Divided pressure vessel apparatus for carbon dioxide based systems and methods of using same

A dry cleaning method comprising the steps of:

• transferring a first densified gas based dry-cleaning solution from a first liquid chamber of a divided working tank to a wash tank containing a dry-cleanable article, wherein the first densified gas based dry-cleaning solution is a first carbon dioxide based dry-cleaning solution;
• contacting the dry-cleanable article with the first carbon dioxide based dry-cleaning solution;
• returning the first carbon dioxide based dry-cleaning solution from the wash tank to the divided working tank;
• transferring a second densified gas based dry-cleaning solution from a second liquid chamber of the divided working tank to the wash tank, wherein the second densified gas based dry-cleaning solution is a second carbon dioxide based dry-cleaning solution;
• contacting the dry-cleanable article with the second carbon dioxide based dry-cleaning solution;
• returning the second carbon dioxide based dry-cleaning solution from the wash tank to the divided working tank;
• and
• transferring a first volume of the first carbon dioxide based dry-cleaning solution from the first liquid chamber to a third liquid chamber of the divided working tank, wherein the step of transferring the first volume from the first liquid chamber into a third liquid chamber precedes the step of transferring a first carbon dioxide based dry-cleaning solution from the first liquid chamber to the wash tank.

A cleaning method comprising the steps of:

• transferring a first densified gas based treating solution from a first liquid chamber defined in a divided working tank to a wash tank containing an article;
• contacting the article with the first treating solution;
• returning the first treating solution from the wash tank to the divided working tank;
• transferring a second densified gas based treating solution from a second liquid chamber defined in the divided working tank to the wash tank;
• contacting the article with the second treating solution;
• and
• returning the second treating solution from the wash tank to the divided working tank;
• wherein the first and second liquid chambers share a common vapor space.