Vapour and liquid drum for a shell-and-tube heat exchanger

Method of operating a shell-and-tube heat exchanger comprising a shell enclosing a plurality of U-shaped tubes of a tube bundle, wherein each tube includes open first and second ends and is provided with a first tube portion and with a second tube portion that are hydraulically connected by a U-bend, wherein the open ends of each tube are connected to a tube-sheet and the tubes are vertically arranged and disposed downward with respect to said tube-sheet, wherein the shell is provided with an inlet nozzle and with an outlet nozzle, and wherein a pressure chamber is connected to the tube-sheet on the opposite side of the shell and above said shell, the pressure chamber being provided with a liquid inlet nozzle and a vapour outlet nozzle, wherein the pressure chamber contains a guiding jacket that, at a first end thereof, is sealingly joined to the tube-sheet or the first tube portions and, at a second end thereof that is opposite to the first end, is open, wherein the guiding jacket splits the pressure chamber into a first section, that is enclosed by the guiding jacket and is in communication with the first tube portions, and a second section, that is in communication with the second tube portions, wherein the first section and the second section are in communication with each other by way of the open end of the guiding jacket, and wherein the first section is provided with a vapour chamber, the method comprising:

• inletting a first fluid through the inlet nozzle of the shell,
• inletting a second fluid through the liquid inlet nozzle of the pressure chamber,
• introducing the second fluid in the first section of the pressure chamber into the open first ends of the tubes,
• flowing the second fluid within the tubes under natural circulation to indirectly perform a heat exchange with the first fluid and vaporize the second fluid during the heat exchange,
• discharging the second fluid from the open second ends of the tubes so that the second fluid enters the second section of the pressure chamber, and flowing the second fluid that has entered the second section of the pressure chamber toward the open second end of the guiding jacket so the second fluid enters the first section of the pressure chamber by way of the open second end of the guiding jacket, wherein the second fluid that is discharged from the open second ends of the tubes passes through the second section of the pressure chamber before entering the first section of the pressure chamber,
• having a liquid level of the second fluid located below said open end in the first section to separate the vaporized second fluid from a liquid portion of the second fluid at the open end, the vapour chamber being located above the liquid level,
• outletting the vaporized second fluid through the vapour outlet nozzle of the pressure chamber, and
• outletting the first fluid through the outlet nozzle of the shell.

Shell-and-tube heat exchanger comprising a shell enclosing a plurality of U-shaped tubes of a tube bundle, wherein each tube is provided with a first tube portion and with a second tube portion that are hydraulically connected by a U-bend, wherein open first and second ends of each tube are connected to a tube-sheet and the tubes are vertically arranged and disposed downward with respect to said tube-sheet, wherein the shell is provided with at least an inlet nozzle for inletting a first fluid and with at least an outlet nozzle for outletting the first fluid, and wherein a pressure chamber is connected to the tube-sheet on the opposite side of the shell and above said shell, the pressure chamber being provided with a plurality of nozzles for inletting and outletting a second fluid, said second fluid flowing under natural circulation within the tubes, to indirectly perform a heat exchange with the first fluid, and vaporizing during the heat exchange, wherein the pressure chamber contains a guiding jacket having opposite ends, the opposite ends being a lower end and an upper end, the lower end of the guiding jacket being sealingly joined to the tube-sheet or the first tube portions, the upper end of the guiding jacket being an open upper end, wherein the guiding jacket splits the pressure chamber into a first section and a second section, the first section of the pressure chamber being enclosed by the guiding jacket and being in communication with the first tube portions so that the second fluid in a lower portion of the first section flows into the first tube portions of the tubes by way of the open first ends of the tubes and is subject to the heat exchange in the tubes, the second section of the pressure chamber including a lower portion that is in communication with the open second ends of the tubes so that the second fluid in the second tube portions enters the lower portion of the second section of the pressure chamber by way of the open second ends of the tubes and flows upwardly in the second section toward the open upper end of the guiding jacket, the first section and the second section communicating with each other by way of the open upper end of the guiding jacket, whereby the second fluid is separated into a liquid phase and a vapor phase at the open upper end and the liquid phase that has been separated from the vapor phase flows into the first section, the guiding jacket being positioned between the open first ends of the tubes and the open second ends of the tubes so that the second fluid entering the lower portion of the second section of the pressure chamber by way of the open second ends of the tubes is separated from the first section of the pressure chamber and is only able to flow into the first section of the pressure chamber after flowing upwardly in the second section and passing the open upper end of the guiding jacket.