logo


Is pinch enough?

Back in the late 1970’s and early 1980’s when fuel gas prices were high, energy utilization assumed major importance. A new method of calculating heat exchanger networks was developed. It was called Pinch Technology. Today pinch has been rediscovered by engineers who have access to fast computer simulation models. But as occurs with any older method that is rediscovered by a newer generation, enthusiasm generated by the rediscovery tends to obscure the deficiencies while highlighting only advantages. The fact is that Pinch Technology does have value — but its usefulness has certain limitations which must be recognized if it is to be truly useful.

Pinch analysis relies heavily on thermodynamics but relegates practical concerns such as crude hydraulics and distillation to secondary importance. But exchangers are part of the larger integrated system. Forgetting this invites the inevitable—a beautiful pinch analysis for a crude unit, for example, can be rendered meaningless by cold desalters, desalter rag layers, fouling and corrosion in exchangers, coking in fired heaters and poor residue stripping and fractionation. Disregarding these realities can only invite problems, especially with heavy crude oils. The lessons to be learned are that designing grass roots units and when revamping, one should profit from know-how and experience. If a proven design differs from what pinch analysis tells you, weigh your decision carefully. A unit that does not meet processing objectives and is very difficult to start-up is a humbling experience. For revamps it is crucial to know what equipment constraints exist as determined by a comprehensive test run and data analysis. Ultimately the refiner wants something that works, not a theoretically perfect design that operates poorly.

Today fuel prices are sky high. Supplies are tight and because they will remain so until LNG is politically accepted, it is critical that we develop new economies employing state of the art technology. But let us remember that pinch analysis is not new. We have had more than 25 years to evaluate it. Yet it will be useful only when it is used by practical engineers with actual experience with the process being designed.

DOWNLOAD LITERATURE

View More

  • Oil sands crude — profits and problems?

    Canadian bitumen production currently runs about 1 MMbpd, with some being sold as Synbit and Dilbit. Over the next 10-12 years output is expected to increase to 3.5 MMbpd and more refiners will begin investing to process it and come to depend on the Synbit and Dilbit for a significant part of their supply. ...

  • Nasty stuff

    Heavy crudes are here to stay. As longs as oil prices remain high, Canadian, Venezuelan, Deep Water Gulf of Mexico, Mexican and other low API gravity crude oils will play an ever more important role in supplying world refineries. And prices promise to remain high because gainsayers notwithstanding, Hubbert ...

  • Designing deepcut vacuum units that really work

    Every barrel of vacuum gas oil (VGO) you can save from being reduced to coke in the delayed coker unit is a barrel more that can go to the FCCU. That’s a good reason to raise HVGO cutpoint. But how to do it? Some people think the job can be done just by running computer models in the engineering ...

  • A time for grass roots thinking ?

    Within the past year or two spiking crude prices and surging refinery margins have led to overheated talk about increasing refinery capacity worldwide. Plans for construction of as many 60 grass roots refineries have been discussed. But stretched out lead times for major equipment and inflated prices, ...

  • A single integrated vacuum system

    Failure to design the vacuum unit as an integrated system will invariably result in unsatisfactory yield and poor product quality (high vanadium, nickel, microcarbon, or asphaltenes), and ultimately, an unscheduled shutdown. To avoid these revamp problems the charge pump, fired heater, transfer line, ...

  • Is pinch enough?

    Back in the late 1970’s and early 1980’s when fuel gas prices were high, energy utilization assumed major importance. A new method of calculating heat exchanger networks was developed. It was called Pinch Technology. Today pinch has been rediscovered by engineers who have access to fast computer ...

  • Opportunity knocks

    A group of interesting articles* deals with opportunity crudes, a mixed breed that includes very heavy, sour and high total acid number types as well as those with unexceptional naphthenic acid content but which do have significant concentrations of aliphatic acids or possess the ability to generate ...

  • Processing heavy Canadian crude

    Reducing crude oil cost is the major incentive driving crude and vacuum unit projects to handle heavy Canadian crudes. But such crudes–Albian Heavy, Christina Lake, MacKay River and others derived from oil sands–today present refiners with a unique set of problems not just because of extra-low ...

  • Why do many crude/vacuum units perform poorly?

    In many cases it’s because the original design was based more on virtual than actual reality. There is no question: computer simulations have a key role to play but it’s equally true that process design needs to be based on what works in the field and not on the ideals of the process simulator. ...

  • Why produce diesel from the vacuum unit?

    Look ahead five years. The economy is likely to keep tightening and the rush to control pollution will inevitably be accompanied by demands for greater energy conservation. Consequence? A growing market for diesel which yields more energy per unit volume. Yet many continue to believe that producing diesel ...