NATURAL GAS COMBINED POWER GENERATION PROCESS WITH ZERO CARBON EMISSION

Abstract

The present disclosure relates to the technical field of natural gas power generation, and particularly discloses a natural gas combined power generation process with zero carbon emission, the process comprising: introducing the pressurized air into an air separation facility to obtain liquid oxygen and liquid nitrogen, wherein the liquid oxygen is used for gasification and power generation, the liquid nitrogen is applied as the coolant of flue gas, and then used for the gasification and power generation; the liquid nitrogen and a part of liquid oxygen stored during the valley period with low electricity load are provided for use during the peak period with high electricity load; the natural gas, oxygen and the recyclable CO.sub.2 jointly enter a combustion gas turbine for burning to drive an air compressor and a generator to rotate at a high speed, the air compressor compresses the air to a pressure of 0.40.8 MPa, the generator generates electricity; the high-temperature combustion flue gas performs the supercritical CO.sub.2 power generation, its coolant is liquid oxygen; the moderate temperature flue gas then exchanges heat with liquid nitrogen, the liquid nitrogen vaporizes for power generation, the cooled flue gas is dehydrated and subjects to distillation and separation to obtain the recovered CO.sub.2, a part of the CO.sub.2 can be returned for circulation and temperature control, another part of the CO.sub.2 may be used for replenishment of work medium for supercritical CO.sub.2 power generation, and the remaining part of CO.sub.2 may be sold outward as liquid CO.sub.2 product. During the peak period with high electricity load, the liquid nitrogen stored during the valley period with low electricity load and separated during the peak period is pumped and pressurized and then subjects to heat exchange and vaporization for power generation. The power generation process provided by the present disclosure not only solves the difficult problems in the existing natural gas combined power generation technology such as high water consumption, low power generation efficiency and small range of peak load adjustment capacity; but also can compress air with high unit volume for energy storage with a high conversion efficiency, and greatly reduce load of the air compressor, thereby perform CO.sub.2 capture and utilization with low cost, zero NO.sub.x emission and discharging fuel gas at a normal temperature, and significantly improve the power generation efficiency.

Claims

1. A natural gas combined power generation process with zero carbon emission, the process comprising: 1) pressurizing the air with an air compressor to a pressure of 0.40.8 MPa, and then introducing the pressurized air into an air separation facility for performing air separation to obtain liquid oxygen and liquid nitrogen; 2) performing heat exchange at a cooler between the liquid oxygen and the high-temperature CO.sub.2 at an outlet of a supercritical CO.sub.2 generator, so as to generate high-pressure vaporized oxygen and recyclable CO.sub.2; 3) combusting the high-pressure vaporized oxygen and natural gas, and the obtained high-temperature combustion flue gas drives an air compressor and a generator to generate electricity; 4) subjecting the high-temperature combustion flue gas obtained in step 3) to a heat exchange in a CO.sub.2 waste heat boiler to perform a supercritical CO.sub.2 power generation; 5) performing heat exchange of the heat exchanged combustion flue gas obtained in step 4) with liquid nitrogen through a vaporizer, and the vaporization of liquid nitrogen drives a nitrogen turbine generator to generate electricity.

2. The natural gas combined power generation process with zero carbon emission according to claim 1, wherein the stepwise cooled flue gas obtained in step 5) is dehydrated, and the dehydrated flue gas is pumped to a flue gas distillation tower to separate and recover CO.sub.2.

3. The natural gas combined power generation process with zero carbon emission according to claim 2, wherein at least a part of the recovered CO.sub.2 is recycled to the step 3) for combustion along with the high-pressure vaporized oxygen and natural gas.

4. The natural gas combined power generation process with zero carbon emission according to claim 3, wherein the mass ratio of the high-pressure vaporized oxygen relative to the recovered CO.sub.2 recycled to step 3) is 1: (212).

5. The natural gas combined power generation process with zero carbon emission according to claim 4, wherein the mass ratio of the high-pressure vaporized oxygen relative to the recovered CO.sub.2 recycled to step 3) is 1: (58).

6. The natural gas combined power generation process with zero carbon emission according to claim 2, wherein at least a part of the recovered CO.sub.2 is used in replenishment of working medium for supercritical CO.sub.2 power generation.

7. The natural gas combined power generation process with zero carbon emission according to claim 1, wherein the air separation is a cryogenic air separation, a cascade air separation combined with pressure swing adsorption separation and cryogenic separation or a cascade air separation combined with membrane separation and cryogenic separation.

