KR810000398B1 - Shaft furnace for pyrolysis of refuse with bed support structure - Google Patents

Abstract

Shaft furnace for the pyrolysis of pelletised refuse has a hearth(1) in the base, for combustion and melting, provided with an oxygen supply. The pellets are supported on a structure formed by >=3 cooled refractory supports(7) which extend inwards from the hearth wall(14). This structure is in the lower part(6) of the hearth but above the oxygen supply. The supports form peripheral spaces(13) which extend through the structure and converge downwards. These spaces are formed by the side wall surfaces of adjacent members and the inside surface of the hearth. The support arrangements permit solid lumps of char formed in the pyrolysis zone to pass through into the combustion zone in the base of the hearth.

Description

Furnace for Pyrolysis of Garbage with Layer Support Structure

1 is a vertical sectional view of a furnace hearth having a waste layer support structure in accordance with the present invention.

2 is a plan view taken along line 2-2 of FIG.

3 is an illustration of the layer support structure shown in FIG. 2 of FIG.

4 is a horizontal cross-sectional view of the upper surface of the layer support structure showing the use of eight support elements of two different sizes.

FIG. 5 is a detail along the centerline 5-5 of one long support element shown in FIG. 4.

6 is a plan view of a vertical hearth provided with four support elements with side walls spread downward.

7 is a vertical sectional view taken along line 7-7 of FIG.

8 is a cross-sectional view of another device in which a support element is installed on the wall.

9 is a partial cutaway view of a device with a layer support structure in accordance with the present invention.

FIELD OF THE INVENTION The present invention generally relates to apparatus for the treatment of solid waste and for the recovery of useful resources therefrom, particularly to improved vertical furnaces or converters for thermal decomposition of waste.

In an effort to solve ecological problems caused by previous methods of treating solid waste and in an attempt to recover as much of the natural resources contained in the waste as possible, a process as described in US Pat. No. 3,729,298 has been developed. Developed by Anderson.

In a nutshell, the Anderson process consists of waste being fed to the top and oxygen to the bottom of the vertical furnace. Furnaces (or conversion furnaces) are divided into three functional areas. That is, it is divided into a drying zone at the top, a pyrolysis zone at the middle, and a combustion zone and a melting zone (or hearth) at the bottom, but they are not clearly distinguishable.

That is, they have no distinct line to fractionate and change somewhat fluidly during operation. The waste descends from the furnace and is first dried by the heat from the furnace and then pyrolyzed. In the pyrolysis process, organic matter in the waste is decomposed and pyrolyzed at oxygen-deficient atmospheric pressure to produce substances such as CO, H ₂ and charcoal.

As the waste passes through the pyrolysis zone, some are converted to ascending volatiles and some are converted to charcoal descending into the hearth. It burns with oxygen to produce the heat needed to melt carbon monoxide, carbon dioxide, and inorganic solids such as glass and metal in the waste. As a result, the molten debris is continuously removed from the hearth and cooled in the water tank. A gas mixture containing at least 50% carbon monoxide and hydrogen (dry) is discharged from the top of the furnace. After purification, the gas is used as intermediate BTU fuel gas or as a raw material for chemical synthesis.

Suitable apparatus for carrying out the above-mentioned Anderson process is shown in US Pat. No. 3,801,082.

In order to effectively and continuously process the crushed waste through the blast furnace, it is necessary to form debris from the waste prior to feeding the blast furnace in order to ensure that the crushed waste is too densely packed to excessively restrict the flow of gas through the shaft. need.

The characteristics of the waste fragments required for smooth long term operation are described in Anderson's application in US Application No. 675,935, filed April 12, 1976. According to Anderson, the appropriate fragments are characterized by:

(1) It has a specific gravity greater than that given in the equation below.

