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Other Blending
Applications |
Piston Operated Mixers (POM)
for other Applications
POM-30, POM-40, POM-60, POM-80, POM-100 |
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In addition to the
"traditional" applications of LP/Air blending in backup, standby,
and PeakShaving
systems, the AES POM blenders can also be used for a variety of
other applications where reliable performance, ease of use, high
turn-down ratios, adjustable blending ratios, and low maintenance are
desired.
The following
paragraphs describe just a few of the many installations where POM
blenders have been used successfully. The main feature that these
applications have in common is that two dissimilar gasses needed to
be blended at an adjustable ratio.
The AES POM blenders can blend any two or more gasses safely and
reliably. |
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Sample Applications
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Digester Gas Augmentation
System |
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Situation:
Waste Water Treatment Plants produce "Digester Gas" (DiG) as a
by-product of the waste water treatment. The DiG is used as fuel for
multiple reciprocating internal combustion engines to drive air blowers and/or
electric generators, or as fuel for boiler plants.
Periodically (for example during sludge removal), the DiG production
does not match the consumption of the engines or boilers. This is
typically handled by turning off one or more engines, which invariably
leads to considerable amounts of excess DiG (more than the engines or
boilers can consume, but not enough to add another engine). The excess
DiG must be flared off to avoid pressure build-up in the digesters.
Efforts are now being made to eliminate the waste of energy (the flaring
off of the excess DiG), and instead to add "just enough" DiG replacement
gas to allow the operation of an additional engine or boiler.
Solution:
Installation of a POM blender that generates a NatGas/Air blend with
properties that match the properties of the Digester Gas.
Operation:
The POM blender is supplied with air from a high-efficiency blower
and with unregulated NatGas (10...50 psi). The blender discharges the
DiG replacement gas at a higher pressure than that of the DiG (keeps the
blender and the piping system small = less expensive). A "Tie-In
Regulator" monitors the pressure in the gas supply line from the
digester to the engines/boilers. If the DiG production is less than the
consumption of the engines/boilers, the resulting loss of DiG pressure
is detected by the Tie-In Regulator, causing it to open and to inject
"just enough" DiG replacement gas to meet the demand of the
engines/boilers, avoiding the need to flare off any DiG.
When the pressure in the digesters recovers, the Tie-In Regulator closes
and the engines/boilers are only supplied by DiG.
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DigesterGas Augmentation System
Low-Pressure Example
Click for PDF file (40 kB)
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DigesterGas Augmentation System
Engine-Supply Example
Click for PDF file (69 kB)
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DigesterGas Augmentation System
GasHolder Example
Click for PDF file (47 kB) |
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Digester Gas Enrichment and Backup |
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Situation:
Waste Water Treatment Plants produce "Digester Gas" (DiG) as a
by-product of the waste water treatment. The DiG is used as fuel for
reciprocating internal combustion engines to drive air blowers and/or
electric generators. The air from the blowers is used in the digester
process; the electricity from the generators is used in the plant;
excess electricity is sold to electric utility companies.
The heating value of the
DiG depends largely on the type of waste that is being processed, and
can therefore vary widely. These variations require the engines to be
set up in a very "forgiving" mode, resulting in diminished efficiency
and increased exhaust gas emissions.
Occasionally, the supply
of DiG is interrupted due to equipment maintenance. This leaves the
engines without fuel, which leaves the digester process without the air
from the blowers, which is needed to stimulate and boost the digester
process.
Solution:
Both goals, stabilization of the properties of the DiG as fuel for the
engines, and backup fuel supply for times when DiG is unavailable, can
be covered with the Installation of a single POM blender with Automatic
Gas Properties Control (AccuBlend™).
Operation:
The POM blender is supplied with NatGas, with Digester Gas, and with
Air.
If DiG is available from
the waste water treatment process, the POM blends NatGas and DiG at a
varying ratio that results in very stable fuel gas properties (Calorific
Value) for the blower/generator engines.
