Gas boiler with ultra-low load operation and high load change rate functions

Abstract

The utility model discloses a gas boiler with ultra-low load operation and high load change rate functions, which comprises a burner, a steam pocket, a hearth and a tail flue, the steam pocket is connected with a downcomer, and a first evaporator, a superheater and a second evaporator are sequentially arranged in the hearth along the flowing direction of flue gas. The upper ends and the lower ends of the first evaporator and the second evaporator communicate with the steam pocket and the downcomer through pipelines correspondingly, and a high-temperature economizer, an SCR denitration device, a low-temperature economizer and an air preheater are sequentially arranged in the tail flue in the flue gas direction. According to the gas boiler with the ultra-low load operation and the high load change rate function, through structural arrangement and water circulation process optimization, the boiler can operate under the 5% ultra-low load, forced shutdown of the boiler when fuel is insufficient is avoided, meanwhile, the load change rate of the boiler reaches up to 25% / min, gas flow fluctuation of a user can be responded in time, and the energy consumption of the boiler is reduced. The investment of a large gas holder is saved, and great economic benefits are brought to owners.

Description

TECHNICAL FIELD

[0001] The utility model relates to steel metallurgy secondary energy recovery, boiler technical field, especially a kind of gas boiler with ultra-low load operation and high load variation rate function. BACKGROUND

[0002] Steel enterprises will produce a large amount of coal gas by-products in the production process, including blast furnace gas, converter gas and coke oven gas. Make full use of secondary energy, efficient recovery and utilization of surplus coal gas power generation, in the current steel industry competition intensifies situation, it is of great significance to improve enterprise competitiveness. There are mainly two types of using coal gas for power generation internationally, mode 1 is the traditional steam single-cycle boiler generator set, mode 2 is gas-steam combined cycle power generation (CCPP).

[0003] Mode 1 steam single-cycle boiler generator set has good coal gas adaptability, can be used for 100% various coal gas, has less restriction on coal gas quality and flow ratio, has large load regulation range, fast load change rate, is the best buffer user and guarantee means for "coal gas zero emission" scheduling, system is simple, operation and maintenance are convenient, has high reliability and availability, occupies less land, has short construction period, low investment, less maintenance cost, and fast economic benefit.

[0004] The main equipment and parts of mode 2 gas-steam combined cycle power generation basically need to be imported, one-time investment is high, operation and maintenance requirements are high and expensive, and the quality and stability of coal gas are required very strictly, and efficiency decreases significantly at low load.

[0005] At present, domestic steel enterprises mainly use mode 1 for coal gas power generation, and the furnace type mainly adopts conventional mature π-type boiler.

[0006] The minimum stable combustion load of conventional Π-type coal gas boiler is 30%, and the load variation rate of conventional Π-type coal gas boiler is relatively low, generally 2%~5% / min.

[0007] The recovered coal gas in steel industry has intermittent characteristics, and the coal gas flow fluctuation is large. In order to adapt to boiler combustion, large-scale coal gas tank is needed to store and regulate coal gas fluctuation. Large-scale coal gas tank has large investment and poor economy. INVENTION CONTENTS

[0008] To solve the above technical problems, the utility model designs a kind of gas boiler with ultra-low load operation and high load variation rate function, through structure arrangement and water circulation process optimization, boiler can operate at 5% ultra-low load, avoid forced shutdown of boiler when fuel is insufficient, simultaneously, boiler load variation rate is as high as 25% / min, can respond to coal gas flow fluctuation of user in time, save large-scale coal gas tank investment, bring great economic benefits to owner.

[0009] The utility model discloses the following technical scheme is adopted:

[0010] A kind of gas boiler with ultra-low load operation and high load variation function, including combustor, steam pocket, hearth and tail flue, steam pocket is connected with downcomer, evaporator one, superheater and evaporator two are sequentially arranged in the hearth along the flow direction of flue gas, the upper and lower ends of evaporator one and evaporator two are respectively communicated steam pocket and downcomer by pipeline, high-temperature economizer, SCR denitration device, low-temperature economizer and air preheater are sequentially arranged in tail flue along flue gas direction.

