WO1999051917A1

WO1999051917A1 - Circulating fluidized bed

Info

Publication number: WO1999051917A1
Application number: PCT/JP1999/001663
Authority: WO
Inventors: Kanichi Ito
Original assignee: Ebara Corporation
Priority date: 1998-03-31
Filing date: 1999-03-31
Publication date: 1999-10-14
Also published as: JP3497822B2; AU3053899A

Abstract

A circulating fluidized bed for heat-treating solid waste such as of municipal waste and waste plastic. The circulating fluidized bed is of a loop type and is divided into fluidized beds (1, 2) partitioned at an intermediate portion by moving beds (9, 10) and having independent free boards (22, 25). In the circulating fluidized bed, a fluid medium is circulated by a driving force generated because of the difference in specific gravity between the moving beds (9, 10) and the fluidized beds (1, 2).

Description

Description Circulating fluidized bed Technical field

The present invention relates to a fluidized bed used for heat treatment of solid waste such as garbage and waste plastic. Background art

In the case of heat treatment of solid waste such as garbage and waste plastic, the present inventor has already published Japanese Patent Publication No. 62-350004 (Patent No. 1461775).

As described in detail in “Method and Apparatus for Combustion of Solids”, the combination of a pyrolysis gasification fluidized bed and a cyclone combustion and melting furnace is a reasonable method to compensate for the disadvantages of both, and is well known. In recent years, this method has been put into practical use as a “gasification and melting furnace”. However, the fluidized bed in a conventional gasification and melting furnace supplies the heat required for gasification (endothermic reaction) by the partial combustion of the raw material. Calories were reduced. On the other hand, in the cyclone combustion melting furnace, rapid high-temperature heating is indispensable for the function of melting ash at a high temperature and capturing it on the inner wall of the furnace by a strong swirling flow, but waste with low heat content and high moisture content is required. There was a problem that such rapid high-temperature heating was difficult with low-strength raw gas obtained from raw materials.

Moreover, in the cycle-opening combustion melting furnace, the temperature inside the furnace becomes as high as 130 to 140 ° C in order to melt and drop ash on the inner wall as described above. Heat dissipation · It is necessary to prevent heat loss, so the construction of the furnace wall is expensive. There was a title.

On the other hand, there is a well-known two-tower circulation type fluidized bed as a method to obtain high-strength port gas regardless of the calorific value of the raw material waste. 10 and 11 are views showing a conventional two-tower circulation type fluidized bed, wherein FIG. 10 is a schematic sectional view, and FIG. 11 is a view taken in the direction of arrow Z in FIG. As shown in Figs. 10 and 11, the two-column circulating fluidized bed is composed of a pyrolysis gasification fluidized bed 51 and a combustion fluidized bed 52 of the first class, which are connected by a pair of pipes 53, 54. In this method, the amount of heat required for pyrolysis is supplied by circulating the heat medium in two towers. The pyrolysis gas is taken out separately from the combustion exhaust gas. However, since the heat medium in the fluidized bed has a property that it is difficult to move in the horizontal direction, in this configuration, the heat medium is locally supplied by piping and tends to flow short-circuited as indicated by arrows 55 and 56. However, in order to cause a sufficient reaction in the fluidized bed, it was necessary to increase the height H of the fluidized bed, and there was a problem that not only the power loss of fluidization was increased but also the size of the apparatus was increased.

Furthermore, in the pyrolysis gasification of waste plastics containing vinyl chloride, etc., the generated HC1 is included in the pyrolysis gas. High temperature corrosion occurs due to HC 1 gas in the equipment. In order to prevent this, there was a problem that complicated pre-treatment was required, such as mechanical removal of vinyl chloride in advance or thermal decomposition separately after heating and melting to remove chlorine. Disclosure of the invention

The present invention solves the above-mentioned problems, that is, (1) a high calorie gas capable of rapidly heating a cycle-opening combustion melting furnace even with a low calorie and high moisture content refuse raw material can be obtained. (2) The construction of a cyclone combustion and melting furnace with a high furnace temperature does not require expensive furnace walls. There is no danger of short-circuiting in the circulation of the heat medium as in the two-tower circulation system described in (1), and the equipment is small and compact with small motive power. (4) Waste plastic raw materials containing vinyl chloride etc. The purpose is to obtain a gas applicable to the cycling furnace and to avoid high-temperature corrosion of HC1 by HC1 in various devices after the melting furnace.

In order to achieve the above object, the invention according to claim 1 comprises forming a fluidized bed in a loop shape, and separating the middle of the looped fluidized bed with a moving bed and having a plurality of independent free boards. It is characterized in that the fluidized medium is circulated using the specific gravity difference between the moving bed and the fluidized bed as the driving force.

