Cooling flow fraction

For the purpose of the current calculations the cooling flow fractions were assumed to increase linearly with combustion temperature, from 0.05 at 1200 C. Thus, the following values of cooling fraction were assumed 0.05 at 1200°C 0.075 at 1400°C O.lOat 1600 C 0.125 at 1800°C 0.15 at 2000°C. 

These conclusions are broadly confirmed by real gas calculations for single step cooling with arbitrary assumptions for cooling flow fractions. 

In any particular cycle calculation, with the inlet gas temperature known together with the inlet coolant temperature Tcj, and with an assumed allowable metal temperature Tb), E() was determined from Eq. (A7). W" was then obtained from Eq. (A 18) and the cooling flow fraction i/ from Eq. (A16). 

In a particular blade row, for a given gas entry temperature Tgj, a cooling air entry temperature and an assumed allowable blade metal temperature Tbi, the blade cooling effectiveness eq is obtained. With ep = 0.4 and Pcooi = 0-7, then follows from Eq. (5.10). With C = 0.045 the cooling air flow fraction ip is obtained from Eq. (5.13). 

The results of calculations for the cooling air flow fractions in the first (nozzle guide vane) row of the turbine, ba.sed on the assumptions outlined in Section 5.2 for film cooled blading, are illustrated in Fig. 5.1. The entry gas temperature Tgi was taken as the combustion temperature Tcoi = Ty and the cooling air temperature as the compressor delivery temperature T2. The cooling air required is. shown here as a fraction of the exhaust gas flow, i.e. as ip/( 1 + ip), plotted against compressor pressure ratio and combustion temperature for an allowable blade metal temperature, Tpi = 800°C. Also shown are... 

Cracked gases are cooled and fractionated to remove fuel oil and water (2-5) then compressed (6), processed for acid-gas removal (8) and dried (9). The C3 and lighter material is separated as an overhead product in the depropanizer (10) and acetylene is hydrogenated in the acetylene converter (11). The acetylene converter effluent is processed in the demethanizer system (12-14) to separate the fuel gas and hydrogen products. The demethanizer bottoms is sent to the deethanizer (15) from which the overhead flows to the C2-splitter (16), which produces the polymer-grade ethylene product and the ethane stream, which is typically recycled to the furnaces as a feedstock. The deethanizer bottoms flows to the C3-splitter (18) where the polymer-grade propylene is recovered... 

The primary coolant circuit of a water-cooled reactor (including BWRs and PWRs) has several loops, including the main coolant loop, a core heat removal system, and a reactor water cleanup system. However, it is convenient, for computational purposes, to differentiate between the main loop, which has a high flow fraction, and the secondary loops, for which the flow fractions are small. The species concentrations and electrochemical potential (ECP) are solved for in the main loop and the values at the entrance to the secondary loop are used as the initial conditions for solving the system of equations for the secondary loops of interest. Mass balance is applied at each point where more than one section comes together. 

Lower block cooled by water FIGURE 13.19 Thermal field-flow fractionation. 

The bypass flow concept utilizes a fractional cooling flow ( 1% of total gas flow) in parallel with the hot leg gas. The bypass flow is supplied from the recuperator outlet and is discharged into the turbine outlet. The bypass flow concept was evaluated with and without internal insulation. The un-insulated option was not viable due to excessive cold gas temperature increase, as illustrated by the results of the counter flow thermal analysis presented above. In the un-insulated bypass flow configuration, this will cause the cold gas temperature to exceed the temperature limit of the piping material. In order to maintain an outer wall temperature of 900K in the insulated bypass flow concept, the insulation thickness must approach that of the internally insulated concept. The addition of insulation will significantly increase pressure drop due to a reduction in the area available for gas flow and will also increase manufacturing complexity. 

In such a plant the gas stream passes through a series of fractionating columns in which liquids are heated at the bottom and partly vaporised, and gases are cooled and condensed at the top of the column. Gas flows up the column and liquid flows down through the column, coming into close contact at trays in the column. Lighter components are stripped to the top and heavier products stripped to the bottom of the tower. 

Furthermore, 60—100 L (14—24 gal) oil, having sulfur content below 0.4 wt %, could be recovered per metric ton coal from pyrolysis at 427—517°C. The recovered oil was suitable as low sulfur fuel. Figure 15 is a flow sheet of the Rocky Flats pilot plant. Coal is fed from hoppers to a dilute-phase, fluid-bed preheater and transported to a pyrolysis dmm, where it is contacted by hot ceramic balls. Pyrolysis dmm effluent is passed over a trommel screen that permits char product to fall through. Product char is thereafter cooled and sent to storage. The ceramic balls are recycled and pyrolysis vapors are condensed and fractionated. 

Quench Converter. The quench converter (Fig. 7a) was the basis for the initial ICl low pressure methanol flow sheet. A portion of the mixed synthesis and recycle gas bypasses the loop interchanger, which provides the quench fractions for the iatermediate catalyst beds. The remaining feed gas is heated to the inlet temperature of the first bed. Because the beds are adiabatic, the feed gas temperature increases as the exothermic synthesis reactions proceed. The injection of quench gas between the beds serves to cool the reacting mixture and add more reactants prior to entering the next catalyst bed. Quench converters typically contain three to six catalyst beds with a gas distributor in between each bed for injecting the quench gas. A variety of gas mixing and distribution devices are employed which characterize the proprietary converter designs. 

In the Sulser-MWB process the naphthalene fractions produced by the crystallisation process are stored in tanks and fed alternately into the crystalliser. The crystalliser contains around 1100 cooling tubes of 25-mm diameter, through which the naphthalene fraction passes downward in turbulent flow and pardy crystallises out on the tube walls. The residual melt is recycled and pumped into a storage tank at the end of the crystallisation process. The crystals that have been deposited on the tube walls are then pardy melted for further purification. Following the removal of the drained Hquid, the purified naphthalene is melted. Four to six crystallisation stages are required to obtain refined naphthalene with a crystallisation point of 80°C, depending on the quaHty of the feedstock. The yield is typically between 88 and 94%, depending on the concentration of the feedstock fraction. 

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