EP0062363B1 - Process for the simultaneous production of fuel gas and thermal energy from carbonaceous materials - Google Patents

Description

The invention relates to a process for the simultaneous generation of fuel gas and process heat from carbon-containing materials by gasification in a first fluidized bed and subsequent combustion of the combustible constituents remaining in the gasification in a second fluidized bed, the gasification being carried out at a pressure of at most 5 bar and one Temperature of 800 to 1100 ° C by means of oxygen-containing gases in the presence of water vapor and 40 to 80 wt .-% of the carbon contained in the starting material are reacted, and then the residue from the gasification together with the by-products from gas cleaning are fed to a further fluidized bed becomes.

Energy is required in various forms in the manufacture of industrial products. High-quality primary energy sources such as gas and oil are often used to generate them. Their increasing scarcity and growing political uncertainty in the supply increasingly force them to substitute these fuels with solid fuels. This necessity requires the development of new technologies that can be used to convert solid fuels in such a way that they can replace traditional energy sources in the context of existing processes. The environmental pollution associated with the use of solid fuels must be reliably avoided. This is particularly because the shortage of primary energy is increasingly forcing the use of high-ash and high-sulfur coal.

Depending on the type of process step involved, industry needs energy in various forms when producing a specific product, e.g. as steam for heating purposes, in the form of other high-temperature heat and in the form of clean fuel gases, the combustion of which does not adversely affect product quality.

In principle, it is possible to use the various forms of energy, e.g. To produce fuel gas and steam, each separately, but this requires an investment and operating costs, which is not justifiable in the context of conventional industrial plant sizes. In addition, the operation of energy conversion systems that work independently of one another is associated with increased losses and increased expenditure for environmental protection.

In order to avoid the disadvantages associated with the separate production of different forms of energy, a process for the simultaneous generation of fuel gas and steam has already been presented, in which coal of practically any nature is gasified in a fluidized bed and the gasification residue is burned to produce steam (Processing, November 1980, page 23).

Although a step in the promising direction has been taken with this process, it is disadvantageous that its throughput is low in relation to the specified reactor dimensions and that because of the process conditions chosen, in particular for the gasification stage, the flexibility with regard to the production of fuel gas and steam is low. This method also does not solve the problems associated with the necessary fuel gas cleaning, in particular the problem of desulfurization and elimination of the annoying by-products that arise during the fuel gas cleaning.

DE A 27 29 764 relates to a process for the gasification of carbon-containing material by means of oxygen-containing gases and water vapor, in which the gasification residue is then burned and the combustion gas is used as an additional gasification agent and heat transfer medium in the gasification reactor. Both gasification and combustion take place in the "classic fluidized bed", ie in a fluidized state which is completely different compared to the "circulating fluidized beds" used in the application. The process envisages entering the by-products from mechanical gas cleaning (dust) and gas cooling (water) into the combustion stage. There is no detailed information on the desulfurization of the gases produced.

The main drawbacks for this method are the disadvantages already mentioned above.

US Pat. No. 4,026,679 deals with the production of fuel gas by two-stage gasification of carbon-containing material using two expanded fluidized beds connected in a crosswise manner. The desulfurization of the gas produced takes place for the most part in the gasification reactor itself. A combustion and thus generation of process heat is not provided. The object of the invention is to provide a method for the simultaneous generation of fuel gas and process heat from carbon-containing materials which does not have the known, in particular the aforementioned disadvantages, high flexibility in converting the energy content of the starting material into fuel gas on the one hand and process heat on the other hand owns and thus enables a short-term adjustment to the respective energy form requirement.

The object is achieved by designing the method of the type mentioned at the outset in accordance with the invention in such a way that both the gasification and the combustion take place in a separate, circulating fluidized bed and the two gas streams obtained are cleaned, cooled and dedusted separately, the in the gasification stage generated fuel gas at a temperature in the range of 800 to 1000 ° C i. Whirl state is freed of sulfur compounds with the aid of CaS-forming materials and the combustion of the remaining combustible constituents takes place at an air ratio of λ≈ 1.05 to 1.40.

