US3898317A - Method for incinerating flue gases - Google Patents

Abstract

An incineration system for incinerating flue gases which contain varying quantities of combustibles therein. Means is provided for controlling combustion air added to the flue gases when they contain combustible matter and means is provided for sensing the temperature of the combusting waste gases. When a preset temperature is exceeded, additional air is added to reduce the temperature of the gas, but when the temperature falls below the preset point, the burner firing rate is increased and the added air is cut off to insure proper incineration and achieve fuel efficiency.

Description

tates atet 1191 Hemsath et al. 1 Aug. 5, 1975 [5 METHOD FOR INCINERATING FLUE 3,695,192 10/1972 Von Brimer 110/8 A GASES 3,741,713 6/1973 Reed 431/202 [75] Inventors: Klaus H. Hemsath, Sylvania; Arvind FOREIGN PATENTS OR APPLICATIONS C. Thekdi, Toledo, both of OhiO 1,585,340 l/l970 France 431/5 [73] Assigneez. Midland-Ross Corporation Primary ExaminerL. Dewayne Rutledge Cleveland Ohlo Assistant E.\aminerArthur J Steiner [22] Filed: Feb. 25, 1974 Attorney, Agent, or FirmPeter Vrahotes; Frank J.

Appl. No.: 445,480

Related US. Application Data Nawalanic 5 7 ABSTRACT An incineration system for incinerating flue gases which contain varying quantities of combustibles therein. Means is provided for controlling combustion air added to the flue gases when they contain combustible matter and means is provided for sensing the temperature of the combusting waste gases. When a preset temperature is exceeded, additional air is added to reduce the temperature of the gas, but when the temperature falls below the preset point, the burner firing rate is increased and the added air is cut off to insure proper incineration and achieve fuel efficiency.

3 Claims, 2 Drawing Figures PATENTEU AUG 1975 FIGZ METHOD FOR INCINERATING FLUE GASES This is a division, of application Ser. No. 274,406, filed July 24, 1972, now US. Pat. No. 3,838,974.

BACKGROUND OF THE INVENTION Industrial fumescontaining common air pollutants, such as hydrocarbons, alcohols, ethers, soot and other combustibles, are frequently encountered. These fumes can be broadly divided into two types. The first type of fumes contains relatively insignificant quantities of combustible pollutants and there is an ample supply of oxygen for the combustion of the pollutants. Standard types of incinerators are readily available on the market which can be used for the incineration of such fumes.

The other type of fumes contains mainly a mixture of combustibles (hydrocarbons, soot particles, etc.) and other inert gases. The oxygen content of such fumes is relatively small. When a source of ignition, such as a premix pilot or a burner operating at stoichiometric air/fuel ratio, is placed in the fume stream, the fume cannot continue to burn because of insufficient oxygen. Presently available ineinerators,as a rule, are not able to complete combustion of the exhausts; thereby yielding exhaust gases with high quantities of pollutants.

It is, therefore, an object of this invention to provide an incineration system for incinerating industrial waste gases which contain varying amounts of combustibles therein.

It is another object of this invention to provide means for incinerating waste gases and maintaining the temperature of the combustion uniform.

It is a further object of this invention to provide apparatus to incinerate rich fumes.

It is still another object of this invention to provide means for incinerating rich fumes that achieve high fuel efficiency.

Other objects, purposes and advantages will be apparent from a consideration of the following description and the accompanying drawing in which:

FIG. 1 is a vertical cross-sectional view, partially schematic, of an incineration system incorporating the features of this invention; and

FIG. 2 is a cross-sectional view taken along line 22 of FIG. 1.

SUMMARY OF THE INVENTION A double chambered system is added to a stack emitting industrial waste gases which contain various amounts of combustibles therein. The first chamber terminates at the exit end of the stack in an annular passage, or restriction, so that air at high velocity is directed longitudinally relative the stack. This air acts as an air pump to enhance egress of the flue gases. These gases then enter into the second chamber of the housing, which chamber includes a plurality of burners. Within the second housing is a thermocouple which senses the temperature of the waste gases. A preset temperature is achieved by varying the quantities of air emitted from the first chamber as opposed to the amount of fuel and air supplied to the burners in the second chamber. In this way a constant temperature may be maintained despite the variance of combustibles within the exhaust gas.

