Example for purification of a biogas
and obtaining pure biomethane
innovative "One-pot" process consists in capturing gaseous
pollutants in a physicochemical treatment whose liquid
effluents are subsequently digested by the aerobic bio-purification
process in the treatment plant.
process of absorption (capture) and organic chemical
modification of Volatile Organic Compounds (organic
This operation is carried out in a single operation
on a collection installation by physicochemical washing.
final destruction of the capture products after the
simultaneous process of absorption and chemical modification
This ultimate operation (B) is carried out in a biological
treatment plant. The organic compounds present and formed
During the condensation reaction are digested by the
process of natural aerobic bio-purification of the purification
originality of the process resides firstly in the choice
of the reagent which combines with the pollutants to
be treated and secondly in the final natural destruction
in the wastewater treatment plant that does not generate
any new gaseous pollution.
example below describes the treatment of 100 m3 of biogas
from the methanisation of sludge from an urban sewage
100 m3 of biogas consists of:
m3 of pure methane (biomethane) (3.123 mol)
m3 (about 60 kg) of carbon dioxide (CO2) to
be removed and recovered (1,338 moles)
kg of hydrogen sulphide (H2S) to be removed
Possibly traces of siloxanes
amounts of base and reagent are calculated on
the basis of Spreadsheet
and load sheets .
Absorption column 800 liters (column + tank),
Height: 3 m,
base area: 0.28 m2 (diameter 60 cm), plate lining,
mist eliminator at the air outlet.
Fluid circulation pump adjustable from 0 to
polluting effluent feed valve from 0 to 1000
load for a batch operation:
: 300 L.
30% soda: 390 kg
reagent : 7.3 kg or 18,4 kg of solution à
operation is carried out over a period of 4 hours with
a gas flow rate of 25 m 3 / h.
The end of the reaction is controlled by pH-metry (about
8.5), and the absence of H2S verified with lead acetate
The reaction medium is odorless and the suspension of
CO 3 Na 2 (carbonate of soda) is separated on a centrifuge.
capture and transformation of the 30 m3 of CO2 present
in the biogas yielded in principle 142 kg of sodium
carbonate (Na2CO3). On this theoretical weight, 100
kg are obtained after drying (70%), which can be used,
for example, in cement plants in the cement manufacturing
+ Na2CO3 = CaCO3 + 2 Na+ + 2 OH- (See
remaining 30% soluble in the colorless and odorless
reaction medium rejoin the wastewater treatment system
STEP before being discharged into the natural environment.
This release helps compensate for the pH of surface
in the oceans, which has been declining for years, from
8.25 to 8.14, and due to the increase in anthropogenic
CO2 emissions in the atmosphere.
At the end of the reaction, sodium carbonate may also
be advantageously displaced by calcium chloride
in order to obtain practically insoluble calcium carbonate
according to the reaction:
Na2CO3 + CaCl2 --> CaCO3 + 2 NaCl
it is not desired to recover the carbonate, the soda
will be replaced by the potash. The carbonate of potash
soluble in the reaction medium, and will not precipitate,
as carbonate of soda has done.
The clear, colorless and odorless reaction medium is
evacuated to the all-water pit to be subjected to the
bio-purification process of the purification plant.
flux calculation worksheet to determine the quantities
calculation of the operating costs for evaluating the
economic potential of the process:
this test, it is clear that for the destruction of H2S,
the treatment with bleach is three times more expensive
than treatment with GASWASH system.
Treatments with ClO2 or H2O2 are even more expensive:
10 times more expensive.
example of biogas treatment includes:
elimination of H2S.
(complete elimination of CO2).
lowering of 4% water methanization at 40 ° C. (1 to
total removal of siloxanes and organochlorines or
fluorinated if present in trace amounts.
In this example, GASWASH system was used to purify 100
m3 of biogas which supplied 70 m3 of pure biomethane
also to capture and remove 30 m3 of carbon dioxide and
to eliminate 0.4 kg of H2S.
also the examples of the DAVID Process- Odors
on the 100 m3 of biogas treated with GASWASH process
100 m3 of biogas produced from sludge from STEP avoided
the production and release into the atmosphere of
230 kg of CO2 responsible for global warming during
of these 100 m3 of biogas, the capture of the 30 m3
of CO2 present after sludge methanisation provides between
and 100 kg (70%) of sodium carbonate (Na2CO3) with the
complete elimination of H2S (Hydrogen sulphide) and
traces of volatile compounds.
30% soluble in the reaction medium rejoin the sewage
system before being released into the natural environment.
release helps compensate for the pH of surface waters
in the oceans, which has been declining for years,
from 8.25 to 8.14, and due to the increase in anthropogenic
CO2 emissions in the atmosphere.
This capture of 30 m3 of CO2 by the GASWASH system avoided
the release into the atmosphere of 60 kg of additional
CO2 responsible for global warming.
70 m3 of methane of purity greater than 98.5% (biomethane)
obtained can be used as an energy source or
as a precursor for the manufacture of biohydrogen, for
example with the VABHYOGAZ
of pure reagents for GASWASH treatment:
of 100 m3 of biogas: 0,224 € / m3 or for 70 m3 of
pure biomethane: 0,32 € / m3
the 30 m3 of CO2 present in the biogas and disposed
of: 0.75 € / m3