DE3112602A1 - "GASIFICATION SYSTEM" - Google Patents

Description

Gasification plant

The present Krt jndumj concerns a "wall construction for at least one <m part of the walls of a gasification area a gasification plant, in which carbonaceous matter too Synthesis or heating gas is converted.

Bituminous Research Inc., Pittsburg Pennsylvania, V. St. A., two-stage dust gasification system developed in the sixties shows a high potential for further developments. The preferred embodiment of the present invention is higher than the improvement of the Wanc'l construction of such a Two cases of dust pollution control are shown and described.

In the two-stage iqon Anleiqo, powdered coal is poured into a two-way or gasification stage introduced to a process gas and char? to produce coal ("char"). This char is made separated from the process gas, recycled and with oxygen and water vapor converted into hot combustion gas in a first or combustion stage. The term "combustion gas" used here refers to a gas consisting primarily of carbon dioxide and water vapor as well as smaller amounts of hydrogen and carbon monoxide. The hot combustion gas from the combustion stage is introduced into the already mentioned second stage and enters in contact with the carbon powder introduced in dio.se. Included

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the coal is primed and in contact with. the combustion gas and the steam are converted into synthesis gas, a certain amount of methane and carbon dioxide. In the prior art, this gasification reaction typically takes place at low gas flow rates of 0.61 to 3.66 m / s (2 to 12 ft. / Sec), pressures of about 60 atmospheres and temperatures of about 1200 ^° K. The dwell time in the second stage is essentially over 100 ms.

The pressure and temperature of the mineral in the first stage Combustion gases are such that in the second or before Tasungstufe the classic heterogeneous carbon / steam and carbon / carbon dioxide reactions to CO and H- take place.

When exiting the second stage, the exiting gases and the entrained charcoal can enter a cooling zone to cool the gas and char to an acceptable downstream process temperature. Thereafter the process stream is divided into its gaseous and carbon components.

This two-stage. " VerjüKungsverfahron is able to a tar-free and sulfur-free rim .. · η carbonation product in addition to deliver the gaseous product.

In gassing systems of the kind we are talking about, they say that The extent and speed of initial mixing related to. the warm-up speed of each Coal particles and you want for the individual coal particles Reach a warm-up speed that is only possible through the natural physical limit of heat conduction / convection a hot gas surrounding the coal particle is limited to the coal particle. This limit is for a particle with

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a diameter d - 20 μΐη in a hot gasification plant about "'" = 1ms, where d applies. In case of poor initial The system is "mixed-limited" ("mixing limited "), the dT / dt for the individual particles decreases and with it the final yield of volatile substances, as reactions play an essential role with low activation energy. So when the coal particles finally reach a temperature have reached, at which the high-temperature reaction can take place, it is too late for them to add another essential one To contribute.

The second type of mixing has to do with mixing the evolving volatiles with the "background" -H ₂ O and -CJ- to allow for a stabilizing reaction before cracking reactions between volatile hydrocarbons occur to produce foot and hydrogen.

The benefit of total gasification can be measured in terms of total capital and operating costs, and it is almost impossible to estimate the effect of a single process on the cost of the synthesis gas just by itself. It has already been shown that a total process has attractive capital and operating costs. One reason for this is that such a process makes good physical use of the oxygen and therefore only needs a minimal amount of oxygen - which corresponds to the goal of achieving a product stream of synthesis gas plus small amounts of methane, but is free of oils and tars that would then have to be reformed if syngas is the target. Less oxygen means that a smaller proportion of the carbon from the original coal is produced as CO ₂ (a higher amount of carbon is added to the amount of CO): i I: I .; You can get by with a small ion oxygen system, but also with less complex and extensive systems for removing the acid gas (CO2).

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The reactor or gasification stage uses K-O, not H_ as in the hydrogen gasification processes, and therefore you need not paying the price of making hydrogen for this purpose. Because of the use of high speeds and short Residence times in the gasification stage give the added benefit of a smaller and cheaper gasification reactor self.

