Multistage flash system

From a hydrate melting standpoint it is possible in the winter time to have too cold a liquid temperature and thus plug the liquid outlet of the low temperature separator. It is easier for field personnel to understand and operate a line heater for hydrate control and a multistage flash or condensate stabilizer system to maximize liquids recovery. 

Multistage flash (MSF) processes, 21 650 Multistage flash desalination, 26 59 Multistage flash evaporation, 26 61-65, 97 energy required by, 26 86 in hybrid desalination systems, 26 95-96 schematic flow and temperature diagram of, 26 62... 

Desalination has been practiced for many years, although the early large-scale industrial applications were in the 1960s in the Middle-East using thermal desalination technologies such as multistage flash or multi-effect distillation. These plants used sophisticated thermal or vacuum systems to effectively distil a portion... 

The progress made in membrane-based desalination has lead to the substitution of evaporation plants with RO systems in different part of the world. For example, the United States holds the second position in worldwide desalination capacity (15.2% of the world production) and the 78% of their production come from RO treatments. Mediterranean countries, including Spain, Malta, Cyprus, and Israel, have also reverted from traditional multistage flash (MSF) to RO during the past two decades. The water production by reverse osmosis desalination plants passed from 36% of the global desalting capacity in 1996 to 42%... 

First applied for production of distilled water on board ships, flash and multistage flash evaporators have been more recently utilized to evaporate brackish and sea water as well as for process liquids. An aqueous solution is heated and introduced into a chamber which is kept at a pressure lower than the corresponding saturation pressure of the heated feed stream. Upon entering the chamber, a small portion of the heated water will immediately flash into vapor, which is then passed through an entrainment separator to remove any entrained liquid and condense the water vapor. A series of these chambers can be maintained at successively lower pressures with vapor flashing at each stage. Such a system is called a multistageflash evaporator. 

Figure 1 represents the general flow diagram of the multistage flash evaporation process and the solar heat collector system. The process conditions shown are typical for operation with a brine temperature of 140° F., as would be the case during May, June, and August. 

Once-Through Multistage Flash This system does not require acid addition and hot-end corrosion can be minimized with proper material selection and venting. Few pumps or controls are needed and frequent cleaning is not required with proper operation. 

Multistage Flash With Brine Recirculation More pumps and controls are needed. Two treatments are used for scale control acid and non-acid. Non-add systems require maintenance similar to once-through systems. Acid addition usually results in corrosion but better material of construction and proper operation can reduce corrosion related maintenance. 

Multistage Flash With Brine Recirculation These systems have economies of 3-12. Greater economy is possible, but more stages are required. The practical maximum number of stages is about 50 where economy is about 12. Low-pressure steam or hot water can be used. 

Fig. 3.16 shows a desalination cogeneration process designed for efficient recovery of the waste heat from a VH f R. Table 3.6 summarizes the design parameters of the process. A multistage flash (MSF) system is connected to the reactor plant cycle via... 

Yan, X., Noguchi, H., Sato, H., Tachibana, Y., Kunitomi, K., Hino, R., 2013. Study of an incrementally loaded multistage flash desalination system for optimum use of sensible waste heat from nuclear power plant. International Journal of Energy Research 37, 1811-1820. 

The conventional DBA and MDEA split-flow/flash amine systems operated at 900 psia. The circulating solutions were 30% DBA and 50% MDEA. Acid gas in both systems was released at 25 psia. The multistage membrane system consisted of an initial membrane bulk removal unit followed by a two-.stage permeation system with recycle. 

Multistep and multistage membrane systems of the type shown in Figure 21.5 have been used to treat a number of vapor-gas streams. However, hybrid processes in which membrane separation is combined with another separation process, are attractive because they may enable each unit operation to operate in its preferred range, improving overall process efficiency. The most important of these hybrid processes is the combination of condensation under pressure with membrane separation, illustrated in Figure 21.6. In this process, a vapor-permeable membrane unit is combined with a vapor condensation-flash unit (Baker and Wijmans, 1994 Baker et al., 1998 Wijmans, 1993/1992). 

The calculation of single-stage equilibrium separations in multicomponent systems is implemented by a series of FORTRAN IV subroutines described in Chapter 7. These treat bubble and dewpoint calculations, isothermal and adiabatic equilibrium flash vaporizations, and liquid-liquid equilibrium "flash" separations. The treatment of multistage separation operations, which involves many additional considerations, is not considered in this monograph. 

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