Plasma gasification reactors with modified carbon beds and reduced coke requirements   

This application claims the benefit of U.S. Provisional Application No. 61/403,123, filed Sep. 11, 2010, which is hereby incorporated by reference.

A companion application by some of the present inventors and others, assigned to the same assignee, and filed the same date as the present application (application Ser. No. ______, filed ______) entitled “Enhanced Plasma Gasifiers for Producing Syngas” (Atty. Docket No. 2011WP1NP) includes descriptions of plasma reactors and their operation combinable with the subject matter of the present application and said companion application is hereby incorporated by reference for such descriptions.

FIELD OF THE INVENTION

The invention relates to reactors that can be applied for gasification or vitrification of a wide variety of materials and which have reaction beds of carbonaceous material. Plasma gasification reactors are one form of such reactors to which the invention may be applied.

This background is presented to give a brief description of the general context of the invention.

Plasma gasification reactors (sometimes referred to as PGRs) are a type of pyrolytic reactor known and used for treatment of any of a wide range of materials including, for example, scrap metal, hazardous waste, other municipal or industrial waste and landfill material, and vegetative waste or biomass to derive useful material, e.g., metals, or a synthesis gas (“syngas), or to vitrify undesirable waste for easier disposition. (In the present description “plasma gasification reactor” and “PGR” are intended to refer to reactors of the same general type whether applied for gasification or vitrification, or both. Unless the context indicates otherwise, terms such as “gasifier” or “gasification” used herein can be understood to apply alternatively or additionally to “vitrifier” or “vitrification”, and vice versa.)

PGRs and their various uses are described, for example, in Industrial Plasma Torch Systems, Westinghouse Plasma Corporation, Descriptive Bulletin 27-501, published in or by 2005; a paper by Dighe in Proceedings of NAWTEC16, May 19-21, 2008, (Extended Abstract #NAWTEC16-1938) entitled “Plasma Gasification: A Proven Technology”; a paper of Willerton, Proceedings of the 27th Annual International Conference on Thermal Treatment Technologies, May 12-16, 2008, sponsored by Air & Waste Management Association entitled “Plasma Gasification—Proven and Environmentally Responsible” (2008); U.S. Pat. No. 7,632,394 of Dighe et al., issued Dec. 15, 2009, entitled “System and Process for Upgrading Heavy Hydrocarbons”; a U.S. patent application of Dighe et al., Ser. No. 12/157,751, filed Jun. 14, 2008, entitled “System and Process for Reduction of Greenhouse Gas and Conversion of Biomass”, (published patent application 20090307974, Dec. 17, 2009), and Dighe et al. patent application Ser. No. 12/378,166, filed Feb. 11, 2009, entitled “Plasma Gasification Reactor”, (published patent application 20100199557, Aug. 12, 2010), all of said documents being incorporated by reference herein for their descriptions of PGRs and methods practiced with them.

It is known to set up and operate such PGRs with a carbonaceous bed in a lower part of a reactor vessel where the bed is arranged with plasma torches that elevate the bed temperature (e.g., to at least about 1000° C.) for thermal reaction with material added that is to be gasified or vitrified. Although there have been suggestions that carbon material for such a carbonaceous bed can be of a variety of other carbon bearing materials, there has in the past been a heavy reliance on the use of coke for such purposes as it is of about 90% pure carbon and has chemical, thermal, and strength properties that are favorable for many processes that are performed in such reactors. “Coke” is a term for a product of a fossil fuel e.g., coal or petroleum, subjected to drying, e.g., by baking, to drive off volatile constituents.

While the carbonaceous bed is an important component in the operation of a PGR, another known form of a gasification reactor is a gasifier utilizing a carbonaceous bed (of coke) but without utilizing plasma torches. The carbonaceous bed of such a reactor serves all the same functions as it does in a PGR with respect to the distribution of gases and the movement of molten materials. However, in addition, the carbon bed also serves to provide the thermal energy for gasification that would otherwise be provided by a plasma torch. A carbonaceous bed of such a reactor may be initially activated to a temperature for gasification by, for example, brief ignition of natural gas supplied to the bed.

