Chlorine is a strong oxidant that in normal conditions and in its pure state formsdichlorine, a toxic gas with a yellow-greenish colour formed by diatomic molecules (Cl2) that are about 2.5 times heavier than air and have an unpleasant smell.
Among its multiple applications and due to its powerful oxidising nature, it is widely used forwater purificationin sewage treatment plants and as a disinfectant in other applications.
In sewage treatment plants, instead of treating the water directly with chlorine gas,hypochlorite solutions are used that gradually release chlorine into the water and are capable of eliminating bacteria, fungi, parasites and viruses. However, in other sectors such as hospitals, chlorine is usually stored in bottles of liquified gas from which a leak could cause a harmful atmosphere and for this reason they are confined to containment rooms with safety systems. The disadvantage of chlorine used in this format is the conditions needed to store and move it. The high toxicity of the gas, which can be harmful at levels of 0.1 ppm in the air, means that it is necessary to handle it only with special equipment, safety programmes and contingencies duly established by competent staff.
The main technologies for eliminating chlorine; pros and contras:
- Outstanding among the most common chlorine elimination systems are dry media and wet scrubbers.
- Classic dry media have several advantages over wet scrubbers, which require considerably more maintenance. The instrumentation of wet scrubbers, which consists of pumps, nozzles and valves, is more complex. All this entails geater risk in their operation.
Another factor against wet scrubbers is directly related to the use of caustic liquids that generate a liquid effluent that requires subsequent treatment. On the other hand, dry media remove the pollutant permanently, transforming it into innocuous substances. Depending on the operating conditions, the spent adsorbent can even be used as a fertilizer.
Finally, another major advantage of dry media over wet scrubbers is that it is a solution able to maintain efficiency levels of over 99.9%, regardless of the load fed to the reactor.
All these advantages are leading the market to choose dry media over wet scrubbers as the most effective solution, both in technical and economic aspects.
Bioconservacion developed specific filtering medium to remove chlorine and acid vapours. Bi-On Clear is a clay impregnated with sodium thiosulfate capable of reaching chlorine elimination capacities of up to 9% p/p.
The BiOn Clear reaction mechanism removes chlorine through the processes of adsorption, absorption and chemisorption. The chlorine is transformed into innocuous solid substances that remain irreversibly trapped in the pellet.
This medium is especially designed to be used in applications where significant concentrations of chlorine may be released, such as the paper pulp manufacturing industry, sewage disinfection or the smoke from PVC laser cutting.
A practical case: A hospital in Peru
In 2013 Bioconservacion, together with its distributor in Peru, Requinor, carried out a project consisting of the introduction of chlorine safety equipment in a hospital in Peru.
Diagram of a chlorine adsorption safety system designed by Bioconservacion
In this hospital, chlorine cylinders are confined to a room with a specific volume and following the American Uniform Fire Code Article 63 (NFPA 1, 2006) equipment packed with BiOn Clear was designed.
The size of the equipment will vary depending on the standard followed in the design of the safety system. The conceptual basis of the standard consists of designing equipment able to adsorb the volume of chlorine gas released by the breakage of a chlorine cylinder. In this way, the safety system must be able to aspirate a certain gas flow rate so as to produce a depression in the room and efficiently adsorb the chlorine.
Bioconservacion designed equipment with the following characteristics:
- Reactor manufactured with polyester reinforced with glass fibre.
- Klopper-shaped ceiling
- Entrance handrail.
- Reactor height: 2950 mm.
- Outer Diameter: 1500 mm.
With this equipment it was possible to ensure a chlorine elimination efficiency of over 99.9%, ensuring an exit of under 50 ppbv at all times.
In addition to the reactor with the chemical medium, Bioconservacion/Requinor designed the pipes and the high-pressure centrifugal ventilator for the safety system.
As is habitual in our company, we continue to cooperate with Requinor on data exchange, assessment, incident resolution, etc, that allow closer ties and joint work on future projects.