the dust collector installed downstream of the exhaust gas of the fluidized bed boiler 10 is carried out. Ash is also reused as a component for producing a solid fuel that is put into the fluidized bed boiler as a fuel.

Further, in the soil solidifying agent manufacturing apparatus attached to the fluidized bed combustion furnace of this embodiment, the fluidized bed combustion furnace as the combustion apparatus is the fluidized bed boiler 10, and waste plastics etc. are used as fuel containing sulfur. Industrial waste, or combustion ash such as coal ash, industrial waste such as waste plastics, etc. are mainly mixed with waste oil and water as industrial waste, and pelletized solid fuel obtained by compression molding is obtained. It is used, and it is burned and incinerated in the combustion bed 13 of the fluidized bed boiler 10 to obtain steam in the heat transfer tube 14, and the desulfurization chamber 16 downstream of the combustion bed is used.
Since the waste limestone after being subjected to the desulfurization of the combustion exhaust gas generated by the combustion is used in the desulfurization bed 17 of the above, the waste is effectively used as the industrial waste thermal recycling system, and further discharged from the system. By recycling the waste limestone thus produced, it is said to be useful as a total recycling system for industrial waste.

Further, since the combustor is the fluidized bed boiler 10 which is a fluidized bed type combustion furnace, efficient combustion can be performed even if the waste as fuel has various shapes. Low NO _X operation can be performed, and low pollution combustion can be performed. Further, even if the waste contains a relatively large amount of water, it can be burned in the combustion bed 13 as it is without requiring a dehydration treatment, which is advantageous for combustion using waste containing sulfur as a fuel. Has been done.

In the above embodiments, wastes such as waste plastics are used as fuel containing sulfur, or coal ash and waste plastics, which are the wastes, are the main components, and water and waste oil are added and mixed. The case of applying the waste limestone obtained by desulfurizing the exhaust gas by burning the solid fuel as the pellet-shaped compression molded body obtained by compression molding has been described, of course, as a fuel containing sulfur, oil coke, coal, Waste limestone used for desulfurization of exhaust gas obtained by burning oil such as heavy oil can also be applied.

Next, an example of the production of the soil solidifying agent performed by using the pilot plant of the soil solidifying agent producing apparatus attached to the fluidized bed combustion furnace shown in the embodiment of FIG. 1 will be described. When oil coke was supplied from the fuel supply pipe 15 to the combustion chamber 12 of the fluidized bed boiler as a fuel containing sulfur at a rate of 270 Kg / h and burned, 165 Kg / h of limestone as a desulfurizing agent was supplied to the desulfurization chamber 17. 65Kg of waste limestone obtained by supplying
Soil solidifying agent was made by crushing / h. For comparison, a soil solidifying agent was prepared using waste limestone that was not crushed at the same time. In both cases, the mixing ratio of cement clinker, gypsum and waste limestone in the soil solidifying agent should be the same, the particle size of cement clinker and gypsum should be about 3000 branes, and the crushed waste limestone should be 0.5 mm or less. The waste limestone that was not crushed was 3 mm or less. The mixing ratio of each component in this soil solidifying agent is as shown in Table 1.
In Table 1, the mixing ratio of the solidifying agent produced by using the crushed waste limestone of the present invention is shown as an example, and the mixing ratio of the solidifying agent produced by using the uncrushed waste limestone is shown as a comparative example.

[0027]

[Table 1]

Then, the soil solidifying agent according to the present invention prepared by using the crushed waste limestone in the mixing ratio shown in the Example column of Table 1 and the non-crushed waste limestone are used in the comparative example column of Table 1. The graph of FIG. 4 shows the solidification performance with the soil solidifying agent prepared with the indicated blending ratio. This solidification performance was taken as a soil sample with both soil solidification agents Location: Ariake Town, Saga Prefecture,
Soil classification: fine soil, natural water content: 97 to 147%, wet density: 1.24 to 1.47 t / m ^3, dry density: was used in 0.5 ~0.62 t / m ^3. FIG. 4 shows the relationship between the ratio (%) of the amount of the soil solidifying agent added to the soil sample and the uniaxial compressive strength (Kgf / cm ² ) of the soil solidifying agent-added soil sample. The soil solidifying agent produced by using limestone (shown by a solid line) and the soil solidifying agent produced by using uncrushed waste limestone (shown by a chain line) are shown for comparison.

