AU2015101614A4 - Device for fixed-bed gasification of solid fuels - Google Patents

Abstract

A fixed-bed pressure gasifier for gasifying coarse-grained, solid fuels with oxygen- and steam-containing gasification media, comprising a gasifier vessel, a 5 feed for coarse-grained, solid fuels and a raw gas draw, both at a top of the gasifier vessel, a rotary grate and an ash discharge at a bottom of the gasifier vessel, an adjustable feed for first gasification media for non-slagging gasification by means of the rotary grate, means for adjusting critical minimum values for the steam/oxygen ratio in the gasification media, and a fixed bed heap above the 10 rotary grate, characterised by further comprising at the level of an upper region of the fixed-bed heap at least one gasification media injection nozzle protruding into the upper region for an additional and independent feed of second gasification media for a non-slagging gasification, the at least one gasification media nozzle arranged to enable injection of the second gasification media with steam/oxygen 15 ratios of 0.5 to 4 kg/m 3, preferably of 0.5 to 3 kg/m 3, and gas exit velocities of 20 to 120 m/s.

Description

1 DEVICE FOR FIXED-BED GASIFICATION OF SOLID FUELS FIELD OF THE INVENTION 5 This invention relates to an apparatus for the fixed-bed pressure gasification of solid fuels with increased performance and a widened usage spectrum of solid fuels. Such apparatus, also called gasifiers, allow the gasification of coals with a higher fine grain content and/or in addition the gasification of fine-grained and pulverized fuels. 10 BACKGROUND TO THE INVENTION The gasification of coarse-grained solid fuels, i.e. of coarse-grained coals and/or carbonaceous solids with grain sizes greater than about 5 mm and smaller than 15 about 10 mm, preferably is effected in the fixed bed by the process of fixed-bed pressure gasification FPG, also known under the term Fixed Bed Dry Bottom Gasification. The fuels are introduced into the fixed-bed pressure gasifier over head by means of pressure locks. In the fixed bed (actually moving bed), which extends over the height of the fixed-bed pressure gasifier, the following zones are 20 formed in an ideal-typical way from top to bottom: Drying zone, pyrolysis zone, gasification zone, oxidation zone and ash zone. At the bottom of the gasifier the ashes are discharged through a rotary grate which at the same time serves for supplying the gasification media. The raw gas draw is located at the top of the fixed-bed pressure gasifier. 25 The gasification media substantially consist of technical oxygen and steam. The latter is added in excess, in order to limit the maximum temperatures in the oxidation zone to values below or in the vicinity of the ash melting temperatures relevant for the fixed-bed pressure gasification and thus avoid the formation of 30 massive, interfering ash agglomerates or slaggings (non-slagging gasification). The quantity ratio of steam and oxygen in the gasification medium represents one of the most important quantities for the control of the process. It frequently is indicated as steam/oxygen ratio, preferably in the units kg steam/mstd 3 oxygen 2 (100 vol-%). Depending on the height of the ash melting temperatures, minimum values between about 4 kg/m 3 (high-melting ashes) and about 9 kg/m 3 (low melting ashes) are required. The steam excesses increase the gas flow velocities and the amount of fine grain which is discharged with the raw gases via the raw 5 gas outlet, but do not contribute to an increase of the reaction turnover. Although the values for the steam/oxygen ratio are adapted to the ash melting temperatures and are kept as low as possible (critical minimum values of the steam/oxygen ratio for a so-called "hot" operation at the "slag limit"), this results in considerable limitations above all with respect to the maximum performance, the 10 permeability of the bed and the discharge of dust, see also /J. Schmalfeld: Die Veredlung und Umwandlung von Kohle, DGMK (2008), p. 311/. A general disadvantage of the fixed-bed pressure gasification, which is caused thereby, consists in that the solid fuels to be gasified should contain only small 15 amounts of fine-grained fuels with grain sizes smaller than about 5 mm and in particular pulverized fuels with grain sizes smaller than about 1 mm. Otherwise, this results in local accumulations of fine-grained material in the fixed bed with the consequence of a non-regular, channel-like flow through the fixed bed as well as a high discharge of dust, incomplete carbon conversions in the ashes or 20 slaggings. These negative effects are reinforced in different ways, when caking hard coals or briquetted lignites are used. The general disadvantage of the counterflow principle furthermore applies for the low raw gas outlet temperatures of the fixed-bed pressure gasification. Ammonia, 25 non-condensable higher hydrocarbons, phenols and tar oils, which together with the discharged dusts are separated in the water (tar/gas water/dust mixtures), generally are undesired by-products. The raw gas outlet temperatures are obtained in dependence on the feed fuels corresponding to the total heat balance of the process. Except for the selectively arranged, incomplete heat exchange 30 between gas and solids (e.g. lowered bed) they cannot be increased actively. To maintain the required grain size spectrum of the coarse-grained fuels to be gasified, the raw coals mined must be processed. In particular, hard coals are 3 screened and/or washed before the gasification, in order to separate the fine grain (coal fines), lower the ash content, and increase the quality of the solid fuels to be gasified. The fines smaller than 5 mm frequently amount to up to 50 % of the unscreened, mined coal. Since the separated coal fines cannot easily be 5 utilized for the production of synthesis gases during the fixed-bed pressure gasification, corresponding solutions were sought. According to patent document EP1 0792A1 pellets were formed from the fine grained fuels, which are surrounded by a non-caking enveloping layer. Patent 10 document GB1 435089A describes the production of a fine coal/ash/pitch mixture which is processed in an extruder to obtain extrudates which are pressed directly from the extruder into the free gas space of the atmospherically operated fixed bed pressure gasifier. As pelletizing aids for coal fines bentonites also are proposed (US Patent 4,773,919 B1). Alternatively, US Patent 4,146,369 B1 15 provides to expand the fixed-bed pressure gasifier towards the top by a fluidized bed gasifier and above the same by an entrained-flow gasifier, in which fine grained and pulverized fuels should be usable. There is also proposed a separate arrangement of fluidized-bed or entrained-flow gasifiers for processing the fine grained or pulverized fuels, e.g. in patent document WO 1980/00974 Al, where 20 gasification of a previously produced fuel/hydrocarbon/water slurry takes place in the entrained-flow gasifier. Patent document DD 219 597 Al discloses a process for