The method according to the invention can be used for all carbon-containing materials which can be gasified and burned independently. It is suitable for all types of coal, but is particularly attractive for coal of inferior quality, such as coal washing mountains, mud coal, coal with a high salt content. However, lignite and oil shale can also be used.

The principle of the circulating fluidized bed used in the gasification and combustion stages It is characterized in that, in contrast to the "classic" fluidized bed, in which a dense phase is separated from the gas space above by a clear density jump, there are distribution states without a defined boundary layer. A leap in density between the dense phase and the dust space above it does not exist; however, the solids concentration within the reactor decreases continuously from bottom to top.

mit

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wobei

ist.When defining the operating conditions using the key figures from Froude and Archimedes, the following areas result:

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It means:

In contrast, the desulfurization of the gas produced can take place in any vortex state, e.g. in a Venturi fluidized bed with solids discharge in a downstream separator. However, a circulating fluidized bed can also advantageously be used for desulfurization.

A particularly advantageous embodiment of the invention consists in converting 40 to 60% by weight of the carbon contained in the starting material into the gasification. In this way, a fuel gas with a particularly high calorific value can be generated. In addition, it is possible to dispense with the use of otherwise significantly higher amounts of water vapor, which in the subsequent process steps are again produced as gas water which is undesirable per se.

If the carbonaceous material does not already have the amount of water vapor required for gasification itself in the form of moisture, it is necessary to add water vapor for the gasification reaction. Water vapor and the required oxygen-containing gas should be entered at different levels. An expedient embodiment of the invention consists in that in the gasification stage water vapor, predominantly in the form of fluidizing gas, and oxygen-containing gas, predominantly in the form of secondary gas, are supplied. This procedure does not rule out that the entry of minor amounts of water vapor can also take place together with the oxygen-containing secondary gas and the entry of minor amounts of oxygen-containing gases together with water vapor as the fluidizing gas.

Furthermore, it is advantageous to set the residence time of the gases above the entry point of the carbon-containing material to 1 to 5 seconds in the gasification stage. This condition is usually realized by entering the carbonaceous material at a higher level in the gasification stage. On the one hand, this creates a gas that is richer in smoldering products and has a correspondingly higher calorific value, and on the other hand it ensures that the gas has practically no hydrocarbons with more than 6 carbon atoms.

The gas can be desulfurized using the usual desulfurization agents. A preferred embodiment consists of desulfurizing the gases emerging from the gasification stage in a circulating fluidized bed by means of lime or dolomite or the corresponding fired products with a particle size dp 50 of 30 to 200 tim, and for this purpose an average suspension density of 0.1 to 10 kg / m in the fluidized bed reactor ³ , preferably 1 to 5 kg / m ^3; and to set an hourly solids circulation rate which is at least 5 times the solids weight in the reactor shaft. This procedure is characterized in that the desulfurization can be carried out at high Oas throughputs and at a very constant temperature. The high temperature stability has a positive effect on the desulfurization in that the desulfurizing agent retains its activity and thus its absorption capacity against sulfur. The high degree of granularity of the desulfurization agent complements this advantage, since the ratio of surface area to volume is particularly favorable for the binding rate of the sulfur, which is essentially determined by the rate of diffusion.

betragen. Dabei ist zu berücksichtigen, daß bei Verwendung von Dolomit oder gebranntem Dolomit praktisch nur die Kalziumkomponente mit den Schwefelverbindungen reagiert.The desulphurization agent dosage should be at least 1.2 to 2.0 times the stoichiometric requirement

be. It should be noted that when using dolomite or burnt dolomite, practically only the calcium component reacts with the sulfur compounds.

The desulfurizing agent is most advantageously introduced into the fluidized bed reactor via one or more lances, e.g. by pneumatic blowing.

Particularly favorable operating conditions are achieved if the gas speed during desulfurization is set to 4 to 8 m / sec (calculated as empty pipe speed).

In particular if the exhaust gases from the gasification stage exit at high temperatures, a preferred embodiment of the invention consists in adding all of the desulfurization agent also required for the combustion stage to the gas desulfurization stage. In this way, the thermal energy required for heating and possibly for deacidification is withdrawn from the gas and thus preserved in the combustion stage.

