Commissioning and Operation of SCR Denitration System for Small Coal-fired Boiler Flue Gas Emissions

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The SCR (Selective Catalytic Reduction) denitration system for small coal-fired boiler flue gas emissions, supplied by Hebei Hanlan for an energy company, has been successfully commissioned. The initial NOx concentration in the boiler flue gas was 150-200 mg/Nm³ (at 5-8% O₂). After the installation of the denitration system, the NOx concentration of the flue gas was reduced to ≤50 mg/Nm³ (at 15% O₂), achieving compliance with emission standards.

This SCR denitration project uses an aqueous ammonia solution as the reducing agent. The flue gas denitration system mainly consists of:
Ammonia storage tank system
SCR reactor
Control system
Reducing agent supply system
Injection system

Related auxiliary systems

To ensure the hot commissioning and trial operation of the boiler flue gas denitration equipment proceed with high quality, order, punctuality, safety, efficiency, and proper management, Hebei Hanlan developed a specialized commissioning plan. After the complete installation of the SCR denitration equipment and the completion of individual and subsystem trial operations, hot commissioning and continuous trial operation will verify the rationality of the design, construction, and equipment quality.

Through commissioning, the operating conditions of the scr system and its components will be adjusted to provide a basis for establishing operational procedures, ensuring the system meets denitration requirements in a highly cost-effective manner. The process will also verify whether the scr system meets the technical specifications outlined in the design and contract. The adjustments and tests will evaluate:

（1）Whether the denitration system design is reasonable;

（2）The denitration efficiency of the scr system, as well as methods for hot commissioning and shutdown;

（3）The influence of various operating parameters on SCR denitration performance;

（4）The optimal operating mode specifically suited for this scr system.

Based on the characteristics of the denitration system startup and the actual conditions of this project, the commissioning process is divided into two phases:

（1）Subsystem trial operation (individual and subsystem testing)，Subsystem trial operation refers to the commissioning work from the completion of equipment installation until the full-system startup begins.
（2）Full-system startup trial operation (including full-system startup commissioning and continuous trial operation)，Full-system startup trial operation involves the startup, operation, and adjustment of the denitration system after subsystem testing, fine-tuning parameters to achieve stable full-load operation as designed.

During the commissioning and operation of the denitration system, any abnormalities must be promptly analyzed and addressed, including:

1. Pump and Valve Maintenance
If a pump fails to start, check whether the ammonia tank liquid level is too low.
Ensure the power switch in the distribution cabinet is closed and supplying electricity.
Confirm that the inlet and outlet pipeline valves of the pump are open.

2. Spray Gun Maintenance
During spray gun operation, monitor the atomizing air pressure gauge to ensure the pressure transmitter maintains 0.4 MPa and airflow is unobstructed.
If the metering pump triggers pressure protection, the spray nozzle may be clogged.

If clogging occurs, use a sharpened wire to clear the spray gun pipeline, clean or replace the nozzle.

Additionally, since this SCR denitration project uses aqueous ammonia as the reducing agent, the following safety measures must be implemented:

1. Emergency Leak Handling
Isolate the contaminated area and restrict access.
Emergency personnel should wear chemical safety goggles and general work clothing.
Avoid direct contact with the leaked material.
For minor leaks, flush with water immediately.
For major leaks, use sand, vermiculite, or other inert materials to absorb the spill, then contain it with barriers for collection, transfer, recycling, or safe disposal.

2. Protective Measures
Eye protection: Wear chemical safety goggles.
Body protection: Wear work clothing.
Hand protection: Use chemical-resistant gloves.
Other precautions: No smoking, eating, or drinking in the work area. Shower and change clothes after work to maintain good hygiene.

3. First Aid Measures
Skin contact: Rinse immediately with water if ammonia solution contacts the skin.
Eye contact: Lift eyelids and rinse with running water or saline, then seek medical attention immediately.

The commissioning and operation of the denitration system aim to ensure the entire system can start safely and smoothly, identify and resolve potential issues, and enable stable and safe operation after commissioning. This will maximize investment returns and contribute to environmental protection efforts as intended.