For producing atmospheric gases like oxygen, nitrogen and argon in large scale, low temperature distillation provides the most economical route from many points of view. In addition, many industrially important physical processes require very low temperature in the form of cryogenic distillation. Such cryogenic process plants are exclusively based on the low-pressure cycles for which an expansion turbine to generate refrigeration is an essential part of the plant.
Turbo-expanders are highly engineered products, which are always built according to the process requirements as well as to the customers’ specifications.
Turbo-expander packages are characterized into three distinct application categories:
NirvaTech offers a wide range of turbo-expander packages to API-617 through reputable world-class turbo-expander manufacturers as follows:
| Size | Power (KW) | Expander Inlet Flow (m3/h) | ||
| Min | Max | Min | Max | |
| 10-40 | 50 | 400 | 100 | 150 |
| 20-70 | 400 | 700 | 150 | 550 |
| 30-160 | 800 | 1,600 | 550 | 3,400 |
| 40-340 | 1,600 | 3,400 | 1,200 | 6,700 |
| 50-660 | 2,700 | 6,600 | 6,700 | 13,600 |
In a Gas Processing Plant, the purpose of the Turboexpander is to efficiently perform two distinctly different, but complimentary, functions in a single machine. The primary function is to efficiently generate refrigeration in the process gas stream, which is performed by the Expansion Turbine end efficiently extracting the potential heat energy from the gas stream, causing it to cool dramatically. This extracted energy can then be converted to mechanical energy to rotate the Shaft to the Booster Compressor end of the Turboexpander, which partially recompresses the residue gas stream. The Turboexpander operates according to the thermodynamic and aerodynamic laws of physics. When designed properly, the Turboexpander can yield very high efficiencies at the "Design Point" and reasonable efficiencies at other, or "Off-Design", Points. Hence, requiring an state-of-the-art design, to take place in order to overcome various process and mechanical constraints.
All above indicated sizes can be combined with a booster compressor to form a turbo-expander / compressor package.
The energy extracted from a gas expanding across the turbine can be converted into electric power by connecting the load side of the expander shaft to a generator. The Expander/Generator arrangement is typically available in following three configurations:
In most cases, the operating speed of the expander will be at a higher RPM than the operating speed of the generator. It is therefore necessary to utilize a speed reduction gearbox to facilitate appropriate coupling speed.
In one such configuration, the high speed expander shaft is connected to a high speed coupling that transmits the torque to a speed reduction gearbox. The gearbox is then coupled to the generator. This configuration is typically used in medium to high power applications.
In most cases, the operating speed of the expander will be at a higher RPM than the operating speed of the generator. It is therefore necessary to utilize a speed reduction gearbox to facilitate appropriate coupling speed.
In another such configuration, the expander wheel is directly mounted on a shaft that also serves as the high-speed gearbox pinion eliminating the high-speed coupling. As with the Expander/Coupling/Gearbox/Generator, this configuration is also used in medium to high power applications.
In a third configuration, the expander wheel is directly mounted on a shaft that also serves as the high-speed generator’s shaft, eliminating the gearbox entirely. This configuration is limited to the power capacity of high-speed generators and is typically used in low to medium power applications.
The sizes 30-160 to 50-660 as indicated above can be combined with an alternator to form a turbo-expander / generator package.
In some applications, an expander is used to achieve maximum refrigeration in a low-flow process stream. The potential energy recovered from the gas expansion is not sufficient to justify the investment of an attached generator, or it may not be feasible to attach a booster compressor. In this situation, the energy is absorbed by a dynamometer wheel rotating in a liquid system. A dynamometer is sometimes referred to as a brake. The dynamometer dissipates the energy into the liquid through a pumping action. The liquid is normally contained in a closed loop system that incorporates a cooler to keep the liquid at a predictable viscosity. Both Oil or Hydraulic systems are available.
The sizes 10-40 and 20-70 as indicated above can be combined with a dynamometer to form a turbo-expander / generator package.
