Detailed investigations of the influence of catalyst packing porosity on the performance of THAI-CAPRI process for in situ catalytic upgrading of heavy oil and bitumen

Heavy oils and bitumen are indispensable resources for a turbulent-free transition to a decarbonized global energy and economic system. This is because according to the analysis of the International Energy Agency’s 2020 estimates, the world requires up to 770 billion barrels of oil from now to year 2040. However, BP’s 2020 statistical review of world energy has shown that the global total reserves of the cheap-to-produce conventional oil are roughly only 520.2 billion barrels. This implies that the huge reserves of the practically unexploited difficult-and-costly-to-upgrade-and-produce heavy oils and bitumen must be immediately developed using advanced upgrading and extraction technologies which have greener credentials. Furthermore, in accordance with climate change mitigation strategies and to efficiently develop the heavy oils and bitumen resources, producers would like to maximize their upgrading within the reservoirs by using energy-efficient and environmentally friendly technologies such as the yet-to-be-fully-understood THAI-CAPRI process. The THAI-CAPRI process uses in situ combustion and in situ catalytic reactions to produce high-quality oil from heavy oils and bitumen reservoirs. However, prolonging catalyst life and effectiveness and maximizing catalytic reactions are a major challenge in the THAI-CAPRI process. Therefore, in this work, the first ever-detailed investigations of the effects of alumina-supported cobalt oxide–molybdenum oxide (CoMo/γ-Al2O3) catalyst packing porosity on the performance of the THAI-CAPRI process are performed through numerical simulations using CMG STARS. The key findings in this study include: the larger the catalyst packing porosity, the higher the accessible surface area for the mobilized oil to reach the inner coke-uncoated catalysts and thus the higher the API gravity and quality of the produced oil, which clearly indicated that sulphur and nitrogen heteroatoms were catalytically removed and replaced with hydrogen. Over the 290 min of combustion period, slightly more oil (i.e. an additional 0.43% oil originally in place (OOIP)) is recovered in the model which has the higher catalyst packing porosity. In other words, there is a cumulative oil production of 2330 cm3 when the catalyst packing porosity is 56% versus a cumulative oil production of 2300 cm3 in the model whose catalyst packing porosity is 45%. The larger the catalyst packing porosity, the lower the mass and thus cost of the catalyst required per m3 of annular space around the horizontal producer well. The peak temperature and the very small amount of produced oxygen are only marginally affected by the catalyst packing porosity, thereby implying that the extents of the combustion and thermal cracking reactions are respectively the same in both models. Thus, the higher upgrading achieved in the model whose catalyst packing porosity is 56% is purely due to the fact that the extent of the catalytic reactions in the model is larger than those in the model whose catalyst packing porosity is 45%.

The results of a 24-month controlled, prospective study of relapsing multiple sclerosis patients at risk for progressive multifocal encephalopathy, who switched from prolonged use of natalizumab to teriflunomide

Background Natalizumab (NTZ) is a highly effective disease modifying treatment for relapsing multiple sclerosis (RMS), but it increases risk of progressive multifocal leukoencephalopathy (PML) in patients with serum anti- John Cunningham virus (JCV) antibodies. Objective To assess the safety and efficacy of rapid transition, from NTZ to teriflunomide (TFM) in RMS patients. Methods Clinically stable NTZ-treated, anti-JCV antibody positive RMS patients were switched to TFM 28 ± 7 days after their last dose of NTZ. The primary endpoint was proportion of relapse free patients at 24 months. Results Median [IQR] age of the 55 enrolled patients was 47 [40.7, 56.3] years, 76% were female. The median [IQR] number of prior NTZ treatments was 34 [18, 64]. annualized relapse rate (ARR) was 0.07 and 77% of the patients were relapse free at 24 months. Mean time to first GAD + lesion was 19.6 months, and to new/enlarging T2 lesion was 19.2 months. Mean time to 3 month sustained disability worsening (SDW) was 22 months and proportion free of 3-month SDW was 0.87. There were no cases of PML. Conclusions The washout-free transition of NTZ to TFM was an efficacious and safe strategy for patients at risk of developing PML. ClinicalTrials.gov Identifier: NCT01970410

Active, Reactive, and Apparent Power in Dielectrophoresis: Force Corrections from the Capacitive Charging Work on Suspensions Described by Maxwell-Wagner’s Mixing Equation

A new expression for the dielectrophoresis (DEP) force is derived from the electrical work in a charge-cycle model that allows the field-free transition of a single object between the centers of two adjacent cubic volumes in an inhomogeneous field. The charging work for the capacities of the volumes is calculated in the absence and in the presence of the object using the external permittivity and Maxwell-Wagner’s mixing equation, respectively. The model provides additional terms for the Clausius-Mossotti factor, which vanish for the mathematical boundary transition toward zero volume fraction, but which can be interesting for narrow microfluidic systems. The comparison with the classical solution provides a new perspective on the notorious problem of electrostatic modeling of AC electrokinetic effects in lossy media and gives insight into the relationships between active, reactive, and apparent power in DEP force generation. DEP moves more highly polarizable media to locations with a higher field, making a DEP-related increase in the overall polarizability of suspensions intuitive. Calculations of the passage of single objects through a chain of cubic volumes show increased overall effective polarizability in the system for both positive and negative DEP. Therefore, it is proposed that DEP be considered a conditioned polarization mechanism, even if it is slow with respect to the field oscillation. The DEP-induced changes in permittivity and conductivity describe the increase in the overall energy dissipation in the DEP systems consistent with the law of maximum entropy production. Thermodynamics can help explain DEP accumulation of small objects below the limits of Brownian motion.

Singularity analysis and avoidance of a planar parallel mechanism with kinematic redundancy under a fixed orientation

In this paper, the singularity of a planar mechanism with kinematic redundancy is studied. First, the architecture of the mechanism and the concept schematic diagram for singularity avoidance are stated. Next, inverse kinematics model of the planar parallel mechanism with kinematic redundancy is established. For determining the unique inverse solution of the mechanism under certain initial installation configuration, a comparison analysis based on the strategy tree and the virtual prototype is performed. Then, based on the obtained Jacobian matrices and the singular condition, the workspace-singularity map and two singular configurations of the mechanism are drawn. Finally, with the obtained workspace-singularity map, a singularity-free transition layer and an aisle can be found to perform to singularity avoidance, even if the initial designed trajectory passing through the second kind of singularity. Three tasks are carried out to illustrate that the workspace boundary and singular configuration can be changed by adjusting the kinematic redundant actuated parameter.

Governance and the Executive – Legislative Relations since Nigeria’s Fourth Republic (1999 – 2019) and Beyond

The Year 2019 is very significant in the history of party politics in Nigeria. It marked a two decade of uninterrupted democratic regimes culminating in violent-free transition of political power from the defeated ruling political party, the People’s Democratic Party (PDP) to the opposition Party-All Progressive Congress (APC). The cut-throat rivalries among the political parties, as represented in the Executive and legislature, have been responsible for the political instability of the previous republics. What has been responsible for the relative calm in the political space of Nigeria? How has political elites responded to the issue of governance since the inception of Nigeria’s Fourth Republic? How can the Nigerian state build and improve on the current political climate? These and other issues are what the paper has addressed. The work relied contextually on secondary data for appropriate information germane to the work. The findings and analyses will benefit from prognosis that would be of immense value only not to Nigeria, but further implications for other African countries faced with similar political scenario.