Reference Manual

10B −11
— Q = 9000 gpm
D Typical valve selection:
— This valve is specified as a full bore ball
valve by Kamyr, and is referred to as the
RO1 valve. It is normally open, and only
closed when the digester must be isolated
from the HP feeder. NPS 12 to NPS 16 in
size with additional 1/8 inch thickness on RF
male flange.
— This unique size makes this valve a
non-ANSI flange thickness. Fisher does not
have an offering available for this valve.
Valve: HV-51 Top circulation isolation
valve
This is an isolation valve for liquor being sent back
to the high pressure feeder from the impregnation
vessel.
D Typical valve selection:
— This valve is specified to be a full bore
ball valve by Kamyr, and is referred to as the
RO2. It too has the special “male flange”
requirement as referenced in HV-52.
Valve: PDV-18 Digester outlet device
differential pressure
This valve adds liquor to the bottom of the digester
to assist in chip discharge and to help regulate
consistency.
D Typical process conditions:
— Fluid: Washer filtrate
— T = 170_F
— P = 238 psig
— dP = 45 psi
— Q = 100 – 1000 gpm
D Typical valve selection
— This is typically a NPS 4 valve for which
Kamyr has specified a V300 valve with
stainless steel body and ball. The valve
should be offered with a Nitronic 50 shaft,
PEEK bearings, and an HD metal seal. A
piston actuator is normally specified.
Impregnation
The chips at the top of the column now enter the
liquor impregnation zone. In this zone, chips are
subjected to a complete soaking or penetration of
the cooking liquor at a temperature of
approximately 250_F. The impregnation stage
lasts about 45 to 60 minutes at design tonnage. It
is important that thorough penetration takes place
before the heating stage. If penetration is
incomplete, chips with uncooked centers will
result.
The white liquor, or cooking liquor, is added to the
digester together with black liquor, which is
recovered from the chip chute overflow. It is also
possible to put weak black liquor into the makeup
liquor pump suction, but this is normally not
required.
The chip chute overflow goes to the surge tank
(level tank). There, it is controlled at a constant
level, and then goes to the make-up liquor pump
where it is combined with the white liquor. The
make-up liquor pump transports the mixture to the
top of the digester and injects it at a point just
below the top separator. All of this liquor returns to
the high pressure feeder by the top circulation
return line, and is mixed with fresh chips to be
returned to the inside of the top separator and
then to flow down the digester. The amount of
white liquor added is based upon the production
rate and is in direct proportion to the chip feed
rate.
Valve: TV-3A White liquor to make-up
liquor line temperature
D Typical process conditions:
— Fluid: White liquor
— T = 120_ F
— P = 55 psig
— dP = 10 psi
D Typical valve selection:
— This valve has been specified by Kamyr
to be a NPS 3 V150 valve with stainless
steel body and 317 stainless chrome plated
ball, Nitronic 50 shaft, HD metal seal, PEEK
bearings, and a fail-close actuator.
Valve: FV-4 Black liquor flow
This valve only sees infrequent use in the process.
Its function is to add cool washer filtrate liquor to
the black liquor line coming from the level tank in
the event the black liquor and the temperature at
the top of the digester exceed specified
temperature limits.
D Typical process conditions:
— Fluid: Washer filtrate
— T = 180_F
— P = 30 – 60 psig
— dP = 10 – 60 psid