Among the desirable criteria of the carbonaceous bed of PGRs and other reactors is that it be of particles irregular enough in shape to leave voids allowing gases to flow to the surface of the particles where reactions occur and gaseous reaction products to rise from the bed. The voids also allow molten metals and other liquids resulting from the process performed in the reactor to flow down to a metal and slag exit port. Voids of the bed and porosity of particles of the bed can contribute to desirable reactions and flow characteristics. Coke allows formation of such a bed and has sufficient strength of the particles for many processes not to be crushed during operation by the burden of working material deposited on top of the bed.

Despite the satisfactory performance that coke very often provides, it is sometimes the case that factors such as the expense of coke and concerns about its manufacture and use impacting the environment, as it is a fossil fuel, may prevent or limit its use in some processes at some reactor sites.

In the known prior art, U.S. Pat. No. 4,828,607 issued May 9, 1989, to Dighe et al., and entitled “Replacement of Coke in Plasma-Fired Cupola”, discloses a process that includes providing coal instead of coke, although still a fossil fuel, along with metal scrap and a fluxing material, to a plasma-fired cupola to produce iron or ferro-alloys. This evidences fairly early interest in minimizing coke usage in such applications although coke still remains the only form of carbon material that is widely used in operating reactors with carbonaceous beds. Wood or wood products (e.g., charcoal) are known carbon sources but have not found practical application as significant coke replacements in pyrolytic reactors.

SUMMARY

This summary briefly characterizes some aspects of the invention. Statements made are intended to be generally informative as to examples of the invention although not as definitive as the appended claims.

The invention provides, in various forms and by various processes, reactors and carbonaceous beds that require less coke than has been generally the case in the past. The carbon required can be obtained, at least in part, by carbon bearing alternatives to coke. Examples include beds that have at least about 25% (it can be significantly greater up to 100%) of the carbon content of the bed made of non-coke units that may be either, or both, wood blocks of natural wood or bricks comprising carbon-containing particles or fines and one or more binders and possibly a catalyst. Any such materials may be applied in a bed also including coke (although coke may be replaced completely in some applications). Carbon of the bed may additionally include, if desired, for example, if included in feed material to the carbonaceous bed, other non-coke materials such as raw coal (anthracite or bituminous), charcoal, or process materials including biomass (any carbon bearing materials).

Some embodiments of the invention take advantage of, and make use of, carbon material resulting as waste from any of a variety of other processes (e.g., carryover from any gasification reactor, fly ash from coal fired boilers, as well as others) which contribute to lessening requirements for coke in the bed. For one thing, they may be advantageously used as particles or fines in making the above-mentioned bricks. Such waste carbon materials may also be included in the feed stock to the reactor without being formed into bricks.

In connection with the use of extraneous waste carbon materials referred to herein it is immaterial whether those carbon atoms were ever previously in any form of coke. Therefore, the examples of the beds including non-coke units such as wood blocks and bricks with carbon material generally intend that the carbon bed have such non-coke units in a range of about 25% to 100% and about zero to 75% coke (referring to quantities of carbon atoms in the respective materials), where some of that 0 to 75% coke may be replaced by carbon of feed materials (other than the mentioned non-coke units), up to, e.g., about 10% of the total carbon. In some processes it may be favorable to start up a reactor with a bed of coke as has been formerly used. As operation continues after start-up, and the coke is consumed, increasing quantities of the non-coke units can be added.

The carbonaceous beds with the non-coke units of the above examples are believed suitable for use in a variety of pyrolytic processes. Just by way of a more particular example, they are suitable for, but not limited to, use in a PGR process of gasification of biomass or municipal waste to produce syngas.

The non-coke units are of varied or irregular shape and size to leave voids in the bed as necessary for gases to flow to carbon reacting locations and to rise within the bed and exit from the bed. Also, the voids are for allowing liquids, including molten slag and molten metals, to descend through the bed to an outlet at the bottom.

