Composite Gas Sampling System

Abstract

A sampling system for collecting periodic composite and/or non-composite samples of vaporized gas during a transfer process from a vaporizer of a cryogenic hydrocarbon liquid including 1) a direct sample pathway to a gas analyzer for instantaneous, real-time vaporized gas analysis, 2) a speed loop pathway for directly collecting fresh vaporized gas samples for subsequent analysis, and 3) a composite sample pathway including a pressurized sample accumulator for collecting a plurality periodically obtained samples of a select volume during the transfer process to create a composite sample of the vaporized gas.

Claims

1. An apparatus for capturing a periodic gas sample following vaporizing and conditioning into a gas phase of a cryogenic liquid hydrocarbon source during transfer processing, comprising: at least a first and a second vaporized sample input lines each incorporating at least a first direct feed line, a second speed loop line, and a third accumulator feed line; each of the first direct feed lines of the first and second vaporized sample input lines being directly connected to a gas analyzer for on-line, real-time, periodic analysis of a non-composite gas sample; each of the speed loop lines being connected to a speed loop having an a pressure regulator, a high pressure pump, a plurality of solenoid controlled valves for controlled filling of a plurality of non-composite sample cylinders for storage of fresh gas samples obtained at specified processing intervals, and a by-pass outlet to a boil-off-gas system; each of the accumulator lines including at least one solenoid controlled valve, said accumulator line for passing a gas sample of a select volume at select time intervals to a pressure regulator, a solenoid controlled valve, and a gas accumulator for receiving multiple periodic select volume gas samples to create a composite gas sample, and a high pressure pump to maintain pressure sufficient in the gas accumulator to prevent dew point drop-out of the gas sample, a valve controlled outlet from the gas accumulator, and a plurality of sample grab cylinders for receiving composite samples from the gas accumulator upon completion of source processing.

2. The apparatus of claim 1 further comprising a control unit for controlling the solenoid valves, flow operations, speed loop fresh non-composite sample collection timing, and accumulator composite gas sample retention.

3. The apparatus of claim 1 comprising a third vaporized gas sample input line and a second, duplicate accumulator line connected to a said gas accumulator for simultaneous sampling from multiple inputs from the source.

4. The apparatus of claim 3 comprising a residual gas removal system following completion of processing sampling operations.

5. The apparatus of claim 4 where the residual gas removal system is a gas purge system and where the Boil-off-gas system comprises a boil-off gas header.

6. The apparatus of claim 4 where the residual gas removal system includes an evacuation method.

7. The apparatus of claim 2 further comprising a housing cabinet including a heater and over pressure vent.

14. The apparatus of claim 13 where there are four removable, receiving composite sample grab cylinders.

15. A system for selected sampling cryogenic liquid hydrocarbon source where the liquid hydrocarbon has been vaporized and conditioned by a vaporizer during transfer processing, comprising: a housing; a controller for controlling the gas sampling operation contained within the housing; a vaporized gas port providing a first, a second and a third gas stream feed lines adapted to receive a vaporized gas sample of a select volume at a select time; a gas analyzer connected to said first gas stream feed line; a speed loop connected to said second feed line; a plurality of removable, sample cylinders connected to the speed loop for collection of non-composite fresh samples at select times directly from the vaporizer; an accumulator connected to said third gas stream for receiving a select volume of gas to create a composite sample of vaporized gas; at least one pump associated with said accumulator to build accumulator pressure at a level to prevent dew point drop out of the vaporized gas; a plurality of removable sample grab cylinders for receiving composite vaporized gas samples from the accumulator; a residual gas removal array for removing residual gas as from the system following transfer processing of the cryogenic liquid hydrocarbon.

8. The apparatus of claim 7 further comprising a separate analyzer cabinet connected to or within said housing cabinet defining a housing cabinet for housing at least one gas analyzer.

9. The apparatus of claim 8 where, said analyzer is a gas chromatograph, and further includes a heater in the analyzer cabinet and a calibration gas station.

10. The apparatus of claim 1 further comprising at least one flow controller disposed in said speed loop line and a second flow controller disposed in said accumulator line for diverting the gas sample to said speed loop line.

11. The apparatus of claim 10 further comprising at least a first second and third check valves to prevent backflow respectively between said high pressure pump and gas accumulator, said accumulator line and said speed loop line, and said sample grab cylinders and said boil-off gas system.

12. The apparatus of claim 11 further comprising a control unit for controlling the solenoid valves, flow operations, and sample introduction into said accumulator.

13. The apparatus of claim 12 where there are three non-composite sample cylinders for storage of fresh non-composite samples obtained at , and of the elapsed processing intervals.

