Design Problem 3 Figure 4 shows a stirred tank reactor in which two teeds A and B are reacted to a product C. A small amount of gaseous byproducts are produced in the reactor. The reaction is exothermic and the heat of reaction is removed by the cooling jacket serviced by cooling water. Of the material vaporised from the reactor, as much as possible is condensed by a cooling water condenser and refluxed to the reactor. The uncondensed gases are passed to an absorber where as much as possible is absorbed in water. Any gases not absorbed are vented to atmosphere. Liquid from the absorber is sent to effluent. Figure 5 shows the feed system for the reactor. The feeds to the reactor are to be temperature controlled. The feeds are first heated by heat recovery and then by steam before entering the reactor. The product is to be temperature controlled by cooling water. For the design of the control system, a conceptual design is required at this stage, whereby the control signals can be shown as generic signals and it is not necessary to show the location of the control devices. a) Develop a conceptual design for the control system tor the reactor and absorber in Figure 4. The reactor temperature and pressure both need to be controiled. it is not considered necessary to provide temperature control for the reflux condenser for the reactor. Give a short description to justity the basis of the conceptual design. [13 Marks] b) Develop a conceptual design for the control system for the absorber in Figure 4. The pressure of the absorber needs to be controlled to a different pressure from that in the reactor. For the control of the absorber, it is necessary to consider how the absorber functions to provide enough solvent for a given flowrate of gas. Give a short description to justity the basis of the conceptual design. [15 Marks] c) Develop a conceptual design for the reactor feed system in Figure 5. The production flowrate should be controlled by the flowrate of Feed A. The two feeds are to be controlled to be in their stoichiometric ratio. The flowrate splt ratio of the reactor effuent needs to be controlied to be the same as the ratio of the flowrates of the two feed streams. It is important to account for any linkages between the control system for the reactor and absorber and the reactor feed system. Give a short description to justify the basis of the conceptual design. [17 Marks] Figure 5 Reactor feed system. Figure 5 Reactor feed system. Design Problem 3 Figure 4 shows a stirred tank reactor in which two teeds A and B are reacted to a product C. A small amount of gaseous byproducts are produced in the reactor. The reaction is exothermic and the heat of reaction is removed by the cooling jacket serviced by cooling water. Of the material vaporised from the reactor, as much as possible is condensed by a cooling water condenser and refluxed to the reactor. The uncondensed gases are passed to an absorber where as much as possible is absorbed in water. Any gases not absorbed are vented to atmosphere. Liquid from the absorber is sent to effluent. Figure 5 shows the feed system for the reactor. The feeds to the reactor are to be temperature controlled. The feeds are first heated by heat recovery and then by steam before entering the reactor. The product is to be temperature controlled by cooling water. For the design of the control system, a conceptual design is required at this stage, whereby the control signals can be shown as generic signals and it is not necessary to show the location of the control devices. a) Develop a conceptual design for the control system tor the reactor and absorber in Figure 4. The reactor temperature and pressure both need to be controiled. it is not considered necessary to provide temperature control for the reflux condenser for the reactor. Give a short description to justity the basis of the conceptual design. [13 Marks] b) Develop a conceptual design for the control system for the absorber in Figure 4. The pressure of the absorber needs to be controlled to a different pressure from that in the reactor. For the control of the absorber, it is necessary to consider how the absorber functions to provide enough solvent for a given flowrate of gas. Give a short description to justity the basis of the conceptual design. [15 Marks] c) Develop a conceptual design for the reactor feed system in Figure 5. The production flowrate should be controlled by the flowrate of Feed A. The two feeds are to be controlled to be in their stoichiometric ratio. The flowrate splt ratio of the reactor effuent needs to be controlied to be the same as the ratio of the flowrates of the two feed streams. It is important to account for any linkages between the control system for the reactor and absorber and the reactor feed system. Give a short description to justify the basis of the conceptual design. [17 Marks]
