Full-load urea hydrolysis denitration ammonia supply dilution system

Abstract

A full-load urea hydrolysis ammonia dilution system for denitrification belongs to the field of denitrification technology. It includes an air heating system for heating air to dilute and heat the hydrolyzed ammonia gas; a mixing system connected to the air heating system to mix the heated air with unheated air and then with the hydrolyzed ammonia gas; and an automatic adjustment system installed on the pipeline connecting the air heating system and the mixing system to adjust the ratio of heated air to cold air and regulate the temperature of the diluted air. This invention solves the problem of dust content in the urea hydrolysis ammonia dilution air supply for boiler denitrification, while achieving NOx treatment at full load. Compared to conventional SCR denitrification systems using urea hydrolysis heating primary air as the dilution air source, this invention is safer, more reliable, and less expensive, suitable for large, medium, and small boilers. Implementation of this invention achieves full-load urea hydrolysis ammonia dilution and ultra-low NOx emission control with low equipment investment, low energy consumption, and a high degree of automation.

Description

Technical Field

[0001] This utility model belongs to the field of denitrification technology, specifically relating to a full-load urea hydrolysis denitrification and ammonia supply dilution system. Background Technology

[0002] Currently, the vast majority of thermal power plants have undergone denitrification retrofitting. The mainstream technology for controlling ultra-low nitrogen oxide emissions is selective catalytic reduction (SCR). There are three types of reducing agents in SCR denitrification systems: liquid ammonia, ammonia water, and urea. Liquid ammonia and urea are the most commonly used. In China, over 80% of SCR flue gas denitrification devices use liquid ammonia evaporation to prepare the reducing agent. However, liquid ammonia is a toxic and hazardous chemical. Urea, as a non-hazardous ammonia production feedstock, has the same denitrification performance as liquid ammonia and is completely free of hazards and regulatory restrictions, allowing for convenient transportation, storage, and use.

[0003] Existing large-scale units use urea hydrolysis to produce ammonia for flue gas denitrification, with dilution air sourced from boiler hot primary air. As unit operating time increases, the air preheater leakage rate rises, leading to a continuous increase in dust content in the hot primary air. Furthermore, the dust content varies depending on the type of coal burned and operational adjustments. Prolonged operation can cause blockage of the ammonia outlet in the ammonia-air mixer. This blockage is not due to large dust particles, but rather to the accumulation and crystallization of fine dust, thus affecting the ammonia supply to the denitrification unit. Simultaneously, it causes problems such as blockage of the ammonia injection grid, insufficient denitrification unit capacity, and excessive nitrogen oxide emissions, potentially even forcing the denitrification unit to shut down. Summary of the Invention

[0004] This invention aims to solve the problem of dust in the dilution air of urea hydrolysis for ammonia supply during boiler denitrification, and provides a full-load urea hydrolysis denitrification and ammonia supply system that can simultaneously achieve NOx treatment at full load.

[0005] The technical solution adopted by this utility model is:

[0006] A full-load urea hydrolysis denitrification and ammonia supply dilution system is provided, including:

[0007] An air heating system is used to heat air and dilute hydrolyzed ammonia gas.

[0008] The mixing system is connected to the air heating system to mix heated air with unheated air and then mix it with hydrolyzed ammonia gas.

[0009] An automatic adjustment system is installed on the pipeline connecting the air heating system and the mixing system to adjust the ratio of heated air to cold air and regulate the temperature of diluted air.

[0010] Compared with the prior art, the present invention has the following advantages:

[0011] 1. This utility model can solve the problem of dust in the dilution air of urea hydrolysis for boiler denitrification, and at the same time can achieve the effect of NOx treatment at full load.

[0012] 2. Compared with conventional urea hydrolysis heat primary air as dilution air source, this utility model of SCR denitrification is safe, reliable and low-cost, and is suitable for large, medium and small boilers.

[0013] 3. By implementing this utility model, urea hydrolysis for ammonia dilution and NOx emission control can be achieved at full load. The equipment investment is low, the energy consumption is low, and the degree of automation is high. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the structure of this utility model;

[0015] The components include: 1. Fan; 2. Control valve one; 3. Gas-to-gas heat exchanger; 4. Control valve two; 5. Ammonia-air mixer; 6. Hydrolysis reactor; 7. Temperature measuring point one; 8. Temperature measuring point two; 9. Ammonia injection grid. Detailed Implementation

[0016] To better understand the purpose, structure, and function of this utility model, a more detailed description of this utility model will be provided below with reference to the accompanying drawings.

[0017] like Figure 1 As shown, this utility model provides a full-load urea hydrolysis denitrification and ammonia supply dilution system, including...

[0018] An air heating system is used to heat air to 200°C to dilute and heat hydrolyzed ammonia gas.

[0019] The mixing system is connected to the air heating system to mix heated air with unheated air and then mix it with hydrolyzed ammonia gas.

[0020] An automatic adjustment system is installed on the pipeline connecting the air heating system and the mixing system to adjust the ratio of heated air to cold air and regulate the temperature of diluted air.

