Why Use Process Simulation?

In this modern age of powerful computers, it often makes no sense to put pencil to paper like in the old days.  Now, new software can perform repetitive chemical engineering calculations in a fraction of the time it takes to execute them by hand.  Imagine you have been tasked to design a distillation column to produce a 90% benzene overhead product and a 95% toluene bottoms product.  You look up the VLE data for benzene-toluene, carefully construct your x-y diagram, draw the feed line, and step off your McCabe-Thiele trays.  Estimate tray efficiencies.  Then you calculate your mass and energy balance, product and bottoms dew points and bubble points, and estimate your overhead condenser and column reboiler duties.  Wrestle with those tedious hydraulics equations to determine the column diameter.  Then dust off the old heat transfer equations and some time later you have your condenser and reboiler sized.  Finally – the system is designed.

And then they decide they want 95% benzene, and by the way, the feed rate is 2,500 pounds per hour, not 1,500….

The Advantage of Simulation

For the example above, getting the initial solution using process simulation software would take….about the same amount of time.  BUT, when the design conditions are changed – and has there ever been a design where they haven’t? – the speed and accuracy of process simulation begins to save tremendous time and money.  And not only for design changes.  In the example above, you had to select your reflux rate based on some old rule of thumb about the optimum reflux being some multiple of the minimum reflux.  Wouldn’t it be better to be able to plot reflux rate versus energy usage?  Versus number of trays?  And automatically, with one software command?

Multiple runs – quickly.  Process design optimization – quickly.  Such is the power of process simulation.  The example given above is for a distillation tower, but the same holds true for any number of chemical engineering unit operations – heat exchangers, reactors, heaters, absorbers, extractors, crystallizers, evaporators; even pumps, compressors, and piping systems.  In fact, even an entire plant – in one model.

And operations.  Have you ever wondered if that old packed tower or heat exchanger will work in this new application?  Let’s model it and see.

Our Commitment to Simulation

It is our opinion that process engineering services are no longer adequate or complete without the presence of comprehensive process simulation software and chemical engineers highly skilled in its use.  In the ever more competitive world of manufacturing, it is no longer acceptable to determine just a correct answer – the BEST answer is required.  And it is almost never possible to achieve the best answer within the confines of any client’s project budget without the use of simulation software.  Answers like:

  • The feasibility of, and optimum operating conditions for utilizing a two-tower valve tray distillation system (originally designed for depropanizing and debutanizing gasoline) for the production of high-purity propane, iso-butane, and n-butane from various pipeline and refinery feedstocks
  • The optimum process orientation and operating conditions for a multi-tower absorption system for producing maximum product concentration, minimum offgas concentration, and minimum operating costs
  • The optimum reactor design and operating conditions for maximum product yield and minimum byproduct contamination
  • The fact that despite energy savings as compared to a distillation system, a multi-effect evaporator was not technically feasible due to operational instability
  • The optimum number of stages and operating conditions for minimizing energy consumption for a product-concentrating distillation system
  • The best retrofit option for a solvent recovery condensing system, maximizing product recovery while eliminating downtime due to freezing events
  • The best retrofit option for a fume incineration system, minimizing supplemental fuel usage.

 All real projects recently completed by PROCESS.  In all cases it was possible to get the BEST answer from process simulation.

Simulation Software

In the beginning, PROCESS took three months to evaluate the leading simulation softwares.  At the end of the process, we selected Chemstations’ CHEMCAD simulation software product.  To a large extent, we believe that the leading softwares are technically equivalent – but we wanted a partner in this endeavor, and it was our perception that Chemstations’ customer and technical service personnel were superior to their competitions’.  Our engineers have trained extensively on the proper use and application of the software.  We have worked very closely with Chemstations over many years with the development of improvements to the software.  But most importantly, we consult with their expert simulation engineers on a frequent basis, both as a check on our work and for assistance in solving unusual or complex problems.

More recently, as PROCESS began performing more projects in the petroleum refining and oil & gas sectors, client’s operations were heavily invested in previous HYSYS simulations and thus required that software to be utilized. As such PROCESS now maintains a full suite of Aspen Hysys and Aspen Plus software. The following is a list of simulation software PROCESS currently maintains in-house:

Chemstations Aspen Tech OLI Systems
CHEMCAD Steady State Aspen Plus Electrolyte
CHEMCAD Dynamics Aspen Hysys
CHEMCAD Batch Aspen FlareNet
CHEMCAD Polymers

The Benefits to You

  • Accurate design information
  • Software-produced mass and energy balances and process flow diagrams
  • Multiple design cases at a fraction of the cost
  • Process optimization, finding the process’ maximum performance point
  • Sensitivity analyses, determining the process’ key control variables and degree of operating stability.

Call us with your application.  It might be the most cost-effective thing you do all year.