Abstract:
A method and device for the gasification of pulverized fuels from solid fuels such as bituminous coals, lignite coals, and their cokes, petroleum cokes, coke from peat or biomass, in entrained flow, with an oxidizing medium containing free oxygen, by partial oxidation at pressures between atmospheric pressure and 80 bar, and at temperatures between 1,200 and 1,900° C., at high reactor capacities between 1,000 and 1,500 MW. The method uses the following steps: metering of the fuel, gasification reaction in a gasification reactor with cooled reaction chamber contour, quench-cooling, crude gas scrubbing, and partial condensation.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The invention relates to a method for entrained flow gasification with very high capacity that can be used for supplying large-scale syntheses with synthesis gas. The invention enables the conversion of fuels refined into pulverized fuel, such as lignite and bituminous coals, petroleum coke, solid grindable refuse, and solid-liquid suspensions, so-called slurries, into synthesis gas. The fuel is reacted at temperatures between 1,200 and 1,900° C. with a gasification medium containing free oxygen, at pressures up to 80 bar, by partial oxidation to gases containing CO and H 2 . This is done in a gasification reactor that is distinguished by a multiple-burner system and by a cooled gasification chamber.  
         [0003]     2. The Prior Art  
         [0004]     The autothermic entrained flow gasification of solid, liquid, and gaseous fuels has been known in the technology of gas production for years. The ratio of fuel to gasification medium containing oxygen is chosen so that higher carbon compounds are completely cracked for reasons of synthesis gas quality into synthesis gas components such as CO and H 2 , and the inorganic components are discharged as molten slag; see J. Carl, P. Fritz, NOELL-KONVERSIONSVERFAHREN, EF-Verlag für Energie- und Umwelttechnik GmbH, 1996, p. 33 and p. 73.  
         [0005]     According to various systems used in industry, gasification gas and molten slag can be discharged separately or together from the reaction chamber of the gasification device, as shown in German Patent No. DE 197 131 A1. Either systems with refractory linings or cooled systems are used for the internal confinement of the reaction chamber structure of the gasification system; see German Patent No. DE 4446 803 A1.  
         [0006]     European Patent No. EP 0677 567 B1 and International Publication No. WO 96/17904 show a method in which the gasification chamber is confined by a refractory lining. This has the drawback that the refractory masonry is loosened by the liquid slag formed during gasification, which leads to rapid wear and high repair costs. This wear process increases with increasing ash content. Thus, such gasification systems have a limited service life before replacing the lining. Also, the gasification temperature and the ash content of the fuel are limited; see C. Higman and M. van der Burgt, “Gasification”, Verlag ELSEVIER, USA, 2003. A quenching or cooling system is also described, with which the hot gasification gas and the liquid slag are carried off together through a conduit that begins at the bottom of the reaction chamber, and are fed into a water bath. This joint discharge of gasification gas and slag can lead to plugging of the conduit and thus to limitation of availability.  
         [0007]     German Patent No. DE 3534015 A1 shows a method in which the gasification media, powdered fuel and oxidizing medium containing oxygen, are introduced into the reaction chamber symmetrically through multiple burners in such a way that the flames are mutually diverted. The gasification gas loaded with powdered dust flows upward and the slag flows downward into a slag-cooling system. As a rule, there is a device above the gasification chamber for indirect cooling utilizing the waste heat. However, because of entrained liquid slag particles, there is the danger of deposition and coating of heat exchanger surfaces, which hinders heat transfer and may lead to plugging of the pipe system and/or erosion. The danger of plugging is counteracted by taking away the hot crude gas with a circulated cooling gas.  
