Two tank level control

Conversely, composition is not affected by the absolute value of either flow, only by their ratio. Therefore, to make a change in composition, the AIC controller must adjust the ratio set point of the multiplier (FY). To minimize the interaction of the composition controller with the blend tank level control (through its manipulation of flow B), the smaller of the two streams should be controlled by level. 

Using the built in tank level controller with a set point of 50 per cent, increase and decrease the steam rate to the heater and record the tank temperature response. What is the dead time for the process shown in Figure W3.5 Is there a difference between the dead time predicted and the actual dead time from the simulation If the answer is yes, why is there a difference between the two values ... 

Liquid flows through a system of two tanks arranged in series, as shown below. The level control of tank 2 is based on the regulation of the inlet flow to the tank 1. This tank represents a considerable lag in the system. The aim of the controller is to maintain a constant level in tank 2, despite disturbances which occur in the flow F3. 

Figure 10-20 shows two tanks in series, both with independent level controllers. This configuration will result in the lower tank inevitably overflowing. Can you explain why ... 

Three vertical cylindrical tanka (10 feet high, 10 feet diameter) are used in a process. Two tanks are process tanks and are level controlled by manipulating outflows using proportional-only level controllers (PB 100). Level transmitter Spans are 10 feet. Control valves are linear, 50 percent open at the normal liquid rate of 1000 gpm, air-to-open, constant pressure drop. These two process tanks are 50 percent full at the normal liquid rale of 1000 gpm. 

J1. Two tOO-barrel tanks are available to use as surge volume to filter liquid flow rate disturbances in a petroleum refinery. Average throughput is 14,400 barrels per day. Should these tanks be piped up for parallel operation or for series operation Assume proportional-only level controllers. 

Here, a variable-speed pump transfers the hot water from the production well into the steam separator. The speed of the pump is set by the tank level. (Variable-speed pump station controls are discussed in Section 2.17). The level control signal is corrected for steam pressure variations by multiplying the two. This is called a two-element feedwater system. 

The proposed design is a two-CSTR system with minimum residence time per tank of 24 minutes. Each tank is supplied with 5% w/w (1.45 AO hydrated lime (Ca(OH)2> reagent controlled based on pH measured at the exit of the tank. Detailed tank design was such that a mixing delay of less than 10 seconds was expected. The neutralization tanks are followed by a flocculation tank with a minimum residence time of 10 minutes. There is an agitated level-controlled buffer tank upstream of the neutralization tanks, giving about 12 hours of concentration and flow equalization at maximum flow. The scheme to be evaluated is shown in Fig. 9. 

Liquid-level control Figure 13.2d and e show two feedback systems used for the control of the liquid levels at the bottom of a distillation column and its condenser accumulation tank. 

In this problem we see how to select the better manipulated variable among two alternatives. Consider the two noninteracting liquid storage tanks of system 1 shown in Figure PII.l. We can control liquid level h2 by manipulating F or F3. Assume that the cross-sectional areas of the two tanks are A i = 2 ft2 and = 5 ft2. Initially, the system is at steady state with F = 3 ft3/min and liquid levels h i = 3 ft and h2 = 6 ft. 

Let s take a look at the control loops. Now the make-up stream of reactant B is fed on level controller LCf of the buffer tank. The flow rate of the exit stream (Recycle) is set at a constant value by a simple specification on the stream s script. There are also two level controllers LCt and LCb for the top and bottom inventories of the distillation column, which manipulate the distillate and bottom products, respectively. Besides, the top column pressure is kept constant by means of the condenser duty. Quality control is implemented only for the bottom product, the reflux being fixed. We considered a composition measure with a first-order lag transmitted to a controller that manipulates the reboiler duty. 

---