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Initial Post: 08_05_2008
Alternative energy sources to the
utility corporations are biofuels:
ethanol, and
biodiesel, - the production technologies of which have been
effectively analyzed for development; and waste
and virgin vegetable oils. All these provide the fuel that is usable
for distributed power generation system as well as for home heating. Irrespective of which of these
bioenergy sources is
actually specified for adoption as a steam generator biofuel, a BioEnergy Steam Generator
can be developed based on any of these biofuels, and interfaced with the existing
heating delivery lines, followed by the implementation
of the biofuel process
system.
There have been the analyses -
to that end of producing one form of energy source or another,
though all are of the
Combustible Energy Sources categories - of
several biotechnology processes: The analysis of the controlled
microbial digestion of
industrial waste whey into ethanol; The analysis of the
recycle of waste oil into bio-diesel fuel; The analysis of the
recycle of
edible wastes into liquid biofuel mixture of alcohols: Ethanol,
Butanol and Propanol; and gaseous fuel mix carbon dioxide, methane
and hydrogen. These energy sources then serve the collection from
which the steam generator design is being based.
BioEnergy Steam Generator Design
The biofuel steam generator
technology consists of two main sections but are integrated
together:
- Biofuel Combustor
- Water Boiler
The
Biofuel
Combustor though fuel
specific holds the fuel and injects it into the Combustion Chamber
where the fuel droplets under combustion resulting in effluent gases that are of high
temperature. The Combustion Chamber is of a furnace design, that
enables the chemical reaction to occur at intense temperature while
allowing thorough mixing of the hot gases before being discharged
into the water boiler section. The Water Boiler is simply mostly a
heat exchanger of the Vertical Thermosyphon Reboiler, VTSR,
category.
Effectively, the
mission-critical equipment
is the Biofuel Burner. The equipment configuration is specific to
the fuel of target for burning, given that the fluid dynamic
properties of each fuel is different. These properties directly
impact the performance of the combustion burner - the device that
actually delivers the fuel into the combustion chamber - and as such
is designed to accommodate the characteristic fluid properties
of each fluid type as well as mixed fuel types as per the fuel
produced from edible waste. There are available |
for deployment three different
types of Fuel Combustors:
Vegetable Oil Fuel Combustor,
Syngas Fuel Combustor,
High Thrust Bio-alcohols Combustor,
and Bio-diesel Fuel Combustor,
and even domestic Edible Wastes Biogas Combustor.
As already noted, the Water
Boiler is simply mostly a heat exchanger of the Vertical Thermosyphon Reboiler, VTSR,
category. In consistence with the features of a VTSR the Water
Boiler ensures that the feed-water boils into steam, is vented out
for use and is also
replaced continuously as the level of the water in the tubes drops. As such the VTSR is of such size as to meet the required heat load
evaluated for the given application. The outlet of the water Boiler is fitted
with flanges and adapters for the flanges to allow for a smooth
retrofit with existing heating piping-system.
The performance of the Water
boiler is intimately tied to the fuel combustor deployed to provide
thermal energy. The choice of the specific combustor for deployment
therefore is determined by the available technical support skill,
available biomass for the production of the biofuel feed for the
combustor and efficiency specifications among other
application-specific stipulations.
A salient consideration of the
application-specific needs is high rate of heat transfer to the
water in the VTSR. High rate of heat transfer in Heat Exchanger is
known to be directly dependent on the rate of flow of the hot fluid,
the inlet temperature of the hot fluid, and the direction of flow
relative to the cold fluid - in this case the water to bring to
boiling as a fluid-particle travels along the direction of flow.
While the last factor is not directly impacting factor on the choice
of a combustor, the former has direct impact. For the purposes of
achieving optimal heat transfer for the steam generation, the
combustor must provide effluent hot fluid - the effluent gases of
the combustion - at a very high temperature as possible and at a
high flowrate as tolerable.
The inlet temperature
contribution fortunately can be addressed readily for all
combustors. For the
burner-based fuel combustors, the inlet hot fluid temperature
can be adjusted by tightly regulating the air flow into the
combustion chamber to a flowrate that is no less than is required to
ensure complete combustion but as high above as needed to provide the inlet temperature
as required. In the case of the flame-based combustors, this limit
of flowrate is set by the velocity at which the air blown into the
combustion chamber blows out, as extinguishes, the flame. For any
flowrate beyond that volume then the flame has to be protected in a
flame shield or the effluent hot gas can be mixed |
with more air prior to being fed into the Water Boiler. In the case
of
turbine based fuel combustors, the hot fluid inlet temperature
can be controlled by one of two approaches: By tightly regulating
the volume of inlet air driven in by the compression impellers as to
provide the required volumetric flowrate or by mixing with more air
after the combustion. However, the second approach is rarely ever
necessary as just about every required combustion effluent
temperature could be achieved through the regulation of the air
inlet-flowrate into the turbine.
Although the design here has provide a consistent and
well-integrated technology components, in the most restricted cases however, were the
utility corporation preferring to keep existing steam generator -
contextually, water boilers, may only
need to replace or modify the fossil fuel combustion burner that is
currently deployed, in order to implement a
bioenergy distributed
power generation system. |
