Abstract:
A gasifier that includes a combustion chamber and a pressure vessel surrounding the combustion chamber, wherein the pressure vessel includes an inner surface. A heater surrounds the pressure vessel and increases a temperature of the inner surface of the pressure vessel. A method for operating a gasifier includes increasing an inner wall temperature of a pressure vessel surrounding the gasifier.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention generally involves a system and method for controlling a gasifier. Specific embodiments of the present invention may include a controller that adjusts conditions in the gasifier to reduce corrosion. 
       BACKGROUND OF THE INVENTION 
       [0002]    An Integrated Gasification Combined Cycle (IGCC) is known in the art for converting petroleum coke or coal into synthetic gas which may then be supplied to a gas turbine to generate power. The synthetic gas, a clean burning fuel, may be burned directly in the gas turbine or may be processed further to produce methanol and hydrogen for combustion in the gas turbine. 
         [0003]    The IGCC typically includes a gasifier to convert the petroleum coke or coal into the synthetic gas. The petroleum coke or coke is partially combusted with oxygen in a gasifier at a high temperature and pressure to produce the synthetic gas. The gasifier may be constructed of an insulated brick lining surrounded by a pressure resistant steel vessel. The brick lining is typically designed to withstand internal gasifier temperatures of approximately 2,500-3,000° F., while the steel vessel is typically designed to withstand an inner surface temperature of approximately 400-600° F. 
         [0004]    The gasification process may produce highly corrosive byproducts, such as ammonium chloride. If the dew point of the inner surface of the steel vessel is less than the dew point of the corrosive byproducts, then the corrosive byproducts may condense on an inside surface of the steel vessel, causing aqueous corrosion on the inside surface of the steel vessel. The aqueous corrosion on the inside surface of the steel vessel is undesirable in that it may result in unplanned outages for maintenance and/or repair and ultimately reduces the useful life of the steel vessel. 
         [0005]    Various attempts have been made to control the production and/or effects of the corrosive byproducts. For example, attempts have been made to indirectly monitor the production of the synthetic gas, and thus the production of the corrosive byproducts. Other attempts have involved costly external wind deflectors and variations in the design of the brick insulation. However, an improved system and method for controlling the gasifier would be useful in reducing corrosion caused by the corrosive byproducts. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0006]    Aspects and advantages of the invention are set forth below in the following description, or may be obvious from the description, or may be learned through practice of the invention. 
         [0007]    One embodiment of the present invention is a gasifier that includes a combustion chamber and a pressure vessel surrounding the combustion chamber, wherein the pressure vessel includes an inner surface. A heater surrounds the pressure vessel and increases a temperature of the inner surface of the pressure vessel. 
         [0008]    Another embodiment of the present invention is a gasifier that includes a combustion chamber and a pressure vessel surrounding the combustion chamber, wherein the pressure vessel includes an inner surface. A heater surrounds the pressure vessel, and a controller connected to the heater generates a heater signal to activate the heater. 
         [0009]    The present invention also includes a method for operating a gasifier. The method includes increasing an inner wall temperature of a pressure vessel surrounding the gasifier. 
         [0010]    Those of ordinary skill in the art will better appreciate the features and aspects of such embodiments, and others, upon review of the specification. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    A full and enabling disclosure of the present invention, including the best mode thereof to one skilled in the art, is set forth more particularly in the remainder of the specification, including reference to the accompanying figures, in which: 
           [0012]      FIG. 1  is a simplified cross-section of a gasifier according to one embodiment of the present invention; and 
           [0013]      FIG. 2  is a simplified cross-section of a gasifier according to an alternate embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0014]    Reference will now be made in detail to present embodiments of the invention, one or more examples of which are illustrated in the accompanying drawings. The detailed description uses numerical and letter designations to refer to features in the drawings. Like or similar designations in the drawings and description have been used to refer to like or similar parts of the invention. 
         [0015]    Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that modifications and variations can be made in the present invention without departing from the scope or spirit thereof. For instance, features illustrated or described as part of one embodiment may be used on another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents. 
         [0016]      FIGS. 1 and 2  show a simplified cross-section of a gasifier  10  according to various embodiments of the present invention. As a general proposition, the gasifier  10  includes a combustion chamber  12  surrounded by a pressure vessel  14 . The combustion chamber  12  provides an enclosed volume for combustion of fuel and oxygen to produce a synthetic gas. As such, the combustion chamber  12  is constructed from material capable of withstanding the maximum temperature of the combustion. For example, the combustion chamber may include a refractory insulated brick lining  16  capable of continuous exposure to temperatures of approximately 2,500-3,000° F. The pressure vessel  14  is generally constructed from steel or a steel alloy capable of containing the pressure generated by the combustion and withstanding a continuous exposure to temperatures of approximately 400-600° F. The gasifier  10  may include additional surrounding or partially surrounding layers of material that insulate, contain, or otherwise enclose the gasifier. For example, as shown in  FIGS. 1 and 2 , a refractory grout  18  coating between the combustion chamber  12  and the pressure vessel  14  may be used to attenuate heat between the combustion chamber  12  and the pressure vessel  14 . 