8. The natural gas combined power generation process with zero carbon emission according to claim 1, wherein the supercritical CO.sub.2 power generation is one of a supercritical CO.sub.2 power generation mode of a recompression cycle, a segment expansion cycle, a preload cycle, and a partial cooling cycle.

9. The natural gas combined power generation process with zero carbon emission according to claim 1, wherein the supercritical CO.sub.2 power generation comprises: supercritical CO.sub.2 is pressurized by a CO.sub.2 compressor, and then performs heat exchange in a CO.sub.2 waste heat boiler with the high-temperature combustion flue gas obtained in step 3); the heat exchanged working medium enters the supercritical CO.sub.2 generator for performing the supercritical CO.sub.2 power generation; the high-temperature CO.sub.2 at an outlet of the supercritical CO.sub.2 generator performs heat exchange in the cooler with the liquid oxygen, and the obtained recyclable CO.sub.2 is delivered to the CO.sub.2 compressor.

10. The natural gas combined power generation process with zero carbon emission according to claim 9, wherein the supercritical CO.sub.2 pressure is within a range of 740 MPa.

11. The natural gas combined power generation process with zero carbon emission according to claim 9, wherein the supercritical CO.sub.2 pressure is within a range of 1225 MPa.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The drawings provide reference to facilitate further understanding of the present disclosure, and constitute a part of the description, it serves to illustrate the present disclosure along with the following specific embodiments, but the drawings do not impose limitation on the present disclosure. In the drawings:

[0012] FIG. 1 is a schematic diagram of a natural gas combined power generation process with zero carbon emission according to a specific embodiment of the present disclosure.

DESCRIPTION OF THE REFERENCE SIGNS

[0013]

TABLE-US-00001 1. air separation 2. natural gas pressure tank 3. air compressor facility 4. CO.sub.2 waste heat 5. generator 6. cooler boiler 7. CO.sub.2 compressor 8. supercritical CO.sub.2 9. combustion gas generator turbine 10. vaporizer 11. nitrogen turbine 12. flue gas distillation generator tower

DETAILED DESCRIPTION

[0014] The terminals and any value of the ranges disclosed herein are not limited to the precise ranges or values, such ranges or values shall be comprehended as comprising the values adjacent to the ranges or values. As for numerical ranges, the endpoint values of the various ranges, the endpoint values and the individual point value of the various ranges, and the individual point values may be combined with one another to produce one or more new numerical ranges, which should be deemed have been specifically disclosed herein.

[0015] As illustrated in FIG. 1, the present disclosure provides a natural gas combined power generation process with zero carbon emission, the process comprising:

1) pressurizing the air with an air compressor to a pressure of 0.40.8 MPa, and then introducing the pressurized air into an air separation facility for performing air separation to obtain liquid oxygen and liquid nitrogen;
2) performing heat exchange at a cooler between the liquid oxygen and the high-temperature CO.sub.2 at an outlet of a supercritical CO.sub.2 generator, so as to generate high-pressure vaporized oxygen and recyclable CO.sub.2;
3) combusting the high-pressure vaporized oxygen and natural gas, and the obtained high-temperature combustion flue gas drives an air compressor and a generator to generate electricity;
4) subjecting the high-temperature combustion flue gas obtained in step 3) to a heat exchange in a CO.sub.2 waste heat boiler to perform a supercritical CO.sub.2 power generation;
5) performing heat exchange of the heat exchanged combustion flue gas obtained in step 4) with liquid nitrogen through a vaporizer, and the vaporization of liquid nitrogen drives a nitrogen turbine generator to generate electricity.

[0016] The power generation process provided by the present disclosure does not require to pressurize air to a pressure of 2.8 MPa, which reduces energy consumption. Specifically, the air compressor may be an axial flow air compressor, and in step 1) the air compressor inhales air from the external atmospheric environment and pressurizes the air with a stepwise compression process by a an axial air compressor to a pressure of 0.40.8 MPa. At the same time, the air temperature is also increased accordingly for preheating liquid oxygen.

[0017] According to the present disclosure, the air separation is preferably a cryogenic air separation, a cascade air separation combined with pressure swing adsorption separation and cryogenic separation or a cascade air separation combined with membrane separation and cryogenic separation. The specific operation of the air separation may be carried out according to the conventional techniques in the art, and the present disclosure is not particularly limited thereto. The pressurized liquid oxygen is pumped for heat exchange and cooling of the supercritical CO.sub.2 power generation, and the liquid oxygen exchanges heat in the cooler with the high-temperature CO.sub.2 at the supercritical CO.sub.2 generator outlet for the supercritical CO.sub.2 power generation, so as to obtain the high-pressure vaporized oxygen and recyclable CO.sub.2. The high-pressure vaporized oxygen is used for natural gas power generation, that is, the high-pressure vaporized oxygen and natural gas are combusting, and the obtained high-temperature combustion flue gas drives the air compressor and the generator to generate electricity.

