Abstract
This study proposed plastic waste-fueled Chemical-looping Hydrogen Production (CLHP) based on the concept of three-reactor chemical-looping process for the purposes of sustainable treatment of plastic wastes while producing high purity H2 and separating CO2. Oxygen carrier prepared from red mud wastes (Bauxite residues) was suggested to be circulating materials to improve combustion efficiency and H2 yield. The feasibility of using pelletized oxygen carrier prepared from red mud wastes was experimentally investigated with major components (H2, CH4 and C2H4) of plastics pyrolysis gases as fuels. The red mud oxygen carrier composed of around 38 wt% Fe2O3 and 50 wt% inert materials, and CuO-promoted oxygen carriers composed of 8.0 wt% CuO and 92 wt% red mud wastes were used. The two oxygen carriers were examined by parallel experiments, focusing on the aspects of oxygen transport, stability, hydrogen productivity and carbon deposition. Temperature and different components of plastic pyrolysis gases had significant impacts on oxygen transport behaviors; reduction tests using CH4 or C2H4 fuels suggested that the operation temperature of Fuel Reactor should be higher than 800 °C for deep reduction and high H2 productivity. CuO addition significantly promoted oxygen carrier's reactivity and oxygen transport capacity with various fuel components. The cyclic CLHP experiments, performed over 10 redox cycles with C2H4 as fuels, showed that there was only a limited degradation in oxygen carriers caused by carbon deposition and element migration. The developed oxygen carriers can meet the requirements of long-term operation for CLHP process. Carbon deposition on the oxygen carriers derived from hydrocarbon fuel cracking seemed to be inevitable, which experimentally determined in the range of 0.01–0.043 g g−1 oxygen carriers as C2H4 was used as fuels. However, the reactivity of these carbon deposits was extremely low; their initial steam-gasification temperatures were around 750 °C, much higher than the temperature used for water splitting reaction. This provides the potential opportunities for an industrial CLHP process to produce high purity H2 (>97%) despite of carbon deposits presents in Fuel Reactor.
| Original language | English |
|---|---|
| Article number | 137213 |
| Journal | Journal of Cleaner Production |
| Volume | 409 |
| DOIs | |
| State | Published - Jul 10 2023 |
Bibliographical note
Publisher Copyright:© 2023 Elsevier Ltd
Funding
Different types of carbons might be deposited directly from the polymerization of C2H4 (Huang et al., 2022), and this would pose damages to OCs. The amorphous carbon, found on the surfaces of both RM and RM_CuO, seemed to precipitate only on the reduced metal grains. During reduction step, once iron oxides grains were reduced to metallic iron, C2H4 decomposition will be catalyzed, leading to carbon polymerization on the surface. As some of these carbons permeate into the interior of OC particles via these metal grains (Liu et al., 2021), defects formed in the deposited carbon. As a result, these carbon deposits were reconstructed into amorphous carbon. On the other hand, cracks and cavities were extensively created as the carbon inside OC particles reacted fast with lattice oxygen to produce large quantities of carbon dioxide and monoxide (Tilland et al., 2016), as indicated by Fig. 9 (c) and (d). Owing to the relatively high carbon deposition occurred in reduction step, the interior of RM_CuO (RM_CuO_Reduced by C2H4_10 Cycles) showed more cracks and cavities than RM (RM _Reduced by C2H4_10 Cycles). The growth of carbon fiber without hollow central channel, as found on RM surface, can cause OC degradation too. This type of carbon fiber was seen around the grains edge, which growth followed the tip-growth model. The EDS mapping in Figs. 14 (e−1) - (e−4) showed that, the cap of carbon fiber contained Fe elements and support materials (Si-, Al-, and Ca-elements). Thus, the detach of cap may induce active component loss and OC surface disruption.This research was supported by National Natural Science Foundation of China (No. 52076042), National Key R&D Program of China (No. 2018YFB0605401-04), and “Entrepreneurship & Innovation Plan” of Jiangsu Province of China (2018). The authors gratefully acknowledge Prof. Kongzhai Li at Kunming University of Technology, China, who provided raw RM for this investigation. This research was supported by National Natural Science Foundation of China (No. 52076042 ), National Key R&D Program of China (No. 2018YFB0605401-04 ), and “Entrepreneurship & Innovation Plan” of Jiangsu Province of China ( 2018 ). The authors gratefully acknowledge Prof. Kongzhai Li at Kunming University of Technology, China, who provided raw RM for this investigation.
| Funders | Funder number |
|---|---|
| Kunming University of Science and Technology | |
| National Natural Science Foundation of China (NSFC) | 52076042 |
| National Key Research and Development Program of China | 2018YFB0605401-04 |
| “Entrepreneurship & Innovation Plan” of Jiangsu Province of China |
Keywords
- Chemical-looping
- Hydrogen production
- Oxygen carrier
- Plastic waste
- Red mud waste
ASJC Scopus subject areas
- Renewable Energy, Sustainability and the Environment
- Building and Construction
- General Environmental Science
- Strategy and Management
- Industrial and Manufacturing Engineering
