US3910207A - Apparatus for pyrolytic decomposition of waste materials - Google Patents

Abstract

A hearth apparatus for use in combination with a pyrolysis chamber for waste disposal adapted to support and provide conditions for efficient combustion, pyrolytic decomposition and ensuing removal of the resulting waste residue which comprises at least a pair of oppositely disposed elongated sloping refractory walls which are spaced by and terminate in an elongated openably closed bottom to form a trough-like structure, a plurality of tubes connected to a pressurized air supply passing through the sloping walls providing air sufficient to maintain proper combustion and to fluidize and move pulverulent residue down the sloping walls to a storage area or discharge.

Description

United States Patent [1 Altmann Oct. 7, 1975 1 APPARATUS FOR PYROLYTIC' DECOMPOSITION OF WASTE MATERIALS [22] Filed: May 28, 1974 [21] Appl. No.: 473,349

[52] US. Cl. 110/8 R; l10/75 R; 110/165 R [51] Int. Cl. F23G 5/00; F23L 1/00; F23] 1/00 [58] Field of Search 110/8 R, 18 R, 28 Q, 72 R,

Primary ExaminerKenneth W. Sprague Attorney, Agent, or Firm-Charles J. Speciale, Esq.

[5 7] ABSTRACT A hearth apparatus for use in combination with a pyrolysis chamber for waste disposal adapted to support and provide conditions for efficient combustion, pyrolytic decomposition and ensuing removal of the resulting waste residue which comprises at least a pair of oppositely disposed elongated sloping refractory walls which are spaced by and terminate in an elongated openably closed bottom to form a trough-like structure, a plurality of tubes connected to a pressurized air supply passing through the sloping walls providing air sufficient to maintain proper combustion and to fluidize and move pulverulent residue down the sloping walls to a storage area or discharge.

4 Claims, 8 Drawing Figures APPARATUS FOR PYROLYTIC DECOMPOSITION OF 'ASTE MATERIALS BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates generally to a pyrolytic waste disposal system and more particularly to an improved hearth structure intended for use with a pyrolysis chamber for waste combustion and pyrolysis and removal of residue therefrom.

2. Description of the Prior Art Thermal destruction of waste materials in quantities of up to several tons an hour is commonly accomplished in two classes of equipment, incineration and pyrolysis.

Current incineration equipment provides a waste receiving chamber which is generally a refractory lined box having a door for the extrance of waste in one wall, an exit gas port in a second wall, a forced air burner in one or two other walls and a hearth, usually comprised of metal grates which support the waste. This hearth permits the waste, when decomposed enough to become friable, to fall into an ash pit. The effluent gas from this chamber is largely oxidized hydrocarbon although it contains some combustible components and unburned particles of combustible and inert matter which may be carried in the turbulent, high velocity gas. Secondary chambers are usually provided to complete the combustion but frequently do not accomplish this effectively. The ash which has fallen through the grate usually contains much unburned matter. This ash is usually removed, when the equipment has been shut down by mechanical devices, either powered or manual. The items which will not fall through the grates must be removed, from time to time, in order to achieve full use of the chamber. The grates may be of stationary or moving type but all are subject to destructive conditions due to high temperatures, oxidizing conditions and mechanical abuse. Since this equipment frequently is inefficient and an environmental pollutor, it is falling into disfavor.

Pyrolytic decomposition equipment, now becoming more common, meets the shortcomings of the incinerator by providing thermal decomposition in a two-step process. Waste is placed in a chamber which is largely sealed against the admission of air except through special openings. The chamber is commonly refractory lined and may be fitted with auxiliary burners for use with some types of waste. There is an opening for the admission of waste, a space for the waste to remain quietly lying on an essentially solid hearth, which has been in turn provided with holes supplying air in limited and, in some cases, controlled quantity. The air supports enough combustion to release heat which pyrolytically decomposes the major portion of the waste. The products are hydrocarbons, carbon monoxide and a very small quantity ofparticulate materials. These rich gases are ducted to an after burning device in order to complete the oxidation process. My copending patent application filed concurrently herewith describes an improved device of this type.

In operation, waste is added until the chamber is too full of ash to function efficiently or to accept more waste, at which time the process is stopped, the pyrolysis chamber cooled and the residual ash removed by mechanical devices powered or manually operated. The remaining material is usually a finely divided, light weight, inorganic material mixed with incombustible lumps.

