Steam Reforming and the Production of Hydrogen Gas Essay

Steam Reforming and the Production of Hydrogen Gas - Essay Example About 50% of the global production of Hydrogen is produced by this process(www.getenergysmart.org/Files). eg. activated carbon filters, pressurisation and depending on the reformer design, either pre heated and mixed with processed steam or directly injected with the water into the reformer without the need for an external heat exchanger. The water is normally demineralised using appropriate water conditioning systems. Two options are available for reforming one option is high pressure reforming at a working pressure upto 16 bar. The other option is to use low pressures (1.5 bar) with increased conversion ratios (www.global-hydrogn-beus-platform.com). 2.2 Steam Methane Reforming: The process involves the use of high temperature steam (700C) which is reacted with natural gas( primarily methane) to produce Hydrogen. Methane reacts with steam under 3- 25 bar pressure in the presence of a catalyst to produce Hydrogen, Carbon Monoxide and a relatively small amount of Carbon Dioxide. This process is endothermic and hence heat must be supplied to the process to proceed. (www1.eere.energy.gov) The methane steam reforming reaction is endothermic. Hence this reaction requires a high process temperature to proceed. As the number of moles also changes for the reaction, the reaction is facilitated by as low a pressure as possible to maximise the Methane conversion rate. Another way to shift the equilibrium to the right side is to increase the ratio of steam to methane. Overall, the conversion rate of methane is a function of pressure, temperature and steam/ Methane ratio. The reformer reactor consists of catalyst filled tubes surrounded by a fire box that provides the heat for the reaction as shown in the process flow diagram ( Fig.3) Water Gas shift Reaction: CO + H2O CO2 + H2 (H = - 41.2kJ/mol) (2) The water gas shift reaction is exothermic and needs as low a temperature as possible to proceed. Based on Le Chatelier's principle, the WGS reaction rate: (1) Increases with increase in steam fraction in the inlet gas (2) Decreases with increase in Hydrogen in the inlet gas (3) Decreases with increase in temperature The reactor temperature influences the flame temperature of the reactants. Hence at higher temperature more Methane is converted and less Hydrogen. The presence of a catalyst such as Nickel helps in the formation of Hydrogen rich reformate. The heat required for the first reaction is obtained by the combustion of fuel gas and/ or purge tail gas from the PSA system. Following the reforming step, the synthesis gas is fed into the CO conversion reactor to produce additional Hydrogen. This process occurs in two stages consisting of a High Temperature Shift ( HTS ) reactor at 350C and a Low Temperature Shift ( LTS ) at 190 to 210C.High temperature shift catalysts have an Iron Oxide-Chromium Oxide basis while LTS catalysts consist of Copper Oxide. 3.0 Gas Purification: Hydrogen purification by means of pressure swing adsorption (PSA). The PSA units reach hydrogen

Urban futures (tutorial short answers) Essay Example | Topics and Well Written Essays - 500 words

Urban futures (tutorial short answers) - Essay Example All such functions are important and take place side by side simultaneously in the same public space in a fine balance. According to Edensor (2011), public space is considered important due to the provision of social centers and necessary activities that occur in such space. A lot of joyful human activities are found in public space, and also offer more room and opportunities for people (Edensor, 2011). Lubin (2012) asserts that public space is formed through opening government buildings and property to the public such as public gardens and public libraries. The reformation and contestation of the public space is something of a hallmark for critical theory regarding geography, cultural studies, philosophy, visual art, urban design, and social studies. Public space has for sometime been miscomprehended to mean places like gathering halls which is technically the essence of the broader social space concept (Lubin, 2012). Edensor (2011) says that through the spatial organization and landscape of public space, the social construction of the public space is viewed to be ruled privately through the explicit and implicit expectations and rules of the public space that are enforced. According to the articles, everyone has a right to use and/ or access public space, in contrary to private space that has particular restrictions. There has been however some presence of academic interest in th e formation and management of public space in the cities. According to Lubin (2012), management measures have been taken to control usage of the public space. The benches have been designed to restrict people from resting and sleeping on them. In some situations, police forces are involved in restraining those who misuse the public space. This is a similar practice in most cities in taking care of the public space (Lubin, 2012). Both Edensor (2011) and Lubin (2012) say that the functions of public space is contested and reformed through the privately owned