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Abstract The mass transfer performance of the absorption of CO2 in aqueous blended MDEA-MEA solutions was evaluated experimentally in a lab-scale absorber packed with high efficiency DX structured packing over MDEA-MEA concentrations of 27/3, 25/5, and 23/7%wt under atmospheric pressure using a premixed feed gas containing 15% CO2 balanced with N2. The absorption performance was presented in terms of overall mass transfer coefficient ( K G a v ) and CO2 concentration profile. The results showed that the mass transfer performance increased as ratio of MEA in the blended solution, temperature, and liquid flow rate increased but decreased as CO2 loading increased. In addition, it was found that the cyclic capacity and relative solvent regeneration ability decreased as the ratio of MEA in the blended solution increased. Based on mass transfer performance, cyclic capacity, and relative solvent regeneration ability, 23/7%wt MDEA-MEA was found to be the most effective blend ratio among the three ratios investigated in the present work. Also, the correlation for predicting K G a v for CO2 absorption into aqueous blended MDEA-MEA was successfully developed with an AAD of 21.8%.

The CO2CRC Otway Project in southwestern Victoria, Australia has injected over 17 months 65,445 tonnes of a mixed CO2-CH4 fluid into the water leg of a depleted natural gas reservoir at a depth of ∼2km. Pressurized sub-surface fluids were collected from the Naylor-1 observation well using a tri-level U-tube sampling system located near the crest of the fault-bounded anticlinal trap, 300m up-dip of the CRC-1 gas injection well. Relative to the pre-injection gas-water contact (GWC), only the shallowest U-tube initially accessed the residual methane gas cap. The pre-injection gas cap at Naylor-1 contains CO2 at 1.5mol% compared to 75.4mol% for the injected gas from the Buttress-1 supply well and its CO2 is depleted in 13C by 4.5‰ VPDB compared to the injected supercritical CO2. Additional assurance of the arrival of injected gas at the observation well is provided by the use of the added tracer compounds, CD4, Kr and SF6 in the injected gas stream. The initial breakthrough of the migrating dissolved CO2 front occurs between 100 and 121 days after CO2 injection began, as evidenced by positive responses of both the natural and artificial tracers at the middle U-tube, located an average 2.3m below the pre-injection GWC. The major CO2 increase to ∼60mol% and transition from sampling formation water with dissolved gas to sampling free gas occurred several weeks after the initial breakthrough. After another ∼3 months the CO2 content in the lowest U-tube, a further average 4.5m deeper, increased to ∼60mol%, similarly accompanied by a transition to sampling predominantly gases. Around this time, the CO2 content of the upper U-tube, located in the gas cap and an average 10.4m above the pre-injection GWC, increased to ∼20mol%. Subsequently, the CO2 content in the upper U-tube approaches 30mol% while the lower two U-tubes show a gradual decrease in CO2 to ∼48mol%, resulting from mixing of injected and indigenous fluids and partitioning between dissolved and free gas phases. Lessons learnt from the CO2CRC Otway Project have enabled us to better anticipate the challenges for rapid deployment of carbon storage in a commercial environment at much larger scales.

Abstract Particles deposition and plug-in wellbore cause lots of damage and efficiency reduction during oil and gas exploitation. Transportation has been a focus for safety and production improvement. The annular flow field and particles transport behavior have been investigated using computational fluid dynamics with an renormalization group k–ɛ method. Effects of particles volume concentration, washing fluid concentration with power-law shearing, annular eccentricity, flow rate, and rotation speed have been researched to get the mechanism of particles accumulation and transport behavior. The results show that an increase in eccentricity causes velocity reduction of the annular narrow gap area, particles easily deposit, accumulate, and are hard to transport; increasing flow rate and fluid concentration apparently improve particles transportation and reduce deposition, pressure loss increases; inlet particles volume concentration increases deposition starting position and deposition length, the inner pipe rotation facilitates particles’ second suspension.

