Air separation power generation integration

Patent metadata

Field	Value
Publication number	US-9680350-B2
Application number	US-201214119087-A
Country	US
Kind code	B2
Filing date	May 23, 2012
Priority date	May 26, 2011
Publication date	Jun 13, 2017
Grant date	Jun 13, 2017

Abstract

The present invention provides a method and apparatus for separating air and generating electrical power. A compressed air stream produced in a main air compressor is introduced into an air separation unit that cryogenically rectifies the air into component products. During turndown conditions of the air separation unit, a combustion air stream formed from all or part of the compressed air stream is introduced into a combustor in which a fuel is combusted to produce a heated and pressurized combustion stream. Such stream is introduced to a turbine connected to an electrical generator to generate electrical power. The combustion air stream can be saturated with moisture to increase power output. Further, the combustion air stream can also be preheated with an exhaust of a gas turbine.

First claim

We claim:

1. A method of separating air and generating electrical power comprising:
compressing the air in a main air compressor to produce a compressed air stream;
forming a combustion air stream from at least part of the compressed air stream;
during design operational conditions, introducing the compressed air stream into an air separation unit and separating the air through cryogenic rectification to produce one or more products;
during turn-down operational conditions where the one or more products are not being produced or being produced at a lesser rate, introducing the combustion air stream and a fuel stream into a combustor, combusting the fuel to produce a heated and pressurized combustion stream and expanding the heated and pressurized combustion stream in a turbine connected to an electrical generator to generate electrical power;
operating the main air compressor such that the compressor produces the compressed air stream to allow the combustion air stream to be available during the turn-down operational conditions to support combustion of the fuel stream for generation of the electrical power;
wherein the turbine produces an exhaust stream and the exhaust stream indirectly transfers heat to the combustion air stream prior to the introducing the combustion air stream into the combustor;
the combustion air stream is saturated with moisture prior to the exhaust stream indirectly transferring heat to the combustion air stream
wherein the combustion air stream is saturated with moisture by:
condensing a steam stream in a condenser to produce a condensed stream;
pumping the condensed stream in a pump to produce a first pressurized water stream;
combining the first pressurized water stream with a second pressurized water stream to produce a combined water stream;
heating the combined water stream in the condenser through indirect heat exchange with the steam stream to produce a heated water stream;
counter-currently contacting the heated water stream with the combustion air stream in a saturator to produce the combustion air stream saturated with the moisture and a bottoms liquid; and
recirculating at least part of the bottoms liquid to form the second pressurized water stream.

2. The method of claim 1 , wherein the combustion air stream is saturated with moisture by:
pumping a water stream in a pump to produce a pressurized water stream;
heating the pressurized water stream with the exhaust stream in a water heater positioned between the turbine and a recuperator used in the indirect heat transfer from the exhaust stream to the combustion air stream to at least in part produce a heated water stream;
counter-currently contacting the heated water stream with the combustion air stream in a saturator to produce the combustion air stream saturated with the moisture and a bottoms liquid; and
forming the water stream by combining the bottoms liquid with a make-up water stream.

3. The method of claim 1 , wherein the combustion air stream is saturated with moisture by:
pumping a water stream composed of bottoms liquid of a saturator in a pump to produce a pressurized water stream;
heating the pressurized water stream with the exhaust stream in a water heater positioned between the turbine and a recuperator used in the indirect heat transfer from the exhaust stream to the combustion air stream;
pumping a boiler feed water stream and combining the boiler feed water stream with the pressurized water stream after having been heated in the water heater to form a heated water stream; and
counter-currently contacting the heated water stream with the combustion air stream in the saturator to produce the combustion air stream saturated with the moisture and the bottoms liquid.

4. The method of claim 1 , wherein:
the combustion air stream is saturated with moisture by:
pumping a water stream in a pump to produce a pressurized water stream;
heating the pressurized water stream with the exhaust stream in a water heater to produce a heated water stream;
forming the combustion air stream by further compressing the at least part of the compressed air stream in a booster compressor;
counter-currently contacting the heated water stream with the combustion air stream in a saturator to produce the combustion air stream saturated with the moisture and a bottoms liquid; and
forming the water stream at least in part from the bottoms liquid; and

heating the combustion air stream after having been saturated by moisture through indirect heat exchange with a gas turbine exhaust used to generate additional electrical power.

5. The method of claim 1 , wherein:
the combustor is a combustor of a gas turbine and the expander is an expander of the gas turbine; and
the combustion air stream is further compressed and introduced into the combustor.

6. An apparatus for separating air and generating electrical power comprising:
a main air compressor to compress air and thereby to produce a compressed air stream;
an air separation unit in flow communication with the main air compressor;
the air separation unit configured to selectively operate in a design operational condition and a turn-down operational condition such that during the design operational condition the air within the compressed air stream is separated through cryogenic rectification to produce one or more products and during the turn-down operational condition, the one or more products are not being produced or being produced at a lesser rate than during design operational conditions;
means for producing a combustion air stream from at least part of the compressed air stream;
a combustor in flow communication with combustion air stream producing means such that during the turn-down operation condition, a fuel stream is combusted in the combustor through combustion supported by the combustion air stream and a heated and pressurized combustion stream is produced from the combustion;
a turbine in flow communication with the combustor to expand the heated and pressurized combustion stream to produce an exhaust stream;
an electrical generator connected to the turbine to generate the electrical power;
the main air compressor having sufficient capacity to allow the combustion air stream to be available during the turn-down operational condition to support combustion of the fuel stream for generation of the electrical power;
wherein a recuperator is positioned between the turbine and the main air compressor such that an exhaust stream produced by turbine indirectly transfers heat to the combustion air stream prior to introduction of the combustion air stream into the combustor;
a means for adding moisture to the combustion air stream is positioned between the recuperator and the main air compressor such that the combustion air stream contains moisture prior to the exhaust stream indirectly transferring heat to the combustion air stream;
wherein the means for adding moisture comprises:
a condenser for condensing a steam stream in a condenser to produce a condensed stream;
a pump connected to the condenser to pump the condensed stream and thereby to produce a first pressurized water stream;
a saturator configured to counter-currently contacting a heated water stream with the combustion air stream to produce the combustion air stream with moisture and a bottoms liquid; and
a recirculation flow path connected to the pump, the condenser and the saturator and configured to combine the first pressurized water stream with a second pressurized water stream to produce a combined water stream, to heat the combined water stream in the condenser through indirect heat exchange with the steam stream to produce the heated water stream and having a recirculation pump positioned to recirculate at least part of the bottoms liquid to form

Assignees

• Panuccio Gregory Joseph
• Drnevich Raymond Francis
• Shah Minish Mahendra
• Praxair Technology Inc

Inventors

• Panuccio Gregory Joseph
• Drnevich Raymond Francis
• Shah Minish Mahendra

Classifications

• F25J3/04836 Primary

  Variable air feed, i.e. "load" or product demand during specified periods, e.g. during periods with high respectively low power costs (F25J3/0483 takes precedence) · CPC title

• H02K7/1823 Primary

  structurally associated with turbines or similar engines · CPC title

• F02C3/20

  using a special fuel, oxidant, or dilution fluid to generate the combustion products · CPC title

• F02C6/06

  providing compressed gas (F02C6/10 takes precedence) · CPC title

• F25J2240/82

  with waste heat recovery, e.g. in a combined cycle, i.e. for generating steam used in a Rankine cycle · CPC title