Temperature and Feed Rate

Therefore, the optimization of a semi-batch reactor, for selectivity reasons as well as for safety reasons, will often result in a reduction of the accumulation. Some hints to achieve this goal are given below. 

Figu re 7.10 Temperature course after a cooling failure at the instant of maximum accumulation with three different process temperatures 60, 90, and 120°C. 

For an irreversible second-order reaction, the optimization of the reaction temperature and feed rate can be performed by using the following equation [14]  

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Figure 4. Reaction progress plot for Crosslinker Preparation. Superimposed batch temperature and feed rates.

Initial and final temperature and feed rate are taken as parameters to be optimized, whereby the other variables are optimized in the same run. Temperature and feed rate between these two points are assumed to be straight lines connecting the initial and final values. The optimal values of variables obtained in the first step are taken as initial guesses for optimization. 

The thermal data of the reaction are summarized in Table 5.4. It should be noted that these criteria do not use any explicit kinetic data, but only the results of calorimetric experiments. For the decomposition reaction, by taking the activation energy into account, the safety limits of TD24 = 113 °C and Tm = 122 °C may be established, according to the assessment criteria presented in Section 3.3.3. The activation energy may be determined, for example, from DSC experiments, as described in Chapter 11. Without knowledge of the process conditions of temperature and feed rates, the assessment remains global, as shown in Table 5.4. More detailed assessment will be provided in the next chapters for different reactor types and process conditions. 

These different temperature and feed control strategies and their impact on reactor safety, together with general rules for assessing and improving process safety, are presented below. The choice of the reactor temperature and feed rate is also of primary importance for safety and this point will be discussed in the last section of this chapter. 

To realize these requirements the biomass feeding point was lowered a contraction ring was placed between the dense bed and the upper part of the combustor. These modifications significantly reduce the formation of CO under similar temperatures and feeding rate conditions without impact on NO formation (patent pending). 

To illustrate the concept of combining analytics to improve process understanding an example chemical reaction was run using a Cellular Process Chemistry Systems (CPC) continuous feed micro reactor. This microreactor is configured to operate as a small-scale chemical production plant. It has two reactant input lines and two solvent/wash lines. The thermally controlled microreactor block of the continuous feed reactor has a total internal volume of 50 pL. The reactor system contains active control for both temperature and feed rate of the two reactants. The system flows product from the microreactor block to a residence time module (12 mL volume) and then out of the reactor for product collection and work-up. 

Battery limits of scope of supply and exciusions from scope of supply to be made very clear by vendor. Maximum permissible speed, pressure, temperature, and feed rate shall be specified by vendors. (This can enable assessing capacity for future expansion also.)... 

Melt/Mix fixed screw profile. RPM range, barrel temperature, and feed rate w/in design space parameters. Screw speed designated CPP... 

Logic dictates that when corrosion occurs in a calciner, one should lower the temperature to determine if a satisfactory product can be obtained. This was done and corrosion became much worse. It was soon learned that the bed was much less corrosive to steel at higher temperatures where melt crystallized to crystals more quickly. When optimum temperatures and feed rates were determined, high-quality crystals could be made without causing harm to the calciner. This process was scaled up to pilot plant size and will be discussed in more detail in Chapter 7. 

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