03-07-2012, 02:48 PM
HAZARDS IN CHLORINE MANUFACTURE AND STORAGE
HAZARDS IN CHLORINE MANUFACTURE & STORAGE.pptm (Size: 141.64 KB / Downloads: 103)
INTRODUCTION
Chorine is the by-product of Caustic-Chlorine Industry. It is generated by the electrolysis of brine in mercury, diaphragm or membrane cells. There are 500 Chloro-alkali plants in the world with a total annual capacity of over 50 million tons. DOW Chemicals is the largest producer of chlorine (6.0 Million Tons). In India hardly 2.5 Million tons chlorine is produced, 5 % of world production from 42 plants. GACL is meeting 16 % chlorine demand of India.
Today, chlorine occupies a pivotal role in chemical production. Thousands of industrial and consumer products are made using chlorine. It is called “GIFT” to mankind. But in spite of these benefits, chlorine has environmental and health risks which need to be managed responsibly. Human exposure to chlorine has resulted in large number of deaths and injury. Major accidents are due to lack of knowledge and over confidence. To prevent serious injuries and inherent hazards associated with chlorine, policies and procedures has to be established. This encourages communication, good house keeping, timely maintenance, educating the persons involved, monitoring, auditing, developing, adhering to standard operating practices.
CHLORINE - MANUFACTURING PROCESS
- Chlorine produced by the various processes especially by electrolysis is saturated with water vapor at high temperature and may also contain traces of chlorinated hydrocarbons and is normally at slightly above atmospheric pressure. Before the chlorine can be used, it is to be cooled, dried, purified, compressed and where necessary liquefied.
- Liquid chlorine is stored in tanks and filled in 900 kgs. tonners and 100 kgs. cylinders by dry air padding / liquid chlorine pumps and dispatched to various consumers.
- In developed countries liquid chorine is transported in tankers and railway containers of 55 MT / 90 MT capacity.
- This mode of transportation is yet to pick-up in India.
- During manufacturing operation different types of chlorine is being experienced:-
Fire and Explosion Hazards :
- Non combustible in air.
- Most combustible materials will burn in chlorine as they do
in oxygen.
- Flammable gases and vapors will form explosive mixture
with chlorine.
- Reacts explosively with acetylene, turpentine, ether, fuel
gas, hydrocarbons, hydrogen and finely divided metals.
- It reacts with ammonia, forming explosive nitrogen
trichloride.
- Dry chlorine reacts violently with titanium.
- Liquid chlorine + carbon di-sulphide explodes when added
in iron cylinder.
- Liquid chlorine passed through polypropylene with zinc
oxide reacts explosively.
- Tin with liquid chlorine at –34 Deg.C and aluminum powder
at –20 Deg.C leads to explosions.
- Rubber with liquid chlorine or dry gas leads to fire and
explosions.
- The vapor is heavier than air and shall travel along the
ground and persists at low level.
- It is difficult to disperse.
- At local heating of steel equipments and chlorine – iron fire
may develop at 251 Deg.C.
- If exposed to fire, cylinders may explode violently releasing
total contents. A full cylinder may burst at heating to 95
Deg.C.
- Chlorination reactions must be carefully regulated to prevent this
reaction from going out of control.
CELL HOUSE :
- Chlorine is generated in the electrolyser slightly above atmospheric
pressure. In the event of failure of down stream or any abnormality it is possible that full chlorine production rate can over pressurize the electrolyser / collection headers and large quantity of chlorine can enter the atmosphere. For this necessary control valves / safety valves are provided which are connected with the caustic scrubbing system.
- There is the possibility of hydrogen generation along with chlorine
in the electrolyser. It can form explosive mixture. Continuous analysis of chlorine / hydrogen is a must to avoid this hazard. In membrane cells hydrogen in chlorine has reduced considerably. But some explosions have taken place due to pin holes developed in membranes.
- All the products are at higher temperature 85 – 90 Deg.C in Cell
House and can cause chemical / thermal burns. Protective equipments such as goggles, hand gloves, boots and respiratory system must be used by the working personnel to avoid any hazard.
- In the Cell House even the minor variation in process parameter
leads to big hazard in the electrolyser / down stream. In order to avoid this production system it is to be controlled by procedures, instrumentation competent dedicated and experienced persons only.