Plant design, constraints

The lower bound, on the other hand, is at the discretion of the designer. Constraints (10.1), (10.2) and (10.15)—(10.17 ), in conjunction with the overall plant scheduling constraints, constitute a complete MILP formulation for direct heat integration in batch processes in a situation where the batch size is fixed along the time... 

Plant operating constraints are readily obtained from design data and operating history. There is usually little need to update these constraints unless the plant is debottlenecked or we want to study some new process configuration. 

However, design constraints may limit our ability to exercise this strategy concerning fresh reactant makeup, An upstream process may establish the reactant feed flow sent to the plant. A downstream process may require on-demand production, which fixes the product flowrate from the plant. In these cases, the development of the control strategy becomes more complex because we must somehow adjust the setpoint of the dominant variable on the basis of the production rate that has been specified externally. We must balance production rate with what has been specified externally. This cannot be done in an open-loop sense, Feedback of information about actual internal plant conditions is required to determine the accumulation or depletion of the reactant components. This concept was nicely illustrated by the control strategy in Fig. 2.16, In that scheme we fixed externally the flow of fresh reactant A feed. Also, we used reactor residence time (via the effluent flowrate)... 

This section addresses the question how the research work in IMPROVE has had an impact on industrial practice in process and plant design from the chemical and process engineering as well as from the software vendors perspectives. We will start this section with a brief discussion on business objectives and the relations between these industries, which obviously act as constraints in the process of transferring results from the research in IMPROVE to industrial practice. 

The first commercial application of the Mobil Methanol-to-Gasoline (MTG) process has now been in operation for over a year and a half in the Gas-to-Gasoline (GTG) plant in New Zealand. The catalyst used in the process and the reaction mechanism impose important design constraints. This paper discusses the approach used for the scale-up and design of the fixed-bed MTG reactor system. Design philosophy and selection of equipment to meet the stipulated process and operating objectives are also reviewed. 

Constraints of Plant Design. The potential hazards encountered in the uranium feed materials processing industry include many that are common to the heavy chemicals industry. However special problems present themselves owing to direct radiation, the possibility of inhalation and ingestion of radioactive dusts and gases, nuclear safety, and more unusual chemical hazards. 

Design constraints There are generally more constraints due to re-use and modifications of the existing plant equipment within limited plot space and project execution time Fewer design options and constraints... 

Design Basis is the design inputs, the design constraints, and the design analysis and calculations, It includes topical areas such as seismic qualification, fire protections, and safe shutdown, It encompasses consideration of such factors as plant availability, plant efficiency, costs, and maintainability, and that subset that relates to safety and the authorization basis. 

To understand the plant design margins and constraints, it is recommended to conduct a rating survey for key equipment, and the results can be shown in a plot with rankings and indications of which equipment are limiting and which ones have spare capacity with how much. 

These tools can be used for several applications plaiming, optimization, diagnosis, and control. Their integration in overall system simulation allows reliable plant design and the setting up of the operating conditions while checking the local constraints, for example, the maximum temperature on the cell plane or the maximum difference between the anode and cathode pressures. 

Since the Ca-Br water splitting chemical reaction requires a heat source at 725 C to cause the CaBr2 + H2O CaO + 2HBr reaction to take place, that temperature must be maintained even if the water cracking plant is operating at only partial load. Therefore, for STAR-H2, another design constraint was imposed - the core outlet temperature of 800X at full load must also be maintained at all levels of partial load. 

Note that Constraint 2 on x d has been specified by plant designers in advance. If x d should be changed in response to operating and economic conditions, it could be determined on-line via real-time optimization (Chapter 19). 

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