An apparatus and a process for generation of syngas from solid fuel with steam

Abstract

A gasification apparatus produces syngas from waste materials without oxygen. The gas generator features a gas crossflow and up-flow design with drying, pyrolysis, and carbon reaction zones. A furnace heats gas from the gas generator, adding steam and heating it to 800-950°C for high methane syngas or 1000-1050°C for low methane syngas in a convective or convective and radiant coil. The hot product gas supplies the generator's heat needs via a manifold, while excess gas enters a heat recovery boiler to produce steam for reforming. The syngas primarily contains CO and H2, with minimal CH4, H2O, and CO2, offering high concentrations of valuable components. The apparatus eliminates tar and higher hydrocarbons, is fully scalable, and adjusts methane content by controlling gas flow through the coils while meeting the heat demands of all zones.

Description

AN APPARATUS AND A PROCESS FOR GENERATION OF SYNGAS FROM SOLID FUEL WITH STEAMFIELD OF THE INVENTION

[0001] The present invention relates to production of fuel gas from solid fuels such as farm waste, animal manure, municipal solid waste, plastic waste, peat, lignite, coal. Specifically, the invention relates to a gasification apparatus to convert the solid fuels such as biomass, Manure, Municipal Solid Waste including plastic, forest waste and coal to fuel gas and process for producing a fuel gas, either high in methane content or a low methane content gas commonly termed as syngas - a mixture of carbon Monoxide and Hydrogen containing minor quantity of carbon dioxide, methane, and water vapor. The utility of syngas is higher for syngas with H2 / CO ratio higher than one; because such syngas will yield more of the desired synthesis product such as green hydrogen, methanol, FT Hydrocarbons or DME - Dimethyl Ether.BACKGROUND OF THE INVENTION

[0002] The quality of the syngas is determined by proportion of CO + H2as well as impurities of CO2, H2O, and hydrocarbons such as CH4, C2H4etc. Heavy hydrocarbons commonly referred to as tar are particularly undesirable due to multiple equipment problems downstream from the gasification system. For power generation application higher methane content is an advantage; while for synthesis applications such as methanol, FischerTropsch etc. low methane content is desirable. Syngas quality is strongly dependent on the feedstock material, gasifying agent (O2, Air, H2O, CO2), temperature and pressure inside the reactor, and design of the reactor.

[0003] Gasification of waste materials is a thermochemical process, where thefeedstock is heated to high temperatures. During heating as the solid temperature rises allfeed moisture evaporates (around 100-150 °C, further heating to temperature higher than 300 °C causespyrolysis. Pyrolysis results in the release of volatiles - Tar and Gases from waste solid materials, about 70-80 % of the material is vaporized leaving behind char. Char contains carbon and any ash (inorganic compounds) entering with feed.

[0004] The chemistry of gas generation is explained in words in the last paragraph. It can be more succinctly expressed by the following sequence of reactions.In drying zone Wet Solid-> Dry Solid+ Steam - (1)In pyrolysis zone Dry Solid -> Char + Tar + Gases - (2)The gases include CO, CO2, H2O, CH4, C2H4, C2H6, CaH , CnHmOIn char, carbon reaction zoneC + Steam - CO + H2. (3)

[0005] The above four reactions demand heat to proceed from left to right. This demand of heat is a major challenge of gasification system design. In the earliest gasification system, the feed was partially burnt to provide the heat demand of reactions 1 -4. If air is used for providing oxygen required for partial combustion, then the product fuel gas is diluted by nitrogen contained in air. Therefore, many gasification systems use oxygen for partial combustion, this requires additional expense due to cost of oxygen.

[0006] Prior art also teaches use of a circulating solid to transfer the heat of combustion to the gas-generator; this arrangement avoids contamination of fuel gas by CO2 a product of combustion and the additional cost of oxygen. The solid - sand, dolomite or limestone is heated by intimate contact with burning char (solid). The solid thus heated is transferred to the gas generator to provide the heat of reactions 1 -4. When biomass is the feedstock, the peak combustion temperature of solid must be maintained below 850-900 °C (about 1600 °F) to avoid clinker formation; the clinker formation is due to potash content of biomass. This peak combustion temperature limits the temperature to which the circulating solid can be heated and therefore also the peak temperature in gas generator. US patent US3985519 represents one of the earliest patents using circulating solid to supply the heat demand of gas generator (reactions 1-4). US7760388B2, US8771388B2, US10443005B2,US10653995B2 and US11066612B represent circulating solid as a means of isolating products of combustion from gas product.

