Abstract: In a water-tube boiler in which pollutant (especially NOx) emissions are reduced, a plurality of water tubes arranged in an annular shape are provided. At least some of the water tubes thereof are spaced apart along an annulus so as to provide a plurality of gaps therebetween. A combustion-reaction ongoing gas passes through these gaps, and a temperature thereof is lowered to 1400.degree. C. upon contact with the water tubes. The boiler further includes a second plurality of water tubes arranged in an annular shape outside of the first plurality of water tubes. By adjusting the arrangement of the water tubes along respective annuli and/or adjusting an orientation of the tubes along their length (so as to be straight, tilted, or bent), control of the exhaust emissions is enhanced.

Abstract: A package boiler having water cooled surfaces positioned relatively close to the combustion burner to improve the radiant heat transfer. Extended surfaces are added to the water cooled tube fireside surface to increase absorption rates to the limits established by water side conditions to avoid departure from nucleate boiling (DNB). The heat release rates of multiple firing rate zone burners are matched to the absorption rates of the water cooled surfaces by adjusting the size and extent of the various firing rate zones. The burner is extended or the physical shape is altered to expose a larger surface to greater areas of water cooled furnace surface. The burner is matched to cooling surface to lower combustion zone temperatures and thus thermal NO.sub.X formations. Further, recirculated flue gas, excess air, water vapor or a combination of these may be used to add mass to the fluid stream flowing through the burner. Finally, either the gas fuel or combustion air may be staged.

Abstract: The water flow circuit for a heat recovery steam generator is a hybrid system which combines a circulating drum type circuit and a once-through circuit. A low pressure evaporator is designed for natural or forced circulation and a high pressure evaporator is designed for once-through flow. Orifices may be located in the inlet of the evaporator tubes for flow stability and an intermediate header between the evaporator and high pressure superheater improves stability, minimizes orifice pressure drop and equalizes pressure losses between evaporator tubes.

Abstract: A buckstay system of an associated furnace having a combustion cavity with a front waterwall, a rear waterwall, and opposed left and right side waterwalls joining the front and rear waterwalls and where the waterwalls are arranged in a generally square pattern about the cavity. The cavity has four corners and each buckstay an attachment module welded to each end, each attachment module includes first and second planar plates. The first and second planar plates are disposed in side abutting relationship to the web of the buckstay and extend beyond the end of the buckstay, each of the first and second plates have coaxial pivot holes disposed in a part thereof that extends beyond the end of the buckstay. The planar plates in the attachment module may be rectangular. Or have a notch or recess for clearance.

Abstract: A water cooled panel (1), e.g. for metallurgical use, is constructed from a plurality of rectangular hollow section tube lengths (2), with adjacent tube lengths oriented corner-to-corner in a diamond array, with geometrical diagonals (4) of the tubes in a common plane (5), or generally so, and with means (6, 7, 12) to secure the tubes in such orientation, and with means (14-20) to ensure water flow communication between an end portion of one tube length (2) and an end portion of an adjacent tube length (2).

Abstract: An improved Cyclone furnace particularly suitable for retrofit applications to an existing boiler incorporates a Cyclone furnace and an integrated de-slagging chamber as a single manufactured piece. The Cyclone furnace and the de-slagging chamber are provided with a water cooling circuit which is separate from a water cooling circuit of the existing boiler to which it may be coupled, permitting the improved Cyclone furnace to be easily retrofitted to existing boilers or furnaces, even those not originally designed for Cyclone firing.

