Accurate costings for regenerating carbon

A major water utility in the South-east is one of the first to use Krohne's Optimass Coriolis mass flowmeter to eliminate human intervention and accuracy problems when calculating the cost of regenerating carbon slurry.

Water is purified at the reprocessing plant by passing it through a filtration bed of activated carbon, which removes minute contaminants. Eventually, the carbon needs to be regenerated because it becomes saturated by impurities and loses its filtration properties.

The spent carbon slurry is pumped from the filtration bed into tanker lorries. Before being transported from the reprocessing facility, a sample is taken to calculate the cost of regenerating it.

The cost is derived from the dry weight of the carbon. Once removed from the tanker, the sample is weighed, dried, then weighed again so its dry weight can be found. This process takes up to an hour to perform and is carried out with each load, which can be several times a week.

As well as being very time consuming, this method of determining cost is imprecise. As the carbon slurry is pumped into the tanker, heavier carbon particles settle to the bottom, leaving a mainly water solution at the top. Depending on where the sample is taken from the load, the calculated cost of regenerating the carbon can vary considerably.

Wellingborough-based Krohne was asked by the utility to devise a solution that would provide a real-time, accurate measurement of dry carbon contained in the slurry without the need for human intervention.

The company supplied its Optimass Coriolis mass flowmeter with integrated concentration measurement software to calculate the precise relationship between the slurry density and dry solids concentration.

The Optimass, which has a 50mm internal diameter measuring tube, is installed within the WwTW in line with the slurry output from the filter bed. Concentration measurement is a common requirement in many process industries, covering other diverse applications such as; sugar in soft drinks (Brix), starch solution (Baume), and water and oil mixtures (suspensions).

The company claims that, with user-friendly programming and software tools that make handling the process mathematics simple, Optimass has proven to be an attractive instrument to many customers.

It says that the instrument is ideal for this type of application because it is capable of measuring both mass flow and density to precise levels.

Its straight-tube design provides an unrestricted flow path that will not damage the carbon granules or become blocked and stop the flow. It also has sufficient data processing power to carry out complex calculations.

The solution allows the utility to manage accurately the cost of regenerating carbon. It has also fully automated the process and eliminated the human time and inaccuracies involved with traditional sampling methods and manual calculations.

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