Simulation of Dehydration Unit with a Pre-cooler to Improve the Hydrate Formation Temperature of Natural Gas

Abstract

The presence of water vapor in natural gas can cause several problems such as corrosion in transmission pipelines, blockage of equipment, and reduction of pipeline capacity. Dehydration is a critical step to reduce the water content to prevent these serious drawbacks. The adsorption process is one of the efficient technologies for producing natural gas with low water content. In this study, the industrial molecular sieve-based dehydration unit is simulated. After validating the simulation results with the plant data, the effect of feed gas cooling before entering the dehydrator on the hydrate formation temperature of the produced dry gas is investigated. To do so, we simulate the dehydration unit with a pre-cooler and design the heat exchanger to reduce the feed gas temperature. In addition, we investigate the effect of temperature reduction on the temperature of hydrate formation and water content for dry gas products. On the other hand, the effect of heating time in the regeneration step on the unit performance is discussed. Because of sufficient cooling operation, the temperature of hydrate formation reduces significantly. For the reduction of 15℃ in the feed temperature, about 50% reduction in the product water content is attained. As a result, the improvement of 6 to 7˚C in the temperature of hydrate formation is achieved for the proposed dehydration process with the pre-cooler in comparison with a simple dehydrator scheme depending on pressure. For the proposed heating time of 8000s, the rise of 6.8% in the total amount of the removed water is achieved.