Chlorination system for a water to be treated

A system for chlorination of a fluid to be treated, which includes a container containing trichlorocyanuric acid in a solid and compact form, a first pipe for supplying the container with dissolving fluid, an evacuation pipe in which the chlorinated fluid circulates, connecting the container to a pipe which contains the fluid to be treated, a chlorine analyzer connected to the pipe and which includes a mechanism for continuously measuring the amount of active chlorine in the treated fluid and released constantly by direct contact of the fluid to be treated with a surface of the trichlorocyanuric acid; and a flow rate regulation mechanism connected to a supply and including a mechanism to for constantly varying a continuous flow rate of the dissolving fluid passing into the container as a function of the amount of active chlorine present in the treated fluid and measured by the chlorine analyzer.

TECHNICAL FIELD 
This invention relates to a chlorination system for water for industrial 
use or for consumption and more particularly for water used in a single 
pass system and still more particularly for water that is used in the 
petroleum industry. 
BACKGROUND ART 
Generally, sterilization of water is essentially performed by chlorination 
obtained either by an electrochlorination or by an addition of Javelle 
water or of liquid chlorine. 
Actually, surface water such as that found in seas and lagoons contains 
various organic elements which can proliferate and thus cause fouling of 
the water circulation pipes, leading to very considerable head losses, a 
considerable increase in the rate of clogging of the filters, or further, 
a clogging of the safety filters by growth of Copepoda whose eggs pass 
through filtering media such as prelayers. Thus, it has been found that 
sterilization of water can be as important as the filtration or the 
anticorrosion treatment to prevent deposits and, in the case of the 
petroleum industry, to prevent clogging of the formation into which water 
is injected. 
Javelle water, whose concentration is expressed in chlorometric degree, 
exhibits drawbacks in industry for sterilization of water because it is 
susceptible to aging and unstable in high concentration, loss of activity 
being able to reach 6 to 10 chlorometric degrees during the first 24 hours 
after production. Because of this, it is necessary to provide fresh 
Javelle water several times per week. 
Liquid chlorine is still more difficult to handle because of injection 
systems that are relatively complex to put in place, not taking into 
account the safety problems which necessitate taking great precautions. 
Also, the shipping, handling and storing of empty bottles that have 
contained liquid chlorine require the same type of precautions. 
Another chlorination method is the one called electrochlorination which 
uses electrolysis. Electrochlorination is widely used for treating sea 
water despite the drawbacks due to the considerable maintenance required; 
however, when the salinity of the water to be treated is less than that of 
the sea water, the production of chlorine by the electrolysis cell lowers. 
For example, for saline concentrations less than 4 g/l, the faradic output 
is low and the dimensioning of the chlorination unit becomes important for 
productions of chlorine necessary for the treatment. 
In a closed-loop recycling system, for example in the treatment of swimming 
pool water, most generally chlorocyanuric compounds are used which exhibit 
the advantage of having a slow solubility in water and of containing more 
than 88% by weight of active chlorine, as is the case for 
trichlorocyanuric acid. However, the treatment of water in a closed-loop 
recycling system, for example in a swimming pool, requires only an 
adjustment of the amount of chlorine contained in the volume of water in 
the system. This is obtained by periodic addition and "all or nothing" 
operation of the chlorination cell. The amount of chlorine contained in 
the treated water can vary rather considerably but without exhibiting a 
drawback, the chlorine keeping a sufficiently long time and without 
significantly increasing the consumption of active products. 
Trichlorocyanuric acid mixed with boric acid and with calcium stearate is 
also used for the treatment of municipal waste water, as is described in 
U.S. Pat. No. 4,054,518. In this patent, the compound described is in the 
form of tablets, placed vertically in a pipe in which the water to be 
treated circulates. Although it involves a single pass system and the 
surface of the tablets of compound exposed to the water is a function of 
the flow rate of the water in the pipe, it does not comprise any means for 
intervening constantly and in real time on the amount of active chlorine 
released by the tablets. Actually, the relation which exists between the 
tablets and the water flow rate comes from the sole surface of the tablets 
in contact with the water. The higher the layer of water is in the pipe, 
the more immersed are the tablets. 
DISCLOSURE OF INVENTION 
This invention has as its object to eliminate said drawbacks and to propose 
a system suitable for water consumption in a single pass system and which, 
continuously, makes it possible to adjust the amount of active chlorine to 
be introduced into the water to be treated at the optimum value for the 
treatment to be successful. 
This invention has as its object to provide a system for chlorination of a 
water to be treated, of the type comprising a volume or container 
containing a reserve of trichlorocyanuric acid in the form of compact and 
solid pellets, means to supply said volume with water, an evacuation pipe 
in which the water charged with chlorine circulates, connecting said 
volume to the line of water to be treated, a water line in which the 
concentration of active chlorine is analyzed continuously by an automatic 
analyzer which sends a signal to a regulator making it possible to act on 
a regulation valve causing the water flow rate passing through the volume 
to vary and, thereby, causing the flow of active chlorine injected into 
the line of water to be treated to vary. 
By constantly measuring the active chlorine content in the water to be 
treated, it is possible to act on the flow rate of water passing through 
the volume that contains the pellets with the trichlorocyanuric acid and 
also on the amount of active chlorine to be produced to inject into the 
water to be treated. 
Furthermore, the active chlorine content can be adapted as a function of 
the nature of the living or inert beings that can be found in the water to 
be treated, to reduce considerably both the fouling of the pipes and the 
clogging of the filters which, thanks to this invention, have a longer 
cycle time.

