1. A low-nitrogen and rich-carbon combustion process method is characterized by comprising the following steps:

s1, feeding the tail flue gas of the boiler as a high-temperature heat source into a heat pump system for heat exchange;

s2, separating and extracting gaseous or liquid carbon dioxide products from most of low-temperature flue gas discharged from the heat pump system in a carbon capture system;

and a small part of low-temperature flue gas discharged from the heat pump system is mixed with supplementary oxygen and then enters the boiler again for cyclic utilization.

2. The low-nitrogen concentrated carbon combustion process method according to claim 1, wherein the tail flue gas of the boiler is subjected to desulfurization and denitrification by a desulfurization and denitrification device and then enters a heat pump system.

3. The low-nitrogen rich carbon combustion process method as claimed in claim 1, wherein the heat pump system is provided with two exhaust ports, one large exhaust port is used for exhausting most of the low-temperature flue gas, and the other small exhaust port is used for exhausting a small part of the low-temperature flue gas.

4. The low-nitrogen rich carbon combustion process method as claimed in claim 3, wherein a control valve is arranged on the small discharge port, and the control valve is used for opening or closing the small discharge port to release carbon dioxide quantitatively.

5. The low-nitrogen rich carbon combustion process method of claim 1, wherein the S2 specifically comprises: and a small part of low-temperature flue gas discharged from the heat pump system is mixed with supplementary oxygen in the mixing box and then is sent into the boiler through the fan for cyclic utilization.

6. The low-nitrogen rich carbon combustion process method of claim 1, wherein the S2 specifically comprises: the carbon capture system separates and extracts carbon dioxide gas or liquid products by a physical method, wherein the physical method is physical adsorption or a membrane method.

7. The low-nitrogen rich carbon combustion process method of claim 1, wherein the S2 specifically comprises: the carbon capture system separates and extracts carbon dioxide gas or liquid products by a chemical method, wherein the chemical method is a chemical solvent absorption method or a thermal decomposition method.

8. The low-nitrogen concentrated carbon combustion process method as claimed in claim 1, wherein the heat pump system takes return water in a boiler water system as a cold source to reduce the temperature of the flue gas at the tail of the boiler.

9. A low-nox rich carbon combustion system for use in the low-nox rich carbon combustion process as claimed in any one of claims 1 to 8, said system comprising: the system comprises a boiler, a heat pump system, a carbon capture system and a mixing box;

the tail flue gas of the boiler is used as a high-temperature heat source and sent into a heat pump system for heat exchange, most of low-temperature flue gas discharged by the heat pump system enters a carbon capture system for separation and extraction of carbon dioxide gas or liquid products, and a small part of low-temperature flue gas discharged by the heat pump system is mixed with supplementary oxygen in a mixing box and then enters the boiler again for cyclic utilization.

10. The low-nitrogen rich carbon combustion system of claim 9, wherein the mixing tank is an empty tank, and a drain is provided at the bottom of the empty tank.

Background

The carbon capture technology is the basis and precondition of carbon emission reduction measures and is also the link with the largest cost and energy consumption in the whole carbon capture, utilization and sequestration system. According to the existing energy structure in China, the largest proportion of the production and supply industries of electric power and heat in carbon emission can be found easily. Therefore, the carbon dioxide emission of the capture boiler system has important significance for reducing the total carbon dioxide emission in China. At present, there are 3 trapping technical routes at home and abroad, namely pre-combustion trapping, oxygen-enriched combustion and post-combustion trapping. Post-combustion capture technology is considered to be the most viable method of carbon capture. Post-combustion capture is the system's separation of CO from the flue gas produced by the combustion of a primary fuel in air₂. These systems typically use liquid solvents to capture small amounts of CO from flue gases whose main component is nitrogen (from air)₂The absorption method of the chemical solvent MEA (ethanolamine) as the liquid solvent is most commonly used among the components (generally 3-15% by volume). However, the MEA solution itself has some inherent disadvantages, among which the MEA itself is expensive, the regeneration temperature is too high, the required energy consumption is large, the investment and operation cost is high, and the equipment is easily corroded.

Disclosure of Invention

The invention provides a low-nitrogen and concentrated-carbon combustion process method and a low-nitrogen and concentrated-carbon combustion system, which solve the technical problems of large investment, undesirable effect and high operation cost in flue gas carbon capture.

