Treatment of Oily Waste Using a Scaled-up Carbonization Kiln

Abstract

Treatment of oily wastes generated in production and refining processes is one of the major environmental issues facing the petroleum industry in oil producing countries. Oily wastes such as crude oil storage tank sludge and oil-based drilling mud contain various hazardous materials such as oil (petroleum hydrocarbons) and heavy metals. Generation of oily waste is increasing, and combined with the processing cost and capacity limitations of currently available treatment technologies, is resulting in the accumulation of large amounts of untreated oily waste1). Consequently, inexpensive and effective treatment methods are now needed. Various technologies have been investigated for the treatment of oily wastes. Solvent extraction2),3) has high oil removal efficiency, and allows oil recovery, but the cost is very high and so is considered to be impractical. Biological treatment methods4)~7) capable of large-scale treatment such as land farming can be implemented at low cost, but the treatment period is lengthy and the space requirement is large. Additionally, some oily wastes such as crude oil storage tank sludge contain resin and asphaltene that is difficult to treat biologically. Thermal decomposition treatment8),9) such as carbonization has high oil removal capability and also allows oil recovery, so development continues as a promising technology. For example, addition of various catalysts improves the oil recovery amount and recovered oil quality, resulting in decreased overall treatment cost10)~14). However, the properties of oily wastes can vary greatly by location and over time1),15), so thermal decomposition treatment using a catalyst must adapt the optimum conditions, such as catalyst type and addition amount, to the properties of the oily waste to be treated. This study investigated carbonization treatment (pyrolysis) using superheated steam, without any catalyst, to remove oil from waste. Superheated steam is generated under the operating pressure (steam at 100 °C under normal pressure) and further heated to a temperature higher than the boiling point. This superheated steam heats anoxically, as heat is directly applied without air. Air heating acts only by convection, whereas superheated steam has very high heat energy that can be transferred by condensation and radiation, as well as convection, resulting in superior heat efficiency compared to air heating. In an earlier study16), carbonization treatment using superheated steam removed oil concentrations in waste [Regular Paper]