Regulatory Control Strategy

Step 1. We are assuming in this section that the product stream from the bottom of the stripper is set on the demand of a downstream user. The bottoms stream from the stripper is flow-controlled and so we set the position of the control valve, XMV(8), on this stream (B). The rest of the liquid level controls must be chosen to accommodate this first-priority choice. Note that we could put a flow controller on this stream if necessary, but this was not done in the simulations described later. The quality specification is that component G in the product should not vary more than 5 mol %. 

Step 2. This process has 12 degrees of freedom. One of these is agitation rate, which we simply hold constant. This leaves 11 degrees of freedom four fresh feeds F,A. F0d. FoE. and FcC, purge valve gas recycle valve separator base valve stripper base valve steam valve reactor cooling water valve and condenser cooling water valve. 

Step 3. The open-loop instability of the reactor acts somewhat like a constraint, since closed-loop control of reactor temperature is required. By design, the exothermic reactor heat is removed via cooling water in the reactor and product condenser. We choose to control reactor temperature with reactor cooling water flow because of its direct effect. There are no process-to-process heat exchangers and no heat integration in this process. Disturbances can then be rejected to the plant utility system via cooling water or steam. 

Step 4. Because of the objective to achieve on-demand production rate, the product stream leaving the stripper base is flow-controlled via the bottoms control valve. This is a good example of how a degree of freedom must be used to satisfy a design or business constraint. 

The purge stream is only 15.1 kmol/h, while the largest fresh feed makeup stream, F .c, is 417 kmol/h. The vapor holdup in the reactor. 

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Only after the total process mass balance has been satisfied can we check on the individual component balances in Step 7. That then settles the plantwide issues. We now apply our knowledge of unit operation control in Step 8 to improve performance and remain consistent with the plantwide requirements. Finally, Step 9 addresses higher level concerns above the base regulatory control strategy. 

Case 2 On-Supply Reactant 8.3,1 Regulatory control strategy... 

Figures 11.4 to 11.9 present some results of the rigorous dynamic simulation to various disturbances. Because of the model size, many-different variables could be plotted, but we have tried to include the key ones. Some of the dynamic behavior turns out to be not intuitively obvious. But the most important comment to make at the start is these results demonstrate that the control scheme developed with our design procedure works We have generated a simple, easily understood regulatory control strategy for this complex chemical process that holds the system at the desired operating conditions.

The main obstacles in implementing the optimal regulatory control strategy above are ... 

The development of analytical strategies for the regulatory control of dmg residues in food-producing animals has also been reviewed (128). Because of the complexity of biological matrices such as eggs (qv), milk, meat, and dmg feeds, weU-designed off-line or on-line sample treatment procedures are essential. 

Regulatory Control For most batch processes, the discrete logic reqmrements overshadow the continuous control requirements. For many batch processes, the continuous control can be provided by simple loops for flow, pressure, level, and temperature. However, very sophisticated advanced control techniques are occasionally apphed. As temperature control is especially critical in reactors, the simple feedback approach is replaced by model-based strategies that rival if not exceed the sophistication of advanced control loops in continuous plants. 

Presented as an overview of the State of Oregon s unique approach to particulate control strategy development, this review was prepared to provide those responsible for airshed management with new information on source impact assessment methods. (This material is available in the form of an audio-visual program suitable for presentation before public, regulatory or private Interest groups). 

Risk based regulatory scrutiny that relates to the level of scientific understanding of how formulation and manufacturing process factors affect product quality and performance and the capability of process control strategies to prevent or mitigate risk of producing a poor quality product. 

Economic Incentives for Automation Projects Industrial applications of advanced process control strategies such as MPC are motivated by the need for improvements regarding safety, product quality, environmental standards, and economic operation of the process. One view of the economics incentives for advanced automation techniques is illustrated in Fig. 8-41. Distributed control systems (DCS) are widely used for data acquisition and conventional singleloop (PID) control. The addition of advanced regulatory control systems such as selective controls, gain scheduling, and time-delay compensation can provide benefits for a modest incremental cost. But... 

From an operational and regulatory perspective, the challenge is to develop control strategies which are effective in the field, but which are also practical to implement. For example, from a knowledge of the fundamental chemical and physical mechanisms of PCDD/F formation and their relationships to the prevailing physical and chemical conditions, it is possible to identify through laboratory experiments key operational parameters or surrogate emissions... 

A plantwide control design procedure was used to develop a simple but effective regulatory control system for the Eastman process with an on-demand product control objective. With this strategy, control of production rate is essentially instantaneous. Drastic upsets and disturbances are handled by simple proportional-only overrides. 

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