[0011] As preferred, the combustor is arranged in layers on the front wall of the hearth, and can be arranged in 1-3 layers according to the situation, with 1-2 combustors arranged in each layer.

[0012] As preferred, the hearth is arranged horizontally, and the hearth depth can reach more than 10 m, so that the combustor can be designed with a longer flame to reduce NOx emissions.

[0013] As preferred, the steam pocket is designed with a large volume, so that the water volume is increased to ensure that the steam pocket water level can remain stable during rapid load increase, and a certain amount of flash steam is provided in the early stage of load increase to improve the boiler load variation rate.

[0014] As preferred, the downcomer is arranged with multiple large-section pipes, so that the steam-water flow area is increased to reduce the steam-water flow resistance, which is conducive to the rapid establishment of water circulation and ensures the safety of water circulation under high load variation of the boiler.

[0015] As preferred, the evaporator two, high-temperature economizer and low-temperature economizer can adopt a finned tube structure to improve heat transfer efficiency and reduce the consumption of boiler steel.

[0016] As preferred, the superheater can be designed with 1-3 stages according to the rated temperature at the outlet of the boiler.

[0017] As preferred, the high-temperature economizer, low-temperature economizer and air preheater are supplied to the site in a pipe box structure, so that on-site construction only needs to be hoisted into place, which reduces the on-site installation workload, reduces the on-site installation cost and shortens the construction period of the boiler.

[0018] As preferred, the air preheater can adopt a vertical pipe box structure, a horizontal pipe box structure or a heat pipe structure.

[0019] As preferred, the air preheater can be arranged in 1-2 stages to reduce the flue gas temperature at the outlet of the boiler and improve the efficiency of the boiler.

[0020] The beneficial effects of this utility model are: (1) Through structural layout and water circulation process optimization, it can operate under 5% ultra-low load, avoiding the boiler being forced to shut down when there is insufficient fuel; (2) The boiler load variation rate is as high as 25% / min, which can respond to the user's gas flow fluctuation in a timely manner, save the investment of large gas holders, and bring great economic benefits to the owner. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of this utility model;

[0022] In the diagram: 1. Burner, 2. Steam drum, 3. Downcomer, 4. Furnace, 5. Evaporator 1, 6. Evaporator 2, 7. Superheater, 8. High-temperature economizer, 9. Low-temperature economizer, 10. Air preheater, 11. SCR denitrification device, 12. Tail flue. Detailed Implementation

[0023] The technical solution of this utility model will be further described in detail below through specific embodiments and with reference to the accompanying drawings:

[0024] Example: Figure 1 As shown, a gas boiler with ultra-low load operation and high load variation rate includes a burner 1, a steam drum 2, a furnace 4, and a tail flue 12. A downcomer 3 is connected to the steam drum 2.

[0025] Evaporator 1 (5), superheater 7, and evaporator 2 (6) are arranged sequentially in the furnace along the flue gas flow direction. The upper and lower ends of evaporator 1 and evaporator 2 are connected to the steam drum and downcomer respectively through pipelines. In the tail flue duct 12, high-temperature economizer 8, SCR denitrification device 11, low-temperature economizer 9, and air preheater 10 are arranged sequentially along the flue gas direction.

[0026] This utility model optimizes the structural layout and water circulation process, enabling the boiler to operate at an ultra-low load of 5%, avoiding forced shutdown when fuel is insufficient. At the same time, the boiler load variation rate is as high as 25% / min, which can respond promptly to fluctuations in the user's gas flow, saving investment in large gas holders and bringing great economic benefits to the owner.

[0027] Burners 1 are arranged in layers on the front wall of furnace 4. Depending on the situation, 1 to 3 layers can be arranged, with 1 to 2 burners arranged in each layer.

