Gas hydrate-based Separation as opportunity to reduce the nitrogen footprint of fertiliser plants: A short review of available thermodynamic data

摘要

Gas hydrates, which are ice-like solids, form a subgroup of inclusion crystalline compounds known as clathrates. Clathrates consist of appropriately sized small molecules (guests) encapsulated in cage-like structures made of hydrogen bonded-molecules (hosts), due to van der Waals force. When the host and the guest are water and a gas respectively, the resulting structure is referred to as a gas hydrate. It is well known in chemical engineering that gas hydrates lead to the clogging of pipelines during flow assurance operations. However, they can be advantageously exploited in separation processes. With regard to fertilizer plant operations, some experimental hydrate dissociation data have been reported in the literature for nitrogen as well as ammonia containing mixtures. The present communication is a review of these experimental data which can be used to analyze, design and optimize hydrate-based separation processes. Additionally, a discussion is made on the effectiveness of gas hydrate technology as a novel and environmentally friendly way to separate streams encountered in nitrogen-based fertilizer plants. The end of the present review is a focus on important questions that researchers have to address in view of the industrial implementation of gas hydrate-based separation technology in nitrogen-based fertilizer plants.