Carbon capture at moderate pressures and temperatures

• Moderate pressures around 15 bar

• Moderate temperatures– Hydrate formation at 2-6 oC

• Not far below cooling water temperatures in Nordic countries

– CO2 release 20 – 40 oC• Typical waste heat temperatures

Main concept overview

A closed process involving cooling, heating, compression and decompression stages to form and melt CO2 hydrates

Flue gas

99% CO2 1% N2

N2Traces of CO2

15% CO285% N2

Hydrate promoter (formation pressure)

Seed particles (reaction kinetics)

Electric powerCooling waterWaste heat

The separation is possiblesince CO2 forms hydrates more easily than N2.

The problem with hydrate processes

• There is usually a long induction time before hydrate production start– Seed must form and grow to a certain size before detectable gas

absorption is observed – This takes a long time – hours and days in pure systems

• The hydrate forms first where the gas concentration is high– Thus a droplet gets a hydrate crust around a wet inside

• This hinders the transport of gas into the water phase• And heat away from the reaction centre

• Speeding up the process – the IFE contribution and a possible breakthrough– Using heterogeneous seed particle to speed up hydrate

formation – induction time reduced by a factor of 200

Comparing to chilled ammonia process

• From literature chilled ammonia process consumes energy in the range:– 470 – 550 kWh/ton CO2

• A first rough estimate for a hydrate process:– 220 – 330 kW/ton CO2 (0.8 – 1.2 GJ)