[0007] US8100992B2 uses another approach to transfer heat of combustion to gas generator. The gas generator vessel is placed in the path of combustion products. The ceramic walls of the chamber are heated by the combustion products and the ceramic wall in turn heats the gasifier vessel; in this mode the temperature will reach around 800°C. After separation of gas, it comes in indirect contact with flue leaving the gasification chamber as a result after separation from the solid gas temperature will rise a little further to 850 °C. Maximum temperature reached by gas is a limitation shared by this patent with the circulatingsolid patents described in the last paragraph. Another limitation of US8100992B2 will be the largest scale the system can be built. This method of providing heat of gas generation reaction depends on heat transfer from wall through the solid in contact with the wall. However, solid away from the wall near the centre of gas generator will receive very little heat; thereby limiting the throughput of solid processed.

[0008] Patent US7763088B2 uses a circulating sand as the heat transfer medium and the patent specifies peak temperature reached during gasification as 1300° F (about 700° C). Milena gasifier of ECN operates on similar sand circulation and results of biomass gasification have been published by ECN in numerous publications. A van der Drift et al1publication includes performance of the circulating sand indirect gasifier. The char combustor temperature is listed at 870 °C and gas generator temperature at 800 °C. The product gas composition for the circulating sand gasification is compared with the direct oxygen & air blown gasifier in another ECN publication by R. W. R. Zwart2it is reproduced in Table 1 below.Table 1. Gas Composition, Prior Art1"Milena Gasification Technology for High Efficient SNG production from Biomass" A van der Drift, C. M. van der Meijden, H. Boerrigter; 14thEuropean Biomass Conference and Exhibition, Paris France. October 20052"Oil-based gas washing - flexible tar removal for high-efficient production of clean heat and power as well as sustainable fuels and chemicals" ECN publication ECN-V-09-025, September 2009

[0009] Note the indirect gasification results in lower CO2, and higher CO + H2, tar and CH4. More fuel and less inert. The gas composition listed above for steam blown case is shown after OLGA tar removal process. The gas priorto OLGA tar removal process contained about 5-10% tar.

[0010] WO 2021191924A1 by the present inventor teaches a method of eliminating tar by the following reforming reactions:The heat demand of these reforming reactions 5 and 6 supplied by burning part of thepyrolysis gas from generator by oxygen. Thus, in this case the carbon dioxide content of the gas product will be close to that shown in Table 1 for oxygen and steam blown gasifier or about 25-30%. The published literature would indicate a high carbon dioxide content in the product gas.SUMMARY OF THE INVENTION

[0011] Four prior art limitations have been recognized; the first limiting gas maximum temperature to 800-850 °C will result in very low conversion by reactions 5 and 6 leading to significant tar in product; this conclusion is supported by data in Table 1. Second and thirdlimitation is for partial combustion as a method to provide heat demand of gas generation reactions; in this case the product gas is expensive due to cost of oxygen and it contains high concentration of carbon dioxide. The fourth limitation is for providing heat through the wall of the gas generator taught by US8100992B2, the solid near the wall gets the heat however solid away from the wall remains cooler and does not participate much in the gas generation reactions. As capacity of gas generation system increases, the diameter of gas generator increases, this in turn increases the quantity of solid away from the wall and therefore not generating enough gas. This factor ultimately limits the largest capacity possible, hence this method of providing heat is not scalable.

[0012] The present invention overcomes the limitation of the prior-art documents and provides a gasification apparatus and process for producing syngas from solid fuels. Figure 2 shows the gasification apparatus of present invention, it includes a gas generator 100, a furnace 200 which contains a first heat transfer coil 210, and a boiler 300 which includes a third heat transfer coil 310. The gasification apparatus disclosed herein is a fully scalable equipment; very large throughput gasification system can be designed following the proposed method.