DESCRIPTION OF THE PREFERRED EMBODIMENTS It has been found with regard to the explosion of a gas mixture containing combustibles, such as hydrocarbons, inert gases and air, that if the oxygen content of the mixture is less than 3 percent, the mixture cannot combust merely by increasing its temperature. Such mixtures are considered as above the upper combustion limit, and they are generally referred to as rich fumes.

For proper and efficient incineration of rich fumes, it is necessary to mix air with the combustibles in the fumes, and the temperature of the air/-fume mixture should be raised to a level where the reaction rates are very rapid. Thus, addition of air, proper mixing of the air with the fumes, and heating of the fumes to incineration temperature are the three most important requirements for the incineration of rich fumes. In case of very rich fumes containing combustibles which have a heating value in excess of approximately 40 Btu/ft, it is necessary to supply excess air, in addition to the combustion air, to reduce the temperature of combustion products to the practical incineration temperature, which is between l500l 800F. The amount of excess air, of course, depends on the selected incineration temperature, the heating value of the fumes and the oxygen content of the fumes. By controlling the incineration temperature, the refractory materials in the incinerator are protected.

In case of a batch type process, the fume composition, volume and temperature can vary considerably with time. For the maximum fuel economy. air and fuel supply to the incinerator must be controlled very carefully and independently.

Referring now to the drawing, an incineration system is shown generally at 10 and is adapted to incinerate exhaust fumes coming from a stack 12. The stack 12 has refractory bricks l4 lined on the inside thereof in order to preserve its heat and, as shown, has its inner wall flared out at its upper end at a shallow angle to its axis to approximately meet with its outer wall. Disposed about and above the stack 12 is a housing 16 having a lower chamber 18 and an upper chamber 20, the housing also being lined with refractory material 21. The lower chamber 18 terminates at the upper end of the stack 12 and has a restricted channel 22 portion. The lower chamber 18 also has an opening 24 therein which receives an air pipe 26.

The upper chamber 20 which, as shown, is formed of appreciably wider cross-sectional size than the restricted channel portion 22 to form within the chamber an upwardly facing flame stabilization shoulder or step located just above the upper end of the stack 12, is supplied with tangential burners 28 that are received within openings 30 in the refractory 21 and are located laterally outward of the exit end of the annular passageway 22 and immediately above the exit end of the stack 12. Gas lines 32 are attached to the burners 28 as are air lines 34. The air lines 26 and 34 are in communication with an air control unit 36.

Received within the upper portion of the upper chamber 20 is a thermocouple 38 which has a lead 40 communicating with a temperature measuring and recording instrument 42. The temperature measuring instrument 42 in turn has a lead 44 that communicates with the air controller 36.

In operation, the rich fumes are emitted from the stack 12 into the upper chamber 20. Initially, the burners 28 are fired in order to provide the heat of combustion necessary for the exhaust gases. Simultaneously, a quantity of air is supplied to the lower chamber 18 from the air line 26 and passes through the channel 22 about the exit end of the stack 12. This air passing through the channel 22 acts as an air pump to aspirate and thereby enhance the discharge, or emission, of the ex haust gases from the stack 12. Additionally, the annular stream of air from channel 22 promotes uniform mixing of the gases within upper chamber 20.

