When a new Lithium mine located in South America purchased a metering bin to feed lithium carbonate precipitate from its centrifuge discharge to deliver an even feed to its dryer, the mine chose Kamengo to design and deliver both the storage bin and Kamengo Feeder.
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.
Retrofit of four live bottom metering bins that were suffering from chronic plugging at a pulp mill in Washington State. Kamengo replaced each metering bin with a new bin, Kamengo Feeder, chute and expansion joint.
Retrofit of eight small screw feeders experiencing chronic plugging. The screw feeders where replaced by four surge bins and feeders. Each Kamengo Feeder feeds a split chute, which in-turn directs the hog fuel into two boiler spouts.
Retrofit of a live-bottom metering bin handling wood waste that was suffering from chronic plugging. The metering bin was replaced with five individual Kamengo Feeders and bins.
Front-loaded metering bin, operating outside in an artic environment, delivering an even, metered discharge of wet FGD gypsum into a continuous process.
Two Kamengo metering bins receiving cobalt hydroxide filter cake from a filter press and metering the wet cake to a dryer.
Boiler feed metering bins that are metering poultry litter into a power boiler. This fuel is not only fibrous and compactible, but also sticky and corrosive.
This case study is an example of a retrofit of a 37-foot tall, 6,000 cu-ft silo used to store and feed hog fuel (wood waste) into a power boiler. The hog fuel at the mill is particularly challenging because it contains hickory bark and can be very stringy.
When Kamengo first met the mill, the plant engineers were exploring options to replace the entire hog fuel feeding system. However, upon learning of a retrofit to a similar size tall bin that Kamengo had completed for a pulp mill in Washington State, USA, the mill found that it could solve its feed issues by retrofitting its existing bin
Kamengo replaced the lower half of the bin with a rectangular plane-flow mass flow hopper and Kamengo Feeder. The Kamengo Feeder is ahead of a live bottom bin with screw feeders feeding biomass fuel into the boiler. Since the screw feeders cannot maintain a significant head of material above them, the Kamengo Feeder is used to reliably meter just enough material that the screw feeders can handle to ensure good, steady material discharge into the boiler.
This retrofit was completed in 2004.
Prior to the retrofit, the storage silo converged with a 60-deg cone down to a vibrating hat. The mill could not put more than 6-feet of material in the storage bin before it would plug. This was problematic, because this storage silo was providing critical storage between the hog fuel pile and the power boiler’s metering bins.
The existing silo was suffering from chronic plugging for three reasons:
The solution to fixing the silo had two parts:
The first half of the solution is to modify the bin geometry of the silo such that it will promote a first-in, first-out discharge pattern. In this case, Kamengo cut off the bottom portion of the silo, including the cone and replaced it with a plane flow, mass flow hopper and Kamengo Feeder. A plane flow hopper is the most conservative hopper shape.
The new hopper converged to wide and long 6-foot wide by 18-foot long discharge opening. This wide and long opening is required to ensure gravity will always be sufficient to break the strength of the arch that hog fuel would create above the Feeder. In summary, by replacing the cone with the new plane flow hopper, Kamengo fixed the geometry of the silo such that if the Feeder were removed, the silo would self-empty with only the aid of gravity. The minimum geometry required for gravity discharge, including minimum slope angle of the plane flow hopper and minimum discharge opening were all selected based on the flow properties of hog fuel.
The second half of the solution was to pair the plane flow hopper with a fully-effective Feeder – in this case a Kamengo Feeder. A fully-effective feeder is one that withdraws material evenly from its entire opening, which by definition is necessary to actually achieve a mass flow discharge pattern in the hopper. By definition, to achieve mass flow, the bulk solid must descend the storage bin as a single body with all the stored material in motion, and the only way to achieve this is for the feeder to 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.
Again, discharging in mass flow is often necessary when handling a difficult flowing bulk solid. What makes the Kamengo Feeder unique is that it can be made as wide as needed and as long as desired. This feature is particularly valuable given that the chosen minimum discharge opening of the silo is 6-foot by 18-foot. To achieve mass flow, the Feeder inlet must match this outlet. This is very difficult to do with conventional technologies, but very easy to achieve with a Kamengo Feeder.
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.