[0013] The invention overcomes the maximum temperature limitation of the prior-art documents and provides a gasification apparatus and process for producing syngas without tar and higher hydrocarbons from waste and solid fuels. A furnace is placed near a gas generator to supply the heat needed by the gas generator. Gaseous product of the gas generator is circulated through the furnace to achieve temperatures as high as 1000 °C. Since solids are not circulated through the furnace, the temperature limitation due clinkering is absent. Such high temperature reforms tar and higher hydrocarbons formed in the gas generator; simultaneously producing additional desired CO and H2by reactions 5 and 6.

[0014] The furnace burns a portion of waste feed in a conventional combustion in air with primary and secondary air to generate very hot flue gas (temperature of 1200-1300 oC). The hot flue supplies heat to circulating gas in heat exchanger tubes supplying heat needed inthe gas generator for reactions 1 -4 and supplying heat needed by the tar and methane contained in the gas for reactions 5 and 6. The furnace can additionally use unreacted char from the gas generator as supplementary fuel to completely utilize carbon in the feedstock.

[0015] The hot product gas exiting the furnace has sufficient heat to produce the steam needed for reactions 3, 5 and 6. These three major pieces of equipment - the furnace, the gas generator, and boiler- constitute the apparatus to carry out the process, namely gas generator, gas heater contained in the furnace and heat recovery boiler. Figure 2 shows the minimum equipment constituting the present invention. Additional equipment can improve the overall efficiency of the apparatus and these include air-preheater, economizer to preheat water for heat recovery boiler and steam superheater; the additional equipment is not functionally essential but improves the overall efficiency. The additional equipment to be used will be obvious to a person proficient in the art

[0016] Further advantages and other details of the present subject matter will be apparent from a reading of the following description and a review of the associated drawings. It is to be understood that the following description is explanatory only and is not restrictive of the present disclosure.BRIEF DESCRIPTION OF THE FIGURES

[0017] To further clarify the advantages and features of the disclosure, a more particular description of the disclosure will be rendered by reference to specific embodiments thereof, which are illustrated in the appended drawings. It should be appreciated that these drawings depict only typical embodiments of the disclosure and are therefore not to be considered limiting of its scope. The disclosure will be described and explained with additional specificity and detail with the accompanying drawings in which:

[0018] Figure 1 illustrates a schematic device of a prior art reproduced from patent US7763088B2, where B is waste (biomass) feed and 50 is steam, S is circulating solid carrying the heat from combustion of char 30 to the gas generator 10.

[0019] Figure 2 shows arrangement of a tar-free, oxygen-free gasification apparatus in accordance with minimum required embodiment of the present invention; and shows only the three functionally essential equipment Gas Generator 100, Furnace 200 and Heat Recovery Boiler 300.

[0020] Figure 3 shows peak temperature reached in a gasification system of prior art and of the present invention.

[0021] Figure 4 Shows equipment and locations describing functional characteristics to be followed in the present invention.

[0022] Figure 5 shows functionally necessary as well as efficiency improving equipment used in furnace and typical temperature of the flue at different location in the furnace.

[0023] Further, those of ordinary skilled in the art will appreciate that elements in the drawings are illustrated for simplicity and may not have been necessarily drawn to scale. For example, the dimensions of some of the elements in the drawings may be exaggerated relative to other elements to help to improve understanding of aspects of the disclosure. Furthermore, the one or more elements may have been represented in the drawings by conventional symbols, and the drawings may show only those specific details that are pertinent to understanding the embodiments of the disclosure so as not to obscure the drawings with details that will be readily apparent to those of ordinary skilled in the art having the benefits of the description herein.DETAILED DESCRIPTION OF THE INVENTION:

[0024] FIG. 2. discloses a gasification apparatus according to embodiments of the present disclosure. It includes three major equipment, namely, a gas generator 100, a furnace 200 which includes a first gas heater 210 and a heat recovery boiler 300 that contains a steam generating coil 310.

