SAFETY IN THE PLANT
ne huge current trend throughout all industries emphasises ecology and waste utilisation. For this reason, waste gasifi cation technology along with the ability to process it into pellets, briquettes (and their subsequent usage) are two key areas being developed. Just like with any fuel, it’s crucial to understand the fi re and technical characteristics of these alternative fuels. Given that the combustion of solid alternative fuels is often conducted in existing technologies such as coal and wood chips, several essential parameters must be assessed and determined from a fi re and explosion perspective to ascertain whether the fuel can be used in the technology as is or requires modifi cations before it can be implemented. First and foremost, it’s necessary to
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possess fi re and technical characteristics of both existing and new fuels. Without this knowledge, clear conclusions cannot be drawn. T e following text outlines certain parameters that require focus and details how a parameter change infl uences practice. A signifi cant parameter is the lower
explosive limit (LEL). Based on this, spaces are classifi ed into zones – Zones 22, 21 and 20. If the new fuel has a considerably low lower explosive limit, space classifi cation might shift, e.g., from Zone 22 to Zone 21. T e ignition temperature of suspended/ deposited dust is crucial to assess whether hot surfaces that might occur in the technology could serve as an ignition source. If the new fuel signifi cantly lowers these temperatures, existing installed equipment might not comply, necessitating replacement with new equipment that aligns with those temperatures.
KST IS CRUCIAL
Another crucial parameter is the Kst constant and the associated explosivity
New fuels require new thinking when it comes to explosion protection
Ilona Šimoníková discusses alternative fuels and their utilisation regarding fi re and explosion protection
protection design, e.g., calculating areas for explosion venting devices. Individual protective elements are certifi ed for explosivity classes St1, St2, and St3. A system designed for St 2 cannot be used for a higher class like St3; however, it can be used for a lower class like St1. Maximum explosion pressure is another parameter used for vent area calculations, and knowing its value is essential. T e higher its value, the larger vent areas must be installed on the equipment. If the fi re and technical characteristics of
class St. T ese two parameters are closely linked. T e Kst
the new fuel exhibit more favourable values than the existing fuel, this new fuel can be safely used with existing technologies. However, introducing a new fuel raises several critical questions: Is there something that can be done
Vent area calculations are critical before installing new equipment
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to prevent zone tightening (installation of exhaust or increasing the performance
value is used for explosion
of the existing system)?; Are devices currently installed in the newly classifi ed zone appropriately designed, meeting the requirements for maximum surface temperature?; When reevaluating zones, what potential ignition sources may emerge, such as in assumed or exceptional malfunctions? T is leads to the related topic of whether ignition sources can be excluded or not, necessitating the installation of explosion protection.
All parameters of the new fuel, risk analysis and technical measures to ensure operational safety must be evaluated in the most important document addressing this issue: the Explosion Protection Document (EPD).
Ilona Šimoníková is Head of Risk Analysis department at VVUÚ.
www.vvuu.cz
FIRE PROTECTION FOR NEW FUELS
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