Process Description
PMDA Production
PMDA production begins with a set of batch reactors in which
Formaldehyde, Aniline (in excess), and HCl solution are added to the reaction
vessel and the subsequent reaction to benzylamine. The benzylamine
solution is then forwarded to an isomerization tower where the rearrangement
takes place to form methylene dianiline (MDA).
The methylene dianiline solution is then forwarded to neutralization where the HCl
is neutralized with NaOH and then to separation of the two liquid phases. The organic
phase containing the neutralized methylene dianiline is then washed in a
Graesser contactor to minimize residual salts formed in neutralization and then
forwarded to the aniline stripper where they are process under vacuum for removal
of excess aniline and any residual water remaining from the wash step.
CO Production
CO is produced in the CO plant by reacting Methane with O2 and the
subsequent purification of the CO to remove CO2 and other by-products. The
purified CO is then fed to the phosgene reactor.
Cl2 Purification
Chlorine is received in railcar and purified to remove and heavy
compounds. The excess Cl2 and heavy compounds are then absorbed to produce Sodium
Hypochlorite. The purified Cl2 is then fed to the phosgene reactor.
Phosgene
Phosgene (COCl2) is produced by stoichiometric mixing CO and Cl2 with
a slight excess CO (10% molar) through a carbon bed and subsequent purification to
remove the excess CO. The phosgene is then condensed into a double walled vessel for
feeding to the Phosgenation reaction step.
PMDI Production
(Phosgenation, HCl Gas Purification, Solvent Recovery & Solvent Purification)
PMDA is mixed with monochlorobenzene (MCB) as a solvent and fed to the
Primary Phosgenation Reactor. The fresh COCl2 is mixed with recycled COCl2 and
fed to the Primary Phosgenation Reactor. The Phosgenation reaction process
consists of four continuous stirred tank reactors (CSTR抯) in series. The phosgenation
product slurry is then forwarded for phosgene and MCB removal. The HCl/Phosgene stream
then goes through HCl Gas Purification where the HCl is taken as a purified
overhead stream and the COCl2 is absorbed in MCB and then overhead distilled back to be
recycled to be mixed with fresh COCl2 and fed to the Primary Phosgenation Reactor.
MCB is subsequently processed to remove any heavies and recycled back to mix
with the PMDA. The purified phosgenation product (PMDI) is then ready for separation.
HCl Solution
The purified HCl gas is absorbed in water for use in PMDA production
and excess HCl is sold to customers.
MMDI Production
(MDI Evaporation, Crystallization, Distillation)
PMDI is fed to MDI evaporation where a crude MMDI is vaporized and fed
to Crystallization. The product of Crystallization is Pure MMDI and
mother liquor; the mother liquor can be fed to distillation to produce additional MMDI
and high op to use and sales. The bottoms liquid from MDI evaporation (PMDI) and the op
streams produced then go to Storage & Blend.
Uretone Imine
Uretone Imine is made in a batch reactor using a catalyst that is
subsequently deactivated with an active chloride.
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