Patent Publication Number: US-2005132647-A1

Title: Refractory armored quench ring

Description:
FIELD OF THE INVENTION  
      The present invention is directed to an improved gasifier within which is a reactor that gasifiers carbonaceous fuel mixtures to produce a hot effluent comprising synthesis gas and residual slag. More specifically, this invention is directed to a support element that is located on the gasifier quench ring within the gasifier and that is used to protect the quench ring from the high temperatures of the hot effluent gas exiting through the reaction chamber floor. The support element protects the quench in such a manner that the quench ring is a refractory armored quench ring.  
     BACKGROUND OF THE INVENTION  
      In the production of synthesis gas by the partial oxidation of a carbonaceous fuel mixture, the process is conducted most effectively under high temperature and high pressure conditions. For example, for the production of synthesis gas from a carbonaceous fuel such as particulated coal, coke or even oil, a preferred operating temperature range of about 2,000° F. to 3,000° F. is maintained at a pressure of between about 5 to 250 atmospheres. The harsh operating conditions experienced in such a process, and in particular the wide temperature variations encountered, will typically impose a severe strain on many segments of a gasifier.  
      The present invention is addressed to an improvement in the structure of the gasifier, and more specifically to an improvement of the quench ring structure. The gasifier includes a reaction chamber in which the fuel mixture is gasified and wherein the floor of said reaction chamber is shaped to induce gas recirculation and permit liquefied slag to flow therefrom. A quench chamber holding a water bath is positioned in the reactor to receive and cool the hot produced effluent. A constricted throat that connects the reaction chamber with the quench chamber directs a stream of the effluent through a dip tube which defines a guide passage to conduct said effluent into the water bath. A toroidal shaped quench ring depending from the gasifier floor is spaced outwardly of the dip tube to direct a water stream onto the dip tube&#39;s guide surface. Additionally, refractory material in the throat of the reaction chamber is extended past the reaction chamber floor and is supported by a structure that depends from the quench ring. The quench ring has a vertical front face and removable/replaceable metal apron that provides a small support floor for the extended throat refractory.  
      Due to its function and location within the gasifier, the quench ring is exposed to the gasifier&#39;s maximum temperature conditions by virtue of the hot product gas which makes contact with it as the gas is passed from the reaction chamber to the water bath. The present invention, which provides an insulating barrier that protects the quench ring, decreases the strains and stresses on the quench ring.  
     BACKGROUND ART  
      The following references relate to a variety of systems and devices for protecting the interior section of a gasifier.  
      Brooker, U.S. Pat. No. 6,228,224, discloses a protective refractory shield for a gasifier that is mounted to a fuel injector nozzle or to a vertical surface of a quench ring of the gasifier.  
      Brooker et al., U.S. Pat. No. 5,851,497, discloses a throat section of a gasifier wherein the throat section has an internal cooling system comprised of a network or supporting frame of interconnected pipes and or tubes which carry a liquid cooling medium through the throat.  
      Dach, U.S. Pat. No. 4,828,580, discloses a gasifier quench ring with an insulating collar that protects the quench ring from degradation resulting from slag or other elements that are present in a gasifier reactor.  
      Becker et al., U.S. Pat. No. 4,828,9, discloses a gasifier quench ring comprising a support element that includes a refractory belt that is removably positioned on a support element. The refractory belt defines a thermal barrier located between the quench ring and the hot effluent that is exiting the gasifier reactor.  
      U.S. Pat. No. 4,218,423, issued on Aug. 19, 1980 in the name of Robin et al., illustrates one form of a quench ring and a dip tube assembly wherein an annular channel forms a conduit for carrying cooling water that is used to cool the hot product gas coming from a gasifier reaction chamber. Additionally, the quench ring has a plurality of short passages that are drilled through the quench ring to provide a swirl of cooling water that is directed against the inside of the dip tube. The &#39; 423  patent, however, fails to protect the quench ring from the harsh thermal elements of the reactor.  
