Clean Firetube Boiler Waterside Heat Transfer Surfaces Energy Tips

A steam energy tip sheet for the Advanced Manufacturing Office (AMO). The prevention of scale formation in firetube boilers can result in substantial energy savings. Scale deposits occur when calcium, magnesium, and silica, commonly found in most water supplies, react to form a continuous layer of material on the waterside of the boiler heat exchange tubes. Scale creates a problem because it typically possesses a thermal conductivity, an order of magnitude less than the corresponding value for bare steel. Even thin layers of scale serve as an effective insulator and retard heat transfer. The result is overheating of boiler tube metal, tube failures, and loss of energy efficiency. Fuel consumption may increase by up to 5% in firetube boilers because of scale. The boilers steam production may be reduced if the firing rate cannot be increased to compensate for the decrease in combustion efficiency. Energy losses as a function of scale thickness and composition are given. Any scale in a boiler is undesirable. The best way to deal with scale is not to let it form in the first place. Prevent scale formation by: (1) Pretreating of boiler makeup water (using water softeners, demineralizers, and reverse osmosis to remove scale-forming minerals); (2) Injecting chemicals into the boiler feedwater; and (3) Adopting proper boiler blowdown practices.

This revised AMO tip sheet on cleaning boiler water-side heat transfer surfaces provides how-to advice for improving industrial steam systems using low-cost, proven practices and technologies.

Even on small boilers, the prevention of scale formation can produce substantial energy savings. Scale creates a problem because it typically possesses a thermal conductivity an order of magnitude less than the corresponding value of bare steel.

This revised ITP tip sheet on cleaning boiler water-side heat transfer surfaces provides how-to advice for improving industrial steam systems using low-cost, proven practices and technologies.

Table of Contents: About the Author - Saturated steam temperatures at various boiler pressures - Boiler Energy and Power Units - Typical gross heating values of common fuels (based on approximately 80% fuel to steam efficiency) - Typical energy consumption and output ratings for a fire tube boiler - Steam tables suitable for pressure deaerators - Calculating Blowdown - Coefficients of thermal conductivity for some heat-exchanger metals and boiler deposits - Types of water or steam commonly employed in most HW heating and steam generating plants - Commonly occurring minerals in natural MU water sources - Specific waterside / steamside problems affecting MPHW and HPHW boiler plants - Salt concentration indicators - Summary of waterside / steamside problems affecting LPHW and LP steam heating boiler plants - FW contamination from MU water - FW contamination from returned condensate - Problems associated with the final FW blend - Deposition of boiler section waterside surfaces by alkaline earth metal salts, other inorganic salts and organics - Silica and silicate crystalline scales and deposits affecting boiler section waterside surfaces - Iron oxide and other boiler section corrosion debris deposits - Boiler section corrosion problems involving oxygen, concentration cells and low pH - Stress and high temperature related corrosion - Steam purity, quality and other operational problems - Specification for grades of high-quality water suitable for higher pressure WT boilers - Practical considerations for a RW ion-exchange softener - Types of Internal Treatment Program - Carbonate Cycle Requirement Calculations - Phosphate-Cycle Requirement Calculations - A Guide to Tannin Residuals in BW - Carbonate-Cycle Program. BW Carbonate Reserve Requirements by Pressure and Sulfate Concentration - Carbonate-Cycle Coagulation and Precipitation Program. Recommended BW Control Limits for Non-Highly-Rated FT Boilers Employing Hard or Partially Softened FW - Phosphate-Cycle Coagulation and Precipitation Program. Recommended BW Control Limits for Non-Highly-Rated FT Boilers Employing Hard, Partially Softened, or Fully Softened FW - Phosphate-Cycle Coagulation and Precipitation Program. Recommended BW Control Limits for Non-Highly-Rated WT Boilers Employing Hard, Partially Softened, or Fully Softened FW - Chelant demand (ppm product) per 1ppm substrate EDTA Chelant or All-Polymer/All-Organic Program. Recommended BW Control Limits for Fired WT Boilers Employing Demineralized or Similar Quality FW - Oxygen Solubility at Atmospheric Pressure - Properties of Oxygen Scavengers - Carbon Dioxide Evolution from FW Alkalinity - Amine Requirement to Reach a Stable Condensate pH - Amine Basicity Dissociation Constants - Neutralizing Amine Summary Notes - Some DR values for CO2, NH3 and neutralizing amines at various pressures - Calculating Alkalinity Feed-Rate Requirements - [ASME Consensus table 1: Suggested water chemistry limits. Industrial watertube, high duty, primary fuel fired, drum typeMakeup water percentage: Up to 100% of feedwater. Conditions: Includes superheater, turbine drives or process restriction on steam purity] - [ASME Consensus table 2: Suggested chemistry limits. Industrial watertube, high duty, primary fuel fired, drum type] - [ASME Consensus table 3: Suggested chemistry limits. Industrial firetube, high duty, primary fuel fired] - [ASME Consensus table 4: Suggested water chemistry limits. Industrial coil type, watertube, high duty, primary fuel fired rapid steam generators] - [ASME Consensus table 5: Suggested water chemistry limits. Marine propulsion, watertube, oil fired drum type] - [ASME Consensus table 6: Suggested water chemistry limits. Electrode, high voltage, forced circulation jet type] - Notes

This 6-hour quick book provides simple facts and energy efficiency opportunities in the areas of combustion management, makeup & feed water management, condensate return, blow-down system, waste heat recovery and steam distribution & utilization. This course is aimed at mechanical, chemical & process engineers, system design engineers working in power, oil & gas, chemical, metal & mining manufacturing and engineering industries, energy auditors, operational and maintenance personnel.

Incorporates Worked-Out Real-World Problems Steam Generators and Waste Heat Boilers: For Process and Plant Engineers focuses on the thermal design and performance aspects of steam generators, HRSGs and fire tube, water tube waste heat boilers including air heaters, and condensing economizers. Over 120 real-life problems are fully worked out which will help plant engineers in evaluating new boilers or making modifications to existing boiler components without assistance from boiler suppliers. The book examines recent trends and developments in boiler design and technology and presents novel ideas for improving boiler efficiency and lowering gas pressure drop. It helps plant engineers understand and evaluate the performance of steam generators and waste heat boilers at any load. Learn How to Independently Evaluate the Thermal Performance of Boilers and Their Components This book begins with basic combustion and boiler efficiency calculations. It then moves on to estimation of furnace exit gas temperature (FEGT), furnace duty, view factors, heat flux, and boiler circulation calculations. It also describes trends in large steam generator designs such as multiple-module; elevated drum design types of boilers such as D, O, and A; and forced circulation steam generators. It illustrates various options to improve boiler efficiency and lower operating costs. The author addresses the importance of flue gas analysis, fire tube versus water tube boilers used in chemical plants, and refineries. In addition, he describes cogeneration systems; heat recovery in sulfur plants, hydrogen plants, and cement plants; and the effect of fouling factor on performance. The book also explains HRSG simulation process and illustrates calculations for complete performance evaluation of boilers and their components. Helps plant engineers make independent evaluations of thermal performance of boilers before purchasing them Provides numerous examples on boiler thermal performance calculations that help plant engineers develop programming codes with ease Follows the metric and SI system, and British units are shown in parentheses wherever possible Includes calculation procedures for the basic sizing and performance evaluation of a complete steam generator or waste heat boiler system and their components with appendices outlining simplified procedures for estimation of heat transfer coefficients Steam Generators and Waste Heat Boilers: For Process and Plant Engineers serves as a source book for plant engineers, consultants, and boiler designers.