TRANSPORT CONTAINER WITH GAS SELECTIVE MEMBRANE EXHAUST

Abstract

Described herein is a method for operating a refrigerated stripping container containing respiring produce, the method including: passing a cooled CO.sub.2-rich air stream from an internal environment within the shipping container through a CO.sub.2 selective membrane of a membrane system to produce a cooled CO.sub.2-lean air stream and a CO.sub.2-rich permeate stream; retaining or returning the cooled CO.sub.2-lean air stream to the internal environment; and exhausting the CO.sub.2-rich permeate stream to an external environment outside of the shipping container: drawing external air or permitting external air to pass into the shipping container through an air vent with a pre-set fixed opening of the shipping container in a volume to at least balance a volume difference between the cooled CO.sub.2-rich air stream and the cooled CO.sub.2-lean air stream; wherein the membrane system is operated according to a pre-set mode, and the pre-set mode is independent of a measured gas concentration or pressure of the internal environment; and the pre-set fixed opening of the vent is selected based on one or more characteristics of the respiring produce and the pre-set mode of the membrane system.

Claims

1. A method for operating a refrigerated shipping container or other cooled enclosure containing respiring produce, the method including: passing a cooled CO.sub.2-rich air stream from an internal environment within the enclosure through a CO.sub.2 selective membrane of a membrane system to produce a cooled CO.sub.2-lean air stream and a CO.sub.2-rich permeate stream; retaining or returning the cooled CO.sub.2-lean air stream to the internal environment; exhausting the CO.sub.2-rich permeate stream to an external environment outside of the enclosure; and drawing external air or permitting external air to pass into the enclosure through an air vent with a pre-set fixed opening of the enclosure in a volume to at least balance a volume difference between the cooled CO.sub.2-rich air stream and the cooled CO.sub.2-lean air stream; wherein the membrane system is operated according to a pre-set mode, and the pre-set mode is independent of a measured gas concentration or pressure of the internal environment; and the pre-set fixed opening of the vent is selected based on one or more characteristics of the respiring produce and the pre-set mode of the membrane system.

2. The method of claim 1, wherein the vent is operated independently of a controller or control system.

3. The method of claim 1, wherein the pre-set mode is not adjusted, altered, or controlled in response to any measured variable of the internal environment.

4. The method of claim 1, wherein the method further includes initially selecting the pre-set mode according to one or more characteristics of the respiring produce.

5. The method of claim 1, wherein the pre-set mode is selected from the group consisting of: a pre-set constant gas throughput, a pre-set variable gas throughput, a pre-set constant electrical load, a pre-set variable electrical load, a pre-set constant pressure differential between an inlet and an outlet of the membrane system, a pre-set variable pressure differential between an inlet and an outlet of the membrane system, a pre-set constant pump speed on a pump associated with the retentate side of the membrane, or a pre-set variable pump speed on a pump associated with a retentate side of the membrane.

6. The method of claim 1, wherein the pre-set mode is additionally independent of one or more characteristics of the respiring produce.

7. The method of claim 6, wherein the pre-set mode is a fixed mode of operation.

8. The method of claim 7, wherein the pre-set mode is not adjusted, altered, or controlled.

9. The method of claim 8, wherein the fixed mode of operation is selected from: a pre-set constant gas throughput, a pre-set constant electrical load, a pre-set constant pressure differential between an inlet and an outlet of the membrane system, a pre-set constant pump speed on a pump associated with the retentate side of the membrane.

10. The method of claim 1, wherein the membrane system is operated independently of a controller or control system.

11. The method of claim 1, wherein the cooled enclosure is not operated under controlled atmosphere conditions.

12. A refrigerated shipping container or other cooled enclosure for containing respiring produce, including a control system programmed to carry out the following: pass a cooled CO.sub.2-rich air stream from an internal environment within the enclosure through a CO.sub.2 selective membrane of a membrane system to produce a cooled CO.sub.2-lean air stream and a CO.sub.2-rich permeate stream; retain or return the cooled CO.sub.2-lean air stream to the internal environment; and exhaust the CO.sub.2-rich permeate stream to an external environment outside of the enclosure; the control system further programmed to draw external air or permit external air to pass into the enclosure through an air vent with a pre-set fixed opening of the enclosure in a volume to at least balance a volume difference between the cooled CO.sub.2-rich air stream and the cooled CO.sub.2-lean air stream; wherein the control system operates the membrane system according to a pre-set mode, the pre-set mode being independent of a measured gas concentration or pressure of the internal environment; and wherein the pre-set fixed opening of the vent is selected based on one or more characteristics of the respiring produce and the pre-set mode of the membrane system.

