GASIFIER AND INCINERATOR FOR BIOMASS SLUDGE DESTRUCTION

Field of the Invention

This invention relates to incinerators and the like for processing biomass waste, and particularly biomass sludge and sludge-like matter such as animal manure or other sewage sludge, and the like.

Background of the Invention

It is necessary that various biomass sludges, particularly such as animal manure from factory farms where perhaps many thousands of animals are raised for purposes of slaughter, should be properly processed so that they are reduced to inert, sterile material. It can happen that these forms of biomass and other related volatile solids may have infectious or even deadly bacteria or viruses in them, which must be destroyed. Animal manure may have a significant quantity of water, but may also comprise large percentages of hydrogen, carbon, and also a number of trace elements, such as nitrogen, sulphur, iron, chlorine, magnesium, manganese, sodium and potassium, among others. It

is desirable to heat all of these materials so that the organic matter is converted to gases, preferably harmless gases such as elemental hydrogen and oxygen, which oxidize to water vapor, and to residual carbon dioxide as well as to residual compounds and elements. The residuals, which are typically solids at ambient room or environmental temperature, should end up as inert mineral materials.

In order to accomplish the reduction of such biomass waste and related volatile solids into relatively inert gases and minerals salts, alloys, or other compounds, it is necessary to heat these materials sufficiently so as to break the chemical bonds between the molecular structures. Intense heating is required to break the various chemical bonds, such as hydrogen-carbon bonds. It is necessary that essentially all of the hydrogen-carbon bonds be broken, as the bonds are typically found in organic material, which organic material must be destroyed. Such extreme heating of such materials in this manner is known as pyrolysis, which is defined as chemical decomposition by the action of heat. Typically, such pyrolysis is carried out at temperatures in the order of 850° C. to 1000° C. The ash material that is ideally produced, which ash material is composed mostly of mineral salts, will glow an orangey-red color when it is at 1000° C. and will ultimately be a white ash when it has cooled. The main constituents of the organic materials, namely hydrogen and carbon, are gasified, to form mainly carbon dioxide and water. What is not desirable as an end product, and is even unacceptable, is black colored ash. Such black colored ash indicates that the ash is not completely reduced and that there is still carbon and hydrocarbon material, among other materials, in the ash. The ash, therefore, might contain organic material therein, which organic material might even be in the form of bacteria or viruses, or might be chemical compounds, including toxic materials, such as dioxins, furans and other organo-chlorides. Basically, the heat causes the waste material to process itself, which processing mostly includes the pyrolytic breaking of the various chemical bonds, such as hydrogen-carbon bonds so as to permit gasification of all the materials possible.

Briefly, incineration of a biomass comprises two stages, the gasification stage and

the carbon stage. In the first, gasification, stage, gases are driven off from the biomass as it is being heated ~ that is to say, as it absorbs heat — and such gases comprise water, hydrocarbon gases such as methane and the like, and other volatile organic compounds (VOC). As the gasification stage comes to an end, the remaining sludge will typically have become a dry powder-like substance comprising particularly carbon and other minerals. During the carbon stage of incineration, the carbon is oxidized, typically by providing additional air flow, and carbon dioxide will be driven off from the remaining ash.

Moreover, it should be noted that the two stage incineration of biomass sludge in keeping with present invention will only occur in a hot hearth system, as discussed below; and that the first, gasification, stage will typically occur without the necessity for additional oxygen, and at a slightly lower temperature, than the second, carbon, stage. Also, typically additional oxygen, usually as air, is provided to the side of the incinerator where the carbon stage incineration takes place. A study of a large scale feedlot cattle operation in Texas, where several thousand cattle are kept in close quarters one to another rather than being allowed to graze on grassland, and where the cattle feed from troughs, shows that cattle manure may be produced in quantities such as 200 tonnes per day. Obviously, burying or ponding that quantity of biological sludge-like mass can only be a short term solution. Even so, there may be runoff or other contamination of the surrounding area, and of the local environment.

Regrettably, a well known example of runoff from a so-called "factory farm", where the runoff entered a municipal water supply, occurred in the city of Walkerton, Ontario, Canada, in May of 2000. Seven people died, mostly because of the presence of e-Coli; and over 2300 people became ill. All of this occurred as a consequence of runoff from one or more factory farms where beef cattle were raised for slaughter, and where contaminated rainwater entered the aquifer or other underground water source from which the municipal water supply was pumped. The municipal water system was

improperly monitored and supervised; but it is doubtful that the tragedy would have occurred if there had been proper controls to prevent such runoff.

The present inventor has quite unexpectedly discovered that a biomass sludge such as cattle or other animal manure, or even human waste, can effectively be burned or incinerated by pyrolysis, as discussed above, in a continuous process as described hereafter, and in such a manner that very little additional energy input is required once the pyrolyzation process has been established. The biomass sludge is effectively the sole fuel which functions to ensure its own destruction by pyrolysis or gasification.

The nature of the biomass sludge which can be incinerated in keeping with the present invention must be such as to have a relatively fine consistency; preferably having a particle size which is less than 1 cm, and more typically in the range of 1 to 5 mm. Moreover, the sludge may comprise up to 100% of finely divided solids content, but typically a biomass sludge such as animal manure has a range of solids from 20% up to about 80%, with the balance being liquid. As will be discussed hereafter, the biomass sludge must be such that it can be moved by an auger.