The combustion of the combustible constituents not converted in the gasification stage takes place in a further circulating fluidized bed, at the same time also eliminating the by-products obtained in gas cleaning in an environmentally friendly manner. The loaded desulphurization agents coming from the gas purification stage, in particular insofar as they are in sulfidic form, such as calcium sulfide, are sulfated and thereby converted into landfill-compatible compounds, such as calcium sulfate. In addition, the heat of reaction released in the sulfation process is also obtained as process heat, and the other by-products, such as dust from gas dedusting and gas water, are also removed.

The term process heat is a heat transfer medium, the energy content of which can be used in various ways to carry out processes. It can be gas for heating or, if it is an oxygen-containing gas, for the operation of combustion devices of various types. The generation of saturated steam or superheated steam is also particularly advantageous for heating, for example of reactors or for driving electrical generators, or for heating heat transfer salts, for example for heating tubular reactors or autoclaves.

In a preferred embodiment of the invention, the combustion is in two stages with different levels supplied oxygen-containing gases performed. Their advantage lies in "soft" combustion, in which local overheating phenomena are avoided and NO _o formation is largely suppressed. In the case of two-stage combustion, the upper supply point for oxygen-containing gas should be so far above the lower one that the oxygen content of the gas supplied at the lower part has already been largely consumed.

If steam is desired as process heat, an advantageous embodiment of the invention consists in creating an average suspension density of 15 to 100 kg / m3 above the upper gas supply by adjusting the amounts of fluidization and secondary gas and at least a substantial part of the heat of combustion by means of above the upper gas supply within the dissipate cooling surfaces in the free reactor space.

Such a procedure is described in DE-AS 25 39 546 or in the corresponding US Pat. No. 4,165,717.

The gas velocities prevailing in the fluidized bed reactor above the secondary gas supply are generally above 5 m / s at normal pressure and can be up to 15 m / s and the ratio of diameter to height of the fluidized bed reactor should be chosen such that gas residence times of 0.5 to 8. 0 s, preferably 1 to 4 s, are obtained.

• 1. Als Fluidisierungsgas Inertgas zu verwenden. Dann ist es unerläßlich, das sauerstoffhaltige Verbrennungsgas als Sekundärgas in mindestens zwei übereinanderliegenden Ebenen einzutragen.
• 2. Als Fluidisierungsgas bereits sauerstoffhaltiges Gas zu verwenden. Dann genügt der Eintrag von Sekundärgas in einer Ebene. Selbstverständlich kann auch bei dieser Aus-führungsform noch eine Aufteilung des Sekundärgaseintrags in mehrere Ebenen erfolgen.

Any fluid which does not impair the nature of the exhaust gas can be used as the fluidizing gas. Inert gases such as recirculated flue gas (exhaust gas), nitrogen and water vapor are suitable, for example. With a view to intensifying the combustion process, however, it is advantageous to use oxygen-containing gas as the fluidizing gas. The following options are therefore available:

• 1. Use inert gas as the fluidizing gas. Then it is essential to enter the oxygen-containing combustion gas as a secondary gas in at least two superimposed levels.
• 2. To use oxygen-containing gas as the fluidizing gas. Then the entry of secondary gas in one level is sufficient. Of course, the secondary gas input can also be divided into several levels in this embodiment.

A plurality of supply openings for secondary gas are advantageous within each entry level.

The advantage of this procedure is in particular that a change in the production of process heat is possible in the simplest way by changing the suspension density in the furnace space of the fluidized bed reactor located above the secondary gas supply.

A certain heat transfer is associated with a prevailing operating state under predetermined fluidizing gas and secondary gas volumes and the resultant specific average bus pension density. The heat transfer to the cooling surfaces can be increased by increasing the suspension density by increasing the amount of fluidizing gas and possibly also the amount of secondary gas. With the increased heat transfer at practically constant combustion temperature, it is possible to dissipate the amounts of heat generated with increased combustion output. The increased oxygen requirement required due to the higher combustion output is here virtually automatically present due to the higher fluidization gas and possibly secondary gas quantities used to increase the suspension density.