The mentioned non-coke units are believed superior to coke alternatives such as anthracite coal or charcoal as significant bed constituents in achieving better properties, closer to those of coke, for efficiency of reactions while maintaining strength to support working material without being crushed, which tends to close voids in the bed and impede desirable reactions and flow of molten slag and metals through the bed. Conventional charcoal briquettes, for cooking, are considered relatively weak in strength compared to coke or the non-coke units presented here.

In addition, the non-carbon components in the coke replacement units (i.e., the mentioned blocks or bricks) can be engineered to be useful additions to gasification and/or vitrification processes. Wood, as an example, typically contains about 35-40% by weight of oxygen, which can replace a portion of the oxidant being fed to a gasifier as a gas. Also, in vitrification or in gasification processes in which the feed contains inert materials which will exit the process as slag, additives which are needed to flux or modify the inert materials to produce the desired slag chemistry can be added instead to the brick formula along with the carbon source. For example, one or more binders in the bricks can be selected to satisfy the requirements of those additives where cement type binders will typically provide calcium for fluxing properties while silicate binders will serve as modifiers to the slag chemistry.

In metal melting applications, where the slag chemistry is an integral part of the final metal chemistry, the brick formulation can be engineered to incorporate slag making ingredients, resulting in less need for a separate feed of those ingredients and to provide more intimate contact of those materials with the carbon reductant.

In addition to the foregoing, the present invention includes, either in addition to or independent of the use of the mentioned non-coke units, various other ways of constructing or operating a reactor that can contribute to a lessening of the amount of coke required for the carbon bed (as well as consuming some otherwise waste materials). These include any of the following: Using spent potliner material from the aluminum industry. The carbon liner of the potliner is very high in carbon content. It is joined with refractory material, such as a ceramic. Spent potliner material is a listed hazardous waste that is difficult or expensive to dispose of. By the present invention, there are a number of ways to use the material in reactor carbon beds. The carbon can be applied as particles in the above mentioned bricks (as any other carbon containing material can) but potliner carbon material may also be used in particles or chunks that substitute for coke in the bed. The refractory part of the potliner (sometimes available from aluminum makers intermixed with the carbon liner, or separately) can be placed, in particles or chunks, either in the bricks or otherwise in the bed in addition to the carbon and be a beneficial slag additive (when used in a quantity that meets composition requirements for the reactions occurring in the bed). Providing a reactor with a charge bed (or feed bed) support that is also a gas distributor and a slag screen. This support grid can be disposed horizontally across the reactor inner volume below one or more main feed chutes and above the region in which plasma heated gas is developed. The grid, in some embodiments, has closely spaced grid elements of refractory material with cooling to prolong life, e.g., by inner passages for water cooling in the interior of the grid elements. Operation of the reactor is conducted so that the cooling allows the refractory to survive for a useful period of time but without slots or other grid openings becoming closed by freezing slag or metal within them. Hot gas flow from the region below the grid, through the grid openings, will gasify charge bed material on top of the grid and resulting slag from the gasified charge bed material will flow down through the openings. (In this particular example, very little, if any, of the ungasified charge bed material would pass through the small openings of the grid.). This arrangement allows use of less carbon bed material (coke or otherwise) as well as embodiments of desirable reactors and their operation with no carbon bed. Furthermore, and more generally, any support for charge bed material above a carbon bed, including a support with openings that allow some appreciable amount, but not all, of the charge bed material to fall onto the carbon bed, will still, to some extent, lessen the burden of the charge bed on the carbon bed and, hence, reduce the strength required for the carbon bed materials to support the charge bed. This, in turn, allows selection from a wider range of carbon material particles or non-coke units, including those that may not have the strength of coke particles. A PGR with innovative feed arrangements configured to enhance a supply of non-coke feed materials that can be relatively continuous and dependable. An example in this category is the use of an eductor for carbon fines injection into a carbon bed. Other reactor configurations that can contribute to less consumption of carbon in the bed, such as by permitting operation at a lower temperature at a plasma torch nozzle. A PGR configured with one or more feed chutes at a height no greater than just above the top level of a charge bed is a form of reactor of general utility as well as having a capability to be operated with a lower bed temperature if desired. In some instances, reactors are operated to gasify feed materials that are uncompacted and in pieces that are diverse in size and weight. (For example, shredded biomass or municipal waste including paper products.) A higher percentage of the light weight feed material pieces can be reacted by hot gases rising up from the charge bed where the feed chutes are close to (or under) the charge bed surface to a greater extent than in prior practice in which feed chutes have been located well above the charge bed in an upper section of the reactor and where more of the lighter pieces of feed material did not descend enough to reach sufficiently hot gases for reaction. A large percentage of the lighter pieces may exit the reactor with the exhaust gas in that case. In the new arrangement, any light feed materials that do not descend directly onto the charge bed are more certain to float immediately above the charge bed and reach a high temperature from gases rising from the nearby charge bed so they are gasified. This contributes to the top gas, or syngas, production of the reactor and permits lower demands on the carbon bed, as long as the carbon bed temperature would still be sufficient to maintain molten slag flow. This arrangement can be applied, for example, and without limitation, where the reactor also has, at about the same elevation as the charge bed surface and the feed chutes, one or more gas inlets for oxygen (air) that takes part in reactions of the floating feed material and is regulated to assist in forming carbon monoxide from that feed material.

