Preventing Explosions in Co-firing Power Plants

A new safety approach for protecting coal/wood grinding plants against the ravages of a combustible dust explosion has been developed by REMBE using passive venting devices.

Through the combination of standard explosion panels and flameless venting, protection can be guaranteed as depicted in Figure 1 below. The system can be broken down in more detail based on each component:

Figure 1: Explosion Safety in a Biomass Power Plant with venting panels and REMBE Q-Rohr flameless venting.

Pulverizer Protection
A mixture of coal and wood is pulverized in roller mills which are usually located inside buildings. This location can create headaches when trying to properly protect these mills. Conventional venting concepts are based on free and open venting devices, such as explosion vent panels. This forces operators, architects, and engineers to consider spacing, location, and sufficient ducting to vent to the outside.           

With the advent of the flameless venting technology by REMBE®, indoor venting is available to solve this headache. The flameless vents can be installed on the air inlet to the mill and on the product discharge section of the mill. This explosion venting technology eliminates the need to create changes such as moving mills closer to exterior walls and breaking through those walls (pic.1).

Pic 1: REMBE Inc. Flameless vents protecting mills

Additionally, because flameless venting devices can be mounted inside the building, the venting occurs at the commencement of the explosion. The quenching of the flames occurs in close proximity to the starting point of the explosion. Thus, an explosion is instantly vented and will be less severe in comparison to conventional venting. 

Baghouse Protection and Isolation
The pulverized mixture then travels downstream towards a baghouse, generally located outdoors. To protect the baghouse and isolate the inlet ductwork from a combustible dust explosion, standards panels such as the REMBE ODV and EDP can be utilized. An example of this can be seen in Figure 1 above.  These panels are completely leak tight and suitable in any vacuum conditions. The exact quantity of vent panels will depend on the characteristics of the filter and inlet. 

Every vent panel can also be equipped with a burst signaling device. This type of device can be kept intrinsically safe and will be actuated when a panel opens. The signal can then be used to shut down the connecting processes and issue an alarm throughout the facility.

Silo Protection 
Finally, the last piece in this specific system is storage for the mixture. A silo is generally used outdoors and can also be protected by standard vent panels. In this case, there is little to no vacuum pressure in a silo so a REMBE EGV can properly protect this enclosure. This type of protection can be seen below in Picture 2.

Pic.2: REMBE EGV explosion venting panels on a storage silo in a Biomass Power Plant.

Additional Protection
It’s important to note that isolation protection is also required to stop the propagation of any combustible dust explosion. This can be accomplished through numerous passive approaches as detailed in NFPA. Such options as NFPA compliant rotary airlocks and/or conveyors can be useful isolation devices.

Additionally, if the filter and silo happen to be located indoors then they can also be protected by REMBE flameless venting devices. These passive devices are simple, passive approaches to properly protect a combustible dust explosion. In most cases, downtime can be minimized simply by replacing the vent panel, inspecting and cleaning the venting device, and ensuring the process is safe for start-up. After this, the flameless vent can be ready to protect again!

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