The main advantages of process mass spectrometers

Process mass spectrometers, also known as online mass spectrometers, enable rapid and multi-component analysis, with a single instrument capable of measuring all components to be analysed within a process. Some users in the steel industry have found that process mass spectrometry not only enables the analysis of gaseous components within a process, but also provides further information for process control. For example, by using a tracer gas—introducing helium at a known flow rate and then measuring its concentration—it is possible to calculate the total gas flow rate. In the decarburisation process, for instance, the amount of decarburisation can be calculated with precision.

Owing to the clear advantages of mass spectrometry in gas analysis within the steel industry, many engineering firms involved in the construction and modernisation of steelworks are incorporating process mass spectrometers into their designs as the instrument of choice for gas analysis.

Rapid online gas analysis using mass spectrometry is widely applied in the steel industry to achieve better process control, reduce costs, ensure products meet specifications, determine end points and improve processes.

Automated control measures, such as online instrumentation, can optimise production stages and improve product quality and quantity, thereby achieving the objectives of conserving resources and reducing energy consumption. They have become indispensable tools for analysis, measurement and control in the production management and operations of modern industry, particularly in the petrochemical sector.

Among these, mass spectrometers have become a crucial analytical and measurement instrument in the petrochemical industry due to their high degree of automation, wide measurement range, rapid analysis speed, and excellent instrument stability and reliability.

In the petrochemical sector, mass spectrometry technology is indispensable for a wide range of applications, from the analysis of biomarkers in crude oil and source rocks to the analysis of the chemical composition of crude oil and petroleum products. This article introduces the principles and characteristics of mass spectrometers, cites several examples of process mass spectrometer applications in the petrochemical industry, and briefly outlines the current status of domestically produced process mass spectrometers.

Optimising Processes through Rapid Analysis Using Online Mass Spectrometers

Online mass spectrometers are primarily used in ethylene glycol plants, ammonia and methanol plants employing the water-coal slurry pressurised gasification process, acetic acid plants

and applications involving substances such as acrylonitrile, where reactions are vigorous and rapid online analysis is required. Other applications include ethylene cracking, catalytic cracking, ethylene oxide, polyethylene and propylene.

Main substances detected:

H₂O, O₂, CO₂, N₂, Ar, CO, methane, ethylene, ethane, propylene, etc.

① On-site process monitoring: Capable of simultaneously analysing over 100 process points, with each monitoring point capable of analysing more than 10 components simultaneously;

② Sample pre-treatment system: Performs pre-treatment on each monitoring flow path, such as pressure reduction, filtration, flow stabilisation, flow rate alarms, and

switching, etc., to ensure they meet the requirements of mass spectrometry analysis;

③ Mass spectrometer: Analyses the sample components in the flow path and transmits the corresponding signals in real time to the remote data station for analysis and calculation;

④ Remote data station: This is the core of the entire analytical system; it primarily calculates and processes the analytical signals received from the mass spectrometer,

sends various control signals to the mass spectrometer, feeds back calculation results to the digital input/output unit, and can be remotely monitored by the remote DCS;

⑤ Digital input/output unit: Receives data from the data station and transmits it to the remote DCS system, whilst also forwarding

received external data to the remote data station;

⑥ Remote DCS: Receives analysis data from the digital input/output unit and enables remote monitoring of the remote data station,

facilitating emergency operations by the user.

Analysis of Test Results

Taking the synthetic ammonia process as an example, the test results are analysed. Before evaluating the test results, the test data must first be

. Figure 7 shows the background noise signal measured when pure Ar was introduced. During the ionisation process, Ar produces fragment ions m/z 40 and m/z 20; as can be seen from the spectrum, the signals at these two points are relatively strong, whilst signals elsewhere are all background noise. Notable examples include m/z 2, m/z 18, m/z 28, m/z 32 and m/z 44. For the quantitative ions selected above, it is sufficient to focus solely on the background noise signals at m/z 2, m/z 15, m/z 17 and m/z 28. Figure 8 shows a spectrum of ion signal intensities generated by introducing a sample gas of a specific concentration. In this spectrum, the signal intensities of different fragment ions with the same mass-to-charge ratio are superimposed; for example, the signal from the m/z 15 fragment ion produced by the ionisation of NH₃ is superimposed upon the signal from the m/z 15 fragment ion produced by the ionisation of CH₄. These signals must be separated through data processing to calculate the signal intensities of the fragment ions produced by each component, which are then converted into information on sample concentration.

As shown in Table 4, the relative error in the quantitative analysis of process gases using mass spectrometry is within 1.0 per cent; this measurement error is

entirely within the permissible range for process control and meets the control accuracy required by the process. Its analytical characteristics—rapid, multi-channel, multi-component, high-precision and high-stability—effectively compensate for the shortcomings of other quantitative analytical instruments in industrial processes.

Conclusion

As an effective means of online analysis in industrial processes, quantitative analysis by mass spectrometry has inherent advantages over instruments such as chromatographs and infrared analysers. 

Its analytical characteristics—rapid, multi-channel, multi-component, high-precision and high-stability—lend greater significance to its successful application. The successful implementation of quantitative mass spectrometry methods has played a positive role in promoting the development and widespread adoption of domestically produced mass spectrometers, whilst also facilitating the optimisation of industrial process control, leading to more rational resource allocation and improved production efficiency.