A carbon dioxide-neutral biodigester plant, comprising:
- a) a biodigester for carbon dioxide-neutral, single-stage or multi-stage production of biogas by fermentation of biomass in a fermentation liquid agitated in presence of
- i) elemental hydrogen,
- ii) hydrogenotrophic and methanogenic archaea, and
- iii) activated carbon masses,
- b) a source of ammonia connected to a first ammonia line,
- c) an ammonia cracker to produce hydrogen or a hydrogen-nitrogen mixture by catalytic cracking of ammonia,
- d) a first hydrogen line for feeding the produced hydrogen or the hydrogen-nitrogen mixture directly into the biodigester, and
- e) a treating device for treating activated coal masses with hydrogen at higher pressure comprising:
- e1) a pressure line and
- e2) a treating spray lance
- wherein hydrogen-containing activated coal masses configured as spray cones are injected into the fermentation liquid of the biodigester,
- wherein ammonia from the source of ammonia is produced with power at least in part by renewable energies and the ammonia cracker is powered at least in part by renewable energies,
- wherein the ammonia cracker is configured as a double-tube reactor, the ammonia cracker comprising:
- c1) a central tube with a heat source arranged in the central tube, the heat source comprising a heating chamber with a metallic packed bed, a burner, and a flame,
- c2) a cracking tube with a cracking catalyst contained in the cracking tube,
- c3) a pressure reducer with an electronically controlled actuator,
- c4) a second ammonia line to a first recuperator for heating ammonia with hot exhaust gas supplied from the central tube via an exhaust gas line,
- c5) a third ammonia line for supplying the heated ammonia from the first recuperator to the cracking tube containing the cracking catalyst
- c6) a second hydrogen line for discharging the produced hydrogen or the hydrogen-nitrogen mixture from the cracking tube to a second recuperator for heating air fed to the burner and for cooling the produced hydrogen or the hydrogen-nitrogen mixture,
- c7) a cooling device for further cooling the hydrogen-nitrogen mixture or the hydrogen separated with the aid of a hydrogen-selective membrane to below 70° C., and
- c8) a separating device for separating ammonia from the produced hydrogen or hydrogen-nitrogen mixture before its introduction into a hydrogen-nitrogen distributor of the biodigester and before its introduction into the treating device for treating activated coal masses with hydrogen at a higher pressure.