Process optimization

Abstract

The adsorption process of a dewpoint correction unit (DPCU) can be optimized in several different ways. The right combination of design parameters, integration of equipment and implementing client specific requirements will lead to an optimal performance of the process unit. All with one goal in mind; to lower the total cost of ownership. We applied this philosophy on a DPCU based on proven silica gel adsorption technology. This process installation removes heavier hydrocarbons and dehydrates the natural gas before it is transferred to the national gas grid. The unit includes 12 Silica Gel adsorption towers and related regeneration equipment. A focus on energy saving with strict limitations on power consumption was the starting point for the design of this DPCU. Extensive analysis on heat integration has resulted in several optimizations of the system, e.g. reduced equipment size and selection of sophisticated insulation materials. Furthermore we also challenged the commonly applied method of time based switching. Switching based on dew point measurement, using the adsorption capacity to the full extent, allowed us to reduce the number of heating cycles per year. By considering the fact that the unit is not an isolated system, but part of a plant, we also evaluated the impact of pressure drop over the unit, regeneration gas flow and plot space. Changes in any of these parameters would influence the design significantly. Taking all of the above into account a peak power requirement reduction of 50%, on average even 60%, was achieved. By using the adsorption capacity to the full extent, less regeneration cycles are required (23%), leading to an increased bed lifetime. These optimizations significantly reduce the total cost of ownership and lead to higher efficiency on all levels.