Page 38 - Analysis, Synthesis and Design of Chemical Processes, Third Edition

fluctuates wildly at certain times, making control of the process difficult. Because of the frequent
problems with this exchanger, it is recommended that E-102 be replaced by two separate heat exchangers.
The first exchanger cools the effluent gas and generates steam needed in the plant. The second exchanger
uses cooling water to reach the desired exit temperature of 38°C. These exchangers are to be designated
as E-107 (reactor effluent boiler) and E-108 (reactor effluent condenser).

The E-102 designation is retired and not reassigned to the new equipment. There can be no mistake that
E-107 and E-108 are new units in this process and that E-102 no longer exists.

1.2.2 Stream Information

Referring back to Figure 1.3, it can be seen that each of the process streams is identified by a number in a
diamond box located on the stream. The direction of the stream is identified by one or more arrowheads.
The process stream numbers are used to identify streams on the PFD, and the type of information that is
typically given for each stream is discussed in the next section.

Also identified in Figure 1.3 are utility streams. Utilities are needed services that are available at the
plant. Chemical plants are provided with a range of central utilities that include electricity, compressed
air, cooling water, refrigerated water, steam, condensate return, inert gas for blanketing, chemical sewer,
waste water treatment, and flares. A list of the common services is given in Table 1.3, which also
provides a guide for the identification of process streams.

Table 1.3 Conventions for Identifying Process and Utility Streams