Waste heat boiler system matched with low-rank coal rapid pyrolysis device

Abstract

The invention relates to the technical field of boilers, and discloses a waste heat boiler system matched with a low-rank coal rapid pyrolysis device, which comprises a first flue, a second flue and a third flue, the upper end of the first flue is connected with a high-temperature flue, and the lower end of the first flue is communicated with the lower end of the second flue through a connecting flue; a horizontal flue and a high-temperature fine ash dust remover are sequentially connected from the upper end of the second flue to the upper end of the third flue; the lower end of the third flue is connected with a flue outlet; and a front evaporator is arranged in the first flue. According to the invention, combustible gas in high-temperature waste gas generated by the low-rank coal rapid pyrolysis device can be combusted; the condition that the coke breeze is gathered in the tail flue of the boiler to cause tail combustion so as to influence the safe operation of the boiler is avoided; in the operation process, the heating surface is kept in a relatively clean state, the heat exchange effect of the heating surface is guaranteed, and it is guaranteed that the boiler and follow-up devices can operate continuously, safely and stably; and the operation and maintenance cost of the denitration reactor is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of boilers, and in particular to a waste heat boiler system matched with a low-rank coal rapid pyrolysis device. Background Art

[0002] Low-rank coal generally has a high oil content. Through medium and low temperature pyrolysis, the coal is heated to 500℃~800℃ in an airless or oxygen-deficient environment, and the coal can be decomposed into gas (pyrolysis gas), liquid (coal tar) and solid (semi-coke).

[0003] The most prominent feature of pyrolysis technology is that it can effectively improve resource utilization efficiency. This is because the direct combustion of low-rank coal will convert a large number of high-value-added components into CO2. Through pyrolysis, tar in the coal can be extracted, and coal gas and semi-coke can be produced at the same time, dividing the raw coal into three parts to avoid resource waste.

[0004] The production process conditions of low-rank coal pyrolysis are mild. The pyrolysis temperature is generally 550℃~700℃, the reaction pressure is close to normal pressure, and the production system does not require a large air separation unit. It also has good environmental performance. The semi-coke obtained from coal pyrolysis can be used as boiler fuel and gasification raw material. It contains less pollutants than raw coal and has less impact on the environment.

[0005] The low-rank coal rapid pyrolysis device will produce high-temperature exhaust gas at 550℃~700℃, which contains a small amount of hydrogen (H2), methane (CH4) and other alkane combustible gases and toxic gas carbon monoxide (CO). Low concentration of carbon monoxide can cause headaches, dizziness, and nausea, while high concentration of carbon monoxide can cause death.

[0006] The high-temperature flue gas produced by the low-rank coal rapid pyrolysis device contains a large amount of dust. After the high-temperature dust removal at the front end, there is still a large amount of micron-level dust that cannot be removed. The average particle size of the dust is 20μm, the dust content is 4g / Nm3 under normal working conditions, and 20g / Nm3 under maximum working conditions. The dust is coke powder, with an auto-ignition point of 300-400℃ and a high low calorific value.

[0007] When conventional waste heat boilers are used in low-rank coal pyrolysis devices, when the boiler is running at low load, the combustion temperature is too low, which will prevent the powdered coke in the flue gas from being completely burned in the combustion chamber. The powdered coke will accumulate on the tail heat exchange surface, which is easy to cause tail combustion. In addition, there is a large amount of fly ash in the flue gas, and conventional waste heat boilers cannot adapt to flue gas containing a large amount of fly ash, resulting in serious ash accumulation on the convection heat exchange surface, ineffective heat exchange, high exhaust temperature, low waste heat utilization rate, and affecting the normal use of subsequent devices. Summary of the invention

[0008] In order to make up for the above deficiencies, the present invention provides a waste heat boiler system that is compatible with a low-rank coal rapid pyrolysis device and can treat the waste gas generated by a low-rank coal rapid pyrolysis device, treat the fly ash generated after the flue gas combustion in the boiler system, and recover the waste heat of the flue gas.

