DE2624857A1 - PROCESS FOR GASIFICATION OF CARBON MATERIAL - Google Patents

Description

Bamag Verfahrenstechnik GmbH Wetzlarer Strasse 136

6308 Butzbach / Hesse

Process for the gasification of carbonaceous material

The invention relates to a method for continuous gasification of solid, carbonaceous fuel under selective conditions to produce one of carbon monoxide and hydrogen rich and, if desired, methane-enriched gas and methods of using this method of production of heating gases with low and medium calorific value, motor gas (i.e. gas for driving turbines), reducing gas, Methanol and ammonia.

In the private and technical sectors, coal has been replaced by oil and gas because it is more difficult to handle than other fuels has a residue to be removed and generates dust and dirt when used. In the non-Arabic Countries, the domestic oil and gas sources no longer meet the growing demand for fuel. By the sudden End of a period in which there was very much based on petroleum and natural gas as dominant forces in the economy

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Energy, coal became an important source of energy again. Fortunately, there are large reserves of coal. Those in the United States mined coal could provide more than 100 times the energy consumed by the United States in 1973 " The possibility of using these coal reserves depends however on the availability of a mature technology for the effective and economical conversion of the same into more usable energy sources. If this technology is in technical If the scale is to be usable, it would have to be used for extensive production (e.g. technical quantities) of e.g. gasified products should be suitable. In addition, in view of the current environmental protection legislation, the conversion would have to be carried out the coal is done in an environmentally friendly way.

An object of the invention is to provide an efficient one Process for the continuous gasification of solid, carbonaceous material under selective conditions, the in an environmentally friendly way the economical conversion of considerable amounts of this material into synthesis gas, i.e. an Carbon monoxide and hydrogen-rich gas made possible. Another task is to provide a process that allows gasification carbonaceous solids from lignite to coal and coke, baking and non-baking coals and coals with high Ash content permitted in a wide range of grain sizes. Another task is to create a process that will operate during operation is largely insensitive to fluctuations in the charcoal properties, i.e. ash content, moisture content, etc. Another task is to create a process that

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uses a fluidized bed in the state of motion for intimate mixing of the fuel particles in order to promote a uniform temperature between the solids and gases and to enable the gasification conditions to approach equilibrium in a short time. A further object relates to the creation of a method using fluidization and gasification media in which very few operating or maintenance measures are required and very high operating factors can be achieved. Another object relates to the creation of a method that can use air and / or oxygen as a gasification medium _{or the like}

Another object of this invention is to provide a method which can increase gas production per unit cross-sectional area of the reactor and decrease overall gasifier compression requirements guaranteed. Another task is to create a process that is straightforward and therefore is free from malfunctions and fluctuations in the operating conditions in a given area without major adjustments the system allows.

Another object of the invention is to provide a method in which the incoming coal is degassed and the volatile exhaust gases do not need to be separated and collected, but instead are consumed in the process so that an environmental problem is eliminated. Another job is the creation of a process that is carried out in a single-stage operation in a fluidized bed of carbonaceous material

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and a large amount of product gas per cross-sectional unit of the reactor (e.g. depending on the operating pressure 9754 Nm3 / h ° m2 or more) so that the size of the equipment required to penetrate a given volume of gas is reduced to a minimum can be. Another object is to create a method that eliminates all of the compression effort is reduced in the gasification plant, so that for the Product compression stations to be expended capital costs as well as the daily operating costs for the energy of the product gas compression can be reduced to a minimum. Another object is to create a method in which a highly effective system part for removing finely divided material the product gas is used to create a satisfactory product, but the product gas is still sufficient Pressure retains so that it can only be processed further with little and usually without additional compression can.

A further object is to create a process that can be operated in interacting multiple stages (strands) can, so the large capacity required in the current technical operating systems with acceptable economic efficiency to reach. Another object is to provide a method that is used in methods of manufacture, in particular technical production of heating gases with low / medium calorific value, fuel gas, reducing gas, methanol or ammonia can be economically integrated to produce these products at economically interesting costs. Another

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The task is to create a process for the production of heating gas in which a high conversion of the fuel components (e.g. 85 - 90%) can be achieved in a heating gas with a high calorific value.

Carbonaceous material, such as coal, often contains Sulfur, which is obtained during gasification in the form of gaseous substances such as carbon oxysulphide, hydrogen sulphide and the like. These Sulfur-containing constituents can be disadvantageous both in product gas combustion as a fuel gas and in synthesis. For example, the combustion of fuel gas containing sulfur compounds produces sulfur dioxide, which is an undesirable one Polluter is. When used for synthesis, the sulfur can adversely affect the catalysts used, i.e., be a catalyst poison and lead to the formation of undesirable by-products in the synthesis product. It is therefore desirable to reduce the sulfur content of the product gases to at least a concentration that is acceptable for the environment or for synthesis.

Another object is to create a gas stream under increased pressure, so that when the gas stream is desulfurized, a slight compression is required to achieve the desulfurization pressures _{or the like}

According to the method according to the invention for continuous gasification of solid, finely divided, carbonaceous material under selective conditions with the formation of a carbon monoxide and hydrogen and, if desired, methane-rich products

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duct gas becomes the underlying fluidization medium in this material and the oxygen-containing gas (the underlying Gasification medium) with controlled feed speeds and under certain conveying conditions in an enclosed Carburettor introduced. The gasifier contains a confined fluidized bed of the material as a lower dense phase with an upper and a lower phase boundary. Gases escaping from the fluidized bed and entraining particles essentially form in the gasifier an upper thinned, discharged finely divided material containing gas zone, which is at the upper phase boundary of the fluidized bed adjoins.

The carbonaceous material is fluidized in the bed with selective amounts of fluidizing medium and oxygen as it is fluidized containing gas degassed, carbonized, oxidized, hydrogenated and gasified under selective conditions (these processes are summarized below under "gassed"). The crude product gas is generated under selective conditions to prevent undesirable formation to reduce to a minimum or completely eliminate hydrocarbons as by-products.

The gaseous crude reaction product passes through the dilute gas zone, so that the top product is a gaseous carbon monoxide and hydrogen and, if desired, methane-rich product, which is usually undesirable finely divided material (e.g. partially used coal), and the bottom product is an ash product (e.g. partially used coal) that consists of particles consists that are larger than that of the fluidized bed. The ashes

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product travels down the bed and becomes at the bottom of the gasifier carried out. The top product leaves the carburetor below Operating pressure and high temperatures (e.g. about 815 to 1205 C); the product gas is cooled (to temperatures from about 93 to 26O ° C), whereby its heat content is recovered and substantial amounts of partially used coal are removed. The won Heat or part of it is used to advantage to generate steam, part of which is consumed in the process. The cooled product gas that has been cooled in a heat recovery zone and is under the pressure of the heat recovery zone, which is lower than the pressure in the carburetor is advantageously passed through a high-performance scrubber with a high pressure loss, to remove fine, partially spent coal particles and recover a product gas that is less than about 3.53 (e.g. less as about 0.35) solid particles per Nm3 gas, at least about 10% by volume of carbon monoxide and at least about 10% by volume of hydrogen and has a calorific value of at least about 800 Kcal / Nm3. The pressure in the carburetor is advantageously through a Maintain back pressure control, which takes place on the gas system at a point downstream of the carburetor.

The carbonaceous material can be coke or coal or other solid material consisting essentially of carbon. The charcoal can be bake, moderately bake, and non-bake. If charcoal is used, it must be ensured that the Feed material exposed to elevated temperatures when introduced into the gasifier does not cause harmful agglomeration learns. Typical coals are lignite, sub-bituminous and bituminous coal, etc. In general, the required

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The more reactive the coal, the lower the gassing temperature is =, The carbonaceous material may contain ashes because according to the present method the ash is removed from the gasifier, although with the ash there is also a loss of tangible Heat enters = The carbonaceous material fed to the carburetor can be of different quality and the process can be easily switched from one type of coal to the other without physical change. To simplify the Disclosures are treated below as an example of carbonaceous material coal.

The fluidized bed used according to the method can process very different particle sizes of the coal; fine and coarse particles can be used at the same time _o The coal fed to the gasifier is generally in the diameter size range of up to 9.5 mm. The mean particle size is often around 2.4 to 4.8 mm. The coal may be dry, for example, _o a moisture content of less than 10 wt .-% have, even if before feeding to the gasifier not always drying is necessary, "The use of carbon can often up to 20 wt .-% or more of water contained

The fluidizing medium is basically steam, which also serves as a reactant. It can also be air, carbon dioxide or recycle gas, each with or without steam. For the sake of simplicity, the fluidizing medium is given below by way of example as steam. Steam is particularly suitable as a fluidizing medium; it can also serve as a diluent gas for the gasification medium, since it

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condensed and easily separated from the product gas, leaving behind a product gas with a higher calorific value » Steam is readily available even with the pressures used and can advantageously be generated with the help of the waste heat generated by the overall exothermic nature of the process arises.

