Steady-state systems chemically-pumped

Chemically-Pumped Steady-State (Non-equilibrium) Systems. 

Consider how a chemical system responds to an influx of reactants supplied by pumping fresh reactant solutions into a stirred reactor and simultaneously removing an equal volume o reaction mixture. This type of open system is typical of the classical continuous-flow stirred tank reaaor or CSTR (see Figure 2) familiar to chemists and diemical engineers involved in commercial chemical processing. As the reactant flow rate is increased, the average time any species spends in the reactor (the residence time) decreases, and, because there is less time for the chemical reaction to occur, the composition of the reaction mixture becomes increasingly rich in reactants. The system relaxes to a particular steady state composition at each new value of the residence time. Thus, we anticipate a smooth transition from the product-rich steady state at... 

Steady-state procedures that require routine operator intervention can be either event- or time-based. Event-based procedures are usually performed in response to a system change or condition. For example, with regard to the cooling tower example, the facility may have event-based procedures to handle issues such as adding chemicals to the water, or controlling the temperature of the water. Time-based procedures are those that are to take place at a specified time interval. For example, the operator may have to catch a sample of the cooling water every 4 hours in order to check the chemical concentrations in the water. Many maintenance-related activities, such as checking the lube oil level in pumps, are time based. 

The reactor coolant inventory method is used to detect large volume leakage over a period of steady state operation by continuously monitoring the net makeup flow to the Reactor Coolant System (RCS). Since letdown flov/ and the reactor coolant pump seal bleedoff flow are collected by the Chemical and Volume Control System and recycled back into the RCS, net makeup flow should be zero when there is no leakage. Integrated net makeup flow is trended in the Control Room by the Nuplex 80+ Data Processing System (DPS). 

Crud Chemicals is producing a copolymer of Fj = 0.5 in a CSTR (Figure 11.4b). For their system, Vi = 2.0, V2 = 0.5. Things are going along fine until the feed pump for monomer 1 suddenly quits. It takes the maintenance people a couple of hours to get it back on line. Sketch qualitatively F/ and (F/) versus time for the period from immediately before the breakdown to the restoration of steady-state operation (well after the repair). 

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