While production of electricity and hydrogen will continue to rely on the use of fossil fuels in the near future, there are novel alternative processes that allow this production to be carbon-neutral. We propose a new concept ? a hybrid pyrolysis / gasification reactor operating on natural gas (NG) or biogas. It allows power production with integrated CO2 capture or stand-alone hydrogen production combined with either carbon storage or carbon monoxide on-demand production in a highly efficient process. It combines catalytic thermal decomposition of NG with a high temperature solid oxide fuel cell (SOFC). By utilizing the excess heat of the SOFC as input to the pyrolysis reaction, a very high overall efficiency (>90%) is achieved. This innovation opens up for the new market in Norway and Europe: ?green? production of hydrogen fuel, electrical energy and either carbon monoxide or carbon black from NG with integrated carbon capture.
The primary objective of this Project is development of the hybrid reactor for pyrolysis and gasification of natural gas on a regenerating carbon catalyst. The work has focused on three main goals: taking the reactor design one step further to the larger pilot; collecting more data on the optimal process conditions and its robustness to input feed; and learning to operate without loss of conversion efficiency over time.
Activities and achievements in the Project:
? Design and building of the hybrid pyrolysis/gasification reactor and test setup:
o Extensive CFD simulations to dimension and verify the design elements
o Materials selection
o Manufacture of the reactor components in-house
o Building and automation of the test setup
o Pyrolysis reactor modelling to create a tool used in the future reactor designs
A tubular fixed-bed reactor of approx. 2 L total volume and length of 1600 mm modelling a single section of a larger pilot reactor was built and installed in a fully automated and remotely controlled test setup. Made of a heat- and carbon-corrosion resistant alloy, the reactor provided completely leak-tight operation at 10 bar pressure at the operating temperature of above 850 °C.
? Collecting the test data on the process conditions and robustness to input feed
o Assessing operating temperature in the range 800 ? 1000 °C
o Assessing the reaction kinetics by analysing gas composition along the length of the reactor
o Operating the reactor at up to 10 bar pressure in order to evaluate the reaction equilibrium and conversion efficiency change when coupled to a gas separation system
o Testing the reactor on three different compositions of the feed NG
While higher temperatures provide higher NG conversion, 850 °C was chosen as baseline, providing 56% conversion over 30 min pyrolysis cycle and making it more straightforward to thermally couple to a SOFC. Operating at 10 bar resulted in reduced gas conversion, so a trade-off would be needed when the reactor is integrated into an industrial process in the future. We have operated the reactor on three compositions of feed NG, two synthetic mixtures of C1-C5 hydrocarbons and a real NG from one of the Norwegian fields. The testing was successful, demonstrating the robustness of the process to the variations of feed gas composition. C4-C5 hydrocarbons in the NG seem to promote the decomposition, the mixture containing most of them showing highest conversion. If the NG contains CO2, its pyrolysis in this reactor will also produce CO gas simultaneously, so prior removal of CO2 might be considered depending on the process scheme.
? Learning to run the reactor without loss of conversion efficiency over long time
Various forms of carbon have been shown to catalyse the pyrolysis of methane and natural gas. Active carbons (ACs) promote decomposition of NG into H2 and C inside the micropores, and so catalytic activity of all ACs rapidly decreases over time when the micropores are filled up. Pre-filling the reactor with AC allows starting the pyrolysis with high conversion and minimal by-products formation, while repeating partial gasification of the carbon allows keeping it active over time.
? We have shown over 150 pyrolysis-gasification cycles performed on the same initial load of AC catalyst.
Each pyrolysis cycle lasted 30 min, and gasification time was adjusted to balance the production and consumption of solid carbon inside the reactor. When performed at the same operating conditions, the repeated partial gasification of the carbon ensured constant conversion efficiency over the whole test duration.
Summary: Prototech has achieved the goals of the Project, collecting important process data and demonstrating the long-term operation of the alternating pyrolysis-gasification reactor without loss of conversion efficiency. We are now planning to take the development further to a pilot scale in collaboration with an industrial partner.
Business outcome: the data and experience obtained in this project, together with earlier results by Prototech, is a sufficient basis for up-scaling the process developed here. This work would be done in close collaboration with an industry partner. If a business case is established at the start of the pilot activity, patents would be filed, and a commercial activity/company would emerge.
Other impacts: scientifically, the results are of high interest too. To our knowledge, no one has previously reported a successful long-term operation of such a reactor, and the concept of combining thermal decomposition of natural gas with a solid oxide fuel cell has not been reported, either. An article in peer-reviewed journal is in work. At the level of society, the industrial implementation of thermal decomposition of natural gas may be an important step in the global transition to hydrogen economy, before large scale hydrogen production from renewables is established.
The main purpose of the proposed innovation is to utilize natural gas (NG) or biogas for power production and co-production of hydrogen in a highly efficient process while capturing the NG carbon content.
To achieve this, two technologies are tightly integrated. The first is the use of catalytic pyrolysis (thermal decomposition) of NG, covered by a European patent: EP 1140695B1 held by Prototech. The second is the use of a high temperature solid oxide fuel cell (SOFC). By utilizing the excess heat of the SOFC as input to the pyrolysis reaction and alternating between carbon production by pyrolysis and carbon gasification, a very high overall efficiency (up to 90%) is achieved. The carbon contained in the NG takes the form of a pure stream of CO2 or easy to handle solid carbon, depending on operating mode.
The proposed innovative reactor, when combined with a SOFC, has a large degree of flexibility. The formed carbon can undergo gasification to produce carbon monoxide, which may be used directly as a fuel in the SOFC. When combining pyrolysis and alternating gasification of the carbon with a SOFC, a range of operating modes exists: a) Co-production of hydrogen and electricity with CO2 capture; b) Electricity production where H2 is used as fuel in the SOFC; c) Electricity + CO2 (pure stream ready for storage); d) Electricity + H2 + CO2 (pure stream ready for storage) e) Electricity + syngas and other.
Building up on three previous RCN projects carried out on this topic, the main objective of this Proposal is to resolve the remaining issues, collect and evaluate a large set of test data, build a new hybrid pyrolysis gasification reactor with regenerating carbon catalyst and demonstrate 100 regeneration cycles without efficiency loss. This is the final step towards building a pilot plant of a commercial scale.
CLIMIT-Forskning, utvikling og demo av CO2-håndtering