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Manipulation of the cooling-water

A similar equation could be applied to the manipulation of the cooling water flow. [Pg.520]

An exothermic reaction involving two reactants is run in a semi-continuous reactor. The heat evolution can be controlled by varying the feed rate of one component This is done via feedback control with reactor temperature measurement used to manipulate the feed rate. The reactor is cooled by a water jacket, for which the heat transfer area varies with volume. Additional control could involve the manipulation of the cooling-water flow rate. [Pg.430]

The components of the basic feedback control loop, combining the process and the controller can be best understood using a generalised block diagram (Fig. 2.29). The information on the measured variable, temperature, taken from the system is used to manipulate the flow rate of the cooling water in order to keep the temperature at the desired constant value, or setpoint. This is illustrated by the simulation example TEMPCONT, Sec. 5.7.1. [Pg.96]

These three nonlinear ordinary differential equations will be used to simulate the dynamic performance of the CSTR. The openloop behavior applies when no controllers are used. In this case the flowrate of the cooling water is held constant. With closedloop behavior, a temperature controller is installed that manipulates cooling water flow to maintain reactor temperature. [Pg.109]

The reactor is the jacket-cooled CSTR with an irreversible, exothermic, liquid-phase reaction A —> B, which was considered in Section 3.1. In that section the flowrate of the cooling water Fj to the jacket was the manipulated variable for the reactor temperature controller (TR <— Fj control). In this section we explore the use of the flowrate of the fresh feed F() to control reactor temperature (TR <— F0 control). [Pg.154]

Dynamic Heat Transfer Option Figure 3.99 shows the parameters that must be specified when this heat transfer option is selected. The manipulated variable with this option is the flowrate of the cooling water. The temperature of the inlet cooling water is... [Pg.189]

An alternative arrangement, used especially when the condenser is built into the head of the column, is that of Figure 3.15. Direct measurement and control of reflux are not possible since the flow is internal. Instead it must be controlled indirectly by manipulation of condenser cooling water, which, in turn, may be reset by a vapor-composition controller. This internal reflux arrangement works well if a heat-computation scheme is used for control. A scheme that we have used successfully is discussed in Chapter 11, Section 4. [Pg.85]

Add 15 g, of chloroacetic acid to 300 ml. of aqueous ammonia solution d, o-88o) contained in a 750 ml. conical flask. (The manipulation of the concentrated ammonia should preferably be carried out in a fume-cupboard, and great care taken to avoid ammonia fumes.) Cork the flask loosely and set aside overnight at room temperature. Now concentrate the solution to about 30 ml. by distillation under reduced pressure. For this purpose, place the solution in a suitable distilling-flask with some fragments of unglazed porcelain, fit a capillary tube to the neck of the flask, and connect the flask through a water-condenser and receiver to a water-pump then heat the flask carefully on a water-bath. Make the concentrated solution up to 40 ml. by the addition of water, filter, and then add 250 ml. of methanol. Cool the solution in ice-water, stir well, and set aside for ca. I hour, when the precipitation of the glycine will be complete. [Pg.130]

With the moderate activation energy (69.71 x 106 J/kmol) used in the study, the temperature dependence of the reaction is not excessive. As we observed above, the reactor could be controlled by manipulating jacket cooling water. However, if the activation energy is high, the temperature dependence is increased, and it may be difficult or impossible to control reactor temperature by manipulating the flowrate of jacket cooling water. [Pg.142]

There are two controllers. The proportional reactor level control has a gain of 5. The reactor temperature controller is tuned by running a relay-feedback test. The manipulated variable is the cooling water flowrate in the condenser. With a 50-K temperature transmitter span and the cooling water control valve half open at design conditions, the resulting tuning constants are Kc = 4.23 and = 25 min. [Pg.150]

The performance of the convention control structure, in which cooling water flow is manipulated to control temperature, is shown in Figure 3.52. The disturbance is the same increase in cooling water temperature. Feed flowrate is constant. The cooling water flowrate more than doubles to control reactor temperature, but the temperature is returned to the desired value in about 2 h. The peak deviation in temperature is less than 0.6 K. Controller settings are those given in Table 3.2 for the 95% conversion case with a 330 K reactor temperature (the integral time is 50 min). [Pg.159]

