To improve the processing capacity of direct-fired furnaces for high-concentration waste gases, a systematic design improvement is needed across seven dimensions: combustion chamber structure, temperature control precision, mixing efficiency optimization, waste heat recovery system, application of corrosion-resistant materials, safety protection mechanisms, and intelligent control system. This will achieve efficient decomposition, stable operation, and long-term reliability.
The combustion chamber structure is the core of improving processing capacity. Traditional direct-fired furnaces often employ a single combustion zone design, which can lead to incomplete combustion and residues of some high-boiling-point organic compounds (such as polycyclic aromatic hydrocarbons and halogenated hydrocarbons) in high-concentration waste gases. An improved solution could introduce staged combustion technology, dividing the combustion chamber into a high-temperature oxidation zone and a deep pyrolysis zone: the former maintains a high temperature of 850-950℃ through direct fuel injection to ensure rapid oxidation of high-concentration organic compounds; the latter utilizes secondary combustion to raise the temperature to 1100-1200℃, breaking down recalcitrant substances such as dioxins. Simultaneously, the combustion chamber volume must be designed to match the waste gas flow rate and concentration to avoid insufficient space leading to shortened reaction time.
Temperature control precision directly affects decomposition efficiency. High-concentration exhaust gases exhibit significant fluctuations in organic matter concentration. If temperature control lags, localized low-temperature zones can easily occur, leading to incomplete decomposition. Multi-zone independent temperature control technology is necessary. High-precision thermocouples should be placed at different locations within the combustion chamber, combined with a fuzzy PID algorithm to dynamically adjust the fuel supply, ensuring temperature fluctuations in each zone are controlled within ±15℃. Furthermore, for high-concentration exhaust gases containing halogen compounds such as sulfur and chlorine, oxygen content must be controlled through nitrogen dilution or air-fuel ratio adjustments to prevent the formation of secondary pollutants.
Optimizing mixing efficiency is crucial for improving treatment capacity. Particulate matter and oil mist in high-concentration exhaust gases can easily lead to excessively high local concentrations, affecting combustion uniformity. Improvement solutions include adding swirl vanes or a venturi structure to the inlet, utilizing airflow turbulence to enhance mixing of exhaust gas and combustion air, shortening the residence time to over 0.75 seconds. For high-concentration exhaust gases containing viscous substances, a combination of pre-spray cooling and electrostatic precipitator processes can be used to remove large particulate impurities before entering the direct-fired furnace, preventing burner nozzle clogging.
The design of waste heat recovery systems must balance efficiency and stability. The combustion of high-concentration waste gas releases a large amount of heat; direct emission not only wastes energy but may also damage equipment due to localized overheating. Shell-and-tube heat exchangers or heat pipe technology can be used to recover heat from high-temperature flue gas (>500℃) for preheating intake air or steam production, increasing the overall system thermal efficiency to over 70%. For waste gas concentrations ≥3000mg/m³, self-heating operation can be achieved through heat balance calculations, reducing auxiliary fuel consumption.
The application of corrosion-resistant materials is crucial for extending equipment lifespan. High-concentration waste gas often contains acidic gases (such as HCl, SOx) or halogen compounds, making traditional carbon steel prone to corrosion at high temperatures. The combustion chamber should use acid-resistant materials such as SiC (silicon carbide) or high-chromium bricks, with corrosion resistance controlled to within 0.1mm/year and thermal shock resistance exceeding 10 cycles (1100℃→room temperature). For scenarios where exhaust gases contain alkali metal compounds such as Na/K, an online cleaning system should be added to the bottom of the combustion chamber. This system uses high-pressure water jets and chemical cleaning agents to periodically remove coking, preventing equipment damage caused by a decrease in the ash melting point.
Safety protection mechanisms are essential for handling high-concentration exhaust gases. When the exhaust gas concentration exceeds 25% LEL (lower explosive limit), an online LEL monitoring and emergency pressure relief device must be installed to achieve rapid explosion relief within 3 seconds. Simultaneously, the combustion chamber should employ an explosion-proof valve and temperature interlock design, automatically cutting off fuel supply and activating nitrogen inerting protection when the temperature rises abnormally. For high-concentration exhaust gases containing combustible dust, a spark detector and extinguishing device should be added to the intake pipe to prevent backfire from the combustion reaction to upstream equipment.
The integration of an intelligent control system can improve processing capacity and operational efficiency. By deploying a data cloud platform, key parameters such as combustion temperature, pressure, and O₂/CO concentration can be monitored in real time. Machine learning algorithms can be used to predict equipment failures (e.g., warnings when heat exchanger pressure difference > 1500 Pa).