In single-stage V (jrqu:; er. Η of this ArL the coal is converted into a
hot environment to »amines with oxygen and water vapor eiiKfo-splashes. While the Kohlt? Particles emit volatile substances
("devolatilize"), experience the evolving volatile
Hydrocarbons in the gas phase homogeneous reactions in the background mixture - they settle over the fastest
Reaction around, ie with oxygen. So the oxygen will
consumed and generated the required heat; one must
but to come to terms with the residues of charcoal that are heterogeneously reacted with the steam - a slow one
Inefficient reaction compared to reacting the char with oxygen. A better approach would be that
using valuable oxygen to burn and burn out the char, which is more difficult to implement, and the
Use steam (and the CO ..) to · stabilize the more reactive volatile substances. This is the approach and advantage of two-stage versus single-stage gasification. A single stage gasifier typically includes one or more very high temperature areas where coal oxidation has occurred but gasification has not progressed to any significant extent. In these areas, the coal slag typically rests on the walls
melted before the gasification chamber.

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The concept of the pyrolytic removal of volatile substances of the two-stage dust gasification process provides for a high Thermal efficiency compatible conditions when saubex-es heating gas should be generated. In the first or combustion stage, the char residues are preferably oxygenated in an almost stoichiometric mixture with carbon burned, producing primary carbon dioxide and hydrogen. The main goal of an establishment close to one Total combustion is not the production of hydrogen and carbon monoxide, as is the case with partial oxidation, but rather the provision of a heat source for the pyrolysis taking place in the second stage.

In the second or gasification stage, fresh coal is brought into contact with the product gases from the combustion stage at a temperature on the order of preferably about 1930 ^° C (3500 ^{° F).} With the support of rapid and efficient mixing at high temperatures, a pyrolytic release of volatile substances can bring about a degree of conversion of up to 60% and more of the carbon-carbon to the gaseous components. The use of water vapor in both combustion and pyrolysis provides a stabilizing background atmosphere that is intended to prevent the formation of solid carbon. The subsequent interaction between the erzeugton by the rapid release of the volatile substances chemical species yields a clean fuel gas which is free at an equilibrium temperature in the range of 870 ⁰ C (1600 ⁰ F) of #than and heavier hydrocarbons.

As can now be seen, it is desirable to betiroibon a gasification plant so that some Reroiche or plant parts are exposed to a flow with a very high temperature. This loading

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The formation of a molten slag layer can occur effect on the inner wall surface. A two-stage gasification plant can be optimally achieved with slag formation in the combustion stage, the coal injection area and in one part of the pyrolyser.

The technology in the field of gasification uses a wall construction typically from an outer pressure jacket with an inner lining made of a high temperature resistant material in the form of bricks or a poured or tamped material; this is the primary isolation structure. Is the Temperature in the gasification area high enough to melt the slag, as stated above, the high temperature resistant one is used Inner wall surface typically as a bonding surface on which one Slag layer can form.

The known wall construction, as explained above, is generally satisfactory for systems with large open spaces Areas, Slow Flow and / or Operating at Low Temperatures; Their main night, however, is that they do not boi over long periods of time. operate at higher temperatures leaves. Typically, the high temperature resistant material forming part of the wall becomes from the flowing slag melted unevenly, so that one is only partially isolated wall. In this way the heat losses can increase and the flow field in the carburetor can change accordingly distort the changed geometry of the wall structure. Another disadvantage is the thermal stress limit of such Wall, dir »a slow heating and cooling of the system required to avoid losses.

The present invention provides a wall construction for at least part of the wall '. · in a gasification area

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Gasification plant for converting carbonaceous matter into synthetic or heating gas, the gasification plant being of a type in which a flow of hot combustion products with a temperature of more than 1260 ⁰ C (2300 ⁰ F) and a speed of at least 30 m / s (100 ft./see.) is introduced into a gasification area with a separate stream of finely divided carbonaceous fuel. In this case, have the hot combustion products - including a slag containing at least mineral part components of which at least some are not fixed - a residence time of 1 ms to 100 ms in the part of the gasification area in which the temperature übet 1260 ⁰ C (2300 ⁰ F) lies. The wall construction is designed with an inner element that carries means to which the slag from the hot combustion products adheres, and with means to keep the inner element and the means carried by this at a temperature which is lower than the melting temperature of the Slag is.

