Page 45 - Chemical Process Equipment - Selection and Design

20 FLOWSHEETS

Net Fuel Gas 71 83
I c
Sulfur Sulfur
Recovery

Recovery
Primary r-7 Steam + Phenols 2380
I
Steam
Net Waste Liquids
Net Waste Liquids
2380
Carbonizer Primary
Fractionator
Fractionator
Coal
Coal
100,000
Light Aromatics
770
100,000 22,500 Oils Light Aromatics 770
Oils
Recovery
Recovery
Air
Air I I
I I Middle Oils (diesel, etc.) 12575
Middle Oils (diesel, etc.)
12575
Tar Acids 3320
Distillation t Heavy Oils (creosote, etc.) 2380
Pitch
I 1
1 Pitch 3000
Char 77500
Figure 2.1. Coal carbonization block flowsheet. Quantities are in lb/hr
compressed air, fuel, refrigerants, and inert blanketing gases, and Since a symbol does not usually speak entirely for itself but also
how they are piped up to the process equipment. Connections for carries a name and a letter-number identification, the flowsheet can
utility streams are shown on the mechanical flowsheet, and their be made clear even with the roughest of equipment symbols. The
conditions and flow quantities usually appear on the process
flowsheet.
Since every detail of a plant design must be recorded on paper,
many other kinds of drawings also are required: for example, TABLE 2.1. Checklist of Data Normally Included on a
Process Flowsheet
electrical flow, piping isometrics, instrument lines, plans and
elevations, and individual equipment drawings in all detail. Models 1. Process lines, but including only those bypasses essential to an
and three-dimensional representations by computers also are now understanding of the process
standard practice in many design offices. 2. All process equipment. Spares are indicated by letter symbols or
notes
3. Major instrumentation essential to process control and to
2.5. DRAWING OF FLOWSHEETS understanding of the flowsheet
Flowsheets are intended to represent and explain processes. To 4. Valves essential to an understanding of the flowsheet
make them easy to understand, they are constructed with a 5. Design basis, including stream factor
6. Temperatures, pressures, flow quantities
consistent set of symbols for equipment, piping, and operating 7. Weight and/or mol balance, showing compositions, amounts, and
conditions. At present there is no generally accepted industrywide other properties of the principal streams
body of drafting standards, although every large engineering office 8. Utilities requirements summary
does have its internal standards. Some information appears in ANSI 9. Data included for particular equipment
and British Standards publications, particularly of piping symbols. a. Compressors: SCFM (6OoF, 14.7 psia); APpsi; HHP; number of
Much of this information is provided in the book by Austin (1979) stages; details of stages if important
along with symbols gleaned from the literature and some b. Drives: type; connected HP; utilities such as kW, Ib steam/hr, or
engineering firms. Useful compilations appear in some books on Btu/hr
process design, for instance, those of Sinnott (1983) and Ulrich c. Drums and tanks: ID or OD, seam to seam length, important
internals
(1984). The many flowsheets that appear in periodicals such as d. Exchangers: Sqft, kBtu/hr, temperatures, and flow quantities in
Chemical Engineering or Hydrocarbon Processing employ fairly and out; shell side and tube side indicated
consistent sets of symbols that may be worth imitating. e. Furnaces: kBtu/hr, temperatures in and out, fuel
Equipment symbols are a compromise between a schematic f. Pumps: GPM (60°F), APpsi, HHP, type, drive
representation of the equipment and simplicity and ease of drawing. g. Towers: Number and type of plates or height and type of packing;
A selection for the more common kinds of equipment appears in identification of all plates at which streams enter or leave; ID or
Table 2.2. Less common equipment or any with especially intricate OD; seam to seam length; skirt height
configuration often is represented simply by a circle or rectangle. h. Other equipment: Sufficient data for identification of duty and size