Transporting frozen CO2 by box container

- seeking research project partners

Henrik O Madsen, former CEO of DNV, is seeking partners for a Euro 2m project to assess the transport of CO2 in frozen, pelletised form in box containers

Original article found in Carbon Capture Journal

Jul 28 2023

Does it make sense to transport CO2 as frozen pellets in a box container?

There is growing discussion in the industry about the need to transport CO2 by ship where pipelines are not available. The discussions usually lead to the assumption that the best way to do it is with tankers, carrying CO2 as a liquid.

But there are disadvantages to using tankers. They are expensive to build. To achieve a low cost per tonne transported, we will need large tankers, which means higher upfront expenditure, which is hard to get funded. Such large vessels may only serve a single CO2 source and CO2 injection point. And many berths do not have the water depth or space to accommodate large vessels.

If there is a need to move CO2 on land, the only option normally considered is transporting it in liquid form in a road tanker, although very few high pressure, low temperature road tankers have been built.

If the CO2 is frozen into pellets and put into box containers instead, we can make use of the existing, low-cost box container infrastructure we already have.

We will need a design of containers with thick (25cm) insulation, which does not sound too complicated. Also, a system for discharging the CO2 pellets into another device, where the CO2 can be transformed into a liquid or high-pressure gas, ready for pipeline transport and injection into the subsurface. This also does not sound too complicated.

The critical issues are probably the energy cost of freezing CO2 into pellets, and the amount of CO2 in the box container which gasifies and escapes through the pressure release valve.

Also whether there would be public and regulatory acceptance for a box container which would slowly emit very small amounts of CO2 as some of the CO2 gasifes due to the insulation not being 100 per cent resistant to flow of heat.

The only way to find these answers is to investigate in more depth and probably to build prototype systems.

Companies may be willing to pay Euro 20 per tonne for the transport part of the capture, transport, and storage process.

The box container transport option has another advantage over tanker shipping, in that the container can be used as intermediate storage as well as for transport – no onshore storage tanks are required. The box container can easily be moved along land as well as by sea.

Moving CO2 by box container could also make it easier to bring into e-fuel production, where hydrogen made from renewables is reacted with CO2 to make a liquid fuel.

The frozen CO2 can be transported at atmospheric pressure, while liquified CO2 requires a pressure of above 5 bar. This adds to the cost of making a tanker. It means transport as a solid is easier and safer. (Note there can be safety implications if solid CO2 gasifies and leaks, such as if CO2 displaces oxygen and makes atmosphere impossible to breathe in, or if it causes frostbite).

Solid CO2 exists at atmospheric pressure and temperature of about -80 degrees C.

Henrik O Madsen, who served as CEO of DNV from 2006 to 2015, is interested in putting together a team of companies to fund a project to investigate the viability. He estimates that the technology could be fully evaluated and developed to technology readiness level 6, “system prototype demonstration in a relevant environment” for Euro 2m.

Exploring the feasibility

The big question is probably the energy cost of converting gas phase CO2 into solid pellets. Mr Madsen estimates that the energy cost of converting CO2 into pellets is double the cost of liquefying it.

Technology to convert liquid CO2 into pellets, known as ’dry ice,’ is commercially available. For example, an off the shelf “dry ice pelletiser” is available from ASCO Carbon Dioxide Inc, a company headquartered in Switzerland. According to data on its website, it costs $150k, with capacity of 750kg/hr, power consumption of 19 KW, and dimensions 1.7 x 1.1 x 3.86m.

These CO2 dry ice pellets are used for sandblasting, for cleaning up fire damaged properties, aged brick, and stonework.

Mr Madsen envisages that there could be twenty-five tonnes CO2 stored in a standard 20-foot container. Standard box containers normally take 21.6 tonnes, and” heavy tested” higher specification containers normally take twenty-eight tonnes.

The box container would be fitted with 25 cm thick insulation, about ten times stronger than what is normally used in refrigerated containers. There would not need to be any active cooling system on the container. Mr Madsen envisages that the solid CO2 would gasify at about 0.1 to 0.2 per cent per day, released through a pressure release valve, which should be acceptable. The CO2 could be poured into the container in pellet form.

Container transport cost itself can be pretty cheap – for example the costs of shipping a twenty-foot box from Felixstowe (UK) to Rotterdam can be around $500, according to online estimates. If this carries 25 tonnes of CO2, then the cost per tonne is just $20. This cost is based on booking a single container - with large volume contracts, perhaps chartering a whole container ship, it would be much lower. "The transport cost should we well within the boundaries of what the value chain can absorb," Mr Madsen says.

The CO2 would need to be converted to gas form for injection into the subsurface. Mr Madsen envisages this could be done by loading the CO2 into a pressurized receiving facility, where it would be converted to liquid form, so it can flow through a pipeline. Some energy must be added, such as from sea water at atmospheric temperature, using a heat exchanger.

Project proposal

Mr Madsen is seeking funding of Euro 2m to develop the project, including developing systems to freeze CO2, design of the container, design of the loading and unloading systems, constructing a prototype container, evaluating transport economics, reviewing offloading options, building a prototype receiving facility, evaluating safety and regulatory requirements, economic analysis, making communications and training material, studying Co2 thermodynamics, studying insulation materials, reviewing port safety, and overall project management.

He envisages that this funding could be found from 4-5 main sponsors contributing Euro 300k, 5- 7 sponsors contributing Euro 100k, and further participants joining on an ‘in-kind’ basis.

The project team does not intend to assert IP rights for any individual elements or for the complete system – the ‘technology’ will be free to use. However individual partners developing specific technology elements, such as the refrigerated container design or receiving facility, may choose to assert IP rights for their own contributions.

Mr Madsen seeks for the project to run from Oct 1, 2023, to July 31, 2024,

He is not seeking to make a profit out of the project, just covering his own direct costs and a fee for management.

Mr Madsen can be contacted on henrikomadsen@gmail.com

See https://www.decarbonice.org/