Carbon dioxide scrubber for fuel and gas emissions

Details Carbon dioxide scrubber for fuel and gas emissions Carbon dioxide scrubber for fuel and gas emissions

2002-01-16

2004-06-29

Smith, Duane S. (Department: 1724)

Gas separation: processes

With control responsive to sensed condition

Concentration sensed

C095S097000, C095S139000, C096S111000, C096S130000, C096S126000

Reexamination Certificate

active

06755892

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to a system for minimizing carbon dioxide emissions from a stationary source, and specifically for minimizing carbon dioxide emissions emanating from burning fossil fuels or extracting natural gas.
There is currently a great interest in reducing emissions of carbon dioxide (CO
2
) gases into the atmosphere. The amount of CO
2
gas emitted into the air is cited as a factor contributing to global warming. CO
2
gas is emitted whenever fossil fuels are burned, such as in automobile engines and coal burning furnaces used by power plants for the generation of power. Reductions in the amount of CO
2
gases emitted by such processes is of increased importance and is a point of specific emphasis for government regulatory agencies. This is especially so for power plants burning large volumes of fossil fuels, emitting large quantities of CO
2
into the atmosphere.
Currently systems for controlling and eliminating the CO
2
from a breathable air supply are utilized in submarines, space vehicles and space suits. These systems utilize a CO
2
sorbent bed composed of a plurality of amine sorbent beads disposed within a container. A stream of air containing CO
2
is flowed through the container and the amine sorbent beads. The CO
2
contacting the amine sorbent beads reacts therewith to become trapped within the container. The remainder of the breathable air recirculates into the controlled environment. Once the container has become saturated with CO
2
such that further absorption of CO
2
is inefficient, the breathable air stream is switched to a second container. The saturated container is then exposed to heat or reduced pressure to evolve or release the trapped CO
2
for disposal or use in other systems. Such systems have proven effective and efficient for controlling CO
2
content within enclosed environments, however this technology has not been applied to environments such as those encountered in the operation of a power plant or the extraction of natural gas.
It is therefore desirable to employ technology associated with controlling CO
2
in enclosed environments to control exhaust emissions associated with burning of fossil fuels and extraction of natural gas.
SUMMARY OF THE INVENTION
A disclosed embodiment of this invention is a system and method for controlling carbon dioxide (CO
2
) emissions emanating from a gas source using sorbent beds containing a regenerable sorbent.
The system controls CO
2
emissions formed from the burning of coal or natural gas by absorbing CO
2
from a gas stream. The system is installed such that exhaust gases are communicated through a CO
2
sorbent bed before being released into the atmosphere. The CO
2
sorbent bed traps CO
2
contained within the exhaust gas such that the now CO
2
minimized gas is finally exhausted to the atmosphere. Another embodiment of this invention is installed to control CO
2
content within natural gas extracted from a well. The gas extracted from the natural gas well is routed through the CO
2
sorbent beds of this invention to control the amount of CO
2
contained within the final product.
The system includes at least two sorbent beds with one operably associated with the exhaust gas stream. The particular sorbent bed communicates with the exhaust gas stream by way of an inlet conduit and inlet valve. The inlet valve directs the exhaust gas stream through the sorbent bed such that CO
2
is absorbed and trapped. The outlet valves direct gas out of the sorbent bed. While one sorbent bed absorbs CO
2
, another sorbent bed is being regenerated to release trapped CO
2
into a storage container for disposal or use in other processes.
Applying heat above a predetermined temperature to release trapped CO
2
regenerates the sorbent bed. A vacuum source is in operable communication with the regenerating CO
2
sorbent bed to draw the released CO
2
out of the sorbent bed. Alternatively, a steam source is introduced through a steam inlet valve to heat the sorbent bed and release CO
2
. Steam heats the sorbent bed above the predetermined temperature to cause the release of CO
2
from the sorbent bed and concurrently drive the CO
2
out through the outlet valve.
A controller governs actuation of the heat source and of the vacuum source. The controller is also in communication with the inlet valve and the outlet valve to switch which sorbent bed, the gas stream flows. The controller alternates flow of the gas stream between the sorbent beds, such that one of the sorbent beds is always regenerating, while another sorbent bed is in communication with the gas stream.
A cooler is in operable communication with the sorbent bed that is currently in communication with the gas stream to regulate temperatures within the sorbent bed. Absorption of CO
2
generates a great deal of heat, and the sorbent bed works most efficiently at cooler temperatures. The cooler is actuated in response to signals from the controller to maintain a desired optimal temperature for the sorbent bed.
The sorbent beds include a regenerable CO
2
sorbent. Regenerable CO
2
sorbents are capable of repeatedly trapping and releasing CO
2
for many cycles and are therefore desirable for CO
2
removal applications including exhaust gases exhausted from a smoke stack. Preferably, the sorbent is an amine sorbent applied to a support structure to form a plurality of amine sorbent beads. The amine sorbent beads are packed into each sorbent bed to contact the gas steam.
In operation, the controller of the system actuates the inlet and outlet valves to direct the gas stream through at least one of the sorbent beds. The sorbent disposed within the sorbent bed forms a loose molecular bond with the CO
2
to trap the CO
2
within the sorbent bed. The remaining gas is directed out of the sorbent bed either to a storage tank or through a smokestack. The controller actuates the cooler to govern the temperature of the sorbent bed in contact with the gas stream to maintain an optimal temperature.
The CO
2
sorbent bed is placed within the gas stream, for a predetermined duration calculated to optimize CO
2
absorption. The controller will then actuate the inlet and outlet valves to divert the gas steam to another sorbent bed. The CO
2
saturated sorbent bed is then regenerated in preparation for another absorption cycle.
The system and method of this invention employs technology for controlling CO
2
in enclosed environments to control exhaust emissions associated with burning of fossil fuels and with natural gas production.


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European Search Report completed May 12, 2003.

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