[0025] A first portion of the waste material or solid fuel feed, feed-1 , enters the gas generator 100 through the feed hopper 110 at ambient temperature. It moves down the gas generator 100, while gas moves mostly from a second manifold 170 to a first manifold 160 across the solid. The second manifold 170 contains the hottest gas received from the furnace 200. Since there is no hindrance to the gas movement, some gas moves up the gas generator 100.As the solid fuel fed to the generator 100 moves down, it gets heated by the gas flowing across and up. As solid fuel heats up to a temperature of 100 °C and higher, it dries up by losing moisture. Drying is essentially complete once the temperature reaches 150 °C. Zone 120 in the gas generator 100 denotes this drying zone in which the temperature of the solid fuel rises from ambient to around 150 °C. The gas continues to heat the solid fuel, and as temperature of solid fuel rises to 300 °C and beyond the solid fuel pyrolyzes releasing gases, tar as well as chemically bound moisture. By the time the temperature of the solid fuel reaches 500 °C, it has lost 60-75% of its weight. Thus, the major weight loss by vaporizing away is essentially complete in the pyrolysis zone 130. As the temperature of the solid fuel rises to 600 °C and beyond the carbon in the solid fuel reacts with steam and carbon dioxide present in the gas producing CO and H2. Zone 140 in the gas generator represents this carbon reaction zone. Thus, as the solid fuel moves down the gas generator 100, it gets heated and converts to gas. Simultaneously as gas moves up the gas generator it cools down due to heat given up by it to the solid fuel and due to supply of heat demand of reactions 1 - 4. Any unreacted solid fuel is moved out of the gas generator through a opening or a hole 150 and a char screw 180. A gas blower 220 sucks gas from the first manifold 160 and delivers it to the furnace 200 for heating. The furnace 200 delivers the heated high temperature gas back to the second manifold 170 at a temperature ranging from 900-1050 °C. The delivery to the second manifold 170 may be at multiple locations and may be in different proportions along the second manifold 170. The proportion of hot gas delivered at different locationswill be determined by the heat demand of zones 120, 130 and 140 in the gas generator 100. The net gas generated by the gasification system continues beyond the second manifold 170 to the heat recovery boiler 300.

[0026] The Furnace 200 heats the gas from gas generator 100 sucked by the blower 220 to a temperature in the range of 900-1050 °C and delivers the hot gas to the second manifold 170 of the gas generator 100. The heat required to raise the gas temperature is generated by burning the remaining second portion of the solid fuel, feed-2, supplemented by burning of the unreacted char from the gas generator 100 delivered by screw 180. Depending on the final application of the syngas, often fuel gas streams may also be available. For example,if the application using syngas is generation of methanol, FT Hydrocarbons or DME - Dimethyl Ether; then the synthesis section commonly utilizes a synthesis loop recycling unconverted syngas back to synthesis reactor. The synthesis loop will purge a part of the recycle gas stream to avoid buildup of inert gases such as methane or nitrogen, or buildup of byproducts of synthesis. Raw syngas processed through membrane or PSA (Vacuum Pressure Swing Adsorption) purification will generate a pure hydrogen stream and a reject stream including CO, CH4and small amount of H2. If the furnace fuel is the application of the product gas, and the application calls for heat delivery temperature of 1000°C or higher, then the flue from the furnace can deliver the heat need of tubular coil 210. These are three syngas use examples, where substantial quantity of fuel gas is available as fuel for the furnace, in which case, the quantity of second portion of solid fuel required (feed-2) is reduced. The solid fuel and unreacted char are fed to the grate 230 of the furnace and burned by conventional primary air secondary air method. Depending on the capacity of the furnace and the furnace supplier, the grate 230 may be a travelling grate or vibrating grate or reciprocating grate; any of these types of grates burn the solid fuel efficiently while removing volatile gaseous matter from the solid. This volatile gaseous matter is burned in a long flame over the grate by the secondary air; any fuel gas stream if available, will also be burned over the grate. The ash generated is delivered to ash disposal area. The heat of combustion can be delivered to the gas circulating through the furnace via a second heat transfer coil 240 situated in the lower radiant zone of the furnace 200 and a first heat transfer coil 210 situated in the upper convective zone of the furnace 200. The coils 210 and 240 are tubular coils with gas from gas generator flowing inside them. Flue gas from combustion area of grate 230 as well as flame over the grate 230 passes on the outside of the first heat transfer coil 210; hence the term convective coil. If a coil is placed in the combustion area, it will receive heat radiated by the flame, hence the term radiant coil may also be used to refer to the second heat transfer tubular coil 240. If the target fuel gas product is high methane syngas, then optimal temperature range for maximum methane in product while minimum tar in the product is in the range of 800-900 °C, depending on the nature of waste feedstock. In this case, only the convective coil 210 will be used. If the target syngas is low methane syngas,then hotter gas temperature in the range 1000-1100 °C is required. In that case gas from convective coil 210 can pass to radiant coil 240. In both high methane or low methane cases, the total hot gas from the coils 210 and or 240 is divided into two portions. The first portion of around 60-70% of total gas is returned to the gas generator at the second manifold 170 to provide the heat needed by gas generator 100. The second portion is the net gas generated and it is delivered to the heat recovery boiler 300 for steam generation.