The combustion products will ignite in the upper chamber and the temperature thereof is sensed by thermocouple 38. The measuring instrument 42 will set a given temperature for the combustion products and will control the amount of air supplied to the lower chamber 18 and the upper chamber 20 in response to this temperature. When the temperature is low, additional air will be supplied to the burners 28 in order to raise the temperature and assures complete incineration of the waste gases. The burners 28 may be of the type that gas is supplied thereto in proportional response to the amount of air supplied to the burners. If the temperature becomes too high, the supply of air to the burners is discontinued and the temperature is controlled by air supplied through the air pipe 26 into the housing 16. So long as the temperature can be maintained at the set point through the supplying of air to the exhaust gases, the burners 28 need not be operated. This obviously means that the exhaust gases have a sufficient quantity of combustibles therein to independently support combustion. If the amount of combustibles in the exhaust gases are so high that the preset temperature is exceeded, an excess amount of air will be added through pipe 26 in order to lower the temperature of the combusting exhaust gases. Thus, an incineration system is provided which is operative to completely combust waste gases emitted from a stack, regardless of the amount or percentage of combustibles contained in the gases. I

What is claimed is:

4 1. A method of incinerating rich fume combustible gases emitted from a generally cylindrical stack into a larger. generally cylindrical combustion chamber having an open upper end and a reduced diameter lower end surrounding said stack in spaced relation to define an axially extending annular passageway circumscribing said stack, said method comprising the steps of:

introducing combustion air through said annular passageway at a velocity sufficient to enhance the egress of said fumes from said stack into the annulus of air exhausted from said passageway to define a mixture which expands radially in said combustion chamber until striking the walls thereof at some distance dependent on said velocity whereat stoichiometric mixing is assured; heating said mixture to assure combustion by directing combusting gases from a burner in said combustion chamber to penetrate said mixture prior to said mixture striking the walls of said combustion chamber; sensing the temperature of said combustion chamber at a point therein removed from said stack; and

controlling the air supplied to said passageway and said burner in a dependent manner to maintain a predetermined temperature in said combustion chamber whereby thorough combustion of said rich fumes is achieved independent of the composition of said fumes.

2. The method of claim 1 further including the step of introducing said combusting gases from said burner tangential to the walls of said combustion chamber at a position approximately aligned with the exit end of said stack.

3. The method of claim 1 further including the step of increasing said flow of air through said passageway to effect cooling of said chamber walls while said heat dissipated from said burner is correspondingly decreased by a decrease of air supplied thereto when said temperature of said combustion chamber increases above said predetermined value.

Claims (3)

1. A METHOD OF INCINERATING RICH FUME COMBUSTIBLE GASES EMITTED FROM A GENERALLY CYLINDRICAL STACK INTO A LARGER, GENERALLY CYLINDRICAL COMBUSTION CHAMBER HAVING AN OPEN UPPER END AND A REDUCED DIAMETER LOWER END SURROUNDING SAID STACK IN SPACED RELATION TO DEFINE AN AXIALLY EXTENDING ANNULAR PASSAGEWAY CIRCUMSCRIBING SAID STACK, SAID METHOD COMPRISING THE STEPS OF: INTRODUCING COMBUSTION AIR THROUGH SAID ANNULAR PASSAGEWAY AT A VELOCITY SUFFICIENT TO ENHANCE THE EGRESS OF SAID FUMES FROM SAID STACK INTO THE ANNULUS OF AIR EXHAUSTED FROM SAID PASSAGEWAY TO DEFINE A MIXTURE WHICH EXPANDS RADIALLY IN SAID COMBUSTION CHAMBER UNTIL STRIKING THE WALLS THEREOF AT SOME DISTANCE DEPENDENT ON SAID VELOCITY WHEREAT STOICHIOMETERIC MIXING IS ASSURED, HEATING SAID MIXTURE TO ASSURE COMBUSTION BY DIRECTING COMBUSTING GASES FROM A BURNER IN SAID COMBUSTION CHAMBER TO PENETRATE SAID MIXTURE PRIOR TO SAID MIXTURE STRIKING THE WALLS OF SAID COMBUSTION CHAMBER,

2. The method of claim 1 further including the step of introducing said combusting gases from said burner tangential to the walls of said combustion chamber at a position approximately aligned with the exit end of said stack.

3. The method of claim 1 further including the step of increasing said flow of air through said passageway to effect cooling of said chamber walls while said heat dissipated from said burner is correspondingly decreased by a decrease of air supplied thereto when said temperature of said combustion chamber increases above said predetermined value.

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