Fall 2024 Final Exam - Hydrogen Technologies - PDF

CHEG360: Introduction to hydrogen technologies and applications FALL 2024 - FINAL EXAM - 9th December 2024 Code of Honor: “I, _________________________, pledge to uphold academic integrity and honesty during this examination. I will not engage in any form of cheating, plagiarism, or academic miscon...

CHEG360: Introduction to hydrogen technologies and applications FALL 2024 - FINAL EXAM - 9th December 2024 Code of Honor: “I, _________________________, pledge to uphold academic integrity and honesty during this examination. I will not engage in any form of cheating, plagiarism, or academic misconduct. I will complete this examination to the best of my abilities, using only my own knowledge and resources. I will not provide or receive unauthorized assistance or use or have in my possession any unauthorized materials such as notes, textbooks, or electronic devices (MOBILE PHONES, SMARTWATCHES, HEADPHONES/EARBUDS, BLUETOOTH DEVICES, ETC). By signing this pledge, I affirm my commitment to ethical behavior and academic excellence.” Name___________________________ Signature_________________ ID ______________ Instructions: - There are a total of 38 questions, divided into MCQ, T/F, and short (essay) questions that require an explanation with your own words. Please, answer the MCQ and T/F here, and the short (essay) questions in the exam booklet. You will need to submit both. - Please, put your name, ID and signature in both of them. - Please, use pen (pencil is NOT allowed). Thanks, and good luck! Multiple Choice Questions [3 marks each] – CLEARLY MARK THE CORRECT ANSWER 1. To reach net zero emission by 2050, hydrogen is more critical to decarbonize: (a) Power production. (b) Hard-to-abate industries. (c) Physics. (d) Manufacturing processes. 2. What can hydrogen be used for? (a) To produce heat and power. (b) To produce synthetic fuels. (c) To store energy. (d) All of them. 3. Which of the following methods can be used to produce hydrogen from methane? (a) Pyrolysis. (b) Partial oxidation. (c) Steam reforming. (d) All the mentioned technologies. 4. Which molecules are used to produce hydrogen from electrolysis? 1  (a) H2O and CO2 (water and carbon dioxide). (b) CH4 (methane only). (c) H2O and H2S (water and hydrogen sulfide). (d) CH4 and O2 (methane and oxygen). 5. A solar fuel is a fuel (mainly hydrogen) produced from sunlight through different processes. From the following list, mark the ones that are used to produce solar fuels: (a) Photo-chemical. (b) Thermo-chemical. (c) Photo-Electro-chemical. (d) All of them. 6. Which type of reaction is typically involved in solar thermochemical fuel production? (a) Exothermic reactions. (b) Electrochemical reactions. (c) Endothermic reactions. (d) Photochemical reactions. 7. Hydrogen can be stored in cylinders/tanks by changing its physical state into compressed or liquid hydrogen, however, there are some issues associated to it. From the following list, please, highlight the one that it is NOT an issue for storing hydrogen in cylinders/tanks: (a) Low volumetric energy content. (b) Stringent operating conditions to change physical state of hydrogen. (c) High cost for storage cylinders. (d) Chemical stability of hydrogen. 8. Which one of the following processes can deliver high pure hydrogen (99.9%)? (a) Reaction of salt-like hydrides with water. (b) Reaction of methane with steam. (c) Mixing natural hydrocarbons of high molecular weight. (d) Electrolysis of water. 9. Choose from the list below the best approach to decarbonizing cement industry: (a) Finding clinker substitutes. (b) Developing new technologies. (c) Using low-carbon hydrogen. (d) Integrating CCUS technologies. (e) All of them. 10. Which of the following is not an advantage of using ammonia as a fuel? (a) Low NOx emissions. (b) Low flammability. (c) Low price as onboard fuel. (d) Low risk of explosion. 11. For which of the following processes is liquid biomass is not needed for producing hydrogen: (a) Biophotolysis. (b) Photo fermentation. (c) Dark fermentation. 2  (d) Microbial electrolysis cell. 12. What is the main reason for including the water-gas shift step in a steam methane reforming process? (a) To obtain more amount of hydrogen per mass of methane. (b) To increase the purity of the produced hydrogen. (c) To reduce the energy requirement of the process. (d) To reduce the CO2 emissions to the atmosphere. 13. It is expected that hydrogen will play a role in decarbonizing the hard-to-abate sectors. From the list given below, which one is not a hard-to-abate industrial sector? (a) Metallurgy. (b) Power production. (c) Heavy-duty transport. (d) Cement. True or False questions [1 mark each] – CLEARLY MARK THE CORRECT ANSWER 14. Hydrogen produced using wind power is the most promising clean technology in the UAE in the near-term. TRUE ___ / FALSE ___ According to the wind map, UAE does not have enough wind resources for bet in this direction. Solar power generation is an option, although the solar panels require high maintenance. 15. Blending is the injection of hydrogen into a natural gas stream using the existing infrastructure. Integrating blended hydrogen into natural gas transmission networks is feasible at levels of around 80%H2 with relatively minor upgrading. TRUE ___ / FALSE ___ 16. Production of green hydrogen from water splitting is the most environmentally friendly option, independently of the energy source used for the process. TRUE ___ / FALSE ___ Hydrogen is considered green only when the energy source of the process comes from renewable sources. 