From here ;

D = specific gravity of the debris sphere (1bs / cu ³ )

A =% of minerals in waste debris

(2) the ratio of surface area to volume greater than that given in the equation below;

R = 0.075 (G / H) 0.625

From here ;

R = ratio of surface area to volume of debris (ft ² / ft ³ )

H = height of rubbish bed in furnace (ft)

G = waste feed (ton / day / ft ² , ft ² ; unit area of furnace section).

When operating shaft furnaces of the type described in US Pat. No. 3,801,082 relating to coarse waste delivery, it has been found that sudden confusion or agitation over normal operating limits tends to occur periodically in the operation of the furnace. This confusion is thought to be caused by the periodic breakdown of roadbed waste beds and the lack of adequate gas mixing and distribution in the furnace.

In order to overcome the above problems, a method for supporting a waste debris layer in a shaft furnace has been provided. However, such a support must be able to withstand the high temperatures of the furnace (about 3000 ° F) and provide high oxidation conditions at the bottom of the furnace, as are the various components of the waste that form the various products.

It is known that layer support structures are used in coal gasification furnaces as well as in gas furnaces.

The new code discloses the use of water-cooled metal grids in a coal gasification furnace in US Pat. No. 3,253,906.

There, agglomerated bituminous coal is supported on metal grids composed of hollow metal pipes extending across the furnace through which the cooling medium passes. The combustion of coal takes place on the grid, so that the solid remains on top of the grid, but only dissolved product flows through it. The use of support grids formed of horizontal hollow metal rods covered with refractory materials is also reported in cupola oxygen furnaces as described in US Pat. No. 3,802,678 to Tafts. Above these bars is a spherical layer of refractory spheres in which the contents of the furnace reside. These spheres allow gas to pass and provide sufficient passage length and contact time for the falling metal contents to dissolve and overheat. Thus small droplets of metal fall through the support grid and collect in a pool at the base of the shaft furnace.

The support structure shown in the aforementioned U.S. patent has the function of not allowing solid objects to pass through them, but only molten metal to flow to the hearth. Such a lattice structure is not satisfactory for use in shaft furnaces for pyrolysis of garbage debris.

This is because in the pyrolysis zone the charcoal formed from the rubbish debris has to be burned through the lattice grid and burned to generate the heat necessary to thermally decompose the organic matter of the garbage and fluidize the inorganic material.

At the same time, fragments of unpyrolyzed waste should not flow down to the roadbed, otherwise they will disrupt the operation of the furnace.

It has a structure that can support a layer of garbage debris on top of it for disposal of waste and generation of useful fuel gas, and provides a shaft furnace that allows the solids of charcoal to pass through the support structure to the combustion zone at the bottom of the hearth. It is an object of the present invention.

It is still another object of the present invention to provide a shaft furnace having a support structure capable of withstanding significant high temperatures in the furnace of a furnace for pyrolysis of waste.

The above and other objects apparent to those skilled in the art are achieved by the present invention, which includes the following.

In the vertical shaft furnace for pyrolysis of debris with a dry zone at the top, a pyrolysis zone at the middle and a furnace at the base of the furnace with oxygen supply, the improvement includes a waste bed support structure. The support structure described above is located at the bottom of the hearth, but above the oxygen supply device, and comprises at least three cooled fire-resistant structural materials having a side wall and extending radially inwardly from the hearth wall towards the shaft of the hearth. The above-described support structure is characterized in that it extends through the above-described structure and has a plurality of surrounding spaces gathered downwardly, each space being formed by at least a portion of the side surface of the adjacent structure and the inner surface of the hearth. .

In general, the diameter of the largest inscribed circle suitable for the horizontal cross section of the surrounding space in the support structure is three times smaller than the diameter of the loaded waste crusher.

Another such inscribed circle decreases downward in diameter.

In one specific embodiment of the present invention, the structures are blocked near the axle to form a central space extending through the support structure described above.

The cross section (in a horizontal piece corresponding to the supporting structure) of the central space mentioned above is 40% or less of the total cross section of the hearth in the same plane.

