Re: GAS-L: Gasification tests

[Peter Singfield <snkm@btl.net>]

At 09:01 PM 1/6/2002 EST, CAVM@aol.com wrote:

>http://www.nf-2000.org/secure/Fair/F826.htm
>
>"Demonstration of small bio-power plant for rural application"
>
>This site gives some very interesting data on gasification.
>

Have appended this article.

Interesting -- when all the "smoke" settles -- 20% over all efficiency at
some astronomical costs!

And still a problem with "dirty" fuel leading to unreliable operation -
-and a humongous servicing head-ache.

All could be so easily avoided by going with a small refrigeration working
fluid Rankine Cycle device. And getting better over all efficiencies -- and
at much better prices.

But beating dead horse to get more performance is the rule of the day when
it comes to gasification of biomass for power!

At present -- Ormat produces 250 KWH "ORC" devices that are easily coupled
to a simple fire tube boiler -- thermal oil heat transfer (Atmospheric
boiler pressure) -- that results in around 18% efficiencies with room for
improvement -- and runs for ever and one day with very minimum of
maintenance -- and for a fraction of the costs presented below. And
requires no gas cleaning! (Or -- as far as that goes -- a gasifier!!)

But no -- dead horse mentality prevails ---

Peter Singfield / Belize

*********appended article ******************

Final Report Abstract 
Source: Final report, 1999 

Consortium: The project was co-ordinates by Meurer Maschinen GmbH+Co KG,
Fursteneu (Germany), in partnership with Stork Comprimo, Amsterdam (The
Nethedands), BIBA, University of Bremen (Germany), Joanneum Research,
Institute of Energy Research, Graz (Austria), FH Hannover (Germany), TFH
Bochum (Germany). 

Abstract 

Objectives: The objectives of the project were to design and to operate a
demonstration unit for the gasification of rural feedstocks and to produce
electricity. 

During the first year the design and the construction of the plant were
finished and the operation of the plant began. During the second year the
operation of the plant has been continued and the operation demonstrated
the production of electricity. The result was that the plant produced a
cold, clean and combustible gas as required for gas-motors. The engine
together with the generator produced electricity for the grid. Nevertheless
some goals like the high efficiency of e.g. 40% could not be proved as
expected. But the SME - Meurer Maschinen - got helpful information for the
production of such plants and the market situation in the field of
small-scale CHP production plants (CHP =. Combined Heat and Power
Production). Users can get data for planning and further operation of
Bio-Power Plants from the project or the producer. 

During the third year of the project the operation has been improved, in
that way that the operation was stable, more safe and more efficient. One
of the main objectives to produce power to the grid could be demonstrated,
also to outstanding experts. 

The third year of the project was the most successful year in the projects
time, because of the continuous development of the design especially of the
gas-cleaning system, which enables the plant to demonstrate the production
of a clean and combustible gas, which is the basis for the contracted
demonstration character of the plant. 

because of the key decision to use an electrical precipitator for
de-dusting of the gas and for tar-removal, to protect the engine. 
because of the duration of a long consisting demonstration run of about 150
h together with the engine/generator unit, that was possible with the
activities in the field of gas-cleaning design and with the designed and
constructed precipitator. 
Especially the introduction of the new electrical condenser was the step to
enable long engine runs. It can be assumed that the gasifier operated more
than 2000 hot operation hours and together with the engine more than 400.
The Electro-condenser improved the operation tremendously. The longest
operation period was done during the time between the 1.7. and the 9.7.99
within 150 hours of steady operation. Six further longer runs P01
demonstrated in the time of 19.7. to the 25.9.99. 

At the end of the 3rd year nearly all contracted objectives have been
realised by the project-partners. Only partially realised is the proposed
power of 200 kwel and the total efficiency of 30%: One of the important
objectives has been to install a 200 kW CHP. 

A proposal from an external supplier was received. After long negotiations
the supplier would not guarantee the proposed power output if the engine
was used with leangas, nor would they guarantee a long term running time of
the engine with leangas (particle and tars have been the critical point),
nor would they modify the engine, which was built for natural gas, in a way
so that it could be used for leangas (leangas has an energy content of 4
MJ/m3 and is thus nearly ten times lower in its caloric value than natural
gas). 

The price of the offered engine (250,000 Euro) was to high for the projects
budget, that had an overall budget for hard-ware of 467,000 Euro. The
specific cost can be calculated from this price as 4000 Euro/kW, which
appears too high for CHPS. The contract-negotiations with the proposed
supplier were thus closed. Hence, the project group decided to find a used
engine for the first runs. 

