Patent Application
20050279089
1. Field of the Invention
The present invention relates generally to the field of direct contact pre-condensers. More specifically, the present invention relates to a sub-zero condensation vacuum system for pre-condensing water vapor for creating a vacuum.
2. Background of the Prior Art
In glycerine refining or any other steam distillation under vacuum, condensable and non-condensable vapors must be removed from the process stream in order to complete the refining process. The vapors from the process stream are removed by sending them directly in to a vacuum system in which the vapors can be condensed or otherwise removed.
In the area of condensers, it is known to provide a low pressure region into which vapor can exhaust, the condenser also having a condensate chamber for collecting the condensate.
Traditional vacuum systems, such as a steam ejector with contact or surface condensers, or hybrid systems with steam ejectors with condensers and a liquid ring vacuum pump are currently used to evacuate the gases and vapors in the glycerine refining process and in other such processes that require operation under a vacuum and use sparging or stripping steam.
The present invention provides a pre-condenser for condensing vapors at sub-zero degree Celsius temperatures without the formation of ice.
A brine solution is delivered from a brine storage tank to a brine metering pump. The brine metering pump is able to control the dispensing of brine solution to achieve a predetermined salt concentration. The resulting brine solution is cooled in a pre-condenser cooler to a sub-zero degree Celsius temperature.
A pre-condenser has a series of inlets for receiving the brine solution and dispensing the brine solution therein. A top portion of the steam condenser is connected to a vacuum system. A lower portion of the pre-condenser has an inlet for receiving vapors and gases from a scrubber, that are to be condensed in the pre-condenser.
The pre-condenser contains a packing material for maximizing contact between the brine solution and the vapors and gases. The brine solution travels toward the bottom of the pre-condenser by gravity while the vapors and gases travel counter-currently towards the top of the pre-condenser as a result of the connection to the vacuum system.
As the brine solution contacts the vapors, the vapors are condensed at sub-zero degree Celsius temperatures without the formation of ice. The condensed vapors are removed with the brine solution through an outlet in the lower portion of the pre-condenser. The remaining gases are removed through the top outlet via the vacuum system.
The brine solution leaving the pre-condenser is returned to the brine storage tank and may by recycled to repeat this process.
A brine storage tank 12 is shown having a brine solution therein, such as sodium chloride or a similar salt in water. The brine storage tank 12 has an outlet 14 that feeds to a line 16. The line 16 has a brine metering pump 18 wherein the brine is pumped through the line 16.
The brine is fed into a mixer 24 wherein the mixing means 26 therein allows the salt concentration to reach the predetermined concentration level.
The brine solution from the mixer 24 is then delivered to a pre-condenser cooler 28 by a pre-condenser pump 30. The pre-condenser cooler 28 cools the brine by supplying a chilled glycol solution from a chiller 32. It is contemplated that the chilled glycol solution be at −15 degrees Celsius when delivered to the pre-condenser cooler. The glycol solution cools the brine solution by surface contact and then the glycol solution is returned to the chiller 32.
It is contemplated that the brine solution should be cooled in the pre-condenser cooler to a temperature below 0 degrees Celsius so that the brine solution can be used to condense water vapor at sub-zero temperatures without the occurrence of ice formation.
The chilled brine solution is fed from the pre-condenser cooler 28 to a pre-condenser 34. The pre-condenser 34 has one or more inlets 36 in a sidewall for delivering chilled brine solution thereto. The pre-condenser 34 has a top portal 38 for connection to a vacuum system 40.
A vapor and gas inlet 42 is positioned at a bottom portion of the pre-condenser 34 for receiving vapor and gases from a process stream.
The vacuum system 40 causes the vapor and gases to travel upwardly within the pre-condenser 34 as the vapor and gases come into contact with the chilled brine solution. The brine solution is dispensed to various parts of the pre-condenser 34 and travels downwardly due to gravity.
At least a portion of the pre-condenser 34 is filled with a packing material 44 to increase the contact surface area of the chilled brine solution to improve both heat and mass transfer. This increases the contact between the chilled brine solution as it travels counter current against the upward flow of the vapors and gases.
The chilled brine solution is dispersed within the chamber of the pre-condenser by a dispensing means 46 so as to provide maximum coverage and dispersion within the chamber of the pre-condenser 34. A dispensing means 46 is positioned vertically above the inlet 42 for the vapors and gases to initiate condensation of the vapors and gases.
The vapors are cooled by the brine solution to a sub-zero temperature and condensed as slightly diluted brine without any ice formation. The condensation at temperatures below 0 degrees Celsius generates the vacuum required in the process. The resulting brine solution is transferred by gravity through the outlet 48 in the bottom of the pre-condenser 34 and returned to the brine barometric seal 50. From the barometric seal 50, the brine can be re-circulated with the brine pump 18.
The water vapor load of the gas and vapor leaving the gas outlet of the pre-condenser is drastically reduced, such that the size of the vacuum system 40 and utilities consumption required to remove the remaining vapor and gas are greatly reduced as a result of the sub-zero pre-condenser system 10.
The residual gases can be sent to a vacuum system 40 such as a vacuum system having steam ejectors with condensers and/or a liquid ring vacuum pump to evacuate the residual gases to the atmosphere.
As shown, the vacuum system 40 may include a steam inlet 52 positioned near the outlet 38 of the pre-condenser 34 allowing the steam to extend through the structure of the vacuum system 40 to a vessel 54 having a water inlet 56 at a top portion and connected to a hot well 58 at a bottom portion. The vessel 54 is connected to yet another similar vacuum system 60 that receives steam and water therein wherein this second vacuum system 60 has a second vessel 62 that is likewise connected to the hot well 58. The entire combination of the first and second vacuum systems 40, 60 are operated in conjunction with a vacuum pump 64 connected to the second vessel 62.