[0009] To achieve the above object, the present invention provides the following technical solutions:

[0010] A waste heat boiler system matched with a low-rank coal rapid pyrolysis device comprises a first flue, a second flue and a third flue; the upper end of the first flue is connected to a high-temperature flue, and the lower end of the first flue is connected to the lower end of the second flue through a connecting flue; a horizontal flue and a high-temperature fine ash dust collector are connected in sequence from the upper end of the second flue to the upper end of the third flue; the lower end of the third flue is connected to the flue outlet; a pre-evaporator is arranged in the first flue; a burner is arranged above the flue gas inlet in the second flue; a high-temperature evaporator is arranged in the horizontal flue, and a two-stage superheater, a first low-temperature evaporator, a second low-temperature evaporator, a gas preheater, an economizer and an SCR denitrification device are arranged in sequence from top to bottom in the third flue; a steam drum is arranged on the top of the third flue, and a bypass flue is arranged in the middle; one end of the bypass flue is arranged between the gas preheater and the economizer of the third flue, and the other end is arranged between the economizer and the SCR denitrification device.

[0011] Furthermore, the economizer feeds water to the steam drum, the steam drum feeds water to the pre-evaporator, the high-temperature evaporator and the low-temperature evaporator, the steam-water mixture heated in the pre-evaporator, the high-temperature evaporator and the low-temperature evaporator returns to the steam drum, the saturated steam outlet on the steam drum is connected to the superheater inlet, and the superheater outputs medium-pressure superheated steam.

[0012] Furthermore, the front evaporator and the high-temperature evaporator adopt a light tube structure.

[0013] Furthermore, the first low-temperature evaporator and the second low-temperature evaporator adopt a spiral fin tube structure, the pitch of the spiral fins is 10 mm to 12 mm, and the height of the spiral fins is 12 mm to 15 mm.

[0014] Furthermore, the two-stage superheater arranged in the third flue is a high-temperature superheater and a low-temperature superheater from top to bottom, the saturated steam outlet on the steam drum is connected to the inlet of the low-temperature superheater, and medium-pressure superheated steam is generated at the outlet of the high-temperature superheater.

[0015] Furthermore, the second flue adopts a circular structure, and two burners are arranged at the lower part of the second flue in a tangential arrangement; the connecting flue connecting the front evaporator and the second flue is evenly connected to the second flue along the circumferential direction.

[0016] Furthermore, the high-temperature fine ash dust collector is arranged after the high-temperature evaporator of the horizontal flue, and the flue gas after dust removal by the high-temperature fine ash dust collector enters the third flue and exchanges heat with the heating surface in the third flue.

[0017] Furthermore, the coal gas preheater arranged between the second low-temperature evaporator and the economizer in the third flue is used to heat the low-pressure coal gas from 100°C to 300°C.

[0018] Furthermore, a group of economizers is arranged after the gas preheater of the third flue, and the feed water is heated in the economizer and then sent to the steam drum.

[0019] Furthermore, a bypass butterfly valve is provided on the bypass flue, and the temperature of the flue gas entering the SCR denitrification device is adjusted by adjusting the opening of the bypass butterfly valve so that the flue gas temperature meets the denitrification temperature requirement.

[0020] The present invention has the following beneficial effects:

[0021] 1. The present invention can burn off the combustible gases such as hydrogen (H2), methane (CH4), carbon monoxide (CO) in the high-temperature exhaust gas generated by the low-rank coal rapid pyrolysis device through high-temperature combustion in the waste heat boiler, and effectively utilize the heat carried in the high-temperature exhaust gas;

[0022] 2. The present invention can burn the coke powder in the high-temperature exhaust gas generated by the low-rank coal rapid pyrolysis device in the second channel through high-temperature combustion of the waste heat boiler, safely and effectively utilizing the heat of the coke powder, while preventing the coke powder from accumulating in the flue at the tail of the boiler, causing tail combustion and affecting the safe operation of the boiler;