It will also be emphasized hereafter that the present invention comprises a so-called a "hot hearth system"; meaning that the charge of biomass sludge which is to be incinerated will reside over a very hot hearth which is heated from below in the manner discussed hereafter. Moreover, as will be discussed hereafter, the present invention presents a continuous operation for the incineration of biomass sludge, rather than by way of batch processes which require cooling and heating cycles of the incinerator. Obviously, if incineration of a biomass sludge can be accomplished using a continuous process, thereby avoiding cool-down and heat-up of the incinerator, then very consequential savings in energy can be accomplished.

Brief Description of the Drawings

Embodiments of this invention will now be described by way of example in association with the accompanying drawings in which:

Figure 1 is a sectional side elevation view of a first prior art incinerator; Figure 2 is a sectional side elevation view of a second prior art incinerator;

Figure 3 is a sectional side elevation view of a third prior art incinerator;

Figure 4 is a plan view of the third prior art incinerator;

Figure 5 is a simplified front view of a biomass gasifier and incinerator in keeping with present invention; Figure 6 is a simplified plan view of the biomass gasifier and incinerator in keeping with the present invention;

Figure 7 is a simplified front view of an alternative biomass gasifier and incinerator in keeping with the present invention;

Figure 8 is a simplified front view of a further alternative biomass gasifier and incinerator in keeping with the present invention;

Figure 9 is a sectional side elevation view similar to Figure 3, but showing structural details of a biomass gasifier and incinerator in keeping with the present invention; and

Figure 10 is a plan view similar to Figure 4, but showing structural details of a biomass gasifier and incinerator in keeping with present invention.

Description of the Prior Art

Nearly all biomass incineration takes place in an incinerator that comprises at least two chambers—a primary chamber into which the biomass charge is placed for incineration, and either a secondary or heat transfer chamber that is in heat transfer relationship to the primary chamber, or an afterburner chamber that passes to the exit flue for the incinerator.

In order to obtain volatization of all of the biomass material in the primary

chamber, it is necessary to break the bonds ~ mainly hydrogen-carbon bonds — between the various molecules. This breaking of the bonds is essentially a chemical reaction, generally an endothermic chemical reaction, and requires that an amount of external heat energy be introduced into the material in order for the various reactions to take place. Oxidation reactions are exothermic, these reactions provide for the release of heat energy from the reacted materials. This released heat energy in the afterburner chamber tends to cause an increase in the temperature in the primary chamber, which increase in temperature therefore tends to urge those materials towards their volatilization temperatures. If the external heat energy introduced into the biomass material is at a very high temperature or is applied very abruptly, especially in a concentrated area, then two things tend to happen: Firstly, any reactions that occur tend to be rather violent, thus causing the production of fly-ash into the fumes of the volatilizing biomass; secondly, the sudden and concentrated reactions produce a large amount of heat energy, which in turn can cause the abrupt volatilization of the surrounding material, which volatilization can be somewhat violent. Further, if a substantial amount of material is volatilized, in the manner discussed immediately above, over a relatively short period of time, then the ambient temperature of the primary chamber will tend to rise substantially, thus causing the remaining biomass to be volatilized more quickly, but not at a controlled rate. In other words, the reaction is, at least to some degree, out of control.

In order to have a continuing volatilization reaction that is generally controllable and that is free from abrupt changes in heat generation rates and reaction rates, and which is therefore relatively free from abrupt physical disturbances, it is necessary to apply external heat energy so as to effect a continuing slow rise in temperature of the biomass material to its volatilization point.

All known prior art incinerators and cremators are designed to use relatively forceful techniques, in terms of the application of heat to a biomass material, in order to volatilize the biomass material. Essentially, all known prior art incinerators use "brute

force" to cause the required volatilization, based on the assumption that more heat energy input will cause more chemical reaction and volatization.

Traditional incinerators and cremators, an example of which is shown in prior art Figure 1 , and as indicated by general reference numeral 1 , employ two or more burners, with a first burner 2 being in the primary chamber 3 of the incinerator 1 - the primary chamber being where the biomass charge or other material for incineration is placed—and a second burner 5 being located in the fume vent 6. The first burner 2 in the primary chamber 3 is directed at the biomass 4 and is intended to initially ignite the biomass 4. It is found, however, that the fumes that are driven off contain a great quantity of materials, such as fly-ash, having hydrogen-carbon bonds, and other unincinerated materials.

Therefore, the second burner 5 is included so as to act as an afterburner to further burn the materials that are found in the fumes. However, relatively large pieces of material, such as fly-ash, may contain several million or billion molecules; and, accordingly, such pieces of material as are borne by the fumes may not get fully incinerated in the time that they take to pass through the afterburner chamber 7.

The first burner 2 in the primary chamber 3 is aimed directly at the biomass 4, or other material to be incinerated, so as to cause direct burning of the biomass 4. The flame tends to cause the biomass waste to inflame and also tends to physically agitate the biomass 4. As a result, an undesirably high amount of fly-ash is included within the fumes from the burning biomass 4. The fumes and the fly-ash contain unburned materials which may be organic materials, and which also might include unwanted dangerous chemicals such as dioxins, furans and organo-chlorides.

