Hydrogen sulfide gas causes a wide range of health effects. Workers are primarily
exposed to hydrogen sulfide by breathing it. The effects depend on how much hydrogen
sulfide you breathe and for how long. Exposure to very high concentrations can
quickly lead to death.
Highlights
Caustic scrubbing is a technology has been used for the removal of H2S from
exhaust gases in different industries for many years.
Improvements in design and control strategies, favorable prices for caustic
compared with other non-regenerable H2S scavenging chemicals, and the potential
for sales value for the NaHS (sodium bisulfide) product have made caustic
scrubbing an economic and viable option for some refinery streams
The scrubbing of hydrogen sulfide (H2S) using sodium hydroxide (NaOH) solution is
established technology, and has been applied in a variety of industries.
The removal of small amounts of H2S from gas streams is typically referred to as
scavenging. Caustic is often classified as an H2S scavenger, and competes with
other scavengers such as solid reactive adsorbents.
Scavengers are most often used for the removal of H2S in amounts of roughly 0.1
ton per day, or less. However, the product of caustic scrubbing of hydrogen
sulfide at moderate pH - NaHS which is also referred to as NaSH - when produced
at high quality can often be sold, and depending on the value of the product
solution.
Worker Exposure Limits
NIOSH REL (10-min. ceiling): 10 ppm
OSHA PELs:
· General Industry Ceiling Limit: 20 ppm
· General Industry Peak Limit: 50 ppm (up to 10 minutes if no other
exposure during shift)
· Construction 8-hour Limit: 10 ppm
· Shipyard 8-hour limit: 10 ppm
NIOSH IDLH :100ppm
IDLH:immediately dangerous to life and health (level that interferes
with the ability to escape) (NIOSH)
In the scrubbing process, sodium hydroxide reacts with H2S dissolved in
aqueous solution to form sodium bisulfide (NaHS) and sodium sulfide (Na2S).
H2S + NaOH → NaHS + H2O (1)
NaHS + NaOH → Na2S + H2O (2)
The extent of reactions 1 and 2 are dependent upon the amount of NaOH that is
available relative to the amount of H2S that is scrubbed into the solution.
When greater amounts of NaOH are present relative to the sulfide that is
present, the solution pH is higher, and continuation from reaction 1 to reaction
2 is favored.
NaHS is a valuable product than Na2S; in order to maintain product quality, it
is required to control the pH of the spent caustic solution so that NaHS is the
predominant sulfide species.
Na2S uses twice the amount of caustic necessary for H2S removal and it has a
limited solubility in water as well.
Features
Can handle air flow rate from 100 to 30,000 CFM
Removal method is Absorption / Chemisorption
Material of Construction: PP, FRP, PP+FRP, MS+FRP, SS 304, SS 316
High efficiency Tellerette®Tower Packing removes soluble/reactive
gases, solid particulate and liquid droplets down to 7
microns
Lower shell serves as integral sump for recycle of liquid
Spray nozzles accessible from top of unit
Entrainment separators prevent liquid carryover
Special multi-bed packing designs accommodate different scrubbing
solutions for removal of multiple contaminants
Efficiency up to 99 %
Important Considerations for H2S Scrubber Design
There are many different possible designs for caustic scrubbers.
In selecting a configuration for a caustic scrubber for H2S removal, the
following are some of the factors that should be considered:
H2S Concentration in exhaust gas
H2S load (per day)
Other contaminant (eg. CO2)
By product formation
Frequency of scrubber operation
Cost of caustic
Additional accessories
Continuous pH monitoring system for scrubbing liquid
Dosing system for adjusting pH
PLC operated control panel
SCADA system
Applications
Exhaust gas scrubbing
Municipal odor control scrubbing
Biogas purification scrubberMunicipal odor control
scrubbing
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