Dahlman OLGA

OLGA performance

The OLGA process proved itself in many lab & pilot scale tests. The performance of OLGA is presented by the results of the 500kW(t) durations tests. Objectives of these tests were to demonstrate that the OLGA process is stable and reliable, that the gas quality after OLGA is on specification for a gas engine or gas turbine. Further, the test is also used to study specific duration effects.

 

Process temperatures & dynamic gas composition

The graphs on the right show the process temperatures and dynamic gas composition data from the duration test. Both graphs show that the process has been very stable. Operator action was limited to a guard function. Process control was automatic and stable.

 

Gas composition & measured performance

The table below summarises the data from the gas analysis. The gas composition can be seen as typical for a CFB gasifier. NH₃ and H₂S concentrations are low as clean wood chips were used as biomass feedstock. The tar and naphthalene data show good efficiencies (99%), phenol was under the detection level.

Tar dew points were reduced to levels well below target (<10 °C)

Typical gas composition		Raw gas	After OLGA
H2	vol% dry	7,2	7,4
CO	vol% dry	17,4	17,4
CH4	vol% dry	4,6	4,6
CO2	vol% dry	15,5	15,5
C2H2	vol% dry	0,2	0,2
C2H4	vol% dry	2,0	1,9
C2H6	vol% dry	0,1	0,1
N2	vol% dry	51,3	52,0
H2O	vol% dry	14,6	1,9
Benzene	ppmv dry	3511	2424
Toluene	ppmv dry	448	158
NH3	ppmv
H2S	ppmv	10	10
Total tar (accuracy 200 mg/Nm3)	mg/mn³ dry	16855	91
Naphthalene	mg/mn³ dry	4023	35
Phenol	mg/mn³ dry	386	< 2,5
Tar aerosols (incl. dust)	mg/mn³ dry	--	< 5
Tar dew point (measured)	° C	≈ 350	≈ 1
Tar dew point (calculated)	° C	≈ 350	2
Tar dew point @ 2,5 bar (calculated)	° C	--	14

 

Water condensate composition

The figures below shows the water condensate composition. After OLGA a water quench / condenser is installed. The condensate analysis show some remaining BTX and naphthalene. BTX removal is not a target of OLGA as these compounds do not form a problem for downstream equipment. In future tests OLGA performance on naphthalene will be optimised to reach even better results.

Tars in water after OLGA
Benzene	mg/l	49,9
Toluene	mg/l	3,25
Ethyl benzene	mg/l	0,012
m/p-Xylene	mg/l	0,022
o-Xylene	mg/l	0,024
Naphtalene	mg/l	10

 

Conclusion 500 kW(t) duration test

• The whole biomass gasification line, including OLGA is successfully operated for more than 650 hours. The OLGA process showed to be stable and reliable; availability of OLGA was 92%.
• The tar related problems in the piping before OLGA are an important lesson. Pipe geometry, particularly between the cyclone and OLGA should be well considered during plant layout design. Before OLGA the tar problem is still present!
• The quench / condensation water after OLGA proved to be free of  “problem tars.”  The small naphthalene and BTX concentrations that remain are not very difficult or cost intensive to treat.
• Final inspection of the gas engine showed that it was completely clean; no carbon deposition at cylinders and valves. The gas engine lube-oil quality was investigated and shown to be similar to an engine operated at natural gas.