Proposal of a theoretical model for dry ice (solid CO2) formation and agglomeration in natural gas mixtures


The presence of CO2 on the Brazilian pre-salt gas results on challenges to the production facilities. To remove the CO2 , the process plant is equipped with systems capable of handling concentrated CO2 at high pressure with the objective of re-injecting it back to the reservoir. The solid CO2 (dry ice) can deposit while the natural gas mixture is depressurized, creating a threat in terms of process safety. The dry ice can agglomerate inside the piping, causing a blockage, which can lead to overpressure and possibly loss of flammable gas containment. Based on the criticality of a flammable gas release in conjunction with the limited literature references, this study developed a model capable of predicting the formation and agglomeration of the dry ice inside of a relief system. The model is based on process simulations, pneumatic conveying principle and is reliable once it was validated using an experimental study conducted by Maher et al. (2016). The model presented a variation of 11 to 21% in terms of solid deposition in comparison with the experiments. Additionally, it suggests the piping blockage could occur once two criteria are satisfied: a) minimum gas flow and b) the amount of dry ice deposited. The study concludes dry ice particle size and the heat transfer profile are the most important parameters for the model, also suggests the use of the tool as reference to design and operate facilities with the requirement of handling pressurized CO2 streams.

SANTANA, Flavio Cesar Imazu; ALDEIA, Wagner. Proposta de modelo teórico para formação e aglomeração de dry ice (CO2 sólido) em mistura de gás natural. In: RIO OIL & GAS EXPO AND CONFERENCE, 2022, Rio de Janeiro. Proceedings… 11 p.

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