Further, this type of conventional prior art incinerator 1 does not provide sufficient heat intensity on an overall basis to properly incinerate all of the waste material. Only localized heat is provided by way of the first burner 2 within the primary chamber 3, which first burner 2 incinerates the exterior of the biomass 4, and also by way of the floor 8 of the primary chamber 1, which floor 8 eventually heats up sufficiently so as to cause burning of the biomass 4 immediately in contact with it. There

is often not enough heat intensity to cause complete gasification even of the materials that do burn, and certainly not enough heat intensity to cause complete gasification of the waste material at the centre of the biomass. Indeed, it has been found that the waste material at the centre of the biomass charge 4 does not burn much at all. The ash that is produced is still black, which indicates that the ash is composed largely of carbon. It has been found that typically there is also undesirable material such as dioxins, furans and organo-chlorides, and other organic matter. This black ash is typically about 10% to 15% by volume of the original waste material (and about 15% to 25% by weight).

Figure 2 discloses an improved incinerator and cremator that overcomes some of the problems encountered with conventional prior art incinerators and cremators. This incinerator is essentially that which is taught in the present inventor's U.S. Pat. No. 4,603,644, issued Aug. 5, 1986. The incinerator and cremator taught in that patent, and as indicated by the general reference numeral 10, has a vent 11 in the back wall 12 of the primary chamber 13, which vent 11 leads to a vertically disposed flame chamber 14. The flame chamber 14 comprises first a mixing chamber 15 wherein the flame from the sole burner member 16 mixes with the fumes from the primary chamber 13, and an afterburner chamber 17 where the fumes from the mixing chamber 15 are reacted—so as to break the hydrogen-carbon bonds~and gasify the materials in the fumes. This process is known as "cracking". The afterburner chamber turns a 90° corner, where the majority of "cracking" takes place. A relatively short horizontally disposed portion of the afterburner chamber 17 leads into a generally horizontally disposed heat transfer chamber 18. The heat from the "cracking" of the hydrogen-carbon bonds in the afterburner chamber 17 causes an elevation of temperature, to about 1000° C, of the heat transfer chamber. The heat within the heat transfer chamber rises through the roof 19 of the heat transfer chamber, which is also the floor of the primary chamber, so as to heat the primary chamber and the biomass 9 within the primary chamber 13. In this manner, the biomass 9 receives conductive and convective heat from the heat transfer chamber 18, which conductive and convective heat assist in the heating of the biomass 9 in the

primary chamber 13. The burner member 16 is located at the top portion of the mixing chamber 15, immediately beside the vent 11 from the primary chamber 13. Accordingly, the flame from the burner member 16 provides direct radiant heat into the primary chamber 13 through the vent 11. This direct radiant heat reaches the biomass 9 being incinerated and partially assists in the heating of the biomass 9 (known as "direct radiant heat volatilization"). Such incineration by way of direct radiant heat tends to cause burning of the biomass 9 so as to cause premature ignition which leads to incomplete combustion in the early stages of the process. An ignition burner 19 is also included to assist with combustion of the waste mass. The firing of this burner can cause instability in the primary chamber and cause the emission of fly-ash material. Some of the fly-ash becomes gasified within the afterburner chamber 17; however, it is quite possible that some of the fly-ash can pass through the afterburner chamber 17 without being completely gasified. Such incomplete gasification is generally unacceptable as this material might include hydro-carbons, dioxins, furans, and other unwanted organic matter such as bacteria, viruses, and other micro-organisms.

All known prior art incinerators and cremators use one or more, and possibly even several, control systems in order to try to stabilize the temperature within the primary chamber. It has been found that the use of such multiple control systems tends to produce an overall system wherein the temperature in the primary chamber may vary and, therefore, cannot be considered stable. Such lack of stability is caused by the plurality of control systems essentially working against each other.

It has been found that such prior art incinerators and cremators as discussed above, due to the inherent nature of the incineration process that occurs, produce an unacceptable end product. The fumes that are produced have relatively high levels of hydro-carbons, dioxins, furans, among other materials and substances, and also may contain fly-ash, while the resulting ash remaining in the incinerator may have unwanted organic matter such as bacteria, viruses, and other microorganisms. It can therefore be seen that incineration of biomass waste and related volatile solids is generally

unacceptable as it does not render potentially infectious waste totally safe.

A further prior art approach is that which shown in Figures 3 and 4, which show a gasifϊer indicated by the general reference numeral 20. This gasifier 20 is that which is shown in the present inventor's United States patents 5,611,289 issued March 18, 1997, and 6,116,168 issued September 12, 2000. The gasifier 20 comprises a primary chamber

30 shaped to receive therein a charge of waste material 22 to be gasified. The primary chamber 30 includes a main door 32 to permit selective access to the primary chamber. A low volume air inlet 34 may be included in the door member 32 for permitting the inflow of small amounts of air or oxygen into the primary chamber 30. The floor 36 of the primary chamber 30 is made of a suitable refractory material so as to be strong enough to support the weight of any material placed therein, which may be several thousand pounds. The floor 36 is also heat-conductive so as to allow heat to enter the primary chamber 30 from below.

