Centrifuge Applications in the Field of Oil Spill Recovery
Oil spills in salt and fresh water occur on a regular basis. Off shore drilling and shipping necessarily involve some degree of risk. There is some "leakage" that occurs as a result of any drilling and harvesting operations. Pipelines, loading points and shipping all represent risk for inadvertent release of the oil into the surrounding waters. Some amount of the expected leakage is typically handled by natural dispersion and degradation with no significant affect on the surroundings, but in instances where leakage exceeds those limits generally considered acceptable recovery of the oil is necessary and desirable for both environmental issues and economic reasons.
Separating water from oil is a necessary and continual part of any oil spill recovery operation. Although the environmental concerns related to these issues are of paramount importance, this article addresses the practical issues relating to the fields of sedimentation and centrifugation.
The transportation and storage costs of large volumes of polluted water, the labor and materials involved and the salvage value of the recovered material are all of concern when evaluating oil spill recovery technologies.
Although technologies have been tested and used in the recovery of oil from many of the spills which have occurred as a result of the production and handling of oil, no environmentally and economically successful strategy currently exists for dealing with oil spills.
Technologies
The first factor affecting the oil recovery process is the oil to water ratio. When a spill is contained in a boom and the water is calm the ratio of oil to water can be as high as 90% oily phase. In uncontained spills with turbulent water free water might represent 98% (or more) of the fluid.
The adage that water and oil do not mix is somewhat accurate. However, crude oil and intermediate to heavy oil products generally emulsify (forming a water in oil emulsion (W/O emulsion) (resembling chocolate mousse)) in salt water. Over time spilled materials degrade (this is sometimes called weathering.) Currents, wind and waves, watercraft and obstacles such as piers, rocks dams all agitate the water and oil. The stage of degradation and emulsion will effect the separation process. De-oiling and draining of free water is governed by Stoke's law which indicates that droplet size and velocity can be crucial to ease of separation. Both sedimentation and centrifugation processes can be used to recover materials released in oil spills.
Coalescing and Gravity Type Separation
In order to increase the speed (and/or volume) of separation an oleophilic medium (attracting the oil and providing a barrier between the oil and the water) may be employed to improve adherence and collection efficiency.
Centrifugal Separation
Hydroclones and centrifuges may be used for oil spill recovery. Typically hydroclones are most effective when the oil to water ratio is 25% or less. The turbulence related to the centrifuge process increases emulsification, therefore the geometric design of the hydroclone must be specific to the application.
A Partial List of Companies Providing Industrial Centrifuge Equipment:
Company Profiles
Companies headquartered in China are listed separately because of the size of the Chinese market and the number of participants. Most provide a substantial portion of their product for export.
Jiangsu HuaDa Centrifugal Machine Manufacturing Company
Liaoyang Longda Pharmaceutical Machinery
Liaoyang Sunny Pharmaceutical Machinery Co., Ltd.
Liaoyang Xianglong Pharmaceutical Machinery Co., Ltd.
Peony Filtration and Separation
Rotofilt Engineers Ltd (India)
Suzhou Sea Whale Centrifuge Co
Tianxing Pharmaceutical Machinery
Zhangjiagang Peony Machinery Company LTD.
Centrifuge equipment is typically designed for a specific application. The shape of the vessel, speed of rotation, location and orientation of the inlets and outlets and the materials used are just a few of the considerations in the design process. All applications involve relatively high G forces and the products being separated in many applications are abrasive. Therefore, maintenance is a crucial and costly consideration when centrifuge equipment is being used. As such, there are many local repair and maintenance facilities with knowledgeable personnel. Frequently these local shops can provide used or reconditioned equipment for applications when a fast delivery is required.
A Partial List of Representative Industrial and Municipal Centrifuge Applications
In most applications the materials being separated would, given time, separate without intervention. Centrifuge equipment is generally used to either facilitate the process or to do it more quickly.
In some cases, like oil spills, the materials would separate relatively quickly but external factors make mechanical separation necessary. For instance, in the case of an oil spill in open ocean, wave action prevents natural separation of the materials and the moral and environmental imperative to prevent damage to fragile ecosystems makes speed of the essence.
In other cases, like tar sands, the separation would require periods of unacceptable duration. Waste water treatment dewatering is frequently performed using centrifuge equipment because of geographical space constraints. The factors affecting the applications vary.
Waste Water Treatment
Biofuel Applications
Food and Beverage Production
Bulk Chemical Manufacturing and Reprocessing
Metalworking
Mining
Water Treatment for Utility Applications
Dewatering of Oil Shale and Natural Gas Fracturing Applications