Such a wall construction is specially designed in such a way that a stabilized flowing sludge layer can be used as the primary insulation for t? single and multi-stage Si aubvergasanlagen results. It can be a chilled metal, carbide or nitride structure containing high temperature resistant oxide elements and is constructed so that the temperature of the metal or high temperature resistant material nowhere approaches or exceeds the melting temperature of the slag. The selected high-temperature-resistant material can, for example, predominantly be a single oxide such as Al — O ₃ , MgO or ZrO or another high-temperature-resistant compound such as an aluminum or zirconium silicate. One method of manufacturing the wall is to work grooves into the hot surface of the cooled wall at right angles to the direction of the GaHütrömumj grooves and to make them square in cross-section

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or right-angled grooves, a high-temperature-resistant cement, for example phosphate-bonded zirconium oxide, can be poured in. According to another method, several layers can be flame sprayed onto the wall surface, which are graded from cermet to ceramic. The structure, the cooling and the type and dimensions of the ceramic wall have been chosen so that metal and ceramic temperatures are obtained within certain limits. The metal or other room material is preferably operated at as low a temperature as possible, but a temperature below the dew point of the working fluid is avoided. The ceramic component of the wall structure is preferably designed to operate thermally at a peak ceramic temperature that is lower than the melting temperature of the slag / ceramic compositions in order to avoid ceramic losses by dissolving in the flowing lick and washing out. Likewise, it is desirable that, during operation, at least part of the ceramic - for example near the center of the grooves or the like - is hot enough and, in the absence of a layer of slag, has a sufficiently low thermal diffusion ability to remove the droplets, particles or particles on it KlüsHigkoit separated slag? to tie. This is desirable to facilitate the formation of a bonded slag layer on an initially uncoated wall. The main advantage of the present invention is that it provides a stable and predictable wall construction that is compatible with high temperature dust gasification operations. It has the further advantage that the wall areas to be coated with slag can be precisely determined by the choice of the wall structure. While the walls in the high-temperature areas can be designed to accommodate a layer of slag and the advantages that can thereby be used can be used, the downstream walls can be built up in such a way that slag accumulation is avoided, so that low-temperature areas can be used in the areas

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Avoids contamination. The invention has the further advantage that it is suitable for both one and two-stage gasification plants. It has the further advantage of being controllable and erosion-resistant structure exposed to high temperatures and flow rates Provide areas of a gasification plant.

A potential disadvantage of the present invention is the considerable amount of heat that can be lost through a cooled wall structure in a system with a large open wall area. On the other hand, the invention is ideally suited for use in a dust gasification system operating at high flow rates, because only a relatively small system and a correspondingly limited wall surface are required for a high to very high throughput. As a result of the amount of heat that is necessarily lost through the gasifier walls according to the present invention, the present invention can only be used with advantage in certain types of gasification plants. These are the dust gasification plants that work with temperatures of locally more than about 1260 ⁰ C (2300 ⁰ F) and a flow velocity of at least about 30 m / s (100 ft./see) and in which the gas in those parts of the plant , in which the temperature is higher than 1260 ⁰ C (2300 ⁰ F), has a dwell time of about 1 ms to 100 ms.

The invention will now be described in detail with reference to the accompanying drawing explained.

Fig. 1 is a partial sectional view of the giner wall construction according to the present invention;

Fig. 2 is an enlarged section through

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-U-

the wall structure according to FIG. 1 with a layer of slag deposited on the inner surface.

As the present invention focuses on providing improved Wall structures for gasification plants are aimed at the construction and operation of gasification plants not to be further inaganyon even here.

