Combining stable carbon isotope analysis and petroleum-fingerprinting to evaluate petroleum contamination in the Yanchang oilfield located on loess plateau in China

This study evaluated petroleum contamination in the Yanchang (Shaanxi Yanchang Petroleum (Group) Co., Ltd.) oilfield, located in the loess plateau region of northern Shaanxi, China. Surface soil and sediment samples were collected from the wasteland, farmland, and riverbed in this area to assess the following parameters: total petroleum hydrocarbon (TPH), n-alkanes, polycyclic aromatic hydrocarbons (PAHs), and carbon isotope ratios (delta C-13). The results showed that TPH and PAH levels in the study area were 907-3447 mg/kg and 103.59-563.50 mu g/kg, respectively, significantly higher than the control samples (TPH 224 mg/kg, PAHs below method quantification limit, MQL). Tests using delta C-13 to detect modified TPH (2238.66 to 6639.42 mg/kg) in the wastelands adjacent to the oil wells revealed more significant contamination than tests using extraction gravimetric analysis. In addition, "chemical fingerprint" indicators, such as low to high molecular weight (LMW/HMW) hydrocarbons, carbon preference index (CPI), and pristine/phytane (Pr/Ph), further confirmed the presence of heavy petroleum contamination and weathering. This has resulted in a nutrient imbalance and unsuitable pH and moisture conditions for microbial metabolic activities. This study evaluates petroleum contamination, which can inform contamination remediation on a case by case basis

Boric Acid Cross-linked 3D Polyvinyl Alcohol Gel Beads by NaOH-Titration Method as a Suitable Biomass Immobilization Matrix

Granule-base immobilization of biomass is a potential method for a decent quality granular sludge cultivation. In this study, 3D polyvinyl alcohol (PVA) gel beads were chemically cross-linked via a simple NaOH-titration method. The PVA gel beads’ porous morphology was characterized using scanning electron microscope (SEM) and Brunauer–Emmette–Teller (BET), and their mechanical properties were evaluated by swelling rate and compressive stress tests. When cross-linking time was 10 min, high quality gel beads (P10) were synthesized, which demonstrated a homogeneous porous structure, good swelling rate, and high compressive strength. A mechanism for synthesis of the gel beads was proposed based on the results of Fourier transform infrared (FTIR) and X-ray diffractometer (XRD) analysis. Briefly, the intermolecular hydrogen bonds of PVA were firstly broken by NaOH to generate active bond of O–Na, which easily reacted with B(OH)4 − to produce the PVA-boric acid gel beads. P10 showed excellent biocompatibility for anaerobic ammonia oxidation (anammox) biomass’ immobilization. After incubation for three months, well granule-base immobilized sludge on P10 was developed in up-flow reactor. The sludge had high abundance of anammox biomass and was in balance with other functional bacteria. This work provides a simple method for the rapid preparation of 3D PVA gel beads and verifies their potential in granule-base immobilization of biomass.</p

Investigation of a refrigeration system based on combined supercritical CO2 power and transcritical CO2 refrigeration cycles by waste heat recovery of engine

The majority of the energy in the fuel burned in the internal combustion engines is lost in the form of waste heat. To address this issue, waste heat recovery technology has been proposed to increases the overall efficiency of engine. This paper investigates a heat driven cooling system based on a supercritical CO2 (S-CO2) power cycle integrated with a transcritical CO2 (T-CO2) refrigeration cycle, aiming to provide an alternative to the vapour absorption cooling system. The combined system is proposed to produce cooling for food preservation on a refrigerated truck by waste heat recovery of engine. In this system, the S-CO2 absorbs heat from the exhaust gas and the generated power in the expander is used to drive the compressors in both S-CO2 power cycle and T-CO2 refrigeration cycle. Unlike the bulky vapour absorption cooling system, both power plant and vapour compression refrigerator can be scaled down to a few kilo Watts, opening the possibility for developing small-scale waste heat driven cooling system that can be widely applied for waste heat recovery from IC engines of truck, ship and trains.A new layout sharing a common cooler is also studied. The results suggest that the concept of S-CO2/T-CO2 combined cycle sharing a common cooler has comparable performance and it is thermodynamically feasible. The heat contained in exhaust gas is sufficient for the S-CO2/T-CO2 combined system to provide enough cooling for refrigerated truck cabinet whose surface area is more than 105 m2

Effects of experimental parameters on elemental analysis of coal by laser-induced breakdown spectroscopy

The purpose of this work is to improve the precision of the elemental analysis of coal using laser-induced breakdown spectroscopy (LIBS). The LIBS technique has the ability to allow simultaneous elemental analysis and on-line determination, so it could be used in the elemental analysis of coal. Organic components such as C, H, O, N and inorganic components such as Ca, Mg, Fe, Al, Si, Ti, Na, and K of coal have been identified. The precision of the LIBS technique depends strongly on the experimental conditions, and the choice of experimental parameters should be aimed at optimizing the repeatability of the measurements. The dependences of the relative standard deviation (RSD) of the LIBS measurements on the experimental parameters including the sample preparation parameters, lens-to-sample distance, sample operation mode, and ambient gas have been investigated. The results indicate that the precision of LIBS measurements for the coal sample can be improved by using the optimum experimental parameters

