Gas-based Processes Research Articles

The dual role of low-carbon ammonia in climate-smart farming and energy transition

The changing climate poses unprecedented risks and challenges to agricultural production and energy systems worldwide, necessitating innovative technology and policy solutions that transcend traditional boundaries. This paper highlights the critical intersection of energy and agricultural systems and identifies low-carbon intensity ammonia (LCIA) as a pivotal element in reducing the carbon footprint of US agricultural production, particularly in fertilizer use. It presents a comprehensive analysis of the ammonia market and value chain, emphasizing its potential to decarbonize agricultural fertilizers and serve as an alternative clean energy source. The technical review covers various ammonia production methods, from natural gas-based processes with carbon capture and storage to electrolysis using renewable energy. These methods’ economic and environmental implications are examined to provide insights into the levelized costs and emissions of LCIA applications across various scenarios. A case study focusing on the Permian Basin and Southern High Plains regions is conducted to illustrate the regional synergy between the agriculture and energy sectors, proposing a framework for integrating LCIA into the US agricultural sector. The proposed framework, Sustainable Ammonia for Resilient Agriculture, outlines policy recommendations and strategic investments to overcome market and infrastructure barriers, aiming to develop a resillient and sustainable LCIA value chain. Future research direction should emphasize the need for local value chain development plans encompassing agriculture, energy, infrastructure, and workforce development under a unified policy framework.

Seeing the nanoscale dynamics in gas-based processes by using in-situ TEM

Seeing the nanoscale dynamics in gas-based processes by using in-situ TEM

Modeling and simulation of the use of direct reduced iron in a blast furnace to reduce carbon dioxide emissions

The reduction of greenhouse gas emissions in all economic sectors is an important goal of the transition towards a sustainable energy system. The steel industry is one of the largest industrial CO2 emitters and roughly two-thirds of the annual steel production can be attributed to the conventional blast furnace/converter route. In this study, the potential to reduce CO2 emissions from blast furnace processes by using direct reduced iron (DRI) as a pre-reduced input material is examined. An existing blast furnace model constructed using Aspen Plus in combination with FactSage/ChemApp is applied. Different types of DRI produced by gas-based processes (i.e., the Midrex and Energiron process) are considered. These are assumed to be produced partially using pure hydrogen as a reducing gas, which is generated renewably by water electrolysis. The simulation results show that the CO2 emissions can decrease significantly with the measure implemented. At the most favorable operation conditions using 400 kg/tHM of DRI (tHM = ton of produced hot metal), the CO2 emissions of the blast furnace can be reduced by up to 26.7% relative to typical operations using pulverized coal at an injection rate of 120 kg/tHM.

Is It Greener? Impact of Cathode Catalyst Performance on Life-Cycle Emissions of Producing Methanol By Electrocatalytic CO2 Reduction

Direct electrocatalytic reduction of carbon dioxide (deCO2rr) is being developed as a route to energy-dense liquid transportation fuels for a low-emissions future. This technology would reduce net emissions from fuel combustion, because these would be fully offset by upstream capture of the CO2 used to produce the fuel. However, it would produce some additional emissions from related processes, such as generating the process electricity and purifying the product stream. Although extensive basic-science catalysis research is underway in this area, the full life-cycle emissions of this technology platform have not been quantified.In this prospective technology analysis, we apply systematic life cycle assessment (LCA) to estimate the total life cycle emissions associated with producing methanol from low-temperature electrocatalytic reduction of CO2. This analysis framework (1) quantifies the emissions impact of using deCO2rr to provide drop-in liquid hydrocarbon fuels, and (2) provides catalyst performance targets (faradic efficiency, overpotential, and yield) for this technology to provide net emissions reductions. The framework provides a long-term emissions impact perspective to guide priorities in catalysis research for sustainability.The hypothetical reference case deCO2rr system in this analysis features a cathode electrocatalyst that reduces CO2 to methanol with 15% faradaic efficiency, 0.8 V overpotential, and 25% conversion of CO2 to product. Water is oxidized at the anode. The methanol production system is coupled to CO2 capture from a coal-fired power plant. In a preliminary analysis of this integrated methanol-electricity system, the products (1 g MeOH plus 6.1 Wh of electricity) have a total emissions intensity of 3.8 g CO2. This is approximately half the emissions produced when using conventional processes to produce the same electricity (without carbon capture) and methanol (using a natural gas-based process). In addition, we quantify the emissions impact of improving the performance of the CO2 reduction catalyst from present values. We identify technology performance thresholds for this renewable methanol process to provide a net emissions reduction compared to conventional processes. For instance, we estimate that using present-day CO2 capture technology, the integrated electricity-methanol production system would provide a net reduction in emissions if the cathode catalyst has 20% faradaic efficiency and 20% molar conversion of CO2 to methanol.