         [0008]     Ch. Higmann and M. van der Burgt in “Gasification”, page 124, Verlag Elsevier 2003, describe a method in which the hot gasification gas leaves the gasifier together with the liquid slag and directly enters a waste heat boiler positioned perpendicularly below it, in which the crude gas and the slag are cooled with utilization of the waste heat to produce steam. The slag is collected in a water bath, while the cooled crude gas leaves the waste heat boiler from the side. A series of drawbacks detract from the advantage of waste heat recovery by this system. Deposits form on the heat exchanger tubes, which lead to hindrance of heat transfer and to corrosion and erosion, and thus to lack of availability.  
         [0009]     Chinese Patent No. CN 200 4200 200 7.1 describes a “Solid Pulverized Fuel Gasifier”, in which the powdered coal is fed in pneumatically and gasification gas and liquefied slag are introduced into a water bath through a central pipe for further cooling. This central discharge in the central pipe is susceptible to plugging that interferes with the overall operation, and reduces the availability of the entire system.  
         [0010]     The capacity of the various gasification technologies mentioned is limited to about 500 MW, which is attributable in particular to the fuel infeed to the gasification reactor.  
       SUMMARY OF THE INVENTION  
       [0011]     It is therefore an object of this invention to provide a gasification method that permits maximum capacities of 1,000 to 1,500 MW with reliable and safe operation.  
         [0012]     This object is achieved by a gasification method for the gasification of solid fuels containing ash at very high capacities with an oxidizing medium containing oxygen based on an entrained flow reactor whose reaction chamber contour is confined by a cooling system, with the pressure in the cooling system always being kept higher than the pressure in the reaction chamber. The process for preparing the fuel and feeding it to the gasification burners is as follows: with dry pneumatic infeed by the dense-flow transport principle, the fuel is dried, pulverized to a grain size of &lt;200 μm, and passed through operational bunkers to pressurized sluices, in which the dust-like fuel is brought to the desired gasification pressure by introducing a non-condensing gas such as N 2  or CO 2 . Different fuels can be used here at the same time. Via a system of multiple such pressurized sluices, they can be loaded and pressurized alternately. The dust under pressure then is sent to metering tanks, in the bottom of which a very dense fluidized bed is produced by likewise introducing a non-condensing gas, with one or more transport pipes immersed in the bed and opening into the burners of the gasification reactor. A separate infeed and metering system is associated with each high-capacity burner. The fluidized fuel dust flows to the burners by applying a pressure differential between the metering tanks and the burners of the gasification reactor. The amount of flowing fuel dust is measured, regulated, and monitored by measurement devices and monitors.  
         [0013]     With the reactor according to the invention, there is still also the ability to pulverize the undried fuel to a grain size of &lt;200 μm and to mix the pulverized fuel with water or oil and to feed it as a slurry to the burners of the gasification reactor. The method of infeed, which is not described at this point, is configured by one skilled in the art according to known methods.  
         [0014]     An oxidizing medium containing free oxygen is supplied to the burners at the same time, and the slurry is converted to crude synthesis gas by partial oxidation. The gasification takes place at temperatures between 1,200 and 1,900° C. and at pressures up to 80 bar. The reactor has a cooled reaction chamber contour that is made up of a cooling shield. This consists of a tubular shield welded gas-tight that is studded and lined with a material that is a good heat conductor.  
         [0015]     The crude gas produced in the gasification reactor leaves the gasification reactor together with the liquid slag formed from the fuel ash and is sent to a chamber located perpendicularly below it, in which the hot crude gas and the liquid slag are cooled by injecting water. The gas can be cooled completely down to the condensation point of the gas by spraying in excess water. The temperature is then between 180 and 240° C., depending on the pressure. However, it is also possible to feed in only a limited amount of cooling water and to cool the crude gas and slag by partial cooling to 700 to 1,100° C., for example, and then to utilize the sensible heat of the crude gas to produce steam in a waste heat boiler. Partial quenching or partial cooling prevents or sharply reduces the risk of slag caking on the tubes of the waste heat boiler. The water or recycled gas condensate needed for complete or partial cooling is supplied through nozzles that are located directly on the jacket of the cooling chamber. The cooled slag is collected in a water bath and is discharged from the process. The crude gas cooled to temperatures between 200 and 300° C. is then sent to a crude gas scrubber, which is preferably a Venturi scrubber.  
