Catalytic Combustion Methane Sensors: Principles, Applications & Industrial Safety Solutions

Methane (CH₄) is a colorless and odorless gas that plays a significant role in the energy sector and environmental science. The following introduces the catalytic combustion methane sensor.

Principle of catalytic combustion

Catalytic combustible gas sensors utilize the thermal effect principle of catalytic combustion. They are typically composed of a sensor head, a circuit board, and connecting wires etc.

The measurement bridge is made up of two components: a detection plate (D) that reacts with methane and a compensation plate (C) that does not react with methane gas.

Under certain temperature conditions, Methane gas undergoes flameless combustion on the surface of the detection element carrier and under the action of a catalyst. As a result, the temperature of the carrier rises, and the resistance of the platinum wire passing through it also increases accordingly. This causes the balance bridge to lose balance and output an electrical signal proportional to the concentration of methane gas. On the contrary, since the compensating sheet does not burn, its resistance does not change (Figure 1).

Circuit Testing and Output - Concentration Conversion

The components form the Wheatstone bridge circuit (Figure 2). In an environment where there is no methane gas, the variable resistor (VR) can be adjusted to keep the bridge circuit in a balanced state.

When the gas sensor is exposed to flammable gas, only the resistance of the detection plate rises and the balance of the bridge circuit is disrupted. This change is manifested as an unbalanced voltage (Vout) and can be detected. There exists a proportional relationship between this unbalanced voltage and the gas concentration as shown in Figure 3, and the gas concentration can be detected by measuring the voltage.

The catalytic combustion principle is mainly used for the detection of combustible gases. It features good linearity of output signals, reliable index, low cost, and no cross-infection with other non-combustible gases.

Catalytic combustion sensors are the most common technology for detecting flammable gases, whether for organic or inorganic gases, to monitor the concentration of flammable gases in the surrounding air within the range of 0 to 100% of the lower explosive limit.

It has a wide range of applications and is hailed as an "impeccable sensor", having a good response to both alkane and non-alkane flammable gases. It is regarded as an industrial standard for combustible gas detection, and its reliability and excellent on-site working performance have earned it a high reputation. Its flexibility and low cost in installation and maintenance make it more acceptable. The calibration cycle of the catalytic combustion probe sensor is 90 to 180 days.

Characteristics of catalytic combustion methane sensors

1. It can alarm for the content of flammable gas in the air below the lower explosive limit concentration.

2. Catalytic combustion gas sensors can detect most flammable gases. For gases that cannot be burned, the sensors have no response at all.

3. The catalytic combustion sensor has a very simple structure, low replacement and maintenance costs, and a long service life.

4. The sensor output is basically not directly affected by water vapor and is not sensitive to the direct influence of environmental temperature and humidity.

5. The output signal achieves linearity - especially with a linearity of less than 60% LEL.

Disadvantages of catalytic combustion methane sensors

1. The combustion values of different combustible gases vary. The sensor measures the resistance change caused by combustion rather than the concentration change. Therefore, even at the same concentration, the readings of different combustible gases may still be different.

2. Components are directly affected by sulfides, halogen compounds, etc., which significantly reduces their service life.

3. The working temperature is high. The surface temperature of the detection component is usually between 200 and 300℃, and the internal temperature can reach up to 700 to 800℃. It cannot be made into a cost-safe explosion-proof structure and can only be made into an isolated explosion-proof structure.

4. When using a combustible gas alarm for detection in an oxygen-deficient environment, the indication value error is relatively large. 

To enhance the performance of catalytic combustion gas sensors, researchers have been constantly optimizing the formulation and preparation process of catalysts. For instance, by adding different metal oxides or precious metals, the activity and selectivity of the catalyst can be enhanced. By altering the morphology and structure of the catalyst, its surface area and the number of catalytic active sites can be increased. In addition, some new types of catalytic combustion gas sensors have adopted advanced technologies such as nanotechnology and optoelectronics, further enhancing the performance and application scope of the sensors.

Introduction to Catalytic Combustion Methane Gas Sensor

The most widely used and detected gas by catalytic combustion gas sensors is methane, and the application scenarios of catalytic combustion methane sensors are numerous in both daily life and industrial applications. Methane (CH₄) is a highly flammable, colorless and odorless gas. It is a potent greenhouse gas that has a significant impact on the environment. If not monitored properly, it may cause major safety risks. Methane sensors play a crucial role in ensuring safe, environmentally friendly and efficient industrial operations.

Application of methane sensors

1. Safety in industrial environments

By detecting and monitoring methane leaks, explosions are prevented and the safety of workers in industries such as mining, oil and gas, and chemical manufacturing is ensured.

2. Environmental monitoring

Track methane emissions from natural resources (such as wetlands and livestock) and human activities (such as landfill sites and fossil fuel extraction) to address environmental and climate change issues.

3. Home safety

Detect methane leakage from natural gas appliances to ensure a safe living environment.

4. Industrial process

Ensure the normal operation, safety and efficiency of industrial processes that utilize or produce methane.

5. Agricultural sector

Monitor methane emissions from agricultural activities (including animal husbandry) to manage and reduce greenhouse gas emissions.

Product Recommendation

Here is the product information of EURsense's catalytic combustion gas sensors.

Equipped with the British Alphasense CH-A3 catalytic combustion methane sensor module (CH4) - AG-3-CHx-CHA3(D):

The AG-3-CHX-CHA3 sensor module consists of a catalytic combustion type sensor and a data acquisition and processing board, which can detect the concentrations of flammable gases such as CH4, C3H8, and H2 in the environment. The module takes the AIphasense Technology CH-A3 catalytic combustion sensor as the sensitive element and realizes the detection of gas concentration under the control of the sampling circuit. It has good stability and anti-toxicity. This module communicates with the receiving terminal in a digital manner and outputs the gas concentration signal through the UART bus, facilitating users to quickly form a system in a simple way in different scenarios. It is suitable for gas detection in the industrial field.