Abstract:
A method and an apparatus for gasifying combustible dusts in an entrained flow gasifier with several gasification burners. Each gasification burner is associated with one or a plurality of lock hopper and dosing systems having a plurality of supply flows. This has the advantage that the burners will continue to operate in the event of a failure of one supply flow.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     One embodiment of 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. A gasifier for use in this method is disclosed in U.S. patent application Ser. No. 11/359,608, the disclosure of which is herein incorporated by reference. The invention allows for conversion of combustibles processed into pulverized combustible dusts such as hard coal and lignite, petroleum coke, solid grindable residues but also solid-liquid suspensions, called slurries into synthesis gas. The combustible is thereby converted through partial oxidation into CO— and H.sub.2-containing gases at temperatures ranging from 1,200 to 1,900.degree. C. using a gasification agent containing free oxygen at pressures of up to 80 bar. This occurs in a gasification reactor having a multiple burner array and by a cooled gasification chamber. 
     2. The Prior Art 
     In a gas production technique, the autothermal entrained flow gasification of solid, liquid and gaseous combustibles has been known for many years. For reasons of synthesis gas quality, the ratio of combustible to oxygen-containing gasification agents is chosen such that higher carbon compounds are completely cleaved into synthesis gas components such as CO and H.sub.2 and that the inorganic constituents are discharged in the form of a molten slag. 
     According to different systems well known in the art, gasifying gas and molten slag can be discharged separately or together from the reaction chamber of the gasification apparatus, as this is shown in German Patent No. DE 197 18 131 A1. Systems provided with a refractory lining or cooled systems are known for bounding the reaction chamber structure of the gasification system from inside. 
     SUMMARY OF THE INVENTION 
     One embodiment of the invention can provide a gasification method that achieves the highest outputs of 500 to 1,500 MW while ensuring reliable and secure operation. 
     In high-performance entrained flow reactors, it is necessary to arrange a plurality of gasification burners if one wants to achieve secure conversion of the combustible. In order to ensure start up and secure operation of such reactors, a central ignition and pilot burner is disposed that is surrounded by 3 dust burners symmetrically spaced 120.degree. apart from each other. In order to allow introducing the large amounts of combustible dust of for example 100-400 t/h into the gasification reactor operated under pressure, a plurality of lock hopper and dosing systems are arranged for supplying dust to the gasification burners. It is also possible to associate a lock hopper and dosing system with each gasification burner. Another possibility is to connect each lock hopper and dosing system to a plurality of gasification burners in order to increase their availability. 
     One embodiment of invention provides a method in which one single lock hopper and dosing system is associated with each gasification burner. For this purpose, supply lines lead from each lock hopper and dosing system to a respective one of the gasification burners. Each of the burners may have three feed ports for these supply lines. 
     Further, supply lines may lead from each lock hopper and dosing system to the feed ports in the various gasification burners. The supply lines of three lock hopper and dosing systems may thus lead to different gasification burners so that three gasification burners each having three feed ports may be provided. Each feed port is supplied with combustible from another lock hopper and dosing system. There may be fewer lock hopper and dosing systems than gasification burners. Two lock hopper and dosing systems may, for example, supply combustible to three gasification burners through lines. The combustible dust of each lock hopper and dosing system is distributed evenly to the gasification burners through the respective supply lines. Providing a plurality of lock hopper and dosing systems offers the advantage that the burners will continue to operate steadily upon failure of one of them. 
     In case each gasification burner is supplied through at least two supply lines, one supply line is led from each lock hopper and dosing system to each burner so that redundancy is provided in the event of a system failure. 
     One embodiment of the invention has the advantage that all the gasification burners are supplied uniformly with combustible dust. In this manner, it is possible to mix combustible dusts from diverse lock hopper and dosing systems of the large plants in the gasification burner. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       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. 
