Effect of coral sand powders and seawater salinity on the impact mechanical properties of cemented coral sand

Coral sand is one kind of the important building materials in coral reef engineering practice. The use of cement as a stabilizing agent can significantly improve the mechanical properties of coral sands and is widely applied in the subbase engineering construction in coral reef islands. Cement-stabilized coral sand structures may contain high contents of fine coral particles and salinity because of the high crushability of coral sands and the existence of seawater surrounding them. In this study, the effects of coral sand powders and seawater salinity on the dynamic mechanical properties of cemented coral sand (CCS) were investigated through the split Hopkinson pressure bar (SHPB) tests and Scanning Electron Microscope (SEM) analysis. It was found that the strength (i.e., the peak stress) of CCS specimens increased firstly and then decreased with the increase of powder content. The specimens reached the maximum peak stress when 3% powder content was included. The initial improvement of CCS strength was attributed to the pore-filling effect of coral powders, namely, the micro pores of the CCS specimens could be more effectively filled with higher percentages of coral powders being used in the experiments. However, excessive coral powders resulted in the reduction of specimen strength because these powders could easily be cemented into agglomerates by absorbing water from the specimens. These agglomerates could reduce the cementation strength between the coarse coral particles and the cement. Meanwhile, the peak stress of CCS specimens was found to be negatively correlated with the average strain rate and the ultimate strain. The degree of specimen fracture was found to be correlated with the amount of specific energy absorption during the tests. Furthermore, the “sulfate attack” caused by the inclusion of salinity of water had different influences on the CCS specimens with different coral powder contents. The ettringite and gypsum produced in “sulfate attack” could fill the pores and lead to cracking of the specimens, significantly affecting the specimen strength.     

Enhanced oil recovery from carbonate reservoirs by spontaneous imbibition of low salinity water

An experimental study was performed to investigate the impact of low salinity water on wettability alteration in carbonate core samples from southern Iranian reservoirs by spontaneous imbibition. In this paper, the effect of temperature, salinity, permeability and connate water were investigated by comparing the produced hydrocarbon curves. Contact angle measurements were taken to confirm the alteration of surface wettability of porous media. Oil recovery was enhanced by increasing the dilution ratio of sea water, and there existed an optimum dilution ratio at which the highest oil recovery was achieved. In addition, temperature had a very significant impact on oil recovery from carbonate rocks. Furthermore, oil recovery from a spontaneous imbibition process was directly proportional to the permeability of the core samples. The presence of connate water saturation inside the porous media facilitated oil production significantly. Also, the oil recovery from porous media was highly dependent on ion repulsion/attraction activity of the rock surface which directly impacts on the wettability conditions. Finally, the highest ion attraction percentage was measured for sodium while there was no significant change in pH for all experiments.     

Migration and distribution of saline ions in bauxite residue during water leaching

Bauxite residue, a highly saline solid waste produced from digestion of bauxite for alumina production, is hazardous to the environment and restricts vegetation establishment in bauxite residue disposal areas. A novel water leaching process proposed here was used to investigate the dynamic migration and vertical distribution of saline ions in bauxite residue. The results show that water leaching significantly reduced the salinity of bauxite residue, leaching both saline cations Na⁺, K⁺, Ca²⁺ and anions CO^2?₃, SO^2?₄, HCO^?₃. Na⁺ and K⁺ migrated from 40–50 to 20–30 cm of the column, presenting a high migration capacity. The migration capacity of Ca²⁺ was lower and accumulated at 30–40 cm of the column. CO^2?₃ initially distributed at 20–30 cm of the column, subsequently transported to 30–40 cm of the column, and finally returned to 20–30 cm of the column along with evaporation. SO^2?₄ was originally distributed at 40–50 cm, but finally migrated to 20–30 cm of the column. Nevertheless, HCO^?₃ remained at the bottom of the column, and its migratory was less affected by evaporation.     

裴沟煤矿典型断裂构造带水化学变化特征

断裂运动是错综复杂的地质作用，物质组成的变化能够通过水质中阴阳离子含量直观表现。以裴沟煤矿近20年来的突（涌）水点化验数据为依据探究各含水层水化学普遍性质，发现阳离子含量和矿化度可以作为水源判别的重要指标，以典型构造浮山寨断层为对象研究断裂构造带水化学变化特征，结果显示距离断裂构造带越近，水中Ca²⁺+Mg²⁺含量减小、Na⁺+K⁺含量增大、矿化度降低，揭示断层两盘不同含水层间水掺和程度。     