13. A refrigerated shipping container or other cooled enclosure configured to transport or store respiring produce, including: a membrane system including: a gas inlet open to an internal environment within the enclosure; a first gas outlet open to the internal environment within the enclosure; a second gas outlet open to an external environment outside the enclosure; a CO.sub.2 selective membrane configured to: receive a cooled CO.sub.2-rich air stream from the internal environment via the gas inlet, and to separate at least a portion of CO.sub.2 from the cooled CO.sub.2-rich air stream to form a cooled CO.sub.2-lean air stream on a first side of the CO.sub.2 selective membrane and a CO.sub.2-rich permeate stream on a second side of the CO.sub.2 selective membrane, and discharge the cooled CO.sub.2-lean air stream through the first gas outlet and the CO.sub.2-rich permeate stream through the second gas outlet, and gas circulation apparatus configured to pass the cooled CO.sub.2-rich air from the internal environment through the CO.sub.2 selective membrane; wherein the membrane system is configured to be operated according to a pre-set mode, and the pre-set mode is independent of a measured gas concentration or pressure of the internal environment; and wherein the enclosure includes an air vent with an opening, the air vent configured to be opened to a selected pre-set fixed opening based on one or more characteristics of the respiring produce and the pre-set mode of the membrane system.

14. The enclosure of claim 13, wherein the pre-set mode is operated independently of a controller or control system.

15. The enclosure of claim 13, wherein the pre-set mode is independent of any measured variables of the internal environment.

16. The enclosure of claim 13, wherein the vent is operated independently of a controller or control system.

17. The enclosure of claim 13, wherein the enclosure does not include a controlled atmosphere control system.

18. A CO.sub.2 selective gas membrane module when used in a refrigerated shipping container or other cooled enclosure that does not include a controlled atmosphere control system, the membrane module including: a mount for installing the membrane module into the enclosure; a gas inlet configured to be open to an internal environment within the enclosure; a first gas outlet configured to be open to the internal environment within the enclosure; a second gas outlet configured to be open to an external environment outside the enclosure; a CO.sub.2 selective membrane configured to: receive a cooled CO.sub.2-rich air stream from the internal environment via the gas inlet, and to separate at least a portion of CO.sub.2 from the cooled CO.sub.2-rich air stream to form a cooled CO.sub.2-lean air stream on a first side of the CO.sub.2 selective membrane and a CO.sub.2-rich permeate stream on a second side of the CO.sub.2 selective membrane, and discharge the cooled CO.sub.2-lean air stream through the first gas outlet and the CO.sub.2-rich permeate stream through the second gas outlet; and gas circulation apparatus configured to pass the cooled CO.sub.2-rich air from the internal environment through the CO.sub.2 selective membrane; wherein the membrane system is configured to be operated according to a pre-set mode and the pre-set mode is independent of a measured gas concentration or pressure of an internal environment of the enclosure.

19. A method of installing a membrane module according to claim 18 in a refrigerated shipping container or other cooled enclosure that does not include a controlled atmosphere control system.

20. A method of modifying a controlled atmosphere refrigerated shipping container or other controlled atmosphere cooled enclosure to provide a cooled enclosure according to claim 12, the method including removing the controlled atmosphere control system from the enclosure.

21. A method for reducing refrigeration energy requirements in operation of a refrigerated shipping container or other cooled enclosure containing respiring produce, the method including: a membrane exhaust activity involving drawing and/or driving air from the interior of the enclosure through a CO.sub.2 selective membrane of a membrane system installed in the enclosure, and exhausting the resulting CO.sub.2-rich downstream air stream to the exterior of the enclosure; and an atmosphere replenishment activity involving causing or permitting ambient air from the exterior of the enclosure to pass into the enclosure to balance the volume of air lost through the membrane; wherein the method is conducted in the absence of controlled atmosphere operation, such that neither the membrane exhaust activity nor the atmosphere replenishment activity is conducted in accordance with the monitoring of a gas concentration or pressure in the interior of the enclosure.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0092] FIG. 1 is a photograph of a refrigeration panel of a refrigerated shipping container.

[0093] FIG. 2 is a schematic of a membrane separation system for installation into a refrigerated shipping container.

[0094] FIG. 3 is a schematic illustrating one embodiment of the membrane separation system.

[0095] FIG. 4 is a graph showing modelled results of equilibrium CO.sub.2 concentration within a shipping container as a function of membrane surface area for bananas and avocados for different respiration rates.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0096] The invention relates to a method and/or apparatus for storing and/or transporting respiring produce in an unsealed refrigerated shipping container or other cooled enclosure without an actively controlled atmosphere. Respiring produce produces CO.sub.2 which needs to be removed from the internal environment of the refrigerated shipping container to preserve the freshness of the respiring produce. Such respiring produce typically includes fruit, vegetables, plants, seedlings, plant materials, and the like.

[0097] It will be appreciated that the methodology and system is applied without a controlled atmosphere regime. A controlled atmosphere regime is associated with a substantially sealed reefer, and is one in which one or more conditions of the internal atmosphere are monitored, and operation of the membrane system is controlled (such as via a controller or control system) to maintain the one or more monitored conditions