Similarly, to adapt to a reduced process heat requirement, the combustion output can be regulated by reducing the suspension density in the furnace space of the fluidized bed reactor located above the secondary gas line. By lowering the suspension density, the heat transfer is also reduced, so that less heat is removed from the fluidized bed reactor. The combustion performance can be reduced essentially without a change in temperature.

The entry of the carbonaceous material is also most conveniently via one or more lances, e.g. by pneumatic blowing.

Another expedient, more universally applicable design of the combustion process consists in creating an average suspension density of 10 to 40 kg / m ³ above the upper gas supply by adjusting the amounts of fluidization and secondary gas, removing hot solids from the circulating fluidized bed and in the fluidized state by direct and indirect heat exchange cool and return at least a partial flow of cooled solid into the circulating fluidized bed.

This embodiment is explained in DE-OS 26 24 302 or in the corresponding US-PS 4 111 158.

In this embodiment of the invention, the temperature constancy can be achieved practically without changing the operating conditions prevailing in the fluidized bed reactor, that is to say without changing the suspension density, among other things, solely by controlled recycling of the cooled solid. Depending on the combustion performance and the set combustion temperature, the recirculation rate is more or less high. The combustion temperatures can range from very low temperatures, which are close above the ignition limit, to very high temperatures

Set temperatures as required, which are limited by softening the combustion residues. They can be between 450 ° C and 950 ° C.

Since the heat generated during the combustion of the combustible constituent is predominantly removed in the fluidized bed cooler connected downstream on the solids side, and a heat transfer to the cooling register located in the fluidized bed reactor, which has a sufficiently high suspension density as a prerequisite, is of secondary importance, which results in a further advantage this method that the suspension density in the area of the fluidized bed reactor above the secondary gas supply can be kept low and consequently the pressure loss in the entire fluidized bed reactor is comparatively low. Instead, the heat is extracted in the fluidized bed cooler under conditions that allow extremely high heat transfer, for example in the range of 400 to 500 watts / m ² . ° C.

The combustion temperature in the fluidized bed reactor is controlled by recycling at least a partial stream of cooled solid from the fluidized bed cooler. For example, the required partial flow of cooled solid can be fed directly into the fluidized bed reactor. In addition, the exhaust gas can also be cooled by introducing cooled solid matter, which is fed, for example, to a pneumatic conveyor line or a floating exchanger stage, the solid matter which is later separated off from the exhaust gas then being returned to the fluidized bed cooler. As a result, the exhaust gas heat ultimately ends up in the fluidized bed cooler. It is particularly advantageous to enter cooled solid as a partial stream directly and as another indirectly after cooling the exhaust gases in the fluidized bed reactor.

In this embodiment of the invention, too, the gas residence times, gas velocities above the secondary gas line at normal pressure and type of fluidization or secondary gas supply are in agreement with the same parameters of the previously discussed embodiment.

The recooling of the hot solid of the fluidized bed reactor should take place in a fluidized bed cooler with several cooling chambers flowing through one after the other, into which interconnected cooling registers are immersed, in countercurrent to the coolant. This enables the heat of combustion to be bound to a comparatively small amount of coolant.

The universality of the last-mentioned embodiment is particularly given by the fact that almost any heat transfer media can be heated in the fluidized bed cooler. Of particular importance from a technical point of view is the generation of steam in various forms and the heating of heat transfer salt.

The flexibility of the method according to the invention can be further increased if, in a further advantageous embodiment of the invention, the combustion stage is additionally fed with carbon-containing materials. This embodiment has the advantage that the production of process heat can be increased as desired in the combustion stage without influencing the combustion gas generation in the gasification stage.

In the process according to the invention, air or oxygen-enriched air or technically pure oxygen can be used as the oxygen-containing gases. In the gasification stage in particular, the use of an oxygen-rich gas is recommended. Finally, an increase in performance can be achieved within the combustion stage by carrying out the combustion under pressure, up to about 20 bar.

The fluidized bed reactors used in carrying out the method according to the invention can be of rectangular, square or circular cross section. The lower region of the fluidized bed reactor can also be conical, which is particularly advantageous in the case of large reactor cross sections and thus high gas throughputs.

The invention will be explained in more detail with reference to the figure, which represents a flow diagram of the method according to the invention, and the exemplary embodiments.

