The incineration of waste material, such as garbage or vegetable waste, having a high moisture content has proven to be as a difficult task. The high moisture content along with the fact that the moisture is not evenly distributed through- out the mass of waste results in uneven and incomplete combustion.

In a pyrolytic incineration system, the waste material is heated in a combustion chamber which causes the waste material to give off a combustible gas containing hydrocarbons and other combustible components. The gas given off in the combustion chamber travels upward into an afterburner which burns the gas. The afterburner is contained in an area of the incinerator generally called the thermostack.

After combustion in the thermostack, the gas exists the thermostack and enters a scrubber unit.

Depending on the nature of the waste material being incinerated, the combustion gas being discharged from the system may contain substantial particulate material such as fly ash. To meet emission requirements, it is often necessary to incor- porate a scrubber in the incineration system in order to minimize the emission of the particulate material. One type of scrubber as used in the past consists of a series of baffles or scrubber members, which are suspended in spaced relation within the scrubber chamber, and are arranged in a pattern to provide a tortuous path of flow for the combustion gases. This arrangement of baffles results in a high velocity flow of combustion gas between adjacent baffles and areas of low velocity or stagnation adjacent the front and rear surface of the baffles, causing heavier particulate material to fall by gravity along the front and rear surfaces of the baffles for collection in a collection bin, while lighter particulate material will collect on the front and rear surfaces. During use, the baffles tend to expand and contract, causing the collected particulate material to dislodge from the baffles, and the dislodged material will fall by gravity to the collection bin or site.

Because of the high temperatures encountered in the scrubber, it has been necessary to construct the baffles of a heat resistant alloy such as Inconel. Due to the cost of the material as well as the fabrication expense, the production of the baffles results in a substantial capital expenditure.

SUMMARY OF THE INVENTION The invention is directed an improved incineration system providing more effective and complete combustion of the waste material. The incineration system has particular application in incinerating waste material having a high moisture content such as garbage, plant or vegetable waste, and the like.

In accordance with the invention, the incineration system includes an incinerator that defines a combustion chamber containing the waste material. Air for pyrolytic combustion is supplied under the waste material through a plurality of general- ly parallel air tubes, each having a series of outlet ports through which pressurized air is discharged into the lower end of the combustion chamber. A water cooling system is employed for each of the air tubes passing through the waste material, such that the water cooling system prevents burn down during extended periods of combustion.

Combustion of the waste material results in the generation of hot combustion gases and a portion of the hot gases are withdrawn from the upper end of the combustion chamber through a recirculating conduit by a blower and are returned to the lower end of the combustion chamber through a plurality of gas tubes, which are located beneath the air tubes. In a preferred form of the invention, the gas tubes are located in vertical alignment with the spaces between adjacent air tubes and the hot gases are discharged upwardly through a series of discharge ports in each gas tube into the spaces between the air tubes.

In a preferred form of the invention, each of the air tubes are coupled to a shaking device which operates to oscillate the air tubes within the waste material to further increase the efficiency of combustion.

In a further aspect of the invention, the series of air tubes and gas tubes can be retrofit into existing incineration systems to further improve the combustion of waste material. In accordance with another feature of the invention, the air tubes and gas tubes can be combined into a single series of tubes passing through

the waste material. In this manner, the system of the invention can be easily retrofit into existing incinerators to increase the operating efficiency.

The recirculated hot combustion gases contain a substantial proportion of hydrocarbons or combustible material, and the combustible material in the recirculat- ed gas is burned in the lower end of the combustion chamber within the mass of waste material, thus providing a more efficient and effective combustion. In addition, as the circulated combustion gases can be at a temperature in the neighborhood of 2200°F (1250°C), the hot gases can aid in drying the wet waste material.

As a further advantage, the recirculated hot gases contain fines from the combustion process and as the hot gases pass upwardly through the bed of waste material, the particulate material is filtered out, thus serving to reduce the amount of particulate material or fines which is discharged from the combustion chamber through the stack.

