Intercooling and

Space needs to be provided for the auxiliaries, including the lube oil and seal systems, lube oil cooler, intercoolers, and pulsation dampeners. A control panel or console is usually provided as part of the local console. This panel contains instmments that provide the necessary information for start-up and shutdown, and should also include warning and trouble lights. Access must be provided for motor repair and ultimate replacement needs to be considered. If a steam turbine is used, a surface condenser is probably required with a vacuum system to increase the efficiency. AH these additional systems need to be considered in the layout and spacing. In addition, room for pulsation dampeners required between stages has to be included. Aftercoolers may also be required with knockout dmms. Reference 8 describes the requirements of compressor layouts and provides many useful piping hints. 

FIG. 23-3 Temperature and composition profiles, a) Oxidation of SOp with intercooling and two cold shots, (h) Phosgene from GO and Gfi, activated carbon in 2-in tubes, water cooled, (c) Gumene from benzene and propylene, phosphoric acid on < uartz, with four quench zones, 260°G. (d) Mild thermal cracking of a heavy oil in a tubular furnace, hack pressure of 250 psig and sever heat fluxes, Btu/(fr-h), T in °F. (e) Vertical ammonia svi,ithesizer at 300 atm, with five cold shots and an internal exchanger. (/) Vertical methanol svi,ithesizer at 300 atm, Gr O -ZnO catalyst, with six cold shots totaling 10 to 20 percent of the fresh feed. To convert psi to kPa, multiply by 6.895 atm to kPa, multiply by 101.3. 

The way to enhance the power output of a gas turbine can be achieved by intercooling and reheat. 

Intercooling and Reheat Effects. The net work of a gas turbine cycle is given by... 

Isothermal compression is presented here to represent the upper limits of cooling and horsepower savings. It is the equivalent of an infinite number of intercoolers and is not achievable in the practical types of compressors described in this book. For an isothermal process. 

Figures 5-9 and 5-10 depict the two most common forms of in-out arrangements. This arrangement is also referred to as a compound compressor. In these applications, the flow out of the compressor is taken through an intercooler and back to the compressor. The arrangement is not limited to cooling because some services use this arrangement to remove and scrub the gas stream at a particular pressure level. Provision for liquid removal must be made if one of the gas components reaches its saturation...

Fig. 1.10. Temperature-entropy diagram. showing reheat, intercooling and recuperation.

Fuller analyses of a/s cycles embracing intercooling and reheating were given in a comprehensive paper by Frost et al. [3], but the analysis is complex and is not reproduced here. 

Frutschi and Plancherel [11 not only described the basic EGT cycle, but also a modified version with an intercooler added. Macchi et al. [9] called this intercooled EGT the RWI plant and the simplest version is shown in the top part of Fig. 6.14. Macchi et al. also considered more complex versions (some with evaporative intercooling and aftercooling), the performance of which are discussed in Section 6.6. 

De Ruyck et al. [lOJ proposed another variation of the EGT cycle, in an attempt to reduce the exergy los.ses involved in water injection (the REVAP cycle). Rather than introducing the complication of a saturator, De Ruyck proposed several stages of water heating (in an economiser, an intercooler and an aftercooler). The efficiency claimed for this cycle is only a little less than the HAT cycle. 

In the second development, the emphasis is on taking advantage of the increa.sed specific work associated with evaporative intercooling and of the increased mass flow and work output of the turbine. Any gain on the dry efficiency is likely to be marginal, depending on the split in pressure ratio. 

To further understand the thermodynamic philosophy of the improvements on the EGT cycle we recall the cycle calculations of Chapter 3 for ordinary dry gas turbine cycles—including the simple cycle, the recuperated cycle and the intercooled and reheated cycles. 

For two stages of compression, what should be the pressures across the cylinders if the intercooler and piping pressure drop is 3 psi ... 

Assume the 3% pressure loss (1% due to entrance and exit losses plus 2% due to intercooler and piping losses). Suction pressure at second case ... 