The gasification medium is in principle the oxygen-containing gas; it also contributes to the fluidization of the bed. It contains free or bound oxygen that is available for reaction with carbon _o It may be oxygen or oxygen with diluents, for example air or oxygen-enriched air, preferably it is introduced at a plurality of spaced locations in the bed. Diluents for the gasification medium can be used, specifically in amounts which are greater than the amount required for the gasification reaction. Carbon dioxide, recycled product gas, nitrogen and the like can be used. However, steam is preferred, inert diluents such as nitrogen reduce the temperature in the gasifier and lower the calorific value of the product gas per unit volume of gas. A diluent such as carbon dioxide can participate in the reaction to form carbon monoxide; Such a reaction is endothermic. »If the product gas is to have pipeline quality, eg as a heating gas with a medium calorific value (approx. 2490 Kcal / Nm3), an oxygen-containing gas that contains as much nitrogen as air is not permitted. On the other hand, if the product gas is used for synthesis purposes, for example for ammonia, air or air enriched with oxygen may be suitable as the oxygen-containing gas, but oxygen is preferred. If the desired product is methanol

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is, oxygen is preferably used alone. Air is suitable for the production of heating gas with a low calorific value or of fuel gas (about 1110 Kcal / Nm3). If the oxygen-containing gas contains diluents, it must be suitable for the desired pressure a larger volume of gas can be compressed in the carburetor. When air is used as the oxygen-containing gas, it is preferred Air together with steam as a fluidizing medium; when oxygen is used as the oxygen-containing gas, it is preferred Steam alone as a fluidizing medium. The fluidized bed shows a clear upper surface or phase boundary that looks like this as if it were the surface of a boiling liquid In general, the height of the fluidized bed is about 1.3 or 1.5 to 3 times the height of the bed in more compact Shape. The bed losses arise not only from the conversion of solid material into product gas, but also from the removal of ash particles (if the coal contains ash) from the bottom of the bed and the removal of small particles caused by entrained gases flowing upwards in the carburetor. It is therefore desirable to maintain product gas generation, to refill the bed with new coal. The coal is preferably fed into the gasifier directly at the upper phase boundary or above or below into the fluidized bed at a pressure slightly above the gasifier pressure and temperature from about ambient to 204 ° C or 316 ° C or 538 ° C. The introduction takes place in order to maintain the continuous gasifier operation with an essentially continuous one Rate of addition and in such an amount that the upper phase boundary at a level of about 1.20 m to 6.10 m above the lower phase boundary of the fluidized bed

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where the ratio of the height of the dilute phase to the height of the fluidized bed is about 3: 1 to 10: 1.

The primary gasification (e.g. oxidation or reaction) of the coal takes place in the fluidized bed. The coal particles gassed in the bed have an average dwell time of around 30 to 100 minutes »This dwell time is much longer than the dwell time of the Gas product (about 3 to 50 seconds). The residence time of given particles in the bed is sufficient to absorb substantial amounts of the to oxidize available carbon to carbon monoxide. The bed experiences strong agitation, primarily from the fluidizing medium takes place with the help of the gasification medium. As mentioned above, this agitation can be described as a boiling motion.

The oxygen-containing gas, preferably with up to 50, eg about 0.1 to 50 volume _o -% of steam and, in general, an average overall temperature of up to about 538 ⁰ C _7, for example, about 38 to 538 ° C, and at a pressure slightly above of the gasifier pressure, is preferably introduced into the gasifier at spatially separate, substantially evenly distributed locations at different heights, in amounts sufficient to bring it into contact evenly with the constituents of the fluidized bed under controlled selective reaction conditions and to gasify these components. The temperature of the oxygen-containing gas should be as high as possible in the stated range to maximize overall performance. Preferably, at least about 50% by weight of the steam fed to the fluidized bed becomes spatially at the lower phase boundary of the fluidized bed

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separate, essentially evenly distributed over the circumference Set generally at a temperature up to about 649 ° C and a pressure slightly above the carburetor pressure and speed introduced, which is sufficient to fluidize the lower part of the bed.

Every place of the bed is due to the one created by the fluidized bed Stirring strives to assume the same temperature with respect to the time. However, the composition of the fluidizing medium and the distribution points for the introduction of the fluidizing medium into the bed serve to accommodate changes in the temperature profile in the bed, which can lead to product gases of different quality. For example, the Coal particles in the lower part of the bed come into contact with steam. The steam is preferably in the lower level of the bed blown in to stir up the particles and preferably heat from the ash particles emerging at the bottom of the bed (e. B. particles from partially used coal) to win and to cool these particles and so preheat the steam. In a similar way Way, a portion of the oxygen-containing gas can be fed to the upper part of the bed in order to reduce the remaining To oxidize carbon. Another portion of the oxygen-containing Gas, preferably up to about 10% by volume, e.g. about 0.1 to 10% by volume of steam, can be at or just above the phase boundary between the fluidized bed and the dilute phase at spatially separate, substantially uniformly distributed over the circumference Places are introduced in sufficient quantities so that they react with the carbon fractions leaving the fluidized bed

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yaw, increase the temperature in the dilute phase, increase the carbon conversion of the process and a crude product gas provide which contains at least about 50% of the oxidized carbon as carbon monoxide.

The surface of the bed adjacent to the phase interface, i.e. the Interface between the bed and the dilute-phase gas zone can generally have higher temperatures, since the primary oxidations take place there and this area with the hot Reaction gases from the lower parts of the bed is in contact.

The gasification reactions occurring in this process include the carbon oxidation and the reduction of carbon dioxide with formation of a product gas which essentially contains carbon monoxide and hydrogen. The starting materials are Coal and Oxygen Supplied by the Oxygen-Containing Gas and Steam »The basic gasification reactions are as follows:

C + 02 = C02 (exothermic)

C + 0.5 02 = CO (exothermic)

C + C02 = 2 CO (endothermic)

C + H20 = CO + H2 (endothermic)

C + 2 H20 = C02 + 2 H2 (endothermic)

C + 2 H2 = CH4 (exothermic)

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The speeds of these reactions are favored by increased temperatures. The coal in the fluidized bed is advantageously gasified at a maximum temperature in the gasifier in the range of about 816 to 1316 ° C. Preferably, the main temperature is in the dense phase below the softening temperature of the ash contained in the material "It is a gaseous reaction product is produced containing carbon monoxide, hydrogen, carbon dioxide, methane, and diluent, and in the dilute phase passes _o At the same time result in the gasification of solids from partially used coal. The temperature in the dense phase of the gasifier is preferably kept about 28 ° C. below the softening temperature of the ash. The temperature used depends on the amount of diluent gas in the fluidizing and gasifying media, the type of coal, the softening temperature of the ash, the heat tolerance of the gasifier and the like. In general, the temperature is at least about 816 to about 1316 ° C. or more, and to achieve a good heat output, preferably about 927 to 1093 or 1204 C. The dilute phase advantageously has the highest possible temperature, as far as this is compatible with the properties of the ash contained is compatible.

The reactions in the gasifier are advantageously carried out under positive pressure, generally above 1.5, for example from about 1.5 to 20, with advantage from about 2 or 2.5 to 15 and preferably from about 6 to 14 ata. The selection of the one applied in a given plant Overpressure depends on the design and the pressure tolerance in the processing plant, the pressure drop in the plant downstream of the carburetor, the desired special use

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generation of the product gas and the like, as well as whether multiple carburetors be used in strands. The use of higher reaction pressures according to the invention also favors the degree of utilization the coal for the product gas generation and increases the gasifier throughput.

This process uses selective amounts of coal, oxygen-containing gas, and steam, depending on several variables, to maintain operating conditions (e.g. temperatures), the calorific value of the product gas, and the rate of production. The total amount of steam used should be sufficient to keep the bed in the desired fluidized state and temperature. A particular advantage of the present method is that the steam required for the fluidization and gasification can be obtained by utilizing the process heat for steam generation. This results in a cooled product gas, preferably with less than about 141 solid particles per Nm3, for example at gasification pressure and at temperatures more suitable for further processing, with substantial amounts of partially consumed coal from the raw product gas for the purpose of extraction from the process, recycling or the work-up can be removed under other conditions and the cooling of the product gas to temperatures of about 93 to 260 C takes place in a heat recovery zone. It can be produced, an excess of high-pressure steam on the required in the process amount of addition "This excess is, therefore, to drive the turbine of the product gas compression and in the case of using air to drive the air compressor available _e In general, up to about 60 % By weight partially

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spent coal withdrawn from the bottom of the bed and advantageously with steam introduced into the bed at the lower phase boundary brought into contact, whereby the sensible heat of the spent coal is recovered and used for steam preheating.

