A Fair World | Notion

Industrial Innovation Choose level of difficultySimple[x] AdvancedSustainable Steel Clean Concrete Textiles PreCCCPostCCC Oxy-Fuel Carbon Utilisation Open Problems Final Quiz Get Certificate Created by Authors: Camelia Hamdi-cherif, Terese Teoh, JP Arellano, Matthieu Wilson, Susanna Raiskio, Analaura Sánchez, Pandora Dewan Artists: Tania Chiang, Ho Yee-Lee, Federica Merante, Ella Anderson, Sabrina Lam, Chris Robertson, Alex Shuttleworth, Hana Fairuzamira, Airi Iris Ryu, Ashley Betters, Mira Lu Reviewers: Anna Philips, Criodán Ó Murchú, Or Hadas, Dotan Gazith, Mairenn Collins, Eric Steinberger, Ed Hodgson, Camelia Hamdi-cherif, Terese Teoh, JP Arellano, Matthieu Wilson, Susanna Raiskio, Analaura Sánchez, Pandora Dewan External reviewers: Dr. Loh Xian Jun PreCCC: Capturing CO₂ Before We Burn it 19 minute read Updated on Thursday, February 15, 2024Click to enlarge How could we capture carbon instead of emitting it? For some industries, it’s really tricky not to create CO2. So, wouldn’t it be cool if we could capture CO₂ before it is emitted into the atmosphere and then store it somewhere (like underground)? Well, we can! This process is called carbon capture and storage (CCS).

Unlike carbon dioxide removal (CDR), which focuses on extracting existing CO₂ from the air to combat climate change, CCS targets emissions at their source. (To learn more about CDR, check out our Undo Climate Change course!)

Now, back to CCS.

CCS can help remove emissions from many different manufacturing and industrial processes; wherever CO₂ is released from burning, high temperatures or chemical reactions, CCS could be used to capture and store it! CCS in natural gas and coal power plants is particularly interesting. It allows us to eliminate the emissions from existing fossil fuel power plants as we transition to cleaner forms of energy production.

Although this is promising and even exciting, it's important to note that this is not an excuse to build more fossil fuel power plants nor keep current ones running for longer than necessary.

So let's take deep dive into this novel technology! There are three ways to capture carbon: • Pre-combustion carbon capture (preCCC): Here, carbon (in the form of CO₂) is removed from fossil fuels in a reactor before being burnt. • Post-combustion carbon capture (postCCC): Here, carbon (in the form of CO₂) is removed after the fossil fuels are burnt. • Oxy-fuel combustion: Here, pure oxygen is used to burn the fossil fuel, resulting in a relatively pure stream of CO₂, which is easier to capture.The captured CO₂ needs to be appropriately stored for all three methods. Why is this so important?[ ] If it isn’t stored properly, it could explode[ ] If it isn’t stored properly, it could leak back out into the atmosphere, undoing the work of storing it[ ] If it isn’t stored properly, it could cause small seismic events[ ] It isn’t important; it doesn’t matterTake a guess! So, let’s look at how the carbon is actually captured, starting with preCCC and then going on to postCCC and oxy-fuel combustion in the following chapters.

What is preCCC, and why is it useful? Fossil fuels, like coal and natural gas, are what chemists call hydrocarbons. These are compounds made up of hydrogen (H) and carbon (C). When burnt (combusted) in the presence of air, they transform into molecules like CO₂ and H₂O.Which of the following fuels produces the lowest levels of pollutants?HydrogenCoalNatural gasTake a guess! The process of preCCC turns fossil fuel hydrocarbons into hydrogen (H₂) and carbon dioxide (CO₂) before they are combusted. The hydrogen is then used as a much cleaner energy source (see our energy course) while the CO₂ is captured and stored, avoiding its emission into the atmosphere! How does preCCC work?Click to enlargeSimplified diagram of how preCCC works Let’s go through this step-by-step! Although the process works for natural gas and coal plants, we’ll only cover natural gas here. Gas is cheaper, and it is not currently economically feasible to add CCS to older coal plants as they have a shorter operating life left. 1. Syngas production Firstly, we need to break down the hydrocarbon into what is called syngas, a mixture of mostly carbon monoxide (CO) and hydrogen (H₂). The most common method of achieving this is steam reforming. So how does it work?