Carbon-containing material is added to the circulating fluidized bed formed from the fluidized bed reactor 1, the cyclone separator 2 and the return line 3 via line 4 and gasified there by adding oxygen via secondary gas line 5 and water vapor via fluidizing gas line 6. The gas generated is dedusted in a second cyclone separator 7 and introduced into a Venturi reactor 8, which is supplied with desulfurizing agent via line 9. The desulfurization agent is introduced together with the gas into a waste heat boiler 10, separated there and discharged via line 11. The gas enters a scrubber 12, in which it is freed of residual dust. The washing liquid is pumped through line I3, a filter device 14 and a further line 15. Finally, the gas arrives in a condenser 16 for water separation and is then discharged via line 44 after passing through a wet electrostatic precipitator 17.

The gasification residue is taken from the circulating fluidized bed 1, 2, 3 via line 18, via a cooler 19 and line 20 of the second circulating fluidized bed used for combustion and formed from a fluidized bed reactor 21, cyclone separator 22 and return line 23. Oxygen-containing gas is supplied via lines 24 and 25 as fluidizing gas and as secondary gas. A separate addition of fuel is possible via line 26 and of desulfurizing agent via line 27. Together with the gasification residue via line 20, desulphurization agents, sludge and gas water are also introduced, which are introduced via lines 11, 42 and 43, respectively. The gas emerging from the separator 22 of the fluidized bed reactor 21 is freed of dust in a further cyclone separator 29 and cooled in a waste heat boiler 30. Further ash is extracted from the exhaust gas in the separator 31. The exhaust gas is finally discharged via line 32.

A partial flow of solid circulated via fluidized bed reactor 21, separating cyclone 22 and return line 23 is withdrawn from return line 23 by means of line 33 and cooled in fluidized bed cooler 34. In addition, in the fluidized bed cooler 34, the dust which is deposited in the separating cyclone 29 and in the waste heat boiler 30 is fed via lines 35, 36 and 37, respectively. A heat transfer salt is used as the coolant, which is passed in countercurrent through the fluidized bed cooler 34 by means of cooling registers 38. The oxygen-containing fluidizing gas which is supplied to the fluidized bed cooler 34 via line 41 and heated there passes via line 39 as secondary gas into the fluidized bed reactor 21 Solid is fed to the fluidized bed reactor 21 via line 40 to absorb the heat of combustion.

example 1 A coal came into use

• 20% by weight of ash and
• 8% by weight moisture.

Its calorific value was 25.1 MJ / kg (mega joules)

3300kg of the aforementioned coal was fed to the fluidized bed reactor 1 via line 4 every hour. At the same time, 913 Nm ^{3 of} oxygen-containing gas with 95% by volume _{02 were introduced} via line 5 and 280 kg of steam of 400 ° C via line 6. Due to the selected operating conditions, a temperature of 1020 ° C. and an average suspension density (measured above line 5) of 200 kg / m ³ reactor volume were established in the fluidized bed reactor. The gas of 1020 ° C largely freed of solids in the cyclone separator 2 was further dedusted in the cyclone separator 7 and introduced into a Venturi fluidized bed 9, which also received an addition of 238 kg / h of lime (CaC0 ₃ content 95% by weight). The desulfurized gas together with the loaded desulfurizing agent emerged at a temperature of 920 ° C. and was introduced into the waste heat boiler 10. 155 kg / h of loaded desulfurizing agent were obtained in the waste heat boiler 10, and saturated steam of 45 bar was also produced in an amount of 1.75 t / h. The dedusted and cooled gas then reached the scrubber 12, in which it was cleaned with washing liquid pumped over line 13, filter device 14 and line 15. It was then transferred to the condenser 16 by being cooled to 35 ° C by indirect cooling. After passing through a wet electrostatic precipitator 17, 3940 Nm ³ / h of fuel gas were removed via line 44. The calorific value of the fuel gas generated was 10.6 MJ / Nm ³ .

