Aufbau und Inbetriebnahme eines Gaswäschers für Synthesegase aus Biomasse

Within the scope of this master thesis, a purification plant for syntheses gases from biomass is to be built and put into operation. The aim is to operate the plant within the framework of the European research project Phy2Climate in order to purify the synthesis gas from a pyrolysis based process from pollutant gases such as ammonia (NH3) and hydrogen sulfide (H2S). This enables a material use of the synthesis gas to produce liquid energy carriers via catalytic synthesis processes. In addition, a saving of fossil energy sources should be achieved. The main tasks for the commissioning of the plant were the mechanical and electrical construction as well as the automation of the plant. The modular plant consists of gas scrubbers for coarse cleaning, fixed bed reactors for fine cleaning, a cooling trap for water separation and final ammonia removal as well as a police filter, which can be used as required.
The real commissioning was preceded by a methodical commissioning, which included nitrogen and noxious gas tests with ammonia and hydrogen sulfide to measure the separation efficiency of the gas cleaning system, respectively of the respective system components. Tests on the coarse separation of NH3 and H2S using the gas scrubbers showed that the input concentrations of the gases could be significantly reduced using water as the scrubbing medium. For example, the concentration of ammonia was reduced from 7.33 % to 0.45 %. Fixed bed reactor tests for fine cleaning of H2S including loading and regeneration were also made, whereby the input hydrogen sulfide could be depleted from 2.5 % to below 200 ppm. Tests on the functionality of the cold traps showed that there were blocking problems after the first cold trap for water separation, due to excessive residual moisture and subsequent icing. To solve the problem, a drying tower filled with silica gel was connected between the first cold trap and the second cold trap. This reduced the relative gas humidity to below 0.28 %rH and prevented blocking. In the tests on the separation efficiency of the purification system using all purification components, a reduction of the inlet concentrations from 3.44 % NH3 to below 10 ppm and from 3.21 % H2S to below 10 ppm was observed. The subsequent test using syngas from sewage sludge from the TCR® laboratory plant showed that the purification plant maintained the performance of the previous commissioning tests even under real conditions and achieved a reduction of the pollutant gas concentration to < 5 ppm ammonia and < 1 ppm hydrogen sulfide. The results showed that with the help of the syngas scrubber presented here, the objectives of the Phy2Climate project, with respect to the pollutant gas concentrations in the low ppm range, could be successfully achieved and the pyrolysis gas could be almost completely purified from pollutant gases.
In the future, the stability of the purification performance will be proven by long-term tests and the connection of a synthesis gas compressor for the subsequent compression of the synthesis gas will be carried out.