Abstract: An apparatus for reducing the concentration of nitrogen oxides in flue gases produced in a furnace of a combustion unit includes a device for maintaining combustion reactions in the furnace, the combustion reactions resulting in the production of hot gases containing nitrogen oxides, the hot gases flowing mainly upwardly within the furnace, internal heat transfer surfaces within the furnace for recovering heat from the mainly upward flow of hot gases, an introducer for introducing nitrogen oxides reducing agent into the upward flow of hot gases in the furnace, for reducing the concentration of nitrogen oxides in the hot gases, wherein the introducer is integrally connected to the internal heat transfer surfaces, for keeping the temperature of the reducing agent at a sufficiently low temperature level upon introduction thereof into the furnace, and for efficiently mixing the reducing agent with the upward flow of hot gases, and a discharge for discharging flue gases from the furnace.

Abstract: A continuous-flow steam generator includes a combustion chamber of rectangular cross-section and combustion-chamber walls each having essentially vertically disposed evaporator tubes through which a flow medium can flow from the bottom towards the top. The tubes are connected to one another in a gas-tight manner by tube webs. In order to equalize a differing supply of heat into the evaporator tubes, a heat-absorbing surface formed from an individual evaporator tube and from the tube web assigned to that tube is smaller in the case of evaporator tubes in a middle region of the combustion-chamber wall than at a corner of the combustion chamber.

Abstract: A once-through steam generator includes a gas flue formed of steam generator tubes welded to one another in a gas-tight manner through fins. The steam generator tubes are connected in parallel for the throughflow of a flow medium, they have a surface structure on their inside for generating a high flow turbulence in the medium flowing through them and they are disposed approximately in a spiral coil in a firing region of the gas flue. The steam generator tubes are constructed in such a way that, when they are in operation, the geodetic pressure loss of the medium flowing through them is at least 0.5 times their pressure loss due to friction. This ensures that such a once-through steam generator can also be operated in low load states of, for example, about 20% of the design load, without excessive thermal stresses occurring.

Abstract: The combustion chamber of a once-through steam generator is formed with walls of vertical tubes through which a flow medium flows from the bottom upwards. The tubes have a surface structure on their inner wall surfaces. Particularly favorable mass flow density m is established in the tubes at the load at which critical pressure prevails in the tubes according to the formula: ##EQU1## wherein q.sub.i is a heat flow density on an inner tube wall surface, T.sub.max is a maximum permissible material temperature of the tubes, T.sub.crit is a temperature of the flow medium at the critical pressure, .DELTA.T.sub.W is a temperature difference between the outer and inner wall surfaces of the tubes, and C is a constant.

Abstract: A once-through steam generator having single pass non-split fluid flow upper furnace circuitry with a one to one connection of tubes of the lower furnace spiral or vertical tube assembly being connected to the vertical tubes of the upper furnace assembly to prevent steam water separation and provide a fully drainable flow circuit.

Abstract: A once-through steam generator having single pass non-split fluid flow upper furnace circuitry with a one to one connection of tubes of the lower furnace spiral or vertical tube assembly being connected to the vertical tubes of the upper furnace assembly to prevent steam water separation and provide a fully drainable flow circuit.

Abstract: A buckstay system of an associated furnace having a combustion cavity with a front waterwall, a rear waterwall, and opposed left and right side waterwalls joining the front and rear waterwalls and where the waterwalls are arranged in a generally square pattern about the cavity. The cavity has four corners and each buckstay an attachment module welded to each end, each attachment module includes first and second planar plates. The first and second planar plates are disposed in side abutting relationship to the web of the buckstay and extend beyond the end of the buckstay, each of the first and second plates have coaxial pivot holes disposed in a part thereof that extends beyond the end of the buckstay. The planar plates in the attachment module my be rectangular. Or have a notch or recess for clearance.

Abstract: A refractory protective block protects heat exchange means connecting tubes to fins. The refractory protective block has an inside complementary shape corresponding to the surface shape of the heat exchange means and the refractory protective block is provided with recesses into which projections formed on the tubes are fitted and received. A pair of projections formed on the two adjacent tubes in the heat exchange means are arranged so as to confront each other. The refractory protective block has a high durability which does not break even when heat exchange means expand more than the refractory block at the time of the repetition of heating and cooling and which enable the dispersion of strain at the time of the repetition of expansion and contraction.

