Hi there, and welcome to this lecture on process flow diagram equipment summary tables. My
name is Marina Miletic. Over the past few lectures, we've discussed the required tables
which supplement every process flow diagram. We've looked at stream or flow summary tables,
as well as utility stream or utility summary tables, but there's another critical table
which must be provided as a supplement to every process flow diagram, and that's an
equipment summary table. Equipment summary tables provide critical physical characteristics
for each piece of equipment that has a letter and number designation on a process flow diagram.
This information includes the type of equipment, the equipment's height, width, volume, or
area, its power output or generation, the material the equipment is constructed of,
the incoming and outgoing temperature and pressure, among other information. This information
is critical because it enables us to look in books, catalogs, call distributors, or
use price estimation software to determine not only the initial cost of purchasing that
piece of equipment, but also the cost of running it. Recall that these costs are instrumental
in determining the initial and ongoing expenses of the process, and if these outweigh the
money generated from selling the product, then the project should not be continued.
This is an equipment summary table for the ethylene oxide production process. Some equipment
is listed in groups. For example, compressors, turbines and pumps are all listed together,
and the same is true for vessels, towers and reactors. However, heat exchangers and fired
heaters are grouped by themselves. Every piece of equipment with a letter and number designation
on the process flow diagram is described in this table. Let's start with compressors,
turbines and pumps, and look at the information you should provide for these units. One of
the first pieces of information you should provide is type. Though there are many choices,
there are 4 general types of turbines, compressors, and pumps: axial, centrifugal, reciprocating,
and rotary. Axial is the most common type of compressor and turbine for large chemical
processes with high flowrates. Centrifugal is the most common pump type used in large
chemical processes. In almost all cases, this design is the cheapest, most efficient way
of increasing the pressure of liquids for low viscosity, high flowrate applications.
Reciprocating compressors and pumps usually use pistons connected to a crankshaft to increase
pressure through back and forth motion. Reciprocating compressors, pumps and turbines are also sometimes
called positive-displacement, and they're typically used for smaller applications requiring
minimal space and involving low flowrates. Rotary compressors or pumps usually compress
by physically shrinking the size of the gas or liquid cavity, forcing the fluid into a
smaller volume using some form of rotation. Rotary compressors or pumps are also sometimes
referred to as positive-displacement, and are frequently used when high viscosity or
non-Newtonian fluids need to be pressurized. Something that surprises most students is
that CHEMCAD or Aspen will not select a compressor, turbine or pump type for you. I suggest you
look in a design book and determine the best type based on the flowrate, the horsepower
required to run the compressor or pump, the inlet and outlet pressure of the process stream,
and the price. For this ethylene oxide process, I chose reciprocating for the compressors
because it is the cheapest for their power requirement, axial for the turbine because
almost all turbines are an axial design, and centrifugal for the pump because it's the
most efficient and cheapest for the flowrate and the power required. Once you've selected
a compressor or a pump type, it's important to select the drive type. The drive is what
actually creates the motion which runs the compressor or pump, and enables it to pressurize
the fluid. Recall that turbines actually extract energy from a fluid through depressurization.
Instead of having the fluid having work done on it, here the fluid is doing the work to
create rotation or movement, so because energy is not being added to the fluid but instead
being removed, turbines don't have drives. There are four main types of drives you can
choose: electric, steam turbine, gas turbine, or internal combustion engine. Let's start
with the most common, electric drive. Many process compressors and pumps are run using
an electric drive, more commonly referred to as an electric motor. Electric motors are
the most common drive type in most chemical processes because they have high efficiencies
and work well when the power requirement is 100 horsepower or lower. Steam turbines create
motion by sending steam through a turbine, which generates rotation, which is then used
to run the pump or compressor. Though they're less efficient than electric motors, steam
turbines are useful when the power requirement for a pump or compressor is greater than 100
horsepower, and during power outages to keep the process running. Gas turbines differ from
steam turbines in that instead of sending steam through the expander, some other gas
or vapor is used. The disadvantage with gas turbines is that they tend to be very inefficient
and expensive, but they may pay for themselves in the case where a high flowrate gas stream
would need to be depressurized anyway. In this case, if enough power is generated, gas
turbines are well worth the initial and ongoing cost. Lastly, internal combustion engines
combine a fuel such as diesel or gasoline with air and compresses the mixture, then
combusts it, usually in a piston and cylinder system. Internal combustion engines are sometimes
used to run pumps or compressors in remote areas, or where availability to electricity
is intermittent. The disadvantage of using them is that they tend to be very inefficient,
since a lot of energy is lost to heat, and the fuel source always needs to be replenished.
So to select the best drive type, consider the horsepower required by the pump or compressor.
Remember that electric drives are typically more efficient than steam turbines, which
are more efficient than gas turbines and internal combustion engines, and try to find the option
which results in the lowest long-term cost. You can find estimates of power ranges, efficiencies,
and prices in most process design books. Because of their high efficiency and low cost, I chose
electric drives for these compressors and the pump. Remember that turbines do not require
a drive because they are used to depressurize or extract work from a fluid. This is why
there is no drive type selected for turbine C-103.