Boiler blowdown: achieving economy of scale
Economy of scale: The cost advantage that arises with increased output of a product.
Scale buildup is a common issue with steam plant operation that can rob you of valuable BTUs, create efficiency loss, and even lead to leaks or vessel failure due to overheating or deterioration of the carbon steel tubes. Scale deposits created from the evaporation of steam can accumulate on heat exchange surfaces, and impede the boiler’s ability to transfer heat to water (decreasing the rate of steam generation).
Boiler blowdown should be scheduled one time per shift, ideally every 12 hours (industry recommendation) depending on usage, but at least every 24 hours. Maintaining proper blowdown frequency is one of the best ways to monitor and prevent buildup of scale or sludge in the boiler.
Bottom level valves and controls are the most common for boiler blowdown, but surface blowdown is becoming a more prevalent addition, continuously removing flyable impurities (too light to sink) formed during the evaporation of steam where it separates at the top of the boiler. Surface blowdown is normally fed to a flash tank and heat exchanger for heat recovery. Manual metering valves or automated – timed or continuous valves can be used to open a downstream valve to release impurities.
If you are experiencing a high level of scale, it is also advisable to check the chemical process or considering a third party chemical company to audit input water quality, recommended softeners or treatments, etc. to maintain the ideal range of conductivity for efficient steam generation.
Routinely eliminating water contaminants and scale with proper blowndown frequency helps ensure safe, clean operation and increase the longevity and thermal efficiency of your boiler. It can also mean considerable payback in fuel savings and equipment life.
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