CO Fire & Explosion

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Dear All,

In our plant we are installed a pre-heating system for pre-heating of coke. We have three coke bunkers. We have taken a tapping from the exhaust flue gas line going to the stack, and added a booster fan and taken the line to the bunkers for pre-heating.

The flue gas contains carbon monoxide at high percentages by volume. (Approx.1000 PPM and fluctuates depending upon the furnace process). The bunkers are open to the atmosphere at the top end. The LEL and UEL for CO are 12.5% and 74% respectively.

The booster fan specifications are as follows:

Capacity: 48000 k cubic meter

differential pressure: 70 m bar

speed: 1475 rpm

b h p: 174

design temp.: 300 degree C

This system was started 2 years back and was stopped due to an explosion at the bunker. Now it is planned to restart the same after doing a through risk analysis.

1. Kindly let me know, what can be done to negate the effects of CO with respect to fire and explosion at the bunker.

2. How can systems be put in place, so that in case of any leak of flue gas containing large quantities of CO, the system can trip. (there are 3 nos. of manually operated dilution dampers in the over all line)?

3. Will ingress of external air containing oxygen for controlling temp. sent through the dilution dampers aid fire and explosion / burning of CO at the above mentioned concentrations?

4. Also please explain me about the possibilities of dust explosion at the bunkers filled with coke fines and for negating the same what can be done?

With regards,

K. Haricharan,

Safety Engineer,

Safety Department,

Chanderiya Lead Zinc Smelter

Hindustan Zinc Limited

P.O Putholi, Dist. Chittorgarh - 321 012

Rajasthan

Ph: 4871

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