Abstract This study used ProMax® 4.0 process simulator (rate–based model) to conduct a parametric sensitivity of carbon dioxide (CO2) capture from a 115 MW coal–fired power plant (Boundary Dam 3 power plant) using monoethanolamine (MEA) and diethanolamine (DEA) blend. Saskatchewan Power Corporation (SaskPower), Canada provided the flue gas composition used in this study. The validated simulation was used to determine the effects of some process variables (independent process variables) on different dependent process variables. The independent process variables are flue gas temperature (TFG, oC), lean amine temperature (TLA, oC), lean amine flow rate (FLA, tonne/day), lean amine concentration difference (CMEA–DEA, kmol/m3) and reboiler temperature (TREB, oC). The dependent process variables are MEA and DEA vaporization from the absorber, CO2 absorption efficiency (%), regeneration energy (GJ/tonne CO2), rich amine loading (RAL, mol CO2/mol amine) and lean amine loading (LAL, mol CO2/mol amine). Amine degradation was investigated by the O2 absorption rate (tonne O2/day), NO absorption rate (tonne NO/day) and NO2 absorption rate (tonne NO2/day). The vaporization rates of MEA (tonne MEA/day) and DEA (tonne DEA/day) were also investigated. The contribution of amine and water make–up costs, regeneration energy, pump electrical energy, blower electrical energy and compressor electrical energy towards variable operating expenditure (V–OPEX) were also investigated. Results showed that NO also contributes to amine degradation. From the parametric analysis it was observed that TREB has the greatest influence on most of the dependent process variables. It was also discovered that the regeneration energy, compressor electrical energy and amine, water make–up cost and cooling water contributed 82.5%, 12.3%, 1.1%, 0.9% and 0.5% of the V–OPEX respectively.

Abstract Implementation of a lignin-based biorefinery into one of the existing kraft pulp mills calls for increased consumption of resources such as steam (by up to 21.5%), water (by up to 3%), carbon dioxide (by up to 16.2%), and sulphuric acid (by up to 11.3%). To compensate for these extra demands on resources, an advanced process integration method was used to identify steam, water, and chemicals savings options and resource recovery opportunities within the kraft process. Given the importance of the lignin-based biorefinery, an economic viability assessment was carried out toward four scenarios, namely: a reference case relating to a stand-alone kraft pulp mill without a pulp production increase but with/without advanced process integration (scenarios #1 and #2) as well as to an integrated biorefinery with a pulp production increase by 5, 10 and 15% (scenarios #3 and #4).

CO2 separation plays an important role in energy saving and CO2 emission reduction to address global warming. Ionic liquids (ILs) have been proposed as potential absorbents for CO2 separation, and ...

Abstract Two sets of experiments on typical Class G well cement were carried out in the laboratory to understand better the potential processes involved in well leakage in the presence of CO2. In the first set, good-quality cement samples of permeability in the order of 0.1 μD (10−19 m2) were subjected to 90 days of flow through with CO2-saturated brine at conditions of pressure, temperature and water salinity characteristic of a typical geological sequestration zone. Cement permeability dropped rapidly at the beginning of the experiment and remained almost constant thereafter, most likely mainly as a result of CO2 exsolution from the saturated brine due to the pressure drop along the flow path which led to multi-phase flow, relative-permeability effects and the observed reduction in permeability. These processes are identical to those which would occur in the field as well if the cement sheath in the wellbore annulus is of good quality. The second set of experiments, carried out also at in situ conditions and using ethane rather than CO2 to eliminate any possible geochemical effects, assessed the effect of annular spaces between wellbore casing and cement, and of radial cracks in cement on the effective permeability of the casing-cement assemblage. The results show that, if both the cement and the bond are of good quality, the effective permeability of the assemblage is extremely low (in the order of 1 nD, or 10−21 m2). The presence of an annular gap and/or cracks in the order of 0.01–0.3 mm in aperture leads to a significant increase in effective permeability, which reaches values in the range of 0.1–1 mD (10−15 m2). The results of both sets of experiments suggest that good cement and good bonding with casing and the surrounding rock will likely constitute a good and reliable barrier to the upward flow of CO2 and/or CO2-saturated brine. The presence of mechanical defects such as gaps in bonding between the casing or the formation, or cracks in the cement annulus itself, leads to flow paths with significant effective permeability. This indicates that the external and internal interfaces of cements in wells would most probably constitute the main flow pathways for fluids leakage in wellbores, including both gaseous/supercritical phase CO2 and CO2-saturated brine.

Abstract The innovative concept of a zero-waste, energy efficient, and therefore sustainable desalination strategy, Zero Thermal Input Membrane Distillation (ZTIMD), is demonstrated to be economically more effective than existing seawater desalination technologies by simulation based on a single-pass Direct Contact Membrane Distillation process using surface seawater as the feed and bottom seawater as the coolant. Thermal energy required for water distillation in the process was satisfied by extracting the enthalpy of the surface seawater using the bottom seawater as the heat sink. Under one of the favorable conditions, the proposed ZTIMD process could produce pure water with a cost of $0.28/m3 at a specific energy consumption of 0.45 kW h/m3, which is significantly lower than that of the major existing seawater desalination processes, including the currently dominating technology, Reverse Osmosis ($0.45–2.00/m3). Some major advantages promised by the ZTIMD include (1) With no requirement of external thermal energy input, ZTIMD is an inherently energy-saving process, (2) it is economically competitive to existing desalination technologies, and (3) it is waste-free.