Materials Science Forum Vol. 965

Abstract: The present work assesses water and power consumption, ethanol production and CO₂ emissions in order to evaluate the technical and economic feasibility of a high-scale sugarcane-based biorefinery and propose a scenario of full carbon and capture system, so the complex could become a sustainable carbon withdrawer from the atmosphere. This work is performed with the aid of professional software for a rigorous mass and energy balances simulation to achieve process data for plant technical and economic analysis. The combustion of sugarcane bagasse is the only source of energy of the plant, which provides steam for the distillery and generates electricity through cogeneration system. The ethanol production from sugars fermentation produces CO₂ which, jointly with the CO₂ from combustion, is released directly into the atmosphere contributing to global warming. Results demonstrate that for processing capacity of 1,000 t/h of sugarcane, the plant emits 0.7 tCO₂ per ton of sugarcane, with net water consumption of 3,600 m³/h as make-up water to replace blowdown and evaporation losses in the cooling tower. The cogeneration system generates 320MW of net power for exportation as electricity. The economic analysis reveals a fixed capital investment of 910MMUSD and a net present value of 378MMUSD considering as revenues the ethanol produced and the electricity from cogeneration at an annual discount rate of 10%.

Abstract: The oil and gas industry represents an important contributor to CO₂ emissions as offshore platforms are power intensive for producing, processing and transporting hydrocarbons. In offshore rigs CO₂ emissions mainly come from on-site gas-fired power generation for heat and electricity production. The accumulation of atmospheric CO₂ is one of the main causes of the planetary greenhouse effect, thus CO₂ emissions should be minimized. To achieve that, more energy efficient processes for natural gas (NG) conditioning are needed in order to minimize platform power consumption and thus lowering the associated generation of CO₂. In addition, in offshore scenarios gas-hydrate obstructions are a major concern in flow assurance strategies, since thermodynamic conditions favoring hydrate formation are present, such as high pressure, low external temperature and gas contact with free water. To avoid hydrate issues, hydrate inhibition is carried out by the injection of a thermodynamic hydrate inhibitor (THI) in well-heads such that it flows along with production fluids, thus removing the thermodynamic conditions for hydrate formation and ensuring unimpeded flow. Therefore, the three-phase high-pressure separator (HPS) is fed with production fluids, where the HPS splits the feed into: (i) an upper gas phase, (ii) hydrocarbon condensate, and (iii) a bottom aqueous phase. The gas phase goes to NG conditioning for hydrocarbon dew point adjustment (HCDPA) and water dew point adjustment (WDPA) so as to make NG exportable. The hydrocarbon condensate (if present) is collected for stabilization and the bottom aqueous phase consisting of water, salts and THI is sent to a THI recovery unit (THI-RU) for THI re-concentration and reinjection. In conventional plants, WDPA and HCDPA are done by glycol absorption and Joule-Thomson expansion respectively. Moreover, the HPS gas carries some THI such as methanol that is lost in the processing. This work analyses a new process – SS-THI-Recovery – where HPS gas feeds a supersonic separator (SS) with injected water and compares it to the conventional processing. As a result, SS ejects a cold two-phase condensate with almost all water, THI and C3+ hydrocarbons, discharging exportable NG with enough HCDPA and WDPA grades, while the condensate gives aqueous THI returned to the THI-RU and LPG with high commercial value. Thus, SS-THI-Recovery not only avoids THI losses as well as exports NG and LPG. Both conventional gas plant and SS-THI-Recovery alternative coupled to THI-RU were simulated in HYSYS 8.8 for a given NG field and targeting the same product specifications. SS-THI-Recovery presented lower power consumption and thus less associated CO₂ emissions, while potentially increasing the gas plant profitability, as THI losses are significantly reduced and higher flow rate of LPG with higher commercial value is produced in comparison with the conventional alternative. Hence, the higher efficiency of SS-THI-recovery makes it not only more environmentally friendly with lower CO₂ emissions, but also a potential alternative for improving process economics and thus providing an economic leverage that could justify investments in carbon capture technologies, contributing to avoid CO₂ emissions even more with cleaner NG and LPG production.

