Gas Compression System

Abstract

A method and apparatus to reduce the intrusion of ambient air into an open-crankcase compressor. The method employs recycle control to reduce the magnitude of vacuum inside the compressor relative to ambient air pressure, and thereby eliminate the intrusion of said ambient air into said compressor.

Claims

1. A gas compression system comprising, a. an open-crankcase compressor, b. a recycle loop for allowing compressed gas from the outlet of said compressor, to return to the inlet of said compressor, and c. a means to control the flow of said compressed gas through said recycle loop, so as to substantially reduce the magnitude of a vacuum condition at the inlet of said compressor relative to the ambient air, and whereby substantially reduce the intrusion of said ambient air into said compressor.

2. The gas compression system of claim 1 which includes a pulsation dampener on the inlet of said compressor.

3. The gas compression system of claim 1 which includes a pulsation dampener on the outlet of said compressor.

4. The gas compression system of claim 1 which includes a heat exchanger on the outlet of said compressor.

5. The gas compression system of claim 1 in which the means to control the flow of gas through said recycle loop is a pressure regulator.

6. A method of reducing the intrusion of ambient air into an open-crankcase compressor comprising the use of recycle control in a manner effective to reduce or eliminate a vacuum condition at the inlet of said compressor relative to the ambient air.

7. A method for reducing the intrusion of ambient air into an open-crankcase compressor, comprising the steps of: a. measuring the gas pressure at the inlet of said compressor relative to the ambient air, b. recycling a portion of the compressed gas at the outlet of said compressor back to the inlet of said compressor and, c. controlling the flow rate of said recycled compressed gas so as to prevent a vacuum relative to said ambient air, at the inlet of said compressor, thereby preventing the intrusion said ambient air into said compressor.

Description

DRAWING FIGURES

[0020] FIG. 1 is a schematic drawing of the invention.

REFERENCE NUMERALS IN DRAWINGS

[0021] 10. Compressor [0022] 20. Low Pressure Pulsation Dampener [0023] 30. Pressure Regulator [0024] 40. High Pressure Pulsation Dampener [0025] 50. Heat Exchanger [0026] 60. Inlet Pressure Relief Valve

Description—FIG. 1

[0027] FIG. 1 shows a schematic diagram of the preferred embodiment this invention. The outlet of Compressor 10 is connected to a High Pressure Pulsation Dampener 40. High Pressure Pulsation Dampener 40 is connected to a Heat Exchanger 50. Heat Exchanger 50 is connected to a Pressure Regulator 30. Pressure Regulator 30 is connected to a Low Pressure Pulsation Dampener 20. Low Pressure Pulsation Dampener 20 is connected to the inlet of Compressor 10. Inlet Pressure Relief Valve 60 is connected to the inlet of Compressor 10.

[0028] Compressor 10 is an open-crankcase compressor.

[0029] Low Pressure Pulsation Dampener 20 is a volume bottle.

[0030] Pressure Regulator 30 is a pressure regulator.

[0031] Heat Exchanger 50 is heat exchanger.

[0032] High Pressure Pulsation Dampener 40 is a volume bottle.

[0033] Pressure Relief Valve 60 is a pressure relief valve.

Operation—FIG. 1

[0034] Compressor 10 is an open-crankcase oil-less reciprocating (piston) compressor. In operation, it receives gas at its inlet, and compresses it to a higher pressure at its outlet. Compressor 10, by its very nature, will generate pressure fluctuations at both its inlet and outlet. These pressure fluctuations correspond to the stroke of each piston.

[0035] High Pressure Pulsation Dampener 40 and Low Pressure Pulsation Dampener 20 are volume bottles used to dampen the pressure fluctuations created by Compressor 10. A volume bottle, is a pressure vessel usually three to ten times the swept volume of a compressor cylinder. The compressed gas in the volume bottle absorbs and dampens the pressure fluctuations generated by Compressor 10. Dampening the pressure fluctuations is necessary to prevent damage to, and allow proper function of, Pressure Regulator 30.

[0036] Pressure Regulator 30, is a common mechanical pressure regulator. Its function is to control pressure on the low pressure side of Compressor 10. When the Pressure Regulator 30 senses a pressure on the low pressure side of Compressor 10, that is below Pressure Regulator 30's setpoint, Pressure Regulator 30 opens its internal control valve and allows gas to flow from the high pressure side to the low pressure side of Compressor 10. When the pressure on the low side Compressor 10 rises back to Pressure Regulator 30's setpoint, the control valve inside Pressure Regulator 30 will begin to close. In this manner, Pressure Regulator 30 controls the pressure on the low pressure side of Compressor 10.

[0037] Heat Exchanger 50 is a finned tube heat exchanger. The temperature of the gas rises as it is compressed in the Compressor 1. Heat Exchanger 50 will transfer the excess heat from the compressed gas to the ambient air through its fins. This is necessary to prevent excessive heat buildup in the system.

[0038] Pressure Relief Valve 60 is a mechanical pressure relief valve. It monitors the gas pressure at the inlet to Compressor 10, and if the pressure exceeds the Pressure Relief Valve 60 setpoint, Pressure Relief Valve 60 will open and release the excess gas. Once the pressure at the inlet of Compressor 10 falls below the Pressure Relief Valve 60 setpoint, Pressure Relief Valve 60 will close.

