Steam Boilers are integral in process plants and manufacturing units. Several process operations rely heavily on efficient steam boilers for processing, drying, and sterilizing purposes. Plant managers take every measure to ensure the smooth functioning of steam boilers and the safety of the process plant and operating personnel. Regular maintenance inspects the wear and tear in steam boilers and prevents it before it leads to mishaps. However, one of the main concerns of most plant managers is the increased use of natural resources for the combustion process in steam boilers. It consequently results in higher demand for energy, adding to the expense of the manufacturing facilities.
Energy Audit in Industries:
Energy audits aid industries or manufacturing facilities in assessing energy utilization and identify the areas that lead to the high amount of energy waste and measures to improve it. The energy auditor directs the audit by coordinating with the plant managers and operating staff to ensure precision in data and proper execution of the suggestions.
With the increasing cost of energy, the industries might face considerable losses if they make changes on guesswork without proper auditing. Energy audit assists the industries in evaluating energy wastage and suggests measures to reduce energy consumption. Energy Audits usually take place in 3 stages:
- Energy consumption since last 1 to 2 years
- Energy supply contracts and tariffs
- Floor area, number of staff members, production levels
- Benchmark level of energy use and cost
- Metering equipment
- Plant configuration
- Electricity configuration, condition, and controls
- Energy management process and policy
- Assessment management plan, if any
- Gas load profiles
- Internal temperature or humidity
- Ventilation rate
- Analysis of boiler flue combustion
Analysis and Reporting Phase:
- Finding complete energy efficiency
- Assessing Greenhouse Emission Index
- Analysis of life cycle cost
- Analysis of tariffs
Energy Audit for Efficiency Improvement in Steam Boilers:
Steam boiler systems with optimal efficiency lead to high production and eventually high profits for the manufacturing unit. Improving the boiler efficiency and capturing excess heat results in saving energy. Energy assessment of the steam boiler system includes the following factors:
Demand and Size of Boilers:
The heating demands during process operations may change in steam boilers, resulting in systems functioning below their optimum efficiency. Boilers are oversized due to factors such as unrequired additions and expansions. It results in boiler ‘short cycling,’ which occurs when the boiler quickly completes the process operation or heating demands and shuts down until the next process cycle. In such cases, a smaller size boiler that meets the required load demands of the facilities is ideal for saving energy.
Process facilities using multiple boilers can save energy by implementing boiler allocation strategies by operating it simultaneously under low-fire conditions. Such practice maximizes efficiency and reduces energy costs. Hot water boiler efficiency is also improved, by using automatic flow valves that shut off the boiler when not in use. It prevents the hot water from getting cool.
Flue Shut-off Dampers:
Heat loss to the chimney occurs significantly if the boilers shut down regularly because of load changes. Fully closing stack dampers help in preventing the loss of hot air. It functions when the boiler is not in operation.
Negligence in the regular maintenance schedule can negatively impact the burners and condensate return system in steam boilers. Such factors can account for up to 20% to 30% of boiler efficiency over the 2-3 years. A timely maintenance program ensures optimal performance of all the boiler components, resulting in significant savings and reducing air pollutant emissions.
Reduction in Fouling:
It is essential to control the fouling of the fireside of boiler tubes and scaling of the waterside of boiler tubes. A soot layer of 0.03 inches can reduce the heat transfer by 9.5%, and 0.18 inches of layer reduces it by 69%. Scale buildup of 0.04 inches in water-tube boilers can increase fuel consumption by 2% and even result in boiler tube failures. Boilers burning solid fuels like coal have a higher tendency of fouling compared to liquid or gaseous fuels.
Improper blowdown causes boiler water carryover to the steam or deposit formation and exceeding the range results in waste of energy, water, and chemicals. The blowdown rate depends on various factors such as boiler design, operating pressure, makeup water quality, and water treatment. Depending on the feedwater flow rate, the blowdown rate can range from 4% to 8%. Reducing the blowdown rate can decrease the energy loss, makeup water, and chemical treatment costs.
Reducing Excess Air:
Excess air used in burning the fuel causes wastage of heat while heating the air. Lack of maintenance in boilers consists of up to 140% of excess air resulting in waste gas. Boiler efficiency is increased by 1% for reducing 15% of excess air. It is necessary to inspect the fuel-air ratios regularly.
Preheating Boiler Water with Economizer:
Boiler feedwater can be heated by flue gases through an economizer which increases the water temperature in the boiler inlet. It consequently reduces the amount of heat needed for steam generation, thus saving fuels. Economizers can reduce the fuel requirement by 5 % to 10% by recovering waste heat.
Condensate and Heat Recovery:
Installation of condensing economizer can improve the overall heat recovery and bring about 10% steam boiler efficiency. Up to 80% of heat released through blowdown is recoverable using flash vessels and heat exchangers.
Combined Heat and Power:
Combined Heat and Power (CHP) or Cogeneration produces two forms of energy by using a single fuel source. The fuel energy is converted into mechanical and thermal energy. Thermal energy generates steam, hot air, and hot water, whereas mechanical energy produces electricity.
Benefits of Energy Audit:
- Reduces energy costs
- Reduces dependence on procuring energy sources externally
- Reduces environmental damage
- Reduces consumption of natural resources
- Reduce greenhouse emission
- Optimal performance of boiler components
Rakhoh Boilers has been a trusted name in boiler manufacturing and service providers for more than 38 years. We manufacture a range of efficient and reliable steam boilers and provide boiler-related services like energy audit, boiler automation, steam trap assessment, annual boiler maintenance, etc.
Explore our products and services at www.rakhoh.com