The control structure shown in Figure 6.57 is installed on the flowsheet. The feed is flow-controlled. The outlet temperature is controlled by manipulating the coolant flowrate. Note that the OP signal is sent to both of the control valves on the coolant stream, opening and closing them simultaneously. The setup works in the simulations, but it is not what would be used in a real physical system. A pressure-driven simulation in Aspen Plus requires that valves be placed on both the inlet and outlet coolant streams. In a real system, the cooling water would be drawn from a supply header, which operates a fixed pressure. A single control valve would be used, either on the inlet or on the outlet, to manipulate the flowrate of coolant. [Pg.333]

In a liquid-liquid exchanger, the total heat transferred (Q) from the hot process fluid to the cooling water is dependent on the overall heat transfer coefficient (U), the heat transfer area (A), and the log mean temperature difference (ATm). Therefore, any of these can be manipulated to control Q. [Pg.278]

In cascade control, we therefore have two control loops using two different measurements but sharing a common manipulated variable. The loop that measures the controlled variable (in the example, the reacting mixture temperature) is the dominant, or primary control loop (also referred to as the master loop) and uses a set point supplied by the operator, while the loop that measures the second variable (in the example, the cooling water temperature) is called the secondary (or slave) loop and uses the output from the primary controller as its set point. Cascade control is very common in chemical processes and the major benefit to be gained is that disturbances arising within the secondary loop are corrected by the secondary controller before they can affect the value of the primary controlled output. [Pg.266]

In most cases the catalytically active metal complex moiety is attached to a polymer carrying tertiary phosphine units. Such phosphinated polymers can be prepared from well-known water soluble polymers such as poly(ethyleneimine), poly(acrylic acid) [90,91] or polyethers [92] (see also Chapter 2). The solubility of these catalysts is often pH-dependent [90,91,93] so they can be separated from the reaction mixture by proper manipulation of the pH. Some polymers, such as the polyethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) block copolymers, have inverse temperature dependent solubility in water and retain this property after functionalization with PPh2 and subsequent complexation with rhodium(I). The effect of temperature was demonstrated in the hydrogenation of aqueous allyl alcohol, which proceeded rapidly at 0 °C but stopped completely at 40 °C at which temperature the catalyst precipitated hydrogenation resumed by cooling the solution to 0 °C [92], Such smart catalysts may have special value in regulating the rate of strongly exothermic catalytic reactions. [Pg.67]

Step 3. The reaction is exothermal. After process/process energy saving for feed preheating, the excess energy is rejected to the cooling water. Because the only reason of the furnace is to ensure constant inlet reactor temperature the first control loop is inlet reactor temperature/fliel inflow. To prevent the thermal decomposition of the product, a second loop keeps constant outlet reactor temperature by manipulating the quench stream. [Pg.540]

The flow rate of extraction water fed to the top of column C2 is ratioed to the feed to this column D1 by using a multiplier and a remote-set flow controller. The temperature of the extraction water is controlled by manipulating cooling water to the cooler. Base level is controlled by manipulating bottoms, and reflux drum level is controlled by manipulating distillate. The binary methanol/water mixture from the bottom of column C2 is fed to column C3. A constant reflux ratio is maintained in this column by adjusting reflux flow rate. [Pg.271]

A conventional control structure for this process, which works for low to moderate activation energies, is shown in Figure 9. The flowrate Fob of gaseous fresh feed of B is manipulated to control system pressure. The flowrate Fqa of gaseous fi esh feed of A is ratioed to Fob and the ratio is reset by the composition controller, which maintains the composition of A in the circulating gas stream at yuA = 0.5. A bypass stream around the FEHE controls the furnace inlet temperature. Furnace firing controls reactor inlet temperature. Separator drum temperature is controlled by heat removal in the condenser (typically the cooling water valve is wide open to minimize drum temperature). Liquid product comes off on drum level control. [Pg.32]


See other pages where Manipulation of the cooling-water is mentioned: [Pg.519]    [Pg.696]    [Pg.519]    [Pg.696]    [Pg.188]    [Pg.188]    [Pg.265]    [Pg.469]    [Pg.175]    [Pg.80]    [Pg.291]    [Pg.33]    [Pg.7]    [Pg.128]    [Pg.97]    [Pg.163]    [Pg.479]    [Pg.36]    [Pg.107]    [Pg.128]    [Pg.40]    [Pg.216]    [Pg.241]    [Pg.633]    [Pg.161]    [Pg.544]    [Pg.117]    [Pg.112]   


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Cooling water

Manipulation of the cooling - water flow

Manipulation of the cooling-water flow rate

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