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Methanation is the conversion of carbon monoxide and carbon dioxide (CO x) to methane (CH 4) through hydrogenation. The methanation reactions of CO x were first discovered by Sabatier and Senderens in 1902. [1] CO x methanation has many practical applications.
CH 4 + H 2 O → CO + 3 H 2 Δ r H = +206 kJ mol −1 Water shift reaction CO + H 2 O → CO 2 + H 2 Δ r H = -41 kJ mol −1 Synthesis 2 H 2 + CO → CH 3 OH Δ r H = -92 kJ mol −1. The methanol thus formed may be converted to gasoline by the Mobil process and methanol-to-olefins.
The energy factor metric only applies to residential water heaters, which are currently defined by fuel, type, and input capacity. [5] Generally, the EF number represents the thermal efficiency of the water heater as a percentage, since it is an average of the ratio of the theoretical heat required to raise the temperature of water drawn to the amount of energy actually consumed by the water ...
The heating value (or energy value or calorific value) of a substance, usually a fuel or food (see food energy), is the amount of heat released during the combustion of a specified amount of it. The calorific value is the total energy released as heat when a substance undergoes complete combustion with oxygen under standard conditions .
The reaction takes place in a single chamber where the methane is partially oxidized. The reaction is exothermic due to the oxidation. When the ATR uses carbon dioxide the H 2:CO ratio produced is 1:1; when the ATR uses steam the H 2:CO ratio produced is 2.5:1 The reactions can be described in the following equations, using CO 2:
O 2 + C → CO 2 (ΔH = -393 kJ/mol) Theoretically, to make 6 L of water gas, 5 L of air is required. Alternatively, to prevent contamination with nitrogen, energy can be provided by using pure oxygen to burn carbon into carbon monoxide. O 2 + 2 C → 2 CO (ΔH = -221 kJ/mol) In this case, 1 L of oxygen will create 5.3 L of pure water gas.
Steam reforming or steam methane reforming (SMR) is a method for producing syngas (hydrogen and carbon monoxide) by reaction of hydrocarbons with water. Commonly natural gas is the feedstock. The main purpose of this technology is often hydrogen production , although syngas has multiple other uses such as production of ammonia or methanol .
Direct electric resistance tank water heaters are not included in the Energy Star program; however, the Energy Star program does include electric heat pump units with energy factors of 200% or higher. Tankless gas water heaters (as of 2015) must have an energy factor of 90% or higher for Energy Star qualification.