Abstract: Method and apparatus for reducing the viscosity of clogging hydrocarbons in an oil well. The apparatus is preferably trailer mounted for portability. It includes a tube type heat exchanger enabling heated gases to pass within feed water coils to heat the water to a predetermined temperature and at a pressure which prevents any flashing or phase change of the feed water within the heat exchanger. From the heat exchanger the heated feed water passes through a conduit which empties into the oil well. The well is open to atmosphere so that the feed water undergoes a phase change or flashing when it is introduced into the oil well. The resulting combined steam and hot water reduce the viscosity of the hydrocarbons sufficiently to facilitate their flow out of the oil well. One embodiment of the heat exchanger includes special coil arrangements to promote heating efficiency.

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: The water flow circuit for a heat recovery steam generator includes both a low pressure circuit and a high pressure circuit. Both circuits are designed for once-through flow and both include evaporators with rifled tubing. A pressure equalizing header may be located between the evaporator and superheater and orifices may be located at the inlet to the evaporator for flow stability.

Abstract: In a once-through steam generator, a separating bottle (25) is inserted between the evaporator (22) and the superheater (23). To purify the water/steam circuit, a greater quantity of water than is necessary is conveyed through the evaporator (22) via a feed pump (20). The water quantity is measured in such a way that wet steam enters the separating bottle (25). This water fraction, together with all the impurities contained therein, is separated in said bottle and is drawn off via a blowdown line (29). On the occasion of overfeeding, a conditioning agent is metered to the water, in order to reduce the volatility of the substances to be separated.

Abstract: A boiler having a discharge gas duct divided into a plurality of passages, respective passages having reheaters and superheaters therein. Gas flow controllers are provided for adjusting combustion gas flow through the respective passages. Evaporators are provided in the passages which have reheaters therein, the convective evaporators being downstream of the respective reheaters.

Abstract: A compact, unfired, staggered tube, once-through steam generator or boiler of simple construction intended primarily for combined cycle power plants in which the thermal energy utilized to generate steam is obtained from the exhaust gases of a gas turbine engine. The boiler provides steam at two different pressure levels, which maximizes recovery of thermal energy; and all wettable components in the steam/water loop are fabricated of corrosion resistant materials. This eliminates the need for controlling the pH of the feedwater and the need for chemically controlling its dissolved oxygen content, thereby reducing maintenance and operating costs and making automatic, unattended, remotely controlled operation of the boiler practical as well as eliminating the need for blowing down the boiler and minimizing requirements for make-up water. The boiler can be operated dry to remove gas side fouling; and feedwater flow rates can be directly controlled.

Abstract: The steam generator includes means for limiting the heat absorption of the economizer 28 during start-up and low load operation. An air bypass duct 54 is located to convey air from cold air duct 46 at a location between forced draft fan 44 and air heater 40 to the gas duct 38. The air is introduced upstream of economizer 28 where it mixes with hot flue gases to reduce the temperature of gas flowing through the economizer. Control dampers 56 are operated to maintain the desired temperature at the economizer outlet 30.

Abstract: At the start up of the forced-flow steam generator, water is supplied through a line into a radiation-heated superheater heating surface while the by-pass valve connected to the output line of the final superheater is closed. This produces a steam cushion or buffer which initially inhibits the formation of steam in the tube panel (evaporator). Subsequently, the by-pass valve is partly opened to produce a steam flow which cools the superheaters. When the pressure in the steam generator reaches the range of pressures corresponding to the starting pressure of the turbine, feeding of the steam generator with water is started. The heat consumed for starting is therefore reduced.