Abstract

Increasing concern over the pollution of our environment has paved the way for stricter abatement policies to be employed mostly on the national level. The effectiveness of the enforcement of these policies is directly related to the required investment and available technologies. The greatest challenges of the refining industry is to produce fuels satisfying specifications and environmental regulations required in this Millennium. As the specifications tighten, the conventional refining technologies becoming redundant or obsolete and the refiners are forced to deal with molecules rather than boiling ranges.

The abundance of global natural gas resources can be used to make cleaner fuels. Over the last few years, there has been a great deal of attention focused on technologies to convert natural gas into liquid fuel. This paper presents the salient features of the processes, techno-economical and environmental aspects of two main GTL (gas to liquid) products viz., (i) Fischer-Tropsch (FT synthesis products and (ii) Dimethyl ether (DME).

Introduction

Refining is under increasing pressures from a number of sources but perhaps the greatest challenge is to meet the fuels specifications required in future. The main drivers for tighter fuels quality specifications are: Fuels quality and environmental legislation, reduced tail pipe emissions, reduced emissions for refineries and poor refinery structure. The effectiveness of the enforcement of these policies is directly related to the required investment and available technologies. Concerns about air pollutants caused by petroleum-based fuels have prompted government involvement in formulation of stricter environmental regulations and providing tax incentives to use alternative cleaner fuels. Pollutants of concern include nitrogen oxides (NOx), carbon monoxide (CO), carbon dioxide (CO2), sulphur dioxide (SO2), volatile organic compounds (VOCs), particulate matter (PM) and the formation of pollutants in the atmosphere by photochemical reaction leading to the build-up of ozone in the lower layers of the atmosphere.

Two approaches are generally employed to reduce vehicle pollution:

  1. Altering standards of tail pipe emissions for new vehicles; and

  2. Altering composition of the fuel.

The first approach is the most popular one. The drawback of this approach is that it is a long-term policy that can only have effects when old vehicles are replaced by new ones. Today's new cars produce about 95% less air pollutants (volatile organic compounds, CO, NOx) than new cars in the 1960s [1]. Three-way catalytic converters, direct injection engines, and other advanced automotive technologies have greatly improved the efficiency of light duty vehicles.

The second approach involves altering the composition of fuel which can have a more immediate impact on vehicle emissions. Maintaining transportation fuel quality in the regulatory environment during the recent years has become a balancing act between regulating agencies and the petroleum refining industry. Regulations modifying gasoline and diesel fuel composition will be promulgated to improve air quality and reduce human exposure to critical hydrocarbons.

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