EWT Water Technology

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Dosing System

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Summary:

In water treatment, chemical conditioning is a process for altering the behaviour or properties of water by addition of chemical agents. These chemical agents may for example be pH-conditioners, inhibitors, dispersants, coagulants or flocculants, film-forming agents, or biocides.

A dosing system includes equipment for injection, handling, preparation, mixing, and storing of chemical agents. Depending upon the application and the type of chemical agent, this equipment may for example include metering pumps, transfer pumps, pipelines, valves, instrumentation, calibration vessels, storage tanks, agitators, chemical drip trays, chemical vapour traps, etc.

Metering pumps are usually designed as reciprocating pumps, e.g. diaphragm metering pumps or piston metering pumps. For certain applications, water-jet pumps are also used.

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Design Example:

Dosing and transfer system for volatile conditioning agents for boiler feed water treatment. Including metering pumps, transfer pumps, agitators, day tanks, calibration vessels, chemical vapours traps, valves, piping, and instrumentation.

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Applications:

• Raw water treatment: Removal of suspended solids by coagulation or flocculation, injected upstream of for example a →multi-media filter plant.
• Boiler feed water treatment: →Chemical conditioning of the water-steam-cylce by injection of for example trisodium phosphate and ammonia water.
• Recirculating cooling water treatment: →Chemical conditioning of the cooling water by injection of for example corrosion inhibitor, scale dispersant or biocide.
• Treatment of →reverse osmosis feed: Injection of antiscalant, in order to prevent or reduce mineral scale on the reverse osmosis membranes.
• Neutralisation of regeneration effluent from →ion exchange demineralisation plants: pH-adjustment by addition of e.g. hydrochloric acid (HCl) or sodium hydroxide (NaOH).
• Disinfection: Injection of for example chlorine (Cl₂) or sodium hypochlorite (NaOCl) into water.
• Chlorine removal: Injection of for example sodium sulphite (Na₂SO₃) into chlorinated water, for example from municipal supply.
• Iron removal: Injection of for example potassium permanganate (KMnO₄SO₃) into water, upstream of for example a →sand filter plant.

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Technical Data:

chemical agent mass flow		available within an extremely wide range, depending upon the dilution ratio
chemical agent dilution ratio		depending upon application requirements, limited by solubility, handling considerations, and safety considerations
chemical dilution volume flow		available from ≈ 0.05 L/h to ≥ 500 L/h, depending upon application requirements and liquid properties
discharge pressure		available from ≤ 10 bar to ≈ 250 bar, depending upon application requirements and liquid properties
amount of lines		usually 1x100% or 2x100%
storage tank volume		available from 35 L to ≥ 10 m³ usually 60 L to 1000 L
storage tank allowable pressure		usually atmospheric
storage tank allowable temperature		usually ≤ 40 °C
material options		metering pump wetted parts	• polyvinyl chloride (PVC) • polypropylene (PP) • polyvinylidene fluoride (PVDF) • Acrylglas (PMMA) • stainless steel (e.g. 1.4571)
		storage tank	• polyethylene (PE) • stainless steel (e.g. 1.4306, 1.4404)
		pipelines	• polyvinyl chloride (PVC) • polypropylene (PP) • polyethylene (PE) • polyvinylidene fluoride (PVDF) • stainless steel (e.g. 1.4571)
		valves	• polyvinyl chloride (PVC) • polypropylene (PP) • polyvinylidene fluoride (PVDF) • stainless steel (e.g. 1.4408)
		gaskets	• ethylene propylene diene monomer rubber (EPDM) • fluoroelastomer (FKM) • polytetrafluoroethylene (PTFE)
		skid	• polyethylene high-density (PE-HD) • stainless steel (e.g. 1.4301)
control options		process control	• depending upon application requirements
		metering pump stroke frequency	• local manual adjustment • remote, by analogue signal • remote, by pulse signal
		metering pump stroke length	• local manual adjustment • remote, by analogue signal
		filling of the storage tank, preparation of the dosing dilution	• manually • partly automated, PLC • partly automated, control circuit

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Downloads:

• drawing: high pressure dosing system, for boiler water treatment

→further downloads

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2018-05-05 • water treatment made in Germany • Company Information • Privacy