US2252326A - Incineration - Google Patents

Description

s- 12, 9 I R. LEWERS 2,252,326

' INCINERATION 1 Filed March 5,- 1938 INVENTOR GEORGE R. LEWERS LL. ATTORNEY Patented Aug. 12, 1941 UNITED STTES OFFICE INCINERATION- George R. Lowers, Brooklyn, N; Y., assign'or to Underpinning & Foundation. 06., Did, New

York, N. Y., a corporation ofNew York Application March 5, 1938; Serial No'. 194,058

2 Claims.

My invention relates to incineration and more particularly to improvements in tiered multiple hearth furnaces adapted for the drying and burning of moist material such as municipal wastes including partly dehydrated sewage, sewage sludge and garbage. It should be understood that the apparatus of the present invention may be used in the treatment of other kinds of material.

The principal objects of the invention are to provide novel, advantageous and effective forms of apparatus for treatment of material of the general character specified. Another object of the invention relates to improvements in tiered multiple hearth furnaces divided into separate drying and burning sections by intermediate hearths with gas seals, whereby part of the hot gases of combustion from the burning section is brought into direct contact with material in the drying section and when passed out of the drying section at a lower temperature is passed into the burning section to eliminate noxious odors therein and also to utilize the heat units in the combustible gases in burning the material previously dried in the drying section. A further object of the invention relates to the treatment of hot gases passing from the drying section by using a condenser which liquefies the moisture in the exhaust gasesfrom the drying section thereby decreasing materially the pounds of gas to be handled in the incinerating or burning zone and by the hues and. stack through which the gas passes later.

In carrying out the invention, use may be made of a tiered multiple hearth furnace in which an intermediate hearth is provided with a gas seal to divide the furnace into an upper drying section and a lower burning section. In a furnace of this kind the material introduced at the top of the furnace may be worked downwardly from.

on the hearths thereof and, when discharged from the drying section laden with gases and vapors produced in drying, may be passed directly to the burning section or may first be freed of certain vapors by condensation so as to decrease the amount of gas supplied to the burning section.

Noxious odors produced in the drying operation may be eliminated by the high temperature in the burning. section. By this arrangement the B. t. 11-. value of combustiblegases in the stream of gases passing from the drying section is utilized to advantage instead of being lost, as for example, in prior types of apparatus in which such a stream is not passed through the burning section but is burned outside the furnace after mixing with the remaining gases of combustion passing from the burning section .of the furnace, either with or without the use of a heat exchanger to raise the temperature of the stream from the drying section before such mixing.

Fur'therobjects, features and advantages will appear upon consideration of the following description and of the drawing in which the figure isa view in vertical section" of a preferred embodiment of theapparatus of the present invention.

Referringto the drawing, there is disclosed an apparatus including a multiple hearth furnace it]; having a; peripheral wall II, a top 12 and hearths 13,1I4, 15, I6 1! and I8, of which the hearth I8 serves as the bottom of the furnace. Material may be supplied at the top of the furnace by means of a chute 20 extending through the top l2, the chute being provided with a gas seal whichmay be in the form of a conveyor screw 2;], Working in-a tubular casing 22 communicating with the upper end of the chute 20. As herein disclosed, material introduced through the chute 20 passes into the upper compartrnent of the furnace and falls on the hearth I3 near its periphery. The material thus depositedon the hearth I3 is agitated and moved inwardly to a central outlet 23 by one or more rabbling devices each of which comprises a radial arm 24; and inclined blades 25 extending downwardly therefrom, the arm 24 being supported and actuated by a hollow vertical shaft 26 passing through the central part of the outlet 23. Actuationof the shaft Zl'i may be effected by means of a bevel gear 21 meshing with a bevel gear 2 8 and a pulley 29 connected in a suitable manner the bevel gear 28 and actuated from any suitablesource of power.

The shaft 25 is provided above each of the hearths I 4, I 5, I6, I! and 18 with rabbling devices similar to thoseabove the hearth I3, but above the hearths I 4, IB- and [8, the blades are inclined in the opposite direction so as to Work thematerial to peripheral'outlets. The hearth I4 is shown as provided with one outlet 30 provided with a gas seal including a tube in the outlet 30and extending downwardly to within a short distance of a platform 3! on which the material passing downwardly through the outlet 30 piles up and serves to keep the tube closed. The hearth I6 is provided with two or more outlets 3|], and the hearth I8 is provided with a single outlet (not shown) provided with a gas seal which may be of any suitable form. Feeding of the material downwardly through the gas seal to the hearth l8 may be effected by sweeps or sweep arms 32, each of which removes at each revolution some of the material from the shelf or platform and allows other material to settle down through the outlet 30. be mounted on a rabble arm 24. The apparatus just described constitutes one form of means for feeding solid material through the hearth l4 while preventing the flow of gases therethrough. The hearths l5 and I! are provided with'central outlets 23 corresponding to that in the hearth.

I3. The top [2, and the hearths l4, l6 and [8 are provided with gas seals around the vertical shaft 26.

Air may be supplied to the interior of the burning section through a duct 33 connected to the interior of the hollow vertical shaft 26 and through one or more openings or nozzles 34 connecting the interior of the shaft with the interior of the burning section. Air may also be supplied to the burning section through one or more stoking openings 35 as controlled by doors (not shown). Hot gases of combustion may be withdrawn from the burning section, in any suitable manner, preferably through branch ducts 35 leading from the various compartments of the burning section to a manifold or duct 31 connected with a flue 38 through which gases are discharged under natural or forced draft, each of said ducts 36 being provided with a damper 39.