         [0016]     The entrained dust is thereby removed down to a particle size of about 20 μm. This degree of purity is still inadequate for carrying out subsequent catalytic processes, for example crude gas conversion. Salt mists are also entrained in the crude gas, which have detached from the powdered fuel during gasification and are carried off with the crude gas. To remove both the fine dust &lt;20 μm and the salt mists, the scrubbed crude gas is fed to a condensation step in which the crude gas is chilled indirectly by 5 to 10° C. Water is thereby condensed from the crude gas saturated with steam, which takes up the described fine dust and salt particles. The condensed water containing the dust and salt particles is separated from the crude gas in a following separator. The crude gas purified in this way can then be fed directly, for example, to a desulfurization system. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]     Other objects and features of the present invention will become apparent from the following detailed description considered in connection with the accompanying drawings. It is to be understood, however, that the drawings are designed as an illustration only and not as a definition of the limits of the invention.  
         [0018]     In the drawings, wherein similar reference characters denote similar elements throughout the several views:  
         [0019]      FIG. 1  shows a block diagram of the technology according to the invention;  
         [0020]      FIG. 2  shows a metering system for pulverized fuel according to the invention;  
         [0021]      FIG. 3  shows a device for feeding pulverized fuel for high-capacity generators;  
         [0022]      FIG. 4  shows a gasification reactor with full quenching; and  
         [0023]      FIG. 5  shows a gasification reactor with partial quenching. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0024]      FIG. 1  shows a block diagram of the process steps of pneumatic metering of pulverized fuel, gasification in a gasification reactor with cooled reaction chamber structure  2 , quench-cooling  3 , crude gas scrubbing  4 , in which there can be a waste heat boiler  4 . 1  between the quench-cooling  3  and the crude gas scrubbing  4 , and a condensation or partial condensation  5  follows the crude gas scrubber  4 .  
         [0025]      FIG. 2  shows a metering system for pulverized fuel consisting of a bunker  1 . 1  followed by two pressurized sluices  1 . 2 , into which lead lines  1 . 6  for inert gas, and at the top of which depressurization lines  1 . 7  exit, with lines to the metering tank  1 . 3  leaving the pressurized sluices  1 . 2  from the bottom. There are fittings on the pressurized sluices  1 . 2  for monitoring and regulating. A line  1 . 5  for fluidizing gas leads into the metering tank from below, which provides for fluidizing the gas, and the fluidized pulverized fuel is fed through the transport line  1 . 4  to a gasification reactor  2 .  
         [0026]      FIG. 3  shows another design of the device for feeding pulverized fuel for high-capacity generators  2 , wherein a bunker  1 . 1  has three discharges for pulverized fuel, each leading to pressurized sluices  1 . 2 , with each of the three pressurized sluices transporting pulverized fuel streams to one of three metering tanks  1 . 3 , from which transport lines  1 . 3  lead to the dust burners  1 . 2  with oxygen infeed of the reactor. There are three dust burners  2 . 1  on each reactor  2  with oxygen feed, with an ignition and pilot burner  2 . 2  to start the reaction. Because of such intensive fluidized fuel flows and the presence of three burners  2 . 1 , it is possible to achieve maximum capacities of 1,000 to 1,500 megawatts with reliable and safe operation.  
         [0027]      FIG. 4  shows a gasification reactor  2  with full quenching  3 , with the ignition and pilot burner  2 . 2  and the dust burners  2 . 1 , through which the fluidizing gas or a slurry of fuel and liquid is fed into the reactor, being positioned in the center of the head of the reactor  2 . The reactor has a gasification chamber  2 . 3  with a cooling shield  2 . 4  whose outlet opening  2 . 5  leads to the quench-cooler  3 , whose quenching chamber  3 . 1  has quenching nozzles  3 . 2 ,  3 . 3 , and a crude gas discharge  3 . 4 , through which the finished crude gas can leave the quench-cooler  3 . The slag that leaves the quench-cooler through an outlet opening  3 . 6  is cooled in the water bath  3 . 5 .  
