12. Hydrogen from natural gas.docx

\- Steam Methane Reforming (SMR)\ - SMR with CCS\ - Autothermal Reforming (ATR)\ - Methane Pyrolysis and methods\ - Membrane reformer reactor (MRF) \ **Desulfurized Gas and Steam Introduction**: - The process begins with the introduction of desulfurized gas (typically...

\- Steam Methane Reforming (SMR)\ - SMR with CCS\ - Autothermal Reforming (ATR)\ - Methane Pyrolysis and methods\ - Membrane reformer reactor (MRF) \ **Desulfurized Gas and Steam Introduction**: - The process begins with the introduction of desulfurized gas (typically methane, CH₄) and steam. The desulfurization step is crucial because sulfur compounds can poison the catalysts used later in the process.  **Pre-reformer (a)**: - The mixture of steam and desulfurized gas enters the pre-reformer (labeled as \"a\" in the diagram), where initial reactions occur at approximately 500°C. Here, some of the heavier hydrocarbons in the gas are broken down into methane and hydrogen through partial reforming reactions. This step helps in stabilizing the gas composition before it enters the main reformer.  **Reformer Tube (b)**: - The gas then flows into the reformer tube (labeled as \"b\"), where it is exposed to a higher temperature, typically around 650°C. In this stage, steam reacts with methane in the presence of a nickel-based catalyst to produce hydrogen (H₂), carbon monoxide (CO), and a small amount of carbon dioxide (CO₂). The main reaction is: CH4+H2O→CO+3H2 - The reforming reactions are highly endothermic, meaning they require a continuous input of heat.  **Furnace (c)**: - The heat necessary for the reforming reaction is provided by the furnace (labeled as \"c\"), which burns fuel (a mixture of fuel and air). The temperature inside the furnace is around 850°C, which is essential to sustain the endothermic reforming reactions. The furnace is also responsible for heating the reformer tubes.  **Heat Recovery (d)**: - After the reforming process, the hot product gases, which primarily consist of hydrogen, carbon monoxide, and carbon dioxide, exit the reformer at high temperatures (around 850°C). These gases pass through a heat recovery system (labeled as \"d\"), where the residual heat is captured and used to preheat the incoming feed gases or to generate steam for other uses in the process, improving overall energy efficiency.  **Flue Gas**: - The flue gas, which is the exhaust from the furnace, is released after passing through the heat recovery system. This gas typically contains CO₂, water vapor, and some unburned hydrocarbons, which are then managed depending on environmental regulations.  **Final Product**: - The product gas, now rich in hydrogen, is sent to further processing units. This may include the Water-Gas Shift reaction to increase hydrogen yield and the separation of hydrogen from the gas mixture using pressure swing adsorption (PSA) or other purification methods.    Membrane reformer reactor (MRF) A Membrane Reformer Reactor (MRF) is an advanced hydrogen production system that integrates a hydrogen-selective membrane within a reforming reactor. This design allows for the simultaneous production and separation of hydrogen, leading to high-purity hydrogen output directly from the reactor. The membrane, typically made from palladium, selectively allows hydrogen to pass through, while other gases remain on the retentate side. MRFs offer increased efficiency, compact design, and potential for lower CO₂ emissions, though challenges include the high cost and durability of the membranes. separation frees the reactions from the limitation of chemical equilibrium\ The reaction temperature drops from conventional 700 -- 800°C to 500 -- 550°C\ Up to 90% CO2 concentration in the off‐gas enables capture of CO2 by direct liquefaction\ Fuel cell quality H2 is produced ≥ 99.99%