A Numerical Model of Vapour Transfer and Phase Change in Unsaturated Freezing Soils

In recent studies, vapour transfer is reported to lead to remarkable frost heave in unsaturated soils, but how to better model this process has not been answered. In order to avoid the great uncertainty caused by the phase change term of vapour-water-ice in the numerical iteration process, a new numerical model is developed based on the coupled thermal and hydrological processes. The new model avoids using the local equilibrium assumption and the hydraulic relations that accounts for liquid water flow, which provides a new way for the water-heat coupling movement problem. The model is established by using COMSOL Multiphysics, which is a multiphysics simulation software through finite element analysis. The model is evaluated by comparing simulated results with data from column freezing experiments for unsaturated coarse-grained soils. Simulated values of the total water content compare well with experimental values. The model is proved to be applicable and numerically stable for a high-speed railway subgrade involving simultaneous heat and moisture transport. An agreement can be found between the predicted and measured frost/thawed depth and soil moisture profiles, demonstrating that the model is able to simulate rapidly changing boundary conditions and nonlinear water content profiles in the soil

Nanocrystallization of Coarse Primary Phases in Al- and Mg-Based Alloys Induced by HCPEB Treatment

This paper reports on a phenomenon associated with high-current pulsed electron beam (HCPEB) treatment: surface nanocrystallization of coarse primary phase in hypereutectic Al17.5Si and quasicrystal alloys after multiple pulses of HCPEB irradiation. The HCPEB treatment induces superfast heating and diffusion of alloying elements and heterogeneous nucleation in a melting solution, followed by rapid solidification and cooling of the material surfaces. Consequently, nanostructured surface layers can be achieved easily. Nano-Si phase and nano-quasicrystal phase formation on the modified surface layer of hypereutectic Al17.5Si alloy and quasicrystal alloy (Mg37Zn60Y3) show a potential for surface nanocrystallization of materials with enhanced properties by HCPEB treatment

Influence of Constraint on J-resistance Curves for an X100 Pipe Steel

AbstractThere continues to be interest in utilization of high strength steels of X100 (Grade 690) for strain-based designed large diameter, high pressure on-shore pipelines where ground movements are of great concern. While mechanical properties requirements for yield to ultimate tensile ratio, uniform elongation and work hardening are important, fracture toughness evaluation is an integral part of the strain based design analysis. We developed test procedures for measuring J-resistance (J-R) curves using both single-edge bend (SE(B)) and single-edge tension (SE(T)) specimens with shallow and deep cracks. The test procedures and analysis are based on ASTM E1820-11 and a recommended practice for SE(T) developed by CanmetMATERIALS using MTS TestSuite software. Automation of the test procedures has allowed display and export testing parameters, raw data and results, including J-R curves during and after testing.The developed test procedures have been used to measure J-R curves at room temperature for both shallow (a/w=0.20) and deep (a/w=0.50) cracks with different SE(B) and SE(T) specimens from an X100 pipe steel. The results show that for both the shallow and deep crack cases, the J-R curves are slightly higher for SE(T) than for SE(B). SE(T) specimens with a fine EDM notch tend to produce slightly higher J-R curves than those with a fatigue precrack. The differences in J-R curves between SE(T) and SE(B) specimens are established in detailed finite element analysis and shown to be related to the constraint effect which is characterized by the Q-parameter following the J-Q theory. The results obtained in the present study provide more realistic fracture toughness data where two-parameter-based structural integrity assessment is necessary for strain-based design analysis

Petroleum contamination evaluation and bacterial community distribution in a historic oilfield located in loess plateau in China

In this study, petroleum contamination and the corresponding distribution of bacterial communities in the Yanchang oilfield, a historic oilfield in north China was evaluated. Surface soil samples and river sediment samples near the oilfield were collected and analyzed for the total petroleum hydrocarbons (TPHs), n-alkanes, polycyclic aromatic hydrocarbons (PAHs), bacterial biodiversity, and environmental factors. Petroleum fingerprinting analysis and redundancy analysis (RDA) were then conducted to evaluate the petroleum contamination and the bacterial community structure. The results of these studies showed that the petroleum contamination in the study area was high in TPHs, present at the levels in the ranges 1678-6748, 1189-2237, and 1089-1728 mg/kg in the wastelands, sediments, and farmlands, respectively. "Chemical fingerprint" indicators (e.g., carbon preference index near 1 and pristane/phytane < 10) indicate that petroleum pollution in the wasteland near the oil wells migrated to the farmlands and rivers, and deep biodegradation occurred in these places. The microbial diversity analysis identified many genus, including Stenotrophomonas, Arenimonas, Sphingomonas, Aquabacterium, Acinetobacter, Comamonas and Pseudomonas, containing many known petroleum degrading species. The RDA results indicated that moisture was the most significant factor shaping the local bacterial community, followed by the total nitrogen, total organic carbon, and total phosphorus contents, and pH. This study demonstrated an approach for providing comprehensive information to support evaluation and remediation of regional petroleum contamination