Chemical cleaning method and system with steam injection
Disclosed are methods and apparatus for cleaning heat exchangers and similar vessels by introducing chemical cleaning solutions and/or solvents while maintaining a target temperature range by direct steam injection into the cleaning solution. The steam may be injected directly into the heat exchanger or into a temporary side stream loop for recirculating the cleaning solution or admixed with fluids being injected to the heat exchanger. The disclosed methods are suitable for removing metallic oxides from a heat exchanger under chemically reducing conditions or metallic species such as copper under chemically oxidizing conditions. In order to further enhance the heat transfer efficiency of heating cleaning solvents by direct steam injection, mixing on the secondary side of the heat exchanger can be enhanced by gas sparging or by transferring liquid between heat exchangers when more than one heat exchanger is being cleaned at the same time.
1. A system for removing deposits and impurities from a secondary side of a heat exchanger comprising:
a first adapter configured for temporary installation on a first conventional access penetration, the first adapter further comprising
a flange configured for mating to the access penetration;
means for securing the adapter to the access penetration;
a conduit for introducing or removing fluid through the access penetration; and
an opening provided within the secondary side of the heat exchanger;
a steam source configured for connection to the conduit,
a gas source configured for connection to the conduit; and
a controller configured for controlling the steam injection into the secondary side of heat exchanger through the adapter,
wherein, in use, said system is adapted to admix a gas supplied by the gas source with the steam supplied by the steam source to form a combined gas stream in the conduit for injection in the secondary side of the heat exchanger and wherein said gas that is admixed with the steam does not condense during use of said system.
2. The system according to claim 1 wherein the opening is configured as an eductor.
3. The system according to claim 1 wherein the opening is configured as multiple eductors.
4. The system according to claim 1 wherein the opening is selected from a group consisting of regulator direct steam nozzles, spargers, eductors and combinations thereof.
5. The system of claim 1 , wherein the heat exchanger is a steam generator of a nuclear pressurized water reactor.
6. The system according to claim 1 , wherein a concentration of the gas is selected to reduce the potential for cavitation damage within the conduit and/or at the opening.
7. The system according to claim 6 , wherein the gas comprises between 0.01% and 3% of the combined gas stream.
8. The system according to claim 1 , wherein the conduit comprises a steam injection nozzle configured to, in use, entrain a bulk fluid present in the steam generator during injection in the secondary side of the heat exchanger of the combined gas stream through the steam injection nozzle, such that entrainment of said bulk fluid promotes mixing of the combined gas stream with the bulk fluid and ensures that the combined gas stream ejected from the steam nozzle is substantially in thermal equilibrium with the bulk fluid.