- Model STACK 181 WS - Particulate Continuous Emission Monitor



The PCME STACK 181 WS is suitable for measuring particulate emissions from wet scrubbers and other processes where the flue gas falls below dew point (cold stack conditions) or water droplets are present. The extractive instrument takes a representative continuous sample from the stack, heats this well above dew point to evaporate water droplets and then measures the particulate concentration under dry conditions. This extractive approach with heating overcomes the problems of interference from condensation and water droplets associated with using in-situ particulate monitors after wet collectors.

The PCME STACK 181 WS uses an advanced ProScatter Forward Scatter sensor (PCME QAL 181) which is certified by TUV and MCERTS as QAL1 compliant. With certification ranges covering both 0-15mg/m3 and 0-100mg/m3, the sensor is suitable for monitoring the highly abated emissions found after Flue Gas Desulphurisation plant (FGD). The instrument is able to monitor saturated flue gas which is critical for the application of monitoring emissions from a coal fired power plant fitted with a wet FGD system and meets the requirements of PS-11 and EN 14181.

The patented ProScatter™ Forward Scatter technique measures the light scattered from a laser source in a near-forward direction by the particles, and results in an improved signal to noise ratio compared to other techniques, with excellent resolution and zero drift characteristics. This allows for high stability even at low concentrations (< 0.1 mg/m3) as well as rugged operation in stacks where emissions exceed 100 mg/m3.

  • Highly sensitive (<0.1mg/m3) and rugged instrument for measuring particulate concentrations in wet flues
  • Extensive system self-checks including vaporising chamber and sampling pump, with logging of Zero and Span check data for QAL3 reporting, manual audit functionality
  • Modular design to facilitate ease of assembly, servicing and lifting to stack location
  • Isokinetic sampling with automatic adjustment to maintain isokinetic conditions (requires input from external flow meter)

Two other versions of the Wet Stack Monitoring System are also available, the PCME QAL 181 WS and the PCME VIEW 181 WS. The PCME QAL 181 WS is certified by TUV to EN 15267-3 with QAL 1 as defined by EN 14181 with a certification range of 0 - 15 mg/m3. The PCME VIEW 181 WS is suitable for applications that do not require QAL 1 certification.

Resolution and Sensitivity

The PCME QAL 181 sensor within the PCME STACK 181 WS uses a low-angle forward light scattering measurement principle unique to PCME (see ProScatter Forward Scatter). The measured ‘cone’ of scattered light is larger than in typical light scatter instruments, which provides:

  • Excellent sensing resolution and sensitivity, due to an increased signal-to-noise ratio
  • Reduced cross-sensitivity to changing particle size, allowing a greater range of applications for which the instrument is suitable

System Self Checks

Flow rates and heater temperatures are continually monitored in the extractive flow line, to ensure any sample line blockages or problems with insufficient heating are automatically detected and avoided. The system automatically indicates when valid measurements are occurring, hence avoiding any measurement errors during any system warm up. In addition, trace heaters may be added to the intake air to ensure there is no risk of condensation in the pipes.

Modular Design and Ease of Maintenance

The system has been designed to facilitate ease of maintenance and cleaning of all major components, and the central control system records all critical measurements for rapid diagnosis of problems. The system can be isolated from the stack with a safety shut off valve and the vaporising chamber is easily accessed and cleaned by opening the hinged heater cover. The PCME STACK 181 WS is designed in a truly modular format for safety and ease of installation and maintenance, allowing parts to be replaced while still mounted on the stack.

Audit Tools & QAL3 Reporting

As an approved Particulate Measurement System for compliance monitoring, the PCME QAL 181 sensor within the PCME STACK 181 WS has fully automated self checks (Zero and Span) with a dedicated audit channel for QA data logging. This enables a simplified process for operators to meet QAL3 standards, with the option of PCME’s QAL Reporter PC software for automated QAL3 reporting in full compliance with EN 13284-2.

In addition to automatic self checks, the PCME STACK 181 WS has been designed for easy and safe operator access to the measurement volume for external auditing as required for the AST linearity test for EN 14181 compliance and absolute correlation audit for PS-11 compliance. The ProScatter™ 5-point Filter audit unit facilitates a comprehensive instrument check via a 5 point linearity check.

Process Conditions

The PCME STACK 181 WS is suitable for:

  • Stacks below dew point / with water droplets
  • After wet scrubber arrestment plant
  • After Flue Gas Desulphurisation (FGD) plant
  • Flue gas velocity range 1-20m/s
  • Corrosive flue gases (corrosion protection option)
  • Variable particulate size

Typical Applications

The PCME STACK 181 WS is used to monitor emissions from the following types of processes:

  • Coal and Oil fired power plant with FGD
  • Waste incineration plant with wet scrubbers
  • Pulp and paper recovery boilers
  • Metallurgical and chemical processes with wet scrubbers
  • Sugar beat dryers/boilers with high moisture in flue gas
  • Particle board and fibre drying

  • Approvals (181 sensor): QAL1 approved to EN 15267-3 (for EN 14181, EN ISO 14956) under MCERTS (performance standards for CEMs version 3 class 1) and TUV (BlmSch 17, 13, 27: latest revision)
  • PS-11 compliance under US EPA standards for PM CEMs
  • more on approvals
  • Certification Range:
    • 0-15 mg/m3
    • 0-100 mg/m3
  • Measurement Capability: 0-200 mg/m3
  • Detection Limit: 0.01 mg/m3
  • Air Purge Requirement: In-built
  • Stack Temperatures: 0-300°C

Sampling Probe

Flange 4” ANSI, with stub sloping 10° to 15° from horizontal into stack (options available on request)

Probe Length 1.2m from flange face (options available on request)

316 stainless, (corrosion resistance option available on request)

Stack temperature ranges 0-300°C

2m sample line length between sampling probe and analyser (options available on request)

Optional ball valve isolation between stack and analyser

Control Unit

230VAC (standard), 3.2kW (115VAC option)

Interfaces: Modbus RS485, isolated 4-20mA, Ethernet (option)

Data logging: Simultaneous recording of pulse data (for arrestment plant cleaning diagnostics), short term data (for process control), and long term data (for external emissions reporting), with dedicated QAL3 channel for logging of Zero & Span check data for compliance monitoring

Icon driven, multilingual menus for intuitive user interface, advanced graphical display and QA screens)

778 x 640 x 365 mm main enclosure, IP65, 120kg fully assembled.

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