The invention provides a low-nitrogen and rich-carbon combustion process method for solving the technical problems, which comprises the following steps:

s1, feeding the tail flue gas of the boiler as a high-temperature heat source into a heat pump system for heat exchange;

s2, separating and extracting gaseous or liquid carbon dioxide products from most of low-temperature flue gas discharged from the heat pump system in a carbon capture system;

and a small part of low-temperature flue gas discharged from the heat pump system is mixed with supplementary oxygen and then enters the boiler again for cyclic utilization. The operation of the step not only supplements oxygen required in combustion, but also dilutes nitrogen in the flue gas, reduces the formation of thermal nitrogen in the final flue gas, and controls the formation of thermal nitrogen oxide in the combustion process.

Optionally, the tail flue gas of the boiler firstly passes through the desulfurization and denitrification device to be subjected to desulfurization and denitrification and then enters the heat pump system.

Optionally, the heat pump system is provided with two discharge ports, one large discharge port is used for discharging most of the low-temperature flue gas, and the other small discharge port is used for discharging a small part of the low-temperature flue gas.

Optionally, a control valve is arranged on the small discharge port, and the control valve is used for opening or closing the small discharge port to release carbon dioxide quantitatively.

Optionally, the S2 specifically includes: and a small part of low-temperature flue gas discharged from the heat pump system is mixed with supplementary oxygen in the mixing box and then is sent into the boiler through the fan for cyclic utilization.

Optionally, the S2 specifically includes: the carbon capture system separates and extracts carbon dioxide gas or liquid products by a physical method, wherein the physical method is physical adsorption or a membrane method.

Optionally, the S2 specifically includes: the carbon capture system separates and extracts carbon dioxide gas or liquid products by a chemical method, wherein the chemical method is a chemical solvent absorption method or a thermal decomposition method.

Optionally, the heat pump system uses return water in a boiler water system as a cold source to reduce the temperature of the flue gas at the tail of the boiler.

The present invention also provides a low-nitrogen rich carbon combustion system for use in the low-nitrogen rich carbon combustion process as described above, the low-nitrogen rich carbon combustion system comprising: the system comprises a boiler, a heat pump system, a carbon capture system and a mixing box;

the tail flue gas of the boiler is used as a high-temperature heat source and sent into a heat pump system for heat exchange, most of low-temperature flue gas discharged by the heat pump system enters a carbon capture system for separation and extraction of carbon dioxide gas or liquid products, and a small part of low-temperature flue gas discharged by the heat pump system is mixed with supplementary oxygen in a mixing box and then enters the boiler again for cyclic utilization.

Optionally, the mixing tank is an empty tank, and a drainage device is arranged at the bottom of the empty tank.

The embodiment of the invention also provides a system for the low-nitrogen and rich-carbon combustion process method, which comprises the following steps: boiler, heat pump system, carbon capture system and mixing box. The tail flue gas of the boiler is used as a high-temperature heat source and sent into a heat pump system for heat exchange, most of low-temperature flue gas discharged by the heat pump system enters a carbon capture system for separation and extraction of carbon dioxide gas or liquid products, and a small part of low-temperature flue gas discharged by the heat pump system is mixed with supplementary oxygen in a mixing box and then enters the boiler again for cyclic utilization.

Preferably, the mixing box is an empty box, and a drainage device is arranged at the bottom of the empty box. The gas in the mixing box has the heat exchange process, consequently can produce aqueous vapor, can form water stagnation at last and stay in the empty case, and the drainage device of empty case discharges water, avoids water to accumulate more and forms the back overflow, can also avoid influencing the heat exchange efficiency of gas in the mixing box because the heat absorption of ponding with release heat.

