(8a) How to Reduce CO2 Emissions of Steam Cracking Furnaces: The Million Dollar Question

Steam cracking of hydrocarbons is and will continue to be the main industrial process to produce light olefins in the coming decades. As illustrated below steam cracking is today still the best technology to produce on a large scale olefins in comparison to other proven technologies such as Fischer Tropsch, methanol to olefins and the more exotic oxidative coupling of methane.

In state of the art steam cracking plants more than 90% of the CO₂ emissions can be directly related to the high energy consumption of the endothermic conversion in the cracking furnaces. Steam cracking accounts for a global emission of more than to 300 million tonne of CO₂ per annum. Enhancing heat transfer in the radiation section, using green energy and reducing coke formation are key to substantially reduce CO₂ emissions. Heat transfer can be increased by implementing three-dimensional (3D) coil technologies such as swirled and dimpled tubes. These reactor technologies also reduces coke formation because of the lower wall temperatures that are consequently obtained. Advanced manufacturing techniques and better computational abilities have opened the doors to novel and improved 3D reactor technologies that are designed to increase the heat transfer while minimizing the pressure drop penalty. At the same time applying high emissivity coatings on the furnace refractory and reactor tubes can further reduce CO₂ emissions. Substantial fuel savings can also be obtained by a novel furnace design, where the heat recovery scheme is substantially modified. Combining all these technologies could result in reducing emissions with 30%. Shifting completely to green electricity, which is practically infeasible today, is another alternative but the technologies that would potentially allow this are still in their infancy. These new technologies, combined with advanced process innovations and CO₂ capture, will help the industry to meet future emissions targets. The potential benefit of small and larger modifications have been quantified by accounting for the additional annual production of high value chemicals, extended run length as well as reduction in fuel consumption and hence direct CO₂ emissions, compared to a base case being state of the art steam cracking furnace. The evaluation has been carried out by means of COILSIM1D for the following cases:

• carbon capture and storage with or without oxyfuel combustion in a steam cracking furnace
• hydrogen fired steam cracking furnace
• Carbon capture and utilization by electrochemical conversion of CO2
• Electrification of the furnace (different technologies among other Coolbrook)