As Fig. 1 shows, a part of a wall structure, which surrounds a gasification stage or the gasification area of a gasification plant, an outer pressure jacket 10 made of metal and an inner wall portion 11 made of metal, which is spaced from the pressure jacket so that a flow area between them 12 arises for a coolant. The coolant such as water is in the flow area 12 in conventional Manner with manifolds 13 in and out of it to extract heat from the inner wall 11. In the exposed surface of the inner metal wall 11 is a Series of grooves 14 are provided which are substantially rectangular to the direction of the gas flow, which in the present example, as shown by the arrow in Fig. 1, from the left runs to the right. In each groove there is a high-temperature-resistant material 15, which is expediently is a high-temperature-resistant cement such as phosphate-bonded zirconia.

The protective slag layer 16 that forms during operation as explained in more detail below, is shown in Fig. 2, but not in Fig. 1, since the latter is the wall structure the gasification plant according to the present invention before actual use / · shows.

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The wall construction is designed according to the working conditions of the gasification plant so that the inner metal wall and the high temperature resistant material 15 carried by it at a temperature below the slag melting temperature of the coal or the other carbonaceous material used. The grooves 14 can, for example, have a width of approximately twice the local equilibrium thickness of the slag layer, a depth approximately equal to or greater than the width and one Have the spacing of the metal or other suitable wall material approximately equal to the groove width. The local equilibrium thickness the slag layer is determined by the working conditions of the gasification plant, the properties of the slag and the thermal Wall construction and can typically be in the range of 1 to 10 mm. Providing the high temperature resistant Material on the inner surface is essential to initiate the slagging that will eventually result in a Covering the inner wall 12 leads.

The grooves only need to be deep enough to hold the high temperature resistant material and only wide enough to hold the slag adheres to the high-temperature-resistant material and continues to accumulate there, as described in more detail below. The distance of the grooves between each other should not be larger than the one that allows slag to be bridged from one groove to the next.

When starting a gasification plant with the wall construction of FIG. 1, the slag initially begins with the high-temperature-resistant one Material-filled grooves 14 to adhere. The formation of local bumps or the like typically causes that little cinder finger over the exposed metal between flow in the grooves (due to the high shear stress from the gas flow or due to gravity). Follow these fingers wider curtain-like structures until the exposed metal

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is locally bridged and a continuous flowing layer of slag develops.

Typically, chop forms the continuous flowing layer of slag finally as a result of the shear flow in the direction of the gas flow, which is near the upstream end of the wall structure or begins in an area of heavy slag deposition on the wall. Fig. 1 shows - for a clearer illustration enlarged - the grooved wall structure with a continuous insulating slag layer 16 on the exposed Inner surface of the inner metal wall 11.

When operating at high temperatures, it can be expected that the slag ^{surface will equilibrate at about 1370 to 1650 °} C. (2500 to 3000 ^° F), as determined by the shear and physical forces on the slag. The viscosity of the slag is strongly dependent on temperature. The peak values of the temperatures of the metal wall Fuei such temperatures the slag surface can be in the range of about, for example, 150 to 260 ⁰ C (300 to 500 ⁰ I) keep; chemical corrosion takes place slowly and they allow the wall structure to be kept intact for a long time.

In general it can be expected that the qualitative growth behavior and the equilibrium conditions ("steady state conditions") the slag layer on the grooved wall surface is substantially independent of both the wall surface and the gas velocity are up to supersonic velocities. It can therefore be embodiments of the invention with internal Make walls made of different metals and gas flows up to the supersonic range.

During operation, the boundary layer slag transport and the shear flow are the primary causes of slag deposition

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on the wall. The re-entry of the slag into the gas flow - along with a breakup of droplets and one Surface evaporation - are the main causes of slag depletion. A locally steady stream of slag constant thickness is generally the result of a balance between the local deposit and the local Shear flow of the molten slag.