Has the advantages that: the invention provides a low-nitrogen concentrated carbon combustion process method and a system, comprising the following steps: s1, feeding the tail flue gas of the boiler as a high-temperature heat source into a heat pump system for heat exchange; s2, separating and extracting gaseous or liquid carbon dioxide products from most of low-temperature flue gas discharged from the heat pump system in a carbon capture system; and a small part of low-temperature flue gas discharged from the heat pump system is mixed with supplementary oxygen and then enters the boiler again for cyclic utilization. The scheme realizes the carbon concentration and capture functions of tail flue gas discharged by the boiler system, improves the enrichment degree of carbon dioxide in the flue gas and realizes better carbon recovery; the method not only supplements oxygen required in combustion, but also dilutes nitrogen in the flue gas, reduces the formation of thermal nitrogen in the final flue gas, and controls the formation of thermal nitrogen oxide in the combustion process. On the other hand, the low-grade heat source is recycled, the overall energy efficiency of the system is improved, the environmental protection is facilitated, the original equipment of the boiler is utilized, and the overall cost is low.

The foregoing description is only an overview of the technical solutions of the present invention, and in order to make the technical solutions of the present invention more clearly understood and to implement them in accordance with the contents of the description, the following detailed description is given with reference to the preferred embodiments of the present invention and the accompanying drawings. The detailed description of the present invention is given in detail by the following examples and the accompanying drawings.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the invention without limiting the invention. In the drawings:

FIG. 1 is a functional schematic diagram of the low-nitrogen and rich-carbon combustion process and system of the present invention.

Description of reference numerals: the system comprises a boiler 1, a heat pump system 2, a carbon capture system 3, a fan 4 and a mixing box 5.

Detailed Description

The principles and features of this invention are described below in conjunction with the following drawings, which are set forth by way of illustration only and are not intended to limit the scope of the invention. The invention is described in more detail in the following paragraphs by way of example with reference to the accompanying drawings. Advantages and features of the present invention will become apparent from the following description and from the claims. It is to be noted that the drawings are in a very simplified form and are not to precise scale, which is merely for the purpose of facilitating and distinctly claiming the embodiments of the present invention.

It will be understood that when an element is referred to as being "secured to" another element, it can be directly on the other element or intervening elements may also be present. When a component is referred to as being "connected" to another component, it can be directly connected to the other component or intervening components may also be present. When a component is referred to as being "disposed on" another component, it can be directly on the other component or intervening components may also be present. The terms "vertical," "horizontal," "left," "right," and the like as used herein are for illustrative purposes only.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

As shown in FIG. 1, the invention provides a low-nitrogen rich carbon combustion process method, which comprises the following steps: s1, sending the tail flue gas of the boiler 1 as a high-temperature heat source into a heat pump system 2 for heat exchange; s2, separating and extracting gaseous or liquid carbon dioxide products from most of low-temperature flue gas discharged from the heat pump system 2 in the carbon capture system 3; a small part of low-temperature flue gas discharged from the heat pump system 2 is mixed with supplementary oxygen and then enters the boiler 1 again for cyclic utilization, so that the oxygen required in the combustion is supplemented, the nitrogen in the flue gas is diluted, the formation of the final thermal nitrogen in the flue gas is reduced, and the formation of the thermal nitrogen oxide in the combustion process is controlled.

The scheme realizes the carbon concentration and capture functions of the tail flue gas discharged by the boiler 1 system, improves the enrichment degree of carbon dioxide in the flue gas and realizes better carbon recovery; on the other hand, the low-grade heat source is recycled, the overall energy efficiency of the system is improved, the environmental protection is facilitated, the original equipment of the boiler 1 is utilized, the overall manufacturing cost is low, and the implementation, the popularization and the application are convenient.

The tail smoke gas discharge port of the boiler 1 is connected with the gas inlet of the heat pump system 2 in a sealing mode through a pipeline, the heat pump system 2 is provided with at least one low-temperature smoke gas discharge port, high-temperature smoke gas discharged from the boiler 1 is subjected to heat exchange through the heat pump system 2 and then is discharged to the carbon capture system 3 through the low-temperature smoke gas discharge port, and the other part of low-temperature smoke gas returns to the boiler 1 through the pipeline again.

Optionally, the tail flue gas of the boiler 1 firstly passes through the desulfurization and denitrification device to be desulfurized and denitrated and then enters the heat pump system 2. For coal fired boiler 1, the required SOx/NOx control device of environmental protection can be set up to 1 export of boiler, and afterbody flue gas can get into heat pump system 2 through environmental protection device reentrant earlier.

