This case study is an example of a series of Kamengo metering bin feeding construction and demolition debris and other wood waste into one of two power boilers. Each power boiler has six Kamengo metering bins.
This is an example of a storage bin designed specifically to handle difficult flowing biomass, including stringy woody biomass.
Standard storage bins used to handle biomass are typically negative taper, and use a live bottom reclaim system such as augers or a stoker.
In summary, live bottom negative taper bins struggle handling biomass because: 1) they allow the stored biomass to compact on itself and place a heavy load on the reclaim system, 2) promote material compaction by driving material against the bin front wall, and 3) withdraw material in a funnel flow discharge pattern, which induces rat-holing.
The solution to a reliable biomass storage bin starts with good bin design and moving away from the negative taper bin to a positive taper bin where the majority of the load in the bin is carried by the bin walls, and where the biomass will accelerate from the storage bin during discharge. However, for reliable discharge, the geometry of the positive taper storage bin must be correct. The most conservative bin shape for handling biomass is a plane flow hopper shape with a wide and long discharge opening. A plane flow hopper only converges in one plane at a time, and is vertical in the opposite plane. The plane flow hopper is the most conservative hopper shape. The purpose of using a conservative bin shape with a long and wide discharge outlet is to employ a geometry where if the Feeder were removed, the entire bin would self-empty with gravity in a mass flow or first-in, first-out discharge pattern.
The second half of the solution is to pair the plane flow hopper with a fully-effective feeder – that is a feeder that withdraws material evenly from its entire infeed opening. By definition, to achieve mass flow, where the stored material comes down as a single body, the feeder must withdraw material evenly from its entire opening. If the Feeder withdraws material selectively from the bin discharge outlet, sections of material in the bin will be stagnant and funnel flow will ensue.
A great example of a fully-effective feeder is the Kamengo Feeder. In addition to being fully-effective, the Feeder offers consistent metering, and can be made as wide as needed and as long as wanted. As a result, the Kamengo Feeder offers valuable advantages when designing for a difficult flowing fibrous material.
To learn more about the physics of storage bin and feeder design as well as the root causes of bin plugging, please download our white paper entitled: The Design of Reliable Storage Bins and Feeders for the Biomass Industry.
This is an example of a tall 30,000 cu-ft (825 cu-m) truck load out storage bin designed to handle construction and demolition wood waste and other difficult flowing fibrous materials.
Processed construction and demolition wood waste gains strength very quickly when it is subject to compaction, including compaction under its own weight in a storage bin. When processed C&D wood waste compacts it gains shear strength very quickly. Compact C&D wood waste enough and you will form bricks that have the strength of a cement block. It is this strength that enables the material to bridge over wide openings.
Processed construction and demolition wood waste is a relatively low-density material, and this means that the force supplied by gravity to keep the material moving is less relative to other bulk solids. With gravity being the primary force for emptying the storage bin, it is easy to design a storage and feed system where the strength that C&D wood waste gains under compaction exceeds what gravity can break. These storage bins suffer from erratic discharge and/or chronic plugging.
Processed construction and demolition wood waste is a highly variable material. It can be stringy and have long sticks. A conservative design includes using a wide and long bin opening, steep and lined bin sloping walls, and using a feeder that pulls evenly from the entire opening of the storage bin.
Standard truck load out bins use clam shell gates to control discharge. The problem is that when the clam shell is partially open, a funnel flow discharge pattern is induced, which introduces a high risk of bridging and rat-holing. Further, there is little control in how the truck is filled and the loads that are transferred to the truck.
The solution to a reliable C&D waste truck load out bin that provides a controlled discharge of material has two parts.
The first half of the solution is to use a plane flow hopper shape with a wide and long discharge opening. A plane flow hopper only converges in one plane at a time, and is vertical in the opposite plane. The plane flow hopper is the most conservative hopper shape. The purpose of using a conservative bin shape with a long and wide discharge outlet is to employ a geometry where if the Feeder were removed, the entire bin would self-empty with gravity in a mass flow or first-in, first-out discharge pattern.
The second half of the solution is to pair the plane flow hopper with a fully-effective feeder, which withdraws material evenly from its entire opening. A fully effective feeder is, by definition, necessary to actually achieve a mass flow discharge pattern in the hopper, which is necessary when handling a difficult flowing fibrous bulk solid.
Kamengo’s proposal is to use a plane flow shaped truck load-out storage bin with a vertical section and roof to provide up to 30,000 cu-ft (825 cu-m) of live storage. The storage bin has steep sloping walls, and each sloping wall is lined with a single seamless sheet of UHMW. The storage bin has a wide and long 6-foot by 24-foot opening, which is necessary to overcome the bridging dimension of C&D waste.
The storage bin is paired with a Kamengo Feeder. The Kamengo Feeder is capable of filling a range of truck beds. Of critical importance, the Kamengo Feeder withdraws material evenly across both its entire length and width. The result is that the stored material is withdrawn evenly from the full discharge outlet of the truck load out bin. An even withdrawal of material is absolutely required to achieve a first-in, first-out discharge. The Kamengo supplied PLC has a user interface where the truck driver selects their truck-type and is given instructions on starting the loading procedure. Based on the truck type, the Kamengo Feeder, which delivers a consistent, predictable volumetric discharge, will deliver the volume desired for the chosen trailer type.
To learn more about the physics of storage bin and feeder design as well as the root causes of bin plugging, please download our white paper entitled: The Design of Reliable Storage Bins and Feeders for the Biomass Industry.