According to a second aspect of the present invention, in the loop fluidized bed according to the first aspect, the fluidized bed is formed in an annular shape, and a cycle opening combustion melting is formed at the center of the annular fluidized bed. It is characterized by building a furnace.

The invention according to claim 3 is the annular fluidized bed according to claim 2, wherein the annular fluidized bed is partitioned by two moving beds to form a pyrolysis gasification fluidized bed and a combustion fluidized bed of a class. In addition, the generated pyrolysis gas is supplied to the cycle-port combustion melting furnace in the center.

The invention according to claim 4 is characterized in that, in the annular fluidized bed according to claim 2, a heat transfer tube is provided in the moving bed.

The invention according to claim 5 provides the annular fluidized bed according to claim 4, wherein the annular fluidized bed is partitioned by two moving beds to form a dechlorination fluidized bed and a pyrolysis gasification fluidized bed. It is characterized in that the generated pyrolysis gas is supplied to the central cyclone combustion melting furnace. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is an explanatory view of a system embodiment including a longitudinal sectional view of a circulating fluidized bed according to the present invention. The circulating fluidized bed body is a Y-Y sectional view common to FIGS. 2 and 3.

FIG. 2 is a circulating fluidized bed according to the third aspect of the present invention, and is a view as seen from the arrow P in FIG.

FIG. 3 is a circulating fluidized bed according to the third aspect of the present invention, and is a sectional view taken along line XX of FIG.

FIG. 4 is a development sectional view of R_R of FIG.

FIG. 5 is an explanatory view of another system embodiment including a vertical sectional view of the circulating fluidized bed of the present invention. The circulating fluidized bed main body is a Y-Y sectional view common to FIGS. 6 and 7. FIG. 6 is a circulating fluidized bed according to the fourth and fifth aspects of the present invention, and is a view as seen from the arrow P in FIG.

7 is a circulating fluidized bed according to the fourth and fifth aspects of the present invention, and is a cross-sectional view taken along line XX of FIG.

FIG. 8 is an R-R development sectional view of FIG.

FIG. 9 shows another embodiment of the gas dispersion plate and the gas chamber.

FIG. 10 is a longitudinal sectional view of a conventional two-column circulation type fluidized bed.

FIG. 11 is a view on arrow Z in FIG. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 to 9, the same reference numerals denote the same or corresponding parts. The first and third embodiments will be described with reference to FIGS. As shown in FIGS. 1 to 4, in the circulating fluidized bed of the present invention, the pyrolysis gasification fluidized bed 1 and the combustion fluidized bed 2 are formed in an annular shape by an outer cylinder wall 3 and an inner cylinder wall 4. The fluidized bed is partitioned by moving layers 9 and 10 composed of a partition 6 having an opening 5 at the upper end and a partition 8 having an opening 7 at the lower end. Lower gas chamber 1 1, When non-oxidizing gas 13 such as recirculated pyrolysis gas 13 and combustion air 14 are supplied to 12 respectively, fluidized medium (sand) is fluidized through gas dispersion plates 15 and 16 respectively. Then, a pyrolysis gasification fluidized bed 1 and a combustion fluidized bed 2 are formed. Here, the non-oxidizing gas refers to a gas containing no oxygen, such as recycle gas of the pyrolysis gases, refers to the this non-oxidizing gas containing no 0 ₂ (oxygen) combustion-supporting . The composition of the pyrolysis gas is CO (—carbon oxide), H ₂

(Hydrogen), C_〇 ₂ (carbon dioxide), CH (methane), and other flammable gases. Since the specific gravity of the fluidized beds 1 and 2 is lighter than that of the moving beds 9 and 10, this specific gravity difference becomes the driving force, and the fluidized medium (sand) is the pyrolysis gasification fluidized bed 1 → the upper opening 5 → Moving bed 9—opening at lower end 7 → combustion fluidized bed 2 → opening at upper end 5 → moving bed 10 → opening at lower end 7 → pyrolysis gasifier 1 That is, if the upper surface 17 of the fluidized bed is higher than the lower surface 18 of the opening 5 at the upper end, the fluid medium overflows and circulates automatically in the direction of arrow 19, and the circulation speed is the width B of the moving bed. If the width S of the opening at the lower end is sufficiently large, the flow rate is regulated by the overflow height Δ. In other words, the circulation speed can be controlled by adjusting the height H of the fluidized bed. When the refuse raw material supplied from the raw material supply device 20 is thermally decomposed in an oxygen-free state pyrolysis gasification fluidized bed 1 at about 500 to 700 ° C, the generated pyrolysis gas 21 becomes ash content. Along with the free-decomposition gas outlet 23 via the free board 22.Chars generated by the pyrolysis move to the combustion fluidized bed 2 together with the fluidized medium and burn, and the heating medium is heated and heated. This gives the amount of heat required for thermal decomposition (endothermic reaction). The flue gas 24 is taken out from the flue gas outlet 26 through the free board 25, but the two free boards 22 and 25 are separated by the partition walls 6 and 8 and the moving bed 9 and 10 and are independent. in, without pyrolysis gas 2 1 is diluted mixed up with the flue gas 2 4, the force opening Li one this good Una pyrolysis gas is about 5 0 ◦ 0 k C a 1 Z m 3 This has been experimentally confirmed to be reached. In the figure, reference numeral 27 denotes a double discharge valve for removing incombustible residue, and the removed incombustible residue is sieved and the fluid medium (sand) under the sieve is returned to the fluidized bed again.