Optionally, the heat pump system 2 is provided with two discharge ports, one large discharge port is used for discharging most of the low-temperature flue gas, and the other small discharge port is used for discharging a small part of the low-temperature flue gas. A small part of low-temperature flue gas discharged from the heat pump system 2 and supplementary oxygen are mixed in a mixing box 5 and then are sent into the boiler 1 through a fan 4 for cyclic utilization. For the gas boiler 1, the flue gas cooled by the heat pump system 2 is taken as the circulating flue gas in the flue gas recirculation, and then is uniformly mixed with the supplementary oxygen in the mixing box 5. The mixed gas is sent into the hearth through the fan 4, so that the combustion temperature of the hearth is reduced, and the generation of nitrogen oxides is reduced. For the coal-fired boiler 1, part of the low-temperature flue gas cooled by the heat pump system 2 is uniformly mixed with the supplementary oxygen in the mixing box 5, and the mixed gas is used as secondary air and is sent into a hearth for supporting combustion through the fan 4. And (4) completing the enrichment of the carbon dioxide in the flue gas through the circulation of the steps.

Optionally, a control valve is arranged on the small discharge port, and the control valve is used for opening or closing the small discharge port to release carbon dioxide quantitatively. The control valve can be an electronic valve, the opening and closing of the valve can be remotely controlled, the electronic valve can be remotely opened, and part of low-temperature flue gas in the heat pump system 2 flows into the mixing box 5 along the connecting pipe and then reaches the boiler 1 again through the exhaust holes of the peripheral pipeline. The amount of the hot pot of the low-temperature smoke is controlled by the combustion condition of the boiler 1.

Alternatively, the temperature of most of the low-temperature flue gas discharged from the heat pump system 2 is not higher than 15 ℃. The tail flue gas of the boiler 1 is used as a high-temperature heat source and sent into a heat pump system 2 for heat exchange, low-temperature flue gas (about 10 ℃ in an ideal state) is output, and condensed water after the flue gas is condensed is discharged. For the gas boiler 1, the amount of the condensed water is huge, and the volume of the output low-temperature flue gas is reduced sharply;

optionally, the S2 specifically includes: the carbon capture system 3 separates and extracts the carbon dioxide gas or liquid product by a physical method, such as physical adsorption or a membrane method. The carbon capture system 3 is located at the very end of the flue gas treatment system. The low-temperature flue gas output by the heat pump system 2 contains high-concentration carbon dioxide, and after entering the carbon capture system 3, the gaseous or liquid product of the carbon dioxide is separated and extracted by a physical method or a chemical method and is used or sold as industrial gas. The physical methods mainly include physical adsorption (activated carbon) and membrane methods; the chemical method mainly comprises a chemical solvent absorption method and a thermal decomposition method.

Optionally, the heat pump system 2 uses the return water in the water system of the boiler 1 as a cold source to reduce the temperature of the flue gas at the tail of the boiler 1. Energy is saved, and the heat energy utilization rate of the boiler 1 system is improved.

Optionally, the mixing box 5 is an empty box, and a drainage device is arranged at the bottom of the empty box. And water generated in the cooling process is discharged in time through the drainage device.

Has the advantages that:

(1) the enrichment degree of the carbon dioxide in the flue gas is improved. A small part of low-temperature flue gas discharged from the heat pump system is mixed with supplementary oxygen and then enters the boiler again for cyclic utilization, so that oxygen required in combustion is supplemented, nitrogen in the flue gas is diluted, the formation of thermal nitrogen in the final flue gas is reduced, and the formation of thermal nitrogen oxide in the combustion process is controlled.

(2) The low-grade heat source is recycled, and the overall energy efficiency of the system is improved.

(3) Is beneficial to environmental protection.

(4) The original equipment of the boiler is utilized, and the overall cost is low.

The foregoing is merely a preferred embodiment of the invention and is not intended to limit the invention in any manner; the present invention may be readily implemented by those of ordinary skill in the art as illustrated in the accompanying drawings and described above; however, those skilled in the art should appreciate that they can readily use the disclosed conception and specific embodiments as a basis for designing or modifying other structures for carrying out the same purposes of the present invention without departing from the scope of the invention as defined by the appended claims; meanwhile, any changes, modifications, and evolutions of the equivalent changes of the above embodiments according to the actual techniques of the present invention are still within the protection scope of the technical solution of the present invention.