the non-slagging gasification of coals, in which the feed of gasification medium is split up into a 25 primary and a secondary feed. At a freely selectable bed height adjusted to the material to be gasified, the main part of the gasification medium is supplied to the primary gasification separate from the grate and the part to be gasified provided for the secondary gasification is supplied via the grate in a known way, wherein the steam/oxygen ratio should be reducible down the to exclusive injection of 30 steam. In general, this is a non-slagging operation of the gasification with the formation of fine-grained ash. According to the proposal, the gasifier must be operated with high steam/oxygen ratios, so as not to exceed the ash melting point. The reason is to avoid slaggings of the gasifier. In general, the fine ash 4 constituents should quickly be transported into the region below the gasification medium exit, in order to avoid an ash transport into the upper reactor sections and the discharge of ash with the production gas. It should be noted that the proposal disregards the elementary requirements of environmental protection, of 5 the efficiency and the operational safety. The major to complete feed of the gasification medium into the higher regions of the bed at a non-slagging operation of the gasifier necessarily leads to burning through of the bed (channel breakthrough) and the mixture of not completely reacted oxygen with the raw gas, so that deflagrations or explosions can occur with catastrophic consequences. 10 Further reasons for the unfeasibility of the proposal are the incompleteness of the carbon conversion, i.e. the high carbon content of the ash withdrawn via the rotary grate, and the prevention of the suitability of the ash for landfill disposal. A further procedural limitation of non-slagging fixed-bed gasification according to 15 the prior art relates to the fuel spectrum with respect to the caking capacity of the coals. Hard coals with stronger caking properties can be gasified, but require a mechanical stirrer in the upper part of the fixed-bed pressure gasifier, whereby the process as a whole becomes more complicated, more susceptible to failure and more expensive. 20 It has not been possible so far to find procedurally more favourable solutions for the omission of the stirrer. The other proposed solutions for the utilization of fine fuels are technically expensive and economically not viable. They could not gain acceptance in practice. The fine coal must be supplied to another use (in general 25 the combustion) instead of the gasification. Nevertheless, a large part of the fine coal frequently is not economically usable and must be deposited in the form of heaps. In light of the above, it would be beneficial to develop a fixed-bed pressure 30 gasifier of solid fuels, which, by means of small procedural and technical changes to previously known fixed-bed pressure gasifiers, allows one or more of the following improvements: increase the performance of fixed-bed pressure gasifiers; lower the use of steam; widen the spectrum of use of fuels with respect 5 to caking coals and coals with a higher fine grain content and/or in addition allows gasifying fine-grained and pulverized fuels. SUMMARY OF THE INVENTION 5 According to the present invention, there is provided a fixed-bed pressure gasifier for gasifying coarse-grained, solid fuels with oxygen- and steam-containing gasification media, comprising a gasifier vessel with a feed for coarse-grained, solid fuels and a raw gas draw, both at a top of the gasifier vessel, a rotary grate 10 and an ash discharge at the bottom of the gasifier vessel, an adjustable feed for first gasification media for a non-slagging gasification by means of the rotary grate, means for adjusting critical minimum values for the steam/oxygen ratio, and a fixed bed heap above the rotary grate, characterised by further comprising at the level of an upper region of the fixed-bed heap at least one gasification 15 media nozzle protruding into the upper region for supplying an additional feed of second gasification media for a slagging gasification, independent from the first gasification media supplied through the rotary grate, and wherein the at least one gasification media nozzle is arranged to enable injection of the second gasification media with steam/oxygen ratios of 0.5 to 4 kg/m 3 , preferably of 0.5 to 20 3 kg/m 3 , and gas exit velocities of 20 to 120 m/s. According to an advantageous aspect of the fixed-bed pressure gasifier of the invention, the at least one gasification media nozzle is designed such that the quantity of the injected oxygen of the second gasification media corresponds to 0 25 to 50 % of the total oxygen quantity supplied by both gasification media. Advantageously, the fixed-bed pressure gasifier can include several gasification media nozzles for the second gasification media, which are arranged in one or two planes. 30 According to an advantageous aspect of the invention, the nozzle orifices of the gasification media nozzles in one height zone are located either in a planar, horizontal plane, in a vertically stepped arrangement in the height zone, or in a 6 cone-shaped height zone which approximately reproduces the mushroom-shaped contour of the rotary grate or the contour of the bed surface. With a preferred free length of at least 10 cm (free nozzle lengths), the 5 gasification media nozzles protrude into the gasification space of the fixed-bed pressure gasifier. Preferably, the gasification media nozzles located close to the wall protrude about 20 cm to 1 m into the gasification space of the fixed-bed pressure gasifier. With 10 larger, free nozzle lengths up to about 3 m, the gasification media nozzles are held from above by means of tie rods. To form turbulent zones locally separated from each other, the lateral, horizontal distance between the outlet openings of the gasification media nozzles should not 15 fall below 50 cm. Preferably, the lateral, horizontal distance of the outlet openings is 1 to 2 m. The vertical distance of outlet openings located one above the other should be at least 1 m, preferably however greater than 2 m. According to an advantageous aspect, the fixed-bed pressure gasifier includes at 20 least one inlet for fine-grained and/or pulverized fuels (fine fuel inlet). The fine fuel inlet is designed as gravity inlet or as stuffing inlet for fine fuels compacted by briquetting. According to an advantageous aspect of the fixed-bed pressure gasifier, the 25 gasification media nozzles are designed as water-cooled gasification media mixture nozzles (in the case of oxygen and steam as second gasification media) or as water-cooled multicomponent nozzles (in the case of the combined fine fuel supply). 30 The technical design of the second slagging gasification is simple, robust and requires technical adaptations of the known and well-tried fixed-bed pressure gasifier. This also applies to the lead-through stubs for the gasification media nozzles and, if necessary, the supply stubs for the fine fuels.