The ratio between coal and oxygen-containing gas is intended to generate a sufficient amount of heat through oxidation reactions allow for the maintenance of gassing; However, the amount of heat should be less than the amount of heat that would lead to an excess production of carbon dioxide (e.g. less than about 15 to 20% by volume). At a constant coal feed rate the ratio of oxygen containing gas and steam to coal is used to maintain the desired Bed temperature controlled selectively. If air is used as the gasification medium, it can be used to provide the Air required for coal gasification can advantageously be used with compressors driven by a steam turbine will. As mentioned above, additional proportions of steam or oxygen-containing gas can also be present on or near the bed surface can be selectively injected in order to enter the dilute phase to further gasify discharged carbon particles. This blowing in takes place at a sufficient height so that a further gasification of the entrained coal particles and a separation of a Part of the solid material carried away is possible.

The gas and particles discharged from the fluidized bed form a dilute, discharged particle immediately above the bed containing gas zone. Unlike the bed, this one has thinned

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Phase no upper phase boundary or surface. Rather, it expands in the given by the closed gas generator Room off; their dimension will therefore be determined by the dimensions of the surrounding gasifier. The entrained particles will be usually withdrawn from the dilute phase together with the product gas.

The level of the dilute phase containing the entrained particles ensures that the particles have an additional length of time remain under the gasification conditions so that gasification continues and some of the solid material from the diluted Phase returns to the bed before the product gas leaves the gasifier, the level of the dilute phase compared to the bed can be varied. For example, it can be reduced to increase the amount of particulate matter discharged increase, however, if the level of the diluted phase is insufficient too large amounts of carbon can be lost from the gas generator walk. The upper part of the gas generator can have a larger diameter than the lower part, so that the gas velocity decreases and consequently increases the residence time of the particles in the dilute phase and the return of entrained particles is favored in the fluidized bed. With a usual particle size distribution of the feed material, about 40 to 70% of the the solid material leaving the gasifier is removed in the form of the product withdrawn from the diluted phase. In general the height of the dilute phase is about 3 to 10 times, preferably about 4 to 8 times the height of the fluidized bed. Another way to increase the time that the fine coal particles are exposed to the gasification conditions is

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the recycling of part of the separated in a hot cyclone Money.

That from the conversion of carbon, steam and oxygen containing Gas-generated, crude, gaseous reaction product generally has a residence time of about 20 to 50 seconds, preferably about 5 to 30 seconds, in the upper dilute phase of the carburetor. The superficial velocity of the raw product gas through the carburetor is well above the point of incipient turbulence and generally extends up to about 6 m / s in Dependence on the operating pressure.

The product gas is rich in carbon monoxide and hydrogen and generally contains, for example, about 50 to 90%, preferably about 55 to 85% carbon monoxide based on the total carbon oxidized. The remainder of the oxidized carbon is essentially carbon dioxide. Smaller amounts of methane can also be present; generally less than about 10% or even less than 6% of the carbon in the product gas is present as methane. Larger amounts of methane (e.g. more than about 10% and up to about 35%) can be generated in the gasifier under conditions that favor methane formation. The presence of the methane is advantageous if the product gas is used as heating or fuel gas. The amount of methane produced is reduced by the the operating conditions applied to the gasification. Favorable conditions for methane formation are the use less Steam quantities (if steam is used), whereby the omitted steam quantity is completely or partially replaced by recirculation gas,

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Temperatures in the range of about 816 to 927 ° C and pressures in the carburetor of at least about 10 ata. Furthermore, the coal introduced with advantage above the upper phase boundary of the fluidized bed.

In the production of heating gas by the process according to the invention, the cooled product gas is desulfurized if desired. Appropriately A two-stage process for desulfurization is used, the first stage being the sulfur compound in the form an acidic gas, namely as hydrogen sulfide, which is then selectively absorbed from the gas. Carbon oxysulfide can be converted to hydrogen sulfide, for example by hydrolysis. The hydrolysis can preferably be carried out in the presence of a carbon oxysulfide hydrolyzing catalyst under a pressure greater than about 4.2 ata at the hydrolysis temperature, e.g., about 93 to 205 C. The amount of water sufficient for hydrolysis is often contained in the cooled product gas. the Reaction is exothermic.

The outflowing product is generally cooled to the absorption temperature, ie. on temperatures at which the Equilibrium is favorable for hydrogen sulfide absorption. The gases are mostly at a temperature of around 21 to 38 C. cooled before they enter the absorption unit, the absorption can be carried out with a conventional selective absorbent for hydrogen sulfide. Typical absorption systems are, for example, the alkazide process and the Stretford

about 21 to 38 ° C, preferably under a pressure of more than

Processes The absorption is mostly at a temperature of

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4.2 ata performed. The used absorption solution can be regenerated where a rich gas containing hydrogen sulphide arises «From the gas containing hydrogen sulphide can be done in the usual way, e.g. through the Claus process, more elementary Sulfur can be obtained; the Claus process can be supplemented by a sulfur dioxide absorption system, so that one for the Environmentally tolerable exhaust gas is produced.

The gas from the gasification process can be used for synthesis of chemicals, for _o example, ammonia and methanol are used _o In this case, the coal into the gasifier advantageously introduced at or below the top phase boundary of the fluidized bed. The general reactions for the production of methanol and ammonia are

CO + 2 H2 * ■> CII30H

C02 + 3 H2 - + » CH30H + H20 and

3 H2 + N2 - ^ 2 NH3

The cooled product gas is rich in carbon monoxide and hydrogen. Ο Since each of these syntheses requires considerable amounts of hydrogen, the product yield can be improved by converting the gases on a suitable, sulfur-resistant catalyst. When converting to react carbon monoxide and water vapor in a molar ratio of 1: 1 to form hydrogen and carbon dioxide for methanol synthesis _o is frequently a gas having about 2 to 2.5 moles of hydrogen

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Often used per mole of carbon monoxide and carbon dioxide Shift reaction relatively effective, and a product gas stream can bypass around the shift reactor and with the exhaust gas of the shift reactor are combined, so that a gas with the desired proportions of hydrogen to carbon oxides disfigured No carbon monoxide is required in the production of ammonia. Therefore, the conversion reactor delivers Exhaust gas with less than about 3, preferably less than about 2% by volume of carbon monoxide. The conversion reaction is generally carried out at a temperature of about 260 to 482 C under a pressure of more than 14 ata. It can be seen that an increased production of carbon monoxide and hydrogen according to the present invention increases the yield of the synthesis product increases.

The exhaust gas from the conversion reactor is preferably desulfurized. At the same time, excess carbon dioxide can be removed _o The sulfur compounds usually present as hydrogen sulfide and carbonyl sulfide, are removed simultaneously with the carbon dioxide excess by absorption. Physical absorbents are most effective for this purpose. The absorption takes place preferably at pressures above 42 ata. The absorbent can be regenerated by heating and relaxation, and the released gas rich in hydrogen sulfide can be converted into elemental sulfur.

Carbon oxides and hydrogen gas are converted to methanol in a known manner processed, for example according to the ICI method, the

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mostly uses pressures of about 105 ata; it can also be low Pressures of 52.5 ata with the same catalysts for the methanolhers application. At the increased pressure used in the present invention, the increased throughput allows for a reduction the size of the plant and a reduction in the cost of compressing the synthesis gas.

When the desired product is ammonia, these are in accordance with the invention The gases produced are also subjected to the above-mentioned conversion and removal of acidic gas components. To it closes the final cleaning and the adjustment to the stoichiometric Ratios using a gas scrub with liquid nitrogen. The ammonia synthesis occurs after a the usual procedures, such as the ICI procedure, most of the time Pressures greater than about 140 ata and temperatures in that range from about 315 to 538 ° C. As a result of the increased pressure according to the invention, the increased throughput allows a reduction the size of the plant and a reduction in the cost of compressing the synthesis gas.

The invention is explained with reference to the drawing and to examples explained in more detail. Show it

Fig. 1 is a schematic flow diagram of an embodiment of the invention Process for coal gasification under selective conditions to one rich in carbon monoxide and hydrogen Product gas;

Fig. 2 is a schematic flow diagram of an embodiment of the

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inventive method for generating heating gas;

Fig. 3 is a schematic flow diagram of an embodiment of the invention Process for the production of methanol and

Fig. 4 is a schematic flow diagram of an embodiment of the invention Process for the production of ammonia.

In Fig. 1, a gasifier 10 with a fluidized bed 12 and a dilute phase 14 is shown. He is usually trained that the base is a frustoconical section in which the base of the bed is located. The respondents become united in the bed.

