The fabrication of two caustic dosing skids, destined for State-owned power utility Eskom’s 3 000 MW Kriel power station, in Mpumalanga, is on track to be completed at the start of July. The skids will be shipped to site during the second week of July and will be installed by the end of the month, Germiston-based pump distributor Ecochem Pumps projects division manager Trevor van Zyl tells Engineering News.

The work entails the design, fabrication, installation and commissioning of two new 2 500 ℓ/h caustic dosing skids and the upgrade of the ammonia dosing station at the power station’s demineralised water plant.

“Many of Eskom’s ageing coal-fired power stations, such as Kriel, have been considering the upgrade of chemical dosing stations at their demineralised water plants, as the quality of the demineralised water is critical in a power station environment.

“If the water sent to a boiler has not been demineralised beforehand, a scaling process within the boiler will take place, which could damage or permanently destroy the boilers. This can, in turn, potentially take the power stations off line,” explains Van Zyl.

Demineralisation is achieved by sending potable water through a chemical dosing station, with cation (positive charge) and anion (negative charge) resin vessels that remove the mineralisation in the water.

Ecochem Pumps was approached by the Kriel power station in November last year to undertake the installation of the caustic dosing skids and the ammonia dosing station in a sole-supplier arrangement, which requires Ecochem Pumps to supply a turnkey solution at the demineralised water plant.

Ecochem Pumps, as the South African agent of the range, suggested the use of Europe-based water and wastewater treatment products manu- facturer Milton Roy’s PrimeRoyal industrial-grade dosing pumps for the caustic dosing skids, owing to the robustness of the pumps, which can facilitate continual operational duty cycles.

The four PrimeRoyal pumps will be installed in a duty/standby configuration, with two pumps on each dosing skid. This configuration ensures that the duty pump undertakes the primary work, while the standby pump is relied on should there be a problem with the duty pump, explains Van Zyl.

He adds that accessories, such as external pressure relief valves, pulsation dampeners, pressure-indication gauges, back-pressure valves and calibration run pots can be added to the dosing skids. “Adding these accessories to the dosing skids is viewed as best engineering practice for a complete dosing system and will be included on the dosing skids installation at Kriel.”

Meanwhile, Ecochem Pumps is also upgrading Kriel’s existing ammonia dosing station.

In December last year, Ecochem Pumps was approached by the power station to consult with it on the products in service at the power station. The power station was advised to replace the current piston-driven pumps with more robust, diaphragm-driven industrial Milton Roy mRoy dosing pumps.

The project, therefore, entails the supply, installation and commissioning of 12 new 114 ℓ/h mRoy dosing pumps. Six of the mRoy pumps have already been delivered, with the remaining six pumps on order.

The pumps at the ammonia dosing station will also be installed in a duty/standby configuration at each of the power station’s six boilers.

The contract also entails adapting the existing pipework and upgrading the pipework to facilitate the installation of the new mRoy pumps.

The ammonia dosing station’s pumps and caustic dosing skids should be installed simultaneously, but, if the supply of the dosing pumps is delayed, Ecochem Pumps will initiate the installation in August, says Van Zyl.

In addition, Ecochem Pumps also submitted a quotation for the design, fabrication, installation and commissioning of a new sulphuric acid dosing station, also at the Kriel power station, in May.

Ecochem Pumps aims to be contracted, once again, as a sole-supplier, owing to its ability to facilitate the design, fabrication, installation and commissioning of the station and its equipment, notes Van Zyl.