Plasma effects in semiconducting nanowire growth

Three case studies are presented to show low-temperature plasma-specific effects in the solution of (i) effective control of nucleation and growth; (ii) environmental friendliness; and (iii) energy efficiency critical issues in semiconducting nanowire growth. The first case (related to (i) and (iii)) shows that in catalytic growth of Si nanowires, plasma-specific effects lead to a substantial increase in growth rates, decrease of the minimum nanowire thickness, and much faster nanowire nucleation at the same growth temperatures. For nucleation and growth of nanowires of the same thickness, much lower temperatures are required. In the second example (related to (ii)), we produce Si nanowire networks with controllable nanowire thickness, length, and area density without any catalyst or external supply of Si building material. This case is an environmentally-friendly alternative to the commonly used Si microfabrication based on a highly-toxic silane precursor gas. The third example is related to (iii) and demonstrates that ZnO nanowires can be synthesized in plasma-enhanced CVD at significantly lower process temperatures than in similar neutral gas-based processes and without compromising structural quality and performance of the nanowires. Our results are relevant to the development of next-generation nanoelectronic, optoelectronic, energy conversion and sensing devices based on semiconducting nanowires.

A Gas-assisted Gravity Drainage Process in Naturally Fractured Reservoirs

Water alternating gas injection or simultaneous water and gas injection have been proposed as a good candidate to minimize gravity segregation and provide more efficient enhanced oil recovery performance in comparison to conventional continuous gas injection. However, water alternating gas-based processes can cause some difficulties with an increase in water saturation (e.g., water shielding) including diminished gas injectivity (Rao et al., 2004). As an effective alternative for water alternating gas injection, gas-assisted gravity drainage was developed for conventional reservoirs (U.S. Patent 2006/0289157) that takes advantage of the natural segregation of gas from liquid hydrocarbon during injection. The gas-assisted gravity drainage process consists of placing a horizontal well near the bottom of an oil column and injecting gas through existing vertical wells. Gravity segregation of injected gas will cause liquid hydrocarbon and water to drain down to the aforementioned horizontal well. Application of gas-assisted gravity drainage for enhanced oil recovery in a naturally fractured reservoir is evaluated in this article based on some facts and figures.

The “good health” of the iron and steel industry economy of the Arab world

The Arab world has been less affected by the financial crisis of 2008–2009 than many other regions of the world. As an illustration, the apparent steel consumption has been growing to a level of 40 to 45 Mt/year, like in China or India but not so fast. The steel production is also growing, but is still in the range of 15 to 17 Mt/year: the region is a large steel importer, around 30 Mt/year. It is interesting to note that this trade is, essentially, between the two sides of the Mediterranean Sea. Regarding the production, it must be remembered that this area has the special feature of being based on the direct reduction of the iron ores through the natural gas-based processes such as Midrex** or Energiron (ex – HYL). Steelmaking is carried out in EAF (electric arc furnaces) and it must be noted that, in the Marrakesh congress, the Turkish delegation mentioned that a new company in this country is designing and manufacturing electric arc furnaces for mini-mills based on scrap. A last point has to be stressed: the diversification of the steel products made in the Arab world. After a time where the emphasis was on light long products (reinforcing bars and light profiles), the production is now moving to heavy products such as beams and tubes, and flat products.

