Shouldn't you be asking the manufacturer / supplier /installer?

Hacon, why waste your time.... follow Clairel's suggestion I say!

Hi Hacon

In order to provide a better focussed response, could you provide a little more detail on the shape & dimensions of your feed hopper.

Frank Hallett

Hi

I have limited experience with biomass boilers, however I have in the past been involved in the safety issues associated with the management of coal bunkers/boilers. In cold conditions the moisture content present within the bunker resulted in the freezing together of the coal and "bridging" occurred as the auger took away the loose coal below and left a cave like gap around it. I imagine this is similar to the situation you are finding with the wood pellets,

It was this mechanism that had unfortunately led to the death of an individual who had walked over the coal not realising the bridge was there, he fell through into the gap and surrounding coal fell in on top of him causing asphyxiation. As a result of this a range of "trimming tools" were introduced across the organisation to permit coal to be moved towards the auger without the need to enter the bunker.

This incident did occur in the late 80's (possibly 1990) but hopefully the solutions generated then may be of use to you now and help prevent further injury/loss.

Hi Hacon - No experience of these units but did have a client who tried to make such pellets. He's now tried x3 different pellet/log-producing machines, of which the pellet one was first and the most problematic. I suspect Frank's nearest the reason - there's no real standard for pellets and you may get different ones with different "stickiness" depending on how it was made and from what, and its age.

My client was making these from minced scrap softwood (mainly pallets). I guess it depends what wood actually goes in. He gave up because the manufacturing costs outweighed the value of the product. Energy costs were large - these things shoot out of the press red hot and can wear out steel components in the press very quickly! You effectively liquefy the wood under pressure at temperatures >300C. The 3rd attempt produces economically viable low density chipwood logs reliably.

My research also revealed that pellets can and have combusted spontaneously - I guess due to the friction as the compressed wood tries to expand if damp - and there have been several asphyxiation deaths in ships holds because they also release CO to form a toxic atmosphere again suggesting spontaneous decomposition....

Sorry I can't be more help but I hope this is food for thought.

Dave Daniel

Although not directly related to your stated problem Hacon; I agree with the additional comments re volatility and also reduction of O2 in the immediate ambient atmosphere - you're quite right to treat the hoppers as a confined space for both reasons.


As with any bulk-stored, granular or free-flowing cellulose-based material, Pellets have a propensity to commence an exo-thermic reaction in bulk storage [unlikely in the feed-hopper though] that is very dependant on the condition on delivery, amount of humidity in the bulk storage vessel, actual storage mode, and especially related to bulk and duration without agitating - DSEAR applies to this aspect.

Hope that does it

Frank Hallett

Seeing the word 'auger' above prompts me to mention as a general aside that augers with their helical screw configuration are inherently dangerous items of machinery. I've investigated two auger accidents which resulted in foot amputations (one in a road gritting lorry hopper, the other at an ice-making plant at a fishing port) and knew of others investigated by colleagues. Thus, strict precautions are needed to prevent anyone having access to augers which are rotating (or could rotate intermittently and unexpectedly) under power.

Though I'm not acquainted with biomass pellet hoppers I guess that they do not incorporate mesh guards/grids over the augers because such features would hinder the downward movement of pellets and increase the tendency for bridging to occur. Therefore, locking-off of the power supply to a pellet auger is almost certainly as essential as measures against asphyxiation before anyone enters such a hopper.

Also, with ever-increasing rises in the price of gas and other conventional fuels, it's likely that more companies and organisations will consider and choose to have biomass heating systems installed in their buildings.

Hello dear sirs!
I'm sorry if it's a wrong thread or a wrong forum, but it seems like some people on this forum use biomass boilers.
I represent Russian company and we would like to get to know more UK market of wood pellets.
It will take just 5 minutes, but will mean a lot to us and understand UK market.

The link is here (it is totally save and confidental, using google sheets):
http://goo.gl/forms/XZsTtkt65D

We appreciate your help!

This is a 2.5 yr-old thread! I wonder what the deleted message contributed to the debate :)

If anyone's reading this with the same query, we installed a walking floor in our main fuel store.