Steam, properties

With a steam turbine, the turboeompressors ean be readily matehed to the different plant operating eonditions. Under eontinuous load, this type of installation is powered by the steam resulting from ammonia eombustion. Consequently, an outside steam supply is needed for startup. This may be a separate boiler or another external souree with live-steam properties not neeessarily eorresponding to those obtained from the nitrie aeid plant. The steam turbine must be of robust design beeause of the different pressure and temperature levels. 

The flashed steam method is less efficient and its requirements for steam properties—cleanliness, high temperature, and high pressure— are usually unavailable in most geothermal fields. The situation is different with the binary cycle system, which is quite efficient and widely used. This wet system involves the transfer of heat from the hot well stream into a more manageable boiling fluid to generate power through a turboexpander. 

Solution The conditions for the inlet steam are fixed, but the conditions of the outlet steam will depend on the performance of the turbine. First, estimate the steam flowrate from the process heating duty. A good approximation is that the sum of the heat content of the superheat and latent heat is constant from inlet to outlet. At the expander inlet, the heat content of the superheat is higher than that of the outlet, but the latent heat is lower in the inlet than in the outlet. The two trends tend to cancel each other out, with the total heat content of superheat and latent heat being approximately constant across the turbine. From steam properties, the enthalpy of the superheated steam HSup, enthalpy of the saturated steam HSat and enthalpy of the saturated condensate Hi at 100 barg are ... 

Next, determine the isentropic enthalpy change A His- From steam properties, the entropy of the inlet steam is ... 

Now, the parameters for the Willans Line Equations need to be calculated. From steam properties ... 

Now revise the steam flow. From steam properties at 20 barg, Hl = 920 kJ-kg-1 ... 

Determine steam properties from steam tables. What do you conclude about the heat available in the exhaust steam as the outlet pressure varies ... 

Table 23.13 Steam properties for the steam mains in Figure 23.57.

Steam Properties courtesy of the American Society of Mechanical Engineers)... 

Harvey, A.H., Peskin, A.P., and Klein, S.A., NIST/ASME Steam Properties, NIST Standard Reference Database 10, Version 2.2, National Institute of Standards and Technology, Gaithersburg, MD, 2000. 

Some constraints, such as < >2 use stream variables to describe the thermodynamic state of the working fluid. Numerical values for steam properties are generated using a computer subroutine called STEAM (14). Thus not all constraint equations are in analytical form. 

Residue Curve Maps for Reactive Mixtures 461 Heat-Exchanger Design 474 Materials of Construction 483 Saturated Steam Properties 487 Vapor Pressure of Some Hydrocarbons 489 Vapor Pressure of Some Organic Components 490 Conversion Factors to SI Units 491... 

E-mail Address info refiningonline.com Web Address www.refiningonline.com The Refining Connection, a service of Astron International, Inc., is an online refining resource that provides unite conversion tools, information on steam properties, line pressure drop calculators, Internet bulletins, a scientific calculator and various other software. 

Cost data for the purchase and installation of the insulation are available, and the length of service life can be estimated. Therefore, a relationship giving the effect of insulation thickness on fixed charges can be developed. Similarly, a relationship showing the cost of heat lost as a function of insulation thickness can be obtained from data on the value of steam, properties of the insulation, and heat-transfer considerations. All other costs, such as maintenance and plant expenses, can be assumed to be independent of the insulation thickness. 

Find the steam properties from the steam tables... 

While ASTM procedures for both steaming and MAT testing have been established (ASTM D-4463 and D-3907, respectively), a general survey of the petroleum industry indicates that neither of these methods are specifically practiced. Instead, each laboratory has developed individualized steaming and MAT testing procedures that best suit their needs. While many laboratories perform complete chemical and physical analyses on fresh FOC catalysts, the vast majority do not perform such analyses on the steamed catalysts. The latter actually represent the catalysts evaluated vhile the former are in essence a "precursor". While it may be argued that fresh properties can be used as an indicator of steamed properties, a thorough evaluation of catalysts should include an examination of the steamed chemical and physical properties. 

Figure 2 — This graph, along with the factor determined in Fig. 1, is used to relate electrical power to steam properties...

SOURCE Formulatioii of Wagner, Saul, and Pruss,/. Phys. Chem. Ref. Data, 23, 515 (1994), implemented in Harvey, Peskin, and Klein, NIST/ASME Steam Properties, NIST Standard Reference Database 10, Version 2.2, National Institute of Standards and Technology, Gaithersburg, Md., 2000. This source provides data down to 190 K (-83.15 °C). A formula extending to 110 K may be found in Murphy and Koop, (, J. R. Meteorol. Soc., 131,1539 (2005). 

Although the steam tables list steam properties against pressure and temperature, the fact that specific enthalpy and specific entropy are themselves thermodynamic variables means that it is possible to construe the steam tables as providing specific enthalpy as a tabular function of pressure and specific entropy. Alternatively, we may regard the tables as providing specific entropy as a tabular function of pressure and specific enthalpy. These two statements may be summarized mathematically by the two equations ... 

In practice, the tabulation of steam properties in steam tables is not normally fine enough for us to be able to read off accurate values using the basic method of inspecting the existing columns and rows described above. Excellent accuracy may be achieved by using interpolation, however. 

Steam properties in Equations (11.17) and (11.22) can be calculated using the Excel spreadsheet, freely available at http //www.x-eng.com. 

The property packages available in HYSYS allow you to predict properties of mixtures ranging from well defined light hydrocarbon systems to complex oil mixtures and highly nonideal (non-electrolyte) chemical systems. HYSYS provides enhanced equations of state (PR and PRSV) for rigorous treatment of hydrocarbon systems semiempirical and vapor pressure models for the heavier hydrocarbon systems steam correlations for accmate steam property predictions and activity coefficient models for chemical systems. All of these equations have their own inherent limitations and you are encouraged to become more familiar with the application of each equation. 

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