[0018] The supercritical CO.sub.2 power generation according to the present disclosure may be a variety of power generation modes conventionally used in the art, preferably, the supercritical CO.sub.2 power generation is one of a supercritical CO.sub.2 power generation mode of a recompression cycle, a segment expansion cycle, a preload cycle, and a partial cooling cycle.

[0019] According to the present disclosure, subjecting the high-temperature combustion flue gas obtained in step 3) to a heat exchange in a CO.sub.2 waste heat boiler to perform a supercritical CO.sub.2 power generation particularly refers to that the supercritical CO.sub.2 pressurized by the CO.sub.2 compressor exchanges heat in a CO.sub.2 waste heat boiler with the high-temperature combustion flue gas obtained in step 3), the heat exchanged working medium enters the supercritical CO.sub.2 generator for performing supercritical CO.sub.2 power generation.

[0020] According to a preferred embodiment of the present disclosure, the supercritical CO.sub.2 power generation comprises: supercritical CO.sub.2 is pressurized by a CO.sub.2 compressor, and then performs heat exchange in a CO.sub.2 waste heat boiler with the high-temperature combustion flue gas obtained in step 3); the heat exchanged working medium enters the supercritical CO.sub.2 generator for performing the supercritical CO.sub.2 power generation; the high-temperature CO.sub.2 at an outlet of the supercritical CO.sub.2 generator performs heat exchange in the cooler with the liquid oxygen, and the obtained recyclable CO.sub.2 is delivered to the CO.sub.2 compressor.

[0021] According to the power generation process provided by the present disclosure, preferably, the supercritical CO.sub.2 pressure is within a range of 740 MPa, and further preferably, the supercritical CO.sub.2 pressure is within a range of 1225 MPa.

[0022] In the power generation process provided by the present disclosure, the liquid oxygen may be used as a coolant in the supercritical CO.sub.2 power generation process, and may be used for natural gas power generation after heat exchange, the obtained high-temperature combustion flue gas exchanges heat in a CO.sub.2 waste heat boiler with the CO.sub.2 pressurized by a CO.sub.2 compressor, so as to provide heat to the CO.sub.2 pressurized by the CO.sub.2 compressor, and the heat exchanged working medium enters the supercritical CO.sub.2 generator for performing supercritical CO.sub.2 power generation. The power generation process provided by the present disclosure can realize efficient utilization of energy and save energy.

[0023] According to the present disclosure, the liquid nitrogen obtained in step 1) may be stored during the valley period with low electricity load (e.g., at nighttime), and then during the peak period with high electricity load (e.g., in the daytime), the heat exchange of the heat exchanged combustion flue gas obtained in step 4) with the liquid nitrogen may be performed through a vaporizer, the vaporization of liquid nitrogen drives a nitrogen turbine generator to generate electricity. The power generation process provided by the present disclosure can perform peak shaving and power generation.

[0024] According to a preferred embodiment of the present disclosure, the stepwise cooled flue gas obtained in step 5) is dehydrated, and the dehydrated flue gas is pumped to a flue gas distillation tower to separate and recover CO.sub.2. The stepwise cooled flue gas refers to that the flue gas obtained from the high-temperature combustion flue gas which performs heat exchange (first level cooling) in the CO.sub.2 waste heat boiler, and the heat exchanged flue gas then perform heat exchange in a vaporizer with the liquid nitrogen (second level cooling). The present disclosure does not impose a specific definition on the dehydration mode, the dehydration may be carried out according to a variety of technical means conventionally used in the art.

[0025] According to a specific embodiment of the present disclosure, in step 3), the high-pressure vaporized oxygen and the natural gas jointly enter the combustion gas turbine, the obtained high-temperature combustion flue gas enters the turbine, so as to drive the turbine to move the air compressor and the generator to generate electricity.

[0026] According to a preferred embodiment of the present disclosure, at least a part of the recovered CO.sub.2 is recycled to the step 3) for combustion along with the high-pressure vaporized oxygen and natural gas. At least a part of the recovered CO.sub.2 is returned to the combustion gas turbine as a feed material for circulation and temperature control.

[0027] According to a preferred embodiment of the present disclosure, the mass ratio of the high-pressure vaporized oxygen relative to the recovered CO.sub.2 recycled to step 3) is 1: (212), further preferably 1: (58).

