Use Case 3: Key Results

Key results from the implementation of RESTORE Use-Case 3, Ružomberok, Slovakia, are summarized and categorized as follows:

A case of application has been defined, where in the first approach the thermal power of the reactor was set to P_{R_th}=14.32 MW. This assumption was made to use all the steam, which can be generated, when the biomass boiler is under full load operation. In total, this assumption leads to a steam flow of 34.21 t/h, where 20 t/h are fed to the thermochemical reactor, whereas the rest (14.21 t/h) is spent to the steam turbine, producing an electric power of 1.4 MW. This case leads for charging to a very high mass flow of TCES, fed to the TCES-reactor (50,69 t/h), while 36.79 t/h are extracted. Both values are pure solid flows, not considering the oil, which is suspending the solid material.

In case of discharging at a thermal power of P_{R_th}=14.32 MW, the process was assumed to be operated without ORC-cycle. The reason for, is the relatively low condensation temperature of the ORC-process, which prevents from using the heat of condensation for heating up the return water of the district heating network. To operate the TCES-reactor at 14.32 MW causes high mass flows of solid matter to and from the reactor (feed: 313.4 t/h, extract; 431.7 t/h).

As an alternative and for comparison the discharging case, including ORC for electricity production, for a thermal power of the TCES-reactor of P_{R_th}=1 MW was analysed. Solids flow to the reactor is therefore reduced to 21.88 t/h; solids flow out to 30.15 t/h (due to the added water at hydration). At a heat input to the ORC-cycle of 646.5 kW an electric power of 46.07 kW is produced and a waste heat flow to the ambient of 521.1 kW occurs, which can’t be used in the current plant configuration.

Summarized, the findings presented in this report show:

that the TCES-system can be used for supporting the DH-network sufficiently, only if the system is used without the ORC-cycle at discharging. To overcome this problem the condensation pressure of the ORC should be enhanced (to allow higher temperatures for heat release) or the temperature of the DH-network changes, e. g. to allow for using a heat pump.
that the described case, using a TCES-reator with a thermal power of P_{R_th}=14.32 MW, (chosen to calculate the resulting operating parameters) leads to inappropriate high values concerning solid mass flows, reactor size and volume of storage vessels, especially for long term storage.
that, considering a realistic upscaled TCES-reactor with a thermal power of P_{R_th}=1-2 MW, could be a reliable possibility for the paper mill to supply for certain demand in future.

Overall, the findings presented in this report reinforce the suitability of the integration of the RESTORE proposed solution to paper mill plants, as virtually demonstrated in Use-Case III.