[0027] The heat recovery boiler 300 receives hot net gas product from the furnace 200 and reduces its temperature by generating steam required for reactions 3, 5 and 6. A third heat transfer coil 310, which is a convective tubular coil, is used for this purpose. Depending on the application of syngas, the boiler may 300 be sized to supply steam for reactions 3, 5 and 6 and it can generate extra steam to be used elsewhere.

[0028] The various reactions of the gas generation process take place in the gasification system in specific temperature range and either in the presence or absence of solid. Therefore, each reaction can be correlated to the location where it predominantly takes place. The following is a summary of reaction locations:Reaction 1 in the drying zone 120, reaction 2 in the pyrolysis zone 130, reactions 3 and 4 in location char reaction zone 140, reaction 5 and 6 in the first heat transfer coil 210, and or heat transfer coil 240.

[0029] As we have already seen, the first portion of the solid fuel, feed-1 , is fed to the gas generator at hopper 110. A second portion of the solid fuel, feed-2, is burned in the furnace 200 to supply the heat demand of the gas generator 100 as well as the heat requirement of tar reforming reactions taking place in coils 210 and or 240. If the application of the syngas is such that no fuel gas stream is available for the furnace; then feed-2 quantity required can be as high as 40% of feed-1. If a large quantity of fuel gas is available, then the feed-2 quantity required will be zero. Even in the case feed-2 is not required, the furnace still needs a grate 230 to burn the partially converted char from gas generator 100.List of Parts / zonesProcess Description:

[0030] The process for generation of syngas from solid fuel with steam according to the invention is now disclosed.

[0031] Syngas is a mixture of CO and H2 as major components while minor components include moisture, carbon dioxide, methane, and other minor components dependent on the feedstock used to produce syngas. Production of syngas from various solid feedstocks iswell known technology practiced for nearly a century, well documented since 1938-40. Many limitations of the technology are well understood, for example the feed moisture content should be in the range of 15-20%, any higher moisture severely restricts the throughput. Similarly, gas generators work well with briquetted or with lumpy materials as these materials have higher bulk density and pack well in the gas generator increasing its’ throughput. Furnaces for generation of heat by combustion of solid materials have even a longer history. Limitations on feed solids use in a furnace are also well understood and will be not be repeated here as the furnace burning solid material is a part of this invention. Feed preprocessing such as proper sizing of feed as well as sufficient drying of feed is assumed to be completed before it is used in the gas generator or the furnace.

[0032] A first portion of the solid fuel feed, feed-1 , enters the gas generator 100 through the feed hopper 110 at ambient temperature and moves down the gas generator 100 by gravity. A very large fraction of the solid fuel is converted to gas by thermochemical process in the gas generator 100; only 5-20% of initial solid fuel leaves the gas generator 100 as solid. Hot gas from furnace in the second manifold 170 travels across the gas generator towards the first manifold 160. The hot gas can also rise up the gas generator 100. The solid fuel in the gas generator 100 is heated by the hot gas; as the temperature of solid fuel increases, it goes through thermochemical changes. The first change is physical moisture adsorbed on the solid fuel is vaporized away. This drying step is essentially complete as solid fuel temperature rises to around 150 oC. This drying zone is represented as zone 120 in figure 4.

