Controlled atmosphere sea van container including carbon dioxide scrubber curtain

Abstract

A scrubber configuration for controlling carbon dioxide levels in a shipping container containing respiring produce is disclosed. The scrubber is made up of a curtain which includes a gas-selective membrane having a CO 2 /O 2 selectivity ratio greater than 1:1, said curtain being positioned close to and parallel with the rear wall of said container which includes a door, said curtain forming an air-tight seal dividing the interior of the container into a plenum chamber between said membrane and the (rear wall) door, and the remainder of the container in which the produce is placed. The structure also includes an air intake means for conveying fresh air from outside the container into the plenum chamber; and an air output means for conveying air from the plenum chamber to the outside of the container. A method for controlling the carbon dioxide levels inside a shipping container is also disclosed.

What is claimed is: 
     
         1 . A container for shipping and/or storing respiring produce, said container formed by four side walls, a ceiling and a floor, one of said side walls including a door through which said produce is put in and/or taken out of said container, comprising a curtain which includes a gas-selective membrane having a CO 2 /O 2  selectivity ratio greater than 1:1, said curtain positioned close to said door and forming an air-tight seal dividing the interior of the container into a plenum chamber between said membrane and the door, and the remainder of the container in which the produce is placed; an air intake means for conveying fresh air from outside the container into the plenum chamber; and an air output means for conveying air from the plenum chamber to the outside of the container. 
     
     
         2 . The container of  claim 1  which additionally comprises a controller and one or more sensors to control the flow of air into and out of the plenum chamber. 
     
     
         3 . The container of  claim 2  wherein the sensors measure the carbon dioxide level in the produce storage area and the flow of air into and out of the plenum chamber is controlled based on that measurement. 
     
     
         4 . The container of  claim 1  wherein the gas-selective membrane has a CO 2 /O 2  selectivity ratio greater than about 2:1. 
     
     
         5 . The container of  claim 1  wherein the air intake and output means are connected to the outside atmosphere using drainage openings existing in the container. 
     
     
         6 . The container of  claim 5  wherein the existing openings are located in the produce storage area of the container and the air input and output means pass through the curtain into the plenum area. 
     
     
         7 . The container of  claim 6  wherein the seals which surround the air input and air output means at the joint where they pass through the curtain is airtight. 
     
     
         8 . The container of  claim 1  which additionally comprises one or more fans to assist flow of air in the air input and output means. 
     
     
         9 . The container of  claim 1  wherein the curtain is positioned from about 2 inches to about 2 feet away from said door. 
     
     
         10 . The container of  claim 1  wherein the gas-selective membrane has a one-side surface area of from about 3,000 to about 12,000 square inches. 
     
     
         11 . The container of  claim 1  which additionally comprises a stiffener attached to said curtain or membrane to maintain the shape of said membrane. 
     
     
         12 . A method for controlling the carbon dioxide levels inside a shipping container containing respiring produce, said container formed by four side walls, a ceiling and a floor, one of said side walls including a door through which said produce is put in and/or taken out of said container, said container comprising a curtain which includes a gas-selective membrane having a CO 2 /O 2  selectivity ratio greater than 1:1, said curtain positioned close to said door and forming an air-tight seal dividing the interior of the container into a plenum chamber between said membrane and the door, and the remainder of the container in which the produce is placed; an air intake means for conveying fresh air from outside the chamber into the plenum chamber; and an air output means for conveying air from the plenum chamber to the outside of the container; said method comprising circulating fresh air into the plenum chamber, preferably when the carbon dioxide level in the produce storage area reaches a defined level. 
     
     
         13 . The method of  claim 12  wherein the fresh air is circulated into the plenum chamber when the carbon dioxide level in the produce storage area reaches a pre-defined level. 
     
     
         14 . The method of  claim 13  which utilizes a controller and one or more sensors to measure the carbon dioxide level in the produce storage area and control the flow of air into and out of the plenum based on those measurements. 
     
     
         15 . The method of  claim 12  wherein the air intake and output means are connected to the outside atmosphere using drainage openings existing in the container. 
     
     
         16 . The method of  claim 15  wherein the existing openings are located in the produce storage area of the container and the air input and output means pass through the curtain/membrane into the plenum area. 
     
     
         17 . The method of  claim 16  wherein the seals which surround the air input and air output means at the point where they pass through the curtain/membrane is airtight. 
     
     
         18 . The method of  claim 12  wherein the gas-selective membrane has a CO 2 /O 2  selectivity ratio greater than about  2 : 1 . 
     
     
         19 . The method of  claim 12  wherein the container additionally comprises one or more fans to assist flow of air in the air input and output means. 
     
     
         20 . The method of  claim 12  wherein, in the container, the curtain is positioned from about 2 inches to about 2 feet away from said door. 
     
     
         21 . The method of  claim 12  wherein, in the container, the gas-selective membrane has a one-side surface area of from about 3,000 to about 12,000 square inches. 
     
     
         22 . The method of  claim 12  wherein, in the container, the curtain additionally comprises a stiffener to maintain the shape of said curtain. 
     
     
         23 . A curtain for use as a carbon dioxide scrubber in a container for shipping and/or storing respiring produce, comprising a flexible material attached to and surrounding a gas-selective membrane having a CO 2 /O 2  selectivity ratio greater than 1:1, the curtain being of such size that it can be sealed to the side walls, the ceiling and the floor of said container so as to form an air-tight seal. 
     
     
         24 . The curtain according to  claim 23  wherein the gas-selective membrane has a CO 2 /O 2  selectivity ratio greater than about 2:1. 
     
     
         25 . The curtain according to  claim 23  wherein the gas-selective membrane has a one-side surface area of from about 3,000 to about 12,000 square inches. 
     
     
         26 . The curtain according to  claim 23  made from a flexible vinyl material. 
     
     
         27 . The curtain according to  claim 23  which additionally comprises one or more stiffening means attached to said flexible material to maintain complete or partial rigidity of the curtain.