If desired, the grooves can be omitted; instead can one the entire inner surface of the metal wall 11 according to the present Invention with a flame-sprayed smooth and continuous layer as a basis for the adhering slag Mistake. Such a layer can be applied, for example by flame spraying successively layers of graded conventional cermet material or applies graded layers of a conventional cermet material up to a conventional ceramic Coating can, for example, consist of up to four or more layers, each with a thickness of 5 to 30 μm or more exist. The coating material can be present in a conventional manner as a powder, which is a conventional one Oxyacetylene flame spraying device supplies.

An advantage of a flame sprayed interior wall according to the present invention Invention over a grooved wall structure is that. the flamingo syringe wall a more even slag formation causes the slag to bind more firmly to the wall surface. Furthermore, flame-sprayed walls tend to like described above, in addition, their slag layer also during the transition and equalization processes during the running-in and Shut down to hold on to the entire inner surface of the wall longer.

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At a point down the stream the temperature is so high sunk so that the slag solidifies. Upstream of this point and / or where the slag formation on the inner wall surface is undesirable, this can be achieved by using a cooled, but otherwise smooth metal, nitride, Provides carbide or other surface that is not wetted by the slag. It can be an open, smooth one Act surface of the inner metal wall 11. Furthermore, there is the possibility of slag deposits at such a point further decrease by reducing the inner wall area runs slightly divergent and thus reduces the inclination of the slag, the wall surface at this point to touch, the impact of again entrained slag on the downstream wall parts prevents and thus the erosion keeps minimal.

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Claims (9)

AVCO EVERETT RESEARCH LABORATORY, INC., 2385 Reserve Beach Parkway, Everett, Massachusetts, V. St. A. P a I η t a η s ρ r ü c h ο 1. Ward construction for at least part of the wall in the gasification area of a gasification plant for converting carbonaceous matter into synthesis or heating gas, whereby in the gasification plant a stream of hot combustion products with a temperature of over 1260 ⁰ C (2300 ⁰ F) and a speed of at least 30 m / s (100 ft./sea.) is fed into the gasification area together with a separate stream of finely divided carbonaceous fuel and the hot combustion products contain a slag with partially mineral components, at least some of which are not solid, and the residence time in that part of the gasification area, in which the temperature ^{exceeds 1260 0} C (2300 ⁰ F), is 1 ms to 100 ms, characterized in that the wall construction (10 to 15) is designed with an inner element (11) which has a device (15 ) carries, to which the slag from the hot combustion prod- ucts adheres, and that still a Einr icht 130066/0682 _ ο - (12, 13) is provided that the inner element and that of this means carried at a temperature below the melting temperature hold d'3r slag. 2. Wall construction according to claim 1, characterized in that the inner element (11) consists of metal and the device (12, 13) for maintaining the temperature is a coolant arrangement for removing heat from inner elements. 3. Wall construction according to claim 1 or 2, characterized in that the device (15) carried by the inner element (11) is a material which remains intact in the operation of the gasification plant. 4. Wall structure according to one of claims 1 to 3, characterized ekennzeichnet g, that carried by the inner member (11) means (15) is a high temperature resistant material. 5. wall construction according to claim 4, characterized in that dal the high-temperature-resistant material in grooves (14) inside Element (11) is arranged. 6. Wall construction according to claim 5, characterized in that the grooves (14) are spaced from one another and extend at least substantially at right angles to the direction of the gas flow in the gasification area. 7. Wall construction according to one of claims 1 to 4, characterized EKENN g is characterized in that carried by the inner member (11) means is a coating which retains its integrity during operation of the Vergasuncjijnnl age ;. 8. Wandkon:; l; ruk I-lon according to one of claims 1 to 4, since durc h g eke nn ze leans that the inner element (11) carried 130066/0682 Furnishing a «.: Coating made of a high temperature resistant Material is. 9. Wall construction according to claim 2, dadur ch gekennzeichn et that the device carried by the inner element (11) is carried by this only where the construction (10 to 15) forms said part of the walls of the gasification area, but on the inner There is no metal element where the wall construction forms another part or parts of the wall. 130066/0682