Tuning reactors

Following reconciliation of the equivalent reactor model is using real operating data to build preliminary models for real H P H CR reactors. We apply the reaction activities from the equivalent reactor model into the preliminary reactor models. It is necessary to fine-tune the preliminary reactor models. From the Aspen Simulation Workbook, we create a MS Excel spreadsheet (Figure 6.18) to make it feasible to simultaneously fine-tune reactor models of the two parallel series. In the HP HCR model, we only fine-tune HCR selectivity from 4.5 to 3.9 and the resulting model agrees with real operation and production well. The development equivalent reactor model reduces time and makes it achievable to develop the HP HCR model of two parallel reactor series. 

Basic process control system (BPCS) loops are needed to control operating parameters like reactor temperature and pressure. This involves monitoring and manipulation of process variables. The batch process, however, is discontinuous. This adds a new dimension to batch control because of frequent start-ups and shutdowns. During these transient states, control-tuning parameters such as controller gain may have to be adjusted for optimum dynamic response. 

In an HT system, either the star is not grounded or it is a delta-connected system and hence the third harmonic is mostly absent, while the content of the. second harmonic nuiy be too small to be of any significance. For this purpose, where harmonic analysis is not possible, or for a new installation where the content of harmonies is not known, it is common practice to use a series reactor of 6% of the reactive value of the capacitors installed. This will suppress most of the harmonics by making the circuit inductive, up to almost the fourth harmonic, as derived subsequently. Where, however, second harmonics are significant, the circuit may be tuned for just below the second harmonic. To arrive at a more accurate choice of filters, it is better to conduct a harmonic analysis of the system through a harmonic analyser and ascertain the actual harmonic quantities and their magnitudes present in the system, and provide a correct series or parallel filter-circuits for each harmonic. 

Refer to Table 23.1, which shows the average cumulative effect of all the harmonics that may be present in a power system. If we can provide a series reactor of 6% of the total kVAr of the capacitor banks connected on the system, most of the harmonics present in the. system can be suppressed. With this reactance, the system would be tuned to below the fifth harmonic (at 204 Hz) for a 50 Hz system as derived below. 

These types of reactors can now be used as current limiting reactors and also as harmonic suppressors. They are also recommended for capacitor application due to their linear characteristic which will not disturb the tuning of the filter circuit. 

Dilution rate is defined as the number of tank volume pass through per unit time, D = F/V. The residence time is defined as the tune required for one unit volume of reactor to be replaced by the flow rate, t = VIv. When feed is sterile, there is no cell entering the bioreactor, which means x0 = 0, the rate may be simplified and reduced to ... 

The neutral product is extracted from the bottom of the reactor by a volumetric pump and fed to an in-line postblender designed for double check and/ or buffer fine-tuning of pH and addition of other minor components such as buffers preservatives, etc. 

Figure 3. Example of Graphical Output from Analysis Mode. Reaction progress for water-jacketted reactor, with Cascade coupled temperature controllers, both in self-tuning mode.

An optimal model-based PID tuning method for the control of poly-butadiene latex reactor... 

Figure 1. Results of closed-loop operations (reactor A) (a) 9 batch without tuning, (b) 10 batch GA tuning...

First we tuned the simulation model using existing operation conditions. Product properties as well as conversion and temperature profile along the reactor axis closely coincided with the actual data after properly choosing the kinetic constants and other operation parameters. 

The scale-up from a small to a large plasma reactor system requires only linear extrapolations of power and gas flow rates. However, in practice, the change in reactor geometry may result in effects on plasma chemistry or physics that were unexpected, due to a lack of precise knowledge of the process. Fine tuning, or even coarse readjustment, is needed, and is mostly done empirically. 

The CEM Discover platform, introduced in 2001, offers a single-mode instrument based on the self-tuning circular waveguide technique (see Fig. 3.3). This concept allows for derivatization of the reactor to accommodate additional application-specific modules to address other common laboratory objectives. While the Discover ... 

Whereas in Gas Recycle the product must be removed at the same temperature and pressure at which it is formed, in Liquid Recycle the separation of product (and byproducts) from catalyst is independent of the conditions under which the products were formed. This added degree of control brings a variety of benefits. Since large gas flows are no longer required in the reactor, the liquid expansion due to gassing is reduced and more catalyst can be contained in a specific reaction vessel. Reactor temperature and reactant concentrations can be tuned for optimum catalyst performance. The conditions in the separation system can likewise be tuned for optimum performance. In particular, more severe conditions will permit better control over the concentration of heavies in the catalyst solution. 

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