      U.S. Pat. No. 4,444,726, issued on Apr. 24, 1984 in the name of Crotty et al., illustrates another form of a quench ring and dip tube assembly for a reactor vessel. Specifically, it provides for two annular conduits that carry cooling water to quench the product from the reaction chamber, as well as a dip tube that is used for carrying the hot product gases and for directing molten slag from the chamber outlet into a bath of quench water. Although a portion of the assembly is insulated, it does not provide an effective barrier which would avoid contact between the hot effluent stream and the cold quench ring surface.  
      There are several problems that are encountered due to the high temperature conditions within the gasifier. Among those problems are the development of thermal stresses, which often result in damage to the quench ring as a result of the ring&#39;s close proximity to the hot effluent stream, and the lack of protection of the metal surfaces of the quench ring. These problems are often manifested in the form of cracks and fissures which develop in parts of the quench ring. The latter can occur anywhere along the exposed surface of the quench ring, but are even more prevalent in areas where sharp edges are present such that any physical or thermal stress would be magnified and result in spraying of liquid coolant into the reaction chamber.  
      One problem that may be experienced in gasifiers is the propensity of molten slag to harden and freeze in the gasifier&#39;s constricted throat. This phenomenon occurs when the throat section becomes sufficiently cool to reduce the slag temperature. This undesirable chilling action can, under particular circumstances, severely block the constricted throat opening, thereby precluding further operations.  
      Another problem with prior art quench ring and dip tube assembly arrangements includes the inability to repair or partially replace the quench ring while the gasifier is still fairly hot. Repairing or replacing the quench ring when the entire gasifier has cooled down to approximately less than  100 OF significantly delays resumption of the operation of the gasifier.  
      Yet another problem with the prior art quench ring and dip tube assembly arrangements includes small or ineffectively configured drip edges in the refractory lining above the quench ring. These drip edges are easily damaged and thus permit the flow of molten slag down along the throat surface and onto the inner diameter surface of the quench ring and even the dip tube instead of inducing the slag to free fall through the dip tube and into the quench bath as intended. When the flow is misdirected, the molten slag can stick to and freeze on the dip tube inner surface, thereby creating a “shadow” effect wherein the quench water from the quench ring will not adequately coat the inner diameter surface of the dip tube below the frozen slag. An uncoated, unprotected portion of the dip tube such as this can lead to overheating and burn-through of the dip tube. Overheating and burn-through are very serious problems for several reasons, not the least of which is that hot, unquenched syngas will subsequently flow into downstream units of the gasification processes that are not equipped for the high temperature unquenched gasses.  
      Another problem with some prior art is the sharp edges on the quench rings. These sharp edges are not as effectively cooled by the flowing quench water as are curved or flat surfaces since they result in localized stagnant regions within the flow field. Accordingly, the sharp edges tend to run hotter, thereby increasing thermal stresses within the quench ring structure.  
      None of this prior art recognizes the improved quench ring design of the present invention, much less the significant unexpected improvements that this invention provides.  
     SUMMARY OF THE INVENTION  
      Toward overcoming the gasifier operating defects in gasifiers of the type noted, there is presently disclosed a gasifier quench ring which is provided with refractory layers that are located radially inward of the quench ring&#39;s normally exposed surfaces. The refractory layers protect the quench ring from exposure to the high temperature synthesis gas and slag exiting the reaction chamber bottom outlet. The quench ring is thereby insulated and physically protected by refractory materials that are supported by a refractory bearing apron. The protective thermal resistant barrier comprises dense refractory materials and insulating refractory ceramic fiber. The quench ring is thereby insulated by the protective thermal resistant barrier which is supported by a refractory bearing apron. The various refractory materials minimize thermal stresses which would normally be encountered by the quench ring during the gasification process.  
      Stated otherwise, there is presently provided a reactor for gasifying a carbonaceous fuel mixture to produce a hot effluent comprising synthesis gas and residual slag. The reactor includes a reaction chamber in which the fuel mixture is partially oxidized by oxygen, air, or mixtures thereof to form synthesis gas and residual slag, wherein the floor of said chamber is shaped to permit liquefied slag to flow therefrom.  
