Method for starting up a cryogenic air separation unit and associated air separation unit
AssigneeL'Air Liquide, Societe Anonyme pour I'Etude et I'Exploitation des Procedes Georges Claude
InventorsEric Day, Fei Gao, Huali Xie
Life of this patent
Estimating the term…
Abstract
In a process for starting up an air separation unit, which is at a temperature of above 0° C., the air separation unit comprising a main air compressor for compressing the feed air, a booster driven by a turbine and a venting conduit connected downstream of the booster and upstream of the main heat exchanger wherein in order to start up the air separation unit, once the turbine is operating at said given speed, the venting conduit is opened to send at least part of the air compressed in the booster from the booster outlet to the atmosphere.
Claims9
A process for starting up an air separation unit which is at a temperature of above 0° C., the air separation unit comprising:
- a main air compressor for compressing a feed air,
- a main heat exchanger,
- a conduit for sending compressed air from the main air compressor to the main heat exchanger to be cooled,
- a booster,
- a conduit for sending at least part of the compressed air cooled in the main heat exchanger to the booster,
- means for sending air to the main heat exchanger from the booster, there being no means for cooling the air downstream of the booster and upstream of the main heat exchanger,
- a column system,
- at least one turbine connected to receive compressed air from the main air compressor, the at least one turbine being connected to the column system to provide air to be distilled in the column system,
- a conduit for removing an oxygen enriched product from the column system and sending the oxygen enriched product to be warmed in the main heat exchanger,
- a conduit for removing a nitrogen enriched product from the column system and sending the nitrogen enriched product to be warmed in the main heat exchanger;
- wherein, during normal operation, the air separation unit is configured such that air is sent from the main air compressor to the main heat exchanger, cooled in the main heat exchanger, compressed in the booster, cooled in the main heat exchanger and separated in the column system, air is sent from the main heat exchanger, expanded in the turbine and separated in the column system, and the nitrogen enriched product and the oxygen enriched product are warmed in the main heat exchanger;
- wherein the air separation unit comprises a venting conduit connected downstream of the booster and upstream of the main heat exchanger, inlet;
- wherein, during start-up of the air separation unit, the method comprises the steps of:
- i) compressing air in the main air compressor and then sending said air to a booster inlet;
- ii) sending air to a turbine inlet;
- and
- iii) biasing the venting conduit to a closed position before the turbine is operating at a given fraction of its critical speed, and once the turbine is operating at said given fraction or above, opening the venting conduit to send at least part of the air compressed in the booster from a booster outlet to an atmosphere.
Dependencies are inferred from the claim text.