Co-production of cement and carbon nanotubes with a carbon negative footprint

Abstract

C2CNT (Carbon dioxide to carbon nanotube) cement plants have been introduced and analyzed which provide a significant economic incentive to eliminate the massive CO 2 greenhouse gas emissions of current plants and serves as a template for carbon mitigation in other industrial manufacturing processes. Rather than regarding CO 2 as a costly pollutant, this is accomplished by treating CO 2 as a feedstock resource to generate valuable products (carbon nanotubes). The exhaust from partial and full oxy--fuel cement plant configurations are coupled to the inlet of a C2CNT chamber in which CO 2 is transformed by electrolysis in a molten carbonate electrolyte at a steel cathode and a nickel anode. In this high yield 4e-- per CO 2 process, the CO 2 is transformed into carbon nanotubes at the cathode, and pure oxygen at the anode that is looped back in improving the cement line energy efficiency and rate of production. A partial oxy--fuel process looping the pure oxygen back in through the plant calcinator has been compared to a full oxy--fuel process in which it is looped back in through the plant kiln. The second provides the advantage of easier retrofit, while the first maximizes efficiency by minimizing the volume of gas throughput (eliminating N 2 from air).An upper limit to the electrical cost to drive C2CNT electrolysis is USD70 based on Texas wind power costs, but will be lower with fuel expenses when oxy--fuel plant energy improvements are taken account. The current value of a ton of carbon nanotubes is substantially in excess of a ton of cement. Hence a C2CNT cement plant consumes USD50 of electricity, emits no CO 2 , and produces USD100 of cement and USD60,000 of carbon nanotubes per ton of CO 2 avoided. As the cement product ages, CO 2 is spontaneously absorbed. This is a powerful economic incentive, rather than economic cost, to mitigate climate change through a carbon negative process.

Carbon Nano‐Onions Made Directly from CO2 by Molten Electrolysis for Greenhouse Gas Mitigation

“…2019, 3,1900056 The noble iridium/platinum anode in this study is purposely used here to inhibit CNT formation and enhance the observed formation of the desired CNO product by preventing introduction from the anode, migration, reduction, and formation of nickel or chromium nucleation sites on the cathode which we demonstrated favored formation of the alternative CNT product in other studies. [1,[29][30][31][32][33][34][35][36][37][38][39][40] However, an iridium or iridium alloy anode is not a prerequisite for high yield CNO growth. The inhibition of low levels of nickel migration from a nickel or nickel containing alloy anode, or a thin film iridium anode are readily envisioned and will be the topic of an ensuing study.…”

“…[23] Carbon nano-onions can also be synthesized using arc discharge, laser ablation and plasma processes, shock compression techniques, autoclave processes (catalytic and noncatalytic), and by carbonization routes, [24] thermal pyrolysis of alcohol at high 2700 K, [25] and high fluence 120 keV implantation of carbon ions into copper and silver. In 2015 we introduced a chemistry to synthesize CNTs at high yield by electrolysis of CO 2 , [1,[29][30][31][32][33][35][36][37][38][39] rather than their conventional CVD synthesis from organometallics. [6] Challenges to the bulk production of bulk carbon nano-onions has limited their commercial availability.…”

“…[35,36] High yield, low electrolysis voltage, and high uniformity CNTs were demonstrated to be produced from dissolved CO 2 in a variety of alkali and alkali-earth carbonate electrolytes, [32,33] and straight (low defect) or tangled (high defect) were controlled through the addition or exclusion of oxide added to the molten carbonate electrolyte. [35,36] High yield, low electrolysis voltage, and high uniformity CNTs were demonstrated to be produced from dissolved CO 2 in a variety of alkali and alkali-earth carbonate electrolytes, [32,33] and straight (low defect) or tangled (high defect) were controlled through the addition or exclusion of oxide added to the molten carbonate electrolyte.…”

“…We have introduced and studied the high yield, molten carbonate electrolytic transformation of CO 2 to CNTs (referred to as the "C2CNT") process' applicability to transforming CO 2 from the flue gas of fossil fuel power or cement plants to carbon nanotubes. [35,36] High yield, low electrolysis voltage, and high uniformity CNTs were demonstrated to be produced from dissolved CO 2 in a variety of alkali and alkali-earth carbonate electrolytes, [32,33] and straight (low defect) or tangled (high defect) were controlled through the addition or exclusion of oxide added to the molten carbonate electrolyte. [29,32,33,37] A variety of cathode substrates were studied as effective for the C2CNT process, and we demonstrated that very long (mm length) CNTs can be grown, and/or high conductivity CNTs, such as boron and other doped CNTs are readily formed by the controlled addition of impurities to the electrolyte during the electrosynthesis.…”

Effect of molten carbonate composition on the generation of carbon material

“…These ndings based on experiments strongly demonstrate the fact that ambient CO 2 could act as raw feedstock in industrial production, and this transformation provides a path to eliminate carbon dioxide emissions from power or cement plants. 39,42,43 XRD characterization (Fig. 5) was performed to reveal the crystal characteristics of the carbon product prepared at different molten salts composition, wherein no obvious sharp diffraction peak of carbon appears, signifying that the obtained carbon product in this work is mostly amorphous.…”