Cold-shot

Cold shot or hot shot. Injection of cold fresh feed for exothermic reactions or preheated feed for endothermic reactions to inter-... 

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. 

Nonisotnermal Operation Some degree of temperature control of a reaction may be necessary. Figures 23-1 and 23-2 show some of the ways that may be applicable to homogeneous liquids. More complex modes of temperature control employ internal surfaces, recycles, split flows, cold shots, and so on. Each of these, of course, requires an individual design effort. 

Exothermic processes, with cooling through heat transfer surfaces or cold shots. In use are sheU-and-tube reactors with smaU-diameter tubes, or towers with internal recirculation of gases, or multiple stages with intercoohng. Chlorination of methane and other hydrocarbons results in a mixture of products whose relative amounts... 

Cold shot. Injection of cold fresh feed for exothermic reactions or preheated feed for endothermic reactions to intermediate points in the reactor can be used to control the temperature in the reactor. Again, the heat integration characteristics are similar to adiabatic operation. The feed is a cold stream if it needs to be increased in temperature or vaporized and the product a hot stream if it needs to be decreased in temperature or condensed. If heat is provided to the cold shot or hot shot streams, these are additional cold streams. 

Multistage Operation with Cold-Shot Cooling... 

Figure 21.11 Flow diagram and notation for three-stage FBCR with cold-shot cooling...

Note that fAoi < /a,-i- That is, the mixing of fresh feed with the effluent from stage i - 1 results in a decrease in fA as well as in T. This is a major difference between cold-shot cooling and interstage cooling, in which /A does not change between stages. 

The operating lines for an FBCR with cold-shot cooling are shown schematically and graphically on a plot of /A versus T in Figure 21.12, which corresponds to Figure... 

Figure 21.12 Conversion-temperature diagram showing operating lines for cold-shot cooling operation of FBCR for exothermic, reversible reaction...

A number of factors may influence the choice of cold-shot cooling rather than interstage cooling in adiabatic operation of an FBCR. (Some of these are explored in... 

Figure 21.13 Interpretation of AT in equation 21.5-23 for exothermic, reversible reaction with cold-shot cooling, ith stage...

For an FBCR operated with cold-shot cooling for the reaction A products, determine, from the information given below,... 

In cold-shot-cooling operation of a multistage FBCR for the exothermic reaction A products, if cP (for the flowing stream) and (-A.Hra) are constant, show that the slopes of the operating lines (Figure 21.12) are all given by equation 21.5-8 (that is, they are all the same). 

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