Carbon Emission Reduction via HNGLRP CC&S Technology

The paper objective is to present the successful achievement by Saudi Aramco gas operations to reduce the carbon emission at Hawyiah NGL Recovery Plant (HNGLRP) after successful operation & maintainability of the newly state of the art Carbon Capture & Sequestration (CC&S) technology. This is in line with the Kingdom of Saudi Arabia (KSA) 2030 vision to increase the resources sustainability for future growth and part of Saudi Aramco circular economy in action examples. Saudi Aramco CC&S started in June 2015 at HNGLRP with main objective to capture the carbon dioxide (CO2) from Acid Gas Removal Units (AGRUs) and then inject an annual mass of nearly 750 Kton of carbon dioxide into oil wells for sequestration and enhanced oil recovery maintainability. This is to replace the typical acid gas incineration process after AGRUs operation to reduce carbon footprint. CC&S consists of the followings: integrally geared multistage compressor, standalone dehydration system using Tri-Ethylene Glycol (TEG), CO2 vapor recovery unit (VRU), Granulated Activated Carbon (GAC) to treat water generated from compression and dehydration systems for reuse purpose, and special dense phase pump that transfers the dehydrated CO2 at supercritical phase through 85 km pipeline to replace the typical sea water injection methodology in enhancing oil recovery. CC&S has several new technologies and experiences represented by the compressor capacity, supercritical phase fluid pumping, using mechanical ejector application to maximize carbon recovery, and CO2/TEG dehydration system as non-typical dehydration system. CC&S design considered the occupational health hazards generated from the compressor operation by installing engineering enclosure with proper ventilation system to minimize the noise hazard. CC&S helped HNGLRP to reduce the overall Greenhouse Gas (GHG) emission resulted from typical CO2 incineration process (thermal oxidizing). (2) The total GHG resulted from combustion sources at HNGLRP reduced by nearly 30% since CC&S technology in operation. The fuel gas consumption to run the thermal oxidizers in AGRUs reduced by 75% and sent as sales gas instead. The Energy Intensity Index (EII) reduced by 8% since 2015, water reuse index (WRI) increased by 12%. In conclusion, the project shows significant reduction in the carbon emission, noticeable increase in the production, and considerable water reuse.

Digital contact tracing contributes little to COVID-19 outbreak containment

Digital contact tracing applications have been introduced in many countries to aid in the containment of COVID-19 outbreaks. Initially, enthusiasm was high regarding their implementation as a non-pharmaceutical intervention (NPI). Yet, no country was able to prevent larger outbreaks without falling back to harsher NPIs, and the total effect of digital contact tracing remains elusive. Based on the results of empirical studies and modeling efforts, we show that digital contact tracing apps might have prevented cases on the order of single-digit percentages up until now, at best. We show that this poor impact can be attributed to a combination of low participation rates, a non-flexible reliance on symptom-based testing, low engagement of participants, and delays between testing and test result upload. We find that contact tracing does not change the epidemic threshold and exclusively prevents more cases during the supercritical phase of an epidemic, making it unfit as a tool to prevent outbreaks. Locally clustered contact structures may increase the intervention's efficacy, but only if the number of contacts per individual is homogeneously distributed, a condition usually not found in contact networks. Our results suggest that policy makers cannot rely on digital contact tracing to contain outbreaks of COVID-19 or similar diseases.

Identification of Self-Organized Critical State on Twitter Based on the Retweets’ Time Series Analysis

There is a number of studies, in which it is established that the observed flows of microposts generated by microblogging social networks (e.g., Twitter) are characterized by avalanche-like behavior. Time series of microposts depicting such streams are the time series with a power-law distribution, with 1/f noise and long memory. Despite this, there are no studies devoted to the detection and analysis of self-organized critical state, subcritical phase, and supercritical phase. The presented paper is devoted to the detection and investigation of such critical states and phases. An algorithm is proposed that allowed to detect of critical phases and critical conditions on Twitter, based on the analysis of retweets time series corresponding to the three debates of the 2016 United States Presidential Election, as the most popular debate in the history of America, collecting 84 million live views.