[0023] 3. The present invention can effectively remove a large amount of dust carried in the flue gas after combustion by arranging a high-temperature fine ash dust collector in the waste heat boiler, and reduce the dust content from 4g / Nm3 in the normal working condition before dust removal and 20g / Nm3 in the maximum working condition to less than 1g / Nm3, thereby ensuring that the ash amount entering the third flue is within a reasonable range. During operation, cleaning measures such as shock waves or steam soot blowing are used to keep the heating surface in a relatively clean state, thereby ensuring the heat exchange effect of the heating surface and ensuring that the boiler and subsequent devices can continue to operate safely and stably.

[0024] 4. The present invention adjusts the flue gas temperature entering the SCR denitration device by adjusting the opening of the bypass valve, so that the flue gas temperature is always maintained at 340°C to 380°C, which greatly improves the denitration efficiency, prolongs the service life of the catalyst, and reduces the operation and maintenance costs of the denitration reactor. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a structural schematic diagram of the present invention;

[0026] Explanation of the reference numerals in the accompanying drawings: 1. Waste heat boiler flue inlet; 2. First flue; 3. Pre-evaporator; 4. Connecting flue; 5. Flue gas distribution main pipe; 6. Flue gas distribution branch pipe; 7. Burner; 8. Second flue; 9. Horizontal flue; 10. High-temperature evaporator; 11. High-temperature fine ash dust collector; 12. Third flue; 13. High-temperature superheater; 14. Low-temperature superheater; 15. First low-temperature evaporator; 16. Second low-temperature evaporator; 17. Gas preheater; 18. Economizer; 19. Economizer bypass flue; 20. Bypass butterfly valve; 21. SCR denitrification device; 22. Waste heat boiler flue outlet; 23. Steam drum. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] Reference Figure 1 An embodiment of the present invention is as follows: a waste heat boiler system for a low-rank coal rapid pyrolysis device comprises a first flue 2, a second flue 8 and a third flue 12; the upper end of the first flue 2 is connected to the high-temperature flue, the lower end of the first flue 2 is connected to the lower end of the second flue 8 through a connecting flue 4, the upper end of the second flue 8 is connected to the horizontal flue 9, the outlet of the horizontal flue 9 is connected to the inlet of a high-temperature fine ash dust collector 11, and the outlet of the high-temperature fine ash dust collector 11 is connected to the upper end of the third flue 12. A pre-evaporator 3 is arranged in the first flue 2, a burner 7 is arranged above the flue gas inlet of the second flue 8, a high-temperature evaporator 10 is arranged in the horizontal flue 9, and a high-temperature superheater 13, a low-temperature superheater 14, a first low-temperature evaporator 15, a second low-temperature evaporator 16, a gas preheater 17, an economizer 18 and an SCR denitrification device 21 are arranged in the third flue 12 from top to bottom; the third flue 12 below the SCR denitrification device 21 is connected to the outlet flue, a steam drum 23 is arranged on the top of the third flue 12, and a bypass flue 19 is connected to the third flue 12 located between the gas preheater 17 and the economizer 18, and the bypass flue 19 is connected to the third flue 12 after the economizer 18; a bypass butterfly valve 20 is arranged on the bypass flue 19.

[0029] Among them, the above-mentioned waste heat boiler system equipped with the low-rank coal rapid pyrolysis device, wherein the economizer 18 supplies water to the steam drum 23, the steam drum 23 supplies water to the pre-evaporator 3, the high-temperature evaporator 10, the first low-temperature evaporator 15 and the second low-temperature evaporator 16, the steam-water mixture after being heated in the pre-evaporator 3, the high-temperature evaporator 10, the first low-temperature evaporator 15 and the second low-temperature evaporator 16 returns to the steam drum 23, the saturated steam outlet on the steam drum 23 is connected to the superheater inlet, and the superheater outputs medium-pressure superheated steam.

