Flow Measurement Application in Coalbed Methane Ground Extraction

A leading company in Shanxi specializes in coalbed methane ground development, coal mine gas management, and coalfield geological exploration. To eliminate gas hazard risks at the source, the company collaborated with a large provincial coal enterprise to implement the "Province-wide Gas Extraction Full Coverage Project". It established coalbed methane ground extraction bases in four major coal mining areas, reducing coal seam gas content and mine pressure through scaled extraction to ensure safe production. The project, lasting three years (April 2019 - March 2022), deployed a total of 842 high-reliability gas flow instruments, forming an industry benchmark solution.

Project Challenges

Coalbed methane (mainly composed of methane) ground extraction faces complex working conditions:

1. Complex medium: The gas contains dust and has high humidity (RH > 90%), which can easily cause instrument wear and blockage.

2. Pressure fluctuation: The extraction pipeline pressure ranges from 0.2 to 6.3 MPa, requiring wide-range adaptability.

3. Safety risks: The explosive limit of methane (5%-15% VOL) demands an instrument explosion-proof rating of Ex d IIC T4.

4. Real-time data: Dynamic monitoring of extraction efficiency and gas concentration is required to support mine safety early warning.

Solutions and Product Configuration

Our company customized a combination solution of gas turbine flow meters and vortex precession flow meters, covering the full pipeline range from DN50 to DN200 with a pressure tolerance of 1.6-6.3 MPa, to achieve precise control throughout the extraction, measurement, and transportation process:

1. Gas Turbine Flow Meters (STG Series)

• Technical Advantages:

• Titanium alloy bearings + tungsten carbide shaft core, resistant to dust wear (particle size ≤50μm).

• Turndown ratio of 30:1, accuracy ±1.0% (certified by ISO 9951), pressure tolerance up to 6.3 MPa.

• Explosion-proof design (Ex d IIC T4), compliant with GB 3836.1-2010 standards.

• Application Scenarios:

• Deployed in high-pressure main pipelines (＞2.5 MPa) to measure the total volume of methane extraction in real-time.

• Built-in temperature/pressure sensors automatically calculate the standard flow rate (Nm³/h), with an error of less than ±1.5%.

2. Vortex Precession Flow Meters (SSV Series)

• Technical Advantages:

• No mechanical rotating parts, maintenance-free design, suitable for gas-liquid mixed media.

• Built-in flow field straightener, resistant to flow distribution interference (only 3D straight pipe section required upstream).

• Wide turndown ratio of 15:1, low pressure loss (＜0.02 MPa), accuracy ±1.5%.

• Application Scenarios:

• Used in low-pressure branch lines (0.2-1.6 MPa) and inlet of gas collection stations to monitor single-well extraction efficiency.

• Data is uploaded to the SCADA system via Modbus RTU, linked with extraction pump frequency conversion speed regulation.

Implementation Results

• Safety Improvement: Gas extraction rate increased to 85%, and coal mine gas outburst accidents decreased by 90%.

• Energy Efficiency Optimization: The precision of turbine flow meters improved methane recovery and utilization rate to 78%, reducing over 500,000 tons of CO₂ equivalent emissions annually.

• Maintenance Cost Reduction: The maintenance-free design of vortex precession flow meters reduced annual maintenance costs by 40%.

• Data Value: Data from 842 instruments integrated into the intelligent extraction platform, achieving three-dimensional visualization of extraction efficiency, concentration, and pressure.