The emergency chlorine vapor scrubbing system is a three-stage chemical absorption
system consisting of a horizontal cross flow spray system followed by two horizontal
cross flow packed bed sections.
An induced draft fan pulls vapors through the scrubber, where intimate contact with a
recirculating caustic solution results in the complete absorption and removal of
chlorine or sulfur dioxide vapors.
A high efficiency mist eliminator is located in the gas stream, prior to exhaust, to
remove any residual caustic solution. A chlorine detector or manual remote start
switch activates the system in two steps.
The caustic pump is activated first to permit proper wetting of packing in the
scrubber stages before starting the exhaust fan, with a 0 to 5 second adjustable
time delay. The time delay is typically set for 3 to 5 seconds. This feature allows
the scrubber to be ready prior to passing any chlorine laden gases through it.
The exhaust fan is placed downstream of the scrubber. This feature allows the
complete system to be under negative pressure until the gases are completely
scrubbed. The absorber is placed on top of a caustic storage tank, which is an
integral part of the system.
Scrubbing liquid is supplied to the motive inlet under pressure. As a result of the
large drop in liquid pressure across the nozzle, a high velocity liquid spray exits
the nozzle. This atomized liquid provides surface area for transfer of mass from the
gas to the liquid phase and allows for capture of particulates
from the gas phase due to impaction. In addition, the velocity of the liquid spray
creates a negative pressure which pulls gas into the Chlorine Scrubbers.
Working pattern of Emergency chlorine scrubber
The chlorine is neutralized using caustic solution. The unit is designed based on
risk analysis study to prevent release of chlorine directly into atmosphere.
The scenario considered are:
Instantaneous high flow rate
Chlorine concentration
Scrubbing efficiency
The chlorine concentration should be monitored continuously near the toner and should
be ensured that concentration is less than 3 ppm
Fusible plug worst case in the 900 kg toner
Melts at approximately 160 oF (71 oC)
Cl2 at 80 oF = 117 psia vapor pressure
Cl2 at 160 oF = 325 psia vapor pressure
34” diameter orifice = 437 lbs/min at 160 oF
Ton Container liquid plug empties ~ 5 minutes
437 lbs/min = 2380 scfm
Considering safety factor, suction air flow required is 3000 CFM to evacuate entire
chlorine gas from leakage area.
For 50 kg toner, considering safety factor, suction air flow required is 250 CFM to
evacuate entire chlorine gas from leakage area.
Chlorine Neutralization
In the scrubber system, Chlorine is neutralized by using sodium hydroxide and gives
by product of sodium hypochlorite and sodium chloride.
Cl2 + 2 NaOH —–à NaOCl + Nacl + H2O
Major Components in Scrubber
Chlorine sensor
FRP Capturing hood with actuated damper
FRP Ducting
FRP scrubber system
Caustic recirculation pumps
FRP blower
FRP exhaust chimney
Operation of scrubber system
One common duct will run along the length of chlorine storage area, chlorine tank
filling and loading area. Tonners containing chlorine will be connected online
with chlorine sensor. All the tonners will be provided with an online chlorine
gas monitoring system with hood to cover the toner, nozzle and connection
manifolds.
The hood part has bottom portion and top portion, of which top portion is
removable when it is required to change the toner. Whenever the chlorine tanks
are to be connected/removed from the online system, the top portion will be
removed and placed after keeping the toner. When both hoods, bottom portion and
top portion are placed, it creates a fully closed system, thus preventing the
chlorine escape out of hoods.
The electrically actuated damper will be provided for each hood, connected with
each toner. All the hoods are connected to main ducting line which is connected
to the scrubber. The damper is controlled by PLC based controller system. All
the dampers are in closed condition normally. When the chlorine gets leaked in a
particular toner, it will be detected by sensor and the signal will be sent to
PLC controller system. Then, automatically the damper of leakage toner hood will
be turned on and the scrubber and blower will be switched on without any human
intervention.
Once the system starts, it will create negative suction near the leakage hood and
pulls out entire leaked chlorine to the scrubber system. The scrubber will
neutralize the chlorine gas by caustic solution and will leave treated gas to
the atmosphere via blower and chimney.
The scrubber system consist of three section. 1 Spray section and 2 Packed bed
section. The inlet gas from the hood enters horizontally in spray section where
15 % caustic solution is sprayed with high pressure at cross current direction
to scrub the chlorine. This section handles extremely high concentration of
chlorine. After passing through the spray section, it enters into the packed bed
section, it acts as polishing section to increase scrubbing efficiency.
The entire chlorine gas is neutralized before releasing into the atmosphere. The
scrubber is capable of reducing the inlet chlorine gas concentration to less
than 5 ppm at the outlet. A pre-treatment stage (spray section) handles
extremely high concentrations while subsequent high-efficiency stages remove the
remainder of the toxic vapors. During catastrophic releases, the scrubber
achieves more than 99.999 % chlorine vapor removal efficiency.
Features
Factory-assembled for easy installation
Proven in independent testing under a catastrophic one-ton gas release
Skid-mounted
Compact, low profile enables indoor installations
FRP construction for strength and corrosion resistance
Integral secondary containment
Heat trace and insulation
Designed to contain and treat up to eight 150-lb chlorine cylinders
Minimum maintenance at remote, unmanned locations
Typical Scrubbing Products Liquid chemicals that have been used to scrub chlorine
include:
Sodium hydroxide
Potassium hydroxide
Sodium carbonate
Calcium hydroxide
Hydrogen peroxide
Sodium hydroxide solutions are the most commonly used for typical scrubbing
applications. However, the other chemicals listed above have been successfully used
in many applications where they may be readily available, less expensive or satisfy
the specific application.
Drizgas Tech is one of leading manufacturer of Emergency chlorine scrubber in India.
We provide highly efficient, top-quality scrubber system built around your precise
requirements. Contact us with your process information so we can begin discussing
the type of new equipment that best fits your situation.
Phone Number
+91 842 823 1593 | +91 995 287 7991
Email Address
sales@drizgas.com | info@drizgas.com
Office Address
No. 50, Villianur Main Road, Odiyampet, Puducherry - 605 110, INDIA