Fuel Prep Technology: Speed vs Throughput Debate

When procuring recycling and biomass fuel preparation technology for the future, should operators prioritize speed, or throughput?
By Peter Streinik | August 30, 2017

It would be naïve to suggest that biomass fuel preparation facilities exist purely for environmental gain. Of course, their creation of a renewable energy source is strengthening our nations’ commitment to greater resource security. But unless the schemes are community-backed, operators will naturally seek to make a profit from their sites.

In the face of often-fluctuating market opportunities and revenue potential, one way to safeguard these profit levels is by trying to minimize the biomass production cost per ton. But how can the possible margin of the plant’s machinery be boosted?

For some operators, this performance-driven mindset homes in on speed. After all, it is logical that the more wood a shredder can handle, the greater the volume of biomass feedstock that can be produced. And, typically, volume output means increased revenue generation.

But however simple the concept in essence, wood shredding is actually a far more complex process. Concentrating too much on speed and the inherent risks of the facility could rise as a consequence.
The target speed for a wood shredder should be no higher than 60 rpm. Above this, the machine will generate a significant level of dust, which not only makes for a dirty process, it also poses a significant fire hazard. If a slower rotor speed is balanced with a high torque, the technology can maintain target throughputs of up to 40 metric tons per hour, whilst generating less dust and thus reducing the risk of a spark.

In tackling this speed criteria, operators are often—albeit subconsciously—considering their throughput strategies at the same time. Capacity is not just governed by how many tons a shredder can process in a shift, for example. If the true capacity of a plant is measured in terms of output, there are other important factors at play such as particle homogeneity.

The biomass market demands a fuel manufactured to a defined specification, for utmost energy value. Operators should strive to maximize the proportion of on-specification feedstock that they can manufacture, if they are to optimize their revenues. Dust-like, nonspecification material (fines) represents nothing but a cost.

Studies have shown that high-speed wood shredders can produce up to 25 percent of fines, whereas with slower speed equivalents this figure will drop to as little as 5 percent. As a result, choosing the right machine can yield up to 20 percent more material per ton, reduce the disposal costs associated with nonbiomass specification outputs and protect the fire safety of the plant.

Other fire safety mechanisms can uphold throughput levels too—not to mention the long-term integrity of the facility. If the shredder is manufactured with an in-built fire suppression system, with extinguishing nozzles and heat sensors located throughout the machine’s hopper, cutting chamber and discharge conveyor, for example, this will prevent hot, glowing or lit material from exiting the machine. Not only does this containment method significantly reduce the risk of fire, it also maintains the likelihood of a continuous shredding operation. Even a simple, daily plant cleansing regime can help in this respect.

Of course, other seemingly simple modifications to a plant’s design can enhance its commercial viability. If the shredder has integrated foreign object protection, for example, the machine will automatically stop so that the problematic material can be extracted with ease, for minimal downtime. Additionally, if the wood can be shredded without the need for post treatment, such as a screen, this further streamlines the process and negates the need for additional capital expenditure.

Furthermore, if the shredder is flexible and able to handle different input materials, to satisfy varied end-product requirements, the plant has a greater degree of operational versatility. This may provide much-needed commercial protection during periods of market volatility. Few organizations stand still now in terms of the wastes they produce, which means recyclers and alternative fuel producers need to adapt.

These speed vs. throughput considerations aside, what must categorically be prioritized above all else, is safety—no machinery should ever jeopardize the wellbeing of operatives and wider stakeholders. However, as is hopefully becoming apparent, in opting for safe processing equipment, biomass fuel producers do not have to sacrifice the performance criteria already outlined. On the contrary, thanks to technological innovation it is possible to improve safety, by design, without compromising a plant’s bottom line. 

Continued research, development and engineering is enabling biomass fuel preparation technologists and their customers to tread new boundaries when it comes to machinery performance. So, why not strive for optimum capacity and greater process security, too?

Author: Peter Streinik
Head of Business Unit Waste, UNTHA
+43 6244 7016 65