Plasma-driven self-organization of Ni nanodot arrays on Si(100)

The results of the combined experimental and numerical study suggest that nonequilibrium plasma-driven self-organization leads to better size and positional uniformity of nickel nanodot arrays on a Si(100) surface compared with neutral gas-based processes under similar conditions. This phenomenon is explained by introducing the absorption zone patterns, whose areas relative to the small nanodot sizes become larger when the surface is charged. Our results suggest that strongly nonequilibrium and higher-complexity plasma systems can be used to improve ordering and size uniformity in nanodot arrays of various materials, a common and seemingly irresolvable problem in self-organized systems of small nanoparticles.

Droplet cooling in atomization sprays

Transport between droplets/particles and a gas phase plays an important role in numerous material processing operations. These include rapid solidification operations such as gas atomization and spray forming, as well as chemical systems such as flash furnaces. Chemical reaction rates and solidification are dependent on the rate of gas-particle or gas-droplet transport mechanisms. These gas-based processes are difficult to analyze due to their complexity which include particle and droplet distribution and the flow in a gas field having variations in temperature and velocity both in the jet cross-section and in the axial distance away from the jet source. Thus to study and properly identify the important variables in transport, these gas and droplet variations must be eliminated or controlled. This is done in this work using models based on a single fluid atomization system. Using a heat transport model (referred to as thermal model) validated using single fluid atomization of molten droplets and a microsegregation model, the effect of process variables on heat losses from droplets was examined. In this work, the effect of type of gas, droplet size, gas temperature, gas-droplet relative velocity on the heat transport from AA6061 droplets was examined. It is shown that for a given gas type, the most critical process variable is the gas temperature particularly as affected by two-way thermal coupling and the droplet size. The results are generalized and applied to explain the difference in droplet cooling rate from different atomization processes.

Carbon saturation of arrays of Ni catalyst nanoparticles of different size and patternuniformity on a silicon substrate

The kinetics of saturation of Ni catalyst nanoparticle patterns of the three different degreesof order, used as a model for the growth of carbon nanotips on Si, is investigatednumerically using a complex model that involves surface diffusion and ion motionequations. It is revealed that Ni catalyst patterns of different degrees of order, with Ninanoparticle sizes up to 12.5 nm, exhibit different kinetics of saturation with carbon on theSi surface. It is shown that in the cases examined (surface coverage in the rangeof 1–50%, highly disordered Ni patterns) the relative pattern saturation factorcalculated as the ratio of average incubation times for the processes conducted in theneutral and ionized gas environments reaches 14 and 3.4 for Ni nanoparticles of 2.5and 12.5 nm, respectively. In the highly ordered Ni patterns, the relative patternsaturation factor reaches 3 for nanoparticles of 2.5 nm and 2.1 for nanoparticles of12.5 nm. Thus, more simultaneous saturation of Ni catalyst nanoparticles of sizes inthe range up to 12.5 nm, deposited on the Si substrate, can be achieved in thelow-temperature plasma environment than with the neutral gas-based process.

Fundamentals of fast reduction of ultrafine iron ore at low temperature

Fundamentals on the fast reduction of ultrafine iron ore at low temperature, including characterization of ultrafine ore, de-oxidation thermodynamics of stored-energy ultrafine ore, kinetics of iron ore deoxidation, and deoxidation mechanism, etc., and a new ironmaking process are presented in this article. Ultrafine ore concentrate with a high amount of stored energy can be produced by mechanical milling, and can be deoxidated fast below 700°C by either the coal-based or gas-based process. This novel process has some advantages over others: high productivity, low energy consumption, and environmental friendliness.

