A novel absorption process for small-scale natural gas dew point control and dehydration

• Hydrocarbon and water dew-point specifications can be met in one process step.
• Energy consumption is up to 52% lower than other process schemes.
• Investment and operating costs are lower than commercial technologies.
• Heavy hydrocarbon absorption is more selective with less reduction on gas flow.
• Process is simpler and operation conditions are less severe than other processes.

Heavy hydrocarbon removal is one of the processes found in natural gas processing plants for reducing heating value and hydrocarbon dew point to sales gas quality. Conventional technologies include Joule–Thomson expansion, turboexpansion, mechanical refrigeration, membrane separation and supersonic centrifugal separation. In this paper, a novel absorption process system is presented for dew point control of natural gas streams associated to crude oil production. The system is based on simultaneous absorption of heavy hydrocarbons and water from natural gas using a mixture of TEG and lean oil. This alternative technology has an equipment count, investment and operating cost, and energy consumption lower than commercial technologies available nowadays. Natural gas processes are modelled and simulated within Aspen Plus® simulator with a common set of operating criteria and adjusted thermodynamic interaction parameters for the absorption process, based on experimental data. An energy balance and economic assessment for each process option are developed considering investment and operating cost and profitability analysis. Results indicate an increase in hydrocarbon absorption efficiency with increase in lean oil concentration; 46% of pentane plus components can be removed with a 20% of lean oil. Energy consumption is up to 52% lower than other process schemes, while capital cost and operating cost are also 40% and 25% lower. Process description, operating conditions, equipment requirements, recovery efficiency and limitations for the new absorption process are presented.