Page 161 - Design of Simple and Robust Process Plants

146 Chapter 5 Process Simplification and Intensification Techniques
. direct feed to customers;
. storage of base products only, and by feeding additives during loading or at
the customer; and
. production directly into transportation containers.
Optimal sizing of storage volumes based on probabilities in the overall supply lines,
from receipt of the raw material until delivery to the customer, is discussed in
Chapter 7.
By comparing the batch process in Figures 1.4±1.7 in Chapter 1, it is possible to
see all the above-mentioned options. In the ultimate concept, all tanks are removed
from raw material storage, mix feed tanks, lot tanks and product tanks, while trans-
port containers are added for the product and additives. Elimination of these facil-
ities is not a unique situation; all related equipment is also eliminated, such as
pumps, mixing devices and instruments, as well as safety provisions and various
operational aspects.

5.2.2
Transport of Fluids

In the case of liquids, the standard solution is to use pumps. However, it should be
noted that pumps these might be subject to elimination by using:

. gravity flow; or
. pressure difference
Although these options are well known, they are applied only in limited circum-
stances. Only in cases of extreme competition between technology suppliers are
these options regularly exploited on a competitive basis. Plants such as nitric acid or
nitration processes are designed commercially to include a minimum number of
pumps. This saves on rotating equipment, contributes to reliability, and also often
leads to compact process designs. Gravity flow solutions must utilize all liquid head
available, and this drives for shorter lines and compact building. The direct dosing
of a neutralizer is a simple example (see Figure 3.7 in Chapter 3).
Pressurization of the additive containers can be used to avoid pumps and mixing
stations if the additives are delivered at the composition required for the process.

5.2.3
Recovery Systems

These are designed to cope with waste gas and water streams. Such systems might
be avoided or greatly reduced either by eliminating the large sources of pollutant(s)
or reducing carriers such as nitrogen and water flows (see the visionary document
about 21st century plant; Natori and O'Young, 1996). Re-design of the safety provi-
sion of a NH 3 storage tank (Figure 3.5 in Chapter 3) is a good example of avoiding a
release system.