      A quench chamber containing a water bath is positioned inside the gasifier to receive and cool the hot produced effluent. A constricted throat passageway allows communication between the reaction chamber and the quench chamber. The quench chamber contains a dip tube which defines a passage to guide the stream of hot effluent from the reaction chamber into the water bath of the quench chamber.  
      A toroidal shaped quench ring attached to a gasifier floor is spaced above the top end of the dip tube to direct a water stream onto a dip tube&#39;s guide surface. A support element depending from the quench ring extends into the effluent guide passage and supports throat refractory materials which define a protective thermal resistant barrier between the quench ring and the hot produced effluent.  
      Accordingly, in its broadest embodiment, the present invention is directed to an improved quench ring in combination with a reactor vessel having a refractory lined reaction chamber with a bottom outlet and a floor to support said refractory lined reaction chamber, comprising: 
      (a) a quench ring for carrying a supply of cooling water therein and removably mounted beneath said floor;     (b) a protective thermal resistant barrier mounted contiguous to said quench ring; and     (c) said protective thermal resistant barrier abutted to the bottom outlet of the reaction chamber.    

      It is therefore an object of the invention to provide an improved gasifier for producing synthesis gas, in which a gasifier dip tube is wetted by a quench ring which embodies a protective thermal resistant barrier, which comprises dense refractory brick, dense refractory ramming mix and refractory insulation, such as refractory ceramic fiber, to segregate it from the hot effluent as well as from hot segments of the gasifier.  
      A further object is to provide a liquid carrying quench ring for a gasifier, which is separated from hot effluent produced in the gasifier reaction chamber by means of a protective thermal resistant barrier supported by the quench ring exposed surfaces.  
      A still further object is to provide a gasifier quench ring having a removable refractory barrier comprising a refractory bearing apron, dense refractory brick, dense refractory ramming mix and refractory insulation, such as refractory ceramic fiber, positioned to form a portion of the guide passage which conducts hot effluent gas between the gasifier&#39;s constricted throat and the water bath.  
      The present invention overcomes the disadvantages of the prior art. Because the protective thermal resistant barrier segregates the gasifier&#39;s constricted throat from the quench ring, the molten slag is not rapidly cooled by the cooling liquid circulating in the quench ring and does not harden and freeze in the constricted throat. Instead, the slag remains molten until it contacts the water on the inner surface of the dip tube or in the water bath.  
      Another disadvantage of the prior art that the present invention overcomes is the inability to repair the quench ring while the gasifier is still fairly hot. Because the protective thermal resistant barrier is easily replaceable, it can be done while the gasifier is still moderately hot; and, because the protective thermal resistant barrier prevents damage to the metal surface of the quench ring during gasifier operations, it therefore precludes the need to remove the quench ring from the gasifier.  
      Another disadvantage of the prior art that the present invention overcomes is the sharp edges that are on some quench rings. The quench ring in the present invention has a toroidal annular surface. The rounded toroidal shape promotes even cooling of the quench ring and does not increase thermal stresses that are normally found in quench rings having sharp edges/angled surfaces intersections. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The invention may be understood by reference to the following description taken in conjunction with the accompanying drawings.  
       FIG. 1  is a vertical elevation view in cross-section of a gasifier or reactor of the type contemplated.  
       FIG. 2  is an enlarged segmentary view of the quench ring area of  FIG. 1 .  
      FIGS.  3 A-C are a detailed view of the quench ring apron of the present invention. 
    
    
      While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.  
     DETAILED DESCRIPTION OF THE INVENTION  
      Illustrative embodiments of the invention are described below. In the interest of clarity, not all features of an actual embodiment are described in this specification. It will, of course, be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developers&#39; specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.  
