Feed rate, influence

One such approach is called cascade control, which is routinely used in most modern computer control systems. Consider a chemical reactor, where reac tor temperature is to be controlled by coolant flow to the jacket of the reac tor (Fig. 8-34). The reac tor temperature can be influenced by changes in disturbance variables such as feed rate or feed temperature a feedback controller could be employed to compensate for such disturbances by adjusting a valve on me coolant flow to the reac tor jacket. However, suppose an increase occurs in the... 

W1 is Bond work index based on 100 percent passing a 200-mesh sieve, is the sohds feed rate in kg/min, and S is weight percent solids in the feed. This represents experimental data for limestone, feldspar, sulfide ore, and quartz. The influence of Wl is believed to be due to its effect on amount of fines present in the mill. Parameters that did not affect are specific gravity of feed material, and feed size over the narrow range studied. 

A small amount of nickel in the FCC feed has a significant influence on the unit operation. In a clean gas oil operation, the hydrogen yield is about 40 standard cubic feet (scf) per barrel of feed (0.07 wi /r ). This is a manageable rate that most units can handle. If the nickel level increases to 1.5 ppm, the hydrogen yield increases up to 100 scf per barrel (0.17 wt%). Note that in a 50,000 barrel/day unit, this corresponds to a mere 16 pounds per day of nickel. Unless the catalyst addition rate is increased or the nickel in the feed is passivated (see Chapter 3), the feed rate or conversion may need to be reduced. The wet gas will become lean and may limit the pumping capacity of the wet gas compressor. 

An example of cascade control could be based on the simulation example DEACT and this is shown in Fig. 2.35. The problem involves a loop reactor with a deactivating catalyst, and a control strategy is needed to keep the product concentration Cp constant. This could be done by manipulating the feed rate into the system to control the product concentration at a desired level, Cjet- In this cascade control, the first controller establishes the setpoint for flow rate. The second controller uses a measurement of flow rate to establish the valve position. This control procedure would then counteract the influence of decreasing catalyst activity. 

A gas phase reaction, A = B, is carried out under conditions where both surface reaction and diffusion to the external surface influence the overall rate of conversion. The feed rate is 200 Ibmol/hr of pure A, the pressure is 2 atm and 50% conversion is required. 

The combined group Ua has been shown 25 26-1 to be influenced by the feed rate of solids, the air rate and the properties of the material, and a useful approximation is given by ... 

Since the accumulation is determined by a balance between feed rate and reaction rate (reactant depletion), it can be influenced by using different feed rates or different temperatures. This offers the possibility of optimizating the process conditions (discussed in Section 7.9). 

Figure 7.8 Influence of the feed rate 4, 6, and 8 hours on the heat release rate (left) and on the accumulation (right).

Feed rate (FE) The feed time does not explicitly appear in Equation 7.23. However, it directly influences the amount of reactant B accumulated in the reactor, and hence the maximum temperature, which can be reached after a cooling failure has occurred during the course of the reaction. Therefore, the feed rate is a key parameter, which has to be monitored and technically limited to the highest allowable value. This will be discussed in Section 7.8. 

Figure 6.21 Influence of feed rate on moisture content of product.

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