Page 63 - Chemical Process Equipment - Selection and Design

7. DETERGENT MANUFACTURE 35
the evaporator proceeds beyond the battery limit for further mixture is pumped during the course of the reaction through an
purification. Evaporator bottoms proceeds to waste disposal. The external heat exchanger (entering at -10°F and leaving at -15°F)
aqueous phase from decanter V-103 is pumped with P-109 through a which is cooled with ammonia refrigerant (at -25°F) from an
feed-bottoms exchanger E-104 to the top tray of the brine tower absorption refrigeration system (this may be represented by a block
D-102. The overhead is condensed in E-105, collected in on the FS); the exchanger is of the kettle type. HCI gas is injected
accumulator V-104 and pumped beyond the battery limits for into the recirculating stream just beyond the exit from the heat
recovery of the phenol. Tower D-102 is provided with a steam exchanger; it is supplied from a cylinder mounted in a weigh scale.
heated reboiler E-106. Bottom product is a weak brine that is The aluminum chloride forms an alkylation complex with the
pumped with B-110 through the feed-bottoms exchanger and toluene. When the reaction is complete, this complex is pumped
beyond the battery limits for recovery of the salt. away from the reactor into a storage tank with a complex transfer
Two important control instruments are to be shown on the pump. To a certain extent, this complex is reused; it is injected with
flowsheet. These are a back pressure controller in the reactor its pump into the reactor recirculation line before the suction to the
effluent Line beyond exchanger E-101 and a pH controller on the recirculation pump. There is a steam heater in the complex line,
feed line of the 5%HC1 that is fed to springer R-102. The pH between the reactor and the complex pump.
instrument maintains proper conditions in the springer. The reaction mixture is pumped away from the reactor with an
Note: There is a tendency to byproduct diphenyl ether alkymer transfer pump, through a steam heater and an orifice mixer
formation in reactor R-101. However, a recycle of 100 pph of DPE into the alkymer wash and surge tank. Dilute caustic solution is
in the feed to the reactor prevents any further formation of this recirculated from the a.w.s. tank through the orifice mixer. Makeup
substance. of caustic is from a dilute caustic storage tank. Spent caustic is
intermittently drained off to the sewer. The a.w.s. tank has an
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A
6. ~ A ~ ~ F OF BLBTADlENE SULFONE internal weir. The caustic solution settles and is removed at the left
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of the weir; the alkymer overflows the weir and is stored in the
A plant is to manufacture butadiene sulfone at the rate of right-hand portion of the tank until amount sufficient for charging
1250 lb/hr from liquid sulfur dioxide and butadiene to be recovered the still has accumulated.
from a crude C, mixture as starting materials. Construct a flowsheet
for the process according to the following description. DISTILLATION
The crude C4 mixture is charged to a 70 tray extractive
distillation collum T-1 that employs acetonitrile as solvent. Trays Separation of the reactor product is effected in a ten-plate batch
are numbered from the bottom. Feed enters on tray 20, solvent distillation column equipped with a water-cooled condenser and a
enters on tray 60, and reflux is returned to the top tray. Net Dowtherm-heated (650”F, 53psig) still. During a portion of the
overhead prolduct goes beyond the battery limits. Butadiene distillation cycle, operation is under vacuum, which is produced by
dissolved in acetonitrile leaves at the bottom. This stream is a two-stage steam jet ejector equipped with barometric condensers.
pumped to a 25-tray solvent recovery column T-2 which it enters on The Dowtherm heating system may be represented by a block.
tray 20. Butadiene is recovered overhead as liquid and proceeds to Product receiver drums are supplied individually for a slop cut, for
the BDS reactor. Acetonitrile is the bottom product which is cooled toluene, light alkymer, heart alkymer, and a heavy alkymer
to 100°F and returned to T-1. Both columns have the usual distillate. Tar is drained from the still at the end of the operation
condensing and reboiling provisions. through a water cooler into a bottoms receiver drum which is
Butadiene from the recovery plant, liquid sulfur dioxide from supplied with a steam coil. From this receiver, the tar is loaded at
storage, and a recycle stream (also liquified) are pumped through a intervals into 50 gal drums, which are trucked away. In addition to
preheater to a high temperature reactor R-1 which is of the drums which serve to receive the distillation products during the
shell-and-tube construction with cooling water on the shell side. operation of the column, storage tanks are provided for all except
Operating conditions are 100°C and 30Qpsig. The combined feed the slop cut which is returned to the still by means of the still feed
contains equimolal proportions of the reactants, and 80% pump; this pump transfers the mixture from the alkymer wash and
conversion is attained in this vessel. The effluent is cooled to 70°C, surge tank into the still. The recycle toluene is not stored with the
then enters a low temperature reactor R-2 (maintained at 70°C and fresh toluene but has its own storage tank. The heavy alkymer
50 psig with cooling water) where the conversion becomes 92%. distillate tank connects to the olefinic stock feed pump and is
The effluent is flashed at 70°C and atmospheric pressure in D-1. recycled to the reactor.
Vapor product is compressed, condensed and recycled to the
reactor R-1. The liquid is pumped to a storage tank where 24 hr SULFONATION
holdup at 70°C is provided to ensure chemical equilibrium between Heart alkymer from storage and 100% sulfuric acid from the
sulfar dioxide, bufadiene, and butadiene sulfone. Cooling water is sulfuric acid system (which can be represented by a block) are
available at 32°C. pumped by the reactor feed pump through the sulfonation reactor.
The feed pump is a positive displacement proportioning device with
ETERGENT ~AN~FACT~~E a single driver but with separate heads for the two fluids. The
The process of making synthetic detergents consists of several reactor is operated continuously; it has a single shell with three
operations that will be described consecutively. stages which are partially separated from each other with horizontal
doughnut shaped plates. Each zone is agitated with its individual
ALKYLATIO impeller; all three impellers are mounted on a single shaft. On
leaving the reactor, the sulfonation mixture goes by gravity through
Toluene and olefinic stock from storage are pumped (at 80°F) a water cooler (leaving at 130°F) into a centrifuge. Spent acid from
separately through individual driers and filters into the alkylation the centrifuge goes to storage (in the sulfuric acid system block); the
reactor. The streams combine just before they enter the reactor. sulfonic acids go to a small surge drum or can bypass this drum and
The reactor is batch operated 4 hr/cycle; it is equipped with a single go directly to a large surge tank which is equipped with an agitator
impeller agitator and a feed hopper for solid aluminum chloride and a steam jacket. From the surge drum, the material is sent by an
which is charged manually from small drums. The alkylation extraction feed pump through a water cooler, then a “Aomix,” then