KR100402543B1 - Burning method of waste by circulating fluidized bed - Google Patents

Abstract

PURPOSE: A burning method of waste by a circulating fluidized bed is provided to remove the necessity of a pretreatment process for removing moisture and alkali components by preventing agglomeration caused by chemical reaction of the alkali components among sludge. CONSTITUTION: A burning method of waste by a circulating fluidized bed comprises steps of adjusting the temperature of bed materials within a range from 850 to 900 degrees centigrade; adjusting the flowing speed of the bed materials to 6 ¯ 7 m/s; including kaolin in fluidized bed materials(6a) generating reactant having a fusion point higher than the temperature of the fluidized bed materials by reacting to components included in waste.

Description

Burning method of waste by circulating fluidized bed

The present invention relates to a waste incineration method by a fluidized bed, and more particularly, to a waste incineration method that can effectively prevent the aggregation of the layer material by the material contained in the sludge.

In general, a variety of sludge incineration methods are used, such as a bubbling fluidized bed combustion technique using sand, that is, Si0 ₂ , and a circulating fluidized bed combustion technique.

1 is a schematic configuration diagram of a bubble fluidized bed combustion furnace, and FIG. 2 is a schematic configuration diagram of a circulating fluidized bed combustion furnace. Referring to FIG. 1, the bubble fluidized bed combustion furnace 1 has a lower cavity in which air from a combustion air supply device 5 is injected into a lower portion of a combustion chamber 7, and a fluidized bed material 6 is placed thereon. A flowing combustion chamber 7 is located. On the side wall of the combustion chamber 7, a line 4 for supplying the coal / limestone mixture and a line 3 for supplying the sludge alone are disposed so that sludge, limestone and coal are supplied into the combustion furnace. In the case of the bubble fluidized bed combustion furnace, the fluidized bed material 6 has a temperature of 850 to 900 ° C., and the flow rate of the fluidized bed material 6 in the combustion chamber 7 is 0.5 to 2 m / by air supplied from the air supply device 5. adjusted to s.

Referring to FIG. 2, the circulating fluidized bed combustion furnace 1a is provided with a lower cavity in which air from the combustion air supply device 5a is injected into the lower portion of the combustion chamber 7a, and the fluidized bed material 6a is placed thereon. Flowing combustion chamber 7a is located. On the side wall of the combustion chamber 7a, a line 4a for supplying the coal / limestone mixture and a line 3a for supplying the sludge alone are provided to supply the combustion furnace, sludge and coal. On one side of the combustion chamber 7a is a cyclone 8 which recovers waste heat from the exhaust gas and circulates the fluidized bed material.

In the fluidized bed combustion technique described above, a problem is agglomeration of bed materials due to the generation of by-products having a melting point lower than the temperature in the furnace. This agglomeration is caused by agglomeration of the layer material in the molten state of by-products having a low melting point. This agglomeration phenomenon is more severe in the case of a bubble fluidized bed with a relatively low fluidized bed flow rate. The low flow rate results in a low combustion efficiency for high water content sludge with a water content of 85% or more, and in particular, sludge incineration containing a large amount of alkaline components. Remelting material by alkali component containing Na element is generated and the layer material is agglomerated, thus impairing fluidization.

Scheme 1 and Scheme 2 below are chemical reactions in the fluidized bed that causes aggregation.

_{Na 2 SO 4 + SiO 2 →} Na 2 .3SiO 2 + 1/2 O 2

3SiO _{2 +} 2NaCl + H ₂ O → Na ₂ . 3SiO ₂ + 2HCl

Scheme 1 above sikineunde the alkali component is generated for Na ₂ .3SiO ₂ and O ₂ as a by-product reacts with the SiO ₂ component in the material layer after combustion as if the alkaline components Na ₂ SO ₄ is present in the sludge, the Na _Since the melting point of ₂ · 3SiO ₂ is 635 ° C., the temperature of the fluidized bed is 850 to 900 ° C., Na ₂ · 3SiO ₂ reacts with the layer material in a molten state to agglomerate the layer material. In addition, in the case of Reaction Scheme 2, NaCl is present, and Na _{2. 3} SiO ₂ is generated together with HCl at this time, which also causes aggregation as described above. This flocculation occurs in both the circulating fluidized bed and the bubble fluidized bed. If the flocculant accumulates in the bed material at a certain concentration, the operation of the incinerator should be stopped. In order to solve this problem, conventionally, the sludge pretreatment step removes the water in the sludge and first removes the alkali component.

It is an object of the present invention to provide a waste incineration method which does not need to undergo a separate treatment to prevent agglomeration by chemical reaction of alkali components in the sludge and separate water removal and alkali components.

1 is a schematic configuration diagram of a general bubble fluidized bed incinerator,

2 is a schematic structural diagram of a general circulating fluidized bed incinerator.

In order to achieve the above object, the waste incineration method of the present invention is a method of incinerating waste by bed material flowing in a combustion furnace at a predetermined temperature and a predetermined fluidization rate, wherein the flow rate of the bed material is 6 to 7 m. adjusting to / s; Adding kaolin to react with a predetermined component contained in the waste to produce a reactant having a melting point higher than the temperature of the fluidized bed material.

