Steam separators

After the waterwaH tubes deHver the saturated steam back into the top of the boHer dmm, moisture is separated out by a series ofbaffl.es, steam separators, and cormgated screens. The water removed drops down into the hot water contained in the steam dmm. The steam travels out through either a dry pipe, which leads to a superheater header, or a series of superheater tubes that connect directiy into the top of the steam dmm. The superheater tubes wind back into the top of the furnace and/or a hot flue-gas backpass section, next to the economizer, where heat from the combustion gases exiting the furnace superheats the steam traveling through the tubes. 

The pressure vessel is 79 ft high with an upper diameter of 23 ft and lower diameter of 20 ft. This height is key to establishing natural circulation core flow by providing a chimney in the space between the top of the core and the steam separator assembly. This large top diameter increases the water inventory above the core (no accumulators needed), and the smaller lower diameter reduces the volume of water needed to be replaced to provide core cooling. 

When the solution has all been added the toluene is distilled off in steam, separated from the water, and dehydrated over calcium chloride. It distils at 110°. Yields—6 grams. See p. 284. 

This relation is handled very similar to the flash steam separation. 

Instead, the flash vessel is primarily a flash steam separator. Its shape and dimensions are chosen to encourage separation of the considerable volume of low-pressure steam from the small volume of liquid. 

Condensate purification In some boiler systems the condensate returning is retreated using ion exchange to minimise corrosion and deposit accumulation. This particularly applies to once-through boilers (mainly nuclear) where there may be no water/steam separator and perhaps limited facilities for blow-down. Additionally, some high heat-flux boilers (oil-fired) have been fitted with condensate polishing plant (CPP). 

Steam from a field-erected boiler almost always contains significantly less entrained water than the preceding figures because of the greater sophistication of steam separation devices. However, some caution is required because even dry steam from an efficient HP boiler may contain volatilized salts (such as chlorides and silica) through the process of steam stripping. 

From here the water mixture rises through the water-wall tubes (generator tubes) that constitute the furnace membrane where steam is generated (primarily by radiant energy transfer). The steam-BW mixture is collected in top water-wall headers and conducted through risers (riser tubes) back to the top drum, where the saturated steam separates from the water at the steam-water interface. 

Coil boilers often use automatic, TDS-controlled solenoid valves to control BD. They are installed following the steam separator and steam trap. 

The BD pressure translates to a temperature of 365 °F (185 °C). At this pressure 15% will flash off into steam in the BD valve. The flash steam separates from the BD water in the flash vessel at a pressure of 3 psig (0.2 barg). 

Boiler operated with dirty steam separators or incorrect water levels... 

Primary steam separators These devices are located horizontally, immediately above the top drum waterline and use baffles or chevrons and dry pipe collectors, or cyclone or centrifugal action to radically change the steam flow, resulting in the heavier water and contaminants separating out from the steam. 

Water to the coil can be FW (FW definition = MU plus condensate) alone or a combination of FW and concentrated water from the steam separator drains. 

NOTE LP coil boilers with integral recycle are designed with the drain from the water-steam separator recycled within the boiler feed circuits. LP coil boilers with external recycle are designed with the drain from the water-steam separator either being dumped or recycled to the FW tank. 

Testing for steam quality measures the amount of entrained water in dry steam on a weight/weight basis. (Hence the effectiveness of steam separators and reduction in theoretical heat content can be identified.)... 

Steam drums (top drums) often are difficult to enter or move around in because of the fixed mechanical equipment contained within the confined space. It should not be assumed that this equipment has always been correctly reinstalled after any previous inspection or maintenance programs. Consequently, steam drums should first be inspected for proper location, orientation, and anchoring of steam separators, FW lines, baffles, continuous BD lines, and chemical injection lines. 

The development of an aerosol of microdroplets of BW into steam at the water/steam interface, caused by the sudden release of pressure under bubbles as the steam they contain is released. Typically, improved steam separation equipment is needed if misting persists in a boiler. 

Another instability mode of interest is due to the flow regime itself. For example, it is well known that the slug flow regime is periodic and that its occurrence in an adiabatic riser can drive a dynamic oscillation (Wallis and Hearsley, 1961). In a BWR system, one must guard against this type of instability in components such as steam separation standpipes. The design of the BWR steam separator complex is normally given a full-scale, out-of-core proof test to demonstrate that both static and dynamic performance are stable. 

The surface area of Additive R was 93 m /gm after the 1350 F steaming and 83 m /gm after the 1500 F steaming. This 11% loss in the surface area of Additive R caused a 23% loss in SOx activity (blend components steamed separately, then blended) ... 

Blend Components Blend Components Steamed Together Steamed Separately (Loss of Surface (Loss of Surface Area and Poisoning... 

For the case in which the blend components were steamed separately, there was no evidence of silica on the Additive R. 

On the other hand, a linear combination of 10% of an equilibrium boiling (single-step steam separation) and a Rayleigh distillation... 

Fig. 5. Variation of the Sl80 and 8D values of the fluid delivered from well 131, located 500 m away from the re-injection site, during an injection test conducted in the peripheral area of Serrazzano in the Larderello field (open squares). The figure also shows graphically, and in arbitrary units, the flow rate Q of water re-injected into the well as a function of time, and the position of each sample collected. Theoretical isotopic pattern of the steam produced by re-injected water, assuming continuous steam separation at depth, is also reported. Since the actual evaporation temperature and the fraction of residual water are unknown, calculations were made for three different temperatures (140, 160, and 180 °C) and fractions (/w) of residual liquid water after boiling. Dashed line represents the hypothetical mixing between deep geothermal steam (W) and completely evaporated re-injected water (R).

Nuclear Boiler Assembly. This assembly consists of the equipment and instrumentation necessary to produce, contain, and control the steam required by the turbine-generator. The principal components of the nuclear boiler are (1) reactor vessel and internals—reactor pressure vessel, jet pumps for reactor water circulation, steam separators and dryers, and core support structure (2) reactor water recirculation system—pumps, valves, and piping used in providing and controlling core flow (3) main steam lines—main steam safety and relief valves, piping, and pipe supports from reactor pressure vessel up to and including the isolation valves outside of the primary containment barrier (4) control rod drive system—control rods, control rod drive mechanisms and hydraulic system for insertion and withdrawal of the control rods and (5) nuclear fuel and in-core instrumentation,... 

Reactor Assembly. This assembly (Fig. 3) consists of the reactor vessel, its internal components of the core, shroud, top guide assembly, core plate assembly, steam separator and dryer assemblies and jet pumps. Also included in the reactor assembly are the control rods, control rod drive housings and the control rod drives. 

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