Ventilation Air Methane (VAM) refers to the ventilating exhaust from coal mines with methane concentrations between 0.1 and 1.9%. Although the concentration is extremely low, the volume of VAM flow is extremely large. Experts predict that more than 50% of all VAM is exhausted from mine ventilation systems directly to atmosphere and remains underutilized; thus the total quantity of methane released is significant. This will damage the ozone (O3) layer in the atmosphere and as a result, contribute to climate change.
The Chinese government is giving an incredible amount of attention to environmental protection and making the corresponding regulations increasingly restrictive. This has hit the coal industry hard. Almost every coal mining enterprise in China must quickly determine how to meet the regulatory standards and at the same time, efficiently utilize the huge amount of VAM.
A large coal mining company in Shanxi Province, China, decided to adopt a new technology to capture the VAM and convert it into usable energy. After careful evaluation of the suppliers, Anguil’s team in Shanghai was selected to provide the VAM air pollution control system. Anguil Environmental is headquartered in the United States with more than 1,900 pollution abatement installations around the world. Having a presence in Asia for over two decades, the company has successfully installed hundreds of their pollution abatement systems in China.
After a comprehensive design review, Anguil recommended the Regenerative Thermal Oxidizer (RTO) technology equipped with hot gas bypass to destroy the VAM emissions and some low concentration Coal Bed Methane (CMM) from the drainage pipes. With Anguil’s RTO design, no auxiliary energy is required for combustion so long as adequate incoming methane concentrations are maintained, typically above 0.35%.
Any excess heat produced during the oxidation process is routed from a hot gas bypass dampers to a boiler system to generate enough steam, which is led to the steam turbine for electricity generation. Different from traditional methods of power generation by burning the coal or gas, using the excess heat from the RTO does not result in the presence of nitrogen oxide (NOX) and can keep the hot air stream at a very stable temperature, which is very important for the following power generation. There is enough steam to also provide building heat during the winter and cooled shaft air during the summer.
This way, the RTO system is not a just destruction technology; the emissions are converted from a greenhouse gas to a revenue generating initiative for the coal mining enterprise as they are able to sell the electricity.
This VAM abatement project consists of six RTOs that process a total exhaust volume of 540,000 Nm3/hr (336,448 SCFM) with an average methane concentration of 1.2%. Once at full capacity, the system will generate electric power with an installed capacity of 15 megawatts which will be returned to the national power grid. Independent reports show that the methane destruction efficiency is above 99.5% and the system is capable of destroying 51 million cubic feet of methane annually.
Under the close cooperation between the different departments and the full support from Anguil headquarters in the United States, the RTOs were installed on time and within budget. The mining customer recognized Anguil with a Best Engineering Organization Unit Award.
As a new method to utilize a very low concentration of VAM in high efficiency, this project has received extensive attention locally. As reported by several local news outlets, the initiative has been listed as a Methane Zero Net Emission Demonstration Project by China National Development and Reform Commission.
Since the success of this installation, Anguil has received several more orders from other mining companies looking to utilize VAM and reduce their environmental impact. Anguil’s VAM system proves that mining operations can profit by incorporating a properly designed oxidation technology for air purification and combine it with some sort of heat recovery system for steam, heat or electricity production.