7 It has been found to be particularly advantageous that the second slagging gasification can be set up, retrofitted and operated incrementally (starting with one gasification media nozzle) in existing fixed-bed pressure gasification plants. 5 The second slagging gasification can be operated partly or be put out of operation or be retro-fitted, according to requirements. With the above described inventive gasifier, it is possible to conduct a process for the fixed-bed pressure gasification of coarse-grained, solid fuels with oxygen- and 10 steam-containing first gasification media, in which critical minimum values for the steam/oxygen ratio can be adjusted, wherein in addition to and independent of the first gasification media supplied by means of the rotary grate second gasification media for a slagging gasification are injected via at least one gasification media nozzle reaching into the upper region of the fixed-bed heap, 15 and in which the second gasification media are injected with steam/oxygen ratios of 0.5 to 4 kg/m 3 and gas exit velocities of 20 to 120 m/s. As noted, the second gasification media for the slagging gasification are supplied to the fixed-bed pressure gasifier in addition to and independent of the the first 20 gasification media supplied via the rotary grate for the non-slagging gasification, wherein the second gasification media are advantageously injected into the upper region of the heap of the fixed bed by means of the gasification media nozzles reaching into the upper region of the fixed-bed heap. With the first gasification media, the first non-slagging gasification is carried out with the ideal-typical 25 formation of zones over the entire heap of the fixed bed (first drying zone, first pyrolysis zone, first gasification zone, first oxidation zone, first ash zone), and with the second gasification media, the second slagging gasification is carried out with local formation of turbulent zones (raceway formation). 30 The critical minimum values for the steam/oxygen ratios (indicated in the units kg steam / mstd 3 oxygen (100 vol-%) ) of the first gasification media for the "hot" operation at the "slag limit" are adapted to the ash melting behaviour of the solid fuels used. In simple terms, the adaptation is effected such that a rather defined 8 ash granulation is effected (softening and sintering of the ash), without the occurrence of slaggings and the formation of large slag lumps which block the discharge, cf. /J. Schmalfeld: Die Veredlung und Umwandlung von Kohle, DGMK (2008), p. 311/. 5 Advantageously, the second gasification media are injected into the upper half of the first gasification zone formed during the gasification, i.e. below the first pyrolysis zone formed during the gasification. What is particularly advantageous is the injection of the second gasification media in a height zone which comprises 10 a vertical extension of < 1 m in the upper half of the first gasification zone below the pyrolysis zone. Particularly advantageously, the second gasification media are injected in a height zone of the fixed-bed pressure gasifier which maximally extends from 1 m above the tip of the rotary grate to 0.5 m below the surface of the heap of the fixed bed, preferably from 2 m above the tip of the rotary grate to 15 1 m below the surface of the heap of the fixed bed. According to an advantageous aspect of the process of the invention, the quantity of the injected oxygen of the second gasification media corresponds to 0 to 50 % of the total oxygen quantity supplied. 20 The injection of the second gasification media with gas exit velocities of 20 to 120 m/s causes the formation of turbulent raceways in the form of cavities in the fixed bed heap before the outlet openings of the gasification media nozzles in which carbon is burnt with oxygen (second combustion zones). The turbulent zones 25 before the nozzles are enveloped by a heap of coke with which the excess steam of the first non-slagging gasification and possibly the steam of the second slagging gasification react with a decrease in temperature (second gasification zones). 30 Due to the fact that the second gasification media are injected with steam/oxygen ratios with values of 0.5 kg/mstd 3 to 4 kg/mstd 3 , preferably of 0.5 to 3 kg/mstd 3 , it is achieved that the ashes released before the at least one gasification media nozzle reaching into the upper region of the fixed-bed heap melt or sinter 9 immediately and are deposited in the coke heap at the edge of the turbulent zones (second slag zones). The molten or sintered ashes quickly cool down and solidify in the surrounding colder coke heap and release their heat to the surroundings for reinforcing the endothermal second gasification processes. The 5 formation of classical, layer-shaped zones does not occur during the gasification with the second gasification media. For example, with the second gasification media with steam/oxygen ratios of 0.5 mean maximum temperatures of about 2000 0C are achieved before the 10 gasification media nozzles reaching into the fixed-bed heap, which is advantageous for the gasification of coals with ash melting points of 1500 - 1700 C. When the steam/oxygen ratio of the second gasification media is 3.0, mean maximum temperatures of about 1800 0C are achieved before the gasification media nozzles reaching into the fixed-bed heap. This is advantageous for the 15 gasification of coals with ash melting points of 1300 - 1500 C. It is advantageous when the gasification with the second gasification media is carried out below the first pyrolysis zone. It is ensured here that degassed coke is available (higher cold gas efficiency as compared to coal) and the slags or sinter 20 formed solidify quickly in the surrounding colder coke heap. On the other hand, as will be explained below, the ambient temperatures of about 800 to 1100 0C in the surroundings of the gasification media nozzles reaching into the fixed-bed heap are so high that the solidified slags do not yet obtain a high strength. Slags adhering to the gasification media nozzles are detached from the heap moving 25 downwards and are transported further on. With respect to the temperatures of the coke heap in the first gasification zone the following should be noted: Due to the endothermal gasification reactions (initially without taking account of the second gasification processes), the temperatures of 30 the coke heap settle at approximately constant values of the so-called kinetic reaction end temperatures. These values are obtained automatically, chiefly in dependence on the reactivity of the cokes with respect to steam. The range of the reaction end temperatures extends from about 800 0C with high-reactivity fuels 10 (e.g. ortho-lignites) to 1100 0C with low-reactivity fuels (e.g. low-volatility bituminous hard coals). Thus, it lies below the temperature range for the ash melting points of most fuels (about 1200 - 1500 0C). 5 It is particularly advantageous that the ashes released during the second slagging gasification melt immediately and suppress each channelling, since a channel-like "burn-through" of oxygen through the heap is inhibited due to the immediate formation of slag. Initially formed channels or channels which originate from the first gasification likewise are quickly "closed" by forming slag. For this reason, the 10 turbulent zones cannot be removed from the gasification media nozzles towards the top or only to a small extent, but meander at approximately the same height before and above the gasification media nozzles. The second gasification hence is locally limited and defined in height corresponding to the arrangement of the outlet openings of the gasification media nozzles. The meandering gas flow and 15 the slag formed stabilize the fixed bed in the surroundings of and above the gasification media nozzles, so that despite higher flow velocities the regular flow through the fixed bed is maintained. The second slagging gasification leads to uniforming of the flow through the entire 20 fixed bed. The fine grain content of the used coarse-grained fuels can be increased without the discharge of dust with the raw gases rising. The lower grain sizes of the coarse-grained solid fuels supplied to the fixed-bed pressure gasifier at the top can be lowered from about 5 mm to about 2 mm. 25 Due to the gasification with the second gasification media for the slagging gasification, fine-grained and/or pulverized fuels (fine fuels) can be utilized in larger amounts in addition to the coarse-grained fuels, which otherwise would have to be supplied to another use or dumping. For this purpose, the fine fuels are introduced into the turbulent zones in concentrated form, wherein the 30 quantities of the added fine fuels at most are so large that in stoichiometric terms a substantial gasification in the turbulent zones is ensured.