The gasification circulating fluidized bed of gasification residue was removed via line 18 and fed to the fluidized bed reactor 21 via line 20 together with the loaded desulphurizing agent discharged via line 11 and the filter residue discharged via line 43. The total feed rate was 1869 kg / h. The fluidized bed reactor 21 was also supplied with 34 3400 Nm ^{3 of} air via the fluidizing gas line 24 and 25 4900 Nm ³ / h of air via the secondary gas line. Another secondary gas supply in the form of air heated in the fluidized bed cooler 34 was carried out via line 39 in an amount of 1900 Nm ³ / h. The latter air flow was at a temperature of 500 ° C. In the fluidized bed reactor, the combustion temperature was 850 ° C and above the top secondary gas line an average suspension density of 30 kg / m ³ . The exhaust gas from the fluidized bed reactor was freed from the solids discharged in the downstream recycle cyclone 22, dusted in the downstream cyclone separator 29 and finally introduced into the waste heat boiler 30. In the waste heat boiler 30, the temperature of the exhaust gases was reduced from 850 ° C. to 140 ° C. 3.6 t / h of superheated steam of 45 bar and 480 ° C. were generated. The gas was then introduced into the separator 31 and freed from further ash there. Finally, it was fed to the chimney at a temperature of 140 ° C. via line 32. In the separator 30, 660 kg / h of ash and an additional 247 kg / h of sulfated desulfurizing agent were obtained. The ash quantity of 660 kg / h corresponds to the total ash production in the combustion stage.

Of the solid circulated in the circulating fluidized bed 21, 22, 23, 45 t / h of solid were introduced into the fluidized bed cooler 34 via line 33 and there in countercurrent to a heat transfer salt which was at 350 ° C. in an amount of 185 t / h was fed, cooled. The heat transfer salt heated up to 420 ° C. The ashes cooled in the cooler 34 to 400 ° C. were returned to the fluidized bed reactor 21 via line 40 to absorb the heat of combustion. The fluidized bed cooler 34, which has four separate cooling chambers, was in turn fluidized with 1900 Nm ³ / h of air, which heated up to a mixing temperature of 500 ° C. As already mentioned above, it was fed via line 39 to the fluidized bed reactor 21 as a secondary gas. In the above example, the usable / made energy is divided as follows:

Example 2 A coal was used again

• 20 Gew.-% Ascheanteil und
• 8 Gew.-% Feuchte,

deren Heizwert 25,1 MJ/kg betrug. 3300 kg der vorstehend genannten Kohle wurde stündlich dem Wirbelschichtreaktor 1 über Leitung 4 aufgegeben. Gleichzeitig wurden 776Nm³ sauerstoffhaltiges Gas mit 95 Vol.-^0,'o 0₂ über Leitung 5 und 132 kg Dampf von 400° G über Leitung 6 eingetragen. Aufgrund der gewählten Betriebsbedingungen stellte sich im Wirbelschichtreaktor 1 eine Temperatur von 1000° C und eine mittlere Suspensionsdichte (oberhalb der Leitung 5 gemessen) von 200 kg/m³ Reaktorvolumen ein. Das im Zyklonabscheider 2 vom Feststoff weitgehend befreite Gas von 1000° C wurde im Zyklonabscheider 7 weiter entstaubt und in eine Venturi-Wirbelschicht 9 eingetragen, die außer-dem einen Zusatz von 236 kg/h Kalk (CaC0₃-Gehalt 95 Gew.-%) erhielt. Das entschwefelte Gas trat zusammen mit dem bela-denen Entschwefelungsmittel mit einer Temperatur von 900° C aus und wurde in den Abhitzekessel 10 eingetragen. Im Abhitzekessel 10 wurden 155 kg/h beladenes Entschwefelungsmittel erhalten, außerdem Sattdampf von 45 bar in einer Menge von 1,52 t/h erzeugt. Das entstaubte und abgekühlte Gas gelangte dann in den Wäscher 12, in dem es mit über Leitung 13, Filtereinrichtung 14 und Leitung 15 umgepumpter Waschflüssigkeit gereinigt wurde. Es wurde dann in den Kondensator 16 überführt, indem es durch indirekte Kühlung auf5° C abgekühlt wurde. Nach Durchgang durch ein Naß-Elektrofilter 17 wurden über Leitung 44 3400Nm³ /h Brenngas abge-MJ/Nm³.