17. Water gas shift reaction is used in a second stage, to completely oxidize the unwanted fuel traces and obtain higher hydrogen purity. TRUE ___ / FALSE ___ 18. An autothermal reactor combines both steam reforming and pyrolysis reactions to enhance the hydrogen produced per mole of feedstock. TRUE ___ / FALSE ___ It combines steam reforming and partial oxidation. 19. The specific heat for liquid hydrogen at constant pressure is lower than water and much lower than that of oxygen. TRUE ___ / FALSE ___ The specific heat for liquid hydrogen at constant pressure is 9.688 kJ/(kg·K), which is twice higher than water (4.844 kJ/(kg·K) and five times higher than oxygen (1.938 kJ/(kg·K) (see lecture 4, slide 11). 3 20. Ammonia has a higher energy density than compressed and liquid hydrogen. TRUE ___ / FALSE ___ 21. Using CO2 as a cushion gas for underground hydrogen storage improves hydrogen trapping by filling smaller pores with brine and CO2, leaving larger pores for hydrogen. TRUE ___ / FALSE ___ 22. Photocatalysis is the action of light on biological systems that results in the dissociation of a substrate (usually water) into molecular hydrogen and oxygen. TRUE ___ / FALSE ___ This is the definition of Biophotolysis. 23. Hydrotreating processes are standard in refineries primarily to remove sulfur from refined petroleum fuels. This helps reduce sulfur dioxide emissions that are formed when the fuels are combusted. TRUE ___ / FALSE ___ 24. The cyanobacteria directly decompose water to bio-hydrogen and oxygen in the presence of light energy by photosynthesis. TRUE ___ / FALSE ___ 25. All hydrogen fuel cells need noble metals because of the low temperatures at which they operate. TRUE ___ / FALSE ___ Molten carbonate and solid oxide fuel cells do not need noble metals as they operate at very high temperatures (see slide 20 lecture 20 for a comparison of them). 26. Gasification of lignocellulosic biomass at the right conditions produces a syngas. TRUE ___ / FALSE ___ 27. CH4 addition is a promising technology to be used for avoiding the production of NOx during ammonia combustion. TRUE ___ / FALSE ___ It is not methane, but H2O2. Its addition can reduce the ignition delay, while slightly increasing the NO production. 28. A fuel cell is a device that uses electricity and water to produce hydrogen. TRUE ___ / FALSE ___ 29. Oxygen is needed to produce turquoise hydrogen from methane. TRUE ___ / FALSE ___ 30. The risk of a hydrogen explosion is lower than other common fuels because it tends to rise and disperse in the atmosphere. TRUE ___ / FALSE ___ 31. Global warming potential (GWP) is a number that expresses the potential trapping heat from the atmosphere of that gas compared to the same volume of CO2, being 1 the GWP of CO2. TRUE ___ / FALSE ___ 4 32. One of the main advantages of PEM Fuel Cells is that they operate at very high temperatures. TRUE ___ / FALSE ___ 33. Metal hydrides are used for physical hydrogen storage. TRUE ___ / FALSE ___ Questions: please, briefly address the following questions (answer in the exam booklet). Use your critical thinking for comparisons or discussions, when needed. 34. There is a growing interest in turquoise hydrogen. Please, answer the following questions: [10 marks] a) To which hydrogen are we referring with this color name and what are the final products? b) What are the main processes used to obtain it and the main operating factors affecting their performance? c) What are the benefits and d) limitations versus blue hydrogen (SMR process). List at least two advantages and two disadvantages. Answer: a) Turquoise hydrogen is the hydrogen produced from methane cracking (pyrolysis) producing hydrogen and solid carbon. 𝐶𝐻4 → 𝐶𝑠 (𝑠𝑜𝑙𝑖𝑑 𝑐𝑎𝑟𝑏𝑜𝑛) + 2𝐻2 b) The main processes to obtain it are thermal and catalytic processes; plasma can also be used. The main operating factors affecting their performance are temperature and the catalyst, depending on the process. The thermal (non-catalytic) process requires very high temperatures (above 1000°C) for high conversion rates, while the catalytic process requires efficient catalysts (usually Ni or Fe based catalysts). c) Benefits of this technology versus blue hydrogen (SRM+CCS): Solid carbon material is the only byproduct, with commercial applications. Lower energy requirements compared to SMR+CCS. Less complicated in terms of separation of byproducts compared to SMR or MPO (CO2 or CO), as the co-product is solid black carbon. No CO2 emissions vs low CO2 emissions. d) Limitations: Adsorption or membrane separation is required to separate unreacted methane from hydrogen and produce 99%vol. hydrogen. The formation of solid carbon can cause catalyst deactivation by encapsulating the catalyst, which needs air or steam to regenerate it. Very high temperatures are required for pyrolysis. Limited scalability (as of today). Rubric: 2.5 marks each part 35. We have learned in this course that one of the main applications of hydrogen would be to use it as a fuel. Now you are working as a junior engineer in ENOC, where they have built and operate a hydrogen distribution unit and operate some hydrogen trucks, and have some 5  employees under your responsibility. Explain here