Abstract: An air nozzle assembly for use in associated combustion apparatus which includes a first elongated housing having first and second axial extremities. The first axial extremity thereof is open to the interior of the first housing and tapers axially from a larger to a smaller cross section that constitutes a generally flat nozzle at the first axial extremity. A second elongated housing has first and second axial extremities. The fist axial extremity is open to the interior of the second housing, at least the first axial extremity and an axial portion of the second elongated housing are dimensioned and configured to extend with at least the first axial portion disposed within the first elongated housing. The first axial portion tapers axially from a larger to a smaller cross section at the first axial extremity. The apparatus also includes means for selectively preventing flow in the second elongated housing.

Abstract: A small once-through boiler can avoid burning caused due to excessive heating of water pipes and burning around a fire hole of a burner in particular and heighten the heat load of a combustion chamber to further reduce the size of the system as compared with a prior art boiler. In the small once-through boiler, at least one regenerative burner system 20 is provided in a combustion chamber 1, the regenerative burner system 20 carrying out supply of combustion air A and exhaust of combustion gas E through a regenerator 22 and relatively changing flows of the combustion gas E and the combustion air A with respect to the regenerator 22 so as to supply the combustion air A via the regenerator 22 heated by heat of the combustion gas. Water pipe group 4 is provided apart from the combustion chamber wall surface 3 to form a passage 12 between the rear surface of the water pipe group 4 and the combustion chamber wall surface 3.

Abstract: A method and apparatus are provided for enhancing the efficiency of combustion in a combustion chamber with the use of acoustic energy. A means for generating acoustic energy (34) is located in relation to a combustion chamber (12) such that acoustic energy is transmitted into the combustion chamber (12) resulting in excitation of particulate and gases flowing therein and increased combustion efficiency. In the preferred embodiment, increased combustion efficiency is accomplished by operation of a horn (34) located at substantially the top of the combustion chamber (12) for generating acoustic energy into the chamber (12).

Abstract: In a cooling surface cladding for polygonal chambers of steam generators with a hopper-shaped floor and fired on the circulating fluidised bed principle, which consists partially of substantially vertical finned tubes extending in the manner of walls between manifolds and converging curves in the floor region to form a hopper, two opposite finned tube walls (1) in the hopper region, viewed from top to bottom, first form a hopper wall (1') inclined from the vertical over their entire width and then form at least one vertical hopper wall (1") of decreasing width and with partially oblique manifolds (2). In the region of the hopper, viewed from top to bottom, the adjacent tube wall (3) and the tube wall (3') opposite it form first a vertical hopper wall of diminishing width and with oblique manifolds (4) and then an inclined side wall (3") of the hopper of constantly reducing width.

Abstract: A once-through steam generator furnace having single pass non-split fluid flow circuitry to prevent steam-water separation with a one to one connection of smaller diameter tubes of the lower furnace spiral tube assembly being connected to the larger diameter vertical tubes of the upper furnace assembly through a reducing tube connecting spiral tubes angled to provide common centerlines with vertical tubes when the spiral tube centerlines are routed vertically.

Abstract: In once-through flow steam generators including a burner for fossil fuels and having a vertical gas flue with essentially vertically disposed tubes, inlet ends of the tubes are connected to an inlet header and outlet ends of the tubes are connected to an outlet header. According to the invention, a pressure-equalization tube branches off from each tube at the same height. The tube is connected to a pressure-equalization vessel. The height H is chosen in such a way that in the case of an individual tube being more strongly heated between the inlet header and the branching-off point of the pressure-equalization tube, the mass flow through the individual tube increases as compared to a mean value of the heating of all of the tubes.

Abstract: Pendant convection pass tube circuitry of once through steam generator have their floor and floor support tubes enlarged by a swage coupling and connected to enlarged sidewall tubes supported from steel boiler top supports to provide a more flexible circuitry operating at decreased temperatures and pressure losses.