16. The system of claim 15 further comprising a redundant vaporized gas port connected to the accumulator.

17. A method for sampling of vaporized gas from a cryogenic liquid hydrocarbon liquid using a gas sample system, comprising the steps of: obtaining a first vaporized gas sample of selected volume and at first select intervals from a vaporizer connected to a cryogenic liquid hydrocarbon repository; passing a select volume of said first vaporized gas sample to a first sample grab cylinder; pumping a second select volume of said vaporized first gas sample to a composite sample accumulator tank under pressure sufficient to prevent dew point dropout; obtaining a second gas sample of selected volume at select interval different from the first select interval; passing a first select volume of said vaporized second gas sample to a second sample grab cylinder; pumping a second select volume of said vaporized second gas sample to the composite sample accumulator tank under pressure sufficient to prevent dew point dropout to obtain a composite gas sample; passing the composite gas sample to a select one of a plurality of removable composite sample collection cylinders for receiving said composite vaporized sample from the accumulator tank; removing the select one of the composite sample cylinders; and removing at least said first sample grab cylinder.

18. The method of claim 17 further comprising the step of removing residual gas from the gas sample system after removing the composite sample cylinder and the sample grab cylinder.

19. The method of claim 17 further comprising the step of purging residual gas in the gas sample system after removing the composite sample cylinder and the sample grab cylinder,

20. The method of claim 17 further comprising the step of analyzing the content of the removed composite sample cylinder and said sample grab cylinder.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] FIG. 1 is a photographic depiction of a composite sample system in accordance with an embodiment of the invention.

[0023] FIG. 2 is a schematic diagram of the embodiment of FIG. 1.

[0024] FIG. 3 is a schematic diagram of a multi-stream, multi-sample collection embodiment of the invention.

[0025] FIG. 4 is a schematic diagram of an embodiment of the invention that with a bladderless accumulator and a vacuum unit for removing residual gas from the system upon completion of a transfer process.

DETAILED DESCRIPTION OF THE DRAWINGS

[0026] The embodiment illustrated in FIG. 1 includes the composite sample system 10 contained in housing 11. The system 10 provides a representative gas composition sample by taking small bite size samples over a period of time. The system 10 includes a programmed logic controller (PLC) 12 with a connection to a remote communication facility for controlling the valves and solenoids and indicator lights for system operation as well as monitoring system status. In addition to the controller 12, the housing 11 of sampling system 10 contains sample pumps 14, a plurality of removable accumulator grab sample cylinders 16 (four cylinders are used in the illustrated system), a plurality of fresh sample cylinders 18 each for receiving a respective gas sample at a specific interval (e.g., load transfer, load transfer, and load transfer) during the transfer processing. The grab cylinders 16 are connected to accumulator 20 through appropriate tubing for communication the composite sample. The accumulator 20 which receives a multiplicity of samples of a specified small volume, e.g., 0.5 cc, at a preset time interval (i.e., 1 sec.) under conditions (pressure and temperature) maintained to prevent dew point dropout. Similarly when feeding the composite gas from the sample accumulator 20 to the respective grab sample cylinders, the associated pump(s) must maintain the pressure of the gas to prevent dew point drop out. For maintenance of system stability, the interior of cabinet 11 includes the electrical housing heater 22 to maintained temperatures at an elevated level.

[0027] In operation, the composite sample system according to the invention grabs a fresh, 0.5 cc, sample every second, storing it in the accumulator 20 for transfer to the associated grab cylinders 16 following the conclusion of the transfer operation. The composite sample can then be removed and transferred to a laboratory or analyzer site for subsequent analysis.

[0028] The invention contemplates residual sampled gas removal at the conclusion offloading or transfer processing to reset the system for the next processing operation. FIG. 2 illustrates a gas purge subsystem based on nitrogen gas fed into the system from the tank 24. The purging operation can be completely automated or may be semi-manual (the nitrogen regulator is opened manually when the PLC has been instructed to open the system valves for purging.

[0029] Turing to the embodiment illustrated in FIG. 3, it illustrates a multipath, multi-vaporizer takeoff system for multiple simultaneous inputs. This embodiment also provides speed loops 24 that provide alternative feed lines for the vaporized gas directly from the vaporizer to one or more select collection cylinders and/or overflow from the gas pumps 14 associated with the accumulator 20. The particular arrangement provides the system user with the greatest flexibility by allowing for either collection cylinder set to be used for non-composite sampling as well as providing venting to line feed 28 for a BOG (boil-off-gas) collector/header system.

[0030] Another option for resetting the system is illustrated in FIG. 4 where a vacuum generating unit 26 is disposed in line with the system and activated by the PLC 12 has all valves opened, to create a negative system pressure and move the residual gas to an appropriate outlet such as a BOG header 28 or using the above-mentioned positive pressure purging gas, e.g., Helium, from the tank 23 to push the residual gas to a vent or the like. Once removed, the system has been effectively reset and is ready for the next sampling operation.

[0031] The invention has been disclosed in the forgoing specification. It is understood by those skilled in the art that many modifications and embodiments of the invention will come to mind to which the invention pertains, having benefit of the teaching presented in the foregoing description and associated drawings. It is therefore understood that the invention is not limited to the specific embodiments disclosed herein, and that many modifications and other embodiments of the invention are intended to be included within the scope of the invention. Moreover, although specific terms are employed herein, they are used only in generic and descriptive sense, and not for the purposes of limiting the description invention.