         [0028]      FIG. 5  shows a gasification reactor  2  with partial quenching, with the gasification reactor located in the upper part, in which dust burners  2 . 1  gasify the dust from the transport line  1 . 4 , and with an ignition and pilot burner  2 . 2  positioned in the center. Gasification reactor  2  has a bottom opening into quenching chamber  3 . 1 , into both sides of which lead quenching nozzles  3 . 2 , with waste heat boilers  4 . 1  placed below this.  
         [0029]     The function will be described with a first example with reference to material flows and procedural processes:  
         [0030]     240 Mg/h of pulverized coal is fed to a gasification reactor with a gross capacity of 1500 MW. This pulverized fuel prepared by drying and grinding crude bituminous coal has a moisture content of 5.8%, an ash content of 13 wt. %, and a calorific value of 24,700 kJ/kg. The gasification takes place at 1,550° C., and the amount of oxygen needed is 208,000 m 3  I. H./h. The crude coal is first fed to a state-of-the-art drying and grinding system in which the water content is reduced to 1.8 wt. %. The grain size range of the pulverized fuel produced from the crude coal is between 0 and 200 μm. The ground pulverized fuel ( FIG. 1 ) is then fed to the metering system, the functional principle of which is shown in  FIG. 2 . The metering system consists of three identical units, as shown in  FIG. 3 , with each unit supplying ⅓ of the total amount of powder, or 80 Mg/h, each to a dust burner. The three dust burners assigned to them are at the head of the gasification reactor, whose principle is shown in  FIG. 4 . The usable pulverized fuel according to  FIG. 2 , which shows one unit of the powder metering system, goes from the operational bunker  1 . 1  to alternately operated pressurized sluices  1 . 2 . There are 3 pressurized sluices in each unit. Pressurized suspension to the gasification pressure is performed with an inert gas such as nitrogen, for example, which is fed in through the line  1 . 6 . After suspension, the pressurized pulverized fuel is fed to the metering tank  1 . 3 . The pressurized sluices  1 . 2  are depressurized through the line  1 . 7  and can be refilled with pulverized fuel. The 3 mentioned pressurized sluices in each unit are loaded alternately, emptied into the metering tank, and depressurized. This process then begins anew. A dense fluidized bed is produced in the bottom of the metering tank  1 . 3  by feeding in a dry inert gas through the line  1 . 5 , likewise nitrogen, for example, that serves as the transport gas; 3 dust-transport lines  1 . 4  are immersed in the fluidized bed. The amount of pulverized fuel flowing in the transport lines  1 . 4  is measured and regulated in relation to the gasification oxygen. The transport density is 250-420 kg/m 3 .  