       In the drawings, wherein similar reference characters denote similar elements throughout the several views: 
         FIG. 1  shows an example in which each gasification burner is associated with one lock hopper and dosing system; 
         FIG. 2  shows an example in which three gasification burners are associated with three lock hoppers and dosing systems, whereas each dust burner has one feed line from each of the three lock hoppers and dosing systems; and 
         FIG. 3  shows an example in which three gasification burners are associated with two lock hoppers and dosing systems, whereas each gasification burner has one feed line from each of the two lock hoppers and dosing systems; 
         FIG. 4  shows a block diagram of the technology according to the invention; 
         FIG. 5  shows a metering system for pulverized fuel according to the invention; 
         FIG. 6  shows a device for feeding pulverized fuel for high-capacity generators; 
         FIG. 7  shows a gasification reactor with full quenching; and 
         FIG. 8  shows a gasification reactor with partial quenching 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 1  shows an example in which each lock hopper and dosing system  1 ,  2 ,  3  is associated with one gasification burner  4 ,  5 ,  6 . The objective is to feed a gasification reactor for entrained flow gasification of carbon dust with an gross input of 1,000 MW with the 180 Mg/h carbon dust needed for this purpose. For this purpose, there are three lock hopper and dosing systems  1 ,  2 ,  3  ( FIG. 1 ), each supplying a gasification burner  4 ,  5 ,  6  through supply ports  4 . 1  through  6 . 3  thereof with 60 Mg/h combustible dust through three supply lines  1 . 1  through  3 . 3  with a feed capacity of 20 Mg/h. The capacity of each dust supply line  1 . 1  through  3 . 3  can be set in the range from 15-30 Mg/h. The three dust supply lines  1 . 1  through  3 . 3  of each lock hopper and dosing system  1 ,  2 ,  3  thereby end in a gasification burner  4 ,  5 ,  6 , supplying it with the 60 Mg/h carbon dust mentioned. All three lock hopper and dosing systems  1 ,  2 ,  3  must be in operation. Operation with two of the three gasification burners  4 ,  5 ,  6  results in unacceptable crooked burning in the gasification reactor. In the event of a failure of only one of supply lines  1 . 1  through  3 . 3 , burner  4 ,  5 ,  6  of concern may also be operated for a limited time with two supply lines. 
       FIG. 2  shows an example in which three lock hoppers and dosing systems  1 ,  2 ,  3  are associated with all three gasification burners  4 ,  5 ,  6 . The objective is the same as in  FIG. 1 . However, the three supply pipes  1 . 1  through  3 . 3  of each lock hopper and dosing system  1 ,  2 ,  3  are not connected to one gasification burner, but with all the three. Upon failure of one lock hopper and dosing system  1 ,  2 ,  3 , each gasification burner  4 ,  5 ,  6  may also be supplied for a limited time from the two still operating lock hopper and dosing systems  1 ,  2 ,  3 . 
       FIG. 3  shows two lock hopper and dosing systems  1 ,  2  which are connected to three gasification burners  4 ,  5 ,  6 . The objective is to supply a gasification reactor for entrained flow gasification of carbon dust having an output of 500 MW with the 90 Mg/h carbon dust needed for this purpose. For this purpose, 2 lock hopper and dosing systems  1 ,  2 , each having a capacity of 45 Mg/h, are arranged, each of the three supply lines  1 . 1  through  2 . 3  having an output of 15 Mg/h. Each gasification burner  4 ,  5 ,  6  is supplied from two supply lines  1 . 1  through  2 . 3  originating from a respective one of the lock hopper and dosing systems  1 ,  2 . As a result, two lock hopper and dosing systems  1 ,  2  can be utilized for middle-performance gasification reactors having three gasification burners  4 ,  5 ,  6 . 
       FIG. 4  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 . 
       FIG. 5  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 . 
       FIG. 6  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. 
       FIG. 7  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 . 
       FIG. 8  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. 
     The function will be described with a first example with reference to material flows and procedural processes: 
     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.degree. C., and the amount of oxygen needed is 208,000 m.sup.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 .mum. The ground pulverized fuel ( FIG. 1 ) is then fed to the metering system, the functional principle of which is shown in  FIG. 5 . The metering system consists of three identical units, as shown in  FIG. 6 , 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. 5 , 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.sup.3. 
     The gasification reactor  2  is shown and further explained in  FIG. 6 . 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.sup.3 NTP/h is fed to each gasification burner. The dust burners are arranged symmetrically at angles of 120.degree., 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.degree. 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 .lamda.=0.35 to 0.65. The value of .lamda. 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.sup.3 NTP/h and is distinguished by the following analysis: TABLE-US-00001 H.sub.2 19.8 vol. % CO 70.3 vol. % CO.sub.2 5.8 vol. % N.sub.2 3.8 vol. % NH.sub.3 0.03 vol. % HCN 0.003 vol. % COS 0.04 vol. % H.sub.2 S 0.4 vol. % 
     The hot crude gas at 1,550.degree. C. leaves the gasification chamber  2 . 3  together with the liquid slag through the discharge  2 . 5  and is cooled to 212.degree. 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 .mμm in size and salt mists not separated in the water scrubber  4 . For this purpose, the crude gas is cooled by about 5.degree. 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. 
     According to Example 2, the process of pulverized fuel feed is to occur according to  FIG. 2  and  FIG. 6 , 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.degree. 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.degree. C. is then fed to the water scrubber and partial condensation. 
     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.