Ventilation Air Methane – Converting a Greenhouse Gas into Energy Prof. Krzysztof Warmuzinski Dr hab. Krzysztof Gosiewski, Dr Marek Tanczyk Dr Manfred Jaschik, Aleksandra Janusz-Cygan Polish Academy of Sciences, Institute of Chemical Engineering Gliwice, Poland 5th ISCECC, 11-12 October 2012, Athens, Greece

Methane Increase in concentration (250 years): CO2 – 37%, CH4 – 149% GWP (100 years) – 21 5 Gt of CH4 in the atmosphere (105 Gt CO2 eq.) Annual emissions: 24 Gt of CO2, 0.45 Gt of CH4 = 9.45 Gt/y of CO2 (= 40% CO2 emissions)

Methane sources Livestock, rice growing landfill and sewage Fossil fuel production (gas, oil, coal) Leakage from the gas distribution systems (~100 Mt/y; 1/3 in Russia) Thermokarst Yedoma Methane clathrates 100 Mt CH4 = 2.1 Gt CO2 eq. (EU produces around 2 Gt/y of CO2)

ANTHROPOGENIC SOURCES OF METHANE EMISSIONS

SOURCES OF COAL–RELATED METHANE EMISSIONS

VENTILATION AIR METHANE

membrane separation PSA TSA 60 000 m3N/h 40 000 m3N/h 1 764 m3N/h

CFRR So far, most of the studies have focused on catalytic combustion in CFRRs (catalytic flow-reversal reactors) Advantages Relatively low operating temperatures (below 800 oC ) Safety margin measured by the distance from the temperature of NOx formation is also wider than for TFRR Cheaper materials of construction

CFRR Drawbacks Operating temperature (up to 800 oC) is, however, too high for less expensive catalysts Cost of the expensive catalyst can make the total cost of the plant very high Catalyst will operate with wet and dusty gas, and thus its lifetime will probably be very short Lower temperatures at the inlet to heat recovery units make the recovery less efficient Despite abundant literature and studies, the CFRR has so far been realized only on a small scale

TFRR Advantages TFRRs are widely used in industry for VOCs combustion Non-catalytic oxidation in TFRRs (thermal flow-reversal reactors) is often frequently regarded as an attractive alternative Advantages No investment and operating costs associated with a catalyst TFRRs are widely used in industry for VOCs combustion The concept has already been proven in ventilation air installations (processing up to 136 000 m3(STP)/h) Expected better behaviour with wet and dusty gas Higher temperatures at the inlet to heat recovery units make the recovery more efficient

TFRR Drawbacks High operating temperatures (up to about 1 200oC) More expensive materials of construction Safety margin for the temperature of NOx formation is smaller than for CFRR. Thus, the outlet concentrations of NOx can be higher than those for catalytic reactors

System of central cooling System with hot gas withdrawal CFRR Principal heat recovery schemes INERT CATALYST HEAT EXCHANGER System of central cooling INERT CATALYST Hot gas withdrawal to heat exchanger System with hot gas withdrawal

System of central cooling System with hot gas withdrawal TFRR Principal heat recovery schemes INERT HEAT EXCHANGER System of central cooling System with hot gas withdrawal Hot gas withdrawal to heat exchanger

ESTIMATION OF KINETIC PARAMETERS LABORATORY EXPERIMENTS IN TUBULAR REACTORS (FREE-SPACE COMBUSTION, MONOLITH A, MONOLITH B) TENTATIVE SELECTION OF REACTION SCHEMES (SINGLE STAGE, CONSECUTIVE, PARALLEL, CONSECUTIVE-PARALLEL) ESTIMATION OF KINETIC PARAMETERS FINAL SELECTION OF A REACTION SCHEME AND KINETIC EQUATION BASED ON FORMATION OF CO MAGNITUDE OF THE KINETIC PARAMETERS VALIDATION OF THE MODEL IN A PILOT TFRR (FEED FLOWRATE UP TO 1,000 m3/h)

KINETIC EXPERIMENTS (free space) Conditions of the process Constant gas flowrate of 0.12 m3/h Temperatures from 500°C to 890°C Initial methane concentrations: 0.5 to 1.4 vol.% Quantities measured Temperature in the cell Concentrations: CH4 (inlet, outlet) CO (outlet) CO2 (outlet) Gas flowrate

KINETIC EXPERIMENTS (Monolith A) Conditions of the process Constant gas flowrate of 0.5 m3/h Temperatures from 470°C to 660°C Initial methane concentrations: 0.2 to 1.7 vol.% Quantities measured Temperature along the monolith Concentrations: CH4 (inlet, outlet) CO (outlet) Gas flowrate

KINETIC EXPERIMENTS (Monolith B) Conditions of the process Constant gas flowrate of 0.8 m3/h Temperatures from 660°C to 820°C Initial methane concentrations: 0.38 to 1.2 vol.% Quantities measured Temperature along the monolith Concentrations: CH4 (inlet, outlet) CO (outlet) CO2 (outlet) Gas flowrate

PRELIMINARY RESULTS FOR THE PILOT TFRR AT CYCLIC STEADY STATE Feed flow rate Half-cycle time Methane concentration Conversion Proportion of gas withdrawn m3/h s Inlet, vol. % Outlet, vol.% % 412 240 1.03 0.04 96.1 17.1 398 180 0.77 0.03 9.8 400 90 0.53 0.02 96.2 3.6 402 50 0.43 90.7 2.3 435 60 0.31 93.5 20 0.35 0.05 85.7 406 0.22 86.4

EXPERIMENTAL AND PREDICTED TEMPERATURE PROFILES IN THE PILOT TFRR Experiment vs. model (consecutive scheme)

CONCLUSIONS Ventilation-air methane can be efficiently oxidized in a non-catalytic reverse-flow reactor A portion of the heat generated in the reactor can be extracted without affecting the sustained cyclic operation The consecutive reaction scheme, with the kinetic parameters estimated based on laboratory experiments, can be used to simulate the behaviour of the pilot reactor (both qualitatively and quantitatively) 23

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