Award-winning technology of the utilization of ventilation air methane

The technology for the utilization of methane from the ventilation air of hard coal mines in the Thermal Reversing Reactor (TFRR), developed at the Institute of Chemical Engineering of the Polish Academy of Sciences in Gliwice, was awarded a gold medal at the 13th International Invention and Innovation Show INTARG®2020 Online, as well as a gold medal and a special award at the International Invention and Trade Expo 2020 Online in London.

The present invention refers to the method for utilization of low-concentration gas mixture of combustible gas and air with stable consumption of heat energy and a flow reversal for embodiment of the method. The invention refers specifically to the combustion of methane-air mixtures, with methane concentrations that can be found in the ventilation air of hard coal mines (the so called VAM - Ventilation Air Methane) in a thermal flow reversal device with heat recovery. The method and device according to the invention ensure the utilization of combustion heat in a heat recovery apparatus in the device’s operating conditions providing for high combustion efficiency (conversion) and sufficiently symmetric temperature profiles over device packing, as well as stability of energy consumption wherein energy stream delivered to consumers is approximately constant over the period of device’s operation. The patents obtained, depending on the national version, contain 15 to 20 claims, which protect the original elements of the method and device, giving advantages over similar devices of the competition.

The idea of use VAMOXID is to decrease methane emission to the atmosphere from ventilation shafts of coal mines. The VAM emission by coal mine industry is a serious problem from the environmental protection point of view. Methane as a greenhouse gas has a negative influence on the environment. Its global warming potential (GWP) is at least 21 times higher than GWP for CO2. It means that if only a part of this methane was burned to CO2, the equivalent effect of this emission on the greenhouse effect would decrease. Main problem with VAM abatement consists in low methane concentrations in the mixtures. VAM consists of 0.1–1.0 vol.%. of the combustible component and the amount varies from one coal mine to another. Despite of this VAM can be also a valuable energy carrier. Such a lean mixture can be considered as an alternative fuel for the energy production by applying modern combustion technologies such as VAMOXID.

The main unit of VAMOXID is a thermal flow reversal reactor (TFRR), which consists of two parts – Section I and Section II, connected by a duct at the top. Part of the hot gas can be withdrawn from this duct to the heat recovery exchanger. Both sections are packed with ceramic monolith blocks with a large number of straight and parallel channels, which results in a low pressure drop. The valves responsible for the gas flow reversal are located close to the bottom part of the reactor. An experimental condition were close to the real environment. In the experiments the concentration of methane was varied from 0.1 to 1 vol. % by mixing natural gas with air. Feed gas flow rate was varied from 200 to 580 m3/h. Electric heaters mounted at the top of TFRR were used only for preheating the monoliths to enable launching of TFRR before normal operation. Technology readiness levels (TRL) for VAMOXID is VI.

The VAMOXID can be used in methane coal mines where ventilation air methane contain enough amount of methane. The experiments showed that the device works autothermally from methane concentrations equal to or higher than 0.2 vol.%. Moreover, a reasonable heat recovery is already possible for methane concentration of 0.4 vol.% or higher, which bodes well for the future industrial installation. The expected heat recovery for an average ventilation shaft can achieved 4.3 MWt for 0.43 vol.% of methane and even 20.2 MWt for 0.77 vol.% of methane concentration. The recovered heat can be successfully applied for further use as a cold generation or an electricity production.

VAMOXID have significant advantages over competing solutions, such as:

  • absence of a catalyst, which significantly lowers the investment cost and extends the life of the device,
  • high combustion temperature, which allows for the production of high-parameter energy carriers and increases the efficiency of electricity production,
  • autothermal work of VAMOXID, without any additional fuel for methane concentrations from 0.2 vol.%. For higher concentration above 0.4 vol.% the heat can be successfully recovered for further uses,
  • developed algorithms for controlling the switching time and other parameters, which ensures a thermal symmetry of reactor and protection against emergency,
  • utilization of the heat generated in the methane combustion process in the heat exchanger located outside the reactor, which leads to a higher stability of combustion, reduces cyclical fluctuations in the generated heat and does not disturb the symmetrical operation of both sections of the reactor,
  • better stability of the reactor work at low concentrations, when the removal of heat becomes unprofitable; the possibility of a complete shutting off the hot gas withdrawal to the external heat exchanger, which keeps all the heat generated in the reactor and protects against loss of autothermicity,
  • inert packing with a low gas adsorption capacity used in the reactor, which minimizes unburned gas blow-outs during gas flow reversal from cool zones of the reactor,
  • geometrical and material parameters of ceramic monolithic blocks which matches the operating conditions in TFRR,
  • dynamic and quasi-static mathematical models of the process for the optimization of design and operating parameters.

It is worth to mention that KATALIZATOR Sp. z o.o. from Krakow, co-creator of the patents, has extensive experience in the field of purifying industrial waste gases and process gases from organic pollutants, is prepared to build a VAMOXID installation with a capacity of several tens of thousands of m3/h.

Ecological and environmental effect:

- utilization of methane by VAMOXID would decrease the negative impact of VAM emission on the environment.

Economic effect:

- for methane concentration of 0.4 vol.% or higher it is possible to recovered reasonable amount of heat which can be successfully applied for further use, as a cold generation or an electricity production.

Society effect:

- heat recovered from VAMOXID can be used to produce cold, thereby reducing the demand for electricity for air-conditioning mining excavations.

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