[0030] Among them, the above-mentioned waste heat boiler system equipped with the low-rank coal rapid pyrolysis device, wherein the pre-evaporator 3 and the high-temperature evaporator 10 adopt a light tube structure, the first low-temperature evaporator 15 and the second low-temperature evaporator 16 adopt a spiral fin tube structure, the spacing of the spiral fins is 10 to 12 mm, and the height of the spiral fins is 12 to 15 mm.

[0031] Among them, the above-mentioned waste heat boiler system equipped with the low-rank coal rapid pyrolysis device, wherein a two-stage superheater is arranged in the third flue 12, which are a high-temperature superheater 13 and a low-temperature superheater 14 from top to bottom, and the saturated steam outlet on the steam drum 23 is connected to the inlet of the low-temperature superheater 14, and medium-pressure superheated steam is generated at the outlet of the high-temperature superheater 13.

[0032] Among them, the above-mentioned waste heat boiler system equipped with the low-rank coal rapid pyrolysis device, wherein the second flue 8 adopts a circular structure, and two burners 7 are arranged at the lower part of the second flue 8, and a tangential arrangement is adopted. The high-temperature connecting flue 4 connecting the pre-evaporator 3 and the second flue 8 is evenly connected to the second flue 8 along the circumferential direction.

[0033] Among them, the above-mentioned waste heat boiler system equipped with the low-rank coal rapid pyrolysis device, wherein the high-temperature fine ash dust collector 11 is arranged after the high-temperature evaporator 10 of the horizontal flue 9, and the flue gas after dust removal by the high-temperature fine ash dust collector 11 enters the third flue 12 and exchanges heat with the heating surface in the third flue 12.

[0034] Among them, the above-mentioned waste heat boiler system equipped with the low-rank coal rapid pyrolysis device, wherein a gas preheater 17 is arranged between the second low-temperature evaporator 16 and the economizer 18 in the third flue 12 for heating the low-pressure coal gas from 100°C to 300°C.

[0035] Among them, the above-mentioned waste heat boiler system equipped with the low-rank coal rapid pyrolysis device, wherein a group of economizers 18 are arranged after the gas preheater 17 of the third flue 12, and the feed water enters the economizer 18 for heating and then is sent to the steam drum 23.

[0036] Among them, the aforementioned waste heat boiler system equipped with the low-rank coal rapid pyrolysis device, wherein the third flue 12 between the coal gas preheater 17 and the economizer 18 is connected with a bypass flue 19, the bypass flue 19 is connected with the third flue 12 after the economizer 18, and a bypass butterfly valve 20 is arranged on the bypass flue 19. The flue gas temperature entering the SCR denitration device 21 is adjusted by adjusting the opening of the bypass butterfly valve 20, so that the flue gas temperature meets the denitration temperature requirement.

[0037] The denitrified flue gas passes through the outlet of the third flue 13 and enters the subsequent device for treatment.