As is apparent from the graph of FIG. 4, the soil solidifying agent produced using the crushed waste limestone of the present invention has a soil solidifying strength that is higher than that of the soil solidifying agent produced using uncrushed waste limestone. It can be seen that is about 3 times higher. When waste limestone is mixed with gypsum and cement clinker without crushing, quick lime is surrounded by gypsum and hydration reactivity is low.When crushing, quick lime and gypsum are exposed on the surface of the crushed particles. Therefore, it is considered that the hydration reactivity is extremely good.

[0030]

As is apparent from the above description, the present invention has the following excellent effects. In the configuration of claim 1, by crushing or crushing waste limestone, two types of components, gypsum, quicklime, gypsum among cement clinker and quicklime, which are necessary as components of the soil solidifying agent, are exposed on the surface,
This can be effectively used as a component of the soil solidifying agent or as a component supplement, and waste limestone as a waste can be effectively used to obtain a soil solidifying agent capable of resource saving.

According to the second aspect of the present invention, the combustor is a fluidized bed combustion furnace such as a fluidized bed boiler, and industrial waste such as waste plastics is used as a fuel containing sulfur, or combustion ash such as coal ash or waste plastics. The solid fuel in the form of pellets, which is mainly composed of industrial waste such as, is mixed with waste oil and water as industrial waste and is compression-molded, and burns and incinerates it in the combustion bed of a fluidized bed boiler. Industrial waste thermal recycling that uses industrial waste as fuel (heat source) by obtaining steam and using waste limestone after desulfurization of combustion exhaust gas generated by the combustion in the desulfurization bed downstream of the combustion bed By making it possible to effectively utilize the waste as a system, that is, as an industrial waste heat recovery device, and further to make it possible to recycle the waste limestone discharged from the system. It can be made extremely effective as a total recycling system of industrial waste.

Also, by using a fluidized bed combustion furnace as the combustion apparatus in the above, efficient combustion can be performed even if the fuel is waste having various shapes, and low NO _X
It is possible to operate, it is possible to perform low-pollution operation, and further, even if the fuel contains water, it is possible to burn as it is in the combustion bed without requiring dehydration treatment, It is advantageous for combustion using waste containing sulfur as a fuel.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of an apparatus for producing a soil solidifying agent attached to a fluidized bed combustion furnace applied to a method for producing a soil solidifying agent of the present invention.

FIG. 2 is a diagram showing a state before crushing, which shows an enlarged distribution state of components inside waste limestone particles used for desulfurization of combustion exhaust gas generated when a fuel containing sulfur is burned.

FIG. 3 is an enlarged view showing a state after crushing the waste limestone of FIG.

FIG. 4 shows the relationship between the amount of soil solidifying agent produced by using the crushed waste limestone of the present invention added to soil and the uniaxial compressive strength of the soil to which the soil solidifying agent is added. It is the graph shown in comparison with the soil solidification agent manufactured by.

[Explanation of symbols]

10 Fluidized Bed Boiler (Fluidized Bed Combustion Furnace) 11 Air Chamber 12 Combustion Chamber 13 Fluidized Bed Combustion Bed 14 Heat Transfer Tube (Water Tube) 16 Desulfurization Chamber 17 Fluidized Bed Desulfurization Bed 20 Waste Limestone Hopper 42 Crusher [Crusher (Hammark crusher) 43 Sieve machine (vibrating sieve) 50 Gypsum hopper 60 Cement clinker hopper 70 Mixer (paddle mixer)

Claims (2)

[Claims] 1. A soil improvement agent by crushing waste limestone used for desulfurization of combustion exhaust gas generated by burning a fuel containing sulfur in a combustion device, and mixing the crushed waste limestone with cement clinker and gypsum. A method for producing a soil improvement agent, which comprises: 2. The combustion apparatus is a fluidized bed combustion furnace having a fluidized bed combustion bed for burning fuel, and a fluidized bed desulfurization bed for desulfurizing the exhaust gas downstream of the combustion exhaust gas, wherein the fuel is industrial. A solid fuel obtained by mixing and molding waste or industrial waste as a main component, wherein the waste limestone is waste limestone discharged from the fluidized bed desulfurization bed of the fluidized bed combustion furnace. Item 2. A method for producing a soil conditioner according to item 1.