Abstract:
A refractory lining system comprises an inner refractory layer; and an outer layer located outside of the inner refractory layer, the outer layer comprising: a plurality of layer segments; and at least one control joint located between the plurality of layer segments, the at least one control joint configured to allow expansion and contraction in the outer layer. A segment of an outer layer of a refractory lining comprises an edge shaped corresponding to a control joint configured to allow expansion and contraction in the outer layer.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The subject matter disclosed herein relates to refractory vessel design. 
         [0002]    A gasifier is a type of reactor used for partial oxidation of a fossil fuel, such as coal or a heavy fuel oil, to produce energy. Temperatures inside a gasifier vessel may reach over 700° C. during operation. A gasifier vessel may be insulated by a multi-layer refractory lining. The vessel and lining may comprise concentric cylindrical layers. During gasifier operation, high temperatures may cause the layers to expand outwardly, or radially. Each layer may expand differently, according to the temperature and the coefficient of thermal expansion (COE) of the particular layer. The inner layers are at a higher temperature, and may have a higher COE, than the outer layers. Inner layers may push against the outer layers due to expansion that occurs during operation of the gasifier, as the outer layers may expand less than the inner layer. This may cause the outer layers to develop cracks or open joints, resulting in gas bypass through the refractory lining. Gas bypass may cause high skin temperatures, or hot spots, in the outer shell of the gasifier. Forced shutdown of the gasifier may be necessary if hot spots become severe, leading to costly maintenance and loss of productivity. 
         [0003]    Accordingly, there remains a need in the art for a refractory lining that is resistant to cracking. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0004]    According to one aspect of the invention, a refractory lining system comprises an inner refractory layer; and an outer layer located outside of the inner refractory layer, the outer layer comprising: a plurality of layer segments; and at least one control joint located between the plurality of layer segments, the at least one control joint configured to allow expansion and contraction in the outer layer. 
         [0005]    According to another aspect of the invention, a segment of an outer layer of a refractory lining comprises an edge shaped corresponding to a control joint configured to allow expansion and contraction in the outer layer. 
         [0006]    According to yet another aspect of the invention, a method of making an outer layer of a refractory lining comprises forming a plurality of segments of the outer layer, each segment comprising an edge shaped corresponding to a control joint configured to allow expansion and contraction in the outer layer; and assembling the plurality of segments to form the outer layer of the refractory lining. 
         [0007]    These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other, features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
           [0009]      FIG. 1  is a side cross-section of an embodiment of a refractory lining. 
           [0010]      FIG. 2  is a top cross-section of an embodiment of a refractory lining comprising non-continuous joints. 
           [0011]      FIG. 3  shows a portion of an embodiment of outer thermal layer comprising a control joint. 
           [0012]      FIG. 4  shows an embodiment of a method of making an outer thermal layer comprising control joints. 
       
    
    
       [0013]    The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0014]    A gasifier vessel comprises a plurality of refractory lining layers to insulate the high temperature at which the gasification process occurs. If a lining layer cracks, gas from the gasification process may pass through the lining to the outer shell of the gasifier, resulting in hot spots on the outer shell and possible damage to the gasifier. A primary cause of hot spots in the outer shell of a gasifier may be prevented by providing a plurality of control joints in an outer layer of the refractory lining. Control joints, also referred to a non-continuous joints, slip joints or shiplaps, are a mechanical construction that allow expansion and contraction in a structure. The control joints mitigate radial expansion differences between the various layers of the gasifier lining. A slip plane within the control joint prevents formation of a continuous gas path during opening of the joint. The control joint may slide open by a small margin without significant gas bypass, reducing the stress and failure modes of the castable layer. A reduction in stress in an outer layer is accompanied by a proportional decrease in the amount of opposing stress in the inner layer, reducing the rate of failure and long term deformation or creep in the gasifier lining. Reliability of the gasifier is increased, resulting in reduced operating costs due to decreased unplanned outages. Incorporation of control joints into an outer layer does not entail significant increase in installation schedules or material costs, as materials and installation techniques already in use may be used to implement non-continuous joints in the outer layer. 
         [0015]    Referring to  FIG. 1 , a gasifier  100  may include a plurality of refractory lining layers, including but not limited to an inner refractory layer  101 , an outer thermal layer  102 , and an outer shell  103 . While three layers are shown in the embodiment of a gasifier shown in  FIG. 1 , a gasifier may include any appropriate number of lining layers. Outer thermal layer  102  may comprise a monolithic refractory, for example, concrete, in some embodiments. The inner refractory layer  101  expands radially during operation of the gasifier, and pushes against outer thermal layer  102 . This may cause outer thermal layer  102  to crack due various factors, including initial shrinkage, relatively low tensile strength, and lesser radial expansion. The cracking may be substantial, extending from the back of the refractory layer  101  directly to the outer shell  103 . Such cracking may result in gas bypass through outer thermal layer  102 , causing hot spots in outer shell  103 . 
         [0016]      FIG. 2  shows a top cross section of an embodiment of a refractory lining  200  comprising control joints. The refractory lining  200  comprises outer shell  204 , inner refractory layer  201 , and an outer thermal layer that comprises segments  202   a,    202   b,    202   c,  and  202   d  joined by control joints  203   a,    203   b,    203   c,  and  203   d.  The outer thermal layer may be divided into a plurality of segments; the four segments  202   a - d  shown in the embodiment of  FIG. 2  are for illustrative purposes only. 
         [0017]    Control joints  203   a - d  prevent cracking in the outer thermal layer by opening under pressure, creating space between segments  202   a - d.  The control joints  203   a - d  are shaped in a manner that opening of control joints  203   a - d  does not provide a continuous path for gas bypass from the refractory layer  201  to the outer shell  203 . Control joints  203   a - d  thereby relieve the stress in segments  202   a - d  that is caused by growth of inner refractory layer  201  during operation of the gasifier, preventing cracking of the refractory lining, while preventing hot spot formation. 
         [0018]      FIG. 3  shows portion of an embodiment of an outer thermal layer  300  comprising a control joint. The outer thermal layer comprises segments  301   a  and  301   b;  between the segments is a control joint  302 . Each of segments  301   a  and  301   b  comprise an edge that interlocks with the edge of the adjacent segment. Control joint  302  comprises a center slip plane  303 , which prevents the open joint from extending straight from the inner refractory layer  201  to the outer shell  204 . The slip plane  303  is angled to disallow gas bypass between segments  301   a  and  301   b  during opening of non-continuous joint  302 . The slip plane  303  may comprise a shiplap joint in some embodiments. The specific angle, curvature and dimensions of non-continuous joint  302  depend on the dimensions of the gasifier and the various layers that make up the refractory lining. Segments  301   a  and  301   b  may move apart without allowing gas to penetrate through the thermal layer. 
         [0019]    The outer thermal layer comprising control joints may be formed from a monolithic material, a cast in place refractory material, a deformable ceramic, or constructed with pre-cast shapes. An embodiment of a method  400  for casting an outer thermal layer comprising control joints is shown in  FIG. 4 . In block  401 , a plurality of segments of the outer layer are formed. Each segment comprises an edge shaped corresponding to a control joint configured to allow expansion and contraction in the outer layer. In block  402 , the segments are assembled to form the outer layer of the refractory lining. 
         [0020]    Although control joints in a refractory layer have been discussed above in the context of a gasifier for illustrative purposes, control joints may be incorporated into any cylindrical vessel comprising a refractory lining, which may include, but are not limited to, shaft furnaces, petrochemical reactors, or cylindrical cement kilns. 
         [0021]    While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.