Document XzOm3LBg0ver9Vj43d2geJBbd

2Steom from the duol-elrcufoHon boilers enters new 1250-psl heoder for dis tribution to the refinery and to the topping unit! for byproduct power makeup for the boilers. Several of our refineries successfully use raw Lake Michigan, Mississippi or Missouri wa ter as boiler feed at pressures up to 600 psi. Enough of it serves as cooling water for process units to make it at tractive to (1) return it to the power plant after process use at 120 to 180 F f2) treat H chemically lor boiler feed. A recent wartime expansion of our 400-psi steam-generating capacity to 1,000.000 lb per hr required a feedwater-treatment system upon which we drew for our high-pressure planning. That system reduces boiler feed to the lowest hardness possible from use of a 2-stago hot-process treatment--a limesoda stsga supplemented by phosphate treatment in an external sedimentation tank with filtration and deaeration. In addition to our own water-treat ment system we reviewed the experi ence of several operating high-pressure boilers (1200-1500 psi) with 10095 makeup. These employed zeolite coldwater treatment. Installations equipped with ordinary hot-process treatment fell in the 900-psi range. Silica Trouble!. Certain of the highmakeup 1200-psi plants under study re ported silica troubles in turbines. In fact, many plants with small makeup indicated a growing awareness of the silica problem in boiler water. Since a large portion of the steam supplied from the high-pressure topping unit normally would go throughout the refinery to steam turbines driv ing pumps, blowers and fens at throt tle pressures of 400 and 100 psi, silica troubles were of major Interest. Pres sures and temperatures in this range form the region where silica deposits are most likely to occur. Their con trol was a prime consideration. The National Alumlnate Corp ex pressed the belief that a 1500-psl boiler could operate successfully with 100% makeup from Lake Michigan water treated in a hot-process softener. They conducted experiments on a pilot boiler* to determine nature of boiler scale at thii pressure with water treated as we had at Whiting. These experi ments indicated safe operation. An investigation on a commercial scale by this same company showed that dolomitic lime and magnesium ox ide added to a hot-process time-soda softener gave water of less than 1-ppm silica leaving the softener. Slight Im provements in design, plus sludge re circulation under close control, reduce silica content still further below 1 ppm. Ploni Dotign. With this background of economic and operating studies 4 antrteiacui fffcrftc* tf trOtt OnU mi by J A fbtOM ud c fMfeUa. It (IS*) Stone & Webster Engineering were called in to design a iisiIoq' ploying topping turbines to op< -Kw H-P 1250 psi, 900 F at the throttle, fh prime requisites influenced design l\\ the least over-alt cost possible forst^ and power (2) continuous service^' dependability. fas Turbine Foster Wheeler Corp designed circulation boilers, p 85, for operati0| at high pressure Incorponting requisites. They can fire puWtriid Under Way in coal, oil or gas. A conservative heal ^ lease, 13,700 Btu per hr per cu ft, for flexible operation both from fue] ^ and high makeup considerations. Switzerland Under operating conditions Whiting--feedwater with total soluble! solids of 150 ppm. 1 ppm siUct; boiler water of 10 pH; a steam ol p&fscrw to D< flEAOr lor service in 0.1% moisture--the problem of iHfe/ mofitattof 19M-50. a 20,000-kw high- reaching refinery equipment at the 400-1 wfjircaare gas-turbine plant is under con- and 100-psi lovel does not appear too! IfcjriSion at Sober Bros, Wintberthur, serious with these dual-circulation boil-^ lEitffthe Nordeetecbweiserlsche Kraft- era supplying steam- Moreover, [flCserSe A G. It* output will supplement down losses ere much reduced cam- `tk'Swiu hydro system during the cold- pared to a conventional boiler. Recommended Levels. For a coa-' wither months. model shows general arrange- ventlonal boiler operating at 1000 i Foot of equipment In a building about 1500 psi an 18% blowdown bringi UI12i79 ft. Operating on the h-p cycle boiler-water concentration to the 1000- -Mibb, turbine-throttle temperatures of ppm level recommended by the Ameri Befoul 1200 F, efficiency Is expected to can Boiler Manufacturers Association. *Kmteed 30% on heavy fuel oil. Solids carryover with the steam nmi J*v'Stfld-ltisd Crete. The h-p or semi- about 1 ppm. Under these conditions,'' ml' dimd cycle fs believed particularly avoiding silica deposits requires keep k;soiied. to plants of large output as the ing total silica concentration in the 'itUth density of working fluid resulting boiler water below 5 ppm; the pH a..froin pressurised operation permits about 11.0; the silica content of Iht .gl ^iaiUer machinery and piping. As steam below 0.1 ppm. , Ml ) ^ihown In 'the diagram (a modification A comparison of these (actors vefj the design described in Power, tween the standard and the dual-dreo- 1946. p 74, and Oct 1946, pp 84- lation boiler shows how well the dutljjm a doted cycle handles clean air unit meets this problem. The dutl^j ^nly. This consists of a 2-cylinder Inter- circulation boiler has two aepsrUi|fl ^.cooled compressor driven by an air tur- circulating systems, p 85, one In thacoa- Hbfas, t regenerator and a recooler, vectlon orea, and the other in (he rtdiant All steam entering the 1250-ptl`jffl 3*Jdch restores the circulating air to temperature conditions. Air header comes from the primary or* Hvifaa this cycle supports combustion in radiant tone. At the 18% blowdown, fl&Sjfater, which raises closed-cycle air secondary section shows boiler-wtter concentration as 1000 ppm, silica con-ij C;i??perature indirectly ond supplies tent 6.7 ppm. The primary section--jfll ^{j^wobutiion products to two gas tur- one driving the compressor the one supplying steam to the otin-| ^{tapping (resh air into the closed cycle' shows boiler-water concentration 3$2jj other driving a generator to ppm, silica content 2.36 ppm, tots! nielul output. Cas turbines art solids carryover 0.35, and silica io with a reheater between, steam 0.024 ppm. air-heater and combustion-cham- A further precaution against solid* Combination, in which fuel is carryover comes from the unusually ,'d1in the working medium, oper- large steam-collecting drum, radiant *ith equal pressure insido and section In Fig. 2. Drum Internals wet* the tubes, which eliminates subjected to tests by the manufacturer t 'n ,u^e mel*I working at high on a full-sized cross-sectional element ^-ur. High pressure on tho gas of the drum. , More details of plant layout 1 operation follow in a second article. *ncrn#c# specific-heat transfer. n* e^Tccl is a considerable saving j*,ir-heatr space requirements. POWER Man* ^VER . Match IMS r'