Hall G, am, Day 4 Thursday Abstracts

Session S7. Carbon capture, utilization, and storage (CCUS)

CCUS (Carbon Capture, Utilization and Storage) is an important choice for a sustainable low-carbon development in China. The Chinese government attaches great importance to guiding the development of CCUS technology and has taken a series of measures to reduce CO₂ emission in the past decade. This speech provides an overview of CCUS technology development which contained specific details about supported program from National Key R&D Program of China. The speech will also introduce several leading large-scale CCUS industrial demonstrations in China, by summarizing the technical characteristics, reactivity, and procedural scheme of each demonstration. An outlook on future development will be provided according to the 13th Five-Year Plan of China (2016-2020), which is focused on promoting large-scale industrial demonstration in the coal-based industry and oil and gas exploration industry.
One of the promising CO₂ utilization demonstration projects is carbonation curing of concrete. CO₂ curing technology has two major benefits: (i) rapid strength gain of cementitious materials, and (ii) large-scale CO₂ sequestration in concrete. The gas-solid reaction kinetics between CO₂ and cement-based materials were studied. According to the fitting results of different kinetic models, the carbonation curing of concrete showed a progressive product-layer-diffusion limited kinetics despite different factors. Our group also evaluated the feasibility of blending calcium silicate (CS) as intensified addition, which was found to significantly enhance the reaction rate and CO₂ uptake capacity. In terms of practical feasibility, carbonation curing also improved the compressive performance of cement paste with CS. In addition, three typical industrial solid wastes - fly ash, blast furnace slag, and red mud - were studied to replace part of the cement materials to reduce CO₂ emissions. The effects of carbonation curing time, pressure, and water-to-solids ratio on the CO₂ uptake and compressive strength were comprehensively studied.

As one of the most important technologies for Carbon dioxide (CO₂) Capture, Utilization and Storage (CCUS), the practical application of CO₂ enhanced oil recovery (CO₂-EOR) has been growing rapidly. Since the profitability of CO₂-EOR project can be improved by the re-use of CO₂ contained in the associated gas, superior CO₂ separation technology is essential. JGC Corporation (JGC) and NGK Insulators, Ltd. (NGK) have developed CO₂ separation system with DDR-type zeolite membrane. In many cases, the associated gas also contains hydrocarbons in which predominant constituent is methane (CH₄). Since DDR-type zeolite has subnano-size pores which are desirable for CO₂/CH₄ separation, this membrane achieves excellent CO₂ permselectivity. In addition, this system can be operated under high CO₂ partial pressure conditions (~ 8 MPa) which is suitable for CO₂ recovery process from associated gas with high pressure and high concentration of CO₂. Recently, JGC has launched the first field test with laboratory scale DDR-type zeolite membrane at a CO₂-EOR oil field. The membrane was prepared onto the inner surface of 30 channels in a cylindrical monolithic alumina substrate (diameter: 30 mm, length: 160 mm). In this field test, it has been confirmed that this membrane performed well for CO₂ separation from the associated gas. It's of note that the performance observed using the associated gas was substantially equivalent to that of obtained using a simulated gas consisting of CO₂ and light hydrocarbons in laboratory tests. In this presentation, the features of the DDR-type zeolite membrane as well as the summary of the first field test at a CO₂-EOR oil field are addressed. In addition, the outline of the ongoing demonstration project with commercial scale DDR-type zeolite membrane (diameter: 180 mm, length: 1,000 mm) is introduced.