A fume transfer vent 38 is located at the back of the primary chamber 30 and disposed near the top of the primary chamber. The fume transfer vent 38 is in fluid communication with the primary chamber 30 so as to permit the escape of fumes from the primary chamber 30 when the charge of waste material 22 is being gasified therein. The fumes from the fume transfer vent 38 comprise gases and also molecules having hydrogen, carbon, and oxygen atoms therein, with many of the constituents having hydrogen and carbon bonded together, accordingly with hydrogen-carbon bonds.

A vertically disposed mixing chamber 40 is in fluid communication with the fume transfer vent 38 and thereby accepts the fumes from the primary chamber 30. An afterburner chamber 42 is in fluid communication with the mixing chamber 40. In the preferred embodiment, the afterburner chamber has a vertically disposed first portion connected at a 90° corner, as indicated by double-headed arrow "A", to a horizontally disposed second portion 46. The "corner to corner" width at the 90° corner is greater than the width of the afterburner chamber 42 so as to maximize the effect of the afterburner chamber 42, as will be discussed in greater detail subsequently. The afterburner is

thereby shaped and dimensioned to permit the heating flame to fully oxidize substantially all of the constituents of the fumes from the primary chamber.

A burner member, in the form of an auxiliary heat input burner 48 is situated at the top of the mixing chamber and is oriented so as to project a heating flame downwardly through the mixing chamber 40 and into the first vertically disposed portion of the afterburner chamber 42. The heating flame from the auxiliary heat input burner 48 causes additional oxidization of the constituents of the fumes so as to completely resolve the main portion of these components into carbon dioxide and water vapor — water vapor being a gas at and above temperatures of about 100° C. The mixing chamber permits mixing of the constituents of the fumes from the primary chamber 30 with the ambient air in the mixing chamber and also with the oxygen from an oxygen inlet 49 that is juxtaposed with the auxiliary heat input burner 48.

The auxiliary heat input burner 48 has a fuel inlet and an air inlet to permit the supply of fuel and oxygen gas, respectively, to the input burner 48. A control means is operatively connected to the input burner 48 by way of wires 57, and is used to control the supply of fuel to the input burner 48. It is typically necessary to adjust the flow of fuel to the auxiliary heat input burner 48 initially so as to produce a substantial heating flame that extends into the afterburner chamber 42. As the afterburner chamber 42 generally increases in temperature, the flow of fuel to the auxiliary heat input burner 48 is typically decreased, as less input is required to keep the afterburner chamber 46 at a generally constant temperature once the gasification process is underway.

A partitioning wall 50 is disposed between the mixing chamber 40 and the primary chamber 30 and also between the vertically disposed first portion 44 of the afterburner chamber 42 and the primary chamber 30. The partitioning wall 50 is positioned and dimensioned to preclude the heating flame produced by the auxiliary heat input burner 48 from entering the primary chamber 30, and also to preclude the radiation from the heating flame from directly entering the primary chamber 30. In this manner,

the heating flame does not directly heat the waste material 22 in the primary chamber and, therefore, does not abruptly overheat a localized area of the material. Particularly, the partitioning wall 50 precludes physical agitation of the material 22 by the heating flame from the auxiliary heat input burner 48, thereby precluding the production of fly-ash from the waste material 22 as the material 22 is being heated and gasified.

The partitioning wall 50 is variable in height by way of the subtraction or addition of bricks 51 therefrom, so as to allow for "fine tuning" of the cross-sectional area of the fume transfer vent 38. Typically, the fume transfer vent 38 is kept as large as reasonably possible so as to allow for ready escape of the fumes from the primary chamber 30. In the afterburner chamber 42, the hydrogen-carbon bonds in the various materials, among other bonds, break down and oxidize so as to produce a net exothermic reaction. The breaking of the hydrogen-carbon bonds, which is known in the industry as "cracking", takes place largely at the 90° corner between the vertically disposed first portion 44 and the horizontally disposed second portion 46 of the afterburner chamber 42. This corner is referred to as the "cracking zone".

As the fumes exit the horizontally disposed second portion 46 of the afterburner chamber, they enter the heat transfer chamber 52. The heat from these exothermic reactions causes the heating of the heat transfer chamber 52 to a very high temperature, ultimately to about 1000° C. This temperature is, of course, adjustable by way of the control means 56 of the auxiliary heat input burner 48. As the heat from the "cracking" of the hydrogen-carbon bonds, in addition to the residual heat from the auxiliary heat input burner 48, increases the temperature within the heat transfer chamber 52, the control means 56 can be used to decrease the heating flame being projected from the auxiliary heat input burner 48. This control means 56 can be interfaced with a thermocouple 58 that senses the temperature within the heat transfer chamber 52. The thermocouple 58 is electrically connected by way of wires 59 to the control means 56 so as to provide feedback signals to the control means, thereby allowing for automatic adjustment of the heating flame from the auxiliary heat input burner 48. The heat

transfer chamber 52 is bifurcated so as to increase the effective length of the heat transfer chamber 52, thus increasing the amount of time the hot gases within the heat transfer chamber are exposed to the floor 36 of the primary chamber 30 above, and thereby permitting more heat to be transferred from the heat transfer chamber 52 to the primary chamber 30.