If DiG is not available
from the waste water treatment process, the POM blends NatGas and air at
a ratio that results in a mixed gas that allows the blower/generator
engines to operate at their highest efficiency with the lowest possible
emissions.
A gas analyzer at the
outlet of the POM measures the properties of the NatGas/DiG or the
NatGas/Air mixture.
If the gas analyzer
detects a deviation of the gas properties from the desired values, the
AccuBlend™ controller automatically adjusts the position of the piston
in the POM, thereby changing the blending ratio, and re-establishing the
desired properties. |
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BioGas Enrichment and NatGas Conditioning |
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Situation:
A small town in Europe is supplied with locally produced "BioGas"
from an agricultural operation. The BioGas is used in private homes for
cooking and heating, and by several industries for heating and process.
The heating value of this BioGas is slightly (~10%) below the heating
values of normal NatGas.
For most of the year, the BioGas production is sufficient to supply all
homes and all industries with gas. However, in winter the gas
consumption is frequently greater than the BioGas production, and in
summer the BioGas production is occasionally greater than the usage in
this town.
Challenge:
- Provide a solution that supplies the additional gas in
winter.
- Provide a solution that avoids wasting excess BioGas (excess
BioGas used to be flared off) by raising the
heating value of the excess BioGas in summer so that it
can be re-injected into the regional high-pressure
NatGas grid.
Solution:
Install POM blender to reduce the heating value of NatGas from the
regional high-pressure grid so that it is compatible with the properties
of BioGas, and inject it into the city grid at times when the BioGas
production is interrupted or is insufficient to meet the demand.
Install a second POM blender to increase the heating value of the excess
BioGas in summer so that it is compatible with the properties of NatGas
and can be re-injected into the regional high-pressure NatGas grid.
Operation:
When the control system detects that the pressure in the low-pressure
city grid increases above an adjustable setpoint (indicating that BioGas
production exceeds consumption), the BioGas/LPG POM blender is turned ON
automatically. BioGas from the city grid is blended with LPG vapor to
increase its heating value, is compressed, and then re-injected into the
high-pressure regional NatGas grid.
The BioGas blender stays
online until the pressure in the city grid has fallen below a second
adjustable set-point and then turns itself automatically off.
When energy consump-tion
exceeds the available BioGas, the pressure in the city grid will fall
below an adjust-able setpoint. This is monitored by the control system,
which turns the NatGas/Air blender ON.
The NatGas/Air blender
draws NatGas from the high-pressure regional grid, blends it with air to
reduce its heating value, and injects it into the low-pressure city grid
to provide the balance of gas demand.
The NatGas/Air blender
stays ON until BioGas production is sufficient to raise the city grid
pressure above an ad-justable setpoint.
BioGas/LPG blender and
NatGas/Air blender are always "ready to go" and do not require on-site
human intervention to start producing gas. The entire system is
monitored remotely and can also be started manually through commands
from the remote site. |
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Landfill Gas Backup |
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Situation:
The dryers in the paint shop of an automotive manufacturing plant
are supplied with low-BTU Landfill Gas (LFG) as the primary fuel source.
Occasionally, the supply of LFG is
interrupted due to equipment maintenance at the landfill site. Since the
paint process is crucial to the continuous production output of the
plant, a backup gas source is needed.
Solution:
Installation of a POM blender with Automatic Gas Properties Control
(AccuBlend™).
Operation:
The POM blender is supplied with NatGas and with Air. The POM is
pre-set to a blending ratio that results in highly "diluted" NatGas/Air
mixture with a CV that resembles the properties of LFG.
A GraviBlend™-3 gravitometer at the outlet of the POM measures the
properties of the NatGas/Air mixture.
If the gravitometer
detects a deviation of the gas properties from the desired values, the
AccuBlend™ controller automatically adjusts the position of the piston
in the POM, thereby changing the blending ratio, and re-establishing the
desired properties.