Along with the growth of CO₂ enhanced oil recovery (CO₂-EOR) industries, demand of CO₂ separation technologies has been increasing to recover CO₂ from associated gas which contains not only CO₂ but also hydrocarbons mainly CH₄. DDR-type zeolite membrane has the subnano-size pores which are preferable for CO₂/CH₄ separation, resulting in the excellent CO₂ permselectivity. In this study, CO₂ permeance and selectivity of the DDR-type zeolite membrane were examined under high pressure conditions using CO₂/CH₄ binary gas mixture to evaluate the potential applicability for CO₂ recovery process in CO₂-EOR industries. The membrane was prepared onto the inner surface of multi channels in a cylindrical monolithic alumina substrate (diameter: 30 mm, length: 160 mm). The membrane properties are investigated using one channel of the substrate. The test pressure was increased up to 8 MPaG with the temperature range of 90 - 150 deg. C. The CO₂ concentration in the gas mixtures were varied from 50 to 100 %. From these experiments, CO₂ permeance decreased with increasing pressure and temperature. In addition, CO₂ permeance and selectivity decreased with decreasing CO₂ partial pressure in the experiments with CO₂/CH₄ binary gas mixture. CO₂ permeance obtained in experiments was correlated by the surface diffusion model coupled with adsorption isotherm equations (Langmuir equation and Dubinin-Astakhov equation). The surface diffusion model could correlate CO₂ permeances well against the wide range of CO₂ partial pressure. The comparison of CO₂ adsorption curves estimated by the correlation was implied that the competitive adsorption between CO₂ and CH₄ was occurred in this system and it affected to CO₂ permeability of the DDR-type zeolite membrane. As mentioned above, the amount of adsorbed CO₂ decreased as CH₄ concentration in binary gas increased because of competitive adsorption. In contrast, gas diffusion constant and equilibrium constant were not changed.

High surface area magnesium oxide (MgO) has garnered interest as an in-situ CO₂ sorbent for the water-gas shift reaction (WGSR) for its low regeneration temperature and uptake of CO₂ gas at intermediate temperatures of 300 °C upon modification with alkali nitrate salts. Semi-industrial scale production of these high surface area MgO sorbents (>200 m²·g^-1) can be achieved via Calix's flash calcination process. Upon modification with NaNO₃, the CO₂ uptake of MgO in a pure CO₂ environment after 1 h improved by a factor of 27 to 11.1 mmol CO₂·g^-1. The sorbent retained 60% of its CO₂ capacity after 40 adsorption-desorption cycles, outperforming a commercial MgO control. The higher uptake of the NaNO₃ modified high surface area MgO is attributed to a higher ratio of NaNO₃ to MgO, resulting in larger and more similarly sized crystallites of MgO and NaNO₃. This improves the extent of interphase boundaries between the molten salt and gaseous CO₂, improving the rate of adsorption of CO₂ into the sorbent. The molten salt also influences the sintering of MgO and NaNO₃, which further increased the crystallite size and surface area in the first few cycles. When applied as a sorbent in the Cu catalysed WGSR, the NaNO₃ modified MgO sorbent exhibited a CO conversion of 27% at 300 °C, while CO₂ output remained relatively high. The high CO₂ output is attributed to the loss of basic sites when the NaNO₃-MgO sorbents are mixed with the Cu catalyst, which lowers the retention of CO₂ at 300 °C, and impedes the effect of NaNO₃ in capturing CO₂ in the WGSR.

The CO₂ methanation has received attention as a reaction converting CO₂ into a useful resource such as methane (PtG technology). When assuming that methanation is used as a reaction to process CO₂ emitted from an industrial process, the presence of oxygen may have a negative influence, such as an oxidation of the active site. In this study, to examine the influence of O₂ on the catalytic function, the methanation performance of a Ni/CeO₂ catalyst was evaluated using a raw material gas containing oxygen of 1–10 vol%. As a result, the methanation activity at a lower temperature was greatly improved, and the ability to produce a high methanation performance was realized even in a region at room temperature. We found a novel route of CO₂ methanation that can be driven with no heating, even in ambient, which we named as auto-methanation. No one in the World has reported such transformation route yet.
A granular Ni/CeO₂ catalyst was prepared using evaporation to dryness of Ni(NO₃)₂·6H₂O on CeO₂ support. The CO₂ methanation was investigated using conventional flow-type reactor by introducing feed-gas at setting temperature of 350 °C down to room-temperature. The raw gas contained CO₂, H₂, O₂, N₂. The CO₂ concentration was fixed at 10 vol% with 400 ml/min.
Figures 1(a) and 1(b) show CO₂ conversion and product-selectivity. When supplying oxygen of 1 vol% and 3 vol%, the drastic change in conversion shifted to the lower side, which was near room temperature. At oxygen of 5 vol% and 7 vol%, about 65 and 70% conversions were obtained even at room temperature without external heating. Methane selectivity was almost 100% at lower temperature. Figure 1(c) is snapshot of the auto-methanation state. A combination of methanation and combustion might offer a novel CO₂ transformation technique, which will open a new process.