Substitute natural gas
Synthetic natural gas or substitute natural gas (SNG ) ( Colloquially also synthetic natural gas ) is a substitute for natural gas, which is based on coal, especially brown coal, or biomass (bio -SNG or biomethane) produced via synthesis gas. In order to replace natural gas, SNG has this in its composition and properties as possible to those.
History
Process for the production of SNG from coal in 1902 were developed and brought to maturity industry during the oil crisis in the 1970s. This effort came from the fear that achievable sources of natural gas might not be sufficient for long-term supply of industrial nations. Natural gas made at that date the majority of the supply of raw materials for energy production and should be replaced by low available carbon. 1984 launched a first plant with a daily production of 3.9 million m3 SNG in North Dakota ( Great Plains Synfuels Plant) production based on lignite. In this plant is currently produced in 14 parallel carburetors SNG with a thermal output of 150 MW each and methanized. The total production is about 15 TWh / a Other plants have not been built because of the high Investititionskosten and new finds of natural gas sources.
In particular, in recent years there has been increasing for the use of biogas for the production of biomass- based substitute for natural gas, which is referred to as bio -SNG, biogas or biomethane. Predominantly located in the development and testing of the production of bio-SNG from wood gasification.
Technology
Synthetic Natural Gas on the basis of lignite is produced by a coal gasification and on the basis of biomass on biomass gasification to synthesis gas. In both cases, the resulting synthesis gas is supplied after the cleaning of particles, and proportions of carbon dioxide and chlorine compounds sulfur subsequent methanation. This is done exothermic and takes place at temperatures of 300 to 450 ° C and a pressure of between one and five bar held in the presence of a suitable catalyst. The following reactions take place:
The ratio between hydrogen and carbon monoxide can already vary significantly upon entry into the Methanisierungsphase, increasing the risk of carbon formation is via the Boudouard reaction, which can be countered by increased water vapor contents. The resulting gas mixture contains up to 50 % carbon dioxide and must be further processed for use as SNG by separation of hydrogen and carbon dioxide.
Use
While synthetic natural gas is produced on the basis of lignite in the U.S. for a long time and fed into the natural gas network, this is in Bio-SNG is currently not the case. Here there are only demonstration plants as bsp. in Güssing, where the resulting synthesis gas is, however, supplied primarily of direct thermal use.
Recycled SNG must, as obtained from biogas Biomethane the natural gas largely correspond to be used as a substitute can (see # biomethane use). The produced in North Dakota SNG has the following composition: 96.3 % methane, 0.02 % carbon, 1.38% hydrogen, 1.1% nitrogen, and argon, and 1.2% carbon dioxide.
Storage of wind and solar energy in the natural gas grid
In 2010, the Fraunhofer Institute for Wind Energy and Energy System Technology (IWES ) published the idea to store irregularly occurring wind and solar energy in the natural gas grid with the help of SNG. For this purpose, hydrogen is produced by electrolysis, which " is converted in conjunction with CO2 ( eg from electricity generation using fossil fuels or from the processing of biogas ) in a methanation for SNG and stored in the natural gas grid. " Then
Colloquially obtained in this way gas is referred to as " wind gas " or " solar gas ".
The storage capacity of natural gas storage in German gas grid accounted for according IWES over 200 TWh, which corresponds to a consumption of several months. The electricity grid currently has only a capacity of 0.04 terawatt hours, especially from pumped storage plants. In 2013, a plant with six megawatts of power was put into operation.