The primary chamber 30 is superimposed on the heat transfer chamber 52, with the heat conductive floor 36 disposed in separating relation therebetween, such that the heat from the heat transfer chamber 52 passes through the heat conductive floor 36 so as to permit conductive and convective heating of the primary chamber 30, to thereby increase the temperature of the primary chamber 30.

The heat transfer chamber 52 is in fluid communication with a vertically disposed exhaust vent 54 located at the rear of the primary chamber 30. The exhaust vent 54 allows for the safe venting of the oxidized fumes into the ambient surroundings.

The temperature within the primary chamber can be controlled in two ways: First, the auxiliary heat input burner 48 is modulated by way of the control means 56 receiving feedback from a thermocouple 58 within the heat transfer chamber 52. The fuel input, and therefore the size of the flame from the auxiliary heat input burner 48, is selected according to the temperature experienced by the thermocouple 58. Second, a small amount of air can be permitted to pass into the primary chamber 30 by way of the low volume air inlet 34 in the main door 32 of the primary chamber 30. Permitting a very small amount of air into the primary chamber 30 can raise the temperature within the primary chamber 30.

When the auxiliary heat input burner 48 is started, the heat from the auxiliary heat input burner 48 heats up the heat transfer chamber 52, so as to thereby slowly and steadily cause a rise in temperature of the primary chamber 30. As the temperature in the primary chamber 30 rises, volatilization of the low enthalpy portions of the waste material 22 starts to occur, as the low enthalpy material 22 has, by definition, lower bond energy. The exothermic reactions of the low enthalpy material 22 which occur in the

primary chamber 30 and in the "cracking zone" of the afterburner chamber 42, combine with the heat from the auxiliary heat input burner 48 to continue to heat up the heat transfer chamber 52, so as to cause a steady and continuous rise in the temperature within the primary chamber 30. As the temperature within the primary chamber 30 increases, the higher enthalpy portions of the waste material 22 is volatilized, thus producing even more heat energy from the resulting exothermic reactions. This increased heat energy continues to combine with the heat energy from the auxiliary heat input burner 48, so as to continue to add heat into the heat transfer chamber 52 and, accordingly, increase the temperature of the primary chamber 30. Thus, there is a steady and continuous increase in the amount of heat energy given off by way of exothermic reaction of the waste material 22 over time. All the while, the thermocouple 58 in the primary chamber 30 allows for monitoring of the temperature of the heat transfer chamber 52 and permits the auxiliary heat input burner 48 to modulate itself so as to preclude the heat within the heat transfer chamber 52 from rising excessively. Essentially, the increase in temperature within the primary chamber 30 is based on the slow rise in heat energy from the continuing exothermic reactions of the material 22.

Summary of the Invention

In accordance with one aspect of the present invention, there is provided a gasifier and incinerator for use in gasifying biomass waste in the form of a sludge having particle size not greater than 1 cm, and having 20% to 100% solids content with the rest being liquid.

The gasifier and incinerator of the present invention comprises a primary chamber adapted to receive biomass sludge therein for gasification and incineration thereof. A fume transfer vent is disposed near the top of the primary chamber, and is in fluid communication with the primary chamber, so as to permit the escape of fumes from the primary chamber.

A mixing chamber is in fluid communication with the fume transfer vent to accept fumes from the primary chamber.

There is an afterburner chamber which is in fluid communication with the mixing chamber. A secondary burner member is situated in the one gasifier so as to produce an initial heating flame within a first vertically disposed portion of the afterburner chamber, and the secondary burner member has a fuel inlet and an air inlet to permit the supply of fuel and oxygen gas, respectively, to the burner member, and control means to control the supply of fuel and oxygen to the burner member. A partitioning wall is disposed between the mixing chamber and the primary chamber, and the partitioning wall defines the bottom limit of the transfer vent.

There is a heat transfer chamber in fluid communication with the afterburner chamber, wherein heated gases flowing from the afterburner chamber cause heating of the heat transfer chamber. The primary chamber has a heat conductive floor and is superimposed on the heat transfer chamber with the heat conductive floor being disposed in separating relation therebetween so as to permit conductive and convective heating of the primary chamber.

An exhaust vent is in fluid communication with the heat transfer chamber for venting the fumes into the ambient surroundings. Also, there is at least one primary auger located crosswise in the primary chamber, and being in communication at a first end with a sludge feed hopper and at a second end with an ash hopper.

Drive means are provided to rotate the at least one primary auger so as to drive biomass sludge through the primary chamber from the sludge feed hopper to the ash hopper, across the heat conductive floor.

It is noted that the heat transfer chamber underlies the at least one primary auger near the second end thereof.

Typically the dwell time of the biomass sludge as it passes across the primary

chamber from the sludge feed hopper to the ash hopper is in the range of 20 minutes to 3 hours.

An additional supply of air or oxygen is provided to the primary chamber on the side thereof which overlies the heat transfer chamber. The gasifier and incinerator of the present invention may further comprise a first liquid extraction chamber overlying the primary chamber and in heat transfer relation therewith.