Abstract: Some carbonate reservoirs are known for their high CO₂ content in oil. One possibility to handle this gas without environmental problems is to reinject it into the reservoir. Injection of carbonated water has been drawing attention because it is an advantageous technique when compared to gaseous CO₂ injection, due to its improvement in mobility in the reservoir. The objective of this study is to evaluate the phenomenon of dissolution and precipitation during carbonated water injection in carbonate rocks. These effects are identified by analyzing the porosity variations through X-ray computer tomography images and permeability profile, determined indirectly by pressure transducers that measured the differential pressure by the fluid at the inlet and outlet of the core holders. The Coreflooding test were carried out with two core holders in series to represent a near region at the reservoir by the injection of brine saturated with 25% of CO₂ in reservoir samples, composed of dolomite, calcite and clay. The test were performed using the following reservoir conditions of 8,500 psi at 70°C. Based on the experimental data provided by CT images, it can be seen that the core porosity increases or decrease during carbonated water injection due to coexistence of dissolution (increase of porosity) and precipitation (decrease of porosity) along the samples. These phenomena are observed in regions with high heterogeneity in porosity. In addition, the mineralogy of the cores is composed by three minerals, which influence in the capacity of reaction with carbonated water. For the experiment, the core placed in the core holder one presented a porosity increase and the second one decreased. On the other hand, the permeability showed a significant increase for both cores, it is believed that, the injection promoted a preferential way flow (wormhole) that affected considerably the permeability of the rock. The novelty of the investigation is that the experiments were carried out using Brazilian pre-salt carbonate reservoir rocks with mineralogy composed basically by dolomite, calcite and clay. Also, experimental work was performed at reservoir operational conditions.

Abstract: Chemical conversion of carbon dioxide (CO₂) to methanol has the potential to address two relevant sustainability issues: economically feasible replacement of fossil raw materials and avoidance of greenhouse gas emissions. However, chemical stability of CO₂ is a challenging impediment to conversion, requiring harsh reaction conditions at the expense of increased energy input, adding capital, operational and environmental costs. This work evaluates two innovative chemical conversion of CO₂ to methanol: the indirect conversion, which uses synthesis gas produced by bi-reforming as intermediate, and the direct conversion, via hydrogenation. Process simulations are used to obtain mass and energy balances, needed to support economic analyses. Due to the uncertainties in the raw material prices, including CO₂ and hydrogen (H₂), its limits for economic viability are estimated and sensitivity analyzes are carried in predetermined prices (base cases). It is considered the scenario of free CO₂ available in atmospheric conditions, as in a bioethanol industry, but the sensitivity analyses show the results for other scenarios, as in a CO₂ rich natural gas, in which the cost of processing CO₂ is zero. The economic analyses show that hydrogenation can be feasible if hydrogen prices are lower than 1000 US$/t, while the indirect route is viable only for cheap sources of natural gas below 3.7 US$/MMBtu. The CO₂ pre-treatment costs are not as sensible as the others raw materials.

Abstract: Membrane separation technology has been recently attracted more attention as an option for gas separations due to its compact system, ease of operation and low power consumption. In this study, polymer membranes with different percentages of polyurethane were synthesized and submitted to permeability and selectivity tests for the following gases, CO₂, N₂, O₂ and CH₄, at two pressures of 4 and 8 bar and at room temperature. The membranes were characterized by FTIR-ATR, Scanning electron microscope (SEM), Thermogravimetric analysis (TGA) and X-ray diffractometer (XRD). At low pressure of 4 bar and room temperature, the membrane with low percentage of PU, 10 %, presented the higher selectivity to CO₂ in relation to both N₂ and CH₄. The same behavior was observed at a high pressure of 8 bar, with higher selectivity to CO₂ in relation to all studied gases, N₂, O₂ and CH₄, compared to the already analogous reported membranes submitted at greater pressures.

Abstract: Two types of polymeric coating were applied on an AISI 1020 steel, where one of them was reinforced by carbon nanotubes, with the objective of protection against corrosion in a medium containing saline solution, NaCl 3% wt satured with CO₂, at 75 bar and tested at 50oC and 75oC for 360 hours. Electrochemical techniques, such as Linear Polarization Resistance, (LPR), Electrochemical Impedance Spectroscopy (EIS), Tafel curves and weight loss method, were used for coating evaluation performance. Scanning Electron Microscopy (SEM), X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS) were used to determine both the morphology and chemical composition of the layer formed on the analyzed surfaces. The coating adhesion to metallic surface was evaluated using pull-off test according to ASTM D4541-09. For the studied conditions, the results obtained showed that there was no adequate coating protection, occurring failures and indicating that both coatings may not be used in the tested conditions.