Bio-methanation at the Agricultural College of Obernai

[Did67]

[This thread follows-and completes by illustrating it in a particular case-with another thread on methanation: https://www.econologie.com/forums/quelques-c ... 11627.html
]



Yesss!

Le Foll is due to inaugurate the Obernai Agricultural College station on April 18, which is now being "ramped up" (connection to the network on April 3).

In Alsace, 5 projects are in operation, being completed or under construction.

With production of 180 kW electrical, about 150 thermal kW sold to an agro-food factory that has a big need for hot water for cleaning every night (the rest used to heat the digester or keep it warm and most importantly, to pasteurize certain wastes - in particular leftovers / canteen waste).

The digestate will make it possible to eliminate all "chemical" fertilization on approximately 600 ha (networks of farmers).

We will try to promote the technique and to initiate future methanizers.

[chatelot16]

while one is in the description of this instalation, the tank is in what? concrete or steel?

and thermal insulation?

I imagine thermal insulation of the vertical wall, and bottom directly on the ground?

[Did67]

I'll have to put data, photos ....

Quickly:

- two tanks (digester and post-digestion / storage) in reinforced concrete, two-thirds buried, on a waterproof membrane (protection of the water table), insulated (expanded polyurethane polystyrene sheets), covered with wood ( larch)...

- I need to check in our archives to know if there is isolation down; I think so - but I will confirm.

- our "objective" was to reach the maximum bonus, therefore to "recover" the maximum heat and to "self-consume" as little as possible (since this no longer enters the calculation of the V !); there remains a doubt as to whether we will reach the max, because of the legal obligation to pasteurize some waste (canteen waste, ... students have the right to eat but must pasteurize before giving it to eat bacteria! ), which increases (a little) our self-consumption ...

The tank was filled last week: digestate from the Ribeauvillé station ("Agrivalor") + manure + slurry ... The "soup" is ready but still cold!

The unit was connected yesterday.

The Schnell group was started up immediately, and is running in "fuel mode": electricity injected into the network, heat is used to heat the tank (temperature rise programmed over 4 days). Perfectly stable, until then. And surprisingly silent: at 200 m, impossible, in the ambient noise, to know if it works or not! It is "monitored" remotely, via the Internet, from the factory headquarters in Bavaria.

After that, it should start to "boil"! As soon as the methane is rich enough, switch to "dual fuel" mode!

[Did67]

I confirm : insulation from below the tanks too.

[chatelot16]

thank you for the information ... the use of the insulating property of the ground is complicated, if in addition it requires an additional sealing for safety, I understand that we prefer to isolate directly under the tank

what is the volume of the tanks?

it seems that for the moment the heating of the tank uses heat at almost 100 ° C salable

there could be some of the heats fatal usable for heating the tank

I imagine that during the temperature rise of the tank, it uses water at high temperature, but once the correct temperature is established, the return of the heating water of the tank must be close to 40 ° C

[Did67]

For the volumes of the vats, I have to go back into the plans. Unfortunately I am very fragile side memory, I forget the speed where it comes in since my heart attack!

So currently:

- digester full of a mixture digestate / manure + slurry (essentially);

- progressive warming in progress, at the rate of 2 ° by 24 h, to start the mesophilic methanation process ...

- the dualfuel group Schnell runs at very partial power (65 electric kW at the moment), only on fuel (since not yet gas)

- electricity (about 40% yield) is sold

- the cooling heat is fully used to warm the tank ; it is not advisable to go faster, so we are bridling the engine accordingly; we went up to 75 kW elec before realizing that it was heating up too fast, so we went down to 60 kW elec.

Note that given the recovery of part of the TIPP and given the expected price for the electricity sold, also given the yield, the sale almost pays for the diesel and the heating of the tank is "free" in a way.

[this is one of the advantages of this dual-fired technology, compared to gas engines where the tank is fired with a boiler (in general)]

[Did67]

it seems that for the moment the heating of the tank uses heat at almost 100 ° C salable

Considering the speed imposed on the engine (it runs at around 30%), the "engine exchanger" outlet temperature is around 75 °.

The engine cooling circuit passes through an exchanger whose "output" feeds a manifold to which the tank "reheating" circuit are connected, with its own regulation, a "pasteurization" circuit and the "heat sales" circuit which leads in another exchanger placed with our neighbor / customer! There is a "waiting" circuit (my reflection around a storage in the ground) ...

There is of course an emergency radiator on the roof of the box, in case of absence of withdrawals by any of the "useful" circuits.

The heat would be salable, but our contract plans to charge our customer only 50% of the value that would cost the production of this heat from a chauidère gas (he must keep safe).

This clause is attractive financially speaking, for the client, to engage in the project, knowing that we also win on our side via the bonus (we hope to reach the V max!).

But currently, we have no interest in selling this heat to "buy" more expensive to heat the tank! (if we installed a gas or oil boiler). Hence the engine clamping to just the power necessary for heating as long as we are on fuel!

[Did67]

there could be some of the heats fatal usable for heating the tank

There remains about 6% of fatal heat: the muffler + the air flow (controlled) cooling the box (which drains the heat released by the engine, knowing that the "useful" parts - exhaust up to exchanger / cooler - are caulked).

The casing is ventilated - in a regulated way - so as to maintain 35 ° at this time.

In theory, the heat of the exhaust is recoverable by modifying the pot, by passing it through an exchanger. I suppose that if Schnell does not do it, it is that it is hardly profitable, considering the care brought also to the energetic questions!

[chatelot16]

in the case of an explosion-only engine, it should be given gasoline! ... but it's not a big problem: this tank heating without methane production should not happen often

I understand that you do not know by heart the volumes of the vats ... and I'm in no hurry, it's better to have an exact answer later than anything of memory!

[chatelot16]

the ventilation of the box at 35 ° c is not far from the 40 ° C of the tank

in order to be able to use this fatal heat to heat the tank, it would be necessary to allow to raise the temperature higher, with the risk of reducing the reliability of all the bazaar which is around the engine! we can understand that it does not happen

but what I wanted to say in my previous message is the water exchanger on the echapement: there is already an exchanger 100 ° to make salable hot water, there could be an exchanger more a 45 or 50 ° only able to heat the tank

same story for the intake air cooler

of course it's small wins ... on these 6% currently lost it will recover less than half ... 2% won?

on the exhaust, at the outlet of the already existing exchanger a water exchanger 50 ° C could be all plastic, to withstand well the condensation ... a large bundle of black polyethylene tube 16mm kind irrigation

this kind of plastic exchanger can also be used to heat greenhouses, I think with water has even lower temperature 20 ° C?

Is there a greenhouse close to the engine? it would be possible to directly send the ventilation air of the box! and even the exhaust gas from the engine