That this decision was right, was confirmed to the partners, when the
engine crashed totally during the first day of use. This event endorsed the
need to improve the gas-cleaning part of the plant. 

The produced power of the 5 1 engine requiring 120 m3/h leangas at 25 kW
(average) 30 kW (max.) fell into the power range that had been identified
as that required by many potential customers as a result of a two year
market survey showed. 

The project held meetings at which extensive discussions centered on the
possible use of a Diesel engine (for which 30 % of the fuel would be
supplied as diesel oil, to supplement the leangas, resulting in a higher
efficiency) rather than an Otto (spark ignition) engine. However, it was
decided to use the Otto engine, in part since the EC informed the project
that the use of fossil energy was within the remit of the FAIR-project. 

Activities: 

In the third year the project demonstrated the operation of the plant and
produced power for the grid, it was the most successful year. 

Progress: 

The plant succeded as a demonstration, that could be easily developed as a
commercial plant. This would require a longer run, of around 150 hours, to
enable the SME involved to give guarantees to customers. 

Achievements: 

Results and discussions indicate that the proposed gasification scheme is
valid for the production of power with an Otto cycle-gas engine. The main
advantage compared with other schemes is the two stage biomass gasification
process. In the ARCAS scheme a thermal tar cracking step is used as the
second stage of gasification. The project has learnt that other research
groups have also tried to introduce such a second reaction stage. In all
known projects a catalytic stage will be introduced, but this method is not
as efficient as an E-filter. 

The results of the test- runs prove that a second stage of gasification
decreases the tars. To increase the life-time of the engine partner 01
decided to design and to build an electrical condenser in order to decrease
the moisture and the tars of the gas. This plant started operation with the
new filter at the end of 98. 

The introduction of this apparatus improved the total situation: The gas
was much cleaner and had less humidity. The operation of the engine was
much better, resulting in stable and safe operation. The main demonstration
goal was reached over the period of January to March 99. Long periods of
running were demonstrated. 

The results of the demonstration runs can be summarised as follows, with
information presented showing the yield of gas and power as well as the
qualities of the produced raw gas and of the cleaned gas. 

Fuel Wood-chips: max. length 30 mm, air-dried, moisture content 10-30% 

Fuel-through-put: average: 40 kg/h Max.: 50 kg/h 

Gas production average: 90 m3/h Max.: 120 M3/h 

Heating value: 4 M.J/m3 

Tar/dust-content: in the raw-gas 100 mg/m3, 10 mg/m3 in the cleaned gas 

Humidity (water-content) of the gas: 25 g/m3, relative humidity 90% 

Temperature: 40°C 

Dry gas analysis: CO: 18 vol%, CO2:14 vol%, H2: 12 vol%, CH4: 1 vol% 

Methane Number: 120 

Power of the engine/generator-system: 25 kWe (average) 30 kWe (max.) 

Specific Power yield per cylinder volume: 5 kW/l 

Efficiency of the engine/generator system: 20 % 

Specific wood consumption (basis air dried biomass): l.6 kg /Kwh 

The plant, as designed and realised is a complete system. It consist of
following elements : 

Raw material bin 
The gasifier (concurrent, two stages) 
Gas cleaning (two stages) 
The gas/air - mixing system 
The motor/generator system 
The converter for sending power to the grid 
The system is controlled automatically, with: 

Level controller for the solids e.g. in the gasifier 
Non manual ignition 
Lambda-sound for the control of the gas/air - mixer 
Overall computer control and monitoring of the plant 
The plant works in a safe manner and can be produced in the workshops of
Meurer Maschinen at an economic cost. The plant demonstratee the
feasibility of small scale use of biomass for power generation. 

Future Prospects and Conclusion: 

Biomass: There is still now no normal commercial market for biomass, but
enough biomass is present in all regions. The most important fuel is wood
in different kinds also some other agricultural (chopped straw like
sorghum, which was used in big quantities )and industrial residues (The
plant used residues of the coffee roasting industries and paper pellets).
To use chicken manure made no sense, because this material will .be used in
digesters. Rape cake should not be gasified it can be used for pig
breeding. Wood is available not only in regions with large forests e.g.
like in the countries of the Alps or in Scandinavia, also in agricultural
regions and in big towns, too hedges, trees in parks, gardens, roads etc.) 