      Referring to  FIG. 1 , in general, there is provided a gasifier or reactor vessel for gasifying a carbonaceous fuel mixture comprised of either solid, liquid or gaseous materials. The gasification process produces a hot effluent which comprises a synthesis gas, primarily composed of carbon monoxide and hydrogen, and a residue normally in the form of slag, especially when the fuel is a solid such as coal or coke. The gasifier is embodied in a heavy walled steel shell which is positioned to form a downflowing stream of the effluent which includes the hot produced synthesis gas.  
      A reaction chamber within the shell receives a pressurized stream of the carbonaceous fuel mixture by way of a feed injector. The latter is fed with a source of the carbonaceous fuel as well as with a source of an oxidation medium, which is usually a gas such as oxygen or air, whereby to form a reactive mixture.  
      The products of gasification (i.e., the hot effluent and slag) that are generated in the reaction chamber are discharged through the reaction chamber floor and are cooled in a liquid holding quench chamber.  
      To facilitate passage of hot produced gas as it leaves the reaction chamber, a dip tube is positioned to guide the effluent into a liquid bath. The dip tube, oriented in the generally upright position, is supported by a liquid conducting quench ring which directs a stream of coolant such as water along the dip tube&#39;s exposed guide face or inner wall.  
      Referring to  FIG. 1 , more specifically, a gasifier or reactor vessel  10  of the type contemplated embodies an elongated metallic steel walled shell  11 . The gasifier is normally operated in an upright position to permit the downflowing of the produced product. Shell  11  includes a reaction chamber  12  at its upper end in which the partial oxidation of the carbonaceous fuels takes place by exposure to the oxidation medium, typically at the high operating temperatures of from about 2000° F. to about 3000° F. The reaction chamber is actually the cavity formed by inner walls  13  at the upper end of shell  11 . Inner wall  13  is preferably formed of a suitable refractory material capable of withstanding the noted high temperatures and providing insulation to shell  11 . The composition of such refractory material, including the refractory brick and refractory fiber, is well known to those skilled in the art. Typically, such refractory material is comprised of alumina or chromia-rich ceramic products that occasionally also bear lesser amounts of magnesia, zirconia, and the like.  
      Feed injector  14  is removably positioned-at the top of shell  11  to inject the carbonaceous fuel mixture such as particulated coal or coke from source  16  into reaction chamber  12 . An amount of gas which is capable of partially oxidizing the carbonaceous fuel mixture is contained in a pressurized source  17  and is concurrently fed into injector  14  as part of the fuel mixture.  
      The invention can be applied equally well to gasifiers which burn a variety of carbonaceous solid, liquid, or gaseous fuels. To illustrate an embodiment of the present invention, it will be assumed that the injector  14  is being fed with a source of coal. The latter is preferably pre-ground and formed into a slurry of desired consistency by the addition of a sufficient amount of water in a manner which is well known to those skilled in the art. The pressurized oxidizing gas at source  17  is normally oxygen, air, or a mixture thereof.  
      The lower end of reaction chamber  12  is defined by a downwardly sloping refractory floor  35 . This configuration enhances the discharge of hot gas and slag from the reaction chamber  12 , and also facilitates more thorough reaction in the reaction chamber by increasing gas recirculation.  
      The lower end of shell  11  encloses a quench chamber  19  into which the products of gasification are directed. Here, both the solid and gaseous products from the gasification reaction contact a quench bath  21  which is most conveniently comprised of a liquid, such as water. The cooled gas then emerges from the quench bath  21  into disengaging zone  26  before leaving the quench chamber through nozzle  22 . The cooled synthesis gas is now processed in downstream equipment and operations into a more desirable form. The solid or slag component of the effluent sinks through bath  21  to be removed by way of discharge port  23  into lockhopper  24 .  
      Reaction chamber  12  and quench chamber  19  communicate with each other through constricted throat  27  formed in reaction chamber floor  33 . The constricted throat is also referred to as the bottom outlet. To properly guide the hot effluent from reaction chamber  12  directly into the liquid in quench bath  21 , quench chamber  19  is provided with a dip tube  29  having an upper edge  31  positioned lateral to constricted throat  27 . Dip tube  29  further includes a lower edge which bears a series of serrations  32  and which terminates in the liquid coolant quench bath  21 .  