[0021] This invention enables full-load urea hydrolysis for ammonia dilution and NOx emission control at ultra-low levels, with low equipment investment, low energy consumption, and a high degree of automation.

[0022] The air heating system includes a gas-to-gas heat exchanger 3 and two fans 1. The two fans 1 are arranged in parallel, one in operation and one on standby. The fans 1 are variable frequency Roots blowers. Two dilution air pipelines are connected in parallel at the outlets of the two fans 1. One pipeline connects to the gas-to-gas heat exchanger 3 inside the boiler, using the waste heat from the boiler's tail flue to heat the air, reducing the impact of primary air consumption fluctuations on the boiler and lowering energy consumption. After heat exchange in the gas-to-gas heat exchanger 3, the air temperature is heated to a maximum of 200℃. The other pipeline connects directly to the ammonia-air mixer 5 in the mixing system. Both pipelines are equipped with regulating valves and interlocked to control the flow rate of the two air sources. According to different loads, the two air sources are reasonably allocated to keep the dilution air temperature and flow rate at the inlet of the ammonia-air mixer within a reasonable range, avoiding excessively high temperatures in subsequent pipe sections that could lead to deformation. At the same time, it solves the problem of high dust content in the hot primary air clogging the ammonia-air mixer 5, the ammonia injection grid 9, and related system pipelines.

[0023] The mixing system includes an ammonia-air mixer 5, a hydrolysis reactor 6, and an ammonia injection grid 9; the hydrolysis reactor 6 is connected to the inlet of the ammonia-air mixer 5, and the outlet of the ammonia-air mixer 5 is connected to the ammonia injection grid 9.

[0024] A baffle plate is installed in the ammonia-air mixer 5 to uniformly mix the urea hydrolysis ammonia gas with the dilution air and maintain the temperature above 140℃. The gas is then injected into the reactor through the SCR ammonia injection grid 9 for flue gas denitrification reaction.

[0025] The automatic adjustment system includes regulating valve 2 and regulating valve 4. Regulating valve 2 and regulating valve 4 are respectively installed on the two dilution air ducts. Temperature measuring point 7 is installed at the outlet of the gas-gas heat exchanger 3. Temperature measuring point 7 is interlocked with regulating valve 2 for automatic adjustment. Temperature measuring point 8 is installed inside the ammonia-air mixer 5. Temperature measuring point 8 is interlocked with regulating valve 4 for automatic adjustment.

[0026] After passing through dilution fan 1, the air is split into two paths. One path enters the gas-to-gas heat exchanger 3 through regulating valve 1 2, and the other path enters through regulating valve 2 4. The air flow of the two paths is automatically interlocked and regulated by the temperature measuring point 1 7 at the outlet of the gas-to-gas heat exchanger 3 and the temperature measuring point 2 8 at the ammonia-air mixer 5. After the two paths merge, they enter the ammonia-air mixer 5 and are mixed with the hydrolyzed ammonia gas produced by the hydrolysis reactor 6. The mixture then enters the ammonia injection grid 9 and is injected into the denitrification SCR reactor to carry out the denitrification reaction with the flue gas.

[0027] It is understood that this utility model has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of this utility model. Furthermore, under the teachings of this utility model, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of this utility model. Therefore, this utility model is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the protection scope of this utility model.

Claims

1. A full-load urea hydrolysis denitrification and ammonia supply dilution system, characterized in that: include An air heating system is used to heat air and dilute hydrolyzed ammonia gas. The mixing system is connected to the air heating system to mix heated air with unheated air and then mix it with hydrolyzed ammonia gas. An automatic adjustment system is installed on the pipeline connecting the air heating system and the mixing system to adjust the ratio of heated air to cold air and regulate the temperature of the diluted air.

2. The full-load urea hydrolysis denitrification and ammonia supply dilution system according to claim 1, characterized in that: The air heating system includes a gas-to-gas heat exchanger (3) and two fans (1); the two fans (1) are arranged in parallel, and two dilution air ducts are connected in parallel at the outlets of the two fans (1), one of which is connected to the gas-to-gas heat exchanger (3) inside the boiler, and the other is connected to the ammonia-air mixer (5) of the mixing system.

3. The full-load urea hydrolysis denitrification and ammonia supply dilution system according to claim 2, characterized in that: The mixing system includes an ammonia-air mixer (5), a hydrolysis reactor (6), and an ammonia injection grid (9); the hydrolysis reactor (6) is connected to the inlet of the ammonia-air mixer (5), and the outlet of the ammonia-air mixer (5) is connected to the ammonia injection grid (9).

4. A full-load urea hydrolysis denitrification and ammonia supply dilution system according to claim 3, characterized in that: The automatic adjustment system includes regulating valve one (2) and regulating valve two (4); regulating valve one (2) and regulating valve two (4) are respectively installed on two dilution air ducts. Temperature measuring point one (7) is installed at the outlet of the gas-gas heat exchanger (3). Temperature measuring point one (7) is interlocked with regulating valve one (2) for automatic adjustment. Temperature measuring point two (8) is installed in the ammonia-air mixer (5). Temperature measuring point two (8) is interlocked with regulating valve two (4) for automatic adjustment.

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