Method for desulphuration of the digestate and the biogas of a digester, and biogas production facility implementing said method

摘要

The invention relates to a method for desulphuration of the digestate and biogas in a digester (1) of urban and/or agricultural and/or industrial effluent, by biochemical and/or thermochemical processes, the digester consisting of an enclosure (2) which is closed at the top, in which anaerobic digestion of a mass of products to be treated making up the digestate (4) takes place, the digester comprising at least one loop (10) for external recirculation of the digestate; an oxidant is injected at least at one point (13, 14) of the loop (10), the injection conditions being as follows: the speed of circulation of the digestate in the loop (10) must be high enough to prevent the deposition of sulphur on the walls of the pipes; the contact time between the injected oxidant and the recirculated digestate recirculated from the injection point (13, 14) of the oxidant until the reinjection point (11b) of the digestate must be long enough for all the oxidant to be dissolved in the liquid phase of the digestate; the amount of oxygen in the oxidant injected into the recirculation loop must be low enough to avoid the presence of oxygen in the biogas, but high enough to eliminate the hydrogen sulphide from the biogas.

主权项

1. A method for desulfuration of a digestate and a biogas in a digester for urban and/or agricultural and/or industrial effluents, by wet and/or dry route, the digester comprising a chamber which is closed at the top and in which anaerobic digestion of a mass of products to be treated takes place, forming the digestate, with a gas space above the digestate, from which the biogas is withdrawn, the digester comprising at least one external digestate recirculation loop, wherein:
a digestate withdrawal point is situated in the lower part of the digester, and the digestate is reinjected at a point at a liquid level higher than the withdrawal point, at least one point of the digestate recirculation loop, a gaseous or liquid oxidant is injected, the injection conditions being as follows: a circulation rate of the digestate in the loop is sufficient to prevent the deposition of sulfur on the walls of the lines in the recirculation loop, a contact time between the injected oxidant and the recirculated digestate, from the point of injection of the oxidant to a point of reintroduction of the digestate in the chamber, is sufficient for all of the oxidant to be dissolved in a liquid phase of the digestate, the amount of oxygen in the oxidant injected into the digestate is low enough to prevent a presence of oxygen in the biogas but high enough to remove hydrogen sulfide from the biogas, a sulfur produced remaining in the form of particles which are dispersed in the digestate and being removed together with the digestate.