Patent ID: 7666366

Claim:
An apparatus for contacting two reactants to produce at least one product, said apparatus comprising: a vertically disposed vessel having a vertical axis, a sidewall, an upper portion and a lower portion; a draft tube comprising at least one heat exchange means, said draft tube providing a riser conduit within said draft tube and a downcomer conduit between said draft tube and said sidewall, said draft tube extending into the upper portion of said vessel and comprising at least one opening in said upper portion so as to provide fluid flow communication between the riser conduit and the downcomer conduit and extending into the lower portion of said vessel and comprising at least one opening in said lower portion so as to provide fluid flow communication between the riser conduit and the downcomer conduit; an inlet means for introducing said reactants; and a gas outlet; wherein: said upper portion of said vessel comprises a vessel head comprising said gas outlet means, said draft tube is suspended from said vessel head, said vessel head is demountably engaged with said vessel sidewall, and wherein said draft tube provided by said plurality of cooling tubes forms a first concentric circle at the bottom portion of said draft tube but wherein the top of said annulus is defined by two concentric circles defined by alternating the connection of the plurality of cooling tubes to said top so that said two concentric circles are characterized, respectively, by one having a larger radius than said first concentric circle and one having a smaller radius than said first concentric circle.