CHLORIDE SALT ELIMINATOR FOR GLYCOL IN NATURAL GAS DEHYDRATION

Abstract

A chloride salt eliminator system and method for removal of chloride salt from glycol circulated through a reboiler in natural gas dehydration, in a continuous process, close to the wellhead. Hot glycol from the reboiler is pumped into a salt eliminator unit having independently replaceable filter elements which trap chloride salts which are not soluble in hot glycol and pass clean glycol for return to the reboiler.

Claims

1. A chloride salt eliminator system for removal of chloride salt from glycol circulated through a reboiler in natural gas dehydration, the chloride salt eliminator system comprising: (i) a salt eliminator unit having a unit inlet and a unit outlet; (ii) a plurality of filter elements arrayed within said salt eliminator unit; (iii) a high-temperature pump having a pump motor, adapted to pump glycol from the reboiler, into said unit inlet, through said filter elements, and out of said unit outlet back into the reboiler; and (iv) a pump controller adapted to control operation of said high-temperature pump.

2. The chloride salt eliminator system of claim 1, further comprising a plurality of said filter elements adapted for independent installation and removal.

3. The chloride salt eliminator system of claim 1, further comprising said filter elements made of spun glass and having a stainless steel core.

4. The chloride salt eliminator system of claim 1, further comprising said filter elements having a diameter of about 36 inches.

5. The chloride salt eliminator system of claim 1, further comprising more than nine said filter elements.

6. The chloride salt eliminator system of claim 1, further comprising thirteen said filter elements.

7. The chloride salt eliminator system of claim 1, where said salt eliminator unit has a design temperature of 650° F. and a normal operating temperature of 395° F.

8. The chloride salt eliminator system of claim 1, where said high temperature pump has a capacity of 15 gpm at a 7 psig discharge pressure.

9. The chloride salt eliminator system of claim 1, where said pump motor is rated 1 hp and 1800 rpm.

10. The chloride salt eliminator system of claim 1, where said pump controller is further adapted to monitor and control pressure of a flow of the glycol into said salt eliminator unit, and to stop the flow of the glycol under set conditions.

11. The chloride salt eliminator system of claim 1, where said pump controller is further adapted to monitor, record, and report a volume of the glycol processed.

12. The chloride salt eliminator system of claim 1, further comprising a bypass outlet on said salt eliminator unit, a bypass valve adapted to return the glycol to the reboiler bypassing said filter elements, and a bypass controller adapted to control said bypass valve.

13. The chloride salt eliminator system of claim 1, further comprising mounting upon a skid.

14. The chloride salt eliminator system of claim 1, further comprising a remote unit, remote-unit communications link, pump-controller communications link, and bypass-controller communications link.

15. A chloride salt eliminator method comprising: (i) providing a chloride salt eliminator system comprising: (a) a salt eliminator unit having a unit inlet and a unit outlet; (b) a plurality of filter elements arrayed within said salt eliminator unit; (c) a high-temperature pump having a pump motor, adapted to pump glycol from the reboiler, into said unit inlet, through said filter elements, and out of said unit outlet back into the reboiler; and (d) a pump controller adapted to control operation of said high-temperature pump; (ii) transporting said chloride salt eliminator system to wellhead site; (iii) installing said chloride salt eliminator system at the wellhead site; (iv) connecting said chloride salt eliminator system to the glycol reboiler of the natural gas dehydration equipment at the wellhead site; (v) operating said chloride salt eliminator system in a substantially continuous process; (vi) changing said filter elements, independently, as needed; and (vii) removing chloride salts from the glycol circulated through the reboiler.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Reference is made to the drawing, showing a schematic view of the chloride salt eliminator of the invention in use.

DETAILED DESCRIPTION OF THE INVENTION

[0018] The chloride salt eliminator 10 system and method provides for removal of chloride salt from glycol circulated through a reboiler in natural gas dehydration, where a glycol such as triethylene glycol (TEG) is used to absorb water, salts, and other unwanted materials from natural gas, in a process usually performed close to the wellhead so that the cleaned natural gas can be transported by pipeline, and where a reboiler 20 is used to heat the previously used “wetted” glycol to an operating temperature of about 395° F./201° C. sufficient to drive out water and other extraneous materials so that the glycol can be reused for additional cycles of dehydration of natural gas. The heating in the reboiler also precipitates out the chloride salts formerly dissolved in the water, which is not soluble in the glycol at the operating temperature of the reboiler, and which therefore crystalizes and precipitates into deposits which are detrimental to the operation of the reboiler and therefore require elimination.