The system is
"always-ON". Two Fisher 1098EGR regulators monitor the pressure in the
LFG supply line. If the pressure drops below an adjustable setpoint, the
first regulator starts opening and begins injecting NatGas/Air into the
fuel gas line to the paint shop. If the first blender is unavailable
(i.e. for turned off for maintenance), the second regulator, which has a
slightly lower setpoint, takes over. The transition from LFG to
NatGas/Air, and from Blender 1 to Blender 2, is fully automatic and
un-noticeable at the paint shop.
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Click on the thumbnail
for a 43 kB PDF with a simplified P&ID for a twin-blender LFG system.
The system maintains the fuel gas supply pressure to the paint shop of
an automotive plant and can augment a supply deficit, or supply 100% of
the demand if LFG supply is interrupted. |
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Natural Gas Stabilization |
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Situation:
A manufacturing line for tempered glass (TV picture tubes) is
supplied by NatGas with fluctuating heating value (Calorific Value, CV).
The fluctuations are significant enough to upset the production results.
Solution:
Installation of a POM blender with Automatic Gas Properties Control
(AccuBlend™).
Operation:
The POM blender is supplied with NatGas and with Air. The POM is
pre-set to a blending ratio that results in slightly "diluted"
NatGas/Air mixture with a CV that is acceptable to the process. A
Calorimeter at the outlet of the POM measures the CV of the NatGas/Air
mixture.
If the Calorimeter
detects a deviation of the CV from the desired value, the AccuBlend™
controller automatically adjusts the position of the piston in the POM,
thereby changing the NatGas/Air blending ratio, and re-establishing the
desired CV.
Note:
If the CV of the NatGas as supplied to the plant is always higher
than the minimum acceptable CV, the POM blender would always "dilute"
the NatGas with Air.
If the CV of the NatGas
as supplied to the plant could fall below the minimum acceptable CV, the
POM blender can be switched to "Enrichment Mode". In this mode, the air
supply is turned off, and is replaced with a supply of BTU-rich gas, for
example LP vapor. As before, the NatGas and the LP vapor will be mixed
by the POM blender to achieve the desired CV. The Calorimeter will again
be used to provide a feedback signal to the AccuBlend™ controller to
make adjustments to the blending ratio if and when required.
The switch from
"Dilution" to "Enrichment" can be initiated manually
by the operator, or can be accomplished fully automatically (without operator
interaction). |
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Coke Oven Gas Replacement |
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Situation:
A steel mill operates their own coke plant. Coke Oven Gas (COG) is a
by-product of the Coke-making process and is used to fuel the process.
Occasionally, the Coke
batteries have to be shut down for maintenance and repairs. To start the
batteries back up again, COG is required. However, since the batteries
are
shut down, no COG is being generated.
Solution:
Installation of a POM blender with Automatic Gas Properties Control
(AccuBlend™).
Operation:
The POM blender is supplied with NatGas and with Air (or Nitrogen).
The POM is pre-set to a blending ratio that results in highly "diluted"
NatGas/Air mixture with a CV that resembles the properties of COG.
A Calorimeter at the outlet of the POM measures the CV of the NatGas/Air
or NatGas/Nitrogen mixture.
If the Calorimeter
detects a deviation of the CV from the desired value, the AccuBlend™
controller automatically adjusts the position of the piston in the POM,
thereby changing the blending ratio, and re-establishing the desired CV.
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Click on the thumbnail
for a 46 kB PDF with a simplified P&ID for a triple-blender COG system.
The system can be operated in "Sweetening-Only" mode, or in "Sweetening
plus Augmentation/Replacement" mode.
The system is sized for
1,800,000 scfh (810 MMBTU/h) and has three POM-80 blenders that are
staged to provide a system flow rate turndown of 1% to 100%. |
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Other Non-Standard Blending
Applications |
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The POM blenders can be used for the
blending of any two dissimilar gasses at (almost) any blending ratio. In
standard POM configurations, the gasses must be compatible with Carbon
Steel, Brass, Aluminum, and Buna N or Viton®.
For more corrosive applications, POM valve
and other components in the gas streams can be manufactured from
Stainless Steel or other corrosion-resistant materials.
Please
contact the factory with your
specific requirements. |
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