Joule-Thomson cooling

Gas can be condensed by (a) mechanically refrigerating it, (b) compressing and expanding it, using turboexpanders, or, (c) pressure effects such as by Joule-Thomson cooling and overcoming the vapor pressure. The liquefaction of methane can involve all three of these effects. These effects can be separately evaluated to show the effectiveness of each in producing liquid. 

Two-sided dissociation eliminates the Joule-Thomson cooling that may stabilize the downstream end of the plug. With radial dissociation along the plug, two-sided dissociation is more than twice as fast as single-sided dissociation. 

To reduce the work of compression in this cycle a two-stage or dualpressure process may be used whereby the pressure is reduced by two successive isenthalpic expansions. Since the isothermal work of compression is approximately proportional to the logarithm of the pressure ratio, and the Joule-Thomson cooling is roughly proportional to... 

Little, W. A., (1990) Advances in Joule-Thomson Cooling, Adv. Cryogenic Engineering, Vol. 35, Plenum Press, pp. 1305-1314. 

For any flow rate the temperature rise at T2 (or T3) due to the energy input to the calorimeter can now be calculated as the difference between the (Fa — Ti) values for the energized and non-energized states. This method compensates for any Joule-Thomson cooling of the vapour due... 

The Joule-Thomson cooling effect of expanding CO2 through the plant—from feed gas pressure to atmospheric pressure—cools the solvent. No additional equipment is required to realize this benefit. 

Useful observations have also been obtained based on a comprehensive assessment of the Joule-Thomson cooling effect predicted for CO2 pipehne packing during the initial system startup. The assessment results from a series of dynamic simulations built upon different operating scenarios. 

While planning and developing the detailed operational procedure for packing the CO2 pipeline for a particular CO2 Injection project, the operations team needs to determine the amplitude of potential Joule-Thomson cooling over a ball valve in the equalization (pressure bypass) line - in order to assess dry ice forming possibility and potential pipeline integrity risk associated with the CO2 packing process. 

A significant Joule-Thomson cooling is suspected to lead to low fluid temperature as a result, sub-zero fluid temperature may occur and dry ice may form if there is indeed water component present in the fluid stream. Furthermore, excessive Joule-Thomson cooling may result in pipeline temperature s falling below its material limit, and thus introduce undesired risk to pipeline integrity. 

In order to assess dry ice-forming potential and mitigate pipeline integrity risk, a simplified fluid flow problem as illustrated in Figure 13 has been developed, transient multiphase flow models (OLGA) built and applied to investigate the Joule-Thomson cooling effects. 

Due to Joule-Thomson cooling associated with pressure drop upon CO2 pipeline packing, significant drop in the CO2 temperature has been observed, which could potentially lead to fluid temperature drop well below zero (as low as -60 °C) over seconds for downstream pipeline. 

In the unfortunate events of water present in the supercritical CO2 fluid stream, CO2 hydrate and/or dry ice may briefly form as a result of Joule-Thomson cooling. The CO2 packing procedure may need to be revisited and modified to prevent the undesired circumstances from happening. 

Luckily, the pipeline wall temperature, both at the inner side and the outer side, is much higher than the CO2 fluid temperature and sits above the material design limit (e.g., -20 °C). Therefore, the Joule-Thomson cooling should not pose substantial risk to pipeline integrity. 

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