Next, a second embodiment of the present invention will be described. The inner cylinder wall 4 of the annular fluidized bed is extended slightly upward, and the combustion gas 21 is formed on the upper part of the cylinder as shown in FIGS. The supply port 29 and the supply port 31 for the pressurized air 30 are provided tangentially, and an exhaust gas outlet 32 is provided at the center of the upper part.

Build 2 8 When swirling flow 33 is created by pressurized air 30 and pyrolysis gas 21 is burned at a high load and rapidly heated to 130 to 140 ° C, the ash melts and the After being caught by the inner wall and flowing down as a molten slag as shown by the dotted arrow 34, it is cooled in the water chamber 36 through the discharge port 35, and then the conveyor 37, the double discharge valve 38 is turned on. boiler 4 0 hot flue gas 3 9 of cyclone combustion melting furnace discharged from _c exhaust gas outlet 3 2 is taken out as a solid slug merges with flue gas 2 4 combustion fluidized bed (not shown) through The waste heat is recovered and used in the gas treatment facility, and is discharged outside through the gas treatment facility 41. In addition, as in the well-known Japanese Patent Publication No. 62-350004, the pyrolysis gas 21 is compressed air.

It is even better to supply in an ejector system by 30.

In the above embodiment, the fluidized bed is constructed in an annular shape. However, as is clear from the above description, in order to circulate the fluidized medium, the fluidized bed is not limited to an annular shape, but is formed into an elliptical annular shape. Any shape is acceptable. In the circulating fluidized bed configured as described above, the fluidized medium is extruded and moved in a "place-and-place" manner, so there is no risk of short-circuiting as in the conventional two-column circulating type, and the height H of the fluidized bed is reduced. At least, the reaction is sufficiently promoted in the fluidized bed. Therefore, the circulating fluidized bed is not limited to heat treatment of solid waste, but can be applied to cracking of heavy oil, for example. For the purpose of promoting the mixing of the raw material and the heat medium in the fluidized bed, for example, as shown in FIG. 9, the dispersion plate 15 is formed into a V-shape, and the gas chamber 11 is set to 1 1 — 1 to 1 1 — Divide as shown in 4 and supply to the outer gas chambers 1 1 1 1 and 1 1-4 Supply the gas pressure of the gas pipe 13-1 to the inner gas chambers 1 1-2 and 1 1-13 It is advisable to raise the gas pressure higher than the gas pressure of the gas pipe 13-2 to agitate the fluidized bed as shown by arrow 44.

Next, embodiments of claims 4 and 5 will be described with reference to FIGS.

In this configuration, the positions of the pyrolysis gasification fluidized bed 1 and the combustion fluidized bed 2 shown in Fig. 1 are replaced by a dechlorination fluidized bed 2A and a pyrolysis gasification fluidized bed 1, respectively. A heat exchanger 42 for cooling the fluidized medium is provided in the moving bed 9 after the pyrolysis gasification fluidized bed 1 to adjust the fluidized medium to an appropriate temperature of about 300 to 350 ° C for dechlorination. HC discharged from dechlorination fluidized bed 2 A 1 Rich gas 2

A gas cleaning device 43 for cleaning 4 A to remove H C 1 is provided. Air is supplied from the gas chamber 11 below the pyrolysis gasification fluidized bed 1 as fluidizing gas to perform pyrolysis at about 400 to 600 ° C by partial combustion. However, since the waste plastics as raw materials have a high calorific value, a high-strength port gas which can be sufficiently applied to the cycle-port combustion melting furnace 28 can be obtained. A part of the clean pyrolysis gas from the gas cleaning device 4 3 is recirculated and supplied as a fluidizing gas for the dechlorination fluidized bed 2 A from the gas chamber 12, and partial combustion as necessary At least, adjust to the appropriate temperature of 300 to 350 ° C for dechlorination.

