Understandable Earth Science

Posts tagged ‘CCS’

Gas sample collection at PACT – Investigating how the CC influences monitoring of the S!

In January 2016, Stuart Gilfillan and I (Stephanie Flude) made the long drive from Edinburgh to Beighton, Sheffield to collect some gas samples from UKCCSRC’s Pilot-Scale Advanced CO2-Capture Technology (PACT) facility. The PACT facility hosts a state of the art, pilot-scale CO2 amine-capture plant that can capture CO2 in flue gases from either a 250kW air/oxyfuel combustion plant (that can burn coal, biomass or gas) or one of the two 330kW gas turbines also hosted at the facility.

The PACT Core Facility entrance and the amine capture absorber and desorber columns.

As we are Earth Scientists, rather than Engineers, we are researching reliable means to trace the fate of CO2 once it has been injected below ground for geological storage. As part of that research we are investigating how the captured CO2 itself can be used as a geochemical tracer. This means I have spent much of the last couple of years tracking down sources of man-made CO2 to sample, and swapping my usual field gear – walking boots, waterproof coat and rock hammer – for steel toe capped shoes, hi-vis jackets, torque wrenches and high pressure hosing. We wanted to collect as many different types of CO2 as possible – from different capture techniques and from different feedstocks, and so collecting samples from PACT was an obvious option.

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Our typical gas sampling equipment – no rock hammers here!

We had arranged to visit while both biomass and natural gas were being air-combusted in the 250 kW plant, allowing us to collect samples derived from two different fuel stocks. We were also hoping to collect gas samples from different parts of the carbon capture system, so we could better understand, and ultimately predict, what controls the inherent fingerprint of captured CO2. For this, we wanted to collect samples of the fuel, the combustion flue gas, the residual gas from the amine absorber column, and the final captured CO2:

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Schematic of our ideal gas sampling strategy.

The staff at PACT were very keen to help us collect this range of samples, but early discussions raised some problems with how to collect the samples. The PACT facility had been designed incredibly efficiently, with multiple gas analysis instruments housed on site that directly tap and analyse the gas of interest. Unfortunately for us, this efficient design meant that very few external sampling ports were installed on the system – why add sample ports when you can simply flow the gas you want straight to your analyser? After discussions with Kris Milkowski and Martin Murphy, we settled on the idea of collecting samples from the exhaust vent of PACT’s FTIR system, with some supplementary samples collected straight from an external tap on a combustion flue gas pipe.

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Stuart collecting a sample of combustion flue gas from the flue pipe

Once on site, we spent a few minutes working out the best way to connect our sampling equipment (copper tubes, clamps, and gas-sample bags) to the available ports and how to ensure a strong enough flow of gas to sample. We collected from the flue pipe first and then moved across to the FTIR hut. Sampling here was a little more hectic as we had a 4 minute window to collect the sample while the FTIR was purging the gas of interest. We need to be very careful to avoid air contamination in our samples, and standard procedure for this is to purge our equipment with the gas we are collecting for at least two minutes, leaving just two minutes to collect the sample and hook up the sampling assembly for the next sample.

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Stuart explaining our sampling procedure to Kris in the FTIR hut.

By the end of the visit, we had managed to collect combustion flue gas, absorber outlet, and captured CO2 from both gas and biomass feedstocks. With the critical sampling tasks out of the way, we were treated to a tour of the combustion rig by János Szuhánszki.

Janos introducing Steph and Stuart to the combustion rig.

So what happens next? We have spent the last year analysing the samples for their inherent geochemical and isotopic fingerprint.  We have measured the carbon and oxygen isotope composition (δ13C and δ18O) of the captured CO2, and concentrations and isotope ratios of trace noble gases (helium, neon, argon, krypton and xenon) that are present in the captured CO2 stream. The results have just been submitted in a manuscript to the International Journal of Greenhouse Gas Control, so keep an eye open for that in the near future.

A version of this article also appears on the UKCCSRC Blog site.

What CCS is and (perhaps more importantly) what it isn’t!

I’ve noticed that there seems to be a lot of anti-CCS views being aired on Twitter at the moment, along with some CCS news articles that are factually incorrect (see bottom of this post).

So here is a quick overview of what CCS is and isn’t. I intend to write more detailed blogs discussing these points sometime soon – just need to find the time.

So, what is CCS?