In that case, a secondary auger is located crosswise in the first liquid extraction chamber, and has drive means to drive biomass sludge between a sludge feed hopper and an intermediate sludge feed hopper which is in communication with the first end of the at least one primary auger.

Thus, when the biomass sludge to be gasified and incinerated has a high liquid content, at least some of the liquid is driven off in the first liquid extraction chamber by heat being transferred thereto from the primary chamber. Moreover, a gasifier and incinerator in keeping with the present invention may further comprise a dividing wall located lengthwise in the primary chamber and having a height less than that of the primary chamber. There is an opening in the dividing wall through which the auger passes so as to drive biomass sludge from the sludge feed hopper to the ash hopper. Typically, the mixing chamber is generally vertically disposed.

Also, it is usual that the burner member is disposed at the top of said mixing chamber.

It will be noted that the partitioning wall may be variable in height.

The structure of the gasifier and incinerator in keeping with the present invention is such that typically the afterburner chamber has a vertically disposed first portion and a horizontally disposed second portion.

Also, the vertically disposed first portion of the afterburner chamber is connected in fluid communication to the horizontally disposed second portion of the afterburner

chamber by way of a 90° corner.

It will be noted that the 90° corner has a "corner to corner" distance that is greater than the width of the afterburner chamber, so as to thereby effectively increase the cross-sectional area of the afterburner chamber at that point. The present invention also provides a method of continuously gasifying and incinerating biomass waste in the form of a sludge having particle size not greater than 1 cm, and having 20% to 100% solids content with the rest being liquid, where the method comprises the following steps.

First, a quantity of biomass sludge is placed in a sludge feed hopper and some biomass sludge is introduced into a primary chamber of a gasifier and incinerator by driving the biomass sludge across the primary chamber with an auger.

A burner member located within said gasifier is started so as to produce an initial heating flame directed through a mixing chamber and vertically disposed only within an afterburner chamber. A heat transfer chamber is initially heated by way of the initial heating flame, whereby the radiation from the flame is precluded from directly entering the primary chamber.

The biomass sludge is heated in the primary chamber by way of conductive and convective heating only from the heat transfer chamber, so as to preclude physical disturbance of said biomass sludge except by the auger.

Fumes are channeled from the biomass sludge into the mixing chamber.

Only the heat from the oxidation of the fumes is used to further heat the heat transfer chamber.

The fumes are then extracted from the heat transfer chamber. More biomass sludge is continuously fed to a first end of the auger and ash is continuously removed from an ash hopper located at a second end of the auger.

Typically, the initial heating flame is directed through a generally vertically disposed mixing chamber.

Moreover, the burner member is located within the gasifier and incinerator so as to be disposed at the top of the mixing chamber.

Finally, the initial heating flame is directed into an afterburner chamber having a vertically disposed first portion and a horizontally disposed second portion.

Detailed Description of the Preferred Embodiments

The novel features which are believed to be characteristic of the present invention, as to its structure, organization, use and method of operation, together with further objectives and advantages thereof, will be better understood from the following discussion. Turning first to Figures 5 and 6, simplified views of a biomass sludge gasifier and incinerator in keeping with the present invention are shown. The biomass sludge gasifier and incinerator is identified generally with the numeral 100, and comprises a primary chamber 102, a secondary chamber or afterburner chamber 104, and at least one primary auger 106. Biomass sludge is fed into the biomass sludge gasifier and incinerator 100 from a sludge feed hopper 108 so as to be carried across the primary chamber 102 by the at least one primary auger 106, with the resulting incinerated ash being collected in an ash hopper 110.

The biomass sludge which is intended to be gasified and incinerated in keeping with the present invention may, as noted above, comprise animal manure, sewage waste, and other sludge-like biomass provided that it that there is no particulate matter which has a particle size greater than 1 cm. The biomass sludge may comprise from 20% up to 100% solids, with the rest being liquid. Other biomass sludge than manure or sewage waste might also be gasified and incinerated, and may comprise biomass waste having a high energy content. For example, ground up animal parts such as meat and bone, having a relatively high fat content, will comprise a high energy content. Gasification and incineration of such high energy biomass waste may be very important in some circumstances such as the disposal of large quantities of foul taken from farms where

avian flu is present or suspected. Likewise, cattle may sometimes be slaughtered and cut up where the presence of mad cow disease is found or suspected. It is important that such biomass waste be completely gasified and incinerated so as to preclude any chance of the viruses or other protein material carrying or causing those diseases entering into any food chain whatsoever, for humans or for animals.

In any event, the gasifier and incinerator 100 is constructed using the typical refractory materials from which such devices are normally made, being structural materials that will withstand temperatures in the range of 850° C. to 1000° C; and in some cases, up to as high as 1300° C. Typically, the augers are made of stainless steel, also so as to withstand the high temperatures to which they are exposed without loss of structural integrity. It can be noted, however, that in the operation the augers may appear with a bright red hot color. However, this phenomenon is a desired one because it ensures that heat is transferred to the biomass sludge being gasified and incinerated.