      The reference numbers used in  FIG. 1  define the same elements in  FIG. 2 . Referring to  FIG. 2 , constricted throat  27  defines the initial guide passage through which the high temperature effluent gas and slag pass.  FIG. 2  illustrates an embodiment of the present invention, an improved quench ring for use in a gasifier. Desirably, cooling of the slag is carried out in liquid bath  21  (not shown in  FIG. 2 ). However, if there is premature cooling in and immediately beneath the throat  27 , which has been the problem with prior art configurations, a solid accumulation or barrier will typically undesirably form. It is desirable therefore to decrease premature cooling in the throat  27 . By means of the armored refractory quench ring of the present invention, such premature cooling of slag in throat  27  is dramatically reduced.  
      In accordance with the present invention, in order to decrease premature cooling of slag in the constricted throat  27 , the constricted throat  27  of a reaction chamber refractory floor  33  has been extended to an elevation below that of the quench ring  36 . The quench ring transmits a supply of pressurized cooling water from a source  18  (not shown in  FIG. 2 ) and is removably mounted beneath the floor  46  of the reaction chamber vessel. A protective thermal resistant barrier protects the quench ring  36  from the harsh, high temperatures and corrosive/erosive slag that pass through the reaction chamber bottom outlet  27  and decreases the premature cooling of slag in the throat. The protective thermal resistant barrier comprises a refractory barrier and a metal apron. The refractory barrier comprises a dense refractory brick  49 , dense ramming mix  73 , and refractory insulation, such as refractory ceramic fiber  53 . The entire protective thermal resistant barrier is removably mounted and is contiguous to the quench ring and is abutted up to the bottom outlet of the reaction chamber  27 . The apron supports the refractory materials and is comprised of an apron upper edge  61 , an apron vertical, cylindrical side wall  48 , an apron lip  70 , and an apron floor  50 . The apron is mounted adjacent to the quench ring. The apron is removably affixed to the bottom edge of the quench ring hotface  47 . Furthermore, the refractory barrier is removably affixed to the apron and the bottom outlet; and, refractory barrier is mounted between the apron and the bottom outlet  27 .  
      Functionally, the inner wall of dip tube  29  defines a cylindrical guide path for the hot effluent including both the gaseous and solid components as they flow from throat  27  into liquid coolant quench bath  21 . The inner wall or guide surface of the cylindrical dip tube  29  is wetted by directing one or more pressurized streams of liquid coolant, typically water, against the inner walls.  
      In one embodiment of the present invention, quench ring  36  is comprised of spaced apart inner wall  37  and outer wall  38 . The inner wall  37 , outer wall  38 , and upper plate  41  define annular toroidal manifold passage or chamber  42  which is fed with a pressurized source of coolant by way of one or more risers.  
      Quench ring  36  is removably fastened in place beneath the floor  46  of reaction chamber  12  by a plurality of fastening bolts  44  in outer wall  38 . A gasket  45  comprised from a material suitable to create a gas impermeable barrier, prevent friction, prevent deterioration, and prevent wear, such as graphite, is affixed to and located between the upper plate of the quench ring  36  and the floor  46  of the reaction chamber  12 .  
      As noted earlier, upper plate  41  of the quench ring  36  has depending from it a quench ring hotface  47  that is perpendicular to the upper plate  41 . The upper plate  41  and quench ring hotface  47  are comprised of a material that is made of Incoloy  825  or other suitable high temperature, corrosion resistant alloy.  
