Environmental Engineering Reference
In-Depth Information
index is the ratio between heating value of the fuel gas and its specific
gravity.)
Calibrated volume metering with volume conversion calculation to
standard conditions.
.
.
Gas conditioning facility for obtaining the required combustion
characteristics by the addition of liquefied petroleum gas (LPG; see
glossary, Section 16.10) and/or air if the gas quality cannot be obtained
by another method.
.
Provision of data relevant to the network operator (remote monitoring,
data transfer).
Network connection pipeline for feeding the treated biogas into the
natural gas network.
.
Odorization of the biogas is an additional process. It is carried out
according to DVGW G 260 (DVGW, 2008a) and G 280 (DVGW, 2008d)
and is necessary if the biogas is fed into an end distribution network.
Capacity bottlenecks can occur in end distribution networks and require
feeding the gas back into an upstream network section of higher pressure.
Sometimes, when gas is transferred into a sensitive section of the network,
the gas must be deodorized. This can be avoided by controlled odorization
of the biogas using a demand-driven odorization facility.
Generally, biogas feed-in stations differ mainly in the quality of the
components, the redundant design of some or all components and the local
conditions (grid pressure, gas quality, distance of the biogas facility to the
gas network), the type of gas compression and conditioning. The main units
and components of a biogas feed-in facility are now described.
16.3.2 Gas compression
The design of the compressor depends on the grid pressure of the natural gas
grid (delivery pressure) and the gas upgrading system (inlet pressure). The
higher the pressure difference the more power is necessary. The work the
compressor must perform and therefore the cost of compression increases
by the power of two of the pressure difference. When selecting a suitable
compressor for a feed-in station, it should be noted that oillubricated
compressors may contaminate the biogas. According to DVGW G 260
(DVGW, 2008a), the biomethane must be technically free of oil vapor and
dust. Oil-free compressors are thus preferred; although they are free of
contaminants, more methane might be lost and equipment wear is distinctly
higher. In many facilities, lost gas is returned to the biogas treatment
facility. The efficiency of a dry running compressor is also lower.
Furthermore, it should be noted that the compression of steam-saturated
gas produces water, which must be removed.
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