Abstract: A heat recovery steam generator (HRSG) which contains multiple superheater and reheater tube units, each unit including an upper and lower header connected pressure-tightly together by a plurality of vertically-oriented tubes provided in alternate parallel banks, with the tubes of adjacent units being provided in an internested arrangement. Each superheater and reheater unit contains primary straight tubes and secondary bent tubes which are offset from the primary straight tubes in a direction perpendicular to the upper and lower headers and parallel to the direction of hot gas flowing transversely past the internested tubes. The ratio of the number of superheater tubes to reheater tubes in each row of tubes is provided in proportion to the desired heat transfer from the hot combustion gas to the superheated or reheated steam passing through the tubes in the generator assembly.

Abstract: A tubular type heat exchanger unit which utilizes upper inlet and outlet headers which are each series connected to at least three lower parallel headers by multiple elongated vertically-oriented tubes. The lower headers are connected together by a plurality of vertically-oriented U-shaped tubes provided in adjacent banks and rows within a thermally-insulated casing. The U-shaped tubes in each tube row are arranged in a staggered pattern relative to the tubes in the adjacent row. Preferably 4-12 lower headers each having a bank of 4-20 vertical tubes are provided. Such heat exchanger unit is enclosed within a thermally-insulated casing and is suitable for use as an economizer and superheater in heat recovery steam generators (HRSG).

Abstract: A control process and system for catalytic denitrification of NO.sub.x containing flue gases derived from a fuel combustion unit such as a gas turbine by ammonia addition to the flue gas upstream of a catalytic denitrification unit. The ammonia addition rate is controlled based on a basic signal which is generated based on functional parameters including the fuel being burned, its combustion temperature, flue gas flow rate, ammonia flow rate and the catalytic activity, so as to inject initially into the flue gas stream less ammonia than is theoretically required. Then the NO.sub.x concentration in the exhaust gas downstream of the catalytic unit is compared with the appropriate standard, the ammonia quantity initially being added is further adjusted until the NO.sub.x concentration is gas emitted to the atmopshere is reduced sufficiently to meet local clean air standards while avoiding unsatisfactory excess ammonia injection and system oscillation.

Abstract: A modular type heat recovery steam generator (HRSG) utilizes multiple pairs of parallel offset upper headers and into which at least two rows of vertically-oriented tubes are connected also to a lower header. The upper headers in each pair are offset from each other by a distance equal to the overall width of up to four rows of tubes, and the tubes connected to each header of the pair are located on opposite sides of the headers. Also, the adjacent end of each header pair overlap each other by a distance equal 0.5-2 times the spacing between adjacent tubes. The header arrangement and tube configuration of each module provides a generator assembly which is compact and facilitates fabrication and installation of the modular generator assembly.

Abstract: A device and method for augmenting support and suppressing vibration for U-bend tubes and tube spacer supports in a vapor generator vessel. The device is installed in the vapor generator vessel from outside the vessel through dual oppositely oriented openings cut through the wall and inner shroud of the generator vessel. The device extension rods are inserted through one of the openings, and the vibration suppressor blades are each inserted sequentially through the other opening and installed on a support rod and then rotated upwardly into place between the parallel tube batwing spacer supports by using a special push/twist tool, after which the support rod is indexed forward to provide positive engagement between the rod and blade, such as by a rod key and blade slot means. The suppressor blades are retained in place on the step block and rod by a clamp block attached to the step block, and the vessel dual openings are then covered by pressure-tight flange plates.

Abstract: A heat exchanger for exchanging the heat between separate fluids has a plurality of heat exchange tubes. These tubes are alternatively divisible into a primary plurality and into an alternative plurality of mutually exclusive subsets. Each one of the primary subsets shares in common with any one of the alternative subsets, one of the tubes. The heat exchanger also has first and second tube sheets each having a plurality of tube holes. Each of the heat exchange tubes are mounted between the first and second tube sheets. Each end of each tube is sealed into a corresponding one of the tube holes. The first and second tube sheets each have a plurality of internal, isolated passageways. Each of these passageways in the first and second tube sheets communicate with the surfaces of the tubes in a different associated one of the primary and alternative subsets, respectively.

Abstract: Water is flowed through bayonet tubes where it is heated to steam which is superheated in other bayonet tubes all the bayonet tubes extending from a single tube sheet. Heated water enters the inner tube of a bayonet tube assembly so that it is heated in the annulus between the inner tube and its associated outer tube and then flows into the annular space between the inner and outer tube of the second bayonet tube assembly so that it is is heated to steam to leave by the inner tube of the second bayonet tube assembly to then flow into the annular space between the inner and outer tubes of the third bayonet tube assembly to be superheated and leave the third bayonet assembly by the inner tube thereof, the flow between one or more of the bayonet tube assemblies being connected by connecting tubes which connect with thermal sleeves covering the inner tubes of the bayonet tube assemblies below the single tube sheet.