Abstract

Norske Shell plans to develop and demonstrate a new technology for power generation from natural gas, which allows efficient and economic capture of the exhaust CO2 for subsurface sequestration. The technology will be suitable for deepwater offshore deployment on floating production facilities. The demonstration project will be a showcase for sustainable development principles, as it will provide power, heat and nutrients to a fish farm

Key Themes

  1. CO2 capture allowing sequestration

  2. Development of high efficiency fuel cells

  3. Integration with another key Norwegian Industry - fisheries

Introduction

Capturing the carbon dioxide emitted by fossil fuel powered electricity generation plants without incurring significant penalties on the efficiency of the conversion process has so far been an elusive goal. In Norway, this search has been driven specifically by strong direction from the government, which seeks to reduce or eliminate CO2 emissions from offshore production operations in a cost-efficient manner. The Norwegian effort is part of a wider global response to concerns about climate change.

A new technology will be demonstrated that is capable of recovering all of the CO2 that would normally be emitted without compromising the high net efficiency of the conversion process. In addition, the demonstration project will show how the power plant can be integrated with a fish-farming project closing an environmental loop in the carbon cycle.

CO2 capture from fossil fuel power generation

A main factor spoiling the economics of CO2 capture from fossil fueled power plants is the low CO2 content of the flue gas, which in the case of a gas turbine power plant is typically in the range of 3% [Langeland and Wilhemsen, 1993] Recovering CO2 at the these low concentrations is expensive and requires significant amounts of energy, which reduces the power plant's net output by as much as 20% [Herzog, Drake and Adams, 1997] The reason for the low concentration of CO2 is that the combustion processes uses air instead of pure oxygen so that the exhaust stream will contain huge amounts of nitrogen. Not only that, some of the nitrogen usually reacts at the high temperatures prevailing to form NOX pollutants To avoid nitrogen dilution it is necessary to have a nitrogen free source of oxygen. This means either an air separation plant or performing the carbon oxidation reaction with oxygen derived from another substance. Various processes can perform this latter trick, for example using water in combination with a shift reaction or a cycle in which copper oxides are alternately oxidised with air and reduced with fuel. The costs and technological requirements for doing any of the foregoing are high.

Basics of the SOFC

Solid oxide fuel cells are one off several types of fuel cells all of which comprise an electrolyte layer interposed between two electrodes. Oxidation of fuel continuously supplied to the anode proceeds via the electrochemical reaction:

O + CO= CO 2 + 2e

O + H2=H2O + 2e

At the cathode the reduction reaction

O2+ 4e=2O takes place.

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