      The quench ring hotface  47  is the side of the quench ring that lies closest to the bottom outlet of the reaction chamber. The quench ring hotface  47  is spaced from the dip tube  29  upper edge  31  to define an annular vent passage  54 . Vent passage  54  will in turn direct a continuous liquid coolant stream against the inner surface of dip tube  29  to facilitate passage of the slag carrying effluent into the liquid coolant quench bath  21  without damage to the dip tube. The quench ring hotface  47  includes a quench ring lip  52  which is a protrusion that is attached to and extends perpendicularly from the quench ring hotface and towards the constricted throat  27 . The quench ring hotface  47  supports a removable apron that mates to the lower edge of the quench ring hotface. The quench ring hotface lower edge has an angled geometric configuration that facilitates a watertight, secure junction  79  when it mates with a complementary configuration on the apron upper edge.  
      The apron comprises an apron upper edge  61 , apron vertical, cylindrical side wall  48 , apron lip  70 , and apron floor  50 . The apron is a single, unitary structure fabricated prior to affixing to the lower edge  59  of the quench ring hotface  47 . The apron is fabricated from Incoloy  825  or other suitable high temperature, corrosion resistant alloy. The apron is secured to the quench ring hotface  47  at the mated junction  79  of quench ring hotface lower edge  59  and apron upper edge  61  through the use of a plurality bolts  51  with standard lock washers and also locking plugs  77 . The bolts  51  pass through large, threaded holes in the apron floor  50 , then through smaller, concentrically aligned holes in the apron lip  70 , and lastly into appropriately threaded and concentrically aligned holes in the quench ring hotface lip  52  to draw the mated junction  79  securely together. Locking plugs  77  are then threaded into the holes in the apron floor  50  until they are tight up against the head of the bolts  51 , to insure complete steadfastness of the position of the securing bolts  51 . The quench ring hotface lip  52  and the apron lip  70  can be either continuous protrusions around the full perimeter of their respective structures, or discontinuous lips positioned as appropriate. The apron floor  50  is a shelf-like structure which is designed for supporting the refractory materials that will protect the quench ring hotface  47  and the apron from the high temperature effluent products exiting the reaction chamber outlet bottom  27 . Towards that end, a plurality of refractory anchors  75  made of Incoloy  825  or other suitable high temperature, corrosion resistant alloy are affixed to the bottom surface of the apron floor  50  by any appropriate means such as welding, so as to provide a support mechanism for the dense refractory ramming mix  73 . A refractory barrier which comprises dense refractory brick  49 , dense refractory ramming mix  73 , and refractory insulating material such as high alumina refractory ceramic fiber (RCF)  53  creates a substantially uniform diameter throat concentric with constricted throat  27 , and provides significant thermal, corrosive, and erosive protection to the quench ring hotface  47 , from high temperature effluents traveling through the constricted throat  27 . Preferably, RCF  53  is used in the refractory barrier. RCF  53  of appropriate density and texture is located between the apron floor  50  and the overlying dense refractory brick  49 , between the apron floor  50  and the underlying dense refractory ramming mix  73 , between the dense refractory brick  49  and the leading, inner edge of the reaction chamber floor  46 , and between the dense refractory brick  49  and the quench ring hotface  47 . RCF  53  reduces the heat flow from the constricted throat  27  to the quench ring hotface  47 , thereby preventing the quench ring hotface  47  and apron from being exposed to the high temperatures of the effluent, thereby limiting their thermal stresses. RCF  53  also keeps the reaction chamber floor  46  from exceeding its temperature limit. Insulation afforded by the RCF  53  also prevents unwanted cooling of the dense refractory bricks  49  and premature cooling of molten effluent materials. Unwanted and unnecessary preheating of the cooling water flowing through the quench ring is also avoided through the use of the RCF  53 . Installation of virtually all refractory materials is preferably achieved prior to attachment of the refractory-laden apron to the quench ring hotface in the gasifier, though in-situ repairs and replacements are possible. Installation of the RCF  53  on the top and bottom surfaces of the apron floor  50  should occur first, followed by the installation of the dense ramming mix  73  with the apron preferably in an inverted orientation. The dense refractory ramming mix  73  is held securely in place