Wednesday, October 29, 2014

Did you know you can model mass transfer in distillation columns in CHEMCAD?

Distillation columns are the ubiquitous workhorses of the chemical processing industry. Design and optimization of these unit operations is done at a much higher level of fidelity than ever before using mass transfer models.

As students, we learned McCabe-Thiele diagrams and shortcut methods to solve simple distillation systems. Often, a little more complexity was added using a spreadsheet to solve harder problems. Then, of course, we were given access to a simulation program which used more rigorous methods, including simultaneous correction and/or inside-out algorithms. When it came to actual columns in the field, however, they didn't always achieve quite what the equilibrium-stage based calculations predicted. You could specify an overall efficiency or even stage-by-stage efficiency profiles to get a better match, but this was a crude way of dealing with the issue.

Enter mass-transfer models, like Bravo & Fair for random packing, Bravo, Rocha & Fair for structured packing, and Billet & Schultes for random or structured packing. CHEMCAD includes these models, along with a database of common packing coefficients. For trayed columns, we include the Chan-Fair, AIChE, and Zuiderweg tray models.

Defining the geometry of such a column requires more user input, but the payoff is vastly improved accuracy and realism in the results for product streams, energy usage, and pressure drop.*

So, take a moment to back up a copy of a simulation with distillation column(s); convert them to mass-transfer by specifying the actual trays/packing you're using; and enjoy the benefits of more accurate answers to your distillation calculations. If you have questions, or if you want to share your successes, give our technical staff a call today!


* I should mention here that from what I've seen in papers delivered by distillation experts over the years, column-internals installation issues can cause significant deviation from expected results in the field. There are a number of companies that specialize in identifying such issues, and I invite you to check out our friends, Dr. Frank Seibert & Dr. Bruce Eldridge, over at the University of Texas Separations Research Program if you're interested in applied research on this topic and more.

Wednesday, October 15, 2014

Did you know you can quickly make property calculations in CHEMCAD?

Quick, what's the bubble point of the process stream entering one of your columns? What's the viscosity of the stream entering your heat exchanger? You may find yourself needing answers to these types of questions much more often than needing to model an entire process, and we've made it easy to access these calculations in CHEMCAD.

If you have an existing flowsheet with a stream already set up with the right composition, just double-click the stream, and you can immediately calculate bubble/dew point (T or P) or vapor fractions. Just remember Gibbs' phase rule and specify two of the three available fields (T, P, VF); then click the Flash button and you'll have your answer. To get at the thermophysical properties, just right-click the stream and select View Properties to get a quick report.

But what if you want to use a composition that isn't in your current flowsheet? If all the right chemicals are in your component list, and you've got the appropriate K-value and enthalpy methods selected, try this trick: 
  1. Make sure no streams are selected (you can click in the white space of the flowsheet to be certain).
  2. On the CHEMCAD main menu, choose Specifications > Select Streams.
  3. In the input dialog, type a stream number not currently used in your flowsheet (like 999) and click OK.
You'll now be working with a 'dummy stream.' You can specify stream conditions and compositions, but nothing you do here will affect any of your actual flowsheet streams. By clicking Report > Stream Properties > Select Streams and entering that dummy stream number, you can even generate thermophysical property reports. The dummy stream will be accessible for as long as you have that flowsheet open (it's cleared from memory if you switch flowsheets or close CHEMCAD).

Don't let your investment in simulation sit around waiting for the large projects! CHEMCAD is like having your own chemical engineering calculator, and it's ready to supercharge all of your tasks.

Whether you're working on a simulation of your entire process, sizing a few pieces of equipment, or just looking for a quick property calculation, don't hesitate to get in touch with our technical staff for more best-practices tips.

Thursday, October 9, 2014

Do we need more chemical engineers? Do we need more heroes?

Someone recently forwarded me a link to ExxonMobil's perspectives blog on the subject of engineers in the United States. You can take a look here to see Ken Cohen's take on addressing the need to educate and connect with young people about engineering and engineers--especially the societal impact, both past and present, of our profession.

As I pointed out several years ago, there are a couple of ways to attack this problem. ExxonMobil's site, BeAnEngineer, and their associated television commercials are a fantastic 'top-down' approach to get the message out to the general public. The complementary approach is 'bottom-up,' and their material is also a great resource for engineers who want to arm themselves with facts and figures they can use to have one-to-one or one-to-few conversations with young people or non-technical colleagues and acquaintances.

If we, as engineers, don't tell our story and tell it well, then we leave ourselves open to two serious consequences: (1) our story gets told by those who view chemicals and chemical engineering as inherently 'bad,' and (2) fewer young people are interested in pursuing chemical engineering.

You know the role we play in society now, and the role we'll play in the future. Learn more about our past successes. Tell your story. Tell our story. Be a hero.


Friday, October 3, 2014

Congratulations to Trevor Rice, Outstanding Young Professional!

Our own Trevor Rice has been awarded the South Texas Section AIChE’s Outstanding Young Professional Award for 2013!

Trevor is a valued member of the development team here at Chemstations, and we've seen his devotion to working on quality projects for our customers, so it's little surprise to us that his passion for the profession of chemical engineering has been rewarded by the local section leadership. He continues to contribute his time and effort to make STS a great institution, and we are all very proud of him and his efforts.