         [0017]    The gasifier  10  may further include separate or combined supplies of fuel  20 , oxidants  22 , and/or diluents  24  to the combustion chamber  12 . The fuel generally comprises petroleum coke, coal, or another suitable product to be gasified. The oxidants generally comprise oxygen, an oxygen compound, or another chemical capable of combusting with the fuel. The diluents generally comprise nitrogen, argon, or another inert gas for diluting the oxidants prior to combustion. The supply of fuel  20 , oxidants  22 , and/or diluents  24  may comprise any suitable tank, piping, and/or valve system for transporting the fuel, oxidants, or diluents to the gasifier  10 . The fuel, oxidants, and/or diluents combine in the combustion chamber  12  to produce the synthetic gas. In addition, the combustion produces one or more byproducts, including corrosive compounds such as ammonium chloride. 
         [0018]    As shown in the embodiment illustrated in  FIG. 1 , the gasifier  10  may further include a heater  26  surrounding an outer wall  28  of the pressure vessel  14 . The heater  26  may comprise any suitable system for supplying heat to the outer wall  28  of the pressure vessel  14  so that the heat penetrates through the pressure vessel  14  to increase the temperature of an inner wall  30  of the pressure vessel  14 . For example, the heater  26  may comprise conductive, radiant, or convective heaters such as, for example, resistive coils, infrared heaters, heated coolant, or any suitable system known to one of ordinary skill in the art for providing heat. 
         [0019]    The heater  26  may be manually activated or energized as needed to increase the temperature of the inner wall  30  of the pressure vessel  14 . For example, measured parameters of the gasifier  10 , content of the fuel, production rate of the synthetic gas, or any other operational parameter may be used to determine when to activate or energize the heater  26 . In this manner, the temperature of the inner wall  30  of the pressure vessel  14  may be maintained greater than the dew point of any corrosive compound produced during combustion to reduce and/or prevent condensation of the corrosive compound on the inner wall  30  of the pressure vessel  14 . 
         [0020]    As shown in  FIG. 1 , alternate embodiments of the present invention may also include a controller  32  connected to the heater  26 . The controller  32  may send a heater signal  34  to the heater  26  to activate or energize the heater  26 . For example, the controller  32  may be programmed to activate or energize the heater  26  at timed intervals, based on the measured parameters of the gasifier  10 , content of the fuel, production rate of the synthetic gas, or any other operational parameter. As described herein, the technical effect of the controller  32  is to control the temperature of the inner wall  30  of the pressure vessel  14  and/or pressure inside the combustion chamber  12  and/or pressure vessel  14 . The controller  32  may be a stand alone component or a sub-component included in any computer system known in the art, such as a laptop, a personal computer, a mini computer, a mainframe computer, or industrial controllers, microcontrollers, or embedded systems. The various controller and computer systems discussed herein are not limited to any particular hardware architecture or configuration. Embodiments of the systems and methods set forth herein may be implemented by one or more general-purpose or customized controllers adapted in any suitable manner to provide the desired functionality. The controller  32  may be adapted to provide additional functionality, either complementary or unrelated to the present subject matter. For instance, one or more controllers may be adapted to provide the described functionality by accessing software instructions rendered in a computer-readable form. When software is used, any suitable programming, scripting, or other type of language or combinations of languages may be used to implement the teachings contained herein. However, software need not be used exclusively, or at all. For example, as will be understood by those of ordinary skill in the art without required additional detailed discussion, some systems and methods set the forth and disclosed herein may also be implemented by hard-wired logic or other circuitry, including, but not limited to, application-specific circuits. Of course, various combinations of computer-executed software and hard-wired logic or other circuitry may be suitable as well. 
         [0021]    The gasifier  10  may further include a corrosion sensor  36  between the pressure vessel  14  and the combustion chamber  12 . The corrosion sensor  36  may comprise an electronic circuit that measures a voltage potential or current flow created by the presence of the corrosive compounds on the inner wall  30  of the pressure vessel  14 . The corrosion sensor  36  may thus generate a corrosion signal  38  reflective of the presence and/or amount of corrosive compounds present between the pressure vessel  14  and the combustion chamber  12 . The corrosion signal  38  may be manually interpreted and acted on by an operator to activate or energize the heater  26 , as desired. Alternately, the corrosion sensor  36  may be connected to the controller  32  to transmit the corrosion signal  38  to the controller  32 . In this manner, the controller  32  may be programmed to activate or energize the heater  26  upon receiving a predetermined corrosion signal. 