Further, by recirculating of the hot combustion gases, the air balance of the pyrolytic system is not disturbed.

In a further aspect of the invention, the combustion gases being dis- charged from the combustion chamber through the stack are passed through a scrubber containing a plurality of spaced vertical columns of refractory material which function as baffles. Each column is preferably formed of a stack of refractory bricks which are supported from the lower wall of the combustion chamber. The stacks of refractory bricks are arranged in a pattern to provide a tortuous path of flow for the combustion gases through the chamber, and prevent direct flow of the gases from the inlet to the outlet. In a preferred form of the invention, the stacks or baffles are arranged in a series of parallel rows with the flat faces of the stacks or baffles being normal or perpendicular to the gas flow. The baffles in each row are spaced apart a distance generally equal to the width of the baffles, and the baffles in each row are staggered with respect to baffles in adjacent row. This arrangement and configuration of the stacks or baffles results in a high velocity flow of combustion gases between adjacent baffles and areas of low velocity or stagnation adjacent the front and rear surfaces of the baffles causing heavier particulate material to fall by gravity along the front and rear faces of the baffles for collection in a collection bin. Lighter particulate

material, which may collect on the front and rear surfaces of the baffles, are automatic- ally dislodged, and will also fall by gravity to the collection bin.

The use of the stacks of refractory bricks as the baffles to achieve the tortuous path of gas flow provides distinct advantages over systems using metal baffles. The stacks of refractory bricks are lower in cost than heat resistant metals, such as Inconel. The brick stacks also provide better heat resistance, have a lower coefficient of thermal expansion, and tend to hold the heat to provide a more uniform temperature in the scrubber chamber during fluctuations in combustion.

As a further aspect of the invention, the refractory bricks in each baffle or stack can be hollow to thereby provide a vertical passage which extends the entire height of the stack. The upper end of the passage is open to the atmosphere, and the bricks can be formed with outlet ports that communicate with the central passage. With this construction, air will be drawn from the atmosphere into the longitudinal passage by the natural draft of the system and will be discharged through the outlet ports into contact with the combustion gases passing through the scrubber chamber causing turbulence and mixing of the air with the combustion gases to enhance complete combustion of the gases.

Other objects and advantages will appear during the course of the following description.

The drawings illustrate the best mode presently contemplated of carrying out the invention.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS Fig. 1 is a side elevation of the incineration system of the invention; Fig. 2 is a vertical section of the incinerator; Fig. 3 is a view taken along line 3-3 of Fig. 2; Fig. 4 is an enlarged vertical section showing arrangement of the air tubes and gas tubes; Fig. 5 is a horizontal section showing a portion of the scrubber chamber; Fig. 6 is a section taken along line 6-6 of Fig. 5; Fig. 7 is a fragmentary enlarged vertical section of a modified form of the invention utilizing hollow refractory bricks; and

Fig. 8 is a section taken along line 8-8 of Fig. 7.

DETAILED DESCRIPTION OF THE INVENTION Fig. 1 shows a pyrolytic incineration system including an outer support- ing framework 1, within which is mounted an incinerator 2 that defines a combustion chamber 3 containing waste material 4, such as garbage or trash. The waste material can be fed into the combustion chamber via a feeding unit 5, and ash can be auto- matically removed from the lower end of the combustion chamber 3 through operation of an ash removal unit 6. Feeding unit 5 and ash removal unit 6 can be constructed as described in U. S. patent 4, 674, 417.

Waste material 4 can be ignited in combustion chamber 3 through use of a conventional gas burner unit, not shown, or alternately, a liquid fuel such as kerosene can be applied to the waste and ignited. Once the waste has started to burn, further fuel is not normally required.

