- Verdesis Solutions -

1. Biogas electrical valorization from 30kW to 1MW
2. Rotary vane compressor 4-6 bars for microturbines
3. Siloxanes treatment for piston engines and microturbines
4. H2S treatment for piston engines and microturbines
5. CO2 removal using breakthrough technology in PSA (Pressure Swing Adsorption)
6. Turnkey projects
7. Logistics - after sale - maintenance

- Generating electricity from biogas -

1 - What is biogas ?

The anaerobic decomposition of the plant or animal organic matters, under the action of bacteria and after run in different phases (hydrolysis, acid formation, methane formation) leads to the formation of a fermentation gas, mainly composed of methane (CH4) and carbon dioxide (CO2) but containing also other sparkling components as the oxygen (O2), nitrogen(N2), sulfurated hydrogen (H2S) as well as traces of water, aromatic compounds, organic fowls, particles of siloxanes, or even sulphured, chlorinated or fluorinated compounds.

This is how the banal domestic and industrial garbage is transformed in the landfill in a biogas containing 45 to 55% of CH4, whereas the methanization of the waste water treatment station's mud, and the agricultural biomass, produces a gas with higher methane content, up to 65%-70% of CH4.

Biogas is harmful to the environment The CH4 is 21 times more harmful than the CO2 for the environment, in term of greenhouse effect. It became clear, since the conclusion of Kyoto's agreements (December 1997), that it was necessary to make a particular effort for the control and the reduction of the methane emissions. It is among others since then, that most European countries have forced the dump operators to recover the biogas and to treat it (at least by elimination in flare).

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2 - Biogas a renewable energy

The "biogas" or "sewage gas" or "landfill gas", is typically composed of more than 50% methane "CH4". This level of methane allows considering its valorization with classical electrical generation…With methane content above 25%, allows considering its valorization with microturbine.

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3 - Electricity from biogas

With a high intrinsic calorific power (more than 50.000 kJ/kg), methane is comfortably transformable in secondary energy (steam or electricity) by its injection in gas engines and, insofar as the biogases include at least 45% of CH4, number of sites is equipped with electrical generation from biogas, since the beginning of the years '90, in Italy as in Germany or in Britain where one now counts on these only three countries, more than 620 MW of capacity installed.

The gas engines which permitted this development became more and more effective and, that it was about the Jenbachers, Deutz, Caterpillar or Waukesha engines, they are capable to treat biogases of various qualities.

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4 - Reciprocating gas engines limitations

However, two big limitations exist with the electrical generation from biogas by engine's: the minimal size of equipment and the minimal admissible content in methane of the treated biogases:

• The engine technologies being tried and mature, their investment cost is relatively moderate, in particular for the equipments of middle and superior size (>500 kW); on the other hand, considering the complexity of the operating mode of the biogas (and therefore of the significant variability of the availability rates of installations) and the high number of mobile pieces that a gas engine includes, the costs of exploitation of these equipments are high because relatively independent of the installation's size and can reach several euro cents by kWh in the case of installations <500 kW; • More unacceptable is the constraint to have a biogas containing at least 40 to 45% of CH4, to be able to valorize it by means of engines: Below a content of 45% of CH4, the trips are frequent, the yield low, and below of 40%, the engines don't run anymore.

this explains that the biogases sites valorized today are those, in activity or no, but where the layers are important and of good quality; for all others, that it was about the small sites (and by there one can include number of stations of water purification of less than 100.000 equivalent-inhabitant is a majority of the middle size sewage plant) or the aging or closed landfill where quantity of biogas and methane content decreases with the years and where, after some years of electrical generation, the sites are abandoned, , in the best of the cases the biogas is destroyed in flare, in the worse of the cases - and well too frequently again - it is vented in the atmosphere.

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5 - Verdesis answers

It is mainly to these sites that the Verdesis offer addresses: the ability of the micro-turbines to function with gases with low methane content - and, by there, to accept methane as low as 35%, as well as their maintenance costs reduced to the minimum, what can among others explain itself by the fact that, in the case of the Capstone turbines for example, there is only one mobile piece, in fact a privileged mean to valorize the biogas of these sites, means that the appraisal of the teams of Verdesis could put in work by a know how of the auxiliaries (dehumidifiers, compressors and filters) necessary to design and operate a microturbine plant.

One can add that the capability of the micro-turbines to produce particularly low NOx emanations permits, in the sites of dense urbanization, to valorize some biogases in acceptable conditions for the adjoining populations.

