(103b) Separation of Ethane-Ethylene in High Flux Microchannels
AIChE Spring Meeting and Global Congress on Process Safety
Tuesday, April 8, 2008 - 8:55am to 9:20am
Ethylene is one of the largest volume petrochemical produced worldwide. This important intermediary is produced in extremely large plants that make 20 billion lb/year ethylene or more. These plants feature 20 or more fractionation columns, which are needed to separate and purify the key products (ethylene and propylene) from the gas effluent leaving the cracking furnaces. The most challenging separation is the splitting of ethylene from ethane in the ?C2 splitter.' The relatively small volatility ratio of ethylene in ethane results in conventional towers which are very large, up to 300 feet tall. This size is limited by manufacturing and transportation constraints, limiting the benefits from economies-of-scale. Microchannel distillation technology holds the potential to greatly improve the ?C2 splitter' by shrinking the size and cost of distillation hardware, and reducing energy consumption.
Microchannels with small characteristic dimension have low mass transfer resistance due to smaller diffusion distances. The increased mass transfer in microchannels enables a large reduction in the Height of an Equivalent Theoretical Plate (HETP). This permits separation hardware based on microchannel technology to have shorter height, smaller footprint, and more stages for efficient separation. Microchannel technology is scaled up by numbering up, adding identical channels or more modules. This modularity allows microchannel technology to benefit from the economy-of-mass-production.
A microchannel device was built and tested to evaluate the ethane-ethylene separation. A steady and consistent separation performance was achieved in the microchannel device. Evaluation of the data showed an achievement of HETP of 63 mm compared to more than 500 mm in a conventional distillation column. This presentation will discuss the experimental set-up and results, as well as the commercial application of this innovative technology.