• 20% by weight of ash and
• 8% by weight moisture,

whose calorific value was 25.1 MJ / kg. 3300 kg of the above-mentioned coal was fed to the fluidized bed reactor 1 via line 4 every hour. At the same time, 776Nm ^{3 of} oxygen-containing gas with 95 vol. ^{0, 0} or 0 _{2 were introduced} via line 5 and 132 kg of steam of 400 ° G via line 6. Due to the selected operating conditions, a temperature of 1000 ° C. and an average suspension density (measured above line 5) of 200 kg / m ³ reactor volume were established in the fluidized bed reactor 1. The gas of 1000 ° C. largely freed of solids in the cyclone separator 2 was further dedusted in the cyclone separator 7 and introduced into a Venturi fluidized bed 9, which also added 236 kg / h of lime (CaC0 ₃ content 95% by weight ) received. The desulfurized gas, together with the loaded desulfurization agent, emerged at a temperature of 900 ° C. and was introduced into the waste heat boiler 10. 155 kg / h of loaded desulphurising agent were obtained in the waste heat boiler 10, and saturated steam of 45 bar was also produced in an amount of 1.52 t / h. The dedusted and cooled gas then reached the scrubber 12, in which it was cleaned with washing liquid pumped over line 13, filter device 14 and line 15. It was then transferred to condenser 16 by cooling to 5 ° C by indirect cooling. After passing through a wet electrostatic precipitator 17, 3400 Nm ³ / h of fuel gas were discharged via line 44-MJ / Nm ³ .

The gasification circulating fluidized bed of gasification residue was removed via line 18 and fed to the fluidized bed reactor 21 via line 20 together with the loaded desulphurizing agent discharged via line 11 and the filter residue discharged via line 43. The total feed rate was 2068 kg / h. The fluidized bed reactor 21 was further supplied with air via the fluidizing gas line 24 3075Nm ³ / h air and secondary gas line 25 7325Nm ³ / h. Another secondary gas supply in the form of air heated in the fluidized bed cooler 34 was carried out via line 39 in an amount of 1900 Nm ³ / h. The latter air flow was at a temperature of 500 ° C. In the fluidized bed reactor, the combustion temperature was 850 ° C and above the uppermost secondary gas line an average suspension density of 30 kg / m ³ . The exhaust gas from the fluidized bed reactor was freed from the solids discharged in the downstream recycle cyclone 22, dusted in the downstream cyclone separator 29 and finally introduced into the waste heat boiler 30. In the waste heat boiler 30, the temperature of the exhaust gases was reduced from 850 ° C. to 140 ° C. 4.4 t / h of superheated steam of 45 bar and 480 ° C. were generated. The gas was then introduced into the separator 31 and freed from further ash there. Finally, it was fed to the chimney at a temperature of 140 ° C. via line 32. In the separator 30, 660 kg / h of ash and an additional 247 kg / h of sulfated desulfurizing agent were obtained. The ash quantity of 660 kg / h corresponds to the total ash production in the combustion stage.

Of the solid circulating in the circulating fluidized bed 21, 22, 23, 54 t / h of solid were introduced into the fluidized bed cooler 34 via line 33 and there in countercurrent to a heat transfer salt. which was fed at 350 ° C in an amount of 223 t / h, cooled.

The heat transfer salt heated up to 420 ° C. The ashes cooled in the cooler 34 to 400 ° C. were returned to the fluidized bed reactor 21 via line 40 to absorb the heat of combustion. The fluidized bed cooler 34, which has four separate cooling chambers, was in turn fluidized with 1900 Nm ³ / h of air, which heated up to a mixing temperature of 500 ° C. As already mentioned above, it was fed via line 39 to the fluidized bed reactor 21 as secondary gas. The energy parts which were used according to this example were divided as follows:

Example 3

Example 2 was varied insofar as the energy generation in the combustion stage was increased by additional coal combustion without any change within the gasification stage.

