Comparative assessment of CO2 capture technologies for carbon-intensive industrial processes

This article presents a consistent techno-economic assessment and comparison of CO₂ capture technologies for key industrial sectors (iron and steel, cement, petroleum refineries and petrochemicals). The assessment is based on an extensive literature review, covering studies from both industries and academia. Key parameters, e.g., capacity factor (91-97%), energy prices (natural gas: 8 €₂₀₀₇/GJ, coal: 2.5 €₂₀₀₇/GJ, grid electricity: 55 €/MWh), interest rate (10%), economic plant lifetime (20 years), CO₂ compression pressure (110 bar), and grid electricity CO₂ intensity (400 g/kWh), were standardized to enable a fair comparison of technologies. The analysis focuses on the changes in energy, CO₂ emissions and material flows, due to the deployment of CO₂ capture technologies. CO₂ capture technologies are categorized into short-mid term (ST/MT) and long term (LT) technologies. The findings of this study identified a large number of technologies under development, but it is too soon to identify which technologies would become dominant in the future. Moreover, a good integration of industrial plants and power plants is essential for cost-effective CO₂ capture because CO₂ capture may increase the industrial onsite electricity production significantly.For the iron and steel sector, 40-65 €/tCO₂ avoided may be achieved in the ST/MT, depending on the ironmaking process and the CO₂ capture technique. Advanced LT CO₂ capture technologies for the blast furnace based process may not offer significant advantages over conventional ones (30-55 €/tCO₂ avoided). Rather than the performance of CO₂ capture technique itself, low-cost CO₂ emissions reduction comes from good integration of CO₂ capture to the ironmaking process. Advanced smelting reduction with integrated CO₂ capture may enable lower steel production cost and lower CO₂ emissions than the blast furnace based process, i.e., negative CO₂ mitigation cost. For the cement sector, post-combustion capture appears to be the only commercial technology in the ST/MT and the costs are above 65 €/tCO₂ avoided. In the LT, a number of technologies may enable 25-55 €/tCO₂ avoided. The findings also indicate that, in some cases, partial CO₂ capture may have comparative advantages. For the refining and petrochemical sectors, oxyfuel capture was found to be more economical than others at 50-60 €/tCO₂ avoided in ST/MT and about 30 €/tCO₂ avoided in the LT. However, oxyfuel retrofit of furnaces and heaters may be more complicated than that of boilers.Crude estimates of technical potentials for global CO₂ emissions reduction for 2030 were made for the industrial processes investigated with the ST/MT technologies. They amount up to about 4 Gt/yr: 1 Gt/yr for the iron and steel sector, about 2 Gt/yr for the cement sector, and 1 Gt/yr for petroleum refineries. The actual deployment level would be much lower due to various constraints, about 0.8 Gt/yr, in a stringent emissions reduction scenario.     

Highwall Stability due to Punch Mining at Opencut Coal Mines

Conventional highwall mining extracts coal with an auger machine or a continuous miner from exposed seams at the base of opencut or strip operations. However, under poor strata and high stress conditions, highwall mining cannot be conducted due to pillar and roof failures. In such cases, punch highwall mining is more effective than the conventional highwall mining. This paper describes conventional highwall mining and punch highwall mining systems and discusses the stability of the highwall due to punch highwall mining at opencut coal mines.     

Fabrication and operation limit of lead-free PTCR ceramics using BaTiO3–(Bi1/2Na1/2)TiO3 system

The electric properties of BaTiO₃–(Bi_1/2Na_1/2)TiO₃ (BT–BNT) solid solution ceramics were studied as a lead-free PTCR (positive temperature coefficient of resistivity) thermistor material usable over 130°C. For determining the maximum switching temperature T _s, the phase diagram of BT–BNT binary system was clarified. Two semiconductorization processes and their electric properties are described. The lanthanum(La)-doped BBNT ceramics sintered in air still showed dielectric behaviors, but the niobium(Nb)-doped ones had a low resistivity at room temperature, ρ _RT, on the order of 10³ Ωcm and showed a PTC behavior. Sintering under a low O₂ atmosphere produces BT–BNT ceramics with less than 10² Ωcm compared to those prepared in air. Our current research produced the BBNT ceramics with T _s values around 210°C by increasing the (Bi_1/2Na_1/2) content in the ceramics.     