The solid material is fed to the gasifier 10 in the following manner. Broken coal is fed to the conveyor 16 and transported to the feed hopper 18. The conveyor system 16 can be a conveyor belt, bucket conveyor or the like. Appropriately a chain conveyor is used because it usually does not jam and does not come to a standstill, when the container is full.

The bunker 18 supplies broken coal to two lock bunkers 22 and 22. In practice, especially when operating under pressure of more than 2.5 ata, it may be desirable to provide additional lock bunkers, so that a continuous coal supply to the carburetor is guaranteed. The lock bunkers allow a pressure increase in the vicinity of the coal except for one for the

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Introducing the gas generator suitable value. In general, the coal charge is subject to gas backflow to avoid it a pressure that is greater than the pressure in the carburetor. Other methods can be used to bring coal to normal pressure to bring on increased pressure.

The lock bunkers work in cycles. In the first stage of the cycle, the lower valve of the bunker is closed and the upper valve is opened so that the lock bunker can be charged. When the lock bunker has been charged, the upper valve is closed and a gas is introduced to increase the pressure. Finally, the batch is emptied through the bottom of the bunker under increased pressure. The batch falls into the holding hopper 24. The introduction of the pressurized gas, for _o example, an inert gas such as nitrogen or carbon dioxide, in the batch hopper of the charge transfer can be continued during the discharge for the purpose of acceleration.

Coal is conveyed from the holding bunker 24 to the gasifier by a screw conveyor, which is shown schematically by the line 26 transported. To better distribute and improve the operational characteristics of the process for a given product the coal can be introduced in several places. Means of transport can also be used to advantage, including Rotary feeder and the like.

The fluidizing gases are often blown into the gasifier at several points _o In this way, the reaction of the dense bed

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phase can be controlled so that the coal utilization increases and a product gas of high quality results. As shown, will a stream consisting essentially only of steam (100%) through Line 28 introduced at the lower phase boundary of the fluidized bed. The steam not only serves as the primary fluidizing gas, but also for cooling the ash particles (e.g. also particles from only partially used coal) for the purpose of discharging them from the Lower part of the gas generator. An oxygen-containing gas is introduced through the lines 30, 32 and 34, which also contains the May contain steam as a diluent. The oxygen and the diluent steam aid the gasification and carry together with other diluents in the oxygen-containing gas for bed fluidization and temperature control, Line 34 carries the oxygen-containing gas preferably at or just above the phase boundary between the bed 12 and the diluted phase 14 too. The gas inlets are often semi-tangential Nozzles. To ensure good agitation, the fluidized bed generally has a height to maximum ratio Diameter from about 1: 2 to 5: 1. The dilute phase gas zone contains entrained particles from the bed. The crude product gas is treated in the cyclone 38 after exiting the gasifier 10 via line 36. The planning of cyclone 38 depends on the starting material used, in particular its grain size. The line 40 carries the separated fine particles Return material to the bed as this material may contain recyclable carbon. When the separated finely divided material is returned to the gasifier, it is advantageous to maintain the reaction temperature in order to avoid unnecessary heat loss

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and avoid spending on carbon. The one separated by the cyclone finely divided material can be used in various ways, e.g. as fuel or - in the case of several stages as Charge for another carburetor. The unreacted coal in the product leaving the gasifier shows a heavier gasability under the gasification conditions in the gasifier, so that it is advantageous to combine these materials in one Use a carburetor that is driven under more severe conditions.

In Fig. 1, the bottom of the carburetor 10 is also provided with a device to remove the ashes. The larger and heavier ash particles are fickle and fall out of the fluidized bed out ο These particles are collected and passed through a water-cooled Conveyor screw 41 transported to the centrifugal discharge bunker 42 for removal from the system. To reduce A crusher can be provided to reduce the particle size of the ash to an easily transportable size.

The raw product gas from the gasifier 10 is by indirect heat exchange in the heat exchanger 44 with heat recovery chilled. Fine-grained material that emerges from the Deposits gases, can be withdrawn from the heat exchanger 44 via line 46. The finely divided material can be used in the same way handled like the ashes at the bottom of the gas generator. The cooled gases leave the heat exchanger 44 via line

The heat exchange medium for heat exchanger 44 is steam. Boiler feed water enters the heat exchange through line 50

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27 2S24857

shear 44 and, after preheating, arrives at the steam drum 52 via line 54. The steam drum 52 can be equipped with a radiation boiler (not shown) in the top of the carburetor 20 in communication. The heat from the radiant boiler can be used for the indirect heat exchange with the steam in the steam drum 52 can be used. Saturated steam generated in the heat exchanger 44 was, leaves the steam drum 52 via line 60 and returns to the boiler 44, where it is before its delivery to the Dampfnetζ the system through line 62 is overheated. A part the vapor from line 62 is combined with the oxygen-containing gas from line 65 and is used for introduction into the Carburetor as a diluent for the gas in lines 30, 32 and 34. Another portion of the vapor passes through line 28 to the carburetor. The process can be operated under such conditions that there is sufficient steam for discharge from the gasifier is produced. Under certain conditions, enough sensible heat is available, which is advantageous for preheating of the oxygen-containing gas in the waste heat recovery line or, if desired, also used for accompanying processes can be.

The cooled gases leaving the heat exchanger 44 pass via line 48 through a cyclone 68 and through line 74 to the scrubber 72, the cyclone having a line 70 for removing the separated fine-particle material (namely partially spent coal) is equipped. The mass of partially consumed coal in the product gas used in the heat recovery plant and the cyclone can be separated by a

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Conveyor screw arrive at a coal bunker (not shown). The heat recovery unit and cyclone can together form at least about 50 percent _o -% and disconnect more than 75 wt .-% of the discharged gas with the product solids. In the case of a heating gas system, the coal is transported from the coal bunker to the system boundary; in the case of an ammonia or methanol system, it is transported to the coal charging bunker of the coal-fired boiler. A water scrubber is provided to wash the feed nitrogen before it is blown off.

The scrubber 72 removes particulate matter and condenses steam from the gas. The gas from the cyclone flows through the venturi scrubber 72, where the remaining coal particles are removed to a level of less than 0.035 particles / Nm3. Around Keeping the amount of water used to a minimum will do that Venturi water cooled and after removing the ashes in one Settlement tank recirculated.

Additional water may be required for the ash container. The coal is in the form of a wet sludge from the sedimentation tank removed and pumped to the system boundary.

The invention allows the use of high-performance washers. Suitable scrubbers are spray towers, cyclone-like spray towers, venturi scrubbers (e.g. a type with high efficiency and high pressure loss) and the like. The Ventüri washers or venturi-like Scrubbers are particularly advantageous because a subsequent further separation of particles from the gases is not necessary. Electrical

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If necessary, static separators were installed on the downstream side of the Washer used to remove the entrained particles. The gases leave the scrubber via line 76.

Example I.

The system shown in Fig. 1 is used to gasify a semi-bituminous coal with about 50% carbon, 20% ash, 15% Water and 10% oxygen and an upper net calorific value of 5720 Kcal / Kg are used. The ash has a softening point of 1260 ° C, a melting point of 1427 ° C and a pour point of 1482 ° C. The coal is crushed to a particle size in the range of 0 to 9.5 mm.

The carburetor is about 20 m high, has an inside diameter of about 5 m and is conical at the bottom. The top of the fluidized bed is at a height of about 4 m above the gasifier bottom.

The gasifier, which operates under a pressure of around 9 ata, is fed around 1600 t of coal per day. About 5.9 t / h of steam are fed to the gasifier, of which about 5.0 t / h of steam are introduced below the fluidized bed. About 24,600 Nm3 / h of a mixture of about 5% by volume of steam and 95% by volume of air are passed through line 34, 52,400 Nm3 of a mixture of 2% by volume of steam and 98% by volume of air are passed through line 32 and 41,900 Nm3 of a mixture of 3% by volume steam and 97% by volume air is fed through line 30 to the gasifier. The residence time of the gases in the gasifier is about 20 seconds and the empty pipe speed. is 1.13 m / s. Almost the entire implementation with _ ₃₀ _

609851/0818

the coal and the coal particles discharged from the bed calculated in the carburetor within 14 meters of the ground.