[0033] The temperature of the solid fuel continues to increase as its temperature rises above 300o C and the thermochemical change known as pyrolysis takes place. The solid fuel loses volatile gaseous matter including a part of its chemically bound moisture, tar and heavy aromatic hydrocarbons, oxygenated hydrocarbons, as well as smaller gas fragments such as CO, H2, CH4. The products of the pyrolysis are numerous and include most classes of organic chemicals. The composition of these organic chemicals changes as the heating rate of the solid changes; however, the composition of these organic chemicals is not of relevance for this invention. Depending on the nature of solid fuel, pyrolysis is considered mostly complete as a temperature around 500 oC is reached. For coal as solid fuel the endof pyrolysis temperature would be higher, depending on the grade of coal it could be as high as 800 oC or as low as 500 oC. The solid remaining after pyrolysis is termed as char due to its black color and it contains carbon as the predominant organic constituent and all inorganic matter commonly termed as ash. This pyrolysis zone in the gas generator 100 is shown as zone 130 in figure 4.

[0034] Further down the gas generator 100, as solid fuel temperature rises above 600-700 oC the char reacts with carbon dioxide and steam producing CO and H2. These reactions of char are hindered by the presence of ash components as the ash components physically block access of gaseous carbon dioxide and steam to the organic solid in char. Depending on the constituents in the inorganic components, it softens as the temperature is increased, further increase in temperature leads to melting of the inorganic components. As the ash softening point is reached, char lumps can form which will block access of gaseous reactants to organic component of char. Melting of ash leads to even larger lump formation; if lumps about % to 1 / 8 of gas generator diameter are formed, downward movement of solid fuel can be obstructed or stop. Although the reaction of steam and carbon dioxide with organic constituent of char occurs at higher and higher rate as temperature of solid increases; the ash softening point limits the highest temperature possible. The behavior of ash puts a practical limit on the extent of organic component of charthat can be converted to syngas in the gas generator. Zone 140 in the gas generator is this char reaction zone.

[0035] As char moves down the gas generator 100, the rate of conversion of organic component of char to syngas keeps slowing down as less and less organic matter is available for reaction. Optimal use of gas generator space requires removal of charfrom the gas generator 100; while it still contains a small quantity of organic component in the char. Char conveyor screw 180 removes less reactive char as it drops through the hole or opening 150 from the gas generator 100.

[0036] The conveyor delivers char to the grate 230 located at the bottom of the furnace 200. The grate 230 with its vibration / reciprocating or travelling action exposes different sides of the solid char to air. The oxygen in air being much more reactive than steam or carbon dioxide, most of the organic matter in char will be burned on the grate.

[0037] The furnace 200 delivers the heat needed by the reactions in the gas generator 100 — drying, pyrolysis, and char to syngas. This function is served by the hot gas delivered by furnace 200 to gas generator 100. However, it serves another important function in the present invention. The numerous organic compounds formed during pyrolysis are swept by gas from the second manifold 170 to the first manifold 160 and delivered to the furnace by the blower 220. At temperature above 750 to 800 oC, these compounds react with steam to form simple molecules CO and H2. A similar reaction with same products also takes place with carbon dioxide but at a much slower rate. If the temperature remains in the range 800- 850 oC in the presence of hydrogen, another small molecule CH4 is formed. The tubular heating coils (210 and 240) in the furnace - by providing heat at a high temperature - help to dismantle the complex organic chemicals formed during pyrolysis to small molecules of CO, H2 and if sufficient hydrogen is also present, then CH4. If the temperature is increased beyond 900 oC, then CH4 reacts with steam in the well-known Steam Methane reforming reaction producing CO and H2.

[0038] A low methane content syngas is required for applications involving synthesis reactions such as methanol, Di Methyl Ether, SAF or Sustainable Aviation Fuel etc. On the other hand, use of syngas for power generation will want a high methane syngas. The required peaktemperature of syngas product will change with a lowvs high methane syngas. The temperature to reach very low methane content in the syngas may be as high as 1050 oC; a practically acceptable low methane would be 950-1000 oC. High methane range will be compromised between low enough tar and high enough methane expected in the range of 800-900 oC. Thus, the target peak temperature reached in the furnace will range from 800- 950 oC for high methane case while it will require a temperature in the range of 950-1050 oC for low methane case.