11 Another important advantage of the second slagging gasification consists in that in particular the fine-grained and pulverized parts of the fuels are gasified in the turbulent zones by producing coarser ash/slag particles. The cooled, solidified slags contribute to increasing the grain size in the entire fixed bed, in particular in 5 the first ash zone, and furthermore to the "interlocking" stabilization of the fixed bed over the entire height. Local accumulations of fine grain and dust, which cause an eruption-like flow through the bed and are one of the main causes for high discharges of dust, are inhibited or pushed back. The second gasification thus leads to uniforming of the flow through the entire fixed bed. The fine grain 10 content of the fuels used can be increased without the discharge of dust with the raw gases rising. Dry to moist, flowable fine fuels advantageously are charged into the heap of the fixed bed from above by means of gravity, approximately vertically above the 15 turbulent zones formed before the gasification media nozzles. On gravity input, the fuels slip into the gasifier due to their own weight via a dosing device, from a pressure lock arranged above the fixed-bed pressure gasifier. What is also possible, however, is a gravity input or a pressure input from the side directly into the fixed bed above the turbulent zones. Dry, pneumatically conveyable fine fuels 20 also are blown directly into the turbulent zones by means of pneumatic conveyance via the gasification media nozzles or from the side. Finally, fine fuels in the form of slurries are pumped in, namely either via the gasification media nozzles or approximately vertically above the turbulent zones from above onto or into the heap of the fixed bed. 25 Alternatively, the use of a stuffing input also is possible, which is effected at the upper edge of the fixed bed, preferably within the first drying zone. By means of a briquetting press, preferably a stamp press, fine-grained and/or pulverized fuels (fine fuels) are compressed, partly agglomerated or compacted in a mold channel 30 and pressed directly into the bed. In contrast to the teaching of patent document GB1 435089A, the compacted fine fuels do not fall onto the fixed bed from above, whereby a crumbling of the compacted fine fuels followed by an increased discharge of dust in the raw gas is avoided. At the same time, the entering strand 12 of compacted fine fuels is covered towards the top by coarse-grained fuels, so that a direct blow-out of the abrasion is prevented. Another essential advantage of this input system is the possible admixture of the tar-oil solids mixture obtained as agglomeration aid during the fixed-bed pressure gasification and the possible 5 omission of a lock system for the input of the fine fuels. Due to the very high compacting pressures up to 150 MPa, which occur in the moulding channel, an almost gas-tight closure between the pressurized gasification space and the surroundings is possible under atmospheric pressure, so that a separate pressurizing system of the fine fuels can be omitted. This form of the input of fine 10 fuels is independent of the operation of the second gasification and can also be employed with non-operated or disused second gasification media nozzles. The second slagging gasification not only improves the fuel tolerance with respect to increased fine-grain and dust contents of the fuels or provides for the additional input of fine fuels, but it also increases the fuel tolerance with respect to caking 15 coals, which would not be gasifiable without the use of a stirrer. The second combustion zones with their fast rises in temperature and their high temperatures reduce the caking tendency of the coals and break up coke bonds formed already. Due to the second slagging gasification, the use of the stirrer can be omitted in many cases. 20 It is also possible to carry out the second slagging gasification in the first pyrolysis zone or in the region of the transition from the first pyrolysis zone to the first non slagging gasification zone. In this case, the ratio of the combustion and gasification reactions is shifted more in direction of combustion reactions in the 25 second slagging combustion zones. The raw gas outlet temperatures rise and the higher hydrocarbons, phenols as well as tar oils, which leave the fixed bed towards the top, are thermally broken down more strongly. The zone-related adjustment of the second slagging gasification is achieved by setting defined bed heights of the fixed bed. In this way, the raw gas outlet temperatures and the 30 quality of the raw gas (methane content, undesired secondary components, etc.) can be adapted.