         [0031]     The gasification reactor  2  is shown and further explained in  FIG. 3 . The pulverized fuel flowing through the transport lines  1 . 4  to the gasification reactor  2  is discharged into 3 metering systems, each with a capacity of 80 Mg/h. The total of 9 transport lines  1 . 4  lead in groups of three each to 3 gasification burners  4 . 1  located at the head of reactor  2 . At the same time, ⅓ of the total amount of oxygen of 208,000 m 3 NTP/h is fed to each gasification burner. The dust burners are arranged symmetrically at angles of 120°, and in the center there is an ignition and pilot burner that heats the gasification reactor  2  and serves to ignite the dust burner  4 . 1 . The gasification reaction, or the partial oxidation at temperatures of 1,550° C., takes place in the gasification chamber  2 . 3 , which is distinguished by a cooled reaction chamber contour  2 . 4 . The monitored and measured amount of pulverized fuel is subjected to ratio regulation with the supplied oxygen, which provides that the ratio of oxygen to fuel neither exceeds nor falls below a range of λ=0.35 to 0.65. The value of λ represents the ratio of the needed amount of oxygen for the desired partial oxidation to the amount of oxygen that would be necessary for complete combustion of the fuel used. The amount of crude gas formed is 463,000 m 3 NTP/h and is distinguished by the following analysis:  
                                                           H 2     19.8   vol. %           CO   70.3   vol. %           CO 2     5.8   vol. %           N 2     3.8   vol. %           NH 3     0.03   vol. %           HCN   0.003   vol. %           COS   0.04   vol. %           H 2 S   0.4   vol. %                      
 
         [0032]     The hot crude gas at 1,550° C. leaves the gasification chamber  2 . 3  together with the liquid slag through the discharge  2 . 5  and is cooled to 212° C. in the quenching chamber  3 . 1  by injecting water through the rows of nozzles  3 . 2  and  3 . 3 , and is then sent through the outlet  3 . 4  to the crude gas scrubber  4 , which serves as a water scrubber to remove dust. The cooled slag is collected in a water bath  3 . 5  and is discharged downward. The crude gas washed with water after the water scrubber  4  is sent for partial condensation  5  to remove fine dust &lt;20 μm in size and salt mists not separated in the water scrubber  4 . For this purpose, the crude gas is cooled by about 5° C., with the salt particles dissolving in the condensed water droplets. The purified crude gas saturated with steam can then be fed directly to a catalytic crude gas converter or to other treatment stages.  
         [0033]     According to Example 2, the process of pulverized fuel feed is to occur according to  FIG. 2  and  FIG. 3 , and the actual gasification in the same way as in Example 1. The hot crude gas and the hot liquid slag likewise pass through discharge  2 . 5  into a quenching chamber  3 . 1 , in which the crude gas is cooled to temperatures of 700-1,100° C., not with excess water, but only by spraying in a limited amount of water through nozzle rings  3 . 2 , and are then sent to the waste heat boiler  4 . 1  to utilize the heat of the crude gas to produce steam ( FIG. 5 ). The temperature of the partially cooled crude gas is chosen so that the slag particles entrained by it are cooled in such a way as to prevent deposition on the heat exchanger tubes. As in Example 1, the crude gas cooled to about 200° C. is then fed to the water scrubber and partial condensation.  
         [0034]     Accordingly, while only a few embodiments of the present invention have been shown and described, it is obvious that many changes and modifications may be made thereunto without departing from the spirit and scope of the invention.  
       LIST OF REFERENCE SYMBOLS USED  
       [0000]      1 . Pneumatic metering systems for pulverized fuel  
         [0000]      1 . 1  Bunker  
         [0000]      1 . 2  Pressurized sluice  
         [0000]      1 . 3  Metering tank  
         [0000]      1 . 4  Transport line  
         [0000]      1 . 5  Line for fluidizing gas.  
         [0000]      1 . 6  Line for inert gas into  1 . 2   
         [0000]      1 . 7  Depressurization line from  1 . 2   
         [0000]      2 . Gasification reactor with cooled reaction chamber structure  
         [0000]      2 . 1  Dust burner with oxygen infeed  
         [0000]      2 . 2  Ignition and pilot burner  
         [0000]      2 . 3  Gasification chamber  
         [0000]      2 . 4  Cooling shield  
         [0000]      2 . 5  Discharge opening  
         [0000]      3  Quenching cooler  
         [0000]      3 . 1  Quenching chamber  
         [0000]      3 . 2  Quenching nozzles  
         [0000]      3 . 3  Quenching nozzles  
         [0000]      3 . 4  Crude gas outlet  
         [0000]      3 . 5  Water bath with slag  
         [0000]      3 . 6  Bottom discharge from  3   
         [0000]      3 . 7  Lining  
         [0000]      4  Crude gas scrubber  
         [0000]      4 . 1  Waste heat boiler  
         [0000]      5  Condensation, partial condensation