The carbon beds described in the foregoing examples are generally applicable to gasification (or vitrification) reactors with a fixed or stationary bed but are not necessarily limited thereto as they may also be applied to fluidized beds. In addition, the carbonaceous beds of other thermal reactors besides PGRs may be similarly modified to reduce coke requirements.

The foregoing is only to briefly describe some aspects of some examples of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevation view, partly in section, of an example of a plasma gasification reactor in accordance with the invention;

FIG. 2 is a partial elevation view of an example of a carbonaceous bed,

FIG. 3 is an elevation view of an example of a bed with non-coke wood blocks;

FIG. 4 is an elevation view of an example of a bed with non-coke carbonaceous bricks;

FIG. 5 is a block diagram of a system that is one example of the use of non-coke carbon in a PGR;

FIG. 6 is a partial, sectional, elevation view of a PGR with an example of a plate or grid supporting a charge bed;

FIGS. 7A and 7B are, respectively, elevation and plan views of an example of a PGR with feed chutes at or near the top of a charge bed; and,

FIG. 8 is a schematic diagram of an example of a system for injecting particles or fines into a carbon bed of a gasifier.

FIG. 1 is an example of a PGR of general capability for gasification and vitrification of various process materials. One manner of operating such a PGR is for gasifying material to produce a syngas from the feed material. The feed material may include, as examples, anyone or more of materials such as biomass, municipal solid waste (MSW), coal, industrial waste, medical waste, hazardous waste, tires, and incinerator ash. The syngas can contain useful amounts of hydrogen and carbon monoxide for subsequent use as fuels.

The reactor of FIG. 1, shown in full elevation in its left half and vertically sectioned in its right half, has a reactor vessel 10, generally of refractory-lined steel (the lining is not specifically shown in the drawing), whose prominent parts include or contain a carbonaceous bed 20 above which is a section for a charge bed 30 of process material, such as biomass, with a freeboard region 40 above the charge bed 30, and the freeboard region extends up to a roof 50.

The portion of reactor vessel 10 enclosing the carbonaceous bed 20 has one or more (typically two to four) nozzles 22 (sometimes alternatively referred to as ports or tuyeres) for location of a like number of plasma torches 24 (not shown in detail) for injecting a high temperature plasma heated gas into the bed 20. The plasma nozzles 22 may additionally be arranged to introduce additional process material that may be desired, such as a gas or liquid (e.g., steam) or some solid particulates, for reactions within the bed 20 along with the material of the charge bed 30. (Such additional process material may also be added directly to the bed 20 by nozzles not having a plasma torch.) The reactor vessel 10 also has at the bottom a molten slag and molten metal outlet 26.

A part of the reactor vessel 10 that is around the charge bed 30 and above the carbonaceous bed 20 further includes some additional nozzles or tuyeres 32 that, usually, do not contain plasma torches but provide for the introduction into the charge bed 30 of further process material, if desired, such as in the form of a gas, liquid, or solid particulates.