A concrete implementation according to the invention is that the shaft furnace has a base support structure, in which the support members are tightly attached to their side ends in a cooled fire resistant toroidal structure, the axis of which is parallel to the axis of the furnace. Device.

The design's most preferential structure has the surface of the toroidal structure described above, facing its Prusto-conical shaft and converging downwards.

Reference is made to FIGS. 1, 2 and 3 specifically illustrated to aid the understanding of the present invention, where the conical hearth is a wall mounted with four equally symmetrically spaced support structures 7. And with it the base support structure.

The hearth 1 of the furnace is attached to the bottom of the cylindrical shaft 2. The hearth 1 comprises a conical metal shell 3 in line with the refractory material 4. The hearth 1 is composed of four support members, separated by a support structure into an upper end 5 and a lower end 6.

Each support structure 7 extends in the axial direction from the wall of the hearth 14 to which it is tightly attached, and has a horizontal top surface 8 and left and right side wall surfaces 9 and 10, respectively. Each extends vertically down and parallel to each other.

Each of the support structures 7 contains a surface 11 facing the hearth and the usual mandrel 19 of the support structure.

The surface 11 extends vertically down, which occurs after it is inclined towards the wall of such a hearth 14 having an inclined surface 12. As a result of the inclination of the surface 12, the central space 13 formed by the support structure 7 becomes larger in the horizontal cross section as it progresses downward. That is, if one wants to draw an inscribed circle A in the middle of the space formed by the four support structures as illustrated in Figure 2, each of the majority of such inscribed circles in the horizontal plane has a diameter as the inscribed circle has the surface 12 open out. After the increase of the surface (11) beyond the length of the mandrel in the direction of the mandrel to maintain a constant distance.

Therefore, the space 13 constrained by such an inscribed circle forms a cylinder through which the cone extends outward. Such a shape 13 ensures that any charcoal that passes through the top open at the midpoint of the layer support structure can access the bottom 6 of the hearth.

Inscribed circle B in the horizontal plane in the surrounding space 15 formed by the side walls 9 and 10 of the support structure 7 and the wall of the hearth 14 adjacent to FIG. 2 is a conical hearth wall 14 of the mandrel. It shows that the size decreases in the downward direction of the mandrel due to the fact that it is less and less in the direction. As a result, each space 15 gathers down, thereby causing pinching and wedging movements to such debris passing into the space 15.

As a result the support structure not only acts to hold the image of the rubble debris on it by the top surface 8 of the support structure 7 but also promotes bridging beyond the space 15. As the wedged debris (invisible) is consumed in the support structure, they will be reduced in size until they can pass through the surrounding space 15, and thus will burn in the lower roadbed 6. Oxygen is supplied into the lower end of the hearth 6 via an injection tour 18. The inorganic material is dissolved in the hearth and forms a pool of molten metal with the slag 16 and is collected at the lower end of the furnace and flows out through the slack tab 17.

4 illustrates a device in which eight support structures are used, four of which 41 are long elements, symmetrically placed around the roadbed. Four short support structures 42 are equally provided between them. The sides of the support elements 41 and 42 are vertical and the surfaces 43 and 43 'are parallel to each other while the sides 44 and 44' extend outwards from the axis towards the wall of the hearth 45.

Figure 4 also illustrates another arrangement of the support elements, where the long element 41 extends (by dashed line 46) to form an element 47 and to sharpen it in the middle (by the dashed line 46). There is no open space below the center of the. However, since the converged element 47 occupies only a small space, a sufficiently open space can be maintained for the proper functioning of the support structure.

5 is a cross-sectional view taken along line 5-5 of the long support structure 41, illustrating the manner in which the support structure is made, whether long or short. As shown in FIGS. 1-3, each of these support structures may be formed of steel or steel in which water or other cooling medium is circulated to keep them cool enough to prevent their decomposition by high temperature and corrosive air in the hearth. The copper tube 52 is made of a refractory material provided.

