Streams temperature trends

Fig-5 refers the BAHE-2 Gas/Liquid exchanger streams temperature trends. Most important point here hot stream (i.e. feed gas) outiet temperamre is almost constant —65degC even when hot inlet stream temperature is varying. This is mainly because 1. Cold stream-2 (i.e. side reboiler) is driven by thermosiphon hence self-adjusts the flow thorough exchanger as heat load varies. 2. Cold stream-1 (i.e. expander feed separator liquid) flow impacted due to loss of level in drum when feed gas C3+ content reduces. 

Figure 6.16 displays the temperature profile and liquid-phase molar fractions for cumene and DIPB. It may be observed that the temperature is practically constant over the reactive sections with a first plateau at 200 °C and a second one at 210 °C. The top temperature is at 198 °C while the bottom temperature climbs to 242 °C. The explanation may be found in the variation of concentrations for cumene and DIPB in the liquid phase. The maximum reaction rate takes place on the stages where propylene is injected. The cumene concentration increases rapidly and reaches a flat trend corresponding to the exhaustion of the propylene in liquid phase. It may be seen that the amount of DIPB increases considerably in the second reaction zone. This variation is very different from that with a cocurrent PFR. The above variations suggest that the productivity could be improved by providing several side-stream injections and/or optimizing the distribution of catalyst activity. 

The PBI-based PEM fuel cell can operate from 120°C to 200°C without external humidification. AC impedance shows that kinetics resistance decreases at higher temperatures, as shown in Figure 6.53, which is different from the characteristics of Nafion -based PEM fuel cells at high temperatures, but is consistent with the performance trend of the PBI-based PEM fuel cells, as shown in Figure 6.54. Although there is no humidification of the reactant streams in the operation of PBI PEM fuel cells, mass transfer issues are still observed through AC impedance, as shown in Figure 6.55. 

The presence of H2O in the feed stream during NO reduction with C3H8 caused kinetic inhibition of the main reactions as well as the apparent activation of solid state phenomena possibly associated to Cu migration. As a result, boA reversible and irreversible deactivation for NO and CsHg conversions were observed. Catalyst deactivation followed a nearly linear trend at short times on stream (t < 12 h), but after long times we observed an unexpected sharp increase in deactivation. The drop in activity was a function of both temperature and H2O concentration, and a low steady state conversion was finally reached. It appears that the main reason for the deactivation of Cu-ZSM-5 is the mobility of Cu + in the presence of H2O rather than ZSM-5 dealumination. 

A third emission reduction choice is to remain with the existing front end process, which continues to produce a sulfur dioxide-containing waste gas stream, and move to some system which can effectively remove the sulfur dioxide from this waste gas before it is discharged. Many methods are available, each with features which may make one more attractive than the others for the specific sulfur dioxide removal requirements (Table 3.8). Some of the selection factors to be considered are the waste gas volumes and sulfur dioxide concentrations which have to be treated and the degree of sulfur dioxide removal required. It should be remembered that the trend is toward a continued decrease in allowable discharges. The type of sulfur dioxide capture product which is produced by the process and the overall cost are also factors. Any by-product credit which may be available to offset process costs could also influence the decision. Finally, the type of treated gas discharge required for the operation (i.e., warm or ambient temperature, moist or dry, etc.), also has to be taken into account. Chemical details of the processes of Table 3.8 are outlined below. 

The trends of methane conversion with time on stream (t.o.s.) on differently loaded Ni-TLC catalysts at 773, 823 and 873K are shown in Fig. 4. Regardless of the reaction conditions, the catalysts undergo activity decay with a rate depending upon the reaction temperature and Ni loading. In particular, as Tr... 

As before, the disturbances seen at flash inlet are available from the steady state simulation. Control of level, temperature and pressure is excellent. No input saturation occurs. Trends of interest are the amounts of benzene in the vapour stream and methane in the liquid stream. They follow the increase or decrease in plant throughput almost proportionally. 

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