Field test evaluations of a liquid desiccant system for air dehumidification at a gas pressure station

• Two-year field test of a liquid desiccant system at a gas pressure station. • System operated continuously with and without internal absorber cooling. • Internal absorber cooling improved moisture removal rate by up to 70 %. • Up to 21 % annual primary energy savings for natural gas preheating. A full-scale, internally cooled/heated liquid-desiccant system was installed at a gas pressure regulating and metering station to dehumidify outdoor supply air to a low dew point (∼1 °C), enabling low post-expansion gas temperatures while avoiding external condensation. Prior work has paid little attention to dehumidification-enabled savings in natural-gas preheating and dynamic field-based assessments of liquid desiccant systems—especially comparisons of absorber operation with and without cooling—are scarce. These gaps were addressed by analysing two years of field measurement data to characterize liquid desiccant system performance depending on absorber mode (with and without cooling) and to determine annual natural-gas preheating savings achieved by dehumidification. From field data, annual primary-energy savings due to dehumidification with absorber cooling were quantified relative to no dehumidification. Using the same boundary conditions, TRNSYS simulations quantified summer natural-gas preheating savings for operation without absorber cooling. Results show that the difference between the heating- and cooling-water inlet temperatures of the liquid desiccant system strongly affects the moisture removal rate and provides a possibility to control the outlet humidity ratio. Increasing this temperature difference by 10 K raised the moisture-removal rate by up to 35 %. Absorber cooling increased the moisture-removal rate by 54 % but reduced the thermal COP by 30 % at an outdoor-air humidity ratio of 10 g kg −1 compared to operation without absorber cooling. Annual primary-energy savings for natural-gas preheating reached up to 21 % (230 MWh). In summer months internal cooling nearly doubled energy savings in natural gas preheating compared to operation without cooling.