The combustion of the waste material 4 generates hot combustion gases which are discharged from combustion chamber 3 through a stack 7 which communicates with the upper end of the combustion chamber. Stack 7 acts as an afterburner to provide complete combustion of the gases given off by the waste material 4 in the combustion chamber 3. The gases are discharged from stack 7 into a generally box shaped unit 8, which defines a combustion chamber 9. The lateral outlet of combustion chamber 9 communicates with an inlet to scrubber chamber 10 of scrubber unit 12, while the outlet of scrubber chamber 10 is connected to a combustion chamber 13 defined by combustion unit 14. After flowing through the scrubber chamber 10 and combustion chamber 13, the gases are then discharged to the atmosphere through stack 15 which is connected to chamber 13.

As best shown in Figs. 2 and 3, incinerator 2 includes an outer shell 16 formed of steel or the like, and an inner refractory lining 17.

Combustion chamber 3 is closed and air for the pyrolytic combustion process is supplied through a plurality of generally parallel air tubes 18 which are locat- ed in the bottom of combustion chamber 3. As illustrated in Fig. 4, each air tube 18 is generally square in cross section and is formed with a plurality of outlet ports 19 which are located in the sides of the tube. Ports 19 extend along the entire length of the tube and as shown in Fig. 4, one group of ports 19a is directed horizontally outward through

each corner of the tube, while a second group of ports 19b is located in each side of the tube and faces upwardly, and a third and fourth group of ports 19c and 19d are located in each side of the tube and face downwardly toward the bottom of the combustion chamber 3.

In order to prevent burn down during extended periods of combustion, a unique water cooling system is employed for the air tubes 18. As shown in Fig. 4, a pair of shrouds 21 a and 21 b formed of a heat resistant alloy, such as stainless steel, are welded to the upper and lower portions, respectively, of air tubes 18. The shrouds 21 a and 21 b define water cooling passages 22a and 22b. Cooling water is introduced into the lower passage 22b and then passes through a connecting passage at the downstream end of the air tube 18 and is discharged through the upper passage 22a.

The cooling water is supplied to the lower passage 22b by means of a water pump 23 which is mounted on the outer surface of the incinerator 2. The discharge side of pump 23 is connected through lines 24 to the lower passage 22b, while the upper outlet passage 22a is connected via return line 25 to a surge tank.

Thus, operation of water pump 23 will introduce cooling water into the lower passage 22b and water will flow through the lower passage to the downstream end of the air tube 18 and then through a connecting passage for return through upper passage 22a to the surge tank.

By the use of the cooling medium, the air being introduced into the combustion chamber will be maintained at a temperature below that which melts the air tubes 18.

The free or distal end of each air tube 18 is closed, while the opposite end of each air tube is connected to a manifold or header 20 located outside of the outer shell 16. Pressurized air is supplied to manifold 20 via an air conduit 26 which is connected to the discharge side of a conventional blower 27. Operation of blower 27 will cause air to be delivered to the air tubes 18 and the air will then be discharged through outlet ports 19 into contact with the waste material 4.

As a feature of the invention, a portion of the hot combustion gases containing combustible hydrocarbons from the upper end of combustion chamber 3 are withdrawn from the combustion chamber and returned to the lower end of the combus- tion chamber beneath the waste material 4. To provide for the recirculation of the

combustion gases, a tubular member 28, having closed ends, is positioned in the upper end of the combustion chamber 3 beneath stack 7. Tubular member 28 is provided with a plurality of inlet ports 29 which extend the length of the tubular member. The central portion of tubular member 28 is connected to a conduit 30 which extends downwardly along one side of the combustion chamber, and the lower end of conduit 30 extends in sealed relation through the side wall of the incinerator and is connected to the suction side of a conventional blower 31. The discharge side of blower 31 is connected through discharge conduit 32 to a manifold 33 which is located to the exterior of the lower end of combustion chamber 3. A plurality of generally parallel gas tubes 34 are connected to manifold 33, and the free end of each tube is closed and supported by the opposite wall of the incinerator 2. Each gas tube 34 is provided with a plurality of outlet openings 35 in the upper portion of the tube, as best shown in Fig.

4. Gas tubes 34 are preferably located in vertical alignment with the spaces between adjacent air tubes 18, so that the hot gases being discharged through the openings 35 will pass between the air tubes 18 and mix with the air being discharged from the air tubes.