Abstract: A once-through steam generator having single pass non-split fluid flow circuitry with a one to one connection of furnace hopper vertical tubes assembly being connected to the spiral tubes of the lower furnace assembly.

Abstract: A hybrid steam generating system and method in which fluid is passed through the waterwall tubes of a furnace to transfer heat from the furnace to the fluid to convert at least a portion of the fluid to steam. Under certain operating conditions, the heated fluid is passed from the furnace to a separator for separating the steam from the heated fluid and the separated heated fluid is passed from the separator back to the furnace. The steam from the separator is passed to a steam utilization unit, and, under certain operating conditions, the heated fluid is passed from the furnace directly to the steam utilization unit.

Abstract: A once-through steam generator has a vertical flue formed of tubes which are oriented vertically and which are connected in parallel for guiding a flow of flow medium therethrough. The tubes have a surface structure on an inner wall surface which causes flow turbulence and eddy currents in the flow medium. The surface structure includes first and second, mutually superimposed, contrary ribbings. The first ribbing encloses an acute angle with the tube axis, and the second ribbing extends parallel to the tube axis. The first ribbing forms an onflow flank angle with the tube wall which is flatter than a flow-off flank angle. Elevations of the ribbings rise at least 0.7 mm above the tube wall surface. A mass flow density of the medium in the tubes is adjusted as a function of the inner tube diameter, by maintaining the mass flow density below a predetermined limit curve.

Abstract: A steam generator is operated under both of supercritical pressure and subcritical pressure and has having generating tubes that form a furnace wall. Upper and lower generating tubes which are directed vertically and central generating tubes are inclined by 10.degree. to 35.degree. with respect to a vertical line. The steam generator further includes a burner wind box which is inclined along the inclination of the central generating tubes and are vertically divided into a plurality of stages.

Abstract: A ceramic tile is mounted to the wall of an incinerator or other high temperature and/or corrosive environment with a stud assembly that includes a threaded stud and a ceramic T-nut. The ceramic T-nut thermally shields the stud to protect it from oxidation and corrosion, and reduces cracking in tile because the T-nut and the tile have similar thermal expansion. The T-nut is accessible through a small bore.

Abstract: An arrangement for a furnace of a once-through steam generator includes a fluid mix header for holding a volume of a furnace mix fluid. A plurality of side wall tubes at the side wall of the furnace are connected to a side wall header. A roof outlet header is located at the roof of the furnace and a roof tube is connected at one end to the roof outlet header and at the opposite end to one end of a loop section of tube. A front wall tube located at the front end of the furnace is connected at one end to the opposited end of the loop section of the tube from the roof tube. A connection tube is connected between the roof outlet header and the fluid mix header. Rear and front screen tubes are connected directly to the fluid mix header of the furnace. Fluid from the fluid mix header is provided to the convection pass downcomer and convection pass tube enclosures of the steam generator.

Abstract: A once-through steam generator includes tubes together forming combustion chamber walls and carrying fossil fuel burners. The tubes are frequently provided on their inner surfaces with fins forming a multiple thread and are connected parallel to one another for conducting a coolant flow. According to the invention, the internal tube diameter is a function of a quotient, and points determined by pairs of values of the internal tube diameter and of the quotient lie in a coordinate system between a curve and a straight line. A summated mass throughput of all of the tubes at 100% steam output divided by the circumference of the gas flue in a horizontal section through the combustion chamber is used to form the quotient, and four defined points then lie on the curve which has a steady ascending slope. Application of this configuration is advantageously possible even for once-through steam generators having nominal outputs down to far below 500 MW.

