Page 28 - Microsoft Word - Sulfo and Sulfa 1.doc

through the process heat exchanger and a large portion of this stream recycles back to the
mixer. A pressure control valve allows product to leave the recycle system as feed
enters. A pH sensor is placed in the recycle line near the inlet to the mixer. The in-line
pH sensor measures an accurate pH on dilute slurries, and produces a single-valued
output signal that is proportional to pH on concentrated pastes. The signal from the
sensor feeds to the pH control system in either case, and controls the flow of the
neutralizing agent into the process. Use of a buffer promotes stability in the pH control
loop. Cooling water is also recirculated and automatically adjusted to maintain a desired
temperature at the process heat exchanger inlet. Therefore, higher melting point products
can be processed without plugging the heat exchanger during start-up.

Figure 25. Sulfonation System

EMERGENCY
SHUTDOWN DDB PURGE EFFLUENT
AIR
TANK GAS
RAW MATERIAL HOT
FEED WATER PROCESS
WATER
FILM DIGESTERS
REACTOR
CYCLONE

CWS

CWS
RECYCLE
CWR PUMP CWR
ACID FROM
ESP PRODUCT
ACID
DISCHARGE PUMP

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