13 The gasification media nozzles are designed as water-cooled gasification media mixture nozzles (in the case of oxygen and steam as second gasification media) or as water-cooled multicomponent nozzles (in the case of the combined feed of fine fuels). They can be both non-cranked (tubular nozzles) and cranked (crank 5 nozzles), wherein in the case of the crank nozzles the cranked nozzle head is seated on the tubular nozzle shank. The gasification media nozzles are guided through the cylindrical outer jacket or double jacket of the fixed-bed pressure gasifier. The non-cranked gasification 10 media nozzles are aligned radially and horizontally or different from the radial and horizontal alignment attachable in all directions with angles of attack of < 450. Preferably, the nozzles are aligned radially and inclined downwards by 10 to 200 against the horizontal. This is found to be advantageous with respect to the avoidance of the entry of solids into the interior of the nozzles and with respect to 15 the formation of the turbulent zones. In the case of the use of cranked gasification media nozzles, the nozzle shanks are aligned approximately horizontally and the nozzle heads analogous to the above-mentioned angles of attack of the tubular nozzles. 20 The second slagging gasification is carried out in a limited height zone in the upper region of the bed of the fixed-bed pressure gasifier. The lower limitation is given by the fact that a sufficient large, vertical minimum distance to the underlying oxidation zone is ensured. This distance is > 0.5 m, preferably > 1 m. The vertical minimum distance to the tip of the rotary grate hence is > 1 m, 25 preferably > 2 m. It is required to allow the slag or sinter formed in the turbulent zone to solidify, before it gets into the oxidation zone or onto the surface of the rotary grate. On the other hand, the gasification media nozzles are not exposed to too high temperatures (< 1100 0C) in the gasification zone. The upper limitation of the height zone results from the fact that a sufficiently high overlap of the 30 gasification media nozzles by the fuel layer of the fixed bed of > 0.5 m, preferably > 1 m, is ensured. With a bed height of the fixed bed of 5 m, calculated from the tip of the rotary grate, the vertical extension of the height zone for the second gasification can amount to a maximum of 3.5 m, preferably a maximum of 2 m.