The mixture of the combustible gas from each of the gas tubes 34 pass between the air tubes 18 such that the mixture of air and combustible gas supports combustion at each of the outlet ports 19. In practice, the combination of the combust- ible gas and air creates a flame at each of the outlet ports 19 which substantially aids in drying the waste material 4.

In practice, the combustion gases from the upper end of combustion chamber 3 may be at a temperature of about 1200°C, and because of these extreme temperatures, the conduits 30 and 32 are preferably formed of a temperature resistant metal, such as Inconel.

As previously mentioned, recirculated combustion gases which still contain a substantial portion of combustible material, such as hydrocarbons, are passed upwardly through the mass of waste material 4 in contact with air being supplied though air tubes 18, thus burning the combustible material in the recirculated gases to increase the efficiency of the combustion process.

In practice, when the incinerator 2 is initially filled with waste material 4, a small amount of liquid fuel such as kerosene is applied to the waste material 4 and

ignited. Once the waste material 4 has started to burn, the waste material 4 gives off a combustible gas which rises into the upper portion of the combustion chamber 3 where a portion of the combustible gas enters the tubular member 28 through the inlet ports 29. Blower 31 recirculates the combustible gas through the series of gas tubes 34.

Gas exiting the outlet openings 35 in each of the gas tubes 34 travels upward through the waste material 4 where it meets fresh air exiting outlet ports 19 contained in each of the air tubes 18. The combustible gas, when combined with the fresh air from the air tubes 18, creates a series of small flames at each of the outlet ports 19. These small flames dramatically increase the operating efficiency of the incinerator 2.

In the preferred embodiment of the invention, a shaking system operates to slightly oscillate each of the air tubes 18 within the waste material 4. Since a small flame is often present at each of the outlet ports 19, it is desirable to slightly rotate the air tubes 18 such that the small flames at each outlet port 19 comes into contact with a new portion of the waste material periodically. The shaking system includes a hydraulic piston and a series of link arms which tend to oscillate the air tubes about 15°.

As a further advantage, the hot gases being withdrawn from the combustion chamber through tubular member 28 will contain fines or particular material, and the upward flow of the hot gas through the waste material 4 will serve to filter out the fines, thus reducing the amount of fines or particulate material that is dis- charged to the stack 7.

By recirculating the hot gases of combustion, the air balance of the pyrolytic incineration system is not disturbed.

While the drawings show the recirculated combustion gases and the air being introduced into the lower end of the incinerator through separate conduits or tubes 34 and 18, it is contemplated that the two gas streams can be combined and fed into the lower end of the incinerator through a single tube. In a system where the air tubes 18 and gas tubes 34 are combined into a single series of tubes, the pair of blowers 27 and 31 could be replaced by a single blower which functions to move both the combustible gas removed from the combustion chamber and a flow of fresh outside air. By combining the air tubes 18 and gas tubes 34 into a single system of tubes, the invention more readily facilitates retrofitting of existing incinerators. With the retrofit in

place, the combination of combustible gas and fresh air in the single series of tubes would create a series of small flames at the outlet port on each of the combined tubes, thereby increasing the operating efficiency of the incinerator as discussed in the preceding description of the embodiment shown in Figs. 1-4.

The invention also includes an improved scrubber construction as illustrated in Figs. 5-6. Scrubber unit 12 includes an outer housing or shell 36 formed of steel or the like, and a refractory lining 37. Mounted within housing 36 are a plurality of vertical baffles or columns 38, each formed of a stack of refractory bricks 39. Bricks 39 can be mortared together through use of a standard refractory mortar to provide the baffles or stacks 38.

As shown in Fig. 6, the lowermost brick 39 of each stack or baffle 38 is supported on the lower wall 40 of housing 36, and wall 40, in turn, is supported by a plurality of crossbeams 41, each of which is located beneath a row of the baffles 38.

