Controlled Freeze Zone™ is an efficient single-step cryogenic distillation process for the removal of carbon dioxide, hydrogen sulfide and other impurities from natural gas. Rather than avoiding the freezing of CO2 at cryogenic temperatures, the solidification is allowed to take place, albeit in a very controlled fashion. The technology has shown the potential to more efficiently and cost-effectively separate carbon dioxide and other impurities from natural gas, and to discharge these contaminants as a high-pressure liquid stream ready for underground injection, either for enhanced oil recovery applications or for acid gas injection disposal.
Natural gas is the cleanest burning hydrocarbon fuel available and its growing demand is only projected to rise throughout this century. ExxonMobil anticipates total global energy demand to grow 35% by 2040 relative to 20101. Greater demand for electricity accounts for more than half of this increase. The clean burning characteristics of natural gas and its increasingly competitive economics for power generation are driving its expanded use in electrical power generation. Natural gas emits up to 60 percent less CO2 than coal when generating electricity, which becomes quite significant as costs arising from greenhouse gas policies mount. ExxonMobil forecasts natural gas to emerge as the leading source of electricity generation by 2040, and to become the second largest global fuel by 2040 behind oil, displacing coal from the second spot.
Meeting such a growth in demand will require a significant increase in gas production. New resources will be developed, many of them containing substantial amounts of CO2 and H2S that must be properly managed once brought up to the surface along with the produced hydrocarbons. Returning them to the sub-surface for geosequestration or using them in enhanced oil-recovery is emerging as a preferred option in their management and disposal. Commercial application of a technology like the ExxonMobil Controlled Freeze Zone (CFZ™) process can help meet that goal at a significantly lower cost than other competing technologies available today.
When acid gas injection is called for in the processing of sour gas resources, the relative advantages of the various types of treatment processes shifts towards options that release the acid gases, removed from the natural gas, at a relatively high pressure, and especially as a liquid. Natural gas fractionation can be designed to recover the acid gases at high pressure and at least partially in some cases as a liquid. This minimizes the power required for compression or pumping for reinjection of the waste acid gases.