by means of refractory anchors  75  that are welded to the bottom of the apron floor  50  prior to installation of the RCF  53 . The specific geometry, spacing configuration and spacing density of the anchors, as well as installation of the ramming mix to yield the preferred cross-sectional shape should be readily achieved by one of ordinary skill in the art. The preferred geometry of the dense refractory ramming mix  73  cross-section shown in  FIG. 2  is designed so as to create an effective slag drip edge even after subjection to extended operation and wear. The cutting of small, appropriately positioned holes in the installed ramming mix mass will be necessary to facilitate passage of the bolts  51  and locking plugs  77  during attachment of the refractory laden apron to the quench ring hotface  47 . These holes should eventually be refilled with additional ramming mix after the apron is in position in the gasifier. The newly installed ramming mix mass  73  should then be dried as per the manufacturer&#39;s recommendations, although not in excess of the temperature. limits of the apron metallurgy. The apron should then be re-inverted to its normal, upright position so that the dense refractory bricks  49  should be of a key shape design so as to keep them locked in place during operations. The bricks reside on preferably two, but possibly more, circumferential ridges  58  protruding from the top surface of the apron floor  50 . This design limits the heat flow from the bricks  49  to the apron floor  50  metallurgy, thereby minimizing the risks of heat damage to the apron floor  50 . Refractory mortar is consequently not necessary on the bottom surface of the dense refractory ramming mix  73 . Refractory mortar should be applied to the top surface of the dense refractory bricks  49 , but only immediately prior to attachment of the apron to the quench ring hotface. Such last minute mortaring will facilitate bonding of the apron bricks  49  to the reaction chamber refractory floor  33  and eliminate any gaps therebetween. Installation of RCF  53  to the inner leading edge of the reaction chamber floor  46 , to the inner diameter surface of the quench ring hotface  47  and lip  52 , and between the outer diameter of the dense refractory brick  49  and the apron vertical, cylindrical side wall  48  should then proceed in final preparation for the attachment of the refractory lade apron to the quench ring hotface  47 .  
      The use of refractory brick and RCF adjacent to the quench ring hotface results in a temperature drop from about 1400° C. to about 350° C. from the constricted throat  27  to the quench ring hotface  47 . Without the use of refractory brick and RCF adjacent to the quench ring hotface  47 , the temperature of the exposed, unprotected quench ring hotface  47  can detrimentally exceed 800° C.  
      Referring to FIGS.  3 A-C, detailed views of the apron are depicted.  FIG. 3A  shows the possible placements of the refractory anchors underneath the apron floor. As shown in  FIG. 3A , the placement of the refractory anchors may be in any manner in which sufficient support is given to the apron floor.  FIG. 3B  shows the apron including a continuous anchoring lip, while  FIG. 3C  shows the apron having a discontinuous anchoring lip. The present invention uses either a continuous lip or a discontinuous lip. While the continuous lip is easier to fabricate, it does not provide as much insulation as the discontinuous lip.  
      In addition to the benefit of providing thermal protection to the quench ring, eliminating the problems of multiple small drip points that quickly wear away, and increasing the lifetime of the refractory at the reaction chamber bottom outlet, the apron also has the benefit of being independently removable from the quench ring, by removing the plugs and bolts. Removing the apron is highly beneficial for several reasons: (1) in the event that some of the refractory ceramic fiber located on, or under, the apron floor is prematurely damaged and needs to be replaced quickly; (2) in the event that the apron is prematurely damaged and needs to be replaced quickly; and (3) in the event that the dense refractory brick is damaged and needs to be replaced quickly. In addition to the stated reasons for quick replacement of the quench ring and associated hardware, other reasons may be encountered in which the quench ring and/or apron needs to be replaced without a excessive disruption of the operation of the gasifier. This feature of the apron is beneficial because the apron can be replaced quickly with a fully refractory-loaded spare apron at anytime without keeping the gasifier out of service for an excessive period of time.  
      It is understood that although modifications and variations of the invention can be made without departing from the spirit and scope thereof, only such limitations should be imposed as are indicated in the appended claims.