METSO AO4H

Description

Technical Specifications:

• Measurement Principle: Prompt Gamma Neutron Activation Analysis (PGNAA)
• Measured Elements: Ash-forming elements including Si, Al, Fe, Ca, Ti, Mg, K, Na, S, Cl
• Measurement Range: 0–50% ash content (adjustable per application)
• Accuracy: ±0.5% absolute ash (typical, depending on coal type)
• Response Time: 30–60 seconds for full measurement cycle
• Source: Americium-241/Beryllium (Am-241/Be) neutron source, sealed and shielded
• Detector: BGO (Bismuth Germanate) scintillation detector or HPGe (High Purity Germanium) in some configurations
• Operating Temperature: -20°C to +55°C (analyzer housing); source and detector rated for boiler environment
• Power Supply: 230 VAC ±10%, 50/60 Hz, or 110 VAC variants available
• Output Signals: 4–20 mA analog, Modbus RTU/TCP, HART protocol
• Communication: OPC-UA compatible, Ethernet/IP option available
• Mounting: Flange-mounted or wall-mounted on duct/conveyor, source and detector mounted opposite each other across the fuel stream

Functional Features:

• Fully non-contact measurement — no intrusion into the fuel stream
• Continuous real-time ash measurement
• Automatic calibration via built-in reference system
• Self-diagnostics and source health monitoring
• Dust-compensated measurement algorithm
• Remote configuration and data access via web interface

Structural Characteristics:

• Source housing: Stainless steel 316L, double-encapsulated Am-241/Be source
• Detector housing: Stainless steel 316L with lead/borated polyethylene shielding
• Electronics enclosure: IP65-rated stainless steel cabinet
• Measurement path: Source and detector mounted on opposite sides of duct or conveyor belt
• Cable lengths: Up to 100 m from detector/source to electronics (standard)

Working Principle: Neutrons from the Am-241/Be source irradiate the fuel passing through the measurement zone. Elements in the fuel emit characteristic prompt gamma rays upon neutron capture. The BGO or HPGe detector measures the gamma ray energy spectrum. The intensity of element-specific gamma peaks is proportional to the concentration of each element. A multi-element regression algorithm converts the spectral data into total ash content.

Advantages:

• No moving parts in the measurement zone — zero maintenance in the duct
• Unaffected by fuel moisture, particle size, or flow rate variations
• No radioactive waste generated during normal operation
• Proven technology with over 20 years of field deployment
• Compliant with IEC 61508 SIL 2 safety rating

Applicable Industries: Coal-fired power plants, biomass power plants, cement plants with coal/biomass firing, waste-to-energy plants

Installation Requirements:

• Requires regulatory license for radioactive source (national nuclear authority)
• Flange mounting on duct or conveyor: DN200–DN1200 (custom sizes available)
• Source and detector must have clear line-of-sight across the full fuel stream
• Minimum 300 mm straight duct section upstream and downstream
• Grounding and shielding per local radiation safety regulations

Usage Precautions:

• Source replacement requires licensed radiation safety personnel only
• Annual source leak test mandated by regulatory authority
• Do not disassemble source or detector housings
• Maintain minimum safe distance per regulatory limits during maintenance
• Calibration verification recommended every 6 months