Pumps for liquids

The selection of pumps for liquids is discussed in Chapter 5. Descriptions of most of the types of pumps used in the chemical process industries are given in Volume 1, Chapter 8. Several textbooks and handbooks have also been published on this subject Garay (1997), Karassik (2001) and Parmley (2000). 

The flow rate enters into the evaluation of the results and should be accurately known and constant. This calls for an excellent flow meter (mass flow meter for gases) and pump (for liquids). 

Fuhr, G., Schnelle, T. and Wagner, B., 1994, Traveling Wave-driven miero- fabricated electrohydrodynamic pumps for liquids, J. Micromech. Microeng., Vol. 4, no. 4, pp. 217-226. 

In Fig. 4.6 a scheme of cooling circuit related to FCS for automotive application is shown. The main components are the pump for liquid circulation, the water reservoir and the heat exchanger with fan. For small size stacks (from 100 to 500 W) it is possible to use only air forced by fan to cool directly the stack, while for higher powers, more suitable for automotive requirements (1-100 kW), it is reasonable to use an internal coolant circuit fed by a liquid, such as de-ionised water or ethylene glycol-water mixtures, to improve the heat removing capacity of an order of magnitude with respect to the gas. 

Most common humidifier devices are used mainly for air hydration, but sometimes also for hydrogen humidification, and are based on bubblers, water evaporators, enthalpy wheels, membranes, or on a pump for liquid water injection inside a mixer or directly inside the first part of the cathode side collector. Membrane humidifiers or injection pumps have been prevalently proposed for hydrogen humidification. 

The compressor performs for gases the function carried out by a pump for liquids it adds energy to the gas to cause it to flow from one unit operation to the next. The pressure of the gas is raised in the process, so that the gas is compressed . The compressor consists of one or more sections, with each section containing one or more stages, which are sometimes referred to as wheels . (3as leaves the machine at the end... 

Figure 13.30 is a flow sheet showing the main process equipment of the Savannah River GS plant and the principal process conditions as given by Bebbington and Thayer [B7]. The plant consists of 24 units of type shown, operated in parallel. Not shown in the figure are the feed-water deaerator, the tower to recover H2S from purge gas, and pumps for liquid. 

Electric spring bellows metering pump for liquids and gases... 

Storage tanks, reactors, and separation units in a chemical process are operated at specified temperatures, pressures, and phase conditions. In continuous processes, pressure conditions are established by valves and pumps for liquids, and valves, compressors, and turbines or expanders for gases. Valves are also used to partially or completely convert liquids to gases. Temperature and phase conditions are established mainly by heat exchangers, which are the subject of this chapter. 

This chapter presents brief descriptions and some theoretical background of the most widely used pumps for liquids, and compressors and expanders for gases, all of which are modeled in simulators. Heuristics for the application of these devices during the synthesis of a chemical process are presented in Chapter 5. Further information on their selection and capital cost estimation is covered in Chapter 16. More comprehensive coverage of the many types of pumps, compressors, and expanders available is presented in Sandler and Luckiewicz (1987) and in Perry s Chemical Engineers Handbook (1997). After studying this chapter and the materials on pumps, compressors, and turbines on the multimedia CD-ROM that accompanies this book, the reader should be able to explain how the more common types of pumps, compressors, and expanders work and how a simulator computes their power input or output... 

One of the major advantages of the principle of MGD is the fact that it is possible to adjust the pressure difference across the membrane to obtain CO2 at a pressure higher than atmospheric pressure. Other advantages are, the absorption liquid can be circulated at constant pressure and this means that the setup will require a lower investment in terms of pumps for liquid compression and decompression to overcome the pressure changes, as compared to conventional absorption and desorption units. The use of a membrane contactor will allow for more flexible operation. For a gas-Uquid membrane contactor independence control of the gas and the liquid stream is possible. 

Because liquids and gases respond differently to an increase in pressure (a gas is compressed whereas a liquid is not) different units are used to distinguish this difference. A centrifugal pump for liquids may be represented as... 

Examples of actuators are rheostats to set and control electrical current, valves, flaps, and metering pumps for liquids. The actuator, which is most frequently encountered in chemical process engineering, is the diaphragm valve (Figure 12.29). 

Pressure may also need to be increased for the reactor (or, infrequently, decreased), and this requires a pump for liquids or a compressor for gases. When there is a choice, pumps are preferable to compressors, because the operating, capital, and maintenance costs are all lower for pumps. If pressure is reduced between the reactor and the separator sections (or anywhere else in the process), an expander can be considered (for gases), but often it is not economical both because of its high cost and also because it reduces the controllability of the process. A valve allows control at a modest cost, but energy is not recovered. 

The engine development problems (Figure 8) are closely related to the properties of the propellants, Ivlajor tasks are the development of 1) pumps for liquid fluorine... 

B. Feld and L. Szilard, A Magnetic Pump for Liquid Bismuth, USAEC Report CE-279, Argonnc National Laboratory, 1942. 

D.. . Watt,. 1 Study in Design of Traveling Field Electromagnetic Pumps for Liquid Metals, Report AERE-ED/R-1696, Great Britain Atomic Energy R( search Establishment, June 12, 1955. 

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