[0019] The chloride salt eliminator 10 provides a high-temperature pump 1, driven by a pump motor 2, and controlled by a pump controller 31. The high-temperature pump 1 draws glycol at operating temperature from the reboiler 20, and pumps the hot glycol to the unit inlet 3 of the salt eliminator unit 4. The salt eliminator unit 4 houses several filter elements 5. Each filter element 5 is made of spun glass and has a stainless steel core. The filter elements 5 are arrayed in a series such that the incoming hot glycol will pass through a first filter element 5 and then a second, and so on in series. The filter elements 5 trap chloride salt crystals while passing the glycol. The first filter element 5 will encounter and trap a larger number of crystals up to a point of saturation, after which the glycol will flow around the saturated filter element 5 and flow onto the next filter element 5, which will trap a larger number of crystals until saturation, with the cycle repeating. The filter elements 5 can be removed and replaced independently, allowing the chloride salt eliminator 10 to keep operating or to be paused only very briefly for filter replacement, therefore providing substantially continuous operation. Saturated filter elements 5 can be safely and appropriately discarded or can be cleaned and regenerated, either on site or off site. The provision of a greater number of filter elements provides for greater efficiency in trapping chloride salts and provides for longer operating time between filter maintenance, up to practical limits of size, weight, and complexity for equipment meant to be used in the field close to the wellhead. The filter elements are each of a size appropriate for handling during installation, removal, transport, and storage close to the wellhead. In a preferred embodiment each filter element 5 has a diameter of about 36″, the salt eliminator unit 4 houses 13 filter elements 5, and the salt eliminator unit 4 has about 69″ overall height and is made of stainless steel. The salt eliminator unit 4 should be able to withstand the high heat and high pressure of operation, plus an additional large margin to withstand increased heat and pressure to ensure safety and reliable operation of the equipment in the field close to the wellhead. In a preferred embodiment, the design temperature of the salt eliminator unit 4 is 650° F. with a normal operating temperature of 395° F. and maximum operating temperature of 400° F. In a preferred embodiment, the design pressure is 125 psig and the operating pressure is 25 psig.

[0020] In a preferred embodiment, the high-temperature pump 1 has a capacity of 15 gpm at a 7 psig discharge pressure, and the pump motor 2 is rated 1 hp, 1800 rpm.

[0021] The pump controller 31 controls the operation of the high-temperature pump 1 and monitors and controls the pressure of the flow of hot glycol into the salt eliminator unit 4. If the pump controller 31 senses an increase or decrease, matching set conditions, in back pressure in the salt eliminator unit 4, the pump controller 31 will stop the flow of hot glycol and will initiate an alarm protocol, which can include sounding an alarm and sending an alarm signal which can be sent to other parts of the chloride salt eliminator 10 system or to other parts of the overall gas-dehydration or wellhead-operation system. In an embodiment, the pump controller 31 can also monitor, record, and report the volume of hot glycol processed through the chloride salt eliminator 10 system, providing data useful for scheduling maintenance, inspections, and filter changes for the system, and for calculating volume-based billing if needed.

[0022] After passing through the filter elements 5 of the salt eliminator unit 4 the hot glycol, free of the chloride salts which have been trapped by the filter elements 5, passes through the unit outlet 6 and is returned to the reboiler 20 for eventual reuse in the natural gas dehydration process.

[0023] In an embodiment having an added bypass feature, hot glycol entering the unit inlet 3 of the salt eliminator unit 4 can be diverted to exit through the bypass outlet 7 and return to the reboiler 20 without passing through the filter elements 5. A bypass valve 8 controlled by a bypass controller 32 regulates the bypassing of hot glycol through the bypass outlet 7. The bypass valve 8 and bypass controller 32 can provide an additional measure of safety for operation of the salt eliminator unit 4 by monitoring for out-of-bounds pressure levels and diverting hot glycol back to the reboiler 20. Additionally, the bypass valve 8 and bypass controller 32 can provide for changing filter elements 5 or performing other work without completely shutting down the flow of glycol. The bypass controller 32 can also monitor, record, and report data regarding its operations.

[0024] In an embodiment especially suited for operation at or close to the wellhead, the components of the chloride salt eliminator 10 system are mounted on a skid, pallet, or platform, as indicated by the skid boundary 40, to facilitate storage, transport, placement, and operation.

[0025] In a remote-operation embodiment, a remote unit 51 is provided, having a remote-unit communications link 52, capable of communicating with a pump-controller communications link 53 and a bypass-controller communications link 54. The remote unit 51 can be implemented as a purpose-built unit or as a software application program for a general-purpose device such as a tablet computer or a smartphone. The communications links can be radio-frequency links such as proprietary links using appropriate frequencies, general-purpose links such as WIFI or BLUETOOTH, or can be cellular data links, where such service is available at the remote locations of drilling operations. The remote unit 51 provides for constant monitoring and reporting of the real-time operating status of the chloride salt eliminator 10 system, plus storage and reporting of additional data collected by the pump controller 31 and bypass controller 32.

[0026] Many other changes and modifications can be made in the system and method of the present invention without departing from the spirit thereof. I therefore pray that my rights to the present invention be limited only by the scope of the appended claims.