[0028] According to a preferred embodiment of the present disclosure, at least a part of recovered CO.sub.2 is used in replenishment of working medium for supercritical CO.sub.2 power generation. The present disclosure does not impose a specific limitation on the specific amount of recovered CO.sub.2 used in the supercritical CO.sub.2 power generation for the replenishment of the working medium and the skilled person in the art may appropriately select it according to the specific operation conditions.

[0029] The recovered CO.sub.2 can also be sold outward as a liquid CO.sub.2 product.

[0030] According to a specific embodiment of the present disclosure, the natural gas combined power generation process with zero carbon emission provided by the present disclosure comprises: an air compressor inhales air from an external atmospheric environment, and pressurizes the air with a stepwise compression process by an axial air compressor to a pressure of 0.40.8 MPa, and the air temperature is increased accordingly for preheating liquid oxygen; the pressurized air with a pressure of 0.40.8 MPa is introduced into an air separation facility for performing air separation to obtain liquid oxygen and liquid nitrogen; the pressurized liquid oxygen is pumped for performing heat exchange with the supercritical CO.sub.2 and cooling and power generation, the pressurized liquid nitrogen is pumped as a flue gas coolant for performing heat exchange, then vaporization and power generation, the liquid nitrogen and a part of liquid oxygen separated at night are supplied for use during a peak period with high electricity load in the daytime; the high-pressure vaporized oxygen subjects to heat exchange through a supercritical CO.sub.2 cooler, and then blends with high-pressure recyclable CO.sub.2 and the injected natural gas for combustion, the high-temperature combustion flue gas then enters a turbine to swell and work, drives the turbine to rotate the air compressor and the generator at high speed, performs the partial conversion of the chemical energy of the natural gas into mechanical work, and outputs the electrical work; the high-temperature combustion flue gas then performs heat exchange in the CO.sub.2 waste heat boiler to carry out the supercritical CO.sub.2 power generation, its coolant is pressurized liquid oxygen, the cooled supercritical CO.sub.2 circulates through a CO.sub.2 compressor; the heat exchanged flue gas performs heat exchange with pressurized liquid nitrogen, the liquid nitrogen is vaporized to drive a nitrogen turbine generator to generate electricity, the stepwise cooled flue gas is dehydrated, the liquid flue gas passes through a distillation tower to separate and recover CO.sub.2, a part of CO.sub.2 returns to the combustion gas turbine as a feed material for circulation and temperature control, another part of CO.sub.2 is used for replenishment of work medium for performing supercritical CO.sub.2 power generation, and a remaining part of CO.sub.2 is sold outward as liquid CO.sub.2 product; during a peak period of high electricity load in the daytime, the liquid nitrogen stored at night and separated in the daytime is pumped and pressurized, and then exchanges heat and vaporizes for power generation, the liquid oxygen stored at night and separated in the daytime is pumped and pressurized, and subsequently exchanges heat and vaporizes for use in a combustion gas turbine to perform peak shaving and power generation in response to the load fluctuation.

[0031] The present disclosure will be described in detail below with reference to examples.

EXAMPLE 1

[0032] 1) As shown in FIG. 1, an air compressor inhales air from an external atmospheric environment, and pressurizes the air with a stepwise compression process by an air compressor (3) to a pressure of 0.40.8 MPa, and the air temperature is increased accordingly for preheating liquid oxygen; the pressurized air with a pressure of 0.40.8 MPa is introduced into an air separation facility (1) for performing air separation to obtain liquid oxygen and liquid nitrogen. The liquid oxygen is used for performing heat exchange and cooling of the supercritical CO.sub.2 and power generation, the liquid oxygen exchanges heat in a cooler (6) with the high-temperature CO.sub.2 at an outlet of the supercritical CO.sub.2 generator (8) performing the supercritical CO.sub.2 power generation, so as to obtain the high-pressure vaporized oxygen and the recyclable CO.sub.2, the coolant in the cooler (6) is liquid oxygen; the high-pressure vaporized oxygen and the natural gas jointly enter the combustion gas turbine (9) for performing combustion, the obtained high-temperature combustion flue gas enters a turbine to drive the air compressor (3) and a generator (5) to rotate at a high speed, performs the partial conversion of the chemical energy of the natural gas into mechanical work, and outputs the electrical work. The high-temperature combustion flue gas obtained from the combustion of the high-pressure vaporized oxygen and the natural gas subsequently performs heat exchange in a CO.sub.2 waste heat boiler (4) to carry out the supercritical CO.sub.2 power generation.

