Introduction to SCR Denitrification Process Equipment for Lime Shaft Kiln Flue Gas:

The SCR (Selective Catalytic Reduction) denitrification process equipment for lime shaft kiln flue gas is a key system used to treat nitrogen oxides (NOx) in the flue gas emitted from lime shaft kilns. Its core function is to convert NOx into harmless nitrogen (N?) and water (H?O) through the action of a catalyst and a reducing agent (such as ammonia water or urea). The following are the main components and functions of this process equipment:

I. Core Equipment Components

1. Flue Gas Preheating System
   • Function: Preheats low-temperature flue gas (typically at a low temperature, requiring preheating to the catalyst's suitable reaction temperature range, generally 200-400°C).
   • Equipment: Heat exchangers (such as gas-gas heaters, GGH) or burner-assisted heating.
   • Importance: Ensures the flue gas temperature reaches the SCR catalyst's active window, improving denitrification efficiency.
2. Reducing Agent Storage and Supply System
   • Function: Stores and quantitatively delivers the reducing agent (e.g., 20%-25% concentration ammonia water or urea solution).
   • Equipment: Ammonia water storage tanks, urea dissolution tanks, metering pumps, delivery pipelines, and safety protection devices (such as ammonia leakage alarms).
   • Features: Requires anti-corrosion and anti-leakage design to ensure stable reducing agent supply.
3. Reducing Agent Injection System
   • Function: Atomizes the reducing agent and evenly sprays it into the flue, ensuring thorough mixing with the flue gas.
   • Equipment: Spray guns (e.g., dual-fluid spray guns), mixers, distribution modules.
   • Key Points: Injection angle and coverage must be precisely controlled to avoid localized ammonia slip.
4. SCR Reactor
   • Function: Provides a reaction space for the catalytic reduction of NOx and the reducing agent on the catalyst surface.
   • Equipment: Reactor body (containing catalyst modules), rectifying grids, guide vanes.
   • Catalyst: Typically uses honeycomb or plate-type catalysts with active components such as V?O?-WO?/TiO?. Sulfur-resistant and anti-poisoning catalysts are selected based on flue gas conditions.
5. Catalyst Regeneration or Replacement System
   • Function: Periodically treats deactivated catalysts or replaces them with new ones.
   • Equipment: Regeneration devices (e.g., thermal desorption furnaces) or catalyst hoisting equipment.
   • Cycle: Catalyst lifespan is generally 2-4 years, requiring evaluation based on operating conditions.
6. Denitrification Byproduct Treatment System
   • Function: Treats byproducts such as ammonium sulfate generated during the reaction to avoid clogging or corrosion.
   • Equipment: Demisters, scrubbers (optional), byproduct collection devices.
7. Control System
   • Function: Monitors and adjusts parameters such as flue gas temperature, flow rate, NOx concentration, and reducing agent injection volume in real time.
   • Equipment: DCS (Distributed Control System), CEMS (Continuous Emission Monitoring System), ammonia slip monitors.

II. Process Flow

1. Flue Gas Preheating: Low-temperature flue gas is heated to 200-400°C via heat exchangers or burners.
2. Reducing Agent Injection: Ammonia water or urea solution is atomized and injected into the flue, mixing with the flue gas.
3. Catalytic Reduction: The mixed gas enters the SCR reactor, where the reaction occurs on the catalyst surface:
   4NO + 4NH? + O? → 4N? + 6H?O
   6NO? + 8NH? → 7N? + 12H?O
4. Byproduct Treatment: Byproducts such as ammonium sulfate generated during the reaction are collected via demisters or scrubbers.
5. Purified Flue Gas Emission: The treated flue gas is discharged in compliance with standards (NOx concentration typically below 50 mg/Nm3).