Abstract: A steam generating system including an upright furnace section formed by a plurality of tubes, a portion of which have upper and lower tube ends and extend at an acute angle with respect to a horizontal plane, a portion of which extend vertically downwards from the lower tube ends, and a portion of which extend vertically upwards from the upper tube ends. Additional lower and upper vertical tubes are provided which are coplanar with, parallel to, and evenly distributed and interlaced among the tubes extending vertically from the respective lower and upper ends. Means is provided to pass fluid through the length of the furnace section to convert a portion of the fluid to steam or to heat the fluid, the fluid passing upwards first through the additional lower vertical tubes, then through the length of the angularly extending tubes including the vertical extensions thereof, and then through the additional upper vertical tubes.

Abstract: A buckstay system for a membraned-tube wall of a steam generator having a first wall section which meets a second wall section at an angle to form a corner. At least one buckstay extends across at least part of each wall section. A pair of tie bars are welded to each other at the corner, an end connection corner tie is welded at the corner to the pair of tie bars, and a pair of end connection buckstay brackets are welded to each end of the buckstays. A pair of pinned end connection links, an end connection corner tie and the end connection buckstay bracket transmit forces from one buckstay to the other wall's tiebar. Bending forces which tend to bend each wall section are transmitted to each respective buckstay which resists such forces.

Abstract: A refractory tile adapted for protecting boiler tubes from the corrosive and erosive effects of a hot gas stream comprises an elongated ceramic body covering only that side of a boiler tube upon which the hot gas impinges. The tile is hung on the tube with a threaded stud anchored on the tube and a nut threaded on the stud, urging the tile against the tube.

Abstract: A steam generator configuration, in particular of a low temperature carbonization-combustion plant, includes a supporting structure. A flue gas channel is disposed in the supporting structure and has a first vertical segment, a second at least approximately horizontal segment, and a third vertical segment being connected through the second segment to the first segment to form a structural unit. Supporting members suspend the first segment in the supporting structure in order to avoid restrictions to expansion and deformation of the flue gas channel as a result of thermal expansion. The supporting members are in an oblique or slanted position relative to the vertical in a cold condition. The oblique position essentially corresponds to a thermal expansion of the second horizontal segment in a hot condition. The supporting elements are parallel to the vertical in the hot condition.

Abstract: A method of supporting the spiral boiler tubing that surrounds a portion of the furnace or combustion area of a steam generator. This method of support eliminates the need to weld plate to the outside of the boiler tubing thereby increasing the mass of the boiler tubing which will result in the creation of temperature differentials within the spiral tubing. In accordance with this invention, a plurality of support members are inserted within and alongside the regular spiral tubing forming a part of the furnace enclosure. These support members are periodically removed from within the plane of this furnace enclosure and re-positioned to another (usually more elevated) position within the furnace enclosure. As the support members near the top of the spiral tubing (which is also the transition from the spiral tubing to more vertically aligned tubing), these support members are secured to this vertical tubing thereby transferring the loading of the spiral tubing to the vertical tubing.

Abstract: A gasifier for partially combusting a carbonaceous fuel mixture in the combustion chamber of the gasifier. The latter includes a water bath into which the hot effluent or products of combustion are immersed, including a synthetic gas. The products of combustion are directed into the bath by way of a constricted throat section. To avoid excessive erosion action and/or thermal shock to the throat section as a result of exposure to the effluent's high temperatures, the throat section is structured with an internal framework of pipes. The framework is communicated with a pressurized source of a cooling fluid, preferably water, whereby to cool the throat section sufficiently to counteract the ill effects of exposure to contact with the high temperature effluent.

Abstract: Surface temperature measurements of the tubes of operating power boilers are facilitated by using ganged and preferably scannable hollow-core sapphire probes to capture infrared radiation emanating from discrete tube surface areas. By selectively overlapping the tube surface areas scanned, the greater diameter of the scanning beam in relation to the tube diameter is compensated for and individual tubes can be assessed for surface temperature. Multiplexing the outputs of many probes to a remote signal processor which also controls the scanning regimens provides systematic automated temperature readings.