As best illustrated in Fig. 5, each brick 39 is generally rectangular in shape, having front and rear faces that are located perpendicular or normal to the flow of gas through the scrubbing chamber 10. In practice, the bricks may be about 9 inches long by 4 inches wide, by 3 inches thick. The stacks or baffles 38 are preferably positioned in a series of rows with the baffles in each row being spaced apart a distance generally equal to the length of the baffles. The baffles of each row are located in alignment with the spaces between baffles in adjacent rows resulting in the combustion gas flowing in a non-linear, tortuous path through the scrubber chamber 10 as shown by the arrows in Fig. 5.

As the refractory bricks 39 are subjected to extreme high temperatures, the bricks 39 will expand during service, and thus the upper ends of the baffles or stacks 38 are free of attachment to the scrubber housing 36. In this regard, the uppermost brick 39 of each baffle 38 extends within a recess in the refractory lining 37 and is spaced beneath the upper wall 42 of the scrubber housing as shown in Fig.

6. This construction permits the stacks or baffles 38 to expand and contract during heating and cooling.

As the combustion gases flow through the scrubber chamber 10, heavier particulate material in the gas will strike the forward faces of the baffles 38, and fall by gravity along the forward and rear faces through openings 43 in the lower wall

40, for collection in a hopper 44. Openings 43 are located adjacent the front and rear faces of the lowermost bricks 39 of each stack, as seen in Fig. 6. An outlet conduit 45 is mounted in the lower end of hopper 44 and flow through the outlet conduit 45 is controlled by a valve 46.

The use of the refractory bricks 39 to provide the baffles or columns 38 has distinct advantages over the use of metal baffles as used in the past. The refract- ory bricks are able to withstand higher temperatures without distortion or warping, and have a smaller coefficient of thermal expansion than metal baffles. As a further advan- tage, the refractory bricks will hold the heat for a longer period of time than metal, thus providing more uniform temperature conditions in the scrubber chamber 10, regardless of fluctuations in combustion.

It is contemplated that a temperature sensing mechanism 47 can be located in the upper portion of combustion chamber 3 for controlling the operation of blower 31. More specifically, if the temperature in the upper end of combustion cham- ber 3 falls below a pre-selected elevated range, the temperature sensing mechanism 47 will operate to increase the speed of blower 31 to correspondingly increase the volume of hot combustion gases being recirculated to the combustion chamber.

Conversely, if the temperature in the combustion chamber rises above the pre-selected range, the sensing mechanism 47 will operate blower 31 to reduce or curtail the flow of the hot combustion gases through conduits 30 and 32.

Figs. 7 and 8 show a modified form of the invention in which the baffles or stacks 48, similar to baffles 38, are each formed of a stack of hollow bricks 49 formed of a refractory material. When stacked, as shown in Fig. 7, the central openings in bricks 49 define a vertical passage 50 which extends the full height of the baffle.

Each brick 49 is provided with a plurality of outlets 51 which communic- ate with passage 50, and preferably outlets 51 are located in the ends of each brick 49, as shown in Fig. 8. Upper wall 42 of scrubber unit 12 is formed with a series of open- ings 52, each of which communicates with the upper end of a vertical passage 50.

With this construction, the natural draft of the incineration process will draw air from the atmosphere through opening 52 into the vertical passage 50 and the air will then be discharged through outlets 51 into contact with the hot combustion gases flowing through the scrubber chamber 10. Preferably, the air is discharged from outlets 51 in bricks 49 at right angles to the flow of combustion gases through scrubber chamber 10, thus resulting in turbulence and mixing to thereby provide more complete combustion of the combustible materials in the combustion gases.

The stacks 48 can be supported from the lower wall of the scrubber unit in the same manner as described with respect to the first embodiment, and the lower wall can be provided with openings, such as openings 43 previously described, through which the particulate material is discharged to hopper 44.

While the incinerator incorporating the recirculated gases is shown in conjunction with the scrubber unit 12, it is recognized that the recirculation system can be used with various types of incinerators and can be retrofitted to existing incinerators.