Stage absorption

Figure 11-15. Schematic diagram of two-stage absorption plant. (Used by permission Rescorla, C. L. Refrigerating Engineering, March 1953 now merged and used by permission American Society of Heating, Refrigerating, and Air-Conditioning Engineers, Inc. All rights reserved.)...

Representative Single-Stage Absorption Plant Operating Conditions... 

Absorption chillers may operate either a one or two stage absorption refrigeration cycle, using water as the refrigerant (typically inhibited by molybdate) and lithium bromide as the absorbent. Depending on design, heat exchangers may include ... 

X 10 and 1.6 X 10 cm /sec for steps 1 and 2, respectively). It is seen that the initial diffusion rate increases with concentration in the polymer (based on the initial slope of the curves), until, at higher concentrations, a two-stage absorption transient occurs. This behavior, which is typical of glassy polymers, is due to the fact that diffusion begins to become faster than die polymer relaxations [95]. 

Figure 4.10 Interval absorption of methanol in cellulose acetate measured using a TSM device. Each curve represents the transient response in going from an initial to a final (( ) volume fraction of methanol in the polymer. Fickian diffusion at low volume fractions turns into two-stage absorption at higher volume fractions. (Reprinted with permis-sion. See Ref. [100].)...

The following diagram shows a staged absorption column in which n-hexane (H) is absorbed from a gas into a heavy oil. 

Gommed, K., and Grossman, G. (1990) Performance Analysis of Staged Absorption Heat Pumps Water-Lithium Bromide Systems, ASHRAE Transactions, Vol. 96(1), pp. 1590 - 1598. 

The phase separation of certain mixtures may take place at economically impractical temperatures and pressures. An example of this type of separation might be the recovery of light hydrocarbon gases dispersed in air. In these situations, a second stream may be added to the mixture to shift the vapor-liquid equilibrium region. Such a process is equivalent to a single-stage absorption or stripping device. 

EXAMPLE 8.1 SINGLE-STAGE ABSORPTION AND STRIPPING OF PROPANE... 

The calculation results for a single-stage absorption are shown in Fig. 20.6. It is worth to note that at certain values of pressure and temperature, some components are desorbed from the liquid to the gaseous phase (this corresponds to negative values of me ). Thus, for condensate weathered at Tb = 20 °C and ps = 0.1 MPa, desorption is observed at T > 15 °C and p < 1.2 MPa. A reduction of Tb and an increase of ps results in desorption of heavy hydrocarbons at higher values of p and lower values of T. 

Single-stage absorption chiller Mechanical chiller Total installation cost... 

For low electricity costs ( 75% compared with the reference case). Cases IE and IG will be more attractive compared with the other cases. These cases are still attractive even with higher electricity cost (125% compared with the reference case), with a payback period of 0.88 years. As expected, a higher electricity price reduces the attractiveness of all cases. Waste LLP steam can be recovered economically from the steam condensate system. Alternatively, waste heat can be recovered as hot water from process streams. Petroleum refineries often discard a lot of waste heat through furnace stacks, fin-fan coolers and product coolers, which can be used to generate LLP steam (Reddy et al., 2013b). In such situations, where LLP steam is available at zero cost, a single-stage absorption chiller (Cases ID and IF) becomes feasible and attractive with a payback period of 0.93 years (Table 11.2). 

When the extent of conjugation in a polyenic molecule reaches a certain stage, absorption occurs in the visible range. Among the lipids this is the case... 

Figure 3-6 shows a schematic for a cocurrent two stage absorption unit. The loading diagram corresponds to the case of the leaving phases just reach equilibrium. (If phase equilibrium is not reached, which is usually the cas a curve must be used which takes into account the true exit loading of each stage A,, etc., instead... 

L. Kairouani, ENahdi. Thermodynamic Investigation of Two-Stage Absorption... 

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