Chemical Engineering August 2018 - 35

Technology Profile
Ethylene Dichloride Production
By Intratec Solutions
E
thylene dichloride (also
known as 1,2-dichloroethane,
as well as EDC and
DCE) is by far the most
widely produced chlorinated hydrocarbon.
The vast majority (~95%)
of EDC is employed in the manufacture
of vinyl chloride monomer
(VCM), which is in turn mostly used
as the starting material for the plastic
polyvinyl chloride (PVC). EDC
can also be used as an intermediate
in the production of chlorinated
solvents, such as trichloroethylene,
ethylene amines, vinylidene chloride
and trichloroethane.
The process
The following describes a process for
EDC production from ethylene and
chlorine. Figure 1 presents a simplified
flow diagram of the process.
Direct chlorination.
In the direct
chlorination step, chlorine and ethylene
are fed to a high-temperature
chlorination (HTC) reactor filled with
liquid EDC as the reaction medium.
Heat from the highly exothermic reaction
is removed by boiling off EDC,
and by the circulation of EDC, which
is recycled from the product column
downstream. Ferric chloride (FeCl3)
is used as a catalyst. About 99%
of the ethylene and almost 100%
of chlorine are converted, with high
selectivity, to EDC. Unavoidable side
reactions generate polychlorinated
compounds as byproducts (mainly
1,1,2-trichloroethane). Among the
byproducts, those with boiling points
higher than EDC are primarily withdrawn
from the bottom of the reactor
as a liquid stream. The gaseous effluent
from the chlorination unit, containing
the EDC product, is routed to
the purification steps downstream.
Product column. In this area, the
gaseous effluent, rich in EDC, is
passed through a heat exchanger,
where it generates steam while being
partially condensed by boiler
feedwater. The EDC-rich stream
is then fed to a distillation column,
where it is purified by separating residual
byproducts. The stream withdrawn
from the column overhead
is then cooled in a cooling water
condenser, yielding a liquid stream
composed
of EDC 99.5
wt.%,
which is pumped to the EDC tank.
Non-condensed gases - mainly
ethylene, nitrogen, chlorine, HCl
and residual water and EDC - are
then passed through a second condenser
using refrigerant fluid. After
this second condensation step, uncondensed
gases are routed to an
incinerator located outside battery
limits. The column bottom product
composed of EDC and polychlorinated
compounds is recycled to the
direct chlorination reactor. Part of
this stream is purged to avoid the
buildup of impurities.
EDC tank. The EDC product is
stored in intermediate tanks before
it is directed to storage facilities located
outside battery limits.
Production pathways
Ethylene dichloride production
routes are primarily based on the
CW RF
BFW
3
1
Chlorine
Ethylene
2
ST Steam
CW
ST
RW
Heavy ends
Heavy ends
FIGURE 1. The process diagram shown here illustrates the production of ethylene dichloride from ethylene and chlorine
CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM
AUGUST 2018
33
6
5
7
BFW Boiler feed water
CW Cooling water
RW Refrigerated water
EDC
4
Offgas
Economic performance
The total operating cost (raw materials,
utilities, fixed costs and depreciation
costs) estimated to produce
EDC was about $510 per ton of EDC
in the second quarter of 2014. The
analysis was based on a plant constructed
in the U.S. with capacity to
produce 500,000 metric tons per
year of EDC.
This column is based on " Ethylene
Dichloride from Ethylene and Chlorine, "
a report published by Intratec.
It can be found at: www.intratec.us/
analysis/edc-e11a.
n
Edited by Scott Jenkins
Editor's note: The content for this column is supplied
by Intratec Solutions LLC (Houston; www.intratec.us) and
edited by Chemical Engineering. The analyses and models
presented are prepared on the basis of publicly available
and non-confidential information. The content represents
the opinions of Intratec only. More information about the
methodology for preparing analysis can be found, along with
terms of use, at www.intratec.us/che.
1. Chorination reactor
2. Product column
3. EDC tank
4. Incinerator
5. Steam boiler
6. Cooling tower
7. Chiller
Ethylene,
chlorine
Direct
chlorination
Ethylene
dichloride
Ethylene,
hydrogen
chloride, oxygen
n Raw material n Process n Main product
FIGURE 2. There are two main production pathways
for EDC
chlorination of ethylene: direct chlorination
by chlorine or oxychlorination
by hydrogen chloride. Figure 2
presents these two different pathways
for EDC production.
Oxchlorination

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Chemical Engineering August 2018

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