[0039] The path from the outlet of Compressor 10, through High Pressure Pulsation Dampener 40, through Heat Exchanger 50, through Pressure Regulator 30, through Low Pressure Pulsation Dampener 20 and to the inlet of Compressor 10, forms a recycle loop. High pressure compressed gas from the outlet of the Compressor 10, is allowed to flow through this recycle loop, back to inlet of the Compressor 10. The gas flow in this recycle loop is controlled by Pressure Regulator 30. Pressure Regulator 30's pressure setpoint is set so as to prevent the pressure at the inlet of Compressor 10 from falling excessively below the pressure of the ambient air.

[0040] In summation, Compressor 10 compresses the gas. Heat Exchanger 50 removes excess heat from the compressed gas. Low Pressure Pulsation Dampener 20 and High Pressure Pulsation Dampener 40, protect Pressure Regulator 30 from pressure fluctuations generated by Compressor 10. Pressure Regulator 30 controls the gas flow through the recycle loop to prevent excessively low pressure at the inlet to Compressor 1. Pressure Relief Valve 6 protects the Compressor 1 from excessively high inlet pressure.

[0041] Another embodiment of this invention omits Pressure Relief Valve 60. If the source gas is of insufficient flow rate to exceed the capacity of Compressor 10, Pressure Relief Valve 60 may not be necessary. Additionally, some commercially available designs of Pressure Regulator 30, may include some pressure relief capability.

[0042] Another embodiment of this invention may omit either, High Pressure Pulsation Dampener 40, Low Pressure Pulsation Dampener 20, or both. In some cases, the function of a pulsation dampener may be accomplished by using a length of pipe or flexible tubing of sufficient volume to effectively dampen the pressure spikes created by Compressor 10. This could eliminate the need for a discreet pulsation dampener.

[0043] Another embodiment of this invention may use a pulsation dampener design other than a volume bottle, for High Pressure Pulsation Dampener 40 and Low Pressure Pulsation Dampener 20. There are many pulsation dampener designs that are commercially available.

[0044] Another embodiment of this invention may omit Heat Exchanger 50. Compressor 10, High Pressure Pulsation Dampener 40, Low Pressure Pulsation Dampener 20 and the piping or tubing associated with recycle loop, all have some heat exchange capacity which may be sufficient to mitigate excessive heat buildup.

[0045] Another embodiment of this invention might replace the finned tube Heat Exchanger 50, with another type heat exchanger. There are many heat exchanger designs that are commercially available.

[0046] Another embodiment of this invention may replace Pressure Regulator 30, with another device that accomplishes the same function. There are many commercially available options, a combination of a discreet pressure sensor, discreet control valve, and programmable logic controller (PLC) is one example.

[0047] Additional embodiments can be assembled using any number of combinations of these alternative embodiments.

Theory of Operation:

[0048] The intrusion of ambient air into the Compressor 10 requires both of two conditions: first, a path for the ambient air to flow through and second, a pressure differential of sufficient magnitude to push the ambient air through this path into Compressor 10.

[0049] Compressor 10 piston seals inevitably wear and begin to leak, providing a path for the ambient air to flow, and thereby satisfying the first necessary condition for the intrusion of ambient air into Compressor 10.

[0050] The method of this invention greatly reduces the development of the second necessary condition, a pressure differential of sufficient magnitude (a vacuum condition) to push the ambient air past the worn seals, into the Compressor 10.

[0051] When Pressure Regulator 30 senses a vacuum condition at the inlet of Compressor 10, relative to the ambient air pressure, Pressure Regulator 30 allows a portion of the compressed gas from the outlet of Compressor 10 to flow back to the inlet of Compressor 10. This ‘recycled’ compressed gas reduces the vacuum relative to the ambient air pressure, at the inlet of Compressor 10, and hence prevents the intrusion of ambient air into Compressor 10.

[0052] Recycling compressed gas from the outlet of a compressor back to the inlet is often referred to as ‘recycle’ capacity control. Reciprocating compressors do not respond well to ‘choke’ flow control. Simply restricting flow to a reciprocating compressor can cause excessive pressures and temperatures. Recycle capacity control allows the compressor to operate in harmony with upstream and downstream process demands while avoiding these extremes. This invention is a new use for recycle control. The intent is not to alter capacity, but to prevent the intrusion of ambient air, by preventing the formation of a vacuum condition inside an open-crankcase compressor.

CONCLUSION, RAMIFICATION AND SCOPE OF INVENTION

[0053] Thus the reader will see that the gas compression system of this invention provides a highly reliable and economical device that can deliver compressed gas free from contamination with ambient air.

[0054] While the above description contains many specificities, these should not be construed as limitations on the scope of the invention, but rather as an exemplification of one preferred embodiment. Many other variations are possible. Any compressed gas application, industrial or medical, that is sensitive to contamination by ambient air would benefit from this invention. Nitrogen, argon, fuel gases, and carbon dioxide are examples gasses that are commonly used applications that are sensitive to contamination with ambient air. Accordingly, the scope of the invention should be determined not by the embodiment(s) illustrated, but by the appended claims and their legal equivalents.