In a distillation column simulation, what does a broad, flat region in the composition profile plot typically indicate?
Explanation
Plotting the composition profiles in a distillation column is a powerful diagnostic tool. A long, flat section in the profile indicates that little or no separation is occurring on those trays, which is a clear sign of a suboptimal design, often due to an incorrect feed location or having far more trays than necessary.
Other questions
What is the primary characteristic that distinguishes sequential-modular simulation programs from simultaneous (equation-oriented) programs?
What is a general guideline regarding the inclusion of components in a process simulation model based on their concentration?
What are pseudocomponents (or hypocomponents) primarily used to model in process simulations?
What is the minimum information typically required to create a new hypothetical pure component in UniSim Design?
Using the Chueh and Swanson method, estimate the specific heat capacity in kJ/kg C of ethyl bromide (CH3CH2Br) at 20 C. The group contributions are: -CH3 = 36.84, -CH2- = 30.40, and -Br = 37.68 kJ/kmol C. The molecular weight is 109.
What is the primary limitation of the UNIFAC group contribution method for predicting phase equilibrium?
In a process simulation, when is a conversion reactor (stoichiometric reactor) model most appropriately used?
What is the primary drawback of using shortcut distillation models in a process simulation?
In the context of a process flowsheet with a recycle loop being solved by a sequential-modular simulator, what is a 'tear' stream?
What is the Bounded Wegstein method, which is the default convergence method in most simulation programs?
What is a significant drawback of using a Gibbs reactor model when a component set includes aromatic hydrocarbons, hydrogen, and carbon?
What is the primary purpose of using a 'component splitter' model in a process simulation?
According to the text, what is a common problem encountered when simulating process-to-process heat exchangers, and what is a recommended practice to avoid it?
When modeling a gas turbine engine in UniSim Design as shown in Example 4.9, what combination of simulation units was used to represent the combustor and the dynamo/shaft losses?
For the autothermal reforming process described in Example 4.5, with a 98 percent conversion of methane, what was the calculated temperature at the exit of the reforming reactor?
What is one of the most common causes of convergence failure in rigorous distillation models?
In a shortcut distillation model for a feed of 100 mol/h of an equimolar mixture, a 99 percent recovery of the light key means how many mol/h of the light key is allowed in the bottoms?
What is one of the first steps an experienced designer would take to troubleshoot a simulation flowsheet that is not converging?
What is the purpose of a controller function like 'Design Spec' in Aspen Plus or 'Adjust' in UniSim Design?
For what purpose is dynamic simulation most useful, according to the text?
In the naphtha isomerization process from Example 4.10, the shortcut column model calculated a minimum reflux ratio of 3.75. The reflux ratio was then set to what value for the simulation?
What is a key difference between a CSTR (Continuous Stirred Tank Reactor) model and a PFR (Plug Flow Reactor) model in a process simulation?
According to the solution for Example 4.8, what was the primary reason the initial single-shell heat exchanger design was unacceptable?
After modifying the heat exchanger design in Example 4.8 to a three-shell system, what was the new total surface area compared to the original single-shell design?
What is the key advantage of a simultaneous, dynamic simulator?
When building a pure component model for a process simulation, why is it important to always include any component that has a specified limit in any of the products?
What type of solid is a material like coal or wood pulp modeled as in Aspen Plus, which is defined by attributes rather than molecular properties?
When is it recommended to use a detailed model with a full component list versus a high-level model with only the main bulk components?
Using Lydersen's method to estimate the critical temperature (Tc) of a compound, what is the formula that relates Tc to the normal boiling point (Tb) and the sum of critical temperature increments (delta T)?
What is the fundamental criterion for thermodynamic equilibrium between two phases for every component 'i' in a multicomponent mixture?
For which type of system would the Peng-Robinson (P-R) equation of state be a suitable choice for modeling phase equilibrium?
What is a major challenge in modeling real industrial reactors compared to the simple library models in simulators?
Why is it often necessary to use a USER2 block or a user subroutine to model complex operations in Aspen Plus?
What is the typical range for the optimum reflux ratio in a distillation column relative to the minimum reflux ratio (Rmin)?
In the distillation column sizing in Example 4.7, the process design basis was 225 metric tons per hour. What feed rate was used for the equipment design basis to account for a safety factor?
When is the Newton convergence method recommended for solving flowsheets with recycles?
What is the primary function of a Yield Shift Reactor model in process simulation?
What is the recommended approach for validating a physical property model when no experimental data is available?
In the context of the structure of a typical simulation program, what is the role of the 'executive program'?
For the shortcut distillation column in Example 4.6, designed to separate a five-component equimolar feed, what was the calculated minimum number of stages?
What is the purpose of using manual calculations to generate an initial estimate for a recycle tear stream?
What is a major limitation of the Wilson activity coefficient model compared to NRTL or UNIQUAC?
In the final converged solution for the naphtha isomerization process in Example 4.10, what was the flow rate and composition of the recycle stream?
What is the purpose of the strategy known as to 'creep up on' a converged solution?
What is the general guideline for the number of pure components in a model to maintain efficient solving?
What is a key consideration when modeling a liquid-liquid extraction process?
In the gas turbine simulation in Example 4.9, what was the calculated net power produced by the dynamo and the overall cycle efficiency?
Which of the following is NOT listed as a core component of a typical process simulation program's structure?
What is the primary reason for using a rigorous distillation model instead of a shortcut model?