The reaction takes place at 103 8 to 1149 ° C. The carburetor under a pressure of about 9 ata gases leaving contain 19 vol .-% CO, 7 vol .-% C02, 12 vol .-% H2 _f 1.4 vol .-% methane (5% of the contained in the product gas Carbon), 50.3 vol .-% N2 and 10.3 vol .-% steam and have a temperature of about 982 C. The waste ash consists of 78% ash and 22% carbon. The gas flows through the heat exchanger 44 and the cyclone 68, where heat is obtained from it and further finely divided material is removed. When it leaves the heat exchanger, the gas has a temperature of about 149 ° C. and when it leaves the cyclone 68 contains about 141 dust particles per Nm3. It then passes through the Ventüri washer 72, when it leaves the gases have a temperature of about 38 ° C., a pressure of about 8 atm and a dust content of less than 0.035 dust particles per Nm3. The upper calorific value of the gas is about 1130 Kcal / Nm3. The carbon utilization, calculated from the carbon content of the gas divided by the carbon content of the coal, is about 90%. The gasification performance, calculated by the ratio of the upper calorific values of gas to coal, is about 65%. The total expenditure for the product gas compression is 24 590 KW with delivery below 15 ata per 17.9 »10 ⁹ Kcal / d.

Example II and III

Example I is essentially repeated, but using a pressure of 3 or 6 ata. The results achieved

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are given in the table. It is also used for comparison purposes Example I repeated under atmospheric pressure.

Pressure, ata 1 3 6th Product gas compound vol .-%
(dry) C02
CO
H2
CH 4
N2 7.1
22.0
14.0
0.8
56.1 7.4
21, 7
13.5
1.2
56.2 Upper calorific value, Kcal / Nm3 1103 1112 Composition of as a side
product coal,% ash
carbon 78
22nd NJ -J
NJ CO Carbon utilization,% 89 89 89 Gasification efficiency,% 65 65 65 Total compression, plant
Effort, KW _
when submitting less than 15 ata each 17.9 * 10
Kcal / d 91.6 * 1O ³ 66.3 · 1Ο ³ 35, Ο 1Ο ³

The above comparison shows the advantage achieved by the method according to the invention with regard to the total compression effort while maintaining the carbon utilization and the gasification efficiency.

Example IV

The procedure in Example I is essentially repeated,

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however, the gasification at a temperature of 871 ⁰ C and a pressure of 14 ata is performed, and 50 vol .-% is of the introduced below the fluidized bed steam replaced by recycled gas, so that from the gasifier, a gas product having a methane content of 7 vol. -% (25% of the carbon in the product gas) escapes. In this particular example it is not necessary to replace the steam with recycle gas to any significant extent, since according to Example I a small amount of steam was used.

With reference to FIG. 2, a specific example for the production of heating gas according to the invention is given for explanation, however, this does not limit the invention. The gas from the gasification part is with the formation of a fuel gas except for one Desulfurized content of max. 100 ppm total sulfur. This low sulfur content is due to a combination of carbon oxysulfide hydrolysis and hydrogen sulfide removal is achieved. For the removal of hydrogen sulfide is carried out using the alkazide process. The concentrated hydrogen sulfide stream from the regenerator for the alkazide solution is in a Claus plant to elemental sulfur implemented.

In detail, the gas from the gasification part is in the compressor 102 compressed to a pressure of about 5.6 at. Gas compression is only required if the carburetor is under a Pressure is operated which is smaller than the required delivery pressure. The compressors are driven by a steam turbine, part of the drive steam being blown off and the remainder being condensed. The one generated in the waste heat branch of the gasification

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Reaction steam of 84 at and 51O ⁰ C is expanded to the required feed pressure for the gasifier. "The remaining energy is supplied by condensation of the steam of 84 at and 510 ° C at 152 Torr. v / o most of the carbon oxysulphide is reacted with the water contained in the presence of activated aluminum oxide or cobalt / molybdenum catalyst to form hydrogen sulphide and carbon dioxide , for example about 121 to Ml ⁰ C, raised. The exhaust gases from the hydrolysis are further cooled to about 38 ° C. by the air cooler 108 and finally by the water cooler 110. The final cooling to the required for the Alkazid absorber temperature, ie about 21 _o ⁰ C is performed by the cooling system 112. "

In the alkazide container 114, the hydrogen sulfide is selectively absorbed by the alkazide solution, an aqueous solution of the potassium salt of dimethylaminoacetic acid. The Alkazidverfahren selectively absorbs hydrogen sulfide in the presence of carbon dioxide, so that a more concentrated hydrogen sulfide feed frequently about 20 vol .-% hydrogen sulfide to the Claus plant is obtained _o The spent solution from the absorber is by stripping with low-pressure steam in a Kochej - outgasser 118 regenerated at about 104 to 127 ° C under a pressure of about 0 to 0.7 at. The heat exchange in exchanger 116 between the spent and regenerated solutions reduces the amount of low pressure steam required in the digester degasser. The overhead gases from the alkazide absorber contain less

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³⁴ 262485?

less than 100 ppm sulfur and are released as product heating gas to the system boundary.

The gas from the boiler outgasser 118 includes, after removal of a part of the moisture contained, for example, approximately 21 vol .-% hydrogen sulfide and together with the required proportion of oxygen, _o for example about 1 mole of oxygen to 3 moles of hydrogen sulfide to the Claus furnace 120 is supplied so that 2 moles of H2S per 1 mole of SO2 are present in the exhaust gas under flow control and sulfur dioxide recirculation via line 122. The sulfur dioxide can come from a regeneration part of an end gas cleaning system. The gases and oxygen burn together at burners, which promote even mixing and combustion. Most of the sulfur-forming reactions take place in this furnace; Some of the unconverted hydrogen sulfide, sulfur dioxide and also small amounts of carbon oxysulfide and carbon disulfide pass through the furnace and are converted in catalytic converters located on the downstream side. The main reaction is

3 H2S + 3/2 02 = 3 H20 + 3 / x S

The hot furnace gas is generated by medium pressure steam in the smoke tube waste heat boiler 123 cooled ,, Part of the sulfur vapor present condenses and is withdrawn to the sulfur pit 128. Alternatively, further cooling, sulfur condensation and The gas is reheated to increase total sales ο

The flue pipes of the waste heat boiler surround a larger pipe 124, through the hot furnace gas with the aid of the downstream valve 126

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can be performed under temperature control in the by-pass. In this way, the gas leaving the boiler tubes is reheated to a temperature suitable for the sulfur formation reactions in the first converter stage 130, approximately 204 to 232 ° C. _f. There may be other means, for example, _o external by-pass or Wiederaufheizöfen, apply to the creation of a controlled inlet temperature for the first converter stage.

The main reaction in the first and second stages of the catalytic Converter 130 and 132 is

2 H2S + S02 = 2 H20 + 3 / x S _x

The hydrolysis of the carbon oxysulphide and the carbon disulfide is essentially completed in the first converter stage, where the main and hydrolysis reactions cause a temperature increase of about 28 to 111 ° C. The one in the first catalytic Converter stage used catalyst can, for example, bauxite, activated aluminum oxide or cobalt / molybdenum.

The gas from the first converter stage is used in the first sulfur condenser 134 is cooled, and sulfur mist is removed in the first agglomerator 136. The condensed sulfur is

The one diverted to the sulfur pit 128 with the main waste heat boiler 123 connected sulfur condenser generates steam by heat transfer on the shell side; the generated Steam is separated from the circulating water in the common steam drum 138

After the first agglomerator, the gas is heated directly

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reheated in an auxiliary burner 140, in the heating gas or Sour gas conducted in the bypass is burned with a little more than the stoichiometric amount of oxygen, so that the exact inlet temperature for the second converter stage 132, e.g. about 204 to 232 C, is observed. The second converter stage works with the same catalyst as the first converter stage. In a similar way as at the entrance of the first stage, other means of preheating the feed can also be used =

The second sulfur condenser operates at a minimum temperature, ZoB. about 127 to 149 C, so that an effective sulfur condensation is guaranteed and therefore only low-pressure steam is generated, which is given off to the waste heat boiler 123 _o Alternatively, the condensation heat can be used to preheat boiler feed water. The sulfur separated in the second condenser and agglomerator is drained to the sulfur pit 128.

The lower operating temperature at the second converter of about 232 to 260 ° C favors the formation of sulfur to such an extent that about 92% of the sulfur entering the plant as hydrogen sulfide is recovered in the second sulfur condenser 142 and its agglomerator 144 after cooling and defogging the converted gas can. A higher percentage of sulfur application may further by addition of catalytic stages are achieved _o This gas is then passed to the incinerator 146, where it is oxidized for the oxidation of sulfur compounds with air to sulfur dioxide at relatively high temperatures, for example, _o 677 ° C _o The exhaust gas is at a sulfur dioxide extraction

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system released so that the end gas released to the atmosphere corresponds to the air purification regulations.

The exhaust gases from the incinerator 146 are suitably used, for example by generating steam in the waste heat boiler 148 and Passed on to the quench tower 150, cooled. The gas is cooled and water is condensed out, so that the sulfur dioxide absorber 152 a saturated gas at about 49 to 77 C is supplied.

