Joule-Thomson

Joule-Thomson effect, Joule-Kelvin effect... 

If high wellhead pressures are available over long periods, cooling can be achieved by expanding gas through a valve, a process known as Joule Thomson (JT) throttling. The valve is normally used in combination with a liquid gas separator and a heat exchanger, and inhibition measures must be taken to avoid hydrate formation. The whole process is often termed low temperature separation (LTS). 

HTS SQUID System with Joule-Thomson Cryocooler for Eddy Current Nondestructive... 

At constant pressure L Joule-Thomson coefficient fX, fXjT-... 

To convert the Joule-Thomson coefficient, I, in degrees Celsius per atmosphere to degrees Fahrenheit per atmosphere, multiply by 1.8. 

TABLE 2-149 Additional References Available for the Joule-Thomson Coefficient... 

TABLE 2-155 Joule-Thomson Data for Carbon Dioxide ... 

Expanders The primary function of cryogenic expansion equipment is the reduction of the temperature of the gas being expanded to provide needed refrigeration. The expansion of a fluid to produce refrigeration may be carried out in two distinct ways (1) in an expander where mechanical work is produced, and (2) in a Joule-Thomson valve where no work is produced. 

Jotile-Thomson Valves The principal function of a J-T valve is to obtain isenthalpic coohng of the gas flowing through the valve. These valves generally are needle-type valves modified for cryogenic operation. They are an important component in most refrigeration systems, particularly in the last stage of the liquefac tion process. Joule-Thomson valves also offer an attractive alternative to turboexpanders for small-scale gas-recovery applications. 

Older proeesses used Joule-Thomson eooling entirely. The Joule-Thomson effeet is defined as the eooling that oeeurs when a highly eompressed gas is allowed to expand in sueh a way that no external work is done. This eooling is inversely proportional to the square of the absolute temperature. The system worked satisfaetorily, but it required mueh higher pressures to remove the same amount of energy. 

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. 

In summary, starting with 105°F gas at atmospheric pressure, the theoretical work necessary to liquify one pound of methane is 510.8 Btu or 352 hp/MMcfd. The simplified liquefaction process, as illustrated, uses a turboexpander/compressor and a small propane refrigeration unit. The 41.25% efficiency breaks down as follows one-fourth contributed by the turboexpander/compressor at 35.8% efficiency one-sixteenth contributed by the mechanical propane refrigeration unit at 43% efficiency, at a moderate temperature where its efficiency is high and a large fraction—eleven-sixteenths—contributed at 58.2% efficiency by compression and Joule-Thomson condensation energy. 

Hydroearbon dew point eontrol is aehieved by eooling the gas. There are three eooling alternatives free expansion or Joule-Thomson expansion, external refrigeration, and using a turboexpander. Joule-Thomson expansion does not always produee the needed refrigeration over the life of the plant and, henee, is not eonsidered as a viable... 

Option 1 Initial Installation—Joule-Thomson Expansion... 

The turboexpander lowers the temperature of the product to -100°F, causing it to liquify. Now at 350 psig pressure, the liquid from this process enters the demethanizer tower where it mingles with the previously introduced stream of liquid. The turboexpanders provide a 92% recovery rate while the former system, a backup Joule-Thomson valve, was able to provide only a 60% recovery rate. The volume of gas entering the turboexpanders can vary up to 10% yet, the different flowrates do not significantly affect the efficiency of these units, which are rated at 2,400 hp at 16,000 rpm. 

Figure 3.5 In the Joule-Thomson expansion, a volume of gas V, is pushed through a porous plug by a piston at pressure pt. The gas expands to a volume V2 against a second piston at a pressure p2.

Thus, the Joule-Thomson expansion is an isenthalpic process. 

Figure 3.6 shows how pressure and temperature are related for a series of isenthalpic (Joule-Thomson) expansions. For example, if we start at the... 

Since the Joule-Thomson process is isenthalpic, the slope of each line can be represented as (dT/dp)lf. This quantity is referred to as the Joule Thomson coefficient, pj j.. Thus1... 

---