Oil and Water Separation

Flotation is a kinetic process. While a number of flotation models exist, Klimpel's first-order rate equation has been demonstrated to provide modelling flexibility, ease of physical interpretation and a good fit to the experimental data. The Klimpel model is written as:

exp( — kt) ~kt where R0(t) is the fractional recovery of oil at time t(s) and k is the characteristic first rate constant (s~J). The key to flotation is the production of air or gas bubbles. The two major techniques are known as dissolved air flotation (DAF) and induced air flotation (IAF). IAF can be further subdivided into mechanically and hydraulically induced flotation.

Mechanically induced flotation has now been used for about 100 years to separate from a suspension in water, particles of valuable mineral from gangue. In the mining industry this process is known as benefici-ation. It is now the main method of concentrating copper, molybdenum, iron, phosphate, lead and zinc ores. In the minerals industry the air is dispersed as bubbles, either through an impeller in subaeration cells or through spargers in flotation columns. These and other variants of the air addition to flotation pulps are classified as IAF. In the petroleum industry natural gas, carbon dioxide or nitrogen may be used as the flotation gas, hence the process is termed induced gas flotation or IGF. The use of these gases significantly reduces downstream corrosion problems and possible hydrocarbon degradation caused by the use of air.

Flotation techniques can remove dispersed, but not dissolved oil. As environmental legislation specifies both the limiting oil concentration and also the biological oxygen demand (BOD) in the discharged water, flotation is often the second stage of a three-stage effluent treatment process of gravity separation, flotation and biological treatment. As an example, British Petroleum's Grangemouth facility has achieved discharge concentrations of 2-3 mg L_1 oil-in-water using gravity separation in American Petroleum Institute (API) separators, followed by IAF with a final biological treatment stage to remove dissolved BOD materials including ammonia, phenols and sulfides. Limits for oil-in-water discharges vary around the world, typically between 15 and 40 mg L_1. A maximum BOD of 216 mg L_1 daily, with a monthly average of 53 mg L_1 is considered to be achievable via the application of the best available technology by the United States Environmental Protection Agency.

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

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