The feasibility studies on sonochemical processes for treating used oil: Toxin reduction for eliminating recycle interference.

摘要

Biochemical processes are well known for their superior performances in the upgrading of heavy crude oils. Based on a similar experimental strategy, a new technology was developed using biochemical process for the conversion of fossil fuel wastes into valuable biomaterials. The technology, developed by Brookhaven National Laboratory and based on a well-developed "Hydrocarbon to Protein" technology, is able to convert used oils to commercially valuable products through a biochemical process.Production and utilization of fossil fuels generate wastes that contain EPA priority pollutants, such as polyaromatic hydrocarbons (PAH) and toxic metals. Used oil, which often contains metals, chlorinated hydrocarbons and other organic compounds, including many that are listed as EPA priority pollutants, is a good example that is generated at a rate of more than 1.5 billions gallons per year in the U.S. As a result, the associated impact to the environment is huge when there is uncontrolled dumping and landfilling of used oil in the environment. Used oil is a valuable resource and a vital source of energy it still has lubricating value and heat value. Following the proper treatment to remove contaminants, used oil can be re-refined into base lube oil, reprocessed as fuel oil, or used as feedstock to produce petroleum-based products or other commercially valuable products via different processes. The high contamination levels in some used oils, however, increase the difficulties in the operations and generate hazardous byproducts as secondary pollutants. A large portion of the recycled used oil is combusted for energy utilization (often creates air pollution problems) or thermally destroyed by incineration (only when the oil has a high concentration of toxic contaminants that makes recycling impractical or unsafe).For BNL's process, preliminary results showed that biomass generated from used oil contains 90% delipidated biomass and 10% lipids. The live biomass, delipidated biomass, and lipid have been proved successful in many applications and have high market values. However, there are problems encountered in the process, such as the poor quality and inconsistency of the bioproducts. The contaminants in the used oil are toxic to the bacteria strains used in the biochemical process and lower product yields. Another concern is the potential bioaccumulation of these toxins in the bioproducts. A proper pretreatment process is necessary to remove these toxins from the used oil stock to enhance the yield efficiency of the bioconversion process and improve the quality of the bioproducts.A chemical-aided ultrasonic irradiation method is proposed to remove/degrade the toxins from used oil. Target contaminants that need to remove from used oil include heavy metals, chlorinated hydrocarbons, BTEX compounds, PAHs, and PCBs. Ultrasound irradiation is widely used in environmental cleanup applications to remove/degrade many toxic compounds in contaminated soils and waters it is proven to be effective on many fossil fuel related applications, including upgrading and recovery. Free radical chain reaction is believed to be the dominant reaction to cause the effects in these systems. Ultrasonic irradiation has the ability to initiate and enhance the free radical generation from both water molecules and hydrocarbons. Hence, it could effectively remove/degrade the toxins in used oil with appropriate chemical additions. If technically and economically proven feasible, the chemical-aided ultrasonic irradiation process may be used not only as the pretreatment step for BNL's biochemical process, but could also become a pretreatment package in other used oil recycling and reprocessing options.To develop a pretreatment package for BNL's process (biocoversion of used oil), the chemical-aided ultrasonic irradiation is server as the basic terminology. Accompanied by destructive adsorption process, the removal efficiency for the decontamination of used oil is greatly enhanced. Optimal operating conditions will be examined and from the results of this study, it seems that this process is a feasible option to pre-treat toxic contaminants before further recycle or reuse options are applied to used oil.