Chemicals – Dosing and mixing tanks

As mentioned in last week’s blog, in industry many different chemicals are used, stored and dispensed – and this includes processes such as mixing and dosing.

Dosing Tanks

One common use for dosing tanks is for the treatment of raw water in industrial applications. This would often be by chlorination, and in liquid form would generally use tanks of sodium hypochlorite. Conversely, there might be processes using mains water which require de-chlorination by chemical process.

Swimming pools are another area where chlorination is required – at a much higher level than that used for drinking water, and any pool would require a dosing tank for the water supply to the pool.

Effluent treatment is another common use, where the dosing tank is part of the treatment system. More on this next week.

Other uses for chemical dosing tanks include:

• Boiler feed – e.g. for corrosion inhibitors.
• Cooling tower water – as this type of system is a high risk for legionella bacteria growth, it is necessary to treat the water to prevent bacterial growth.
• Flocculation – adding of chemicals to a mixture to cause suspended solids to flocculate or ‘clump’ to facilitate removal of solids.
• pH correction by addition of chemicals (acidic or alkaline) to provide the balance. This might be needed for potable (drinking) water in a private water supply system, or in food production industries.

The Enduramaxx range of dosing tanks are specifically designed for ease of use, and rotationally moulded (no joints) in chemical resistant MDPE which is compatible with most common chemicals. They have a raised top section for connection of a pump, and the lower top section contains the filling cap. In the standard natural finish, the tanks have a graduated scale on the outside to show level of contents, as the natural finish is translucent. However, light sensitive chemicals may require black (opaque) finish. The tanks are also available in blue, green or red, so you can colour code different tanks. In these cases, you would need a level gauge as well.

Dosing tanks will probably also need a bund, which has to contain 110% of the maximum tank capacity. These bunds, also constructed in MDPE, are purposed designed for each of the tank sizes. For instance, for a 50 litre dosing tank, you would need a 55 litre bund. This is essentially a dish in which the tank sits.

Mixing tanks

In industrial applications mixing tanks may be required for dry (powder or granular) materials, or for liquids.

The Enduramaxx chemical tanks which Tanks-UK supply are available in a thicker grade suitable for industrial liquids of up to 1.5SG. They are also available in 2SG for heavier specific gravity liquids – these are manufactured to order. For hazardous chemicals requiring a bund, either an external bund can be used, or you can specify a bunded tank, which means it has an integral bund – effectively a tank within a tank.

Batch tanks are a good choice for mixing equipment, since they have full size removeable lids, as well as the standard inlet lid. Open top tanks are another option.

We’re not necessarily talking about hazardous chemicals here, as mixing tanks are used extensively in the food and beverage industries as well. The MDPE used for the tanks is food grade, so is perfectly safe for this usage.

Cone tanks are a good choice as mixing tanks, and in the illustration here we have a cone tank used as a mixer by liquid flow alone, using a skid-mounted pump unit. With the right flow and draw off, it uses the centrifugal rotation of the liquid to create the mix.

For powders and granules, the best type of mixing tank, when used indoors, is possibly an open top cone tank. The open top means that the mixing equipment can sit on top on a frame, allowing space around it for the feed. This is an arrangement much like a domestic food mixer. The conical base is ideally suited to dry mixtures as it allows gravity feed to the outlet without the need for pumps.

Pumps

Where you do need pumps Tanks-UK can help you choose the right type for the application. For example, diaphragm pumps might be the best type for dosing tanks, depending on what liquids are involved.

Pumps and pipework need to be compatible with the substances being mixed, and the flow rate needs to be correct as well. Pumps are usually mains powered for this purpose, but other solutions are possible where mains supply is not an option.

Control panels

Dosing tanks in particular will probably need some form of control panel to complete the system, whether for manual or automatic operation. Please ask us for advice and information on the best type of control panel to complete your dosing system.

Just give us a call on 01953 665940 or email info@tanks-uk.com with your requirements and we’ll send you a quote.