The 'onion diagram' design hierarchy, as shown in Figure 2.24, represents a design that starts with which component at its core?
Explanation
The onion diagram provides a structured, hierarchical approach to process synthesis. It prioritizes design decisions by starting with the most critical part of the process—the chemical transformation in the reactor—and progressively adding layers for separation, heat integration, utilities, and environmental controls.
Other questions
In a process flowsheet, what is the key difference between a block flow diagram and a Process Flow Diagram (PFD)?
According to the list of essential information to be included on a PFD, which of the following items is considered optional?
What is the primary function of the 'Reaction' stage (Stage 3) in the anatomy of a typical chemical manufacturing process?
Which of the following is considered an advantage of batch processing over continuous processing?
In the manufacture of vinyl chloride (VC) by the pyrolysis of dichloroethane (DCE), the reactor conversion is limited to 55 percent. Calculate the quantity of DCE (molecular weight 99) in kmol/h that must be fed to the reactor to produce 5000 kg/h of VC (molecular weight 62.5), assuming negligible side reactions.
How is 'Selectivity' defined in the context of reactor performance?
In a process with a recycle stream, why is it often necessary to include a purge?
An ammonia production process has a recycle loop. The feed to the process contains 0.2 percent argon. To maintain the process, a purge is required to hold the argon concentration in the recycle stream below 5.0 percent. Based on 100 moles of feed, what is the required purge rate in moles?
What is the primary purpose of a patent in the context of process design information?
What does the legal concept 'freedom to practice' mean for a process design engineer?
When making modifications to improve the economics of an established process, which tactic usually gives the biggest impact?
What is the key difference between a 'debottlenecking' project and a 'retrofit' project for an existing plant?
In revamping a fixed-bed catalytic reactor, the pressure drop across the bed is proportional to the flow rate squared. If the flow rate is increased by 50 percent, by what factor does the pressure drop increase?
When debottlenecking a separation column is necessary, what is a common tactic that involves adding a new column to the process?
When two identical compressors are used in parallel, how does the resulting performance compare to a single compressor?
The term 'process synthesis' is used to describe what activity in process design?
What is the primary purpose of a PFD review?
What is the first step in devising a new process design according to the text?
In a process for the chlorination of ethylene to produce DCE, the conversion of ethylene is 99.0 percent. If 94 mol of DCE are produced per 100 mol of ethylene reacted, what is the overall yield based on ethylene fed?
What is the recommended best practice for showing utility (service) lines on a process flowsheet?
To ensure complete combustion in a furnace burning natural gas, 20 percent excess air is supplied. The gas is 95 percent methane (CH4) and 5 percent ethane (C2H6) by volume. How many moles of air are required per mole of fuel?
When solving a recycle problem using the 'cut and try' or 'tear' method, what is the general procedure?
What is one of the most effective strategies for reducing commercialization risk when designing a new process?
When revamping plant hydraulics, if an existing centrifugal compressor cannot be reused in its current location, what should be the next evaluation step for that piece of equipment?
What is the primary reason for the precision of data on a process flowsheet, such as component flows, typically being limited to three or four significant figures?
How should a trace quantity of a component be represented in the data table of a PFD?
When modifying an established process, what is a typical method used to improve environmental impact by reducing Volatile Organic Compound (VOC) emissions from a dryer?
What is a key consideration during a PFD review walk-through of a feed section, as exemplified by the questions in Table 2.2?
In the context of the overall procedure for flowsheet development, when does the text suggest it is most appropriate to use process synthesis techniques?
What is the typical plant attainment or operating rate assumed for a continuous process in a design basis?
If a plant revamp involves increasing the flow rate, why must all pump-and-line and control valve sizing calculations be repeated?
In the 'onion diagram' hierarchy of process synthesis, what step is taken immediately after designing the separation and recycle system?
What is the primary drawback of using the simple shortcut distillation models available in process simulators?
What is the common abbreviation 'NNF' used for on a PFD?
What is a common method for debottlenecking a reactor without adding a new vessel?
What does the abbreviation 'DBO' signify on a Process Flow Diagram?
According to the procedure for process synthesis in Figure 2.25, what should be done if the initial economic assessment (Step 1) shows that the process is not attractive?
What is the primary role of a 'heuristic rule' in process synthesis?
In a heat exchanger system revamp, if a plate heat exchanger E101 is a gasketed-plate type, what is a key advantage for increasing its capacity?
What is the typical layout convention for the overall process flow on a PFD?
Why is it recommended to show control valves on a PFD, even though not all companies follow this convention?
In the production of ethanol by hydrolysis of ethylene, a feed stream is 55 percent ethylene and the product stream is 52.26 percent ethylene. If the feed contains 5 percent inerts and the product contains 5.28 percent inerts, what is the conversion of ethylene?
When is it preferable to use a continuous process over a batch process?
In a revamp, how can the capacity of a centrifugal pump often be increased without replacing the entire unit?
What is the role of the 'preliminary process hazard analysis (PHA)' (Step 6) in the procedure for process synthesis?
When using a process simulator, printouts of the graphical user interface (GUI) that resemble a PFD should not be used as actual PFDs. What is the primary reason given for this?
What is the final stage in the 'anatomy of a chemical process' as shown in Figure 2.11, just before sales?
What is a major reason that 'experienced engineers usually prefer the tried and tested methods rather than possibly more exciting but untried novel designs'?
During a PFD review, what is the 'walk through' procedure?