Abstract: A vertical tube, once-through, sliding pressure steam generator comprises a furnace having an outlet and heat exchanger surfaces made of smooth bore tubes, single-lead ribbed (SLR) tubes, and multiple-lead ribbed (MLR) tubes. All of these tubes are preferably constructed as membrane wall tube panels. The steam generator includes fuel burners for burning fuel and air within the housing, creating low, medium and high heat flux regions within the furnace. Fluid flows through the tubes of the wall panels to provide an efficient heat exchanger. The smooth bore tubes are located at the low heat flux regions, and the SLR and/or MLR tubes are located in the high and medium heat flux regions.

Abstract: Temperatures along the surfaces of water tubes in an operating steam boiler are determined by detecting infrared radiation emitted from the tube surfaces in one or more narrow pass-bands founds to be available despite the presence of hot and turbulent flue gases between the sensor and the tube surface to be measured.

Abstract: A fossil-fueled steam generator includes a vertical gas flue having a lower region being near a flame location, a region above the lower region being remote from the flame location, and an encompassing wall with tubes through which a medium can flow. The tubes are gas-tightly connected together in the lower region, and the tubes are disposed next to one another defining gaps between the tubes in the region above the lower region.

Abstract: It has now been found that these and other objects of the invention may be attained in a vapor generation apparatus which includes a tube wall and an elongated first horizontal buckstay disposed at a first elevation. The apparatus also includes coupling means coupling the first horizontal buckstay to the tube wall, an elongated second horizontal buckstay disposed at an elevation that is higher than the first elevation. The apparatus also includes means for coupling the second horizontal buckstay to the tube wall. A first elongated vertical buckstay member has first and second ends and also includes for securing one end of the first elongated vertical buckstay members to one of the horizontal buckstay members.

Abstract: A vapor generation apparatus which includes a furnace, having a tube wall and at least one vertical buckstay member disposed proximate to the outer face of the spiral tube wall. The apparatus includes a stirrup for transmitting forces between the spiral tube wall and the vertical buckstay member. The stirrup includes a U-shaped plate and a cylindrical member, apparatus for mounting the cylindrical member on the vertical buckstay member including first and second lugs fixed to the vertical buckstay member in spaced relationship. The cylindrical member is fixed between the first and second lugs in spaced relation to the vertical buckstay member. The apparatus also includes apparatus for mounting the U-shaped plate on the tube wall.

Abstract: A PFBC power plant with a combustor (3) enclosed within a pressure vessel (1). The combustor (3) is formed as a polygonal prism with, for example, hexagonal cross section. The bed section (3a) of the combustor (3) accomodates a steam generator constructed from at least three groups (23) of plane tube discs (24), in which groups (23) the discs are oriented parallel to opposite sides walls in the combustor (3). Each tube disc (24) may comprise both evaporation and superheater tubes (25a, 25b, 25c) which may comprise tubes in several parallel planes. In a preferred embodiment, each group (23) of tube discs (24) fills up a parallelepipedic space in the lower part (3a) of the combustor (3).

Abstract: A reactor (7) for gasifying materials that contain carbon under pressure has a tube wall (20) that has coolant flowing through it and is lined with a refractory material (21). The outlet (9) from the reactor (7) points down and opens into a cooler (10). The reactor is accommodated in a pressurized vessel (1) along with the cooler (10) and can be released and removed independently.

Abstract: A refractory tile adapted for protective fixation to the heat exchanger in an incinerator or furnace regardless of orientation. The tile includes a transverse groove which carries a shouldered slot to be guided by and mate securely with an anchor attached to the heat exchanger.

Abstract: An aerodynamically cleaned heat-exchanger is used in heating apparatus in which the radiant energy of a dirty fuel, such as coal or char, is efficiently recovered while the exposed heat-exchange components are protected from the deleterious combustion products.

