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In the past, when two different rooms containing either chlorine or sulfur dioxide
had to be evacuated, automatic louvers were installed that block the gas flow from
the opposite room from where the leak occurred. Since the standard airflow of the
Sentry 2000 is 3000 ACFM, it is possible to use manual dampers to each room and
balance the flow rate of gas from each room. The engineer can choose any flow rate
desired from each room such as 2000-CFM to the storage room and 1000-CFM to the
evaporator room. The elimination of automatic dampers will reduce to initial cost
of the ductwork system and remove a potential source of failure during the chlorine
or sulfur dioxide leak.
System Flow Rates
The basic system is rated at 3000 ACFM. If an application should require additional
gas flow to the scrubber for any reason, the Sentry 2000 can be increased in flow
rate with calculated results. The packed bed portion of the system will increase
in height based on the required flow rate, but the total length and width of the
unit will not change with the normal inlet conditions as specified by the UFC. Scrubber
flow rates can easily be increased to 4500-5000 CFM. The fan horsepower of the system
will increase to 10 hp. Cost of the system will increase approximately 15% depending
on the type of system specified. This additional cost may be saved by the elimination
of automatic louvers and the required electrical components.
System Ventilation Capability
Since the caustic is stored in the sump and the caustic recycle pump does not need
to run when the scrubber fan is operating, the system can be used for ventilation
of many of the chlorine and sulfur dioxide rooms. The fan can be turned on when
personnel are in the room or run continuously. Airflow can be adjusted by manual
or automatic louvers if required. When the chlorine or sulfur dioxide detector system
turns on and starts the scrubber pump, the system will wet the packing and the gas
will be scrubbed.
In warm climates this approach will work very well. Using this feature can eliminate
a primary ventilation system that adds additional cost to the project.
The standard scrubber system will need a containment dike for the caustic in case
of a leak. We offer a true double containment tank system that will eliminate the
need for the containment dike. Only a concrete pad will be required. This system
will be extremely useful in modification of existing buildings for the addition
of the chlorine scrubber.
In addition, the double containment system with the top mounted pumps will eliminate
the need for pump seals, water flushing of the seals and freeze protection of the
water flush if a seal pot is not used. Refer to a typical specification for details.
Safety Relief Vents from Evaporators
In the past, the safety relief vents from evaporators have been piped to the atmosphere
outside the storage room. Currently many applications will require that the safety
valves be piped to the scrubber. One of the options on our system installs a sparger
tube into the caustic storage tank on the side near the bottom of the storage vessel.
If the safety valve system is piped to the scrubber, it should be piped through
a barometric loop with an air purge as recommended by the Chlorine Institute Inc.
Pamphlet #9. Many engineers will eliminate the barometric loop due to height constraints
of the building. Please refer to the Powell sparger drawing in this section for
Vent to Storage Room Scrubber Inlet
In lieu of venting the relief valves to the scrubber sparger, many engineers are
terminating the vents to the inlet duct area of the scrubber in the container storage
room. If the safety valve should relieve into the containment room scrubber inlet
ductwork, the gas detector will turn on the scrubber and scrub the gas. The main
concern with this approach is employee safety during the time of release and scrubber
operation if the employee is in the area.
Vacuum Relief Vents
In the past, the vacuum relief vents have been piped to the atmosphere. Many engineers
are now piping these vents to the area near the scrubber inlet ductwork in the containment
For more technical information about sodium hypochlorite,
visit the Technical Information section. This article is available
in PDF format.
Click here to download it.