What is besides also valid as for the anti-noise norms (the Capstone turbines, with a guarantee of 65 dBa at 10 meters are already less noise than engines with acoustic container.

World largest microturbines farm in Lopez Canyon California.

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- Biogas filtration -

Applied Filter Technology / Verdesis solutions have proved to more than 60 happy customers to make money to their owners. Additional incomes from the higher operating hours per year and saving on the maintenance as well as on the insurance are the corner stone of the success story of the SAG™ product to filter the biogas.

Two Capstone microturbines C30kW + SAG™ filter

Results measurements on siloxanes have shown in Belgium :

Biogas inlet = 45 mg/m3
Biogas outlet = 0,005 mg/m3.

In addition the quasi total Volatile Organic Components are adsorbed leading to quasi natural gas quality to the engine.

Verdesis solution to capture H2S in the biogas is based on aerobic iron sponge. Adding value of Verdesis is to design an aerobic management to mutiply the H2S quantity retained on the iron sponge by a factor of 2 to 3 comparing to anaerobic reaction. This system has running cost two to 3 times cheaper than the best impregnated carbon solution.

Verdesis installation for drying and desulphurization

Verdesis service is based on a customized offer site by site, turnkey projects and a unique warranty in Europe.

1 - Why filter biogas?

The biogas, from landfill or residual of the fermentation of biomass, contains, besides methane (CH4) and carbon dioxide (CO2), other sparkling components as nitrogen (N2), the carbon monoxide (CO), the sulfurated hydrogen (H2S) or the oxygen (O2).

But, more pernicious again for the environment or merely for the good working of the equipment, are the aromatic, aliphatic or cyclic components, as well as of the siloxanes and silanes.

All present some nuisances in fact, to various titles:

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2 - The Siloxanes

One will especially insists on the siloxanes whose impact was practically unknown until recently and which, since some years, are at the center of the preoccupations of all operators of reciprocating engine units, on biomass or landfill sites.

Indeed, although one doesn't know the precise origin of the presence of these molecules, composite of silicon, carbon, hydrogen and oxygen, one could detect their increasing importance in the countries of the North more that those of the South, in the urban zones more that the countries and especially on the most recent sites.

Verdesis installation in Brussels - Belgium

These molecules, which are responsible for the formation of silica in combustion are mainly eliminated today, in an incomplete manner, by solutions of cooling or filtration by active coal, relatively inefficient because either very expensive (fast saturation of the active coals and therefore necessity to replace coals very often), either inefficient (if there isn't frequent tests on the threshold of the siloxanes before injection in the engines, one won't know when the filters are saturated and will therefore have abundant deposits of silica).

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3 - Maintenance constraints

Today, and before the solutions developed by Verdesis can be adopted, one of the few answers to this problem is to conduct frequent draining and to trap the silica in oils: this is how instead of stretching toward draining every 700 hours (biogas with low - or non content in siloxanes), a lot of operators, confronted to this problem, proceed to closer draining, often even every 200 hours, while continuing besides, for a lot of them, to not being able to hold the threshold minima in required siloxanes content by the manufacturers.

It is following research linked to the treatment of these problems in the setting of the optimization of the exploitation of the micro-turbines in the setting of the biogas applications that Verdesis could finalize, in link with Applied Filter Technology, the applicable solutions to the systems of power generation from biogas and landfill gas.

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4 - Filtering solutions

The motorists, confronted to the problems of emissions threshold for the emanations of NOx, developed clean solutions, that it was about the Leanox of Jenbacher or other processes of post-combustion, more or less inspired of the solutions for diesel engines and of the efforts pursued in the automobile industry; one will mention the Caterpillar equipped of the ACERT® systems, or other catalytic reduction solutions.

However, and in spite of the constant improvements in this field, the lowest rates noted following the setting up of these systems remain the order of 100 mg/Nm³, that is to say all things considered, far enough from what one can get with micro-turbines, as could demonstrate it the teams of Verdesis, in association with EDF R&D.

One will evoke thus:

Verdesis solutions runs to sites equipped either with reciprocating engines as well as micro-turbines since the residual silica of the incomplete combustion of the siloxanes/silanes damage as much the engines that the turbines. It is besides on the occasion of studies on the means to protect the turbines efficiently against this type of aggression that the teams of Verdesis, in close contact with Applied Filter Technology, of Snohomish (WA, United States), finalized solutions for treatment of these pollutants, applicable as well on "simple" sites as the water purification stations that on more complex sites as the dumps where the quality of biogas vary enormously not only in time but also from a part of the dump to another.

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