The upper feed section or freeboard region 40 of the reactor vessel is arranged with one or more process material feed chutes 42. Here, one feed chute 42 is shown in a side wall. More generally, one or more feed chutes can be at any locations in the side wall of the reactor vessel 10 or the roof 50 for depositing feed material initially onto the carbonaceous bed 20 as well as during operation of the reactor to add to the charge bed 30 as its process material is diminished by the reactions that take place in the reactor.

The roof 50 encloses the top of the reactor vessel 10 except for one or more outlet ports 52 for gaseous reaction products (e.g., syngas) to exit from the reactor vessel 10. Gas outlet ports may be variously provided either in the roof 50 or the sidewall of the reactor vessel 10. At least where feed material through any feed chutes includes particulates, it is usually desirable for any gas outlet ports 52 to be located enough away from the point of entry of feed material to avoid excessive exiting of unreacted particulate matter through the gas outlet ports.

The PGR configuration shown in FIG. 1 is generally in accordance with an example embodiment of the copending application of Dighe et al., Ser. No. 12/378,166, filed Feb. 11, 2009, published patent application 20100199557, Aug. 12, 2010, which, among other things, includes a generally upwardly and continuously expanding conical wall 12 of the reactor vessel 10 which can provide beneficial gas flow characteristics in the charge bed 30 and the freeboard region 40. Said application is incorporated herein by reference for its description of reactor configurations, including variations of that shown in FIG. 1, and their operation. The present invention, however, is not restricted to reactors with such configurations.

PGR practice, and practice with other types of pyrolytic reactors with a carbonaceous bed, have used, at least almost always, a bed that is substantially all of coke. Coal is sometimes mixed with the coke but any other carbon bearing material has been very minor and incidental to the structure and operation of the reactor. Coke has a composition with a high content of carbon (about 90% by weight), it can be formed in various shapes and sizes so particles of coke, e.g., with average cross-sectional dimensions of about 10-15 cm., can have ample carbon surfaces for reactions, provide voids for upward gas flow and downward flow of liquids, and strength sufficient to maintain voids throughout operation. The full size distribution or variation of particles of a carbon bed with coke is preferred to be greater than about 5 cm. to prevent the void spaces from being too small for proper liquid flow and less than about 25 cm. to minimize material handling issues. Where up to about 10% of the carbon in the bed 20 is of finer carbon particles (e.g. injected directly into the bed 20), adequate voids for liquid flow can be maintained.

In the PGR of FIG. 1, the carbonaceous bed 20 (hereinafter sometimes referred to as a C bed) includes non-coke material to a significant extent, during at least some of its operation, such as at least about 25% of the C atoms of the bed being not in coke units. For that reason, in FIG. 1, the carbonaceous bed 20 is further identified by the legend “C BED WITH NON-COKE”.

Examples of non-coke materials for use as at least part of the bed 20 are natural wood blocks and, also, bricks including particles of a carbon-bearing material with one or more binders. The non-coke materials are formed in particles or units of irregular size and shape so that when placed or assembled in a bed they have exposed surfaces resulting from voids that occur between some parts of them. The non-coke units of the bed 20 are generally of the same size range as the coke particles for reactor beds as discussed above, but are not limited thereto.

An initial carbonaceous bed 20 of a PGR, such as that of FIG. 1 is generally established in the bottom of a reactor vessel 10 prior to operation of the reactor with feed material or powered up plasma torches. Then, once an initial bed 20 is in place, operating with active plasma torches 24 and depositing feed material to form a charge bed 30 commences. Most such processes are substantially continuous over a period of at least many hours with additional feed material applied, perhaps continuously or at least in frequent intermittent quantities. The reaction of the plasma heated gas with the C bed 20 inherently depletes carbon from the C bed. However, the rate at which the carbon in the bottom carbon bed 20 is consumed is much lower than the rate at which the feed material is gasified. Therefore, an initial C bed 20 only requires minor additions of carbon material in the course of processing a much larger amount of feed material. Some aspects of adding carbon material to an initial C bed are described below.

