Page 268 - Design of Simple and Robust Process Plants

254 Chapter 7 Optimization of an Integrated Complex of Process Plants
production chain. A combination of refineries and hydrocarbon plants, for example
in olefin production by cracking all kinds of refinery streams, is quite common. All
the above complexes have product chains with forward and backward integration. If
the customer product processes (e.g., polymer processes) form part of the complex,
they depend heavily on specific markets and the distribution costs. Likewise, poly-
ethylene processes are often sited at a larger complex due to the relative high distri-
bution costs of ethylene. Latex and foam products are often produced close to the
market due to the high transportation cost of the products.
The primary reasons for building integrated complexes are, first, to benefit from
site logistics, where intermediate products can be moved from one process to the
next at very low cost. In such cases, a dedicated line and a pump are often sufficient.
Other benefits are achieved by taking advantage of energy integration with a site-
wide utility system, while water integration and hydrogen integration might also be
attractive options. Sharing facilities such as docks, rails, roads with (un)loading provi-
sions can beneficial. One other advantage may be the utilization of intermediate
product streams or side streams, which have a lower (mostly noncommercial) specifi-
cation. These specific product streams are often much cheaper for the producing
plant. The receiving plant might separate the desired material stream from its impu-
rities at low cost, as that specific separation has already been provided in the process.

7.3
The Design Philosophies of Integrated Complexes

An integrated chemical complex has as its objective the achievement of lower
production costs compared with that of isolated plants. This is realized by minimiz-
ing the logistics and processing cost of process plants, while maintaining the avail-
ability of the product streams at a high level. The vulnerability of such a complex
requires careful quantification and evaluation to achieve the maximum benefits of
integration.
In order to assure operational flexibility of an integrated complex, the following
design philosophies are introduced:

. A failure or stop of a plant should not result in the immediate outage of other
plants; this can be seen as clever integration on a site bases.
. The utility generation for a complex should be designed with an optimized
level of redundancy, to minimize common cause failures of plants.
. Common cause failure of each utility system should be evaluated as part of
reliability of the system.
. Simultaneous outages of more than one utility system should be avoided by
designing the systems independently.
. The impact of utility outages should be minimized by the design of load-
shedding systems; this might include power, steam, and others.
. The vulnerability of the complex should be quantified, and alternatives evalu-
ated based on cost±benefit analysis.