Guide for selection of common laboratory analytical instruments and process analytical instruments

At present, there are two kinds of analytical instruments in the market: laboratory analyzer and process analyzer. Now, I will briefly introduce the instruments suitable for gas composition analysis.

one

Common laboratory analytical instruments

1. Austria gas analyzer

As a classical chemical manual analyzer, Austria’s gas analyzer has the advantages of low price, convenient operation and easy maintenance. This instrument has been widely used for the determination of CO2, O2, CO and H2 in gas. The principle is to use absorption method to determine acid gas, unsaturated hydrocarbon, oxygen and carbon monoxide, make hydrogen burn on copper oxide, and make saturated hydrocarbon burn on platinum wire and oxygen in air, and use weighing method to determine. Although the instrument is simple in operation and cheap in price, the accuracy of measurement is not very high. The accuracy depends on the proficiency of the operator, and the measurement data is not as intuitive and clear as LCD.

The main shortcomings of Austria gas analyzer in application are:

1) The volume of comb tube has an effect on the analysis results; 2) If ar cannot be analyzed, it is not suitable to analyze the circulating gas with the auxometer, and the gas chromatograph shall be used gradually; 3) It takes a long time to carry out hot work analysis and measurement with ostat, and sometimes there is a certain error. It is also necessary to pay attention to the completeness of chemical reaction, otherwise the reading is not allowed to mislead the production.

2. Trace sulfur analyzer

With the application of the new process of fine desulfurization at normal temperature, it is very necessary for Xiang nitrogen fertilizer plant to be equipped with a trace sulfur analyzer to ensure the safety of the combined alcohol catalyst and ammonia synthesis catalyst, and provide a convenient and fast detection method for the qualitative and quantitative detection of various trace forms of sulfur in the production sample gas.

3. Combustible gas explosion detector

It takes a long time to conduct hot work analysis and measurement with the ostium instrument, and sometimes there is a certain error. Therefore, it is recommended to select the combustible gas explosion detector.

4. Industrial gas chromatograph

Industrial gas chromatography is most widely used in gas analysis. The gas components are determined in the order of H2, N2, CO and CO2. In addition, the technology can also be used for the analysis of such components in converter gas and sintering waste gas. In recent years, the chromatographic analyzer has been popularized, but the chromatographic analyzer needs to separate the gas and then detect it, so it is difficult to realize real-time online. In addition to a few domestic blast furnaces still use this method, industrial gas chromatograph is gradually replaced by mass spectrometer or infrared analysis system.

5. Industrial gas mass spectrometer

The mass spectrometer uses the mass to charge ratio of material ions as a criterion for qualitative and quantitative analysis. Gas mass spectrometers usually ionize by electron bombardment, and all substances have characteristic dissociation modes. The mass spectrometer is characterized by extremely fast analysis speed, many components that can be analyzed simultaneously, and high analysis accuracy. However, the advantages of the multi-component and high-speed analysis performance of the mass spectrometer in the blast furnace, sintering and other sections are not obvious, and the gas needs to be separated and then detected. It is difficult to realize real-time online analysis, and the instrument cost is very high. At present, high-precision mass spectrometers mainly rely on imports, and their maintenance parts are also imported from abroad. Most domestic agents respond slowly, which has a great impact on the system utilization rate. In addition, the domestic operating environment is different from that of foreign countries, and the failure rate of the instrument is also very high. The maintenance is quite frequent and the maintenance cost is also large.

6. Others

Other commonly used instruments include conductivity meter, acidity meter, spectrophotometer, moisture meter, etc.

two

Common process analysis instrument

1. Trace gas analyzer

The determination of trace (CO + CO2) in refined gas is an important analysis item in nitrogen fertilizer plants. Due to the low content (CO + CO2 ≤ 25 × 10-6). In some cases, the gas content is even low at ppb level, and it is difficult to measure its composition by manual method.

2. Thermal conductivity analyzer

Thermal conductivity analyzer is a kind of on-line analyzer with the earliest appearance, many kinds and wide application. It is often used to automatically determine the volume fraction of H2, AR, SO2 and other gases in the mixed gas.

3. Oxygen analyzer

Electrochemical or thermal magnetic oxygen analyzer is often used for on-line analysis of oxygen content in coal gas. It has high sensitivity and can also be equipped with alarm device to facilitate maintenance and replacement.

4. Constant infrared gas analyzer

Constant infrared gas analyzer is often used to continuously determine the content of CO, CO2, NH3, CH, H2, O2, etc. in various mixed gases. It is an important type of on-line analyzer. As a fast and accurate gas analysis technology, non spectral infrared (NDIR) gas analyzer is widely used in continuous pollutant monitoring system (CEMS) and vehicle exhaust gas detection. Most of the major manufacturers of NDIR gas analyzers in China adopt the international infrared gas analysis method in the early 1980s, such as using nickel nickel wire as the infrared light source, using the motor to mechanically modulate the infrared light, and using the thin film capacitor microphone or InSb as the sensor. Due to the mechanical modulation of the motor, the instrument has high power consumption, poor stability and high cost. At the same time, the use of thin film capacitance microphone as a sensor makes the instrument very sensitive to vibration, so it is not suitable for portable measurement.

With the development of infrared light source, sensor and electronic technology, NDIR infrared gas sensor has been developed rapidly at home and abroad. It is mainly manifested in the absence of mechanical modulation device, the use of new infrared sensor and electric modulation light source, and the use of Low-Power Embedded System in the instrument circuit, which makes the instrument have incomparable advantages in volume, power consumption, performance and price.

For example, the gas analyzer gasboard-3100 (online type) on the market now adopts the internationally advanced non spectroscopic infrared gas analysis technology, long-life electrochemical sensing technology, and MEMS based thermal conductivity technology. It can simultaneously measure the calorific value of gas and biogas, as well as the volume concentration of CO, CO2, CH4, H2, O2, CnHm and other gases. This instrument is widely used to measure the volume concentration of multicomponent gas in the process gas of gas industry, such as the gas of nitrogenous fertilizer plants, steel companies, gas plants, semi water gas, shift gas, feed gas, etc. Through the analysis of the change of measured gas parameters, the change law of these components can be mastered, so as to realize the dynamic monitoring of the whole production process.

“Instrumentation of analytical technology and automation of analytical instruments” is the leading development direction. Analytical methods and technologies are the guidance of analytical instruments, and finalized analytical and testing methods need to be transformed into instrument devices. With the continuous development of production, the requirements for the quality and performance of analysis are also improving. The laboratory analyzer can not adapt to the continuous and automatic production monitoring and control. In addition to using the currently developed electronic technology and computing technology to realize the automation of analytical instruments, it is also necessary to comprehensively use the popular embedded intelligent platform technology and ultra precision machining technology. Process analyzer is gradually popularized in small and medium-sized enterprises in China, providing dynamic control and monitoring for enterprise production in real time.