Supercritical percolation on nonamenable graphs: isoperimetry, analyticity, and exponential decay of the cluster size distribution

Let G be a connected, locally finite, transitive graph, and consider Bernoulli bond percolation on G. We prove that if G is nonamenable and $$p > p_c(G)$$ p > p c ( G ) then there exists a positive constant $$c_p$$ c p such that $$\begin{aligned} \mathbf {P}_p(n \le |K| < \infty ) \le e^{-c_p n} \end{aligned}$$ P p ( n ≤ | K | < ∞ ) ≤ e - c p n for every $$n\ge 1$$ n ≥ 1 , where K is the cluster of the origin. We deduce the following two corollaries: Every infinite cluster in supercritical percolation on a transitive nonamenable graph has anchored expansion almost surely. This answers positively a question of Benjamini et al. (in: Random walks and discrete potential theory (Cortona, 1997), symposium on mathematics, XXXIX, Cambridge University Press, Cambridge, pp 56–84, 1999). For transitive nonamenable graphs, various observables including the percolation probability, the truncated susceptibility, and the truncated two-point function are analytic functions of p throughout the supercritical phase.

Optimization of a New Design of Molten Salt-to-CO2 Heat Exchanger Using Exergy Destruction Minimization

One of the ways to make cost-competitive electricity, from concentrated solar thermal energy, is increasing the thermoelectric conversion efficiency. To achieve this objective, the most promising scheme is a molten salt central receiver, coupled to a supercritical carbon dioxide cycle. A key element to be developed in this scheme is the molten salt-to-CO2 heat exchanger. This paper presents a heat exchanger design that avoids the molten salt plugging and the mechanical stress due to the high pressure of the CO2, while improving the heat transfer of the supercritical phase, due to its compactness with a high heat transfer area. This design is based on a honeycomb-like configuration, in which a thermal unit consists of a circular channel for the molten salt surrounded by six smaller trapezoidal ducts for the CO2. Further, an optimization based on the exergy destruction minimization has been accomplished, obtained the best working conditions of this heat exchanger: a temperature approach of 50 °C between both streams and a CO2 pressure drop of 2.7 bar.

High Pressure Supercritical Carbon Dioxide Separation from its Mixture with Nitrogen at Different Temperatures

Carbon dioxide (CO2) capturing from point sources is currently being proposed as a way to minimize CO2 emissions to the atmosphere. Carbon dioxide is considered one of the greenhouse gases that affects our environment. Legislations are being enforced in many countries to limit CO2 emissions to the atmosphere. Two methods are mostly used for CO2 capturing from flue gases and natural gases; the first method is absorption using amine-based solvents, while the second is membrane separation. The first method is effective for CO2 separation from gas mixtures with low CO2 concentration in the range of 10 to 20%, while the other can handle gas mixture with intermediate CO2 concentration but there is a limit on the CO2 purity. Hence, such methods cannot be used in pre-combustion and oxy fuel technologies where a more concentrated CO2 gas stream is produced. Throughout this work, a new method is introduced to separate carbon dioxide from its mixture with nitrogen (N2) at high concentrations, 90 mol.% CO2 and 10 mol.% N2 gas mixture. A customized high-pressure experimental set-up was built. Three temperature were tested: 15 °C, 25 °C and 38 °C at 150 bar. At such condition CO2 will be in the liquid and the supercritical phase respectively. The composition of the top and bottom streams where analyzed. The amount of CO2 in the top stream was the smallest at the supercritical condition. In addition, the purity of CO2 in the bottom stream was the highest at 38 °C and 150 bars, when CO2 is at the supercritical phase.

A positive to negative uniaxial thermal expansion crossover in an organic benzothienobenzothiophene structure

Compound 6,6′-([1]benzothieno[3,2-b][1]benzothiophene-2,7-diyl)bis(butan-1-ol) (BTBT-C4OH) displays a continuous type 0 first-order isosymmetric phase transition at 200 K which is accompanied by a continuous change of the thermal expansion along the b axis from positive to negative. The equivalent isotropic atomic displacement parameters for all non-hydrogen atoms as well as all the eigenvalues of the anisotropic atomic displacement tensor show discontinuous behavior at the phase transition. The eigenvalues of the translational tensor in a rigid-body description of the molecule are all discontinuous at the phase transition, but the librational eigenvalues are discontinuous only in their temperature derivative. BTBT-C4OH displays a similar type of quasi-supercritical phase transition as bis(hydroxyhexyl)[1]benzothieno[3,2-b][1]benzothiophene (BTBT-C6OH), despite the difference in molecular packing and the very large difference in thermal expansion magnitudes.