The support structure 41 is tightly attached to the refractory wall or hearth lining 53 and the metal shell 54. Although only a flat coolant tube 52 is illustrated in FIG. 5, it is evident that an improved thermal conductivity effect can be obtained by attaching something like a metal thermal conductive pin to the copper tube 52.

Water is the preferred cooling medium, but other liquids or gases may be used that are lower in temperature than the hearth. Other suitable cooling media include air, steam, chlorinated biphenyls or any fluids in the process that need to be heated.

6 and 7 illustrate another hearth and support structure according to the invention, wherein the hearth is circular rather than conical. The hearth consists of a cylindrical metal shell 71 of fire-resistant linings 72, with four support struts 73 tightly attached thereto, each of which has a sidewall inclined downward toward the wall 72. 75) and (75 '), and a horizontal top surface 74.

The surface 78 facing the mandrel is vertical and consequently the central space 79 extending through the support structure is cylindrical and is formed by inscribed circle A moving downwards. Since the side walls 75 and 75 'are inclined downwards, the diameter of the inscribed circle B (the respective peripheral space formed by the side surfaces 75 and 77' of the hearth wall 72 and the adjacent support structure 73) 77) located on a horizontal plane of the interior), which decreases downwards, thereby allowing the surrounding space 77 to be sharpened downward and to control the passage of solids into the lower roadbed 76.

FIG. 8 illustrates a device for support structure 80 that may be used in place of those shown in FIGS. 1, 4 and 6. FIG. The support 80 installed on the fire resistant lining 83 of the metal hearth shell 84 has a horizontal top surface 85 and an axis of the hearth, and has a surface 86 inclined downward toward the axis and therefrom the hearth wall. It is inclined backwards along the surface 87 towards.

By installing a number of such roadbed structures 80, the space formed in the center of the roadbed support structure has a sharpened cone shape.

That is, the surface 86 directs the flow of the debris into the midpoint of the lower roadbed towards the center of the support structure.

The holding structure 80 is provided with a cooling pipe 82 to prevent the fire resistant support structure from being corroded by the severe condition of the road.

9 is a partially cut isometric view, illustrating one specific arrangement of a layer support structure according to the present invention. This device differs from those described above in that it contains an additional toroidal structural component 91 in the center of the support structure. Component 91 is attached to four support structures 94 (only three are visible) at their axial ends. The opposite distal end of the support structure is attached to the wall 92 of the hearth 93.

The toroidal component 91 is trapezoidal in cross section and forms a conical inner surface 95 and an inclined outer surface 96 toward the hearth wall 92. Each support structure 94 has side walls 97 and 98 inclined downward. Each group of four adjacent surfaces 97, 92, 98 and 96 therefore forms one of the four converging spaces 99 converging down through the support structure. The four surfaces forming each periphery 99 are the side surfaces 97 of one support structure 94, the inner surface of the hearth wall 92, the side surfaces 98 of the adjacent support structure 94 and the toroid structure structure. It is the outer surface 96 of 91.

The support structure has five downwardly converging spaces, four peripheral spaces 99 and a conical central space 100, all of which extend through the support structure.

With such a structure, the charcoal feed rate to the hearth can be adjusted, and the charcoal can also be moved towards the center of the hearth bottom. Although not illustrated in FIG. 9, the toroidal frame 91, like the axial support frame 94, is circulated by a cooling medium through pipes installed in the fire resistant structure to prevent deterioration of the device due to adverse conditions inside the hearth. Each is cooled.

EXAMPLE

A layer support structure as described in US Pat. No. 3,801,082, but with a shaft shaft having a cylindrical axis, such as the design shown in FIG. 4, i.e. having four short support structures with four open center spaces and four long support structures. It improved by installing.