The basic structure and operation of the gasifier and incinerator 100 is not unlike that of the prior art device 20 which is discussed in reference to Figures 3 and 4. Thus, it will be seen that the return flow chamber 112 is in communication with the stack 114; and it will be understood that the gases flowing in the return flow chamber 112 are generally at a lower temperature than those which are flowing in the secondary chamber 104, because the gases will have given off heat to the heat conductive hearth 1 16. An auxiliary or secondary burner 1 18 is provided, together with a secondary air fan 120, and the purpose of the secondary burner 118 is to provide an initial or start-up flame when the otherwise continuous operation of the gasifier and incinerator in keeping with the present invention is initiated.

Fuel is provided to the secondary burner 118, and a secondary air fan 120 is operated, so as to establish heat in the vertical portion of the afterburner 104, shown at

122. That heat will, of course, cause gases to flow through the secondary chamber 104, into the return flow chamber 112, and up the stack 114. However, as those gases become hotter, more heat is transferred to the biomass sludge which is resident on the

hearth 1 16 and which is displaced and driven by the augers 106. In fairly short time, the biomass sludge will be heated sufficiently so as to begin to emit gases including water and volatile organic compounds such as methane and the like. As more and more of these volatile organic compounds are given off, they will pass into a fume transfer vent and into a mixing chamber or transfer into the afterburner chamber 104 through the vertical afterburner portion 122. Eventually, those gases are sufficiently hot so that they require little if any additional heat input from the secondary burner 118, which may then be turned off. Of course, sufficient monitoring and control means are provided to ensure that the temperature in the secondary chamber 104 is high enough to transfer sufficient heat to the biomass sludge overlying the afterburner chamber 104 in order that the carbon phase of the gasification and incineration process, as described above, may take place. If additional heat is required, then the secondary burner 1 18 will be started as necessary.

Of course, drive motors or other drive means 124 are provided so as to drive the augers 106. Typically, the speed which the augers rotate may be in the range of one rotation every three or four minutes, up to as much as 5 RPM.

Of course, depending on the nature of the biomass sludge to be gasified and incinerated, it may be that adjacent augers 106 may be driven in opposite directions. Also, the size and spacing of the augers is dependent on the nature of the biomass sludge to be gasified and incinerated.

So as to accommodate the necessity for occasional cleaning and indeed, for access to the interior of the gasifier and incinerator 100, an access door 126 is provided. Figure 7 shows an alternative form of gasifier and incinerator in keeping with the present invention, which differs only by the addition of a liquid extraction chamber 128 which overlies the primary chamber 102. Here, the sludge feed hopper 108a is located at a first end of the auger 106a, and an intermediate hopper 130 is located at the first end of the primary auger 106. The purpose of the liquid extraction chamber 128 is to permit extraction of excess liquid from the biomass sludge to be gasified and incinerated. Heat

is transferred from the primary chamber 102 through a further heat transmitting hearth 132 so as to drive gasified liquid from the biomass sludge. The gasified liquid will escape through vent 134 to the stack 1 14.

A further alternative form of gasifier and incinerator is shown in Figure 8. Here, a dividing wall 136 is provided lengthwise in the gasifier and incinerator to divide the primary chamber into two chambers 102a and 102b. They are in gas communication one with the other through vent passage 138; and it will be understood that the height of the dividing 136 may vary depending on the nature of the biomass sludge to the gasified and incinerated, but in any event it is less than the height of the primary chamber 102a, 102b. It will now be clearly understood that the present invention provides not only an apparatus by way of a gasifier and incinerator for biomass sludge, it also provides a method for gasifying and incinerating biomass sludge. In that sense, it will be understood that the method of the present invention provides for continuous gasification and incineration, rather than a batch process as has been available previously using prior art devices.

A quantity of biomass sludge is placed in a sludge feed hopper and some of the biomass sludge is introduced into the primary chamber of a gasifier and incinerator and is driven across the primary chamber by an auger. As discussed above, a burner member is started so as to produce an initial heating flame which is directed through a mixing chamber and which is vertically disposed only within an afterburner chamber. A transfer chamber is heated initially by way of the initial heating flame; and radiation from the flame is precluded from directly entering the primary chamber.

The biomass sludge in the primary chamber is heated by way of conductive and convicted heating from a heat transfer chamber which underlies the primary chamber, and physical disturbance of the biomass sludge except by a slowly moving auger is precluded.

Fumes from the heated biomass sludge are channeled into the mixing chamber, and heat from the oxidation of those fumes will further heat the heat transfer chamber.

Fumes are then extracted from the heat transfer chamber for exhaust to the ambient.

In the meantime, more biomass sludge is fed the first end of the auger through a sludge feed hopper for gasification and incineration, and ash is removed from the second end of the auger at an ash hopper. Finally, turning now to Figures 9 and 10, a somewhat more specific teaching of a gasifier and incinerator in keeping with the present invention is shown. It will be seen that these figures are not a dissimilar to Figures 3 and 4, and for the most part the same reference numerals are employed to identify the same structural features. The functioning and operation of the gasifier and incinerator shown in Figures 9 and 10 is similar to that described above with respect to the prior art incinerator shown in Figure 3 and 4.

