AMETEK Ratio Analyzer Model 888

Overview

The AMETEK Ratio Analyzer Model 888 is a dedicated, extractive gas analyzer engineered for continuous, real-time measurement of the hydrogen sulfide to sulfur dioxide (H₂S/SO₂) molar ratio in tail gas streams from Claus sulfur recovery units (SRUs). Operating on the principle of dual-channel ultraviolet (UV) absorption spectroscopy, the Model 888 simultaneously quantifies H₂S and SO₂ concentrations at their distinct, non-overlapping absorption bands—typically near 185 nm for H₂S and 280–320 nm for SO₂—enabling high-selectivity, interference-resistant ratio calculation. Accurate H₂S/SO₂ stoichiometric control is critical to achieving optimal Claus reactor conversion efficiency (>95%) and minimizing sulfur emissions; deviations from the ideal ~2:1 ratio directly correlate with reduced sulfur yield and increased SO₂ slip. The Model 888 delivers stable, low-drift performance under demanding refinery or gas processing plant conditions, supporting closed-loop air-to-acid gas ratio control strategies required for modern SRU optimization.

Key Features

• Dual-beam UV photometric detection architecture with temperature-stabilized light sources and reference-path compensation to minimize drift from lamp aging or optical fouling
• Integrated sample conditioning system including heated sample line (up to 180 °C), particulate filtration, moisture removal via Nafion® membrane dryer, and pressure regulation—designed for wet, corrosive, and particulate-laden tail gas
• Automatic zero/span calibration capability using certified H₂S and SO₂ standard gases, configurable for daily or event-triggered sequences
• Robust 19-inch rack-mount enclosure rated IP65 for hazardous area installation (Class I, Division 2, Groups B, C, D per NEC/CEC); optional ATEX/IECEx certification available
• Real-time ratio output (H₂S/SO₂) as 4–20 mA analog signal plus Modbus RTU/TCP digital interface for integration into DCS or SIS systems
• Onboard data logging with 30-day buffer memory and timestamped event records (e.g., calibration, alarm, maintenance)

Sample Compatibility & Compliance

The Model 888 is validated for use with typical Claus tail gas compositions containing 10–200 ppmv H₂S, 5–150 ppmv SO₂, 0–5% H₂O, <10 ppmv COS/CS₂, and trace hydrocarbons. It complies with applicable sections of API RP 556 (Instrumentation and Control Systems for Petroleum Processing Plants) and meets functional safety requirements per IEC 61511 for SIL 2 applications when configured with redundant sensors and voting logic. All wetted materials—including 316L stainless steel sample path, Hastelloy C-276 flow cells, and fluoropolymer seals—are selected for resistance to sulfuric acid condensate and elemental sulfur deposition. The analyzer supports audit-ready operation under refinery QA/QC programs aligned with ISO 9001 and API RP 2000.

Software & Data Management

Configuration, diagnostics, and historical trending are managed via the AMETEK AnalyzerSuite™ web-based interface accessible through any standards-compliant browser. The software provides full access to raw absorbance signals, calibration logs, alarm history, and diagnostic status (e.g., lamp intensity, cell temperature, flow rate). Data export is supported in CSV format with UTC timestamps, and secure remote access can be enabled via TLS 1.2–encrypted connections. For regulated environments, AnalyzerSuite™ supports electronic signature workflows, user role-based permissions (admin/operator/viewer), and audit trail generation compliant with FDA 21 CFR Part 11 requirements—including immutable records of all configuration changes and calibration events.

Applications

• Real-time H₂S/SO₂ ratio monitoring and feedback control in Claus plant main and tail gas treatment units
• Optimization of air blower setpoints to maintain stoichiometric balance across varying feed gas compositions
• Performance verification of SCOT, SuperClaus®, or LO-CAT® tail gas treating units
• Compliance reporting for EPA 40 CFR Part 60 Subpart J and EU Industrial Emissions Directive (IED) Annex I emission limits
• Troubleshooting catalyst deactivation, thermal reactor upsets, or amine stripper carryover through ratio trend analysis

FAQ

What is the typical response time (T90) for H₂S and SO₂ measurements?
Typical T90 is ≤ 30 seconds from sample inlet to validated concentration output, assuming nominal sample flow of 1.0 L/min and conditioned gas at 40 °C.
Does the Model 888 require periodic replacement of optical components?
UV lamps are rated for ≥ 12 months of continuous operation; quartz windows and flow cells are designed for >5 years service life under proper sample conditioning—no routine optical part replacement is specified.
Can the analyzer operate without external calibration gases?
While zero calibration may be performed using nitrogen purge, span calibration requires certified H₂S and SO₂ standards; automated calibration is recommended at least weekly for regulatory compliance and process reliability.
Is the Model 888 compatible with third-party DCS platforms such as Emerson DeltaV or Honeywell Experion?
Yes—native Modbus TCP support enables seamless integration; optional OPC UA drivers and certified DCS-specific interface modules are available upon request.
How does the analyzer handle sulfur dew point fluctuations in the sample stream?
The heated sample transport system maintains gas temperature above the local sulfur dew point (typically >140 °C), preventing condensation and ensuring representative gas-phase measurement integrity.