Steam sizing

The process requires (Qup + Qlp) to satisfy its enthalpy imbalance above the pinch. If there were no losses from the boiler, then fuel W would be converted to shaftwork W at 100 percent efficiency. However, the boiler losses Qloss reduce this to below 100 percent conversion. In practice, in addition to the boiler losses, there also can be significant losses from the steam distribution system. Figure 6.336 shows how the grand composite curve can be used to size steam turbine cycles. ... 

Sizing Steam Piping in New Plants Maximum Allowable Flow and Pressure Drop... 

In the United States the early decades of the new centuiy were dominated by ever-increasing size steam-turbine generators with capacities that reached over a thousand megawatts, and transmission voltages (the highest ones now often dc) above 700,000 volts. But after mid-centnrv these economies of... 

Example 2-19 Sizing Steam Condensate Return Line... 

Two of the units at the Oak Creek Power Plant have full-sized steam turbine driven boiler feed pumps, along with half-sized motor driven boiler feed pumps for use at low loads and unit startup. The boiler feed pump turbines are supplied with steam from a particular turbine "bleed-point". 

Conventional steam reforming is also restricted to applications in which the size of the locally available supply of hydrocarbon fuel is adequate. Much of the world s total natural gas resources are what is called "static gas," i.e., natural gas resources which are individually so small and so remotely located that they can not be economically pipelined to market. In theory this static gas could be reformed into synthesis gas which could then be made into readily shipped liquids. As discussed by Che and Bredehoft (1995), the minimum size for an economically viable steam reformer based on conventional technology is 5,000,000 standard cubic feet (scf) of hydrogen per day. To give such a minimum size steam reformer a 20-year useful life, the local natural gas resource would need to be relatively large. Studies of the economics of UMR indicate that the process will be satisfactory in small-scale applications. 

Figure 6.7 is a popular flowchart for determining steam flow rate, pipe size, steam pressure, or steam velocity in a given pipe. Using this chart, the designer can determine any one of the four variables listed above when the other three are known. In solving a problem on the chart in Fig. 6.7, use the steam-quantity lines to intersect pipe sizes and the steam-pressure lines to intersect steam velocities. Here are two typical applications of this chart. 

Table 6.7 shows typical steam velocities for various industrial and commercial applications. Use the given values as guides when sizing steam piping. 

Table 5.11 Summary of Equations for Sizing Steam Turbines...

When sizing steam turbines, Mohch [34] recommends a safety factor of... 

Sterilization specifications may be determined from theoretical considerations or from laboratory data and arewithin reason transferable from presentation to presentation, e.g., from 1 ml ampules to 5 ml vials to 50 ml bags. The sterilizer parameters required to deliver the sterilization specification to these presentations differ within the same autoclave and from one autoclave to another according to differences in load configurations, chamber size, steam entry points, control systems, etc. Sterilizer parameters are not transferable and must be developed empirically for each autoclave. 

Corella, J., et al, (2001) Testing commercial full-size steam reforming catalysts for tar elimination in biomass gasification at pilot scale. In this proceedings. 

Densified fuel pellets may be used as boiler fuel in place of coal in stoker-fired furnaces. Direct substitution of fuel pellets was demonstrated in two informally reported instances with no furnace adjustments. The particulate emission from each of these installations were monitored with the emission rate results shown in Figure 2. As a comparison, the North Carolina Administrative Code allowable particulate emission rate schedule (a function of heating rate) is also shown. The environmentally acceptable particulate emission contributes to the economic justification of the conversion of small-to-medium size steam generators to the use of pelleted biomass fuels. Two such installations are now using pelleted fuels on a routine basis, and a third has concluded the economic benefit by entering into a contract agreement to purchase pelleted fuel. 

Steam-pipe design problems are common in refineries, chemical processing plants, and power plants. Since steam is a compressible gas handled at high temperatures and pressures, fluid-flow calculations are somewhat more difficult to handle. This section will discuss methods of sizing steam pipelines. 

In order to compensate for these variations in operating conditions, the designer uses a capacity safety factor to increase the calculated condensate load. This safety factor should be selected with care. One short-cut method that should be avoided sizing steam traps to equal line size. This practice is never a substitute for analyzing process conditions it invariably leads to specification of the wrong size steam trap. 

Since for small- and medium-sized steam turbines with a power output up to approximately 700-800 MWei in particular of Japanese origin, a combined casing for both the HP and IP turbine stages can be found, for coal-flred power plants with a single unit output up to 1000-1100 MWei predominantly separate casings are utilized. For the H P turbine, almost aH turbine manufacturers apply a single-flow configuration. 

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