Chemistry Reference
In-Depth Information
technology arises for so-called 'enabling technology', which opens up themanufacture of new
products, allows a major reduction in investment and operating costs or facilitates a superior
product specification. An example of such a PI application is Dow's process for producing
low-chlorides hypochlorous acid (HOCl) [4]. Another compelling reason to accept a PI item is
debottlenecking of a plant. Size may then be decisive: it is obviously an attractive project to
debottleneck a 200million GBP plant by say 5-10% for a marginal investment, but the
situation might be different if the process plant is small and batch-orientated.
A shutdown in a batch plant is less dramatic as it will be partially stopped and started at
short intervals anyway. There are also often many parallel units to keep other plant items in
continuous operation. In such a setting, it is easier to accept new equipment, possibly with
moving parts, even when it has a risk level that is not proven by previous long operation.
In general, there has to be a significant upside in order for investors to accept PI
technology. Savings on the cost of an individual piece of equipment are very marginal. It
has to be remembered that the equipment cost in a plant is in the order of 25% of the plant's
erected cost. Hence any saving in a process item is only a saving in a quarter of the total
cost. There are much bigger savings to be had if the PI technology proposed also reduces
the cost of the remaining 75%, for example by reducing the support structure needed,
avoiding piling operations, combining two process functions in the same apparatus and so
on. Even so, it might be difficult to argue the point in a multi-unit process train. If a new unit
were to enable a noticeable energy saving, it might be easier to convince investors. Such an
energy saving could for instance come about if a reactor were to produce a product with
fewer byproducts, thereby simplifying the ensuing distillation train. Again, the power of
enabling new products or superior specifications must be emphasized.
Time to market in a batch plant that produces high-value chemicals or pharmaceuticals
has been discussed in PI meetings in the past. Clearly an increase in the time available to
exploit a product advantage before patent expiration is very valuable, and bringing the cash
flow forward is not negative either.
Small equipment items may in themselves represent enabling technology by allowing
retrofitting of new process functions or debottlenecking when space is a challenge. Space is
usually a problem in any existing plant. For example, it might be prohibitive to add a gas-
treating function to an oil and gas platform using conventional technology, but a small unit
might be squeezed in.
HiGee has been a spectacular example and probably the flagship of the PI community. It
has, however, not been the huge commercial success that was visualized 25 years ago.
There are successful applications about, such as Dow's [4] and de-aeration plants in China
[5], but the major breakthrough has not come, and presently there is no active marketing of
the unit. In the main, it could be said that the battle against risk aversion has been lost. The
applications attempted have certainly been associated with conservative process environ-
ments [6,7]: these were demonstration projects in which HiGee was used to treat natural
gas. The first demonstration was for selective absorption of H
2
SoverCO
2
, where a short
residence time is important. The second was of CO
2
capture and water removal from
natural gas. Both demonstration projects were claimed to be successful. Removal targets
were met, and HiGee operated successfully.
PI is much more than HiGee and the other items usually talked about in the PI community,
however. One example not usually put forward is the transport of powder. In earlier days this
was dominated by belt conveyers. Today, more often than not the powder is fluidized and
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