Procedure and equipment for injecting gas into liquids

A method and apparatus is shown for establishing a predetermined concentration of gas in the reactor core coolant for a pressurized water nuclear power system. Gas is added to core coolant water in a bubble column. The gas-water mixture flows through static mixers in the column to produce the desired gas concentration in the water.

TECHNICAL FIELD 
This invention is directed to a procedure for injecting gas into liquids, 
and, more particularly to the injection of hydrogen into the primary 
coolant of pressurized water nuclear power plants. 
BACKGROUND ART 
For example, it is not uncommon in nuclear power plants, to inject hydrogen 
gas into primary coolant water by spraying the primary coolant into an 
hydrogen atmosphere, e.g. into the hydrogen gas blanket of the makeup 
tank, or by bubbling hydrogen gas in the water phase of the makeup tank. 
The makeup tank among other things, is used to equalize primary coolant 
volume changes, and contains both the primary coolant and a hydrogen-gas 
blanket. 
These known procedures have the disadvantage that due to the large hydrogen 
volume in the makeup tank, a release of relatively large hydrogen volumes 
into the space surrounding the makeup tanks is possible, and therefore the 
occurrence of combustible gas explosions must be taken into account. 
Further, the gas/water concentration can not be precisely controlled. 
There is a need, therefore, to find a procedure through which a 
predetermined gas concentration can be reached in the liquid under 
consideration and through which the potential release of dangerous volumes 
of explosive gas can be minimized. 
SUMMARY OF THE INVENTION 
The problem is solved in that the liquid flows through a bubble column, 
only the gas volume necessary for reaching the required gas content is 
injected into the bubble column above the liquid inlet, and the gas and 
liquid are mixed prior to leaving the bubble column. 
The device used for implementing this procedure has a bubble column that 
contains several motionless mixers. The gas feed line is equipped with a 
gas pump, and the pipe section of the two-conduit gas injection line 
arranged inside the bubble column is equipped with nozzles. 
The nozzles, moreover, can be flushed with the aid of a bypass flow of the 
liquid to be gassed. An advantage of this feature is that the bypass flow 
conduits are connected with the pipe sections that support the nozzles. 
A ventilation line is also attached at the bubble column in order to 
prevent gas bubble formation in the primary coolant. Analyses measuring 
devices are installed in the liquid line upstream and downstream of the 
bubble column. 
The gas volume injected through the gas pump depends upon the pre-existing 
hydrogen concentration of the liquid to be injected with gas, and the head 
of the liquid flow. 
In accordance with a specific embodiment of the invention, the isolation 
valves of the bypass flow conduits can be manipulated to enable the 
nozzles to be covered with gas and rinse water on alternate sides.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In conduit 14 the primary coolant to be injected with gas flows into a 
pressurized water reactor system (not shown) in the direction of arrow 19, 
and after the adjustment of the volume flow control valve 10, flows into 
bubble column 6 at liquid inlet 20. With the aid of gas proportioning or 
dosage equipment, e.g. gas dosage pump 1, the hydrogen gas in conduit 2 is 
channeled into the bubble column 6 and is injected above liquid inlet 20 
via the double gas injection conduits 2a or 2b, and nozzles 5 or 5a. 
Hydrogen gas and primary coolant are now intensively mixed when liquid 
flows through motionless mixer 7. After the liquid has flowed through the 
mixer 7, the primary coolant which has been provided with the desired 
hydrogen content, discharges from the bubble column 6 through conduit 15. 
Automatic ventilation through the conduit 16, float valve 17 and isolation 
valve 18 ensures that no gas bubbles remain in the primary coolant. Bypass 
conduit 13 in which coolant flows in the direction of arrow 21, which 
comprises a certain portion of the primary coolant that to be injected 
with gas flows, branches off from the conduit 14. 
The mode of operation for implementing the flushing process enables the 
nozzles 5, 5a to be flushed alternately, or to be used for gas injection. 
For the case "flush nozzle 5", isolation valves 3 and 11a are closed and 
isolation valves 11 and 3a are open. For the case "flush nozzle 5a" 
isolation valves 3a and 11 are closed and isolation valves 11a and 3 are 
open. Check valves 4a, 12a, 4 and 12 prevent gas or flushing liquid from 
returning. 
An analysis measuring device 8 is installed in bypass conduit 13, which 
measures the hydrogen gas concentration of the liquid to be injected with 
gas so that exact gas dosing can be accomplished through the gas dosage 
pump 1 as a function of gas content and liquid volume in conduit 14. 
It should also be noted that the entire gassing and flushing process takes 
place automatically. 
Gassing in accordance with the principles of the invention now is possible 
in a simplified and advantageous manner. Nitrogen, moreover, can be used 
as a gas blanket for the makeup tank, in order to avoid the danger of a 
combustible gas explosion. 
An additional advantage of the invention is the fact that the hydrogen 
concentration of the reinjected primary coolant can be kept within a 
specified range during load change processes.