[0033] The supercritical CO.sub.2 power generation includes: the supercritical CO.sub.2 is pressurized by a CO.sub.2 compressor (7), and then exchanges heat in the CO.sub.2 waste heat boiler (4) with the high-temperature combustion flue gas obtained above; the heat exchanged working medium enters the supercritical CO.sub.2 generator (8) to perform the supercritical CO.sub.2 power generation; the high-temperature CO.sub.2 at the outlet of the supercritical CO.sub.2 generator (8) and the liquid oxygen perform heat exchange in a cooler (6) for supercritical CO.sub.2 power generation, the obtained recyclable CO.sub.2 is circulated to the CO.sub.2 compressor (7).

[0034] The combustion flue gas following a heat exchange in the CO.sub.2 waste heat boiler (4) performs heat exchange with the above liquid nitrogen through a vaporizer (10), the liquid nitrogen vaporizes to drive a nitrogen turbine generator (11) to generate electricity.

[0035] The stepwise cooled flue gas is dehydrated, and the dehydrated liquid flue gas passes through a flue gas distillation tower (12) to separate and recover CO.sub.2, a part of the recovered CO.sub.2 returns to a combustion gas turbine (9) as a feeding material for circulation and temperature control, another part of the recovered CO.sub.2 is used for replenishment of the working medium for supercritical CO.sub.2 power generation, and a remaining part of the recovered CO.sub.2 is sold outward as a liquid CO.sub.2 product.

[0036] The liquid nitrogen and a part of the liquid oxygen obtained from air separation may be stored during the valley period with low electricity load (e.g., at nighttime) so as to be supplied in use during the peak period with high electricity load in the daytime. Specifically, during the peak period of power grid operation with high electricity load (e.g., in the daytime), the liquid nitrogen stored at nighttime and separated in the daytime may be pumped and pressurized, and then subjects to heat exchange and vaporization in a vaporizer (10) for power generation; the liquid oxygen stored at nighttime and separated in the daytime is pumped and pressurized, and subsequently subjects to heat exchange and vaporization for use in a combustion gas turbine (9) to perform peak shaving and power generation in response to the load fluctuation.

[0037] The natural gas combined power generation process with zero carbon emission provided by the present disclosure can be used for peak shaving and power generation. According to an Aspen simulation result, the power generation process provided by the present disclosure only needs to pressurize the air to a pressure of 0.40.8 MPa, while prior art needs to pressurize the air to a pressure of about 2.8 MPa. The power generation process provided by the present disclosure greatly reduces a ratio of the energy consumption of the natural gas combustion gas turbine for the air compressor from to about 10%; the natural gas and the high-pressure recyclable CO.sub.2 blend with oxygen to assist combustion and power generation, such that the specific volume of the flue gas is increased, and the power generation efficiency of the combustion gas turbine is relatively improved; the combustion flue gas uses supercritical CO.sub.2 for power generation and utilizes the liquid nitrogen vaporization turbine generator for generating electricity thereby form a combined system, the temperature of the exhaust flue gas is reduced from about 140 C. in the prior art to about 30 C., and the energy recovery rate is greatly increased; the flue gas can be easily dehydrated and separated to obtain CO.sub.2, the energy consumption of CO.sub.2 capture is significantly reduced; the problem concerning high water consumption of natural gas power generation is solved due to the CO.sub.2 circulation and temperature control of the combustion gas turbine, the supercritical CO.sub.2 applied as a work medium of waste heat power generation, the dehydration of flue gas at a low temperature and a recyclable utilization of the dehydrated water, thus the process is especially suitable for water-deficient areas; in addition, the oxygen-aided combustion in the combustion gas turbine along with the CO.sub.2 circulation and temperature control avoids the NO.sub.x emission of the existing natural gas power plants, and significantly reduces the emission of smoke dust and SOx, thereby perform a clean and efficient natural gas power generation with zero carbon emission; moreover, the air separation components are respectively utilized, the liquid nitrogen is used for energy storage and peak shaving, the demand of gas storage volume is greatly reduced, the energy consumption derived from the air storage volume requirement is reduced by more than 20 times as compared with the large-scale air compression and energy storage in the prior art, the energy storage efficiency is high, thus satisfying the demand of the peak shaving and valley filling of the natural gas distributed energy power plants in the future.

[0038] The above content describes in detail the preferred embodiments of the present disclosure, but the present disclosure is not limited thereto. A variety of simple modifications can be made to the technical solutions of the present disclosure within the scope of the technical concept of the present disclosure, including a combination of individual technical features in any other suitable manner, such simple modifications and combinations thereof shall also be regarded as the content disclosed by the present disclosure, each of them falls into the protection scope of the present disclosure.