Page 96 - Chemical Process Equipment - Selection and Design

68 DRIVERS FOR MOVING EQUIPMENT
Other inefficiencies are due to pressure drops of 2-5%, loss of economically marginal. Efficiencies are improved at higher pressure
1-3% of the enthalpy in the expander, and 1% or so loss of the air and temperature but at greater equipment cost.
for cooling the turbine blades. The greatest loss of energy is due to Inlet temperature to the expander is controlled by the amount
the necessarily high temperature of the exhaust gas from the of excess air. The air/fuel ratio to make 1700°F is in the range of
turbine, so that the overall efficiency becomes of the order of 20% 50 lb/lb. Metallurgical considerations usually limit the temperature
or so. Some improvements are effected with air preheating as on to this value. Special materials are available for temperatures up to
Figure 4.2(b) and with waste heat steam generators as in Example 2200°F but may be too expensive for process applications.
4.2. In many instances, however, boilers on 1000°F waste gas are

REFERENCES 4. R.T.C. Harman, Gas Turbine Engineering, Macmillan, New York, 1981.
5. E.E. Ludwig, Applied Process Design for Chemical and Process Plants,
1. M.P. Boyce, Gas Turbine Engineering Handbook, Gulf, Houston, 1982. Gulf, Houston, 1983, vol. 3.
2. F.L. Evans, Equipment Design Handbook for Refineries and Chemical 6. Marks’ Standard Handbook for Mechanical Engineers, McGraw-Hill, New
Plants, Gulf, Houston, 1979, vol. 1. York, 1987.
3. H. Gartmann, De Laval Engineering Handbook, McGraw-Hill, New
York, 1970.