However, several reference numerals are also employed as are used in Figures 5 to 8. Thus, augers 106 are seen in the gasifier and incinerator of Figures 9 and 10; and it will be noted from arrows 150 that adjacent augers may or may not be counter-rotating. It will also be understood that the additional air or oxygen inlet 34 is positioned so as to be in line with that portion of the primary chamber 102 which overlies the afterburner chamber 52,104. The biomass sludge 152 is driven across the primary chamber in the same manner as described above; and it is emphasized that operation of the gasifier and incinerator of Figures 9 and 10 is continuous, rather than a batch process. A secondary or auxiliary burner 118 is shown, but from the above description it will be understood that its purpose is to provide an initial heating flame. Thereafter, the secondary burner 118 may or may not function, depending on the operation of the controller 56 communicating with a thermocouple 58, and with other operating controls as will be understood by those skilled in the art. On the other hand, air or oxygen is provided to the secondary or afterburner chamber through the vent 49, and will flow continuously.

The principal point to be made is that the structure and operation of the present invention provide for a continuous gasification and incineration process; but it must be

understood that the biomass which is to be gasified and incinerated has the form of a biomass sludge. Because of the operating limitations of the augers 106, it has been determined that efficient operation of a gasifϊer and incinerator in keeping with the present invention will best be achieved when the biomass sludge is such that there is no particle having a size greater than 1 cm, and that the solids content of the sludge is in the range of 20% up to 100%.

It will also be understood that due to the nature of the operation, and particularly since it is a continuous operation, once the gasifier and incinerator is fully functional, the secondary burner can be turned off. In other words, the fuel for continuous operation of the gasifier and incinerator is the very biomass sludge which will be gasified and incinerated. Accordingly, additional energy input requirements for the operation of the gasifier and incinerator in keeping with the present invention are minimal, once it is going. Effectively, the only additional energy input requirements are electrical so as to drive the drive motor motors for the augers, so as to provide power for any electronic control which is in place, and for any other motors are fans which may be operating.

However, no additional fuel requirement is made beyond that which is required for the initial start-up flame, so there is no requirement or necessity for storage of large amounts of fuels such as diesel oil or other burner oil, propane or natural gas, and so on.

Indeed, significant long-term benefits may be derived from the use and operation of a gasifier and incinerator in keeping with the present invention in locations such as cattle feedlots and the like. As an example, in a feedlot where 200 tonnes of cattle manure are produced per day, gasification and incineration of that manure can produce as much as 2 megawatts of energy per day, in the form of electricity or steam. That energy may then be used to support many other operations being carried out at the cattle feedlot, including heating, operating power equipment for feed distribution and the like, and so on.

As noted, the typical dwell time for biomass sludge to be gasified and incinerated in keeping with the present invention may be in the range of 20 minutes up to 3 hours. If

the biomass sludge is such as ground up animal parts or the like, it is relatively dry and it has high energy content, and the dwell time will be less than if the biomass sludge has a higher liquid content and lower energy content. Moreover, biomass sludge such as cattle manure is more easily handled and has a lower liquid content than manure from swine. The latter biomass sludge may require treatment in a gasifier and incinerator which incorporates a first liquid extraction chamber such as that which is shown in Figure 7.

Determination of the dwell time may be, to some extent, empirical. However, as experience is gained by the operator, particularly in those instances where the biomass sludge to be gasified and incinerated is essentially the same at all times, then control of the driving speed of the augers can be established for the most efficient operation of the gasifier and incinerator in keeping with present invention.

It may also be possible to roughly determine the dwell time by placing a small sample of the biomass sludge to be gasified and incinerated in such as a crucible, and observing the period of time required to reduce that biomass sludge to ash on subjecting the biomass sludge to very high temperatures that will be experienced in the primary chamber of the gasifier and incinerator of the present invention.

Other biomass sludge material that may be gasified and incinerated in keeping with the present invention may include human sewage disposal effluent. This may have certain advantages in some circumstances such as the provision of portable toilets for temporary gatherings of large numbers of people — for example, a papal visit, a concert by a famous musical group, and so on — or it may have advantages in situations where there may be a long term municipal or military establishment such as those which are found in the high Arctic where permafrost is found and sewage disposal is a problem. In the operation of a gasifier and incinerator in keeping with the present invention, it is possible that there may be flame present in the primary chamber at the region of the primary chamber where the carbon stage of the incineration occurs. Thus, as the biomass sludge is reduced to ash in the region of the primary chamber 102 which overlies the secondary or afterburner chamber 104, there may sometimes be violent

flame action. So as to preclude undue disturbance of the biomass sludge which becomes very dry and powder-like, it is sometimes advisable to provide the additional dividing wall 136 as shown in Figure 8.

Also, in operation, a typical temperature differential between the temperature of the gases as they flow through the secondary or afterburner chamber 104 to the chamber

112 is about 100° C. Moreover, while the gases which exit the gasifier and incinerator of the present invention through the stack 114 may be quite hot, they will contain very little or no hazardous gases or gasified compounds such as dioxins or other volatile organic compounds whose presence in the atmosphere may be unwanted or may be legislated against. A typical concentration of volatile organic compounds may be considerably less than 10 ppm, which is generally acceptable in most jurisdictions.

Other modifications and alterations may be used in the design and manufacture of the apparatus of the present invention without departing from the spirit and scope of the accompanying claims. Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not to the exclusion of any other integer or step or group of integers or steps.