Enhanced CO2 Capture Performance of Limestone by Industrial Waste Sludge

Hydrogen Production with In Situ CO2 Capture at High and Medium Temperatures Using Solid Sorbents

Hydrogen is a versatile vector for heat and power, mobility, and stationary applications. Steam methane reforming and coal gasification have been, until now, the main technologies for H2 production, and in the shorter term may remain due to the current costs of green H2. To minimize the carbon footprint of these technologies, the capture of CO2 emitted is a priority. The in situ capture of CO2 during the reforming and gasification processes, or even during the syngas upgrade by water–gas shift (WGS) reaction, is especially profitable since it contributes to an additional production of H2. This includes biomass gasification processes, where CO2 capture can also contribute to negative emissions. In the sorption-enhanced processes, the WGS reaction and the CO2 capture occur simultaneously, the selection of suitable CO2 sorbents, i.e., with high activity and stability, being a crucial aspect for their success. This review identifies and describes the solid sorbents with more potential for in situ CO2 capture at high and medium temperatures, i.e., Ca- or alkali-based sorbents, and Mg-based sorbents, respectively. The effects of temperature, steam and pressure on sorbents’ performance and H2 production during the sorption-enhanced processes are discussed, as well as the influence of catalyst–sorbent arrangement, i.e., hybrid/mixed or sequential configuration.

Blending Wastes of Marble Powder and Dolomite Sorbents for Calcium-Looping CO2 Capture under Realistic Industrial Calcination Conditions

The use of wastes of marble powder (WMP) and dolomite as sorbents for CO₂ capture is extremely promising to make the Ca-looping (CaL) process a more sustainable and eco-friendly technology. For the downstream utilization of CO₂, it is more realistic to produce a concentrated CO₂ stream in the calcination step of the CaL process, so more severe conditions are required in the calciner, such as an atmosphere with high concentration of CO₂ (>70%), which implies higher calcination temperatures (>900 °C). In this work, experimental CaL tests were carried out in a fixed bed reactor using natural CaO-based sorbent precursors, such as WMP, dolomite and their blend, under mild (800 °C, N₂) and realistic (930 °C, 80% CO₂) calcination conditions, and the sorbents CO₂ carrying capacity along the cycles was compared. A blend of WMP with dolomite was tested as an approach to improve the CO₂ carrying capacity of WMP. As regards the realistic calcination under high CO₂ concentration at high temperature, there is a strong synergetic effect of inert MgO grains of calcined dolomite in the blended WMP + dolomite sorbent that leads to an improved stability along the cycles when compared with WMP used separately. Hence, it is a promising approach to tailor cheap waste-based blended sorbents with improved carrying capacity and stability along the cycles under realistic calcination conditions.

CO2 Capture at Medium to High Temperature Using Solid Oxide-Based Sorbents: Fundamental Aspects, Mechanistic Insights, and Recent Advances

Carbon dioxide capture and mitigation form a key part of the technological response to combat climate change and reduce CO₂ emissions. Solid materials capable of reversibly absorbing CO₂ have been the focus of intense research for the past two decades, with promising stability and low energy costs to implement and operate compared to the more widely used liquid amines. In this review, we explore the fundamental aspects underpinning solid CO₂ sorbents based on alkali and alkaline earth metal oxides operating at medium to high temperature: how their structure, chemical composition, and morphology impact their performance and long-term use. Various optimization strategies are outlined to improve upon the most promising materials, and we combine recent advances across disparate scientific disciplines, including materials discovery, synthesis, and in situ characterization, to present a coherent understanding of the mechanisms of CO₂ absorption both at surfaces and within solid materials.

Simultaneous CO2 capture and heat storage by a Ca/Mg-based composite in coupling calcium looping and CaO/Ca(OH)2 cycles using air as a heat transfer fluid

The Ca/Mg-based composite prepared from carbide slag and dolomite is efficient for simultaneous CO₂ capture and heat storage.

Porous spherical calcium aluminate-supported CaO-based pellets manufactured via biomass-templated extrusion-spheronization technique for cyclic CO2 capture

Calcium looping has been proposed as one of the most promising technologies for CO₂ capture to mitigate the growing problem of global warming. However, the loss in capacity and attrition are two issues lying on the way to practical application for calcium looping process. To improve CO₂ capture performance and mechanical strength of CaO sorbents, a biomass templated extrusion-spheronization palletization technique was employed to manufacture porous calcium aluminate-supported CaO-based pellets. For the first time, this work investigated the granulation of calcium aluminate-supported CaO-based sorbents and also the effectiveness of three novel biomass-based pore-creating materials of straw, willow, and wheat. The results indicated that the incorporation of calcium aluminate-based supports could effectively enhance cyclic performance and stability. Besides, the 5 wt.% addition of pore-creating materials could further promote the cyclic CO₂ capture capacity of calcium aluminate-supported CaO-based pellets. The pellets added with 25 wt.% calcium aluminate-based supports and 5 wt.% straw still held a good carbonation conversion of 46.45% after 50 cycles even tested under CO₂-rich calcination atmospheres. In addition, the anti-attrition ability tests by friability tester (FT) demonstrated that all the prepared pellets owned an excellent degree of attrition (less than 1%). The good CO₂ capture performance and mechanical strength endowed biomass-templated calcium aluminate-supported CaO-based pellets with promising prospects for practical CO₂ removal.