[0039] The peak temperature reached in the furnace 200 could be the temperature of the net gas product of this gasification apparatus; however, that will waste energy. The heat content of the product gas is used to generate the steam needed by various reactions taking place in the gas generator as well as the furnace 200. The steam production possible from the net product gas is higherthan the expected steam need of the gas generator 100 and thefurnace 200 and can have other alternate uses. For example, if the feedstock has moisture content higher than 15-20%; it needs to be dried before use in the gas generator 100, the extra steam generated could be used in the dryer. Another example is for synthesis applications, purification steps of the raw product of synthesis can use steam. If such use option is available, then the steam generation will exceed just the steam need of the gas generator 100 and the furnace 200. The heat recovery boiler 300 generates steam in the third heat transfer coil 310 with boiling water on one side while the product gas will be on the other side of the tubular coil 310.

[0040] The present disclosure relates to a modified gasification apparatus for producing syngas from waste materials without using oxygen. The gas generator (100) has crossflow arrangement for circulation of gases across the solids present and has drying (120), pyrolysis (130) and carbon reaction (140) zones. A furnace (200) supplies the heat needed by the gas generator by sucking gas from gas generator, heating it and supplying the hot gas to the gas generator. The blower (220) sucks gas adds steam and heats it in a convective coil (210) to a temperature appropriate for high methane syngas; depending on feedstock the gas temperature ranges from 800-950o C. If low methane syngas is required, then even higher temperature (1000-1050oC) is required and gas from coil 210 may be sent to the radiant section coil (240) in the furnace (200) to produce a fully reformed product gas. Either way, from 210 only or 210+240 the product gas has sufficient heat to supply the entire heat need of gas generator (100). Major part of the hot product gas enters the gas generator through manifold (170) at multiple locations to supply its heating need. The balance of hot gas from coil (240) or coil 210 represents the net product gas and it enters the heat recovery boiler (300) to produce steam needed for reforming. The net product syngas contains mostly CO and H2 and small amounts of CH4, H2O and CO2. High concentration of most useful syngas components of CO and H2 is a major advantage of this invention. By changing whether gas passes only through coil 210 or coil 210 and 240 while maintaining appropriate peak gas temperature a syngas with high methane content or low methane content can be produced. The present disclosure overcomes limitation of the prior-arts and provides means of providing the heat need of drying, pyrolysis, and gasification zones without usingoxygen while eliminating tar and higher hydrocarbons from product gas. Heat Transfer area provided in coils 210 and 240 as well as heat release in the furnace can be matched to the heat demand of the gas generator. Hence, the gasification apparatus disclosed herein is a fully scalable equipment.

Claims

CLAIMSWe claim:1 . An apparatus for generation of syngas from solid fuel comprising a gas generator100, a furnace 200, and a heat recovery boiler 300, characterized in that: said furnace 200 has a first heat transfer tubular coil 210 and optionally a second heat transfer tubular coil 240, and said boiler300 has a third heat transfer coil 310, and wherein said gas generator 100 is capable of receiving first portion of solid feed, feed-1 , through a feed hopper 110 and converting said solid feed into hot gas through thermochemical process;- said gas generator 100 is provided with a first gas manifold 160 and a second gas manifold 170, said first gas manifold 160 being capable of receiving gas from said gas generator 100, and said second gas manifold 170 being capable of supplying gas to said gas generator 100; a blower 220 is provided to suck gas from said first gas manifold 160 and delivering it to said first heat transfer coil 210 and optionally to said second heat transfer coil 240; a conveyor 180 is provided to collect unreacted solid feed from the bottom of said gas generator 100 and delivering it to a grate 230 that is provided at the bottom of said furnace 200 for burning; heat radiated by burning flame being used to heat up said second heat transfer tubular coil 240; a steam generating tubular coil 310 is provided in said heat recovery boiler 300 contains steam generating coil 310, said boiler 300 having an outlet for discharging generated syngas; said steam being delivered to said furnace along with the gas supplied from first gas manifold 160; wherein gas generated in said gas generator 100 is taken to said furnace 200 using said blower 220 for heating, and the heated syngas in coils 210 and / or 240 is divided into two portions; the first portion of around 60-80% of gas is returned to the gas generator 100 at manifold 170 to provide the heat needed by gas generator 100, and the second portion remaining 20-40% of the gas is delivered to the heat recoveryboiler 300 for steam generation where it circulates around said steam generating coil 310, and from where syngas is discharged for collection.