The present invention is to maximize the combustion efficiency by increasing the fluidization rate and to react the by-products having a melting point higher than the temperature of the layer material by reacting with a predetermined component, for example, an alkaline component in the waste to the layer material maintaining a predetermined temperature, By-products are present in the solid phase without being melted in the layered material so that they can be recovered and are not limited to any particular alkali material and are generally known as any material capable of producing a high melting point solid material. It is possible.

Hereinafter, an embodiment of a waste incineration method according to the present invention will be described.

Incinerators to which the incineration method of the present invention can be applied are conventional bubble-type fluidized bed incinerators and circulating fluidized bed incinerators, and thus description of the entire process of incineration is not mentioned in this embodiment.

The temperature in the combustion chamber is maintained at 850-900 ° C. and the fluidization rate of the fluidized bed is maintained at 6-7 m / s as in a typical fluidized bed incinerator.

<Example 1>

When the sludge which is a waste contains a large amount of Na ₂ SO ₄ component, an additive having a component of SiO ₂ , Al ₂ O ₃ , TiO ₂ is added to the fluidized bed material as a feature of the present invention. For example, when using Al ₂ O ₃ as an additive, the reaction scheme in the incinerator is as follows.

Na ₂ SO ₄ is first reacted with sand, that is, SiO ₂ , as shown in Scheme 3 below.

_{Na 2 SO 4 + 3SiO 2 →} Na 2 O · 3SiO 2 + SO 2 + 1/2 O 2

This followed the Na ₂ O · 3SiO ₂ reacts as 3SiO ₂ and Al ₂ O ₃ and scheme 4 below.

_{Na 2 O · 3SiO 2 + Al} 2 O 3 + 3SiO 2 → Na 2 O · Al 2 O 3 · 6SiO 2

Finally obtained as in the above reaction formula _{4 Na 2 O · Al 2 O} 3 · 6SiO ₂ and is formed aka sodium silicate.

Since the sodium silicate has a melting temperature of 1117 DEG C, which is higher than the combustion temperature, once formed, the sodium silicate does not melt but is mixed with the layer material in a solid phase.

<Example 2>

When the waste sludge contains a large amount of NaCl component, an additive having a component of SiO ₂ , Al ₂ O ₃ , TiO ₂ is added to the fluidized bed material as a feature of the present invention.

For example, when using Al ₂ O ₃ as an additive, the reaction scheme in the incinerator is as follows.

First, NaCl reacts with SiO ₂ and H ₂ O as in Scheme 5 below.

2NaCl + 3SiO ₂ + H ₂ O → Na ₂ · 3SiO ₂ + 2HCl

Subsequently, Na ₂ · ₃ SiO ₄ reacts with SiO ₂ and Al ₂ O ₃ as in Scheme 6 below.

_{Na 2 O · 3SiO 2 + Al} 2 O 3 + 3SiO 2 → Na 2 O · Al 2 O 3 · 6SiO 2

Finally obtained as shown in Scheme 6 above, _{Na 2 O · Al 2 O 3} · 6SiO ₂ and is formed aka sodium silicate.

As described above, since the sodium silicate has a melting temperature of 1117 ° C., which is higher than the combustion temperature, once formed, the sodium silicate is not melted but mixed with the layer material in a solid phase.

As in the embodiments described above, the present invention is characterized in that the final product obtained by the alkaline component when burning the sludge having an alkali component has a property that the melting temperature is higher than the temperature in the combustion furnace. The fluidization rate of the layered material is controlled to 6 to 7 m / s, so that the solid end product existing in the layered material, the layered material and air flow at a higher speed, so that the mixing / disturbance with the air is more smooth and localized. Heat concentration is prevented. In addition, it is preferable to use crushed granite instead of sand as the layered material in suppressing aggregation between other products and the layered material. Particularly, the additive contains evenly the components of SiO ₂ , Al ₂ O ₃ , and TiO ₂ . It is preferable to use kaolin.

As described above, according to the present invention, by incineration of a substance capable of forming aggregates in a combustion furnace in a layer material having a flow rate of 6 to 7 m / s while using a substance which is not combined with the aggregate as an additive, It is possible to omit the cumbersome and expensive pretreatment process as in the prior art. Based on the concept of the present invention, it is possible to treat not only sodium-based alkaline materials as described above, but also alkaline-based materials of other systems, thereby effectively treating by-products in the sludge dyeing process.

Claims (3)

CLAIMS 1. A method for incinerating waste by bed material flowing at a predetermined temperature and at a predetermined fluidization rate, said method comprising the steps of: adjusting the temperature of said bed material in the range of 850 to 900 &lt; 0 &gt;C; Adjusting the flow rate of the layer material to 6 to 7 m / s; Including kaolin in the fluidized bed material that reacts with components contained in the waste to the bed material to produce a reactant having a melting point higher than the temperature of the fluidized bed material; Waste incineration method by a fluidized bed comprising a. The waste incineration method according to claim 1, wherein the waste contains Na ₂ SO ₄ and the reactant contains Na ₂ O · Al ₂ O ₃ · 6SiO ₂ . The waste incineration method according to claim 2, wherein the waste contains NaCl and the reactant contains Na ₂ O. Al ₂ O ₃ · 6 SiO ₂ .

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