27 lines
4.8 KiB
Markdown
27 lines
4.8 KiB
Markdown
---
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title: "Calcium looping"
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chunk: 4/6
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source: "https://en.wikipedia.org/wiki/Calcium_looping"
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category: "reference"
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tags: "science, encyclopedia"
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date_saved: "2026-05-05T10:46:20.922266+00:00"
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instance: "kb-cron"
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---
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=== Cost per metric ton for CO2 captured ===
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Firstly, Ca-looping offers greater cost advantage compared to conventional amine-scrubbing technologies. The cost/metric ton for CO2 captured through Ca-looping is ~$23.70 whereas that for CO2 captured through amine scrubbing is about $35–$96. This can be attributed to the high availability and low cost of the CaO sorbent (derived from limestone) as compared to MEA. Also, Ca-looping imposes a lower energy penalty than amine scrubbing, resulting in lower energy costs. The amine scrubbing process is energy intensive, with approximately 67% of the operating costs going into steam requirements for solvent regeneration. A more detailed comparison of Ca-looping and amine scrubbing is shown below.
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=== Cost of CO2 emissions avoided through Ca-looping ===
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In addition, the cost of CO2 emissions avoided through Ca-looping is lower than the cost of emissions avoided via an oxyfuel combustion process (~US$23.8/t). This can be explained by the fact that, despite the capital costs incurred in constructing the carbonator for Ca-looping, CO2 will not only be captured from the oxy-fired combustion, but also from the main combustor (before the carbonator). The oxygen required in the calciners is only 1/3 that required for an oxyfuel process, lowering air separation unit capital costs and operating costs.
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Sensitivity Analysis: Figure 3 shows how varying 8 separate parameters affects the cost/metric ton of CO2 captured through Ca-looping. It is evident that the dominant variables that affect cost are related to sorbent use, the Ca/C ratio and the CaO deactivation ratio. This is because the large sorbent quantities required dominate the economics of the capture process. Low costs of CO2 avoided for the indirectly heated Ca-looping process have been reported for integrated concepts in the lime production.
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These variables should therefore be taken into account to achieve further cost reductions in the Ca-looping process. The cost of limestone is largely driven by market forces, and is outside the control of the plant. Currently, carbonators require a Ca/C ratio of 4 for effective CO2 capture. However, if the Ca/C ratio or CaO deactivation is reduced (i.e. the sorbent can be made to work more efficiently), the reduction in material consumption and waste can lower feedstock demand and operating costs.
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=== Cement production ===
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Finally, favorable economics can be achieved by using the purged material from the calcium looping cycle in cement production. The raw feed for cement production includes ~ 85 wt% limestone with the remaining material consisting of clay and additives (e.g. SiO2, Al2O3 etc.). The first step in the process involves calcinating limestone to produce CaO, which is then mixed with other materials in a kiln to produce clinker.
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Using purged material from a Ca-looping system would reduce the raw material costs for cement production. Waste CaO and ash can be used in place of CaCO3 (the main constituent cement feed). The ash could also fulfill the aluminosilicate requirements otherwise supplied by additives. Since over 60% of the energy used in cement production goes into heat input for the precalciner, this integration with Ca-looping and the consequent reduced need for a calcination step, could lead to substantial energy savings (EU, 2001). However, there are problems with using the waste CaO in cement manufacture. If the technology is applied on a large scale, the purge rate of CaO should be optimized to minimize waste.
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=== Waste incineration ===
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There are two main approaches to capturing CO2 from waste incineration facilities and waste-to-energy (WtE) plants. The first one is by using a tail-end CaL process to retrofit existing plants at the back-end. This has the advantage of avoiding excessive modifications of the existing facility, but can significantly increase the space requirements. A second option is to integrate the CaL process by replacing an existing incineration line. In this configuration, the calciner is fired with pre-treated waste, contributing to the waste incineration capacity to the plant. This integrated concept has several advantages, including less space requirements and lower investment costs. The integrated CaL configuration has the lowest CO2 avoidance costs of any capture technology for WtE plants due to the fact that it utilizes waste to obtain the energy for the separation. The avoidance costs have been estimated at 27 €2024/tCO2,av.
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== Political and environmental implications ==
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To fully gauge the viability of calcium looping as a capture process, it is necessary to consider the political, environmental, and health effects of the process as well. |