2. The apparatus as claimed in claim 1 , wherein the maximum temperature achieved by burning solid feed on said grate 230 is 1200-1300 °C, and the temperature of gas coming out of said furnace 200 is as high as 1050 °C.

3. The apparatus as claimed in claim 1 , said solid feed comprises farm waste, animal manure, biomass in general, municipal solid waste, plastic waste, peat, lignite, and coal.

4. The apparatus as claimed in claim 1 , wherein said hopper 110 is situated near the top of said gas generator 100.

5. The apparatus as claimed in claim 1 , wherein said gas generator has the following virtual zones: a drying zone 120, where the temperature is around 150 °C; a pyrolysis zone 130 where the temperature is around 500 °C; a carbon reaction zone where the temperature is around 600 °C or more.

6. The apparatus as claimed in claim 1 , wherein said grate 230 is a travelling grate or vibrating grate or reciprocating grate; or a combination of any of these types of grates.

7. The apparatus as claimed in claim 1 wherein said furnace has a lower radiant zone in which said second heat transfer tubular coil 240 is situated and an upper convective zone in which said first heat transfer tubular coil 210 is situated.

8. A process of producing syngas from solid fuel comprisingthe steps of: a. providing solid feed to a gas generator 100 through a feed hopper 110 at ambient temperature and converting a large portion of said solid feed into gas through a thermochemical process; b. receiving a first portion of hot gas from a furnace 200 into a second gas manifold 170 from a furnace 200 from where it travels to a first gas manifold 160; c. the thermochemical process steps comprising drying of the solid feed in a drying zone 120, followed by the remaining solid feed undergoing pyrolytictransformation in a pyrolysis zone 130 converting solid to char, ultimately followed a char reaction zone 140 converting most of organic matter to gas; d. sucking gas from the first gas manifold 160 using a gas blower 220 and delivering the sucked gas to the furnace 200 for heating; e. heating the gas in the furnace 200 and delivering the first portion of the heated product gas to the second gas manifold 170 and the remaining second portion to the heat recovery boiler 300 for steam generation; f. delivering the unconverted solid feed that is the unreacted char from the char reaction zone 140 of step c through a hole 150 to a char removal screw 180, wherefrom delivering it to a grate 230 located in the furnace 200 for burning; g. feeding a second portion of solid fuel, feed-2, to said grate 230 for burning to supply the heat demand of the gas generator as well as the heat requirement of tar reforming reactions taking place in coils 210 and or 240 h. collecting cooled product gas from the boiler 300 and sending a first amount of steam generated from the boiler 300 to a first heat transfer coil 210 situated in the upper convective zone of the furnace 200, and sending the remaining steam as excess steam stream.

9. The process as claimed in claim 8, wherein the delivery of sucked gas of step d is made to either the first heat transfer coil 210 or a second heat transfer coil 240 situated in the lower radiant zone of the furnace 200.

10. The process as claimed in claim 8, wherein the proportion of the first portion to the total heated product in the furnace 200 is 65-80%.

11. The process as claimed in claim 8 wherein the temperature in the said drying zone 120, said pyrolysis zone 130, and said carbon reaction zone 140 is around 150 °C, 500-800 °C, and 600-850 °C, respectively.

12. The process as claimed in claim 8, wherein the temperature the gas from said furnace is in the range between 850-1050 °C.

13. The process as claimed in claim 8, wherein in step g, the steam sent to furnace 200 to supply the steam needed is 40 to 60% by weight of dry organic matter in the feed solid fuel.1 . The process as claimed in claim 6, wherein in the case where no fuel gas stream is available for the furnace, the quantity of feed-2 is up to 40% of feed-1 quantity.

15. The process as claimed in claim 8, wherein if a large quantity of fuel gas is available, step g is omitted.

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