Hydrogen economy is capitalizing the decarbonization of transport and industrial sectors. Ammonia is an attractive intermediate to store and transport hydrogen, due to its low production cost, well developed storage and transportation infrastruc- ture, high hydrogen density in its liquified form (for transportation) and the potential production from renewable energy sources. Although there have been significant ad- vancements in catalyst development for ammonia decomposition, the potential of this technology cannot be fully exploited until significant process development is made. In this sense, catalytic membrane reactors show promising features and performances. In this work, ammonia decomposition has been studied using the following ap- proach: (1) Catalytic Packed Bed Reactor (CPBR) and kinetic modeling, (2) Cat- alytic Packed Bed Membrane Reactor (CPBMR) modeling and (3) CPBMR scale-up. Stage (1) was performed using Ru-K/CaO and Co-Ce catalysts over a wide range of experimental conditions (including pressures up to 16 bar). Stage (2) includes 1-D and 2-D models that were further validated experimentally, also using different software to tackle the stage (3), which aims to give the optimized geometry and properties of a CPBMR for a production of 5 N m3 h−1 of high purity H2 . The results presented in this Thesis enabled to: (1) obtain a reliable kinetic model capable of describing the ammonia decomposition under a wide range of operating conditions, using Ru-K/CaO and Co-Ce catalysts. (2) identify a range of operat- ing conditions where the CPBMR performs better than the CPBR in terms of NH3 conversion, H2 recovery and H2 purity. This range includes: reaction temperature between 250◦C and 500◦C; reaction pressures between 1 and 16 bar; space times be- tween 1 and 15 gcat h mol−1 and H2 permeate pressure higher than the atmospheric pressure (up to 5 bar). (3) scale-up the CPBMR for ammonia decomposition at a pilot scale, encountering that a pilot plant for a production of 5 N m3 h−1 of pure H2 ( >99.99%) could be obtained with a relatively small multitubular arraignment, that might be even smaller than the needed for the same product using other technology.

Many of the current methods of assessing anaerobic biodegradability of solid samples require sample modification prior to testing. Steps like sample drying, grinding, re-drying and re-grinding to 2mm or less make the test results difficult to apply to field conditions and could lead to oxygen exposure, possibly distorting the results. Finally, because of a small sample size of about 10-50g w/w, the test result may not be representative of the bulk material. A new tool dubbed ‘tube’ has been developed, made of 10 cm diameter PVC pipe measuring 43.5 cm long with 3600 ml capacity with caps at both ends. For easy sample introduction, one endcap is fixed while the other is screw capped. A distinctive feature is the wide neck opening of about 10 cm where solid samples can be introduced as is, without further sample modification. Research has proven the tube applicable across various types of solid organic waste and conditions provided that a suitable organic loading rate is determined. The tube is best operated using 5-7 days pre-digested digested sewage sludge as seed, with minimal mixing and without the addition of nutrients or alkali solution. The test result can be obtained within 4-6 days to 20 days, signifying a 50-75% and 95% substrate degradation, respectively. Irreproducibility seen in some experiments may not only be a function of the seed and the substrate. The organic loading rate (OLR) at which the test is conducted is also influential especially if test is conducted closer to its maximum OLR tolerance where anaerobic process is more erratic. The performance of a continuous reactor digesting on a similar substrate can be estimated using this new tool. Food waste is established by the tubes to have an ultimate methane potential (B0) of 0.45L CH4/g VS. The same substrate when digested in a continuous reactor will produce about (B) 0.32 L CH4/g VS. The first order rate constant for both systems; batch and continuous are identical at 0.12 to 0.28 d-1. First order kinetics is efficient at modelling the anaerobic degradation when the process is healthy but may be less reliable under an unstable process. This research recommends the use of kinetics in combination with the experimental data (e.g. HRT, OLR, yield) when planning and designing an industrial plant to avoid overdesign and unnecessary building, maintenance and operating costs.