The Son
Member
- Location
- Herefordshire
There is your problemTemp has dropped from 37 to 27
There is your problemTemp has dropped from 37 to 27
Gas mixing has worked well for us for 9 years, minimal maintenance and all outside the tank. Nothing could be much simpler, low power motors. Changed the vanes on one compressor, more as a precaution, after over 27,000 hours.
Yeh I suspected temp would be a main reason. Will get oil boiler hooked up
Out of interest how bad is it to put formalin in the slats which will eventually enter the digester? Im talking 40 litres/week into a slatted tank that’s got 150,000 gallon of slurry in roughly ?
Great to hear from someone with experience, some questions.:
1) Was gas mixing part of the original design?
2) Is it a landia system?
3) What are the annual maintenance costs?
4) What is the annual energy consumption?
When you say Gas mixing has worked well for us for 9 years what do you actually mean ?
We feed 30-50% slurry from cubicles bedded with straw, its generally chopped better than in the photo. The only time we had issues with a floating mat was at startup when the total solids level was too low. We started on dirty water with added slurry, but this did not work so had 15 tanker loads from the local Anglian Water AD Monsal stage,Great records.
I visited the Ludlow Plant in 2009, which was working well on food-waste (from Somerset I believe). My only real concern for this type of mixing is when slow digested material is added such as grass and chopped straw and the risks of a floating layer.
What are your views.
We feed 30-50% slurry from cubicles bedded with straw, its generally chopped better than in the photo. The only time we had issues with a floating mat was at startup when the total solids level was too low. We started on dirty water with added slurry, but this did not work so had 15 tanker loads from the local Anglian Water AD Monsal stage,View attachment 660508
Normally 39-41°C, although when the pipes froze up recently we dropped to 33. It did not appear to hit gas production as much as I had feared, down about 1/3 but hard to estimate as we stopped feeding slurry when it was frozen.What temp do you operate at ?
I hope that this is nothing more than teething problems! I think we as farmers can be a little gun-ho with things!! I think in my lack of experience we added maize silage strippings which could have given it belly ache! Got to learn to keep things simple, As it is designed to be! I think that the concept is brilliant as we are producing green energy from waste, reducing slurry smells,gases, improving nutrient availability and able to use a lot of the heat in dairy boilers! However as in all new ventures, there will be lessons to be learnt!! OMNI are replacing our tank with a concrete tank, which should be a better job! As to downtime! I am generally over cautious with sales men’s figures and built in plenty of contingency! Glad to say that it looks as though it will exceed even the salesmen’s figures!!It's a good job we are not reliant on these systems for base-load
It is very interesting that each seem to be having so many problems, and no real reasons for the cause, other than Chippy indicating the stirrer is not up to the job.
There really could not be anything simpler than these small scale plants, operating may be the key issue here. If you were to calculate the lost kwhr's, you may soon find economy (capital cost) may have been a bit of a red-herring.
Criticism hurts, and it is not my intention to offend anyone, but if any of the lenders to agriculture get wind of all the issues for small scale Biogas, it may die before it really takes off.
I have wondered whether such an idea of a pre heat tank was a good idea! However we are working with a low cost digester as we are feeding it with only cow slurry, so have to watch costs! We have noticed that it likes the same amount of slurry every day! When we are spreading digestate and use the reception pit, it seems to have a knock on effect on the output! As for the tank, ours is 1000m3 and we were adding 35m3 per day without any problems as long as it was consistent!It doesn't seem to be unexpected that these plants are struggling.
I am not sure what temp slurry is, but the amounts that have to be added each day, to not a very large tank, especially in the winter, will inevitably decrease the temp, and it becomes a vicious circle, as engine outputs fall, so does heat output.
Would it be more effecient to heat the slurry to 25 degrees before it enters the tank so its not a such a shock?