For this purpose, an additional 500 kg / h of coal (of the type mentioned at the outset) and 35 kg / h of limestone (95% by weight CaC0 ₃ ) were added via line 26 in the fluidized bed reactor 21. The amount of fluidizing air to be supplied through line 24 had been increased to 4100 Nm ³ / h and the amount of secondary air to be supplied through line 25 had been increased to 10 300 Nm ³ / h. As a result of the modified procedure compared to Example 2, 30 5.7 t / h of steam of 45 bar and 480 ° C. were generated in the waste heat boiler and 34 302 t / h of heat transfer salt from 350 to 420 ° C. were heated in the cooler. For this purpose, the one led over the fluidized bed cooler 34 Increase the amount of solids to 73 t / h. 760 kg / h of ash and 284 kg / h of sulfated desulfurizing agent were obtained. Based on the total amount of coal added, the harnessed energy was divided as follows:

Claims (11)

1. A process of sinultaneously producing fuelgas and process heat from carbonaceous materials by agasification in a first fluidized bed and a subsequent conbustion in a second fluidized bed of the combustible constituents left after the gasification, wherein the gasifi-cation is carried out at a pressure of up to 5 bars and atemperature of 800 to 1100⁰ C by a treatment with oxygencontaining gases in the presence of steam and 40 to 80% of the carbon contained in the starting material are thus re-acted and the gasification residue together with the byproducts which have becone available in the purification ofthe gas is fed to another fluidized bed characterized in that the gasification and combuation are effected in respective separate circulating fluidized beds, both gas streams obtained are separately purified, cooled and freed from dust, the fuel gas produced in the gasification stage is freed from sulfur compounds in a turbulent state by means of CaS-forming materials at a temperature in the range from 800 to 1000° C, and the combustion of the remaining combustible constituents is effected with an air ratio number of k = 1.05 to 1.40.

2. A process according to claim 1, characterized in that 40 to 60 % by weight of the carbon contained in the starting material are reacted in the gasifying stage.

3. A process according to claims 1 and 2, charactarized in that the gasifying stage (1, 2, 3) is fad with steam mainly in the form of fluidizing gas (6) and with oxygen-containing gas mainly in the form of secondary gas (5).

4. A procass according to claims 1, and 3, charactarized in that a residance time of 1 to 5 seconds of the gas is maintained in the gasifying stage (1, 2, 3) above the inlet (4) for the carbonaceous material.

5. A process according to any of claims 1 to 4, charactarized in that the gases leaving the gasifying stage (1, 2, 3) are desulfurized in a circulating fluidized bed by a treatment with lime or dolomite or the corresponding calcined products having a particle diameter of dp50 - 30 to 200 um and for this purpose the fluidized bed reactor is operated to maintain therein a suspension having a mean solids density of 0.1 to 10 kg/m³, preferably 1 to 5 kg/m³, and to circulate solids at such a rate that the weight of the solids circulated through the circulating fluidized bed per hour is at least 5 times the weight of the solids contained in the reactor shaft.

6. A process according to any of claims 1 to 5, characterized in that a gas velocity of 4 to 8 meters per second (calculated as empty-pipe valocity) is maintained during the desulfurization.

7. A process according to any of claims 1 to 6, charactarized in that all desulfurizing agent, including that required for the combustion stage, is fed to the gas-dasulfurizing stage.

8. A process according to any of claims 1 to 7, charactarizad in that the combustion is effected in two stages with the aid of oxygen-containing gases fed at diffarant lavels.

9. A process according to claim 8, characterized in that the rates of fluidizing and secondary gases are controlled to maintain a suspension having a mean solids dansity of 15 to 100 kg/m³ above the upper gas inlet and at least a substantial part of the heat genarated by the combustion is dissipated through cooling surfaces provided within the free space of the reactor above the upper gas inlet.

10. A process according to claim 8, charactarized in that the rates of fluidizing gas (24) and secondary gas (25) are controlled to maintain above the upper gas inlet (25) a mean solids density of the suspension of 10 to 40 kg/m³ hot solids are withdrawn from the circulating fluidized bed (21, 22, 23) and are cooled by direct and indirect heat exchange in a turbulent state (34), and at least one partial stream of cooled solids is recycled (40) to the circulating fluidized bed (21, 22, 23).

11. A process according to any of claims 1 to 10, characterized in that additional carbonaceous materials are fed to the combustion stage.

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