In evaluating options, the project team considered the plant’s unique site and operational factors, including the location of the dewatering bunker, the current condition of hoppers and associated equipment, and the operations of truck traffic in the hauling of ash. Water supply issues also fed into the analysis, from water supply to site water redirection and water balance.
Public Service Company of New Mexico (PNM) first considered a more typical Submerged Chain Conveyor (SCC) solution. A simple and robust piece of equipment, it’s been a standard option for more than 30 years. But this solution can be difficult to fit, and so installation can cause longer outages. It also would have been more expensive. PNM needed customer payback by 2022.
A newer technology — a Submerged Grind Conveyor (SGC) — emerged as the preferred choice to upgrade this particular plant quickly and cost-effectively with minimal operational impact. An SGC offered several benefits:
- By replacing the sluice pipe with submerged drag chain conveyers, it allowed for the economical reuse of the station’s existing hoppers, clinker grinders, ash gates, crushers and other current equipment on the bottom of the boiler.
- It didn’t require ash transport water, which eliminated some potential regulatory risk in the event of a discharge.
- Its smaller, more flexible design meant the team could plan a retrofit that minimized the need for demolition and moving of major equipment — greatly reducing operational downtime.