Several weaknesses in the state of the art exist relative to the decomposition stage, and most center around the configuration and function of the hearth and the handling of inert residue. The first requirement of the hearth is to support the waste and distribute the air in such a fashion that combustion proceeds uniformly no matter what type the waste material may be. Items that lay flatly and compactly against the bottom or that conform to the shape of the bottom tend to block the holes supplying combustion air and permit inactive areas that may never burn. Bottom designs employing widely spaced air holes also encourage dead areas. The result of these are the slow or incomplete disintegration of waste and a rapid buildup of residue. The residual materials may also be putrescent and unsatisfactory as a fill material. On the other hand, excessively high velocity air directed into the waste material may be so great to jet the light ash upward into the gas stream where it may remain as a particulate pollutant in the stack gas.

It is highly desirable to be able to operate the pyrolysis chamber for long periods it is most efficient after it is hot and has developed a small bed of ash. This is commonly accomplished by building larger chambers or attempting to use ash removal doors during the operation. Large chambers become inefficient and eventually must be cleaned while opening doors upsets the control of air and produces problems in combustion. Bulk ash removal, either during the burning process or after shut down, tends to take unburned waste and frequently causes airborne ash to be generated either inside or outside the equipment.

SUMMARY OF THE INVENTION It is therefore among the principal objectives of this invention to provide a hearth structure and associated devices which, when used in a pyrolytic waste destruction chamber, will produce major improvements in the support of waste of all types, a uniform distribution of air, velocities sufficiently low to prevent generation of airborne dusts and removal of ash to a location where mechanical removal is simplified.

In accord with the objectives, there has now been provided a hearth structure in combination with a pyrolytic waste destruction chamber wherein the hearth structure comprises at least a pair of oppositely disposed elongated sloping walls of refractory material which are spaced by and terminate in an elongated openably closed bottom to form a trough-like assembly, a plurality of tubes connected to a pressurized air supply passing through the sloping walls at longitudinally and transversely spaced intervals providing air sufficient to maintain proper waste combustion and residue fluidization. Removal of the waste residue can be in continuous fashion by employment of an automatic conveyor which removes the same as it is generated or, by gravity or periodic removal through an exit port provided for that purpose. The subject hearth is installed at the bottom of the pyrolysis chamber.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be hereinafter more fully described with reference to the accompanying drawing in which:

FIG. 1 is sectional elevational side view of the invention hearth structure as positioned at the bottom of the pyrolysis chamber with automatic conveyor associated therewith and with a suitable after-bumer device shown only by phantom lines mounted atop the pyrolysis chamber. FIG. 2 is a sectional front view taken along line 2 2 of FIG. 1 in the direction of the arrows.

FIGS. 3a and 3b are sectional telescopic views along line 33 of FIG. 2 in the direction of the arrows, with two different means of ashresidue removal shown.

FIG. 3c is a view similar to FIG. 3a and 31) except showing yet another embodiment of the invention.

FIG. 4a, 4b and 4c are sectional, fragmented front views of the ash removal systems of FIGS. 3a, 3b and 3c, respectively.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the figures of the drawing and specifically to FIGS. l2, 3a and 4a there is shown therein an essentially closed chamber (e.g. pyrolysis chamber) lined on roof and walls with refractory material 12. The chamber 10 is fitted with an access door 14 removably fitted over an access port 16 to permit waste introduction, an exit port 18 for conducting gases generated into a secondary combustion chamber, such as in my said copending. patent application filed concurrently herewith, and a new hearth structure 20 which is the subject of the present application.

Hearth structure 20 comprises at least a pair of oppositely disposed elongated sloping planar walls 22 which are sloped at an angle between about 20and 60from the horizontal. The sloping walls 22 terminate in and are spaced by either an openable bottom wall 24 (FIGS. 3b and 412) or by a fixed plate 26 along which the ash may be propelled (FIGS. 3a and 4a.

As shown, particularly in FIGS 1 and 3a, removal of residual ash can be accomplished by a conventional conveyor (e.g. drag chain or screw) moving through opposing slots 27 located at either end of the fixed plate 26, so that continuous removal may be effected. Or as shown in FIG. 3b, removal can be through bottom gates 32, or by hoe or scoop (not shown) through end door 34.