Typical operations, such as for production of a syngas, include forming a charge bed 30 on top of the C bed 20 by depositing feedstock through the feed chutes 42 where the feedstock may be, for example, biomass, municipal waste, coal, or mixtures thereof. During or after formation of an initial charge bed 30 that extends above the additional nozzles 32, those nozzles are used to inject fluids such as air, oxygen, or steam into the charge bed 30 while the plasma torches 24 operate with a torch gas, such as air, and, perhaps some steam or other fluid or small particles of solids are injected into the C bed 20 through the nozzles 22.

For production of syngas, to exit through the exit ports 52, it is desirable to operate in a manner to produce carbon monoxide and hydrogen. Carbon dioxide may be produced to some extent but carbon monoxide can be favored under conditions that limit air or oxygen in relation to carbon in the reactor.

As mentioned above, in such an operation, the reactor will consume carbon of the C bed 20 and the carbon is desirably replenished so the quantity of carbon is not appreciably reduced. A way of doing that in the past, for a coke bed, has been to add coke to a feedstock charge bed on top of the coke bed. For example, in production of syngas from biomass material, there has been coke added along with, i.e., mixed with or in alternate batches with, biomass. Processes have been performed in which such added coke amounts to about 5% by weight of the total of feedstock including coke.

Such carbon replenishment is also a consideration where the C bed 20 is to include non-coke material as described. Consequently, in accordance with one embodiment, the carbon material supplied to replenish the C bed 20 can be similar to the nature of an original C bed with non-coke and include at least about 25% of the added carbon being from non-coke materials. In some instances, for example, because of lower carbon content (compared to coke) of non-coke units that may be used, it would be desirable to make the total material of the C bed a greater quantity than in prior operation with just coke so there is an equivalent amount of carbon atoms in the bed.

The C bed improvements described herein, such as the use of wood blocks or carbon containing bricks as some or all of the bed (in lieu of coke), can also be applied to C beds in reactors without plasma torches. In such reactors, a C bed may be initially activated by ignition of a fuel, such as natural gas, supplied for a brief time as formerly practiced with a 100% coke bed of such a reactor.

FIG. 2 shows an enlarged view of just a part of the apparatus of FIG. 1. The C bed 20 of FIG. 1 is shown in some additional detail to show individual particles 21 within the bed 20 and voids 23 occurring within the mass of the particles 21 due to the mixed size and irregular configurations of the particles. The size and shape of the particles 21 can vary widely. Just for example, the particles 21 may have an average of their dimensions in a range of from about 5 cm to about 25 cm, of which about 10 cm to 15 cm is an example of the average size of coke particles and about 10 cm to 25 cm for the average size of non-coke particles.

FIG. 3 shows an additional enlarged portion of a C bed 120 with particles 121 and voids 123 where the particles 121 are natural wood blocks.

The natural wood blocks or particles 121 are, for example, waste from a prior industrial source process such as the manufacture of wood pallets or are formed especially for use in the C bed 120. It is generally unnecessary to dry or treat the wood block particles (such as by charring any surface portions of them before applying them to the bed 120), although either or both some drying and charring can be performed if desired before placement in the bed 120. The wood block particles 121 can be added to a bed 120 that includes coke particles with or without intermixing the materials to produce any particular degree of homogeneity.

The wood for the wood blocks 121 can be of various plants or trees. Hardwoods such as oaks are one suitable wood material. Such woods, and the wood blocks 121, have a typical carbon content of about 50% by weight.

FIG. 4 shows an additional enlarged portion of a C bed 220 with particles 221 and void 223 where the particles 221 are bricks formed of carbon containing particulate material (e.g., wood chips, carbon fines, or a mixture of carbon containing material particulates). The bricks 221 may sometimes be referred to as “briquettes” but are distinct from common charcoal briquettes as explained further below

FIGS. 2-4 are primarily to give just a rough idea of the appearance of the particles and voids referred to. The respective C beds 20, 120, and 220 need not always fully occupy the bottom portion of a reactor. Normally, any of the carbon beds discussed in a plasma reactor would extend up at least past the location of plasma torches, such as one that may be located in a plasma nozzle 222 of FIG. 4.