Growth kinetics of carbon nanowall-like structures in low-temperature plasmas

The results of a hybrid numerical simulation of the growth kinetics of carbon nanowall-like nanostructures in the plasma and neutral gas synthesis processes are presented. The low-temperature plasma-based process was found to have a significant advantage over the purely neutral flux deposition in providing the uniform size distribution of the nanostructures. It is shown that the nanowall width uniformity is the best (square deviations not exceeding 1.05) in high-density plasmas of 3.0×1018m−3, worsens in lower-density plasmas (up to 1.5 in 1.0×1017m−3 plasmas), and is the worst (up to 1.9) in the neutral gas-based process. This effect has been attributed to the focusing of ion fluxes by irregular electric field in the vicinity of plasma-grown nanostructures on substrate biased with −20V potential, and differences in the two-dimensional adatom diffusion fluxes in the plasma and neutral gas-based processes. The results of our numerical simulations are consistent with the available experimental reports on the effect of the plasma process parameters on the sizes and shapes of relevant nanostructures.

Nanostructures of various dimensionalities from plasma and neutral fluxes

A complex multi-scale model and numerical simulations are used to demonstrate, by simulating the development of patterns of nanotips, nanowalls, nanoislands and nanovoids of a characteristic size of 5–100 nm, a greater degree of determinism in the formation of various nanostructures by using the low-density, low-temperature plasma-based processes. It is shown that in the plasma, in contrast to the neutral gas-based processes, one can synthesize nanostructures of various dimensionalities and shapes with a larger surface density, desired geometrical parameters and narrower size distribution functions. This effect is mainly attributed to strong ion focusing by irregular electric fields in the nanopatterns, which effectively redistributes the influxes of plasma-generated building units and thus provides a selective control of their delivery to the growing nanostructures.

Surface fluxes of Si and C adatoms at initial growth stages of SiC quantum dots

Self-assembly of highly stoichiometric SiC quantum dots still remains a major challenge for the gas/plasma-based nanodot synthesis. By means of a multiscale hybrid numerical simulation of the initial stage (0.1–2.5 s into the process) of deposition of SiC∕Si(100)quantum dot nuclei, it is shown that equal Si and kst atom deposition fluxes result in strong nonstoichiometric nanodot composition due to very different surface fluxes of Si and C adatoms to the quantum dots. At this stage, the surface fluxes of Si and C adatoms to SiC nanodots can be effectively controlled by manipulating the Si∕C atom influx ratio and the Si(100)surface temperature. It is demonstrated that at a surface temperature of 800 K the surface fluxes can be equalized after only 0.05 s into the process; however, it takes more then 1 s at a surface temperature of 600 K. Based on the results of this study, effective strategies to maintain a stoichiometric ([Si]∕[C]=1:1) elemental ratio during the initial stages of deposition of SiC∕Si(100) quantum dot nuclei in a neutral/ionized gas-based process are proposed.

The sequestering of carbon dioxide, embodied energy and common targets for the mitigation of greenhouse gas emissions

Abstract A simple three-level spreadsheet has been extended to assess the emissions of carbon dioxide from pairs of countries cooperating in Common Targets and Activities Implemented Jointly. Using this methodology, actual data for 1995 may be compared conveniently with projected data for cooperative projects in the same year to illustrate both the changes in emissions of this greenhouse gas and in the consumption of primary energy. The technique was applied to a major energy-intensive industry of importance in international trade—steelmaking—in a scenario involving the production of ten million additional tonnes per year in each of Australia, Brazil, and Canada in cooperation with Japan, the largest steelmaker in 1995. If carbon dioxide can be captured and sequestered in each of the primary production countries, a major expansion of the industry is possible through the use of pooled sequestering facilities. The direct reduction of iron ore in natural gas-based processes has significant advantages when emissions of this gas must be controlled.

Gas‐based direct reduction processes for iron and steel production

Gas-based processes for the direct reduction of iron are discussed and compared in terms of their costs and energy effectiveness. Possible future lines of development are presented.