[0028] To reduce NOx emissions, the furnace is horizontally arranged with a depth of over 10m, and the burner is designed with a longer flame.

[0029] To ensure that the water level in the steam drum remains stable during rapid load increase and to improve the boiler load variation rate, steam drum 2 adopts a large-capacity design, increasing the water volume and providing a certain amount of flash steam in the early stage of load increase.

[0030] To ensure the water circulation safety of the boiler under high load variation rate, the downcomer 3 adopts large-section multi-arrangement, the steam-water flow area is increased, the steam-water flow resistance is reduced, and the water circulation is quickly established.

[0031] To improve the heat transfer efficiency and reduce the steel consumption of the boiler, the evaporator two, the high-temperature economizer and the low-temperature economizer can adopt finned tube structure.

[0032] To meet the requirement of different boilers on the outlet rated temperature, the superheater can adopt 1-3 stage arrangement.

[0033] To reduce the on-site installation workload, reduce the on-site installation cost and shorten the construction period of the boiler, the high-temperature economizer, the low-temperature economizer and the air preheater are supplied to the site in the pipe box structure, and the on-site construction only needs to be hoisted into place.

[0034] The air preheater can adopt vertical pipe box structure, horizontal pipe box structure or heat pipe structure.

[0035] To reduce the boiler outlet flue gas temperature and improve the boiler efficiency, the air preheater can adopt 1-2 stage arrangement.

[0036] The boiler can run under 5% ultra-low load through the structural arrangement and water circulation process optimization, the forced shutdown of the boiler under insufficient fuel is avoided, meanwhile, the boiler load variation rate is as high as 25% / min, the coal gas flow fluctuation of the user can be responded in time, the investment of the large coal gas tank is saved, and great economic benefits are brought to the owner.

[0037] The above-mentioned embodiment is only a preferred scheme of the utility model, and does not limit the utility model in any form, and other variants and modifications are still possible without exceeding the technical scheme recorded in the claims.

Claims

1. A gas-fired boiler with ultra-low load operation and high load variation rate, characterized in that, It includes a burner, a steam drum, a furnace, and a tail flue. A downcomer is connected to the steam drum. In the furnace, an evaporator, a superheater, and an evaporator are arranged in sequence along the flow direction of the flue gas. The upper and lower ends of the evaporator and the evaporator are connected to the steam drum and the downcomer through pipelines, respectively. In the tail flue, a high-temperature economizer, an SCR denitrification device, a low-temperature economizer, and an air preheater are arranged in sequence along the flue gas direction.

2. A gas boiler with ultra-low load operation and high load variation rate as described in claim 1, characterized in that, The burners are arranged in layers on the front wall of the furnace, and can be arranged in 1 to 3 layers, with 1 to 2 burners in each layer.

3. A gas boiler with ultra-low load operation and high load variation rate as described in claim 1, characterized in that, The furnace is arranged horizontally, and the furnace depth can reach more than 10m.

4. A gas boiler with ultra-low load operation and high load variation rate as described in claim 1, characterized in that, The steam drum is designed with a large volume.

5. A gas boiler with ultra-low load operation and high load variation rate as described in claim 1, characterized in that, The downcomer is arranged in multiple sections.

6. A gas boiler with ultra-low load operation and high load variation rate as described in claim 1, characterized in that, The evaporator II, high-temperature economizer and low-temperature economizer adopt a finned tube structure.

7. A gas boiler with ultra-low load operation and high load variation rate as described in claim 1, characterized in that, The superheater is arranged in 1 to 3 stages.

8. A gas boiler with ultra-low load operation and high load variation rate as described in claim 1, characterized in that, The air preheater can be a vertical tube box structure, a horizontal tube box structure, or a heat pipe structure.

9. A gas boiler with ultra-low load operation and high load variation rate as described in claim 1, characterized in that, The air preheater is arranged in 1 to 2 stages.

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