This paper presents a computational scheme for predicting the sequential variations in the gas-phase composition and clathrate structure of hydrates formed in a reactor during a continuous or semibatch operation for producing hydrates from multiple guest substances, typically fuel-gas-composing hydrocarbons plus a large-molecule guest substance (LMGS), which provides guest molecules to fit into the 51268 cages of a structure-H hydrate. The scheme is based on the thermodynamic modeling of the hydrate-forming operations such that the entire contents of the reactor are defined as a thermodynamic system and that the transient hydrate-forming process, which the system is to follow during each operation, is assumed to be a series of a numerous number of equilibrium states each slightly deviating from the preceding state. For the computational scheme, each equilibrium state of the system is specified with the aid of a proper phase-equilibrium calculation program (e.g., CSMHYD), and the system is forced to advance from one state to another by removing from the system in the former state a prescribed number of gas molecules fixed in a hydrate product and, at the same time, adding the same number of feed-gas molecules to the system, thereby maintaining a constant system pressure. Repeating such a state-to-state transition, thereby continually renewing the three- or four-phase system inside the reactor, we can simulate the entire process of each hydrate-forming operation. The paper exemplifies the application of this scheme to the simulations of the continuous and semibatch operations for forming hydrates from a methane + ethane + propane mixture with or without an LMGS. This scheme can be a useful tool for estimating the evolution of the crystallographic structure and composition of hydrates formed during industrial operations for processing gas mixtures such as natural gas and biogases.
ASJC Scopus subject areas
- Chemical Engineering(all)
- Fuel Technology
- Energy Engineering and Power Technology