The bricks 221 of FIG. 4 can be molded, without any applied pressure or heat being necessary, of a mixture of the carbon particulates with one or more binders. Portland cement is one suitable binder. Other constituents may be included, for example as binders, or as fluxants or glass formers, and/or as catalysts. Some examples of bricks 221 have been formed of a mixture that included, by approximate weight percent, 40 parts carbon fines, 8 parts Portland cement, 4 parts bentonite clay, 4 parts sand (SiO2), 12 parts sodium silicate, and 32 parts water. Such bricks have been made with a carbon content of about 66% by weight on a dry basis.

Other bricks 221 have been formed of a mixture that included, in approximate weight percent, 23 parts carbon fines, 21 parts Portland cement, 11 parts sand, and the balance (45 parts) water.

The bricks 221 can be molded to any size (similar in general size to coke particles) and shape, with characteristics to provide desirable voids in the bulk bed. It is not a necessity to vary the size or shape of bricks formed for use as bed particles such as the particles 221 of FIG. 4. It can be suitable, as well as economical, to use a single mold size and shape if desired. Same sized cylindrical (or spherical) units will inherently provide voids in the bed. Multiple-sized units can also be made and used together, if desired, preferably with a cross-sectional size distribution of about 5-25 cm. for most all the units and only a minor amount of any smaller carbon bearing units that tend to reduce voids.

Pressure and/or heat are also suitable means to form bricks with sufficient strength with a low quantity of, or no, binding agents. Generally speaking, and without limitation, examples of bricks formed with a cement binder are favored where the strength of the bricks is important.

The carbon particulates in the bricks 221 can be “carryover” particles from a gasification reactor and in this way provide a means of recycling carbon otherwise lost to the process resulting in increased carbon utilization and therefore higher efficiency. Carryover particles are unreacted or partially reacted particles that exit a reactor with gases from the reactor. They are generally desirable to be minimized but some will almost certainly result from any gasification process. The carryover particles can be made use of as part of the non-coke content of a C bed in bricks or introduced into a reactor as part of the feed material (at chutes such as 42, FIG. 1) or otherwise (e.g., through plasma nozzles 24 or nozzles 32 of FIG. 1).

In general, the carbon particulates (or “fines”) used in making the bricks 221 are particles having average cross-sectional dimensions in a range of from about one micron to one centimeter and collectively have a total weight percent of carbon of at least about 50%. The average size range mentioned is not to exclude particles outside that range; particles finer than one micron can be quite suitable.

Combustion processes including boilers and incinerators also generate carryover particles such as fly ash and these materials may contain useful quantities of carbon that may serve as a source of carbon for carbon bed bricks. In addition, the properties of fly ash are also advantageous to the brick forming process allowing a reduction in the amount of calcium based cement binders that is needed.

The addition of materials to the bricks 221 which behave as catalysts, such as, but not limited to, nickel or iron, is another advantage of the bricks over coke alone as the carbon bed material. In this manner the brick can be engineered to provide not only a functional source of carbon to the plasma gasification process and the fluxing agents needed to properly vitrify the inert materials contained in the feed being gasified, but also catalysts to cause certain desirable chemical reactions to occur.

One example of a catalyst inclusion in the bricks 221 is an addition of nickel or iron to the bricks on the order of a few percent by weight to catalyze the C+NO reaction to reduce the NO in the syngas to N2+O2. This is especially important in bioreactors converting syngas to liquid fuels. Formerly such catalysts, when used to minimize NOx, had to be added with the feed material to the charge bed.

The following table gives additional examples of formulations for non-coke bricks, such as the bricks 221 of FIG. 4.

TABLE I For- For- For- For- For- For- Range mu- mu- mu- mu- mu- mu- Constituent (wt %) la A la B la C la D la E la F Carbon 40-95  65  70 60 41 45 80 Silica 0-30 6.5 7-14 10 19 15 Calcium Carbonate 0-25 Fly Ash 0-40 10 20 Portland Cement 0-20 13 39 20 Potassium 0-20 8-14 20 Silicate Cement Aluminum 0-20 5 Silicate Cement

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