Unlocking the Potential of Small-Scale HRSG Boilers: A Guide to Safe Operations and Enduring Maintenance- MHl Power Dongfang Boiler Co., Ltd.

Ignition Protocols and Safety Imperatives

The journey to a safe and efficient operation of a small-scale heat recovery steam generator, such as the E-class and below HRSGs that are vital components of gas turbine combined cycle power plants and industrial production lines, begins with a meticulously crafted start-up protocol. Before initiating the sequence, operators must conduct a comprehensive safety audit, ensuring all valves, instruments, and pipelines are in their correct positions and free of leaks. It is crucial to confirm that water levels, pressures, and temperatures within the boiler are within specified ranges, and that the flue gas dampers or valves are open, allowing for a smooth flow of gases into the system. The start-up process should strictly adhere to the principle of "purge before ignition" to completely clear the boiler of any combustible gases, thereby preventing catastrophic explosions. Only after the pressure and temperature inside the boiler have slowly and steadily climbed to operational levels can the system be gradually brought online. This entire process demands continuous monitoring of all parameters, as any unusual fluctuation could signal a potential risk, requiring immediate corrective action or a shutdown for inspection.

Engineering Design and Efficiency Enhancement

At the core of a small-scale heat recovery boiler's design is the ingenious art of maximizing the utilization of high-temperature flue gas from industrial processes or gas turbines, transforming that thermal energy into valuable steam or hot water. The fundamental principle is to progressively absorb the heat from the flue gas using a series of heat exchange surfaces, including the superheater, evaporator, and economizer. To boost thermal efficiency, designers often opt for compact structures and specialized finned tubes, which significantly increase the heat transfer area, allowing the boiler to achieve high efficiency within a smaller footprint. The selection of materials is equally critical; high-temperature and corrosion-resistant alloys are instrumental in extending the boiler’s service life and enhancing its reliability. Furthermore, by optimizing the design of the flue gas flow path to reduce resistance, the energy consumption of the fan can be minimized, further contributing to the overall operational economy of the system.

Water Treatment and Corrosion Mitigation

HRSG boilers, particularly their low-temperature sections, are susceptible to unique corrosion challenges, most notably acid dew point corrosion. When flue gas containing sulfur cools down to a temperature below the dew point of acidic substances, sulfuric or sulfurous acid can form on the heat transfer surfaces, causing severe corrosion to the boiler tubes. To combat this pervasive issue, a comprehensive water treatment strategy is absolutely vital. This includes employing technologies like deaeration, softening, and chemical dosing for boiler feedwater to control water quality and prevent the formation of scale and oxygen-induced corrosion. During operation, measures can be taken to raise the wall temperature of the low-temperature sections, for instance, by using flue gas bypasses or special heat exchangers to prevent the gas temperature from dropping too low. In addition, regular chemical cleaning and passivation of the boiler can effectively remove corrosion products and form a protective film on the metal surface, bolstering its resistance to further deterioration.

Routine Maintenance and Fault Diagnosis

The long-term reliability of a small-scale HRSG boiler is contingent upon meticulous routine maintenance and prompt fault diagnosis. Maintenance activities should encompass regular inspections of both the internal and external surfaces of the boiler, with a specific focus on checking for soot or scale buildup on the heat exchange surfaces, which can drastically impede heat transfer efficiency. It is also imperative to verify that all instruments, valves, and safety devices are responsive and in good working order to ensure they function correctly in an emergency. For common malfunctions such as fluctuations in steam pressure, an abnormal rise in flue gas temperature, or tube leaks, technicians should follow a systematic troubleshooting approach. For example, abnormal steam pressure fluctuations might be related to the feedwater system or the combustion control system, while an increase in flue gas temperature could indicate sooting on the heating surfaces or a decline in heat exchange efficiency. By a comprehensive analysis of all parameters and drawing upon past operational experience, the cause of the fault can be quickly pinpointed, and appropriate repairs can be made to minimize downtime and economic losses.