At high temperatures (750-900०C) and low pressures, steam (vaporised H₂O, also known as water vapour) can be used to split natural gas into CO and H₂. Click to enlargeSteam reforming natural gas to produce syngas 2. Removing impuritiesWhy do you think impurities need to be removed?[ ] Impurities can get lost in the system[ ] Impurities can cause corrosion of component parts[ ] Impurities make the fuel look messy[ ] Impurities can increase the pollutant emissions into the environmentTake a guess! The fuel needs to have impurities removed to avoid damaging the turbine (which generates electricity) and reduce pollutant emissions. If the initial fossil fuel were coal (a dirtier fuel source that would produce more impurities), then more filtering stages would be needed. 3. Water-gas shift reaction The CO in the syngas is then converted to CO₂ by reacting it with steam. This creates even more H₂ that can be used as fuel:Click to enlargeCreating more H₂ (to use as fuel) by reacting the syngas with steam This means that the overall reaction from natural gas (mostly CH₄) to CO₂ and H₂ looks like this:Click to enlargeThe overall reaction to convert natural gas (mostly CH₄) into CO₂ and H₂ with the aid of catalysts to speed up the reaction 4. Separation and storage The CO₂ then needs to be separated from the H₂. Absorption of the CO₂ into a physical solvent is currently the most common (and cheapest) method for capturing the CO₂, which is then, finally, transported into storage. We are now left with just H₂!What happens to hydrogen (H₂) when it is burnt?Reacts with oxygen to form water, H₂OReacts with carbon to form hydrocarbonsDoes nothingTake a guess! By producing water rather than CO₂, hydrogen acts as a much cleaner energy source than the initial fossil fuel! How feasible is preCCC?Click to enlargeIncreased costs and decreased efficiencies of using preCCC in a gas power plantWhy isn’t preCCC more widely used?It is cheaper for companies to pay a tax on carbon insteadWe don’t know how to do itNobody is interestedIt takes too longTake a guess! As we can see, installing and running preCCC in a gas power plant increases the cost of the energy output from the plant. It also decreases the efficiency of the plant because of the added energy required to run the preCCC systems. It is cheaper for companies to pay a tax for their emissions than to install preCCC technologies, and in many places, carbon isn’t even taxed at all! At what stage is the technology right now? There are currently no test plants for natural gas-fueled preCCC power, and the first coal power plant with preCCC faced delays and cost 2.3 times as much as expected. So, there would need to be a lot of research, development and testing if preCCC is to become more common, all of which require time and money. What will preCCC be like in the future? Reducing the energy requirements of preCCC will be needed to make this technology efficient and cost-effective in the future. Energy demands from the process can be reduced in two main ways: reducing how much steam is used (because producing steam requires lots of energy) or combining the conversion of CO to CO₂ and the removal of CO₂ into one step. To understand why, let’s look back at the water-gas shift reaction:Click to enlargeThe reversible water-gas shift reaction This is a reversible reaction that reaches an equilibrium, or balance, when the forward and reverse reactions have constant rates. Once the reaction reaches an equilibrium, it is possible to cause the reaction to shift by altering the temperatures, concentrations, and pressures that it occurs. For example, if we change the concentration by adding or removing molecules, the reaction will adjust to counteract the change. What do you think happens to this reaction if we remove the CO₂ as it is being produced?NothingThe forward reaction speeds up to replace the removed CO₂The reaction stops because we are removing CO₂Take a guess! For the water-gas shift reaction, we want to produce as much H₂ as possible, so let’s see how removing some of the products might help us:Click to enlargeThis is why removing CO₂ and H₂ from the reaction causes it to shift and produce more CO₂ and H₂ Suppose we continuously remove H₂ and CO₂ during the reaction. In that case, we will constantly be changing the concentrations of these molecules on the right side of the reaction, causing the equilibrium to adjust (shift further to the right) to counteract this change. Therefore, the CO and H₂O will react together faster to replace these missing products. In summary, by constantly removing CO₂ and H₂ during the water-gas shift reaction, we get more H₂ and CO₂ produced overall. There exist specific types of membranes that are capable of removing the H₂ as it is produced. This results in the same effect as above! So that covers the basics of preCCC, let’s now look at postCCC! What did you think of this chapter? Not good Okay Good Awesome Thank you!Give FeedbackNext ChapterPrivacy & Cookie Policy Terms of Use Copyright © 2024 Climate Science Ltd. All rights reserved

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