Impact of Divalent Ions on Heavy Oil Recovery by in situ Emulsification

Many reservoir formation brines are characterized by high salinity and contain high concentrations of divalent ions such as calcium, magnesium, and potassium. These challenging conditions can render the surfactants ineffective during chemical flooding for enhanced heavy oil recovery. Various brine types can have an impact on the stability of emulsions generated with chemicals as chemicals have various resistant levels toward hard divalent ions and salinities. To investigate the impact of brine hardness on heavy oil-in-water emulsion stability, glass tube experiments, microscopic visualization and sandpack flooding experiments, and Hele-Shaw visualization experiments were conducted in this study under low-salinity/hard-brine, high-salinity/hard-brine conditions using commercial chemicals, which are designed for specific reservoir brine conditions. Recovery results demonstrated that complex colloidal solution introduced in the previous study with silica and Dodecyltrimethylammonium bromide (DTAB) along with screened chemicals from glass tube tests in this study can enhance heavy oil recovery significantly with an addition of low concentration of xanthan gum (Lee and Babadagli 2018). The results confirmed the robustness of the complex colloidal solution formula to enhance oil recovery with low concentration of polymer under any reservoir brine conditions. The study also demonstrates the potential of polymer as an emulsion stabilization additive for enhanced heavy oil recovery by in situ emulsion generation. Polymer effects seemed to be particularly dominant under the low-salinity conditions than high-salinity conditions.     

Ocean thermal energy conversion by deliberate seawater salinization

Consideration is given to the possibility of ocean thermal energy conversion (OTEC) by the deliberate salinization of surface seawater. The proposed technique is similar to traditional OTEC, with one important exception: rather than cold water being brought from the bottom to the surface, the warm surface water is circulated to the bottom, cooled there, and lifted back to the surface. The entire process is driven by the induced salinity gradient at the surface. As a result, there is no need for a pumping system to bring the cold bottom water to the surface. Two methods are explored for surface salinity enhancement, namely solar evaporation and the direct addition of salt to the seawater.     

利用煤矸石制取净水剂研究

以天然煤矸石为原料,通过酸溶一步法将煤矸石中的氧化铝溶解取出来，并通过条件试验,确定溶出量最高时的工艺条件。再经过盐基度的调整(70％左右)。形成碱式聚合氯化物，该聚合物具有很好的絮凝作用，从而成为一种新型高效的净水剂。     

Soil salinity of urban turf areas irrigated with saline water: I. Spatial variability

With increasing use of saline water for irrigating urban landscapes, soil salinization is becoming a concern. This study examined spatial variation in soil salinity over the length of selected fairways at five golf courses, and of large turf areas at two public parks located in west Texas and southern New Mexico. Salinity of water used for irrigation ranged from 680 to 2700 mg L⁻¹, and the sites consisted mostly of Aridisols (upland soils) or Entisols (alluvial soils). Soil salinity distribution at sites consisting of deep Aridisols was spatially independent with the coefficient of variability (CV) ranging from 24 to 42%. The sites consisting of shallow Aridisols over a calcic horizon had erratic and random soil salinity distributions with an average CV of 37%. Since soil salinity distributions in Aridisols and Alfisols appeared to be spatially independent within the distance of fairways, soil sampling adequacy can be determined by the conventional probability statistics. However, salinity distributions at Entisols sites were spatially dependant to a length of 100 m or more. In addition, the clayey Entisols used for public parks had high levels of salt accumulation (>10 dS m⁻¹ in the saturation extract) with the CV exceeding 60%. When salinity readings were stratified by soil type distribution, the CV was reduced to 28% on the average. The number of samples required to obtain the mean salinity over a typical length of fairways (250–300 m) within a deviate range of 20% averaged 6 in deep sandy Aridisols and Alfisols, and 13 each in other cases, provided that sampling of Entisols is made based on soil type distributions. These sampling requirements are greater than those for field soil moisture or saturation water contents. The spacing to collect the required number of samples over the prevailing length of fairways was between 23 and 38 m. Soil sampling for salinity appraisal is most problematic in Entisols, but can be made simple if a detailed soil map is available. In Aridisols containing a calcic horizon, it is probable to have saline spots over poorly permeable caliche.     

含盐废水短程硝化反硝化生物脱氮的研究

试验采用SBR工艺研究了不同盐度下,NH+4N、pH值、温度等因素对含盐废水短程硝化反硝化的影响.结果表明,含盐量增加有助于亚硝酸盐的积累.含盐量在1759～24630mg/L范围内,通过提高进水pH值和进水NH+4N浓度,可以使亚硝化率[NO-2/(NO-2+NO-3)]达到90%以上.实验证明,亚硝酸菌有较高的耐盐性,能在高盐环境中保持良好的活性.