  • CCS stands for carbon capture and storage
  • CO₂ is captured from energy production and industry. That CO₂ would otherwise end up in the atmosphere and cause global warming.
  • The captured CO₂ is permanently* stored deep (2-3 km) underground in pore spaces in the rock.
  • CCS is the only feasible way of reducing CO₂ emissions from industry – especially the steel industry, necessary for building wind turbines!
  • CCS is a way to reduce CO₂ emissions while we are transitioning from a fossil-fuel to low-carbon energy infrastructure.
  • CCS is a fully developed and tested technology.
  • CCS is a potential way of getting negative CO₂ emissions – i.e. reducing CO₂ in the atmosphere by combining CCS with burning of biofuels for energy.
  • Implementing CCS is cheaper than dealing with the consequences of global warming.

* CO₂ will be stored deep in rocks on the timescale of thousands to millions of years. So technically not “permanently” on a geological timescale, but permanent on a human timescale and easily long enough to buffer global warming.

Now to address some of the misconceptions about CCS.

What CCS is NOT:

  • CCS is NOT an excuse to keep burning fossil fuels indefinitely.
    • CCS can minimise CO₂ emissions while we transition from a fossil-fuel to a low-carbon energy infrastructure over the next 50-100 years. I do not know anybody working with CCS that thinks it is a long term solution that will let us keep burning fossil fuels.
  • CCS is NOT unnecessary for reducing our CO₂ emissions.
    • Many reports (including IPCC) show CCS is needed to meet climate targets.
    • Existing energy infrastructure cannot yet cope with the intermittency of many forms of renewable energy.
    • CCS is currently the only way to reduce industry CO₂ emissions.
  • CCS is NOT storing CO₂ in caves / fractures.
    • In the vast majority of storage sites, CO₂ is and will be stored in rock pore spaces many kilometres underground. Up to 20% of the volume of a rock can be empty space – think of a box of marbles and the gaps between the marbles. That is where the CO₂ will sit. And the storage rocks are deep, with many impermeably layers on top of them which means the CO₂ will not leak out of the ground.
  • CCS is NOT a new, un-tested technology.
    • Lots of CCS pilot-projects exist that show CO₂ can be captured at large scale from power plants, and the world’s first CCS power station –Boundary Dam – was opened in Canada last year (2014).
    • The storage technology behind CCS has been used for years in the oil industry for something called enhanced oil recovery (EOR) where CO₂ is pumped into an oil field to get more oil out of the ground, and there are lots of storage pilot projects that show that the CO₂ can be injected into deep rocks, without causing earthquakes and without leaking.

What CCS is and is not

So, onto the newspapers that are getting their facts wrong.

On January 6th 2015, The Guardian published this article, including the following paragraph:

“CCS is strongly supported by energy companies like Shell. It involves the sequestration and piping of carbon dioxide into underground fissures and currently aids fossil fuel extraction, as well as allowing their continued burning long into the 21st century.”

Carbon dioxide is NOT pumped into underground fissures! It is injected into pore space in rocks!

Then we have this pleasantly optimistic article in the Irish Times published on January 8th 2015 that contains 2 slip-ups I feel need correcting.

Firstly is this paragraph with similar problems to the Guardian article:

 “Statoil has been trying out CCS at its Sleipner natural gas field in the North Sea since 1996. Since then, it has injected some 14 million tons of carbon dioxide into geological caverns and “successfully” proved that it is technically feasible, the company’s Olav Skalmerås said in Bonn.”

There are no caverns in the Sleipner natural gas field. The CO₂ stored in Sleipner (and the natural gas that has been stored in the rocks at Sleipner for thousands to millions of years) exists in the pore spaces between grains in the rock. For more information, see this article by the British Geological Survey.

Next was this paragraph:

“Novel approaches to carbon capture are also being tested. One €8.75 million project in Iceland called CarbFix, which has EU support, involves capturing carbon dioxide from a power station, dissolving it in water and effectively “mineralising” it as basalt for injection into volcanic fields.”

This is a different kind of technology from most CCS storage projects; here the CO₂ is stored by reacting it to make a solid mineral. Maybe I am nit-picking, but “effectively “mineralising” it as a basalt” is incorrect. Basalt is not a mineral – it is a rock (a volcanic rock that forms from lava flows, like the current Bárðabunga / Holohraun / Nornahraun eruption). In this project, basalt is the storage rock that the CO₂ is being injected into. The CO₂ reacts with calcium in the basalt to produce a carbonate mineral called calcite, which should be stable for thousands to millions of years. For more information, see the CarbFix website.