04-07-2012, 12:54 PM
RISKS AND CONTROLS OF NITROGEN TRI-CHLORIDE
[attachment=26650]
OCCURRENCE & FORMATION OF NCl3
Nitrogen Tri-Chloride was first observed in 1811 from the action of Chlorine on the solution of Ammonium Chloride.
This compound is a yellow oil with a pungent Chlorine like Odour.
It is insoluble in water and soluble in most organic solvents.
A drop of oil explodes violently when touched with a feather dipped in turpentine.
Nitrogen Tri-Chloride is formed during the production of Chlorine when Ammonical Nitrogen is present in the brine fed to the electrolytic cells.
Any ammonical compound in the brine or water will be converted to NCl3 in short time. 30 ppm of ammonia in water is converted to NCl3 in 20 seconds.
NCl3 is soluble to the extent of 7.3 mg/l in liquid Chlorine.
ASSOCIATED HAZARDS
Increasing the number to 1.5 gm/cm2 results in fracture.
The hazard is less when Chlorine contaminated with NCl3 is spread in a wide pool than it collects in a nozzle or section of piping.
NCl3 is much less volatile (Boiling point:710C) than Liquid Chlorine (Boiling point:-340C). It tends to accumulate at different points in the process. Any NCl3 present in the gas shall concentrate in liquid chlorine. Vapor pressure of NCl3 is 0.11 atm and for chlorine is 3.68 atm at 0 0C which shows NCl3 will remain on evaporation of liquid chlorine.
Yellow oil of NCl3 explodes violently :
When heated in greater than 93 0C
Exposed to light
Brought in contact with Ozone, Phosphorous, Arsenic, Alkali and organic matter.
Spill of NCl3 is a hazardous residue. Spilled NCl3 can detonate on simple walking through it.
SOURCES OF NITROGENOUS IMPURITY
Nitrogen compounds may be present in salt and other chemicals added during processing.
Nitrogenous explosives used to break the beds in the mines.
Anti-caking agent present in ppm concentration.
Salt delivery vehicle is a potential source of contamination.
Dissolving water is the source of nitrogenous matter in solution mining.
Calcium Chloride used in some brine systems – a by-product of Solvay Process of Soda Ash is a source of Ammonical impurity.
DETECTION
To Control the formation of NCl3 in liquid chlorine, it is essential to limit the entry of Nitrogen compound in Salt and Brine solution in process continuously.
Analysis on line :-
An on line analysis has been developed by a French organization website :- www.seres-france.com. It works in on principle of sequential analysis
It can measure Ammoniac salt(NH4) Concentration in Brine & Ncl3 Concentration in Cl2 gas at the exit of Cl2 Compressor.
Magnetic fields & photo sensibility of Ncl3 influence the analyzer. Therefore the analyzer must be installed:-
At a sufficient distance from the Cells House.
In a close Cabinet with air conditioning & with no external light.
All Transparent piping (Teflon etc) has to be covered.
[attachment=26650]
OCCURRENCE & FORMATION OF NCl3
Nitrogen Tri-Chloride was first observed in 1811 from the action of Chlorine on the solution of Ammonium Chloride.
This compound is a yellow oil with a pungent Chlorine like Odour.
It is insoluble in water and soluble in most organic solvents.
A drop of oil explodes violently when touched with a feather dipped in turpentine.
Nitrogen Tri-Chloride is formed during the production of Chlorine when Ammonical Nitrogen is present in the brine fed to the electrolytic cells.
Any ammonical compound in the brine or water will be converted to NCl3 in short time. 30 ppm of ammonia in water is converted to NCl3 in 20 seconds.
NCl3 is soluble to the extent of 7.3 mg/l in liquid Chlorine.
ASSOCIATED HAZARDS
Increasing the number to 1.5 gm/cm2 results in fracture.
The hazard is less when Chlorine contaminated with NCl3 is spread in a wide pool than it collects in a nozzle or section of piping.
NCl3 is much less volatile (Boiling point:710C) than Liquid Chlorine (Boiling point:-340C). It tends to accumulate at different points in the process. Any NCl3 present in the gas shall concentrate in liquid chlorine. Vapor pressure of NCl3 is 0.11 atm and for chlorine is 3.68 atm at 0 0C which shows NCl3 will remain on evaporation of liquid chlorine.
Yellow oil of NCl3 explodes violently :
When heated in greater than 93 0C
Exposed to light
Brought in contact with Ozone, Phosphorous, Arsenic, Alkali and organic matter.
Spill of NCl3 is a hazardous residue. Spilled NCl3 can detonate on simple walking through it.
SOURCES OF NITROGENOUS IMPURITY
Nitrogen compounds may be present in salt and other chemicals added during processing.
Nitrogenous explosives used to break the beds in the mines.
Anti-caking agent present in ppm concentration.
Salt delivery vehicle is a potential source of contamination.
Dissolving water is the source of nitrogenous matter in solution mining.
Calcium Chloride used in some brine systems – a by-product of Solvay Process of Soda Ash is a source of Ammonical impurity.
DETECTION
To Control the formation of NCl3 in liquid chlorine, it is essential to limit the entry of Nitrogen compound in Salt and Brine solution in process continuously.
Analysis on line :-
An on line analysis has been developed by a French organization website :- www.seres-france.com. It works in on principle of sequential analysis
It can measure Ammoniac salt(NH4) Concentration in Brine & Ncl3 Concentration in Cl2 gas at the exit of Cl2 Compressor.
Magnetic fields & photo sensibility of Ncl3 influence the analyzer. Therefore the analyzer must be installed:-
At a sufficient distance from the Cells House.
In a close Cabinet with air conditioning & with no external light.
All Transparent piping (Teflon etc) has to be covered.