         [0022]    One of ordinary skill in the art will readily appreciate that the gasifier  10  shown in  FIG. 1  may provide a method for reducing and/or preventing corrosive compounds from condensing between the pressure vessel  14  and the combustion chamber  12 . The method increases the temperature of the inner wall  30  of the pressure vessel  14  surrounding the gasifier  10 . The heater  26  may thus be manually activated or energized to increase the temperature of the inner wall  30  of the pressure vessel  14  to a temperature greater than the dew point of the corrosive compound. In alternate embodiments, the controller  32  may be used to automatically activate or energize the heater. In addition, the corrosion sensor  36 , if present, may provide the corrosion signal  38  to the controller  32 , and the controller  32  may activate or energize the heater  26  upon receiving the predetermined corrosion signal. 
         [0023]      FIG. 2  shows the gasifier  10  according to an alternate embodiment of the present invention. The gasifier  10  again comprises the combustion chamber  12 , pressure vessel  14 , and supplies of fuel  20 , oxidants  22 , and diluents  24  as previously described with respect to the embodiment shown in  FIG. 1 . In this particular embodiment, however, the gasifier  10  reduces and/or prevents the condensation of corrosive compounds between the pressure vessel  14  and the combustion chamber  12  by adjusting the pressure in the combustion chamber  12  and/or pressure vessel  14 . Specifically, the flow rate of the fuel, oxidants, and/or diluents may be adjusted to raise or lower the amount of combustion occurring in the combustion chamber  12 , producing a corresponding increase or decrease in the pressure in the combustion chamber  12  and/or pressure vessel  14 . The increase or decrease in the pressure in the combustion chamber  12  and/or pressure vessel  14  produces a corresponding increase or decrease in the dew point of any corrosive compounds, thus reducing and/or preventing the condensation of any corrosive compounds between the pressure vessel  14  and the combustion chamber  12 . 
         [0024]    Measured parameters of the gasifier  10 , content of the fuel, production rate of the synthetic gas, or any other operational parameter may be used to manually adjust the flow rate of the fuel, oxidants, and/or diluents. For example, the gasification of higher energy fuel generally results in a higher pressure in the combustion chamber  12  and pressure vessel  14 . This higher pressure in the combustion chamber  12  and pressure vessel  14  produces a corresponding higher dew point for any corrosive compounds produced as byproducts. The higher dew point for the corrosive compounds may lead to undesirable condensation of the corrosive compounds on the relatively cooler inner wall  30  of the pressure vessel  14 . Therefore, the flow of fuel and/or oxidants may be decreased to reduce the pressure in the combustion chamber  14  and produce a corresponding decrease in the dew point of any corrosive compounds produced as byproducts. Alternately, or in addition, the flow rate of the diluents may be increased to raise the dilution of the oxidants prior to combustion, producing a similar increase in the pressure and dew point of any corrosion compounds produced as byproducts. 
         [0025]    As shown in  FIG. 2 , the embodiment shown in  FIG. 2  may also include the controller  32  and/or corrosion sensor  36  as previously described with respect to  FIG. 1 . For example, the controller  32  may be programmed to generate a fuel signal  40  to control the flow of fuel  20  to the combustion chamber  12 , an oxidant signal  44  to control the flow of oxidants  22  to the combustion chamber  12 , and/or a diluent signal  42  to control the flow of diluents  24  to the combustion chamber  12  to adjust the pressure inside the pressure vessel  14  and/or combustion chamber  12 . The controller  32  may generate the fuel  40 , oxidant  44 , and/or diluent  42  signals at timed intervals, based on the measured parameters of the gasifier  10 , content of the fuel, production rate of the synthetic gas, or any other operational parameter. 
         [0026]    Alternately, or in addition, the corrosion sensor  36  may generate the corrosion signal  38  reflective of the presence and/or amount of corrosive compounds present between the pressure vessel  14  and the combustion chamber  12 , as previously described with respect to  FIG. 1 . The corrosion signal  38  may be manually interpreted and acted on by an operator to adjust the flow of fuel, oxidants, and/or diluents to raise or lower the pressure in the pressure vessel  14  and/or combustion chamber  12 , as desired. Alternately, the corrosion sensor  36  may be connected to the controller  32  to transmit the corrosion signal  38  to the controller  32 . In this manner, the controller  32  may be programmed to adjust the flow of fuel, oxidants, and/or diluents upon receiving the predetermined corrosion signal. 
         [0027]    One of ordinary skill in the art will readily appreciate that the gasifier  10  shown in  FIG. 2  may provide a method for reducing and/or preventing corrosive compounds from condensing between the pressure vessel  14  and the combustion chamber  12 . The method adjusts the pressure inside the pressure vessel  14  and/or combustion chamber  12  so that the dew point of the corrosive compound is less than the temperature of the inner wall  30  of the pressure vessel  14 . The pressure inside the pressure vessel  14  and/or combustion chamber  12  may be adjusted by adjusting the flow of fuel  20 , oxidants  22 , and/or diluents  24 . In addition, or alternately, the method may include detecting any corrosive compounds inside the pressure vessel  14  and adjusting the pressure inside the pressure vessel  14  and/or combustion chamber  12  according to the presence and/or amount of any detected corrosive compounds. 
         [0028]    This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other and examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.