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!

Wednesday, September 10, 2014

Did you know you can perform an optimization in CHEMCAD?

Your process (or process design) is probably not fully optimized. Of course, you know that, and you own a simulator to improve your process. For example, you may make a relatively simple calculation like finding the optimal feed tray location in a distillation column.

In our training courses, we teach a simple method of using CHEMCAD's sensitivity analysis to vary feed tray location while measuring reboiler duty, and we've heard back from a number of you who've achieved significant savings from doing just that.

But did you know that you can have CHEMCAD do the work for you? This is not only possible, but also very straightforward.

Included with CHEMCAD is an optimizer (using General Reduced Gradient, Successive Quadratic Programming, or Simultaneous Modular SQP routines) that allows you to define an objective function and tell the program which variables it can adjust in order to find the optimum (min/max). After just a few clicks, you'll have your solution.

Now let's go even further: many dedicated optimization engines allow "multi-variable" optimization, but you don't need to look beyond the software you already have.

An easy-to-understand example is a CAPEX/OPEX calculation, designed to find the optimal allocation of resources over a given period of time. Using CHEMCAD's cost algorithms, you can get a total equipment cost and an operating cost (energy, utilities, feeds, etc.), which can all be fed to an Excel(TM) spreadsheet using CHEMCAD's Data Map. Another approach to calculating the CAPEX and OPEX values and ratio would be to write a routine in CHEMCAD's Visual Basic for Applications (VBA) tool. The ratio is then available as your objective function in the optimizer.

We told you money was hiding in your process--isn't it time you went out and got it?

To find out more, get in touch with our sales or support representatives. Happy optimizing!

Tuesday, September 2, 2014

Did you know that CHEMCAD has offered embedded rigorous heat exchanger modeling for over eight years?

CHEMCAD's CC-THERM module has offered embedded rigorous modeling of heat exchangers for many years. Why is this a valuable tool?

In many cases, general heat transfer calculations for exchangers are sufficient. In other circumstances, though, you really need a more rigorous model. Let's look at a few examples where rigorous heat exchanger modeling can help you obtain faster, more accurate results.

Imagine you're a plant engineer and are asked to find a way to improve throughput. Can your existing heat exchangers handle the increased flow? You can use CC-THERM in Rating mode to enter specifications for the existing exchanger (TEMA type, # of tubes, baffles, etc.) and get the flows, temperatures, and pressures to match current conditions. Then increase the flow in the model to see if you exceed any constraints on the exchanger.

Suppose there's a concern with fouling in a particular stream. You can switch to Fouling Rating mode in CC-THERM to calculate the fouling rate that allows the model to fit reality. Then increase the flow in the model as before, to determine whether the existing exchanger will be sufficient.

Is the exchanger you have not big enough to handle the increased throughput? You can use CC-THERM in Design mode to design a replacement exchanger. Use the specifications of the existing exchanger to create your initial estimates, since you know these specs are close to your requirements. Now you can approach your heat exchanger manufacturers with a much clearer picture of what you need and what their proposed design should look like.

CC-THERM is available as a stand-alone product or as an add-on to your existing CHEMCAD package. Please contact us at 1-800-CHEMCAD for more details!