| Three-Pass Fire-Tube Boiler | 0.5–30 t/h | 7–25 bar(g) | 82–91% | Light fuel oil, diesel oil, kerosene, and—when equipped with a heated fuel train—residual fuel oil. | Stable combustion with a low-NOx burner can typically achieve approximately 80–150 mg/Nm³ NOx, measured dry at 3% O₂; CO is commonly below 100 mg/Nm³ after proper commissioning. | Modulating burner, flame safeguard, automatic water-level control, low-water cut-off, pressure control, safety valves, feedwater treatment interface, and oxygen-trim option. | General process steam, food production, laundries, hospitals, commercial buildings, and medium-sized factories. |
| Packaged Water-Tube Boiler | 10–100 t/h | 15–60 bar(g) | 84–92% | Diesel oil, light fuel oil, residual fuel oil, and selected blended oils with suitable preheating and filtration. | High-capacity burners can be configured for low-NOx operation. Typical NOx performance is approximately 80–180 mg/Nm³ at 3% O₂, while particulate levels depend strongly on fuel grade and atomization. | PLC or DCS sequencing, multi-element drum-level control, combustion management, burner management system, furnace-pressure control, online alarms, and remote monitoring. | Refineries, chemical plants, textile mills, paper plants, district heating, and high-demand process users. |
| High-Pressure Water-Tube Boiler | 30–300+ t/h | 40–130+ bar(g) | 86–94% | Light fuel oil, diesel oil, residual fuel oil, and dual-liquid-fuel configurations where approved by the designer. | Requires engineered combustion and flue-gas treatment for strict limits. Low-NOx burners may reach approximately 50–120 mg/Nm³ NOx at 3% O₂; fuel sulfur affects SOx and acid-dew-point management. | Redundant burner management, advanced combustion control, three-element drum control, furnace draft control, oxygen trim, safety interlocks, soot-blowing, and DCS integration. | Large industrial plants, power and cogeneration facilities, petrochemical complexes, and export projects. |
| Once-Through Coil Boiler | 0.1–10 t/h | 10–100 bar(g) | 80–90% | Diesel oil, light fuel oil, kerosene, and selected low-viscosity oils. Fuel filtration quality is critical. | Compact combustion chambers can produce relatively high peak temperatures. Low-NOx burners are recommended; indicative NOx performance is approximately 100–200 mg/Nm³ at 3% O₂. | Fast-response PLC control, flow-based firing control, automatic feedwater regulation, flame monitoring, coil-temperature protection, low-flow trip, and pressure relief protection. | Intermittent steam demand, construction sites, mobile plants, small process lines, and space-constrained facilities. |
| Waste-Oil Steam Boiler | 0.3–15 t/h | 7–25 bar(g) | 70–85% | Filtered used lubricating oil, waste hydraulic oil, and approved waste-oil blends. Feedstock acceptance depends on ash, water, chlorine, metals, and viscosity. | Emissions are highly variable. Compared with clean diesel, particulate matter, CO, metals, and acid gases may be higher; a cyclone, bag filter, scrubber, or other treatment may be required. | Waste-oil conditioning, settling and filtration, storage-temperature control, metering pump, combustion-chamber temperature monitoring, flame safeguard, and ash-removal management. | Workshops, fleet depots, recycling facilities, and sites with a reliable supply of legally permitted waste oil. |
| Oil-Fired Boiler with Economizer | 1–100 t/h | 7–60 bar(g) | 88–95% | Diesel oil, light fuel oil, and residual fuel oil, provided that the economizer design controls corrosion risk and maintains the flue-gas temperature above the applicable acid dew point. | The economizer reduces fuel consumption but does not inherently remove pollutants. NOx and SOx remain primarily determined by burner design and fuel sulfur content. | Feedwater-temperature control, economizer bypass or protection, stack-temperature monitoring, oxygen trim, modulating burner, automatic blowdown control, and combustion interlocks. | Continuous-load plants where fuel savings justify additional heat-recovery equipment and maintenance. |
| Dual-Fuel Oil and Gas Steam Boiler | 1–100 t/h | 7–60 bar(g) | 85–94% | Diesel or light fuel oil combined with natural gas or liquefied petroleum gas. Separate fuel trains and combustion settings are required. | Gas firing generally produces lower particulate and SOx emissions than oil firing. Oil-mode NOx is commonly approximately 80–180 mg/Nm³ at 3% O₂, depending on burner and regulation. | Automatic fuel-changeover, dual burner management, gas-leak detection, flame supervision, fuel-pressure monitoring, PLC/DCS interface, load control, and emergency shutdown. | Facilities requiring fuel security, seasonal fuel flexibility, or backup operation during gas shortages. |