The cooled gas then enters vertically into a two-stage countercurrent absorber 152 where it comes into contact with a sulfite-rich sodium sulfite bisulfite solution at a temperature of, for example, about 49 to 77 ° C. The sulfite in the solution is converted to bisulfite by the absorption of sulfur dioxide. The absorber is designed in such a way that it makes the best possible use of energy, ie has a low pressure drop and low heat requirement and still has a sufficiently low sulfur dioxide content in the exhaust gas _o The bisulfite-rich solution from the absorber is pumped to the regeneration system.

A suitable supply is located in containers 154 and 155 of circulating absorbent solution before and after the regeneration system. This supply allows the absorption system to keep the pogeneration plant in operation if it should be necessary for minor repairs and cleaning to turn off.

The absorption solution, which is rich in bisulfite, is forced to

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Running evaporator 156 supplied, in which sulfur dioxide and water vapor evaporated from the solution to produce a sulphite-rich slurry. The indirect heater 159 is used to increase the temperature of the used absorption solution the way to the evaporator. The mixture of sulfur dioxide and water vapor Downstream of the evaporator is in the first condenser 158 partially condensed. This condensate and the condensate from the second condenser 160 is stripped and steam stripped in a condensate stripper 162 to remove sulfur dioxide then the evaporator as return water for the dissolution of the crystals slurry used. The vapor from the condenser 160, along with the overhead vapor from the stripper, is in the exchanger 164 is cooled and the water vapor is condensed, leaving a highly concentrated (95% by weight) sulfur dioxide product stream accrues, which is compressed and returned via line 22 under about 0.7 at to the Claus plant.

The regenerated absorption solution exiting the evaporator 156 is used to supplement the required sodium ions Sodium hydroxide, sodium carbonate or other suitable sodium salts are added. The resulting sulfite-rich absorbent solution is pumped back into the sulfur dioxide absorber.

Referring to Figure 3 _o the inventive method is explained for the production of methanol without limiting the invention herein is shown. The methanol synthesis takes place at about 100 ata. It has been found that it is more economical to compress the gas emerging from the gasification plant prior to further processing. The cooled, dust-free gas

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from the coal gasification is compressed in several compressor stages 202 to about 105 atm. A is used to drive the compressors Steam turbine, which is operated with steam of 84 at and 510 C, the steam is expanded to 152 torr. The cooling and condensate removal takes place after all compressor stages with the exception of the last one, since the gas for the carbon monoxide conversion is on 2 88 ° C must be preheated.

The purpose of the exothermic conversion stage according to the reaction equation

CO + H20 = C02 + H2

is to adjust the ratio of carbon monoxide to hydrogen to the value required for methanol synthesis, An exit CO content of about 6% by volume in the converted gas is achieved in a single-stage conversion reactor 204, which works at about 288 ° C and about 105 ata. Part of the compressed Gas, e.g. about 50%, is around the conversion reactor led around, cooled in the cooler 206 and mixed with the cooled, converted gas, so that an average CO content of about 20%. The conversion catalyst used is sulfur-resistant and contains, for example, cobalt / molybdenum. The compressed gas for the shift reactor is mixed with the shift steam in a molar ratio of steam to dry gas of 1: 1 and mixed before introduction into the reactor Das preheated to 288 ° C. by heat exchange with the hot exhaust gases from the shifting reactor in exchanger 208 Conversion exhaust gas is passed through a waste heat recovery system after the heat exchanger 210p the steam from boiler feed water

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3.5 at generated, cooled and finally with water in a cooler 212 further cooled to 35 ° C.

The Rectisol process developed by Linde and Lurgi in Germany serves to remove the acidic gases. The Rectisol process absorbs C02 and H2S from the converted synthesis gas stream, wherein methanol in the absorber 214 serves as an absorbent. Carbon dioxide is released into the atmosphere, and one to hydrogen sulfide rich gas is then available for sulfur recovery in the manner indicated above. This receives absorption currents by selective regeneration of the methanol from the absorber in a two-stage regenerator, which is carried out by the units 216 and 218 is designated. The methanol stream to the absorber must be cooled for which purpose the heat exchanger 228 with water and the cooling unit 230 are used. Because of this cooling and also because of the Dilution effect, water must be removed from the converted gas fed to the absorber. This is done by mixing of liquid methanol with the gas in the container 220 and separation of the resulting wet methanol. The wet methanol is dried by distillation in the distillation plant 222 and returned to the separation tank 220. Low pressure nitrogen from the air separation plant is used to strip carbon dioxide from the rich methanol solution in the first regenerator stage 216. The stripped solution of the first regenerator stage is converted into a second regenerator stage 218 by means of a low-pressure steam heated digester expelled the hydrogen sulfide. The stream of carbon dioxide with a trace of hydrogen sulfide is released from the first regenerator blown through line 224. The sulfur water exiting from the second regenerator 218 via line 226

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Material stream flows to a Claus plant for the purpose of sulfur recovery. The cleaned synthesis gas is then ready for the methanol synthesis. The carbon dioxide content of the synthesis gas is regulated in such a way that a desulfurized partial stream with high S02 content from the absorber to the S02 recovery unit - as pointed out with reference to Figure ₀ 2 - via line 232, with the head gas from the absorber 214 to mixes a gas with about 5 to 10 vol. _Q -% S02.

The process uses a synthesis using, for example, a copper-based catalyst developed by ICI, which delivers good methanol yields ^{at low temperatures, for example 210 to 271 ° C.} The high activity of the catalyst at low temperature allows reaction at pressures as low as 52.5 atm, pressures of about 105 atm often being used to improve the economics of the process. As a result of the low working temperature, the formation of by-products is very low, so that high yields of process products result.

The last traces of sulfur are produced from the synthesis gas after it has been preheated to a desulfurization temperature of about 343 C in a steam-heated heat exchanger 234 through a bed of zinc oxide removed in container 236. A bed of a chloride trap, namely the chloride trap Z 125-1 from Chemicals and Catalysts, Inc. is provided in container 238 to prevent chloride poisoning of the synthesis catalyst. After cooling down to about 3 8 C in the heat exchanger 240, the synthesis gas is fed through the circulating fan 2 42 into the circulation system used for synthesis entered. The circulation fan circulates the gases in the synthesis circuit

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run around and is a centrifugal fan with a direct steam turbine drive. The mixture of unreacted gas and fresh boost gas is in the converter exchanger 244 by the hot gases leaving the converter to the reaction temperature preheated. The converter for the methanol synthesis is a pressure vessel 2 46 which is designed for straight passage and contains a single catalyst bed.

The temperature is controlled by blowing in cold feed gas via line 245 through distributors at points of suitable elevation into the catalyst bed. Get the distributors excellent mixing and allow a free flow of catalyst between them, so that a fast catalyst filling and emptying is possible.

When flowing down over the catalyst, the reactants form methanol. The exit gas of the converter is first in the converter heat exchanger 244 and then in the raw methanol condenser 246, in which the raw methanol condenses, cooled to about 38 C. The crude product is in the high pressure separator 2 48 separated, which is essentially an impact separator with a defogger made of stainless steel and a very effective separation. The inert components of the booster gas, methane and nitrogen, are removed from the synthesis cycle repelled between the separator 248 and the location of the boosting gas addition. The repellant gas is eventually used as boiler fuel used.

The crude methanol collected in the separator is converted into

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the expansion vessel 252 relaxes. The resulting product comes under a pressure of about 1.75 to 3.5 ata and one Temperature of about 38 C to the distillation plant 254. To enable independent operation of the synthesis and distillation plant, the raw methanol can be pumped into the raw methanol tank 246.

Flash gas, primarily pre-dissolved gas, exits the flash tank through line 258 and becomes with the reject stream of the synthesis cycle and used as fuel.

The crude methanol is distilled to methanol in a single stage processed by fuel quality. The total yield from the distillation is 99%.

The more volatile components are removed in the top of the column, mainly dimethyl ether, methyl formate, aldehydes, ketones and lower paraffinic hydrocarbons. The column portion below the feed tray is used for water removal _o by steam of 3.5 at its boiling point in the heat exchanger 257 heated feedstock enters the upper part of the column. The overhead vapor, which is rich in volatile components, reaches a first reflux condenser 259; the condensate flows at about 66 to 93 ° C. to the reflux drum 260 _o The uncondensed vapors and the remaining synthesis gas pass for further methanol condensation in the second reflux condenser 262. This condenser arrangement avoids supercooling of the reflux flowing back into the column. the

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uncondensed gases from the second condenser are flared.

Fusel oil (mainly alcohols such as isobutanol) is repelled from a tray near the column bottom. To the losses of organic The fusel oil can then be converted into the methanol product to reduce substances and the heat losses with the waste water flow of fuel quality mixed in again. If chemical grade methanol is the desired product, then fusel oil can be burned as fuel.