Trevor's award will be presented at the 6th AIChE Southwest Process Technology Conference at the Moody Gardens Conference Center and Hotel in Galveston, TX (October 9th and 10th, 2014; more information here). Chemstations technical and sales staff will be present throughout the conference, so stop by to congratulate Trevor and visit with us to chat about process simulation and CHEMCAD!



Did you know CHEMCAD has flexible licensing options for individuals, groups, and companies?

Worrying about a license for your process simulator is probably not how you want to spend your time. We get it. You just want CHEMCAD to be available when you need it--so we try to make our licensing as invisible as possible to you, our customers and users.

To that end, we offer a variety of software and hardware licensing solutions, with the aim of providing a "set it and forget it" path for your organization:
  • System Authorization software keys for single-machine licensing
  • SafeNet(TM) hardware keys for single-machine licensing
  • SafeNet(TM) hardware keys for network licensing
  • SafeNet(TM) RMS software keys for network licensing
In all scenarios, CHEMCAD can be installed on any or all machines in your organization. Now let's look at licensing options for some typical organizations.

Large organization (multi-user, multi-site, wide area network)
  • Access a pool of licenses from any client computer on the network, served by a hardware key placed on any machine on the network.
  • Access a pool of licenses from any client computer on the network, served by a software license server (RMS). This further allows commuting of licenses: for example, a laptop connected to your network can 'check out' a license and then leave your network to use CHEMCAD at a remote site.
Small organization (multi-user, single-site, local area network)
  • License a single, dedicated CHEMCAD machine with a software key.
  • Share one or more hardware keys.
  • Use either of the network options listed above on your local area network.
Individual consultant (single user, one or more machines)
  • License a single, dedicated CHEMCAD machine with a software key.
  • Use a hardware key to enable the most convenient machine (desktop, laptop, etc.) at any given time.
Whether you have a dedicated IT staff, have outsourced IT, or do your own IT, we're here to help. Our technical support staff not only are chemical engineers themselves, but also have a wealth of experience addressing the complex IT needs of all kinds of organizations. We can generate license files, help debug licensing issues, and in some cases, provide contingent licensing if you have network access problems.

If you'd like to explore licensing options, you can browse the CHEMCAD knowledgebase on our customer portal, where you'll find articles that address common licensing questions. You can also get in touch with us directly, and let our staff show you how flexible and available CHEMCAD can be in your computing environment.

Wednesday, September 24, 2014

Did you know you can model aqueous electrolyte systems in CHEMCAD?

Water. It's in almost every plant and system . . . if it's not in your process streams, it's likely in your utilities. If your process is defined by aqueous electrolytes, you've probably already been modeling or planning to model concentration, boiling point rises, precipitation, pH, and so forth.

CHEMCAD has both the modified NRTL and Pitzer thermodynamic systems built right in. They are available for calculation in any unit operation, including distillation columns. With mNRTL, you can run in apparent species or true species modes (we have a great discussion on the pros & cons of each in our help system, and we'd be happy to go over it with you). There are a significant number of common electrolyte species and electrolyte reaction data sets included with the program. If you don't have reaction equilibrium constants, CHEMCAD will estimate them from Gibbs free energy of formation for the electrolyte species or you can regress from laboratory/experimental data.

Even if you don't have electrolytes in your process streams, you can still benefit from this feature: if you'll recall from a prior post on modeling utilities (here), there are economic benefits to analyzing your cooling water system. You can watch the buildup of carbonates or other salts, to determine optimal bleed/purge rates or timing for injection of cleaning chemicals.

To jump-start your next aqueous electrolyte modeling work, get in touch with us--we'd love the chance to help make your project a positive one!

Tuesday, September 16, 2014

Did you know you can model a vessel reactor in CHEMCAD?

Do you have an existing vessel reactor in your process? Often, we hear from customers that they have an existing operating procedure, but they aren't sure exactly how much time the reaction actually requires.

Maybe you have a basic reaction analysis from an R&D group that requires scale-up from the lab to a full-scale vessel reactor. We've worked with organizations that would like to use the same software tool for R&D, process development, and operations.

CHEMCAD has you covered.

It's helpful to think of reaction systems in four parts: (1) the reactants/products/by-products, (2) the reaction, (3) the vessel, and (4) the operation step(s).

For the chemicals, CHEMCAD's database of physical properties includes all the DIPPR(TM) data for pure compounds, as well as a wide variety of methods for calculating mixture properties and the phase equilibria.

For the reaction, you can specify Arrhenius constants (or extended Langmuir-Hinshelwood constants), or you can define your own reaction equation for ultimate flexibility. If you don't yet have the kinetics worked out, CHEMCAD also includes regression facilities that you can use with laboratory or operating data.

For the vessel, you can simulate everything from a laboratory flask to a full-scale, continuously stirred tank reactor (CSTR) with jackets and coils. You can define ancillary equipment like pumps, control valves, and PID controllers for feed streams, product streams, and utilities. Add a vent condenser or even a distillation column to the top of the reactor. You can even model safety scenarios by adding relief devices to the vessel.

For the operation step(s), CHEMCAD's dynamic simulation system allows you to set run times, control schemes, dosing rates, ramp controls, and more. CHEMCAD will rigorously calculate properties, reaction rates, phase equilibria, pressure (if desired), and heat transfer for heating/cooling systems. You'll see volume, composition, temperature, pressure, and more versus time so you can optimize your design or your existing operations. And, of course, you can model batch, semi-batch, or continuous operation.

Want to join the ranks of customers who've successfully designed and optimized their vessel reactors? Contact your CHEMCAD sales or support representative today!