The embodiments of claims 4 and 5 except for the above differences,

The mechanism that the fluid medium circulates in the direction of arrow 19 while 5 A is independent, the configuration and operation of the cyclone combustion melting furnace 28 and thereafter are all the same as those described in the embodiments of claims 1 to 3. The same is true. That is, waste plastic raw material including vinyl chloride is supplied from the raw material supply device 20 to the dechlorination fluidized bed 2A, The solids from which incombustibles have been removed from the double discharge valve 27 and from which chlorine has been removed are moved to the pyrolysis gasification fluidized bed 1 together with the fluidized medium and gasified. HC 1 rich gas 24 A discharged from the gas outlet 26 A of the dechlorination fluidized bed 2 A is purified by the gas cleaning device 43, then combined with the pyrolysis gas 21, and then supplied from the supply port 29. Supplied to cyclone combustion melting furnace 28.

Conventional dechlorination of waste plastics has been carried out by melting at 300 to 350 ° C as the optimum temperature for minimizing thermal decomposition as much as possible and enabling dechlorination. However, it was not easy to uniformly heat to a suitable temperature in a short time because the molten plastic had poor heat conduction. In this method, uniform heating of the plastic is facilitated by the fact that the molten plastic adheres thinly to the fluid medium (sand) and the specific surface area becomes extremely large, and the material crushing action peculiar to the fluidized bed and the stirring effect are combined. Therefore, chlorine is released in a relatively short time, in other words, the size of the apparatus can be reduced. In the dechlorinated fluidized bed 2A, a small amount of pyrolysis gas is generated in addition to HC1, but is combined with the pyrolysis gas 21 after gas cleaning and supplied to the cycle-port combustion melting furnace 28. It does not become.

As described above, according to the first aspect of the present invention, a plurality of fluidized beds having independent free boards are formed in a loop shape, and the fluidized medium is extruded in a "roll-to-roll type" so that each fluidized bed is extruded. Because the bed is circulated, there is no danger of short-circuiting and circulation as in the conventional two-column circulation system.If the height of the fluidized bed is reduced, the reaction is sufficiently promoted and the fluidization power is reduced. The equipment can be made compact.

According to the second aspect of the present invention, the cyclone combustion melting furnace is provided at the center of the annular fluidized bed and the outside is surrounded by the fluidized bed. Heat radiation from walls · No need for expensive furnace walls to prevent heat loss. According to the third aspect of the present invention, since the pyrolysis gas is not diluted by the combustion exhaust gas, the gas calorie is high even in the low-calorie high-moisture content refuse, and the cycle requiring rapid high-temperature heating is required. It can be used as a fuel for the mouth combustion melting furnace. That is, it is possible to provide a “gasification and melting furnace” that can be used regardless of the calorific value of the raw material waste.

According to the fourth aspect of the present invention, since the fluidized bed temperature can be adjusted in the intermediate moving bed, a circulating fluidized bed composed of a plurality of fluidized beds having different temperatures can be constructed.

Further, according to the invention as set forth in claim 5, it is possible to dechlorinate waste plastics containing vinyl chloride and the like in a relatively short time due to the characteristics of the fluidized bed. High temperature corrosion due to HC 1 gas can be prevented.

As is clear from the above, according to the present invention, in the heat treatment of municipal solid waste and waste plastics, etc., a gasification and fusion furnace that combines a pyrolysis gasification fluidized bed furnace and a cyclone combustion and melting furnace, which have many environmental advantages, is used. The furnace can be made compact and its applicability can be greatly expanded. Industrial applicability

TECHNICAL FIELD The present invention relates to a fluidized bed used for heat treatment of solid waste such as municipal solid waste and waste plastic, and can be suitably used for waste treatment.

Claims

The scope of the claims

1. A fluidized bed is formed in a loop shape, and the middle of the loop-shaped fluidized bed is divided by a moving bed into a plurality of fluidized beds having independent free boards. A circulating fluidized bed characterized in that a fluid medium is circulated using a specific gravity difference as a driving force.

2. The circulating flow according to claim 1, wherein the fluidized bed is formed in an annular shape, and a cycle-port combustion melting furnace is constructed at the center of the annular fluidized bed.

3. The annular fluidized bed is separated by two moving beds to form a pyrolysis gasification fluidized bed and a combustion fluidized bed of charcoal type, and the generated pyrolysis gas is sent to the central cycle combustion combustion furnace. 3. The circulating fluidized bed according to claim 2, wherein the fluidized bed is supplied.

4. The circulating fluidized bed according to claim 2, wherein a heat transfer tube is provided in the moving bed.

5. The annular fluidized bed is divided into two moving beds to form a dechlorination fluidized bed and a pyrolysis gasification fluidized bed, and the generated pyrolysis gas is supplied to the central cyclone combustion and melting furnace. The circulating fluidized bed according to claim 4, wherein