The system diagrammed in the rectangle represented by broken line 1 
comprises a dissolver 2, a flow rate indicator 3 and a chlorine analyzer 
device 4. A pipe 5 with a diameter appropriate to the flow rate of water 
to be treated, for example 200 m.sup.3 /hour, has one end immersed in the 
water, and comprises a pump 6 for circulating and bringing the treated 
water to the treated water consumption installation, not shown. 
The supplying of dissolver 2 with water is performed by a main pipe 7, 8 
and manual valve 9, said pipe 7 being connected to pipe 5 so as to benefit 
from the pressure existing in said pipe 5, downstream from pump 6, which 
assures the power necessary for the circulation of the water in dissolver 
2. The flow rate of water introduced varies within wide limits and it is 
adjusted by an automatic valve 10 placed on main pipe 7. A pipe 11 for 
extraction of chlorinated water connects dissolver 2 to pipe 5 for water 
to be treated. 
Dissolver 2 is equipped with a quick-opening cover 12 for loading pellets 
13 of trichlorocyanuric acid which, on contact with the water introduced 
by pipe 8 at a flow rate, for example, between 1 and 10 m.sup.3 /hr, 
dissolve and release active chlorine. The chlorinated water is extracted 
through pipe 11 and injected into pipe 5 for water to be treated. The 
total weight of the pellets placed in the dissolver is quite obviously a 
function both of the flow rate and of the frequency of anticipated 
reloading; in tests performed, it has been on the order of 200 kgs. 
The chlorine analyzer of the ordinary type will not be described in detail, 
it delivers electrical signals between 4 and 20 mA, to a signal 
transmitter 14 by a line 15. A regulator 16 is connected by a line 17 to 
signal transmitter 14 and by a line 18 to a control element 19 of 
automatic valve 10. 
A sampling pipe 21 connects chlorine analyzer 4 to water pipe 5 at a point 
located downstream from pump 6 so that analyzer 4 continuously analyzes 
the content of active chlorine present in the treated water which is sent 
to the petroleum installation, the water analyzed then being evacuated to 
a tank, not shown, through an adjustable drain 20. 
When a variation in the chlorine content is detected by analyzer 4, the 
latter emits a signal which is transmitted to regulator 16 via signal 
transmitter 14, regulator 16 governs-- by means of device 19-- the partial 
closing or opening of automatic valve 10 so as to adjust the flow rate of 
water introduced into dissolver 2 at the appropriate value. 
Manual valve 9 is provided for the cases where there would be failure in 
the automatic circuit or in certain extreme cases, the operating 
conditions are such that automatic control does not prove to be necessary. 
Of course, the invention is in no way limited to the embodiments described 
and represented, it is capable of numerous variants accessible to a person 
skilled in the art depending on the applications planned, without 
departing from the scope of the invention. 
Finally, means are provided to measure the level of undissolved pellets 13 
in dissolver 2, said means consisting of a graduated rod 23 passing 
through cap 12, equipped with a feeler in the form of a blade 24 at its 
lower end and guided through a gland 25 of sufficient length to assure the 
verticality of said rod 23. 
Preferably, all these means made of a material resistant to chlorine 
attack, such as for example PVC.