Greenhouse Gas Emission Reduction and Tailgas Maximization at ORYXGTL

Abstract

Abstract ORYX GTL, a joint venture between shareholders Qatar Petroleum and Sasol Synfuels International, is a pioneering gas-to-liquids (GTL) facility that produces premium diesel fuel, naphtha and LPG. The objectives of this paper are related to Greenhouse Gas (GHG) management at ORYX GTL: it aims toidentify the various sources of GHGdescribe the methodology to quantify GHG emissionsidentify various opportunities to reduce GHG emissions, andprovides a case study on GHG emission reduction through utilization of tailgas as fuel in fired heaters. The paper is organized in two sections; the first section presents a brief overview of the ORYX GTL process, identifies the various GHG emission sources, quantifies the GHG emissions and describes the concepts and options to reduce GHG emissions. The second section describes a case study on the opportunity to optimize fired heaters to make use of tailgas and steps that can be taken to make use of these opportunities. A brief overview is also provided on projects executed by ORYX GTL to support the company's strategy of optimizing sustainability and stability by reducing GHG emissions. The major GHG emission sources from the ORYX GTL facility are broadly classified as combustion and flaring emissions. The GHG emissions at ORYX GTL are derived from estimates and calculations taking into account the composition of fuel streams, the energy content of the fuel, available measurement data, emission factors and mass balance approaches. It was found that flaring of tailgas contributes significantly to the release of GHG emissions from the ORYX GTL facility. The GHG reduction was achieved by making use of Advanced Process Control techniques, utilization of tailgas for fuel, and recovery of low pressure vent gases to use as fuel in process heaters. The use of tailgas as a fuel to fired heaters increased from 10% to 90–95% of total heat duty since start-up. The increase of tailgas as fuel resulted in the reduction of natural gas as fuel, improving the carbon efficiency of the plant and thus reduced the environmental impact. In 2012, a 23% reduction in GHG emissions was achieved compared to 2011 levels due to maximizing tailgas utilization as fuel and stable plant operations. The results from this study highlight that a further reduction of GHG emissions is achievable by focusing on plant stability and flare reduction projects. 1. Introduction The growing world energy demand for fossil fuels plays a key role in the continuous increase in GHG emissions into the atmosphere. According to the IPCC, atmospheric GHG concentrations will more than triple in the next 50 years compared to pre-industrial levels if no action is taken, posing climate change risks such as damage to natural ecosystems and more extreme weather conditions [1]. As global concerns intensify to reduce GHG emissions, there is a continuous increase in demand for ultra-clean fuels derived from natural gas. Gas-to-Liquids (GTL) technology converts natural gas into high performing, ultra-clean liquid fuels, as alternatives to the conventional refining of crude oil. In the past ten years, there have been technological advances in developing GTL technology on a larger scale, with several commercial scale plants commissioned. This new and emerging technology is expected to contribute a larger share of the world's gas-processing industry in the future [2, 3].