Abstract: In a furnace wall heat-transfer pipe unit in a spiral wound-type boiler, for distributing gas-liquid double layer fluids from lower part spiral pipes to upper vertical pipes, a horizontal pipe is interposed between the spiral pipes and the vertical pipes and extends in a horizontal plane around the furnace wall. The gas-liquid double-layer fluids flow into the vertical pipes via the horizontal pipe extending around the furnace wall from the lower part spiral pipes. Uniform layers of the fluid flow into each vertical pipe so as to minimize an imbalance of fluid temperature at the outlet of the furnace.

Abstract: A fluidized bed combustion system in which a duct connects a reactor and a separator and extends within the furnace section of the reactor. The duct is wedge shaped, having an inlet width greater than its outlet width, and the bottom wall of the duct angles upwardly from the outer side wall of the duct. A portion of the duct extending within the furnace section is formed by cooling tubes which also form a portion of a side wall of the reactor, and a portion of the duct extending outside the furnace section is formed by cooling tubes which also form a portion of an outer wall of the separator. The portion of the duct extending within the furnace section is secured to the portion of the duct extending outside the furnace section to connect the reactor and separator without the use of expansion joints or seals.

Abstract: The invention relates to a process for starting up a heat exchanger system for the generation of steam accommodated in a hot gas line, in particular in an exhaust gas line, conveniently in a waste heat boiler, for instance downstream from a gas turbine, for instance for starting up a circulation system steam generator or a continuous flow (once-through) steam generator, conveniently a natural or forced circulation boiler or once-through boiler, in particular a preheater/evaporator/superheater system provided with a start-up heat exchanger upstream via which the supply of feed medium, in particular water or steam, is effected, and which on start-up dispenses first hot steam and finally water to the heat exchanger system, so that the initially pressureless, void heat exchanger system substantially heated to hot gas temperature is continuously brought to its operative state and its operating temperature, as well as a corresponding heat exchanger system.

Abstract: A fluid flow circuit for a boiler having a combustion chamber and an exhaust passage. In one embodiment there is provided at least one upflow evaporative generating bank module in the exhaust passage and at least one downflow evaporative generating bank module in the exhaust passage, positioned downstream of the upflow module. One or more upper downcomers are connected to a steam drum and supply water to the lower header of the upflow module and to the upper header of the downflow module. If needed, the convection pass wall enclosures can also be fed by the upper downcomers to their upper inlet headers. One or more lower downcomers may be connected to each lower header of the downflow module (and to the lower outlet headers of the convection pass wall enclosures) for supplying the water to a plurality of furnace circuits which extend along the combustion chamber in the boiler. The opposite end of each furnace circuit is connected to one or more risers which, in turn, are connected to the steam drum.

Abstract: A continuous-flow steam generator includes a vertical gas flue for connection to an outlet conduit of an apparatus emitting hot gas, such as a gas turbine. An evaporator heating surface in the vertical gas flue has an inlet header, an outlet header and tubes connected between the inlet and outlet headers. The tubes form an upper tube segment having an upper segment end and a lower segment end as well as a lower tube segment having an upper segment end and a lower segment end. The upper segment end of the upper tube segment merges with the upper segment end of the lower tube segment.

Abstract: Boiler tube studs of composite construction, particularly for protecting waterwall tubes in pulp mill recovery boilers. The studs include an inner solid cylindrical core of a material having thermal conductivity sufficient to provide proper heat transfer to the boiler tubes during operation, and an outer cylindrical sleeve of a material resistant to destructive conditions within a boiler during operation, such as chemical attack and abrasion. The sleeve surrounds the cylindrical surface of the core, but leaves an end surface of the core exposed. The core may be made of low carbon steel, and the sleeve of stainless steel. In order to avoid melting of the stainless steel sleeves when the studs are welded to the tubes, the cylindrical sleeves do not extend all the way to the attachment end such that axial gaps are defined where the sleeves do not cover the cylindrical surfaces of the cores.