14 The gasification media nozzles can be distributed over this height and over the cross-section of the fixed-bed pressure gasifier. Another advantageous aspect consists in that for the second slagging gasification 5 zone a rather short height zone with a vertical extension of < 1 m in the upper half of the first gasification zone, below the pyrolysis zone, is chosen, so that the first non-slagging gasification zone is extended towards the top uniformly over the cross-section. 10 In case the height of the heap of the fixed bed is changed during the operation of the fixed-bed pressure gasifier between a maximum and a minimum level and the difference is more than 1 m, it is advantageous when alternatively two height zones of the fixed-bed pressure gasifier are equipped with gasification media nozzles, the lower height zone for the minimum level and the upper height zone 15 for the maximum level of the fixed bed. The vertical minimum distance of the two height zones is more than 1 m. In procedural terms, the two height zones then are selectively charged with the second gasification media. Advantageously, the second gasification media are injected in a height zone 20 either in a planar, horizontal plane, in a vertically stepped arrangement in the height zone, or in a cone-shaped height zone which approximately reproduces the mushroom-shaped contour of the rotary grate or the contour of the bed surface. 25 Preferably, the nozzle orifices of the gasification media nozzles are located in a height zone either in a planar, horizontal plane, in a vertically stepped arrangement in the height zone, or in a cone-shaped height zone which approximately reproduces the mushroom-shaped contour of the rotary grate or the contour of the bed surface. 30 With a free length of at least 10 cm (free nozzle lengths), the gasification media nozzles protrude into the gasification space of the fixed-bed pressure gasifier. Preferably, the gasification media nozzles located close to the wall protrude about 15 20 cm to 1 m into the gasification space of the fixed-bed pressure gasifier. With larger, free nozzle lengths up to about 3 m, the gasification media nozzles are held from above by means of tie rods. 5 To form turbulent zones locally separated from each other, the lateral, horizontal distance between the outlet openings of the gasification media nozzles should not fall below 50 cm. Preferably, the lateral, horizontal distance of the outlet openings is 1 to 2 m. The vertical distance of outlet openings located one above the other should be at least 1 m, preferably however greater than 2 m. 10 The second gasification media are injected with steam/oxygen ratios between 0.5 and 4 kg/m 3 , preferably between 0.5 and 3 kg/m 3 . Although no steam is required from a procedural point of view, a small admixture of steam is advantageous, so that when the oxygen is shut off fast, steam is available as purge gas for the 15 gasification media nozzles without interruption. Instead of steam, carbon dioxide or other inert gases also can be used as purge gases. The quantity ratios of second to first oxygen can be varied within wide limits. In the case of an individual gasification media nozzle, 5 to 20 wt.-% of the entire 20 oxygen supplied are injected as second oxygen. The upper value also can be exceeded when larger amounts of fine fuels should be utilized with a gasification media nozzle. In the case of the formation of a second gasification zone over the entire cross-section of the fixed-bed pressure gasifier and the additional gasification of fine fuels, up to 50 wt.-% of the entire oxygen supplied can be 25 injected as second oxygen. The lower the ash contents of the feed fuels, the higher amounts of second oxygen are achievable. The size of the slag or sinter pieces formed in the turbulent zones before the individual gasification media nozzles is limited by the fact that the oxygen loads of 30 the individual gasification media nozzles are varied between minimum and maximum load. The total oxygen quantity of the second gasification media can be kept constant by varying the load distribution between the individual nozzles, or the total oxygen quantity also can be varied over time.