In another embodiment illustrated by FIGS. 30 and 4c, the hearth structure is provided with a pair of oppositely disposed spaced sloping planar walls 36, which are sloped at an angle between about 20 and 60; the same as walls 22, but are at right angles to the latter. Walls 22 and 36 terminate in an opening 38 shaped like that formed by an inverted truncated pyramid. While the embodiment in FIGS. 3b and 4b shows both bottom opening clean out or end opening clean out access to the incinerated waste in the trough 40, the embodiment shown in FIGS. 30 and 4c is provided with a hopper bottom hearth 42 with pivotable sector gates 44 for ash drop.

In actual practice, only one type of hearth structure would be employed. The hearth walls 22, 36 are made of an abrasion resistant concrete refractory material. The walls 22 and 36 are provided with air ducts 46. These are connected to the refractory surface with air tubes 48 connected to a central conventional pressurized air supply 50 only partially shown. The tubes are longitudinally and transversely spaced along the refractory walls and deliver low velocity air to locations approximately 6 inches apart, but no more than 9 inches,

when viewed as in FIG. 1. The air blower (not shown) supplies air through conduits 51 at velocities of from 1 to 20 feet per second and in an amount sufficient to maintain the combustion rate required by temperature sensors (not shown) in the stack. This air quantity and velocity are sufficient to fluidize or move the pulverent ash remaining from final combustion. This fluidization is essential since theash normally has a high angle to repose unless disturbed, with the aid of the air blast, the residue moves down the sloping walls to rest at the bottom of the hearth where no air is being introduced. Larger matter such as glass and heavy cans no longer supported by the ash fall to the bottom as well.

As earlier mentioned the removal of residual ash (not shown) may be by drag chain conveyor or screw conveyor (FIGS. 1, 2, 3a and 4) or by removal through bottom gates or by hoe or scoop through an end door) (FIG. 312), or finally through a bottom dump (FIG. 40).

The steeply sloping hearth walls afford tumbling of boxed waste and piled papers to permit easier access of combustion supporting air and heat. This is important, especially during start up, when no combustion has been established. These deep valleys, as it were with air jets reaching near the top permit much ash storage before the air supply is reduced due to deep coverage of all air ducts.

What is claimed is:

l. A hearth structure in combination with a pyrolytic waste combustion chamber wherein the hearth structure comprises at least a pair of oppositely disposed elongated sloping walls comprising refractory material which are spaced by and terminate in an elongated openably closed bottom to form a resulting troughshaped assembly, a plurality of tubes connected to a controlled pressurized air supply through said sloping walls at longitudinally and transversely spaced intervals providing air sufficient to maintain proper waste combustion and fluidization of resulting combusted ash residue, and wherein another pair of similarly oppositely disposed elongated sloping walls are provided by at right angles to the original said pair of oppositely disposed walls.

2. A hearth structure according to claim 1 wherein all of said oppositely disposed walls terminate in an form an openable bottom hearth.

3. A hearth structure according to claim 1 wherein said similarly oppositely disposed walls are each inclined at an angle between about 200 and 4. A hearth structure according to claim 1 wherein all said sloping walls are inclined at an angle between about 20 and 60.

Claims (4)

1. A hearth structure in combination with a pyrolytic waste combustion chamber wherein the hearth structure comprises at least a pair of oppositely disposed elongated sloping walls comprising refractory material which are spaced by and terminate in an elongated openably closed bottom to form a resulting trough-shaped assembly, a plurality of tubes connected to a controlled pressurized air supply through said sloping walls at longitudinally and transversely spaced intervals providing air sufficient to maintain proper waste combustion and fluidization of resulting combusted ash residue, and wherein another pair of similarly oppositely disposed elongated sloping walls are provided by at right angles to the original said pair of oppositely disposed walls.

2. A hearth structure according to claim 1 wherein all of said oppositely disposed walls terminate in an form an openable bottom hearth.

3. A hearth structure according to claim 1 wherein said similarly oppositely disposed walls are each inclined at an angle between about 20*0 and 60*.

4. A hearth structure according to claim 1 wherein all said sloping walls are inclined at an angle between about 20* and 60*.

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