Drying of the material in the drying section may be effected by passing a portion of the hot combustion gases from the duct or manifold 31 through the drying section as by means of an inlet duct 40 preferably leading into the upper part of the drying section, an outlet duct 4| preferably leading from the lower part of the drying section, and a fan 42 connected with said outlet duct 4|. The flow of combustion gases through the drying section may be controlled in any suitable manner as, for example, by means of a damper 43 in the duct 4|.

In passing through the drying section, the combustion gases pass over the material on the drying hearths and take up water and other vapors. Also, when the temperature is high enough, the flow of the combustion gases through the drying section produces combustible gases, some of which may have obnoxious odors, the temperature in the drying section being below the ignition point for these gases. As will be brought out more fully hereinafter, the heat units in such combustible gases may be utilized to assist the burning operation in the burning section of the furnace.

The gas stream discharged from the fan 42 may be passed directly to the burning section or may first be passed through a condenser 44 which may comprise a cooling element 45 on which condensed liquid will collect and drop into a collecting sump 45 provided with a drain 41. The stream of gases and vapors discharged from the fan 42 may be controlled by a suitable device, which may be in the form of a flap 48, either to pass through a duct 49 to the condenser 44 and from the condenser to 'a duct 50 leading to the burning section or to pass through a duct 5| Each sweep arm 32 may directly to the duct 50, thus short-circuiting the condenser. The duct 50 may serve as a manifold from which branches 52 lead to the various compartments of the burning section, each of the branches 52 having a damper 53. Obviously by adjusting the dampers 39 in the ducts 36 and the dampers 53 in the ducts 52 the flow of gases through the burning section of the furnace may be varied extensively.

When the stream discharged from the fan 42 contains considerable matter that can be condensed and removed, the stream should be directed to the condenser 44 thus decreasing greatly the pounds of gas to be handled within the incinerating or burning section and by the flues and stack and also the fans if fans be used.

In the operation of the apparatus, material to be treated is fed to the uppermost compartment and falls on the hearth I3 and then may be fed downwardly in the usual manner being dried in the drying section above the hearth l4 and burned in the burning section below this hearth. Air is supplied to the burning section through one or more openings 34 in the central shaft or through a stoking opening 35. The combustion gases pass through one or more branch ducts 36, as controlled by the dampers 59, to the duct 31 which directs the gases to the discharge duct or stack 38.

However, some of the combustion gases in the tube or manifold 31 are drawn through the drying section to the fan and may be supplied through the condenser 44 or around the condenser to the duct 50, from which the gases pass under control of the dampers 53 to the interior of the burning section.

It should be understood that the present apparatus enables the disposal of moist material such as sewage sludge in a very advantageous and economical manner.

It should be understood that various changes may be made and that various features may be used without others, without departing from the true scope and spirit of the invention.

Having thus described my invention, I claim:

1. In apparatus for drying and burning moisture containing material such as sewage sludge, the combination with a multiple-hearth furnace comprising a hearth dividing the furnace into an upper multiple-hearth drying section and a lower multiple-hearth burning section and means for feeding solid material from the drying section downwardly past the dividing hearth to the burning section while maintaining a gas seal; of means for supplying air to the burning section, means for withdrawing hot gases of combustion from the burning section and the furnace including a discharge manifold and branch discharge ducts connecting the manifold with the compartments over the hearths of the burning section, means for varying the flow of gases through the various branch discharge ducts to vary the location of the highest temperature combustion in the burning section, means for passing hot gases of combustion from the discharge manifold through the drying section to remove vapors and gases including combustible gases from the drying section, a condenser through which the gases and vapors from the drying section are passed to remove water vapor and other condensable material, and means for passing gases including combustible gases from the condenser to the burning section including a manifold and branch supply ducts connecting the manifold with the compartments above the hearths of the burning section, and means for varying the flow of gases through the supply branch ducts to vary the supply of combustible gas to the various compartments of the burning section.

2. In apparatus for drying and burning moisture containing material such as sewage sludge, the combination with a multiple-hearth furnace comprising a hearth dividing the furnace into an upper multiple-hearth drying section and a lower multiple-hearth burning section, rabbling means for advancing the material over said hearth including a rotary air-cooled shaft, and means for feeding solid material from the drying section downwardly past the dividing hearth to the burning section while maintaining a gas seal; of means for supplying air directly from said central shaft to the burning section in the upper part thereof, means for withdrawing hot gases of combustion from the burning section and the furnace including a discharge manifold and branch discharge ducts connecting the manifold with the compartments over the hearths of the burning section, means for varying the flow of gases through the various branch discharge ducts to vary the location of the highest temperature combustion in the burning section, means for passing hot gases of combustion from the discharge manifold through the drying section to remove vapors and gases including combustible gases from the drying section, a condenser through which the gases and vapors from the drying section are passed to remove water vapor and other condensable material, and means for passing gases including combustible gases from the condenser to the burning section including a manifold and branch supply ducts connecting the manifold with the compartments above the hearths of the burning section, and means for varying the flow of gases through the supply branch ducts to vary the supply of combustible gas to the various compartments of the burning section. GEORGE R. LEWERS.

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