The vertical part of the shaft furnace is about 26 feet in height and 10 feet in inner diameter, in the case of the upper cross section of the conical furnace. The hearth, about eight feet deep, has a layered support attached to the lower end of its wall.

의 예각(제1도에서

)으로 경사져 있다. 각각의 지지구조대는 시장에서 구할 수 있는 내화성의 레밍재로 구성되어 있는데, 그 내부에는 냉각수가 순환되어지는 2인치 구리파이프가 부착되어 있다. 핀 내화물질을 통한 열순환 율을 증가시키기 위하여 냉각튜브에 구리핀을 부착 시켰는데, 그에 의하여 지지구조대 위에서 보호의 슬랙스컬이 유지된다.The top of the layer support structure is about 85 inches in diameter, 3 feet above the road surface, and the end of the support structure extends about 30 inches down. Therefore, the depth of the support structure slightly exceeds one third of its diameter. The axial dimensions of the long support structures are 31 inches, while the axial sizes of the short supports are 24 inches. The roadbed is approximately 69 formed by the roadbed wall and the horizontal plane at the top of the roadbed.

Acute angle of (in Figure 1

Tilt to). Each support structure consists of fire-resistant reaming materials available on the market, with two-inch copper pipes inside which coolant is circulated. Copper fins were attached to the cooling tube to increase the thermal cycling rate through the fin refractory material, thereby maintaining the protective slacks on the support structure.

Shaft furnaces were operated using loaded rubbish in the form of shreds about 13 inches in diameter and about 6-12 inches in length. The operating conditions in the furnace were maintained within the range detailed in US Pat. No. 3,729,298. It was satisfactory to operate with a long time period.

There were no such serious problems as bed collapse and poor gas mixing, confusion in operation.

The present invention has several important advantages over the prior art.

One advantage with the present invention is that it allows for high temperatures in the bottom furnace. In pyrolysis of waste from the Anderson process, it is important to maintain the highest temperature at the bottom of the furnace so that it remains dissolved for the outflow of slag. At the same time, sufficient heat must also be generated in the bottom furnace from charcoal, the main fuel source, to pyrolyze the rubble debris layer in the upper shaft. This benefit is achieved by selectively allowing only charcoal to pass through the support structure.

The layered support structure of the present invention ensures that the pyrolytic waste does not pass through it. This is important because if pyrolyzed fragments enter the furnace and burn, they will be at a lower temperature than if charcoal is burned.

Another advantage of the present invention is that the charcoal passes through the hearth with the charcoal evenly distributed on the horizontal section of the blast furnace so that the rubble debris layer moves uniformly in the pyrolysis zone and the bed falls smoothly without undesirable flow channels. That's one point. Such a uniform space distribution in the bed allows the flow of hot gases through the bed to maintain a constant velocity, resulting in a uniform distribution of heat and practically uniform and complete pyrolysis of the waste in the bed. In addition, the present invention forms a cavity under the layer support structure and on the pool of molten slack to allow it to act as a gas mixing chamber and to serve various auxiliary roles to achieve a uniform flow of ascending gas through the shaft.

Claims (1)

In a vertical shaft furnace for pyrolysis of debris waste, having a drying zone at its upper end, a pyrolysis zone at its middle, and a furnace installed at the bottom of the furnace for supplying oxygen for combustion and melting. An improvement is in the use of a waste bed support structure, which is installed on the bottom of the hearth and above the oxygen supply device, extends inward axially from the hearth wall towards the hearth axis and has at least three cooling with side walls. Composed of fire-resistant support elements, having a plurality of side peripheral spaces extending through the above-described structure and gathered toward the bottom, the above-mentioned peripheral space is formed by at least how close the side of the adjacent support structure and the inner surface of the roadbed. The diameter of the largest inscribed circle suitable for the horizontal cross section of the surrounding space described above is Less than three times of the old debris hit, the diameter of the inscribed circle is such a shaft furnace for thermal decomposition of waste with a layer support structure characterized by reduced going downward.

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