Technology for Extra Profit – Simple, Easy and Affordable

Analysts have estimated that in oil refining the leaders gain over 2 $/ton more from Advanced Process Control (APC) than the average users. For a mid-sized refinery this brings extra cost savings of around 10 million $/year! Other industries like Chemicals have lower product throughput but much higher margins and so the potential gains are similar. The wide variety of processes there, however, does not allow making general claims. But, no matter what type of industry: 

APC has proven to be the most cost and time effective means to increase the profitability of the production!

Although intensively exploited by some since the early 70’s, most companies are still reluctant because they consider these technologies as complex and difficult to use – especially for operators, always needing extra computer platforms plus hefty priced software systems etc. However, special approaches exist that disprove the common perception: ACT offers technologies that are extremely simple and easy to use yet can bring substantial benefits for the plant.

Model Based Predictive Control

Model Based Control (MBC) handles difficult process dynamics (long deadtime, high controllability ratio, inverse response etc.) with ease. It delivers highest performance, reduces variations and keeps variables closer to setpoints or constraints, leading to higher product yield, quality or plant capacity, to lower emission or energy consumption.

MBC also can act smoother on the process, important for tightly integrated plants and sensitive equipment, which often reduces the consumption of the resource. For temperature control e.g. typical savings from reduced use of the heating medium are ~ 1k€ / MW. And, contrary to widespread belief, this is not difficult to achieve, MBC is not necessarily complex or difficult: Using our AMC controller, ACT has developed once a complete feedback + feedforward application in just one day!

AMC delivers top performance at a fraction of the cost and effort of complex approaches and has some more advantages:

             Extremely simple, easy to learn, to use and to maintain, immediate operator acceptance

             Robustness against model errors and non-linearities

             Separate tuning for load upsets and setpoint changes, much easier and faster than tuning a PID - see below!

             Runs in every DCS and does not need extra hardware and interfaces

             Easy extension to adaptive control.

    Tuning the AMC controller

Tuning can be done separately for setpoint changes and load upsets (disturbances) and is extremely easy: Just use the scroll bars to adjust the response. Absolute and rate-of-change (speed) restrictions on the output can be taken into account.

See some more examples 

Constraint control

This is a technique to drive one (or more) target variable to the limits. These control schemes can approach limits closer than the operators, detect chances and threats much earlier and allow deeper exploitation of equipment and resources. Examples are throughput maximization, maximization of the yield of a certain product, tower pressure minimization etc. In the left picture below the throughput through a cooler is maximized subject to constraints in the cooling water temperature and the valve position.

Although for larger problems model based controls are needed, smaller ones can be easily handled with PID based schemes – right in the DCS. Distillation tower pressure minimization e.g. can be done this way: The lower the pressure, the less energy is needed and this means less cost and also less pollution. 3–5 % savings are typical – with less than a week of development effort!

Optimization in real time

Just as MBC, optimization is for many synonymous with complex, difficult and impossible without heavy math. Yet, model-free optimization is none of this: It is a simple technique that probes the process to find the best operating point for to the given objective. Only a small algorithm is required that runs in the DCS. Applications aim at maximum product preheating (or cool-down) with parallel heat exchangers, efficiency maximization of furnaces, energy-yield optimization for distillation columns, etc. A case worth mentioning is the total yield maximization for products that are produced by different units and processes. Such an application is delivering since over 20 years more than a million Euros per year. Every year! It is one of our smallest ever developed and the effort was just two weeks.

In the right picture the optimum flow distribution between the two exchangers is sought for which the maximum product heat-up is achieved.  

For all our technologies, the license fee is paid only once per DCS, but they be used in that system over and over again, just like the PID!

All these techniques are also available in our software package TOPAS. They can be tried out, learned and used for developing prototypes in a realistic simulation environment in a most cost and time effective way. Furthermore, ACT has experience in these techniques since the late 70’s, thus we are ideally positioned to help building your first application and also standard schemes for later easy re-use.

ACT - D.I. Hans H. Eder KEG
Wienerstr. 10, 3443 Elsbach, Austria
Brussels office: Madeliefjeslaan 13, 3080 Tervuren
Phone ++32-(0)2-767-0895, e-mail: office@act-control.com