16 Corresponding to the quantity ratios of second oxygen (for the slagging gasification) injected in addition to the first oxygen (for the non-slagging gasification), the thermal capacities of the fixed-bed pressure gasifier are 5 increased approximately proportionally. It is of minor importance whether the fuel throughput is increased or whether additional fine fuels are introduced. Together with the coarse-grained fuels or in addition to the coarse-grained fuels, larger amounts of fine-grained and fine fuels can be gasified. The fuel spectrum also can be expanded in direction of hard coals caking more strongly, without the use 10 of a stirrer being required. At the same time, the specific use of steam is lowered, and the performance limit of the thermal gasifier capacity is increased due to the improved flow conditions of the heap of the fixed bed. An exemplary embodiment of the invention will be explained in detail with 15 reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 shows a schematic / diagrammatic longitudinal section of a fixed-bed 20 pressure gasifier in accordance with the invention; and Fig. 2 shows a cross-section of the gasifier of figure 1 taken at section A-A. DESCRIPTION OF PREFERRED EMBODIMENT 25 Referring first to fig. 1, there is shown in schematic section a fixed-bed pressure gasifier 1 according to a preferred embodiment of the invention. The fixed-bed pressure gasifier 1 comprises pressure vessel 9 which has at its top an inlet 2 for coarse-grained, solid fuels and a raw gas outlet 30. At the 30 bottom of vessel 9, fixed-bed pressure gasifier 1 has a rotary grate 5 for supplying first gasification media 6 for the non-slagging gasification and an ash discharge 31.

17 In the upper part of the fixed-bed pressure gasifier, the fuel inlet 2 opens into a hanging shaft 28 within vessel 9. Beside the fuel inlet 2 for coarse-grained fuels, an inlet 21 for fine fuels is arranged at the top of the fixed-bed pressure gasifier 1. The fine fuel inlet 21 opens into a downpipe 22 held within the hanging shaft 28, 5 wherein the downpipe 22 is longer than the hanging shaft 28 and ends in the reaction space of the fixed-bed pressure gasifier vessel 9 with a baffle plate 24. The fine fuel inlet can be made inert with nitrogen 27. The clear inside diameter of the vessel 9 of fixed-bed pressure gasifier 1 is 4m 10 and the height of the heap of the fixed bed 3, calculated from the tip 4 of the rotary grate 5, is 6m on average. It is defined by the hanging shaft 28 for fuel distribution. The heap of the fixed bed 3 ideal-typically is divided into the five layers, from bottom to top: first ash zone 14, first oxidation zone 15, first gasification zone 16, first pyrolysis zone 17 and first drying zone 18. 15 At a height of 3m above the tip 4 of the rotary grate 5, a total of ten stubs 7 extend through the wall of vessel 9. The stubs 7 are uniformly distributed over the outer periphery of vessel 9 and serve to supply the second gasification media 8 to the fixed-bed pressure gasifier 1 for the slagging gasification of the solid fuel. 20 Above the tip 4 of the rotary grate 5, in the upper plane of the first gasification zone 16 and above the first pyrolysis zone 17, (additional) supply stub 7 extends through the wall of the gasifier vessel 9. 25 The supply stubs 7 in the upper plane of the first non-slagging gasification zone 16 are equipped with gasification media nozzles 12 reaching into the gasification zone for the supply of second gasification media 8 for the slagging gasification. In the sectional view of figure 2, the stubs 7 are numbered with /1 / to /10/ in 30 clockwise direction. They are guided through the outer, pressure-bearing vessel wall 10 and through the inner steel jacket 11 of vessel 9. A total of six of the ten stubs 7 are equipped with gasification media nozzles 12. The gasification media nozzles 12 are designed as tubular nozzles, aligned radially and inclined 18 downwards with an angle of 150 against the horizontal. They extend 50 cm into the heap of the fixed bed 3. The orifices 13 of the gasification media nozzles 12 end in the upper region of the first non-slagging gasification zone 16. 5 The (additional) stub 7 directed into the first drying zone 18 cooperates with a briquetting press 32 for supplying compacted or briquetted fine fuels 21 into the gasifier 1. The fixed-bed pressure gasifier 1 thus constructed is operated as follows: 10 A charge of 58 t/h of non-caking, coarse-grained hard coals with an ash content of about 35 wt.-% (dry), a water content of about 5 wt.-% (dry), an ash melting point of about 1400 0C and a grain size of about 5 - 100 mm are introduced into the fixed-bed pressure gasifier vessel 9 from above through fuel inlet 2 and 15 gasified in the fixed-bed pressure gasifier's vessel 9 at a total pressure of about 30 bar. The raw gas 29 leaves the fixed-bed pressure gasifier 1 through the raw gas outlet 30 of vessel 9, while the ash 31 can be withdrawn at the bottom of vessel 9 through rotary grate 5. The first gasification media 6 are supplied through the rotary grate 5 into vessel 9. The quantity of oxygen in the first 20 gasification media 6 is 12,000 Nm 3 /h (based on pure oxygen), the steam/oxygen ratio is about 4.5 kg/Nm 3 on average. The quantity of oxygen of the second gasification media 8 in total is 3200 Nm 3 /h (based on pure oxygen), the steam/oxygen ratio is 0.8 kg/Nm 3 . 25 The gasification media nozzles 12 with the numbers /3/, /4/, /8/ and /9/ are each charged with 600 mstd 3 /h of oxygen. The gasification media nozzles 12 with the numbers /1/ and /6/ are each charged with 400 mstd 3 /h of oxygen. The second gasification media 8 flow with flow velocities of 70 m/s (gasification media nozzles 12, numbers /3/, /4/, /8/ and /9/) and 50 m/s (gasification media nozzles 12, 30 numbers /1/ and /6/). Turbulent zones 19 are formed downstream the orifices 13. Downstream the adjacent gasification media nozzles 12, numbers /3/ and /4/ as well as numbers /8/ and /9/, two larger, coherent regions 20 are formed by the respective turbulent zones 19.

