China 
Africa 
Explore chapters and articles related to this topic
Soil Vapor Stripping
Published in David J. Wilson, Ann N. Clarke, Hazardous Waste Site Soil Remediation, 2017
David J. Wilson, Ann N. Clarke
The effects of kinetic limitations on the vapor stripping can be explored in several ways. The well may be operated for a time, shut down for a period, and restarted. If kinetic effects are significant, the VOC soil gas concentration will increase during the period of shutdown; the time dependence of this recovery yields the rate constant for the kinetic processes.The well may be operated at several different flow rates and the VOC soil gas concentrations determined at these flow rates. If kinetic effects are significant, VOC concentrations will be lower when the gas flow rate is higher. The rate constant for the kinetic processes is determined from the relationship between the VOC concentrations and the gas flow rate.Mutch (1990)has suggested that clean air be pumped down through the well and into the surrounding domain. After an interval this gas is sampled and analyzed for VOCs. Several experiments of this type would map out the rate of equilibration of the injected air with the surrounding contaminated soil and yield the rate constant for the kinetic processes. Note, however, that the lumped-parameter method used here replaces what is presumably a rather broad distribution of time constants with a single value. Tests should be designed to estimate a value representative of the long time constants (the small rate constants), since these are what will ultimately control the rate of removal of VOC along toward the end of the remediation. Mathematical analysis of diffusion problems of this sort leads to a spectral distribution of eigenvalues—the inverses of the time constants for the decay of the system toward equilibrium. The smallest eigenvalue yields the longest time constant, which ultimately controls the rate of cleanup (Wilson, 1990).
Preparation and evaluation of new liquid crystal compounds as flow improvers for waxy crude oil
Published in Journal of Dispersion Science and Technology, 2022
Ashraf M. Ashmawy, El-Sayed M. Elnaggar, Manal G. Mohamed, Mohamed C. Hamam
Paraffins are mixtures of hydrocarbons with linear/normal chains comprising mainly of 20–40 carbon atoms, in addition to alkanes with branched and cyclic chains. Paraffin crystals grow with a decrease in temperature, creating a crystalline network, which begins to retain liquid hydrocarbon molecules so that the oil cannot flow, causing many problems during production and transport across pipelines. This effect increases dramatically in the winter. Paraffin problems result in losses of billions of dollars per year to the petroleum industry worldwide through the cost of reduced production, chemicals, well shut-in, capacity reduction, flow-line restriction, equipment failure, and higher horsepower and manpower requirements.[3,4] The wax crystals are generally irregularly shaped (platelet- or needle-like) and can form a continuous three-dimensional network at relatively low concentrations (around 1 wt%).[5,6] In general, the flow problems become greater as the wax content increases.[7]
Nanocomposite gels for water shut-off and temporary plugging in the petroleum industry: a review
Published in Petroleum Science and Technology, 2022
Juan Du, Qiang Wang, Pingli Liu, Gang Xiong, Pengfei Chen, Xiang Chen, Jinming Liu
This article reviews the development of nanocomposite gels used for water shut-off and temporary plugging in the petroleum industry and reports several common nanocomposite gels. According to the classification of nanoparticles used, nanocomposite gels are divided into nano-silica-based nanocomposite gels, nano-montmorillonite cross-linked nanocomposite gels, silicate nano-intercalation composite gels, and hectorite-based nanocomposite gels, CFA-based nanocomposite gels, and so on. Starting from the three elements of the materials used, the preparation mechanism, and the performance, the strength, temperature resistance and recent development trends of nanocomposite gels are reviewed.