The Effect of Air Foam Inclusion on the Permeability and Absorption Properties of Light Weight Soil

Cement-treated clay with air foam, which is called Super Geo-Material (SGM), was developed to utilize dredged clay in an effective way. As SGM is mainly used at levels below the ground water table, water permeability and absorption properties of SGM will affect the durability of the material. In this research, the changes in SGM permeability and absorption as functions of the air foam fraction were investigated. First, permeability tests with triaxial apparatus and constant rate of consolidation tests were conducted on samples containing less than 10% of air foam by volume. From the results, air foam was found to be an impermeable medium in SGM. Secondly, a series of permeability tests and absorption tests were conducted for the SGM with different fractions of air foam while observing the specimen with a micro focus X-ray Computed Tomography (CT) scanner. The results showed that the permeability of SGM increased dramatically due to the appearance of interior water channels when the air foam fraction exceeded 30% by volume. The density distribution change and water absorbed zones of the specimens during absorption tests were estimated using the X-ray CT data. From these results, the air in the SGM was found to be progressively substituted with water from the surface to the inside of the specimen and the substituted zone expanded as it made its way to the specimen interior. The expansion velocity of the substituted zone was not affected by the coefficient of permeability but by the fraction of the air in the specimen.     

Methacrylate-based ionic liquid: radical polymerization/copolymerization with methyl methacrylate and evaluation of molecular weight of the obtained homopolymers

Azobisisobutyronitlite (AIBN)-induced free radical polymerization of a methacrylate-based ionic liquid monomer, 1-(2-methacryloxyethyl)-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (Met-IL) was carried out in a common organic solvent, N,N-dimethylformamide (DMF), and an ionic liquid, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMImTFSI). The molecular weight of the obtained poly(Met-IL) was evaluated by transforming it to non-ionic poly(methyl methacrylate) with hydrolysis of the imidazolium-salt-substituted pendant ester groups and methyl esterification. Radical copolymerization with methyl methacrylate (MMA) was also carried out in both DMF and EMImTFSI. Analysis of copolymer composition revealed that the reactivity of Met-IL was lower than that of MMA in both DMF and EMImTFSI solutions.     

Glare Generation Based on Wave Optics

This paper proposes a novel and general method of glare generation based on wave optics. A glare image is regarded as a result of Fraunhofer diffraction, which is equivalent to a 2D Fourier transform of the image of given apertures or obstacles. In conventional methods, the shapes of glare images are categorized according to their source apertures, such as pupils and eyelashes and their basic shapes (e.g. halos, coronas, or radial streaks) are manually generated as templates, mainly based on statistical observation. Realistic variations of these basic shapes often depend on the use of random numbers. Our proposed method computes glare images fully automatically from aperture images and can be applied universally to all kinds of apertures, including camera diaphragms. It can handle dynamic changes in the position of the aperture relative to the light source, which enables subtle movement or rotation of glare streaks. Spectra can also be simulated in the glare, since the intensity of diffraction depends on the wavelength of light. The resulting glare image is superimposed onto a given computer‐generated image containing high‐intensity light sources or reflections, aligning the center of the glare image to the high‐intensity areas. Our method is implemented as a multipass rendering software. By precomputing the dynamic glare image set and putting it into texture memory, the software runs at an interactive rate.     

Uniform carbon‐nanotube emitter for field‐emission displays

Abstract— The synthesis of carbon‐nanotube (CNT) field emitters for FEDs by thermal chemical vapor deposition (CVD) and their structural and emission characterization are described. Multi‐walled nanotubes (MWNTs) were grown on patterned metal‐base electrodes by thermal CVD, and the grown CNTs formed a network structured layer covering the surfaces of the metal electrode uniformly, which realized uniform distribution of electron emission. A technique for growing narrow MWNTs was also developed in order to reduce the driving voltage. The diameter of MWNT depends on the growth temperature, and it has changed from 40 nm at the low temperature (675°C) to 10–15 nm at the high temperature (900–1000°C). Moreover, narrower MWNTs were grown by using the metal‐base electrode covered with a thin alumina layer and a metal catalyst layer. Double‐walled nanotubes (DWNTs) were also observed among narrow MWNTs. The emission from the narrow CNTs showed a low turn‐on electric field of 1.5 V/μm at the as‐grown layer.     

Mechanisms of reduction in hole concentration in Al-doped 4H-SiC by electron irradiation

From the temperature dependence of the hole concentration in unirradiated lightly Al-doped 4H-SiC epilayers, an Al acceptor with E_V + 0.2 eV, which is an Al atom (Al_Si) at a Si sublattice site, and an unknown deep acceptor with E_V + 0.35 eV are found, where E_V is the top of the valence band. Both the densities are similar. With irradiation of 0.2 MeV electrons the Al acceptor density is reduced, while the unknown deep acceptor density is increased. Judging from the minimum electron energy required to displace a substitutional C atom (C_s) or the Al_Si, the bond between the Al_Si and its nearest neighbor C_s is broken due to the displacement of the C_s by this irradiation. Moreover, the displacement of the C_s results in the creation of a complex (Al_Si-V_C) of Al_Si and a carbon vacancy (V_C), indicating that the possible origin of the deep acceptor with E_V + 0.35 eV is Al_Si-V_C.