The column evaporator is heated by low pressure steam. Since the bottom product is weakly acidic, it will help prevent the Corrosion introduced below the feed tray through line 264 caustic alkali.

The methanol product is withdrawn from the top of the column via line 266, cooled and pumped to the storage container at 45 ° C. and 7 atm.

A methanol plant with a capacity of 5000 tpd from coal requires a large amount of oxygen for coal gasification. It it is therefore economical to integrate an oxygen generation system into the factory. It can be a normal cryogenic air separation system with a production of 1600 tpd oxygen per strand can be used. The one in this plant as a by-product Accumulated nitrogen is used for purging and stripping the methanol in the Rectisol system. With the air separation system you can

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the air and oxygen compressors are equipped with turbine drives be, v / obei working with non-condensing and condensing drive steam. The one needed for coal gasification Reaction steam is available from the non-condensing turbine drive steam, which is heated from 84 at and 510 C to the for the carburetor is relieved of the required pressure.

The method according to the invention for producing ammonia is explained as an example with reference to FIG. 4, without this being seen as a limitation of the invention. Ammonia synthesis takes place at high pressure. It has proven to be more economical to compress the raw gas of the gasification part before further processing. The cooled dust-free gas from coal gasification is at a multistage compressor 302 to drive steam turbines, the steam 84 and has 51O ⁰ C and is depressurized to 152 Torr, at compressed to about 88.5. Cooling and condensate removal take place after each compression stage with the exception of the last one, where the escaping gas is preheated to around 288 ° C for carbon monoxide conversion. The purpose of the conversion stage is to maximize the hydrogen yield according to the exothermic conversion

CO + H20 = C02 + H2

An exit CO content of around 1.3% by volume in the conversion plant is permitted because this concentration has a nominal CO concentration of 2.0% by volume when fed to the nitrogen scrubbing column results. This carbon monoxide concentration is achieved by a two-stage conversion on a sulfur-resistant conversion catalyst, e.g. cobalt / molybdenum. That

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combined gas for the first stage of the shift reactor 306 is mixed with the shift steam so that about gives a molar ratio of steam to dry gas of 1: 1, and preheated to 228 C in the heat exchanger 304 by heat exchange with the hot exhaust gases from the first reactor stage.

The gas from the first stage contains about 6.5% by volume of carbon monoxide. The gas from the heat exchanger is cooled to 288 ° C. in the heat exchanger 308 by generating steam from 17.5 at. Steam is added again so that a molar ratio is obtained before entering the second stage of the shifting reactor 310 from steam to gas of about 1: 1. The hot gas from the second reactor stage is generated by medium pressure and Low pressure steam, preheating of boiler feed water, preheating from high pressure make-up boiler feed water, through an air cooler and finally through a water-cooled end cooler (all summarized referred to as heat exchanger 312) cooled to 35 ° C. The cooled gas flows to the plant for removal acidic gas components.

The Rectisol process is used to remove the acidic gases ο This method is carried out essentially in the same way as was described with reference to FIG. 3 and generally referred to as unit 314.

The nitrogen scrubbing is used to remove residual methane and carbon monoxide and to create a stoichiometric ratio of hydrogen to nitrogen _o The hydrogen-rich gas reaches a temperature of about -45.5 to -59.5 and

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a pressure of about 73.5 ata to nitrogen scrub column 316 where it is mixed with the nitrogen from an air separation plant. The nitrogen scrubbing consists of this single scrubbing column and heat exchangers. By releasing some of the high pressure nitrogen into tail gas expander / heat exchanger 318, a sufficient amount of pressure is achieved Cooling achieved to liquefy some of the remaining high pressure nitrogen. By giving up this liquid nitrogen At the top of the scrubbing column, the remaining impurities, e.g. carbon monoxide and methane, are removed from the hydrogen-rich Gas washed out. The liquid nitrogen leaving the column 316 is passed through line 345 into the end gas expander 318. The hydrogen / nitrogen mixture emerging from the nitrogen scrubbing column is heated in the heat exchanger 320 and passed through Addition of further high-pressure nitrogen from the air separation system to the stoichiometric composition of the ammonia synthesis gas set.

The synthesis gas stream for the ammonia synthesis is before entry finally compressed into the ammonia cycle in the compressor 322 to about 238 to 245 ATA. The exhaust gas, the methane, carbon monoxide and nitrogen can be burned as an additional fuel in a boiler outside the plant. The compressed Gas is then cooled to about 49 to 66 ° C in the syngas compressor aftercooler 324. The cooled addition gas is with mixed with the partially cooled exhaust gas from the ammonia converter. The mixed gases are then in the first and second coolers 326 or 328 cooled by ammonia cooling and condensed. The ammonia is in the ammonia impingement separator 330 from the loading

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the feed stream for the converter is separated. The liquid ammonia is expanded in two stages in order to reduce the content of dissolved gas to a permissible concentration. The gases out the first expansion tank are returned to the suction side of the synthesis gas compressor 322. The gases released in the second expansion tank 324 are transferred to the fuel system of FIG Plant repelled. The product ammonia from this container is fed with a cooling stream from the sour gas removal in the heat exchanger 336 cooled to -33 C and delivered to the system limit for storage. By using the cooling stream The synthesis gas production eliminates the need for a vacuum stage on the ammonia cooling system and product pumps.

The gases from the ammonia impingement separator are exchanged through heat with the converter flue gases in the converter feed heat exchanger 338 heated before they are fed to the ammonia converter 342 by the circulation fan 340. The ones in the converter Incoming gases have a temperature of about 16 to 38 ° C and a pressure of about 252 to 259 ata.

The gases from the ammonia converter are in a number of exchangers cooled before they are mixed with the make-up synthesis gas. This cooling line consists of a feed water preheater, an air-cooled radiator, a water-cooled radiator, commonly referred to as heat exchanger 344, and the converter feed heat exchanger mentioned above.

The ammonia cooling system is designed for overpressure, whereby the lowest pressure is 1.05 at and on the low pressure side of the

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there is a cooling compressor driven by a steam turbine. This compressor works with divided pressure, with the middle Inlet pressure is 2.45 at. The system consists of the refrigeration compressor, the refrigeration condenser, the refrigerant tank, the first and second coolers and the high pressure suction drum. The use of a medium pressure level results in a considerable saving result in compressive energy. Theoretically, an increasing number of medium pressure levels would result in further energy savings lead, however, this often turns out to be uneconomical

The ammonia plant with a capacity of 1200 tpd requires large amounts of oxygen for coal gasification. It is therefore economical to integrate an oxygen generation system into the factory. A normal low-temperature oxygen separation system with a capacity of 1000 tpd oxygen can be used. The low-pressure nitrogen that occurs as a by-product in this system can be used for flushing when stripping the methanol in the Rectisol system and for nitrogen washing. * The high-pressure nitrogen is used for ammonia synthesis. In the air separation system, the air and oxygen compressors are driven by a turbine, using non-condensing and condensing steam. The reaction steam required for the coal gasification plant can be obtained at the outlet of the turbine operated with non-condensing steam, this steam being expanded from 84 at and 51O ⁰ C to the pressure required for the gasifier.

7 <: r? IM < _: 'jc-n <: / changes and equivalents of the present invention

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Application are familiar to the person skilled in the art and fall within the scope of the present invention.

In summary, the invention relates to a process for continuous Gasification of carbonaceous material using a fluidizing medium and an oxygen-containing gas under controlled feed rates, specific addition conditions and selective process conditions, so that a Carbon monoxide and hydrogen-rich product is created »If desired a product with an increased methane content can be generated. The gasification takes place under pressure in a fluidized bed with formation of a gaseous reaction product and carbonaceous solids as by-products. There can be additional proportions of oxygen containing gas are selectively introduced with steam. The product flows at a certain superficial velocity and with a certain residence time through a dilute phase kept at a certain temperature. The presence of undesirable heavier hydrocarbons as by-products is excluded. When withdrawing from the bottom of the bed is the spent coal brought into contact with steam or inert gas in order to recover the sensible heat. The cooled product gas has under certain conditions less than about 141 grain particles per Nm3. Partly consumed Charcoal is removed from the product for delivery or for certain purposes. »The product is cooled and through a Heat recovery zone directed to recover the heat from the at least a portion is used to generate steam, a portion of which is used in the process. The cooled product gas is passed through a heavy duty scrubber with high pressure drop to remove fine particles of partially burnt coal

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609851/0818

to remove and a product gas with small amounts of solids, to provide a carbon monoxide content of at least about 10 vol .-%, hydrogen and a desired calorific value. The pressure in the carburetor is maintained by a back pressure control at one point in the gas system on the downstream side of the carburetor .