The humidity of biomass, particle-size: The used biomass for CHPs should
contain only 10 -20 % of moisture, that means the biomass should be
air-dried: The high O/H - ratio of biomass causes high quantities of
formation - water, together with the humidity a gas with dew points of e.g.
70 % will be produced and that means high quantities of contaminated waste
water will occur, if the gas is used in a cooled status. The used particle
size of <30mm is valid. Air dried leaves, branches or stems have to be
shredded. Not all machines can realise the required size. However, within
the project expertise was developed to enable biomass to be shredded in the
correct way. 

The gasifier - concept: The bottom fired, stirred gasifier concept is
valid. The thermal cracking step is valid as well. Some authors have
suggested that a part of energy will lost according to the following
reaction: 

CO + 0.5 O2 = CO2 

However, project results suggest that additional fuel will be formed
according to equation 

CO2 + C = 2 CO 

The gas cleaning system: The need for a gas cleaning system depends on the
requirement of the engine. Two extreme options are possible: 

to use warm gas for the engine: the project started with this idea but
found that no engines capable of using crude gas are available 
to use cold and cleaned gas: the project decided to go this way. 
The key solution was the development of an electrical precipitation process 

The prime mover: The ARCAS- Project developed a gasification plant for
producing a cold and clean gas, in order to use a IC - engine (not a
turbine, but a commercial piston engine) as prime mover. In the beginning,
in spite of considerable discussions with experts inside and outside the
project, it was not clear which type of engine was the best for a small
bio-power-plant. 

The engine/generator unit had an energy yield of 20%. On the basis of
results from other systems, especially when operated at low rpm (1500),
this is reasonable. It was found experimentally that the engine used in the
project had mechanical losses of 5kW. This lower efficiency contributes to
a reduced power yield. However, the above efficiency is based on use of
electrical energy only, the heat is ignored. If the heat was used, the
efficiency could be raised to 50 to 60% 

The results of the project enable the SME Meurer Maschinen, to build and to
offer a commercial plant with a capacity up to 50kW. 


----------------------------------------------------------------------------
----
Progress Report May 1997 
Introduction The report describes the installed Arcas-Gasifier, for which
the basic design has now been completed. It describes the definition,
design and construction of the plant as well as the first phase of the test
runs.

Activities The following parts of the project were carried out:

the P&I scheme was laid out together with guidelines for sampling and
analysing tar, condensates and particulates 
a proposal for supply of buffer was made along with suggestions for those
measuring instruments that had to be installed and where they have to be
located 
analysis of four biofuels enabled the result to be used in building of the
dryer and the shredder, indicated that the test runs should be started
using wood 
the specifications for the tar filter were calculated, in order to reduce
the tar content to a level suitable for the motor 
a gas cooler was built since the motor could not cope with hot lean gas 
The tar filter and the gas cooler were designed in consultation with
representatives of motor producing companies. The resulting tar filter, the
continuous adsorber, the gasifier and the gas cooler were constructed by
Meurer Maschinen.

Progress Several changes in design have been made, resulting in a new flow
scheme. Wood which is stored with an approximate moisture content of 50% is
sent to the shredder. Before the wood flows into the continuous adsorber it
is dried to drop the moisture content to 15 %. As a result of this only 200
kg of wood per hour (rather than 340 kg as previously estimated) is
required. The wood is then carried to the continuous adsorber and from here
to the reactor. The produced lean gas of about 500 m3 per hour is sent to
the continuous adsorber. The lean gas is cooled by a gas cooler and passed
through the tar filter that is filled with activated carbon during the test
runs.

This is followed by a dust filter, that is meant to remove all the dust
particles that pass through the tar filter. The clean lean gas should then
be sent to the motor. Since the motor company cannot build an engine
without having the gas components of the produced lean gas the question of
the motor been postponed and hence the motor cannot be described as yet.
The goal of the project is an engine that works with gas from biomass alone.

Following a few test runs, during which the tar content and composition of
the lean gas will be established, the motor/generator unit will be ordered.

Discussion

Although there are additional measurements still to be undertaken, it is
unlikely that tar will be removed completely, most probably it cannot be
reduced to less than 100 ppm. However, an unofficial statement of a motor
company indicated that 40 ppm of tar would be required. The test runs will
show whether the required 40 ppm can be achieved with the flow scheme
described above. 

An alternative to this flow scheme would be the substitution of the gas
cooler and the tar filter by an electrostatic precipitator.

Future Activities

It has been decided to operate the gasifier to measure the tar content as
the next step in order to propose the engine. Then, the engine will be
ordered and operated with the produced lean gas. Since the aim of this
project is to operate a demonstration plant, completing long term runs of
the motor, the tar problem has to be considered carefully.

 


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