which are the safety considerations about hydrogen as compared to other fuels in terms of combustion, flammability and explosion that the need to consider. [9 marks] Answer: (see lecture 4) Combustion: - When hydrogen is used as a fuel, it produces heat and water. - As carbon is not generated and due to the presence of water vapor (which absorbs heat), a fire produced by hydrogen would have less power to disperse heat than a fire produced by a hydrocarbon. Flammability: - Very wide flammability range (4% - 74% concentration in air) and requires very little energy (0.02 mJ) to start combustion. - At concentrations < 10% flammability is similar to that of natural gas or gasoline. Explosion: - Much lower risk than other more common fuels since it becomes explosive in concentrations between 18.3% and 59%. - Hydrogen tends to rise and disperse in the atmosphere, other heavier gases tend to accumulate near the ground, increasing the risk of an explosion. Note: you do not need to provide the exact numbers, but the general concepts. Rubric: 3 marks each part, you still get the full mark if you mention the issues with flammability and explosion, and any other hint related to handling hydrogen safely. 36. Explain with your own words the basics of a hydrogen fuel cell, draw a schematic of it, and list, at least, two applications of them. [10 marks] Answer: A fuel cell is a device that produces electricity from the electrochemical oxidation of a fuel (hydrogen, hydrocarbons, etc.), in this case, hydrogen. Fuel cells are composed of an anode (negative side), cathode (positive side), and an electrolyte solution. Direct electricity is produced from the movement of electrons. Fuel cells have small voltages and are stacked or placed in series to increase the voltage. Electrochemical reactions occur at the electrodes with (1) Hydrogen is oxidized at the anode, while (2) oxygen is reduced at the cathode, with the electrodes formed from catalytic materials (typically Pt). The hydrogen fuel cells produce electricity and pure water. Applications: 1) transportation (heavy vehicles such as trucks, trains, etc.), 2) to produce power (either combined heat & power or for microgrids). See scheme below. 6 Rubric: 2.5 marks for mentioning that a fuel cell is a device that produces electricity and water (by using hydrogen in this case) 2.5 marks for mentioning the components: anode, cathode, electrolyte, and the presence of the catalysts (-0.5 mark if the catalyst is not mentioned) 2.5 marks for explaining how it works (the process and the schematic) 2.5 marks for mentioning the two large applications: transportation and power production. (-1.0 mark if one of the two applications is not mentioned). NOTE: unfortunately, some of you have mixed up the concepts of a fuel cell (to produce power and water from hydrogen and oxygen) with an electrolyzer (to produce hydrogen and oxygen from water by using power). This is a serious mistake. Still, you may have obtained some marks depending on your answers to some of the questions. 37. We had the privilege to have an expert on hydrogen and certifications in one of your classes. One of the outcomes of the lecture is that certifications of low-carbon hydrogen are needed to speed up the hydrogen economy. Can you briefly explain in one short sentence why? [4 marks] Answer: Certifications of low-carbon hydrogen ensure the hydrogen produced and traded globally meets specific environmental and sustainability standards, and can have a significant market impact. They promote transparency, incentivize clean production methods, and enable stakeholders to meet environmental and economic goals while combating climate change effectively. They also facilitate Facilitating Policy and Regulation Compliance. Rubric: the answers here have been very diverse, so we have tried to homogenize the marks by considering the key aspects to be mentioned. 4 marks (full mark) for mentioning most of the following: environmental, sustainability (or incentivizing clean production methods), standards across countries (and/or compliance with policies and regulations), benefits for the market. 3.0 if compliance with policies or standards required for specific geographic regions are missing. 7 38. The VP for Environment, Society and Governance (ESG) of EMSTEEL learned that we have been discussing the use of hydrogen to decarbonize the steel and iron sector in one lecture and in an expert panel discussion, and he is very much interested in knowing from you what the options are. Please, briefly summarize here what would you explain to him regarding the use of hydrogen to produce green steel. [8 marks] Answer: a) Green hydrogen can be used in the steel factories to produce heat and power, replacing fossil fuels. b) Hydrogen can be used as a reducing agent for the reduction of metallic ores to extract metals, such as iron (Fe), tungsten (W) and molybdenum (Mo). The by-product of this process is water. This new process (direct reduction) promises a significant reduction in CO2 emissions in steel making, with expected increase in hydrogen demand. See the scheme below. Rubric: 3 marks for mentioning that hydrogen can be used to produce heat and power in the factory, replacing fossil fuels. 3 marks for mentioning the use of hydrogen as a reducing agent for the reduction of metallic ore to extract metals 2 marks for any additional details on the process 8