[0038] The flue gas flow of the waste heat boiler system of the low-rank coal rapid pyrolysis device described in this embodiment is as follows: the high-temperature flue gas generated by the low-rank coal rapid pyrolysis device enters the first flue 2 from the flue inlet 1 of the waste heat boiler, and the high-temperature flue gas entering the first flue 2 exchanges heat with the pre-evaporator 3 and then enters the connecting flue 4 between the first and second flues, and the high-temperature flue gas in the connecting flue 4 between the first and second flues enters the flue gas distribution main pipe 5, and then enters the second flue 8 after being evenly distributed through the flue gas distribution branch pipe 6, and the high-temperature flue gas entering the second flue 8 is ignited by the burner 7 for full combustion, thereby removing combustible gases, toxic gases and coke in the high-temperature flue gas. The high-temperature flue gas after combustion moves upward and enters the horizontal flue 9. The high-temperature flue gas entering the horizontal flue 9 exchanges heat with the high-temperature evaporator 10 and then enters the high-temperature fine ash dust collector 11. The function of the high-temperature evaporator 10 is as follows: the high-temperature flue gas after combustion in the second flue has a flue temperature of 900°C. The high-temperature fine ash dust collector 11 is easily damaged at such a high flue gas temperature, and the long-term safe and stable operation of the high-temperature fine ash dust collector 11 cannot be guaranteed. Therefore, it is necessary to arrange a high-temperature evaporator 10 in front of the high-temperature fine ash dust collector 11. The high-temperature evaporator 10 exchanges heat with the 900°C high-temperature flue gas after combustion to reduce the flue gas temperature to 700°C, thereby meeting the use conditions of the high-temperature fine ash dust collector 11 and ensuring the long-term safe and stable operation of the high-temperature fine ash dust collector 11. The function of the high-temperature fine ash dust collector 11 is to arrange the high-temperature fine ash dust collector after the second flue 8, which will not affect the full combustion of the powdered coke in the high-temperature flue gas in the second channel 8, and can clean the fine ash in the flue gas before the flue gas exchanges heat with the heating surface arranged in the third flue, reduce the dust on the heat exchange surface, and effectively improve the heat exchange efficiency of the heat exchange surface. The high-temperature flue gas after dust removal by the high-temperature fine ash dust collector 11 enters the third flue 12, and the high-temperature flue gas entering the third flue 12 exchanges heat with the high-temperature superheater 13, the low-temperature superheater 14, the first low-temperature evaporator 15, the second low-temperature evaporator 16, the gas preheater 17, and the economizer 18 in sequence. The flue gas that completes the heat exchange enters the SCR denitrification device 21 for denitrification treatment, and the flue gas denitrified by the SCR denitrification device 21 is discharged through the flue outlet 22 of the waste heat boiler. An economizer bypass flue 19 is also provided between the gas preheater 17 and the economizer 18. The function of the bypass flue 19 is as follows: when the temperature of the flue gas entering the SCR denitrification device 21 is lower than 340°C, the bypass butterfly valve 20 on the bypass flue 19 is opened, so that part of the flue gas that has exchanged heat with the gas preheater 17 can enter the SCR denitrification device 21 directly through the bypass flue without exchanging heat with the economizer 18. In this way, the temperature of the flue gas entering the SCR denitrification device 21 can be maintained within the range of 360±20°C, thereby effectively ensuring the denitrification efficiency of the SCR denitrification device 21 and reducing the operation and maintenance costs of the SCR denitrification device 21.

[0039] The steam-water flow of the waste heat boiler system of the low-rank coal rapid pyrolysis device described in this embodiment is as follows: the boiler feed water enters the economizer 18 to absorb heat, the hot water at the outlet of the economizer 18 is sent to the drum 23, the drum 23 feeds water to the pre-evaporator 3, the high-temperature evaporator 10, the first low-temperature evaporator 15 and the second low-temperature evaporator 16, and the steam-water mixture after being heated flows back into the drum 23. The saturated steam outlet on the drum 23 is connected to the inlet end of the low-temperature superheater 14, the outlet end of the low-temperature superheater 14 is connected to the inlet end of the high-temperature superheater 13, and the outlet end of the high-temperature superheater 13 produces superheated steam of medium temperature and medium pressure.

