Reference Manual

10B −4
Figure 10B-2. Steaming Vessel
E1215
— dP = 50 – 60 psid
— Q = 2900 – 5000 lbs/hr
D Typical valve selection:
— This is specified by Kamyr as a NPS 8 to
NPS 10 Fisher Vee-Ballt V150 valve, and
could need an attenuator. Carbon steel body
material has been used successfully,
although stainless steel would provide an
added level of durability. HD metal seats are
specified with PTFE packing, PEEK
bearings, and Nitronic 50 shafts.
Valve: TV-4 Fresh steam to chip bin
This valve provides hot water to the chip bin.
D Typical process conditions:
— Fluid: Hot water
— T = 312_F
— P = 230 psig
— dP = 135 – 145 psi
D Typical valve selection:
— This valve is specified by Kamyr as a
NPS 1/2 globe valve with a 300 lb. rating. A
reduced port may be needed depending
upon flow requirements. A carbon steel body
is suggested with 316 SS equal percentage
trim.
Pre-steaming and Conditioning
The steaming vessel is a normally horizontally
mounted cylinder with an internal screw conveyor
for carrying chips along from the low pressure
feeder through steam to the next stage. Its main
functions are to remove gases and air from the
chips, raise the temperature to approximately
250_F, and bring the chips to a more uniform
moisture content. A secondary aim is to maintain a
pressure balance in the feeding system. This
means that the steam pressure (15-18 psig) in the
steaming vessel must always be higher than the
vapor pressure of the liquor in the top circulation
line so that the latter does not start to boil when it
leaks back into the chip chute low pressure area.
Removal of air and gases enables the cooking
liquor to penetrate the chips more easily.
The steam is supplied from two sources: flash
steam from the No. 1 flash tank and from a fresh
make-up low pressure steam header.
In order to obtain an effective pre-steaming, the
steam is introduced at the bottom of the steaming
vessel (bottom steaming). There are no controls
on the steam from the flash tank as it is
dependent upon extraction flow from the digester.
The venting of exhaust and non-condensable
gases controls the amount of fresh steam usage.
The exhaust line is equipped with a screen that
prevents sawdust and fine particles from being
carried into the heat recovery area.
After passing through the steaming vessel, the
chips fall from the end of the screw conveyor,
down a chute known as the chip chute, into a pool
of liquor. At this point, the chips start to absorb
liquor. An inspection port is provided on the
steaming vessel for the monitoring of the flow of
chips into the chute.
The chip chute is a vertical pressure vessel with
an internal slotted screen plate. It sits directly on
top of the high pressure feeder. The liquor in the