SEPPIL / CCCP (NO2.4)

Purpose and brief technical description, including figures as appropriate

SEPPIL / CCCP is a lab-pilot experimental facility suitable for CO₂ separation and purification of gas mixtures originating from pre-combustion applications such as hydrogen production, oxy-fuel processes, and pre-separated flue gases from post-combustion applications in industry and power generation.

The main purpose of the rig is to demonstrate the capture efficiency (CO₂ capture ratio and compositions of the gaseous and liquid separation products) from the various types of relevant gas mixtures that can be achieved by cooling and condensation. Another purpose is to test liquefaction of CO₂ at relevant temperatures and pressures.

Both purposes have been demonstrated in operational modes (finite separator retention time) and in a scale sufficiently large for industrial interest in four different projects so far. The throughput capacity is approximately 340 Sm³/h, which gives a maximum CO₂ throughput rate in the rough interval 5–15 ton per day, depending on the gas composition and suction pressure in consideration.

CO₂-rich liquid can be separated from CO₂-depleted gas in two separator tanks in series. The bulk separation takes place at high pressure in the first of the two vessels. At the inlet of the second vessel the liquid is throttled to lower pressure, which increases the purity of the liquid CO₂.

The test rig is instrumented to monitor the operation of heat exchangers, separators, compressors and other auxiliary systems:

• 25–30 temperature sensors (excluding compressor instrumentation);
• 6 pressure transmitters (excluding compressor instrumentation);
• 2 level meters for separation tanks;
• 4 mass flow meters;
• 5 extraction points for composition measurement by gas chromatography.

Maximum operation pressure is 120 bar on the high-pressure side. The minimum pressure depends on the freeze-out conditions and can be e.g. 6 bar(a).

An auxiliary refrigeration cycle with CO₂ as refrigerant is included in the RI. This unit has an evaporator temperature of around -50 °C. The capacity of the refrigeration unit is approximately 7.5 kW.

The facility has been upgraded to monitor liquid CO₂ storage. In one of the separation vessels, pure or impure liquid CO₂ can be stored over time and the storage process can be monitored:

• 10 temperature sensors are vertically distributed along the tank so that the temperature stratification can be monitored
• Liquid level meter
• Pressure sensor
• GC to monitor the development of chemical compositions in the liquid and gaseous phases

David Berstad (SINTEF ER): Behind the scenes of the ECCSEL Cold CO2 Capture Pilot Rig (CCCP / SEPPIL)

General: Located in the thermal laboratories of NTNU with its available infrastructures and services. 

Special: See brief instrumentation description above. Available gases: CO2, nitrogen, hydrogen, CO, methane

The RI is the first of its kind with the given process design.

The RI fits very well with the national R&D priorities on CCS. Specifically, the CLIMIT strategy and program plan calls for multiple CCS technologies for CO₂ capture to reduce costs and energy use.

Further, CLIMIT calls for efficient ship transport, in which low-temperature separation processes are attractive, since additional liquefaction can be avoided. The facility enables testing of CO₂ liquefaction at low pressures (e.g. 6 bar), below that of conventional ship transport (e.g. 15 bar). Lowered liquid pressure can improve the transport efficiency due to higher liquid density, lighter tanks due to the lowered operation pressure. 

With the growing focus on hydrogen production from natural gas, the RI has also been successfully used to investigate separation of syngas-derived tailgas mixtures for CO₂ capture, which is a promising processing step in combination with hydrogen-selective separation processes such as proton-conducting membranes and pressure-swing adsorption.