[0040] In the description of the present invention, it should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0041] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0042] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0043] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A waste heat boiler system for a low-rank coal rapid pyrolysis device, comprising a first flue (2), a second flue (8) and a third flue (12); the upper end of the first flue (2) is connected to a high-temperature flue, and the lower end of the first flue (2) is connected to the lower end of the second flue (8) through a connecting flue (4); a horizontal flue (9) and a high-temperature fine ash collector (11) are connected in sequence from the upper end of the second flue (8) to the upper end of the third flue (12); the lower end of the third flue (12) is connected to a flue outlet (22); a pre-evaporator (3) is arranged in the first flue (2); a second flue (8) is arranged above the flue gas inlet The invention relates to a burner (7); a high-temperature evaporator (10) is arranged in the horizontal flue (9); a two-stage superheater, a first low-temperature evaporator (15), a second low-temperature evaporator (16), a gas preheater (17), an economizer (18) and an SCR denitration device (21) are arranged in sequence from top to bottom in the third flue (12); a steam drum (23) is arranged at the top of the third flue (12), and a bypass flue (19) is arranged in the middle; one end of the bypass flue (19) is arranged between the gas preheater (17) and the economizer (18) of the third flue (12), and the other end is arranged between the economizer (18) and the SCR denitration device (21).

2. A waste heat boiler system for a low-rank coal rapid pyrolysis device according to claim 1, characterized in that: The economizer (18) supplies water to the steam drum (23), and the steam drum (23) supplies water to the pre-evaporator (3), the high-temperature evaporator (10) and the low-temperature evaporator. The steam-water mixture heated in the pre-evaporator (3), the high-temperature evaporator (10) and the low-temperature evaporator returns to the steam drum (23). The saturated steam outlet on the steam drum (23) is connected to the superheater inlet, and the superheater outputs medium-pressure superheated steam.

3. The waste heat boiler system for low-rank coal rapid pyrolysis device according to claim 1 is characterized in that: The pre-evaporator (3) and the high-temperature evaporator (10) adopt a light tube structure.

4. The waste heat boiler system for low-rank coal rapid pyrolysis device according to claim 1 is characterized in that: The first low-temperature evaporator (15) and the second low-temperature evaporator (16) adopt a spiral fin tube structure, the pitch of the spiral fins is 10 mm to 12 mm, and the height of the spiral fins is 12 mm to 15 mm.

5. A waste heat boiler system for a low-rank coal rapid pyrolysis device according to claim 1 or 2, characterized in that: The two-stage superheater arranged in the third flue (12) is a high-temperature superheater (13) and a low-temperature superheater (14) from top to bottom. The saturated steam outlet on the steam drum (23) is connected to the inlet of the low-temperature superheater (14), and medium-pressure superheated steam is generated at the outlet of the high-temperature superheater (13).

6. A waste heat boiler system for a low-rank coal rapid pyrolysis device according to claim 1 or 2, characterized in that: The second flue (8) adopts a circular structure, and two burners (7) are arranged at the lower part of the second flue (8) in a tangential arrangement; the connecting flue (4) connecting the front evaporator (3) and the second flue (8) is evenly connected to the second flue (8) along the circumferential direction.

7. The waste heat boiler system for low-rank coal rapid pyrolysis device according to claim 1, characterized in that: The high-temperature fine ash dust collector (11) is arranged behind the high-temperature evaporator (10) of the horizontal flue (9). The flue gas after dust removal by the high-temperature fine ash dust collector (11) enters the third flue (12) and exchanges heat with the heating surface in the third flue (12).

8. The waste heat boiler system for low-rank coal rapid pyrolysis device according to claim 1, characterized in that: The coal gas preheater (17) arranged between the second low-temperature evaporator (16) and the economizer (18) in the third flue (12) is used to heat the low-pressure coal gas from 100°C to 300°C.

9. The waste heat boiler system for low-rank coal rapid pyrolysis device according to claim 1, characterized in that: A group of economizers (18) are arranged behind the coal gas preheater (17) of the third flue (12), and feed water is heated in the economizer (18) and then sent to the steam drum (23).

10. The waste heat boiler system for low-rank coal rapid pyrolysis device according to claim 1, characterized in that: The bypass flue (19) is provided with a bypass butterfly valve (20), and the temperature of the flue gas entering the SCR denitration device (21) is adjusted by adjusting the opening of the bypass butterfly valve (20), so that the flue gas temperature meets the denitration temperature requirement.

Images