Control drive, optimized

Control philosophies for clarifiers are based on the idea that the overflow is the most important performance criterion. Underflow density or suspended sohds content is a consideration, as is optimal use of flocculation and pH control reagents. Automated controls are of three basic types (I) control loops that optimize coagulant, flocculant, and pH control reagent additions (2) those that regulate underflow removal and (3) rake drive controls. Equahzation of the feed is provided in some installations, but the clarifier feed is usually not a controlled variable with respect to the clarifier operation. 

The tracking or servomechanism problem is defined in section 9.1.1(e), and is directed at applying a control u(t) to drive a plant so that the state vector t) follows a desired state trajectory r(t) in some optimal manner. 

Each resei voir generally has a dominant drive, an optimal pattern ofwell locations, and a maximum efficient rate of production (MER), which, if exceeded, would lead to an avoidable loss of ultimate oil recovery. Unfortunately, oil, gas, and water are not evenly distributed within the reservoir. With multiple leases above the reservoir, some lease owners will have more oil, gas, or water than will others, and coordination among competing firms in well placement and in controlling production rates is difficult. Efficient production of the reservoir suggests that some leases not be produced at all. Further, since each firm s production inflicts external costs on the other firms on the formation, some mechanism must be found to internalize those costs in production decisions. 

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