Technical Innovations
Timberjack studying biomass for the masses
Forest biomass has been considered as a potential solution for future energy needs for some time, specifically for feeding power plants. It has a high-energy output and is a natural 100% renewable energy source that has a neutral CO2 balance. To enable the off-highway industry to take advantage of biomass, Timberjack Corp. has received funding from the European Union to research and develop new processes in forest biomass technology.
The challenge for the company is to develop a production system that logistically makes biomass harvesting a practical, efficient, and cost-effective process. Timberjack already actively participates in global attempts to increase the share of renewable fuels in energy production, having adapted several of its harvesting machines and methods to enhance biomass production, including Model 770/720 Energy Harvester.
Industry experts agree that the successful application of biomass as an energy source will ultimately hinge on its ability to be "packaged" for delivery. The product has to be bundled in a manageable form that's easily collected, transported, stored, and used. To achieve this, Timberjack has developed a bundling machine that can be easily adapted to standard Forwarders in their product line. This innovative bundling machine will produce "slash logs" that are more than 3 m (10 ft) long and around 1 m (3 ft) in diameter. These bundles are wrapped with string every 760 mm (30 in).
Currently, three test machines are in operation in Finland for the country's Pietarsaari Power Station, claimed to be the world's largest biomass power plant. The bundling system is producing an hourly average of 20-30 bundles at a mass that averages between 0.36 and 0.64 t (0.4 and 0.7 ton). According to Timberjack, each bundle contains about 1 MW of energy when combusted, which equals around 60 to 80 L (16 to 21 gal) of oil fuel.
The bundles can be stacked and stored indefinitely because the compacted bundles do not rot or compost as easily as loose slash piles. Bundles are transferred to energy plants on standard trucks. Crushing or chipping is done at the plant to transfer the bundles into the right size particles for combustion. To maximize fuel efficiency, these "green" chips are often mixed with other materials such as bark, sawdust, or peat.
- Jean L. Broge
Siemag hoists new technology
 Siemag originally focused on trucks with capacities up to 265 t (290 ton) for its TruckLift, but structures that carry even larger capacities are being considered. |
Known for its mineshaft hoists and associated equipment, Siemag-Nordberg has developed an alternative to haul trucks used in the transportation of uncrushed rock or overburden from deep-pit-mining operations. In the majority of truck and shovel applications, material is loaded at various bench levels onto haul trucks that then make the slow and often arduous ascent around the pit circumference or via designated haul roads, encountering inclines averaging 8-10% and covering long distances to the surface. Many trucks are often in simultaneous operation spread out along the route, depending on the overall length of the haul and size of the mine.
Trucks still provide a cost-effective solution, offering high flexibility compared to fixed or semi-fixed transportation systems like conveyers, but as mines get deeper and distances to the surface get longer, any alternative means to further improve productivity would be beneficial. While trucks have gotten larger, fleet numbers have gotten smaller, and despite the fact that speed-on-grade has increased incrementally over recent years with the inclusion of more efficient drive systems and greater engine power, it can still take considerable time for fully laden trucks to make the round trip.
Siemag's TruckLift slope hoisting system could best be described as a giant truck elevator, structured to follow the same inclination angle as the pit basin. Fully laden trucks can be directly transported from the floor to the surface where its material can be offloaded, then returned back down the slope to be reloaded. The system was designed primarily for two loading points, one at the surface and one on the pit floor, but it can include additional points if required. Both loading points have arresters that lock the transport platform securely into position when it arrives, overcoming any weight changes affected by the truck's movements and reducing dynamic loading on the hoist cables.
It is constructed of four rails secured into a concrete travel-path and supported at strategic points by steel cross-members; the structure then carries the main transport platform that supports the truck. The platform and a counterweight are attached to either end of six to eight steel cables, powered directly from the surface by means of an integrated multi-rope friction winder. Rope sheaves guide the cables as the truck ascends or descends. The operator stays in the vehicle at all times during the hoisting process; as one loaded vehicle moves off the ramp, another takes its place, enabling the ramp to run at maximum loaded efficiency.
The complete motor-drive assembly is designed for operation without the need for tail ropes as weight compensation, so there is no requirement for any additional equipment to be located at the bottom of the mine.
As a mine gets deeper, the bottom loading station has to be relocated. Once the new ramps and path are built at the selected location, all that is required is to move the loading station, arresters, and cables, a task that can be "completed in a few shifts," according to Siemag.
The lift is equipped with an energy-dissipating retardation system to protect personnel and equipment in case of over winding. The platform is decelerated and brought to a complete stop through the conversion of the motor drive into a generator, dissipating the resulting kinetic energy as heat in a controlled manner across forced-air-cooled resister elements. The conventional mechanical friction braking system need only be triggered in an emergency, something that would only occur if several independent safety features had previously failed.
One of the main advantages of this system lies in the reduced transport time. According to Siemag engineers, while on a slope of 10%, trucks move at less than 3 m/s (10 ft/s). The slope hoisting lift can overcome the mine's natural angle of over 50% and accelerate a truck at 8 m/s (26 ft/s), including the time taken to move the truck on and off the TruckLift platform. Also, claims Siemag, whereas one vehicle is on the slope with the TruckLift plant at one time, conventional haulage requires a large number of trucks—especially on the incline part of the haul—to achieve the same overall transport volume.
Overall, the concept is open to several opportunities for optimization, which becomes possible when adapting trucks to changing operating requirements. For example, if the trucks were to be used only to transport material using the lift system and therefore operating only on relatively level ground, a reduction in engine power and driveline capabilities could be specified. Additionally, rather than using a truck with a fixed body, material transportation could take the form of semi-trailers or bottom dumps with trucks acting as tractors, loading and unloading at each station.
- Dave Porter
