29Views & Citations
Nitrocellulose consists of two grades viz., Propellant grade containing more than 12.5 % nitrogen used for production of smokeless gun powders and Industrial grade containing less than 12.5% nitrogen and employed as a film-forming agent in solvent-based paints, protective coatings, fingernail polishes etc. Nitrocellulose (Figure 1) is a derivative of cellulose and is manufactured from purified cellulose either in the form of cotton linters or wood pulp. The manufacturing process involves nitration of purified cellulose with nitric acid and Sulphuric acid under controlled conditions followed by stabilization and washing.
The fire affected plant manufactures industrial grade nitrocellulose by removing water from wet nitrocellulose by centrifuging and adding a solvent such as isopropyl alcohol/butanol. Wet nitrocellulose with nitrogen content in the range of 10.7% to 12.2% is taken as raw material.
Pallets carrying these drums are transferred to the designated storage area. Tankers carrying solvents- isopropyl alcohol/butanol are unloaded in MS storage tanks. During centrifuging process, the industrial wet nitrocellulose is manually taken in open top HDPE drums and using SS bowls, the centrifuges are charged. The centrifuge machine is operated between 500-900rpm for the desired duration. After obtaining the desired moisture content of 2-3%, isopropyl alcohol/butanol is mixed vigorously by using wooden shovel manually. Once the industrial damped nitrocellulose becomes ready, it is packed into corrugated/MS drums. According to security guard, he closed and locked the plant at 10:00pm as usual after the night shift. In the early hours between 03:00 to 03:30 am on the fateful day, he heard some crackling noise and immediately got alerted and rushed to investigate when he noticed huge flames and smoke emanating from the manufacturing area of the plant. He informed the fire brigade which reached in the next 25 min and brought the flames under control by 9:00 am. There was no explosion and there were no casualties in the incident. The factory (with RCC roofing) consisted of two halls, one on the northeastern side (13mx16m) meant for raw material storage area and the adjacent hall (15mx22m) called manufacturing area where three centrifuges were arranged adjacent to the southeastern wall. Behind the manufacturing area of the RCC building and the southeastern compound wall, working shed (15.5mx4m), with GI sheets roofing was located and contained one air compressor unit, two oil units & electrical panel board. Dyke wall of height 0.60 m was present behind the southwestern area where four tanks (one for Butanol 20 KL, one for I.P.A. 20KL and two solvent storage tanks each of capacity 30KL) were located. On the southwestern side of the manufacturing area finished material storage area (22mx25m) with GI Sheeted roof was located as shown in Figure 2 below.
OBSERVATIONS & FINDINGS
In the raw material storage area, finished products (solvent nitrocellulose) in different sizes of drums were stored in addition to raw material (wet nitrocellulose). All the material stored in the storage area was found to be partially burnt (Figure 3).
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