Emergency stop of CHP plant

The incident occurred in a biogas-fed Solid Oxide Fuel Cell Stationary system, working in CHP mode.
A sudden stop of the biogas feeding line caused the safety shutdown of the plant (SOFC module).
The reason was ice formation inside the chiller (located after the biogas compressor) and inside the condensing discharge piping. This ice was creating a pressure drop across the compressor, which went into alarm mode.
By the following maintenance, more heating power has been installed on the pipelines and the ventilation speed was reduced during winter time.

The ROOT CAUSE could be identified in a shortcoming of the design of the chiller.

chiller, piping

The event was unplanned. No signals or problems related to the biogas line were detected in the previous days

No consequences to people. No consequences to environment (no fuel release). The only damage is to the fuel cell plant since emergency shutdown can damage the cells.

Zero maintenance costs, the compressor was under warranty period.
Time Lost (hours): 1 month (because of Christmas break between the failure and the maintenance

taken by the plant operator after the event:
(1) maintenance; installation of trace heating on all piping and inverter control on the ventilation blower.
(2) Monitoring of the container internal temperature during the next seasons and in particularly during the winter.
A risk assessment identified a major risk for the SOFC plant operation in the fact that there are no redundancies on the fuel feeding line.