Thermo Scientific™ Prima PRO Process Mass Spectrometer - Improving process control and efficiency in Ammonia production

Importance of the topic

Ammonia production is a cornerstone of global chemical and agricultural industries, predominantly serving fertilizer manufacture and a range of industrial chemicals. Because the process consumes large quantities of natural gas and steam and operates under tight catalytic and energy constraints, precise, fast and multi-stream gas analysis is essential to maximize yield, reduce energy consumption and prevent catalyst damage. Online, high-frequency composition data enable dynamic control of reforming, shifting, methanation and synthesis steps, directly affecting operating costs and plant availability.

Objectives and study overview

This application note presents how a magnetic-sector process mass spectrometer (Prima PRO) combined with a Rapid Multistream Sampler (RMS) and supporting software can meet ammonia-plant analytical needs. The document outlines the analytical challenges across reformer, shift, methanator and synthesis sections, demonstrates instrument performance (speed, precision, linearity, contamination resistance) and describes how derived values and integration into control systems improve process control (steam-to-carbon, air requirement, methane slippage, H/N ratio and inert accumulation). Independent evaluation and start-up validation are also summarized.

Methods and instrumentation

The analytical approach is based on online process mass spectrometry using a magnetic-sector analyzer (Prima PRO) for rapid, multi-component gas analysis. Key instrument and system elements described include:

• Prima PRO magnetic-sector mass spectrometer with a high-energy (1000 eV) enclosed ion source designed for high sensitivity, low background and resistance to contamination.
• Rapid Multistream Sampler (RMS) enabling software-controlled selection from up to 32 or 64 sample streams, optically encoded position feedback, and heated sampling to 120°C. RMS records sample flow digitally for each stream.
• GasWorks software for quantitative analysis, unlimited derived-value calculations (e.g., S/C ratio, H/N ratio), and communication with DCS using industry-standard protocols.
• Optional integration of an external NDIR CO analyzer for low-level CO measurement in the Low Temperature Shift (LTS) effluent, where spectral overlap reduces MS precision.

Main results and discussion

Analytical performance and process impact reported in the note include:

• Fast multi-point analysis: typical analysis cycle of 20 seconds per stream (including switching), enabling frequent monitoring across the process train.
• High precision: single-run analytical precisions (one standard deviation) vary by component and stream but typically lie in the 0.001–0.03% mol range for major species and ppm-level precision for certain trace targets. Magnetic-sector precision is reported as 2–10× better than quadrupole instruments in comparable conditions.
• Low-level CO in LTS: due to spectral overlap with CO2 and N2, CO detection limit in the LTS outlet is approximately 0.3% mol with a standard deviation of 0.02% mol. For reliable sub-percent CO control at LTS outlet, the note recommends a dedicated NDIR analyzer integrated via the RMS sample loop, with the MS providing backup alarm capability.
• Linearity and calibration: an independent evaluation (EffecTech) calibrated Prima PRO with a single sensitivity gas and validated linearity across nine reference mixtures, demonstrating superior linearity compared to a TCD-based GC for complex mixtures.
• Process control improvements illustrated by H/N ratio data: after implementing control changes guided by Prima PRO measurements, the average H/N ratio moved from 2.824 to 2.991 while the standard deviation fell from 0.015 to 0.001 (relative standard deviation improving from 0.5% to 0.05%). This demonstrates tighter stoichiometric control and potential yield and energy benefits.

Benefits and practical applications of the method

Primary benefits and applications for ammonia plants include:

• Comprehensive multi-stream, multi-component monitoring (C1–C5 hydrocarbons; H2, N2, NH3, CO, CO2, O2, Ar, H2S) with a single analyzer.
• Rapid data for dynamic control loops (steam-to-carbon ratio, air/fuel control, methanator performance, H/N ratio optimization, inert buildup monitoring).
• Improved measurement precision and stability that reduce calibration frequency and enhance the reliability of model-based control actions.
• Ability to monitor catalyst performance and detect signs of deterioration earlier to optimize outage scheduling.
• Flexible software-derived calculations and DCS integration for automated process optimization and alarm management.

Used instrumentation

The note explicitly describes the following instrumentation and accessories used in the application:

• Thermo Scientific Prima PRO process mass spectrometer (magnetic-sector, 1000 eV ion source).
• Rapid Multistream Sampler (RMS) for 1-of-32 or 1-of-64 stream selection with heating and optical encoder.
• GasWorks quantitative software for data processing, derived calculations and plant integration.
• Optional Non-Dispersive Infra-Red (NDIR) CO analyzer integrated via RMS for low-level CO measurement.
• Standard service kit and maintenance tools supplied for onsite servicing; instrument covered by a three-year parts and labor warranty.

Future trends and applications

Key future directions and potential uses include:

• Greater adoption of high-precision MS combined with multistream sampling to support advanced model-predictive control and tighter energy optimization across synthesis plants.
• Hybrid measurement strategies combining MS for broad compositional coverage and fast trending with specialized sensors (NDIR, electrochemical) for trace-species where spectral interference limits MS performance.
• Enhanced digital integration: richer derived metrics, real-time analytics and cloud-enabled historical trending to support predictive maintenance and long-term optimization of feedstock and catalyst usage.
• Broader application to alternative feedstocks (e.g., coal gasification, biogas, hydrogen-rich feeds) where rapid compositional variability requires flexible, multi-component online analysis.

Conclusion

Magnetic-sector process mass spectrometry coupled with a rapid multistream sampler addresses the major analytical challenges of ammonia production by providing fast, accurate, contamination-resistant, multi-point gas composition data. This capability supports improved control of steam-to-carbon ratio, methanation, shift stages and the H/N stoichiometry, reducing energy use and improving yield. For low-level CO in the LTS effluent, MS accuracy is limited by spectral overlap and a complementary NDIR sensor is recommended. Overall, the combined system enables tighter process control, reduced operating cost and more informed maintenance planning.

References

1. U.S. Geological Survey, Mineral Commodity Summaries, January 2017.
2. Chemical Economics Handbook – Ammonia, July 2017.