19 Fine fuels 21 are introduced about centrally above the coherent regions 20 of the turbulent zones 19 of the adjacent gasification media nozzles 12, numbers /3/ and /4/ as well as numbers /8/ and /9/, using gravity feed via a downpipe 22 or forced fed via the stuffing inlet by means of the briquetting press 32. 5 Baffle plates 24 are located at the lower outlet opening 23 of the downpipe 22, below which are formed cavities 25 in the heap of the fixed bed 3, into which the fine fuels 21 can flow off freely. The downpipe 22 is supported at the hanging shaft 28 with holders 26. The vertical distance between the outlet openings 23 10 and the gasification media nozzles 12 is 2m. The downpipe 22 can be made inert with a small amount of nitrogen 27. The fine fuels 21 are obtained from the same hard coal stock used to charge the vessel through top inlet 2. The grain size of the fine fuels 21 is 0 - 2 mm, the ash 15 content is 40 wt.-% (dry), the water content 5 wt.-% (dry). 5.5 t/h of fine fuels 21 is supplied through each of both downpipes 22 into vessel 9. In the present example, the thermal capacity of the fixed-bed pressure gasifier 1 is increased by about 25% by incorporating the process-related and/or 20 constructional features of the invention. With the present invention it has for the first time become possible to co-gasify fine fuel to a considerable extent.

20 Reference Numerals 1 fixed-bed pressure gasifier 2 inlet for coarse-grained solid fuel 5 3 fixed bed 4 tip 5 rotary grate 6 first gasification media 7 supply stub 10 8 second gasification media 9 vessel 10 outer, pressure-bearing vessel wall 11 inner, steel vessel jacket 12 gasification media nozzles 15 13 orifices of the gasification media nozzles 14 first ash zone 15 first oxidation zone 16 first gasification zone 17 first pyrolysis zone 20 18 first drying zone 19 turbulent zone 20 coherent region 21 fine fuels 22 downpipe 25 23 outlet opening 24 baffle plate 25 cavities 26 holder 27 nitrogen 30 28 hanging shaft 29 raw gas 30 raw gas outlet 31 ash 32 briquetting press 35 33 agglomeration aid

Claims (5)

1. A fixed-bed pressure gasifier for gasifying coarse-grained, solid fuels with oxygen- and steam-containing gasification media, comprising a gasifier vessel, a feed for coarse-grained, solid fuels and a raw gas draw, both at a top of the 5 gasifier vessel, a rotary grate and an ash discharge at a bottom of the gasifier vessel, an adjustable feed for first gasification media for non-slagging gasification by means of the rotary grate, means for adjusting critical minimum values for the steam/oxygen ratio in the gasification media, and a fixed bed heap above the rotary grate, characterised by further comprising at the level of an upper region of 10 the fixed-bed heap at least one gasification media injection nozzle protruding into the upper region for an additional and independent feed of second gasification media for a non-slagging gasification, the at least one gasification media nozzle arranged to enable injection of the second gasification media with steam/oxygen ratios of 0.5 to 4 kg/m 3 , preferably of 0.5 to 3 kg/m 3 , and gas exit velocities of 20 15 to 120 m/s.

2. The fixed-bed pressure gasifier according to claim 1, comprising a plurality of said gasification media injection nozzles, said injection nozzles arranged in one or two planes along the height of the fixed-bed heap, the gasification media injection nozzles preferably protruding into a gasification space of the fixed-bed 20 pressure gasifier with a free length of at least 10 cm.

3. The fixed-bed pressure gasifier according to claim 1 or 2, further comprising at least one additional feed into the vessel for fine-grained and/or pulverized solid fuels separate from the feed for coarse-grained, solid fuels.

4. The fixed-bed pressure gasifier according to claim 3, wherein the 25 additional feed comprises either a gravity-fed inlet for flowable, fine-grained or pulverized fuels, or a stuffing inlet for fine fuels compacted by briquetting.

5. The fixed-bed pressure gasifier according to anyone of claims 1 to 4, wherein the gasification media injection nozzles are either water-cooled nozzles for co-injection of oxygen and steam as the second gasification media, or water- 22 cooled injection nozzles for co-injection of oxygen, steam and pulverized solid fuels into the vessel. L'AIR LIQUIDE, SOCIETE ANONYME POUR L'ETUDE ET L'EPLOTATION 5 DES PROCEDES GEORGES CLAUDE WATERMARK PATENT AND TRADE MARKS ATTORNEYS 10 UIP1512AUOO