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609851/0818

Claims (1)

Patent claims Process __ for the continuous gasification of finely divided, carbonaceous material under selective conditions in an environmentally acceptable manner with the formation of an Carbon monoxide and hydrogen rich gas product using a pressurized gasifier with a lower, dense fluidized bed of the material and one at the upper limit of the bed adjoining upper, dilute gas zone containing entrained particles, characterized in that man the material under a pressure slightly above the carburetor pressure at a temperature in the range of ambient temperature to 538 C in such an amount into the gasifier that the upper limit of the fluidized bed in a given Height of about 1.22 to 6.10 m above the lower limit of the fluidized bed is maintained, the ratio of the heights the diluted gas zone and the fluidized bed in the area is from about 3: 1 to 10: 1, - 53 - · 609851/0818 an oxygen-containing gas with up to about 50 volume percent steam with a mean total temperature of up to about 538 ° C under a pressure slightly above the carburetor pressure at spatially separated, essentially over the circumference evenly distributed points at different heights in such quantities into the carburetor that the components of the fluidized bed substantially uniformly in contact with one another under controlled selective reaction conditions come and be gassed, at least about 50% by weight of the steam introduced into the fluidized bed at the lower limit of the fluidized bed spatially separate, substantially evenly distributed points with a gas temperature of up to about 649 ° C and a pressure slightly above the carburetor pressure in such an amount as to stir up the lower part of the bed will, the material in the fluidized bed at a maximum gasifier temperature in the range of about 816 to 1316 ° C and an overall temperature in the dense phase below the softening temperature of any ash contained in the material Formation of a gaseous reaction product and partially consumed coal solids gasified, the gaseous Reaction product contains carbon monoxide, hydrogen, carbon dioxide, methane and diluent and is diluted in the Phase crosses, - 54 - 609851/0818 additional proportions of the oxygen-containing gas with up to about 10% by volume of steam at or just above the boundary between the fluidized bed and the dilute phase in space separate, substantially evenly distributed over the circumference places in such quantities that they with the the carbon components leaving the fluidized bed react, increasing the temperature of the dilute phase and increasing the carbon turnover Improve the performance of the process, resulting in a crude product gas that is at least about 50% of the contains oxidized carbon in the form of carbon monoxide, the gaseous reaction product with a considerably higher superficial velocity than the point of the beginning whirling up and up to about 6.1 m / s with a residence time in the dilute phase of about 2 to 50 seconds can flow through the dilute phase, with further gasification to a crude product gas occurs and the diluted Phase at a maximum possible temperature consistent with the properties of any ash contained is held the crude product gas is generated under selective conditions so that the formation of undesirable heavy hydrocarbons remains limited to a minimum as by-products, withdraws the crude product gas from the upper dilute zone, up to about 60 wt .-% of the partially consumed coal from - 55 - 609851/0818 The bottom of the fluidized bed is withdrawn and for the purpose of recovering sensible heat and steam preheating with at the lower phase boundary brings into contact steam introduced into the fluidized bed, the raw product gas in a heat recovery zone Temperatures of about 93 to 260 ° C cools and substantial amounts of partially used coal for the purpose of removal the process or recirculation or work-up under other conditions from the crude product gas up to a content removed from less than about 141 solid particles per Nm3, so that a cooled product gas is approximately under gasification pressure and occurs at temperatures more suitable for further processing, uses the recovered heat to generate steam, part of which is used in the process, that in the heat recovery zone under the prevailing, Pressures below the gasifier pressures cooled product gas through a high performance scrubber with high pressure drop conducts, thereby removing fine, partially used coal particles and a product gas with a content of less as about 3.53 solid particles per Nm3 gas, at least about 10% by volume carbon monoxide, at least about 10% by volume Hydrogen and with a calorific value of at least about 800 Kcal / Nm3 and - 56 - 609851/0818 the carburetor pressure by back pressure regulation on the gas system at a point located downstream of the carburetor Overpressure, preferably pressures above about 1.5 ata holds. 2c Process according to Claim 1, characterized in that the gasifier pressure is kept in the range from about 2 to 20 ata, preferably 6 to 14 ata. 3. The method according to claim 1 or 2, characterized in that the maximum temperature in the carburetor at about 927 to 12O5 ° C, the crude product gas about 55 to 85% of the contains oxidized carbon in the form of carbon monoxide and the scrubber is a venturi scrubber which is a product gas with less than about 0.53 pesticide particles per Nm3 gas. 4. The method according to any one of claims 1 to 3, characterized in that that the ratio of height to maximum diameter of the fluidized bed is in the range of about 1: 2 to 5: 1. 5. The method according to any one of claims 1 to 4, characterized in that that the oxygen-containing gas is air, oxygen-enriched air or oxygen. 6. The method according to any one of claims 1 to 5, characterized in that that the cooled product gas has less than 3.5 solid particles per Nm3 gas as the starting material for the production of heating gas is used. -57 - 6098 5 1/0818 7. The method according to any one of claims 1 to 6, characterized in that that the oxygen-containing gas is air or oxygen-enriched air and one is the cooled product gas with a content of less than 0.35 solid particles per Nm3 gas as the starting material for production of heating gas with a low calorific value is used. 8. The method according to any one of claims 1 to 6, characterized in that that the oxygen-containing gas is oxygen or oxygen-enriched air and the cooled one Product gas with a content of less than 0.35 solid particles per Nm3 gas as the starting material for production of a heating gas with a medium calorific value is used. 9. The method according to any one of claims 1 to 6, characterized in that that one the carbonaceous material at or below the upper limit of the fluidized bed in the gasifier and the cooled product gas with less than 0.35 solid particles per Nm3 gas as the starting material for production of methanol begins. 10. The method according to any one of claims 1 to 6, characterized in, that one the carbonaceous material at or below the upper limit of the fluidized bed in the gasifier introduces and the cooled product gas with a content of less than 3.5, preferably less than 0.35 solid particles uses gas as a raw material for the production of ammonia per Nm3. - 58 - 609851/0818 11. A method for producing heating gas, characterized in that that the cooled product gas according to one of claims 1 to 8 with less than 3.5 solid particles per Nm3 Gas and a content of carbon oxysulphide and hydrogen sulphide introduces into a desulfurization zone, there in one first phase carbon oxysulphide in the presence of a catalyst which hydrolyzes carbon oxysulphide with the formation of hydrogen sulphide hydrolyzed and from the hydrolysis product gas containing increased amounts of hydrogen sulfide in one second phase absorbs hydrogen sulfide with the formation of a desulfurized heating gas. 12. The method according to claim 11, characterized in that one the hydrolysis is carried out under a pressure of more than 4.2 ata. 13. The method according to claim 11 or 12, characterized in that that the hydrolysis at a temperature of about 93 to 204 C and the hydrogen sulfide absorption at a temperature from 21 to 38 C and a pressure of more than about 4.2 ata. 14. A method for the production of methanol, characterized in that that the cooled product gas obtained according to one of claims 1 to 5 or 9 with less than 0.35 solid particles introduces gas into a conversion zone per Nm3, which Gas with steam in the presence of a sulfur-resistant shift catalyst at a temperature of about -59 - 609851/0818 260 to 482 ° C and a pressure of more than 14 ata to a gas with about 20% carbon monoxide, the gas desulphurized, the carbon oxides and hydrogen in the desulphurized and converted gas on a methanol synthesis catalyst at temperatures in the range from 210 to 271 ⁰ C converts to methanol and the methanol wins. 15. A method for the production of ammonia, characterized in that that the cooled product gas obtained according to one of claims 1 to 5 or 10 with less than 0.35 solid particles introduces gas into a conversion zone per Nm3, the gas with water vapor in the presence of a sulfur-resistant shift catalyst at a temperature from about 260 to 482 ° C and a pressure of more than 14 ata converted to a gas with less than about 3 vol .-% carbon monoxide, desulfurized the gas, converted the desulfurized Gas for removing carbon monoxide and methane with the formation of a gas with the stoichiometric H2 / N2 ratio with liquid nitrogen washes the hydrogen and nitrogen under ammonia synthesis conditions at a Temperature of about 315 to 538 ° C under a pressure of more than 140 ata converts to ammonia and the ammonia wins. 16. The method according to any one of claims 1 to 15, characterized in that that the solid carbonaceous material used in the gasification is coal. 17. The method according to any one of claims 1 to 8, characterized - 6O- 609851/0818 draws that for the production of a product gas with a higher methane content for methane formation favorable conditions preferably applies the carbonaceous material to the gasifier above the upper limit of the fluidized bed introduces. 18. The method according to claim 17, characterized in that one operates at temperatures of around 815 to 927 ° C. 19. The method according to claim 17 or 18, characterized in that that one works at a pressure of at least about 10 ata and reduces the amount of steam used rather than by recycle gas replaced. 609851/0818 Blank page