Condensation occurs in all compressors, and the effects are most prominent where cooling takes place - in intercoolers and air-receivers, which therefore have to be drained at frequent intervals. Normally the amount of moisture present in a compression chamber is not sufficient to affect lubrication, but relatively large quantities can have a serious effect on the lubrication of a compressor. Very wet conditions are likely to occur when the atmosphere is excessively humid, compression pressures are high, or the compressor is being overcooled. 

The absorption process is exothermic. To improve C3+ recovery, liquid from one or more of the middle trays is pumped through an intercooler and returned to the tray below. In some FCC units, the lean oil feed is chilled. 

An ideal Brayton cycle is modified to incorporate multistage compression with intercooling, and multistage expansion with reheating. As a result of these modifications, does the efficiency increase ... 

Find the temperature of all states, power required by the compressors, power produced by turbine 1, which drives compressor 1, power produced by turbine 2, which drives compressor 2, power produced by power turbine 3, rate of heat supplied by the combustion chamber, rate of heat supplied by the reheater, rate of heat removed from the intercooler, and cycle efficiency. 

If an infinite number of intercoolers, compressors, reheaters, and turbines are added to a basic ideal Brayton cycle, the intercooling and multicompression processes approach an isothermal process. Similarly, the reheat and multiexpansion processes approach another isothermal process. This limiting Brayton cycle becomes an Ericsson cycle. 

A Braysson cycle (Fig. 4.32) uses air as the working fluid with 1 kg/sec mass flow rate through the cycle. In the Brayton cycle, air enters from the atmospheric source to a compressor at 20° C and 1 bar (state 1) and leaves at 8 bars (state 2) air enters an isobaric heater (combustion chamber) and leaves at 1100°C (state 3) air enters a high-pressure isentropic turbine and leaves at 1 bar (state 4). In the Ericsson cycle, air enters a low-pressure isentropic turbine and leaves at 0.04 bar (state 5) air enters a first-stage compressor and leaves at 0.2 bar (state 6) air enters an isobaric intercooler and leaves at 20°C (state 7) air enters a second-stage compressor and leaves at 1 bar (state 8) and air is discharged to the atmospheric sink. Assume all compressors have 85% efficiency. 

The Ericsson, Wicks, and ice cycles are modified Brayton cycles with many stages of intercooling and reheat. It has the same efficiency of the Carnot cycle operating between the same temperature limits. The Feher cycle is a cycle operating above the critical point of the working fluid. 

The second step is to develop several conceptual plants (e.g., cycles A, B, and C) to meet the identified need. One of the several plants is described in Example 5.14. In this example, a three-stage regenerative steam Rankine cycle and a four-stage intercool and four-stage reheat air Brayton cycle are combined to meet the need. 

Insisting on using three MFR s with r, between 0.1 and 20 s [see example 2, AIChE /, 40, 849 (1994)], with possible intercooling and a temperature range between 360 K and 396 K, the best scheme calculated by the computer is shown in Fig. P10.18. 

Instrumentation on the solvent extraction equipment will usually consist of recording flow and recording temperature controllers on the feed stream, a pressure controller on the raffinate exit line, temperature recorders on the column intercoolers, and a liquid level recording controller at the liquid-liquid interface to set the extract layer withdrawal rate. 

Atmospheric air at the rate of 6.1 million SCFD is compressed to 160 psig in a two-stage compressor JJ-1 that is provided with an intercooler and a knockout drum. Then it proceeds to a packed tower T-l where it is scrubbed with recirculating caustic soda solution. Overhead from T-l is cooled to 14°F in a refrigerated exchanger. After removal of the condensate, this stream proceeds to a dryer system that consists principally of two vessels F-l and F-2 packed with solid desiccant. 

Three-Stage Compression with Intercooling and Pressure Loss between Stages 164... 

Two-stage with intercooler Two-stage with intercooler and 1530... 

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