External Gas Hot Air Furnace

Applications:

Desulfurization and denitrification industry: Flue gas heating support;

Iron and steel metallurgy industry: Pellet drying - Slag vertical mill - Coal mill, iron concentrate drying, manganese ore, zinc leaching residue, lump ore, pyrite, laterite nickel ore, lithium ore, mica ore, lead-zinc ore, tailings, siderite, etc.;

Chemical industry: Phosphogypsum, carbon material drying, desulfurization gypsum, lignite drying, white carbon black, perlite, compound fertilizer, carbide slag, quartz sand, coal slime, pulverized coal preparation, kaolin, etc.;

Ceramic industry: Spray drying tower, etc.;

Cement industry: Slag micro-powder, coal mill, raw material mill, ball mill, V powder selection grinding system, clay drying, yellow sand, dry-mixed mortar, slag drying, iron powder drying, building gypsum drying, etc.;

Solid waste: Sludge, tailings, carbide slag, phosphogypsum, limestone powder, fly ash, volcanic ash, etc.

Working Principle:

       The combustion chamber consists of a steel cylinder lined with castable refractory material, with the inner cylinder made of Q235 steel. An outer steel cylinder encloses the combustion chamber. The combustion torch is parallel to the axis of the combustion chamber, ensuring full, safe, and stable combustion inside. High-speed secondary air is injected around the furnace walls, enveloping the flame in the center of the furnace. The secondary air provides insulation and protection to the inner furnace walls and controls the combustion temperature to around 1000°C. The air supply enters from the front of the hot blast stove, passes between the outer and inner cylinders, and fully mixes with the high-temperature flue gas generated by combustion in the mixing chamber to produce hot flue gas at the required process temperature. The cold air passing between the inner and outer cylinders also cools the inner cylinder and insulates the furnace body. During operation, the outer cylinder wall temperature is less than 60°C.

Main Performance and Features:

★ Rational structure: The hot blast stove is designed with an all-steel structure, featuring low energy consumption, low wear, light weight, compact size, short installation period, low investment, easy maintenance, and mobility;

★ Convenient operation: No preheating is required when starting the furnace; it meets heating requirements immediately upon startup. Rapid cooling when stopping, with no need for an emergency chimney;

★ Wide adaptability: Capable of burning natural gas, coke oven gas, blast furnace gas, water gas, producer gas, mixed gas, and low-calorific-value gas;

★ High thermal efficiency: Combustion efficiency ≥ 99%; self-cooling insulation design with low outer wall temperature, thermal efficiency ≥ 98%;    

★ Stable heating supply: Heating temperature adjustable from 100–1200°C; flexible load regulation of the hot blast stove, controllable via fully automatic or manual methods.

Composition: Combustion system (electric ignition device, flame detection device), gas valve system, air supply system, control system, etc.

Combustion system mainly consists of: burner, electric ignition device, flame detection device.

Gas is fully burned in the burner flame tube and combustion chamber. The resulting hot flue gas mixes with incoming cold air in the mixing chamber to form flue gas at the desired temperature, providing a heat source for subsequent equipment.

Electric ignition device: Includes ignition electrodes and ignition head. During startup, a small pilot flame is ignited in the burner first, which then ignites the main flame. If the main gas calorific value is too low for direct ignition, a high-calorific-value gas is required for ignition;

Flame detection device: Mainly detects whether ignition is successful and whether the furnace flame is extinguished during combustion. Flame detection is a key component of the hot blast stove safety monitoring system.

Gas valve system mainly consists of: electric regulating valve, pneumatic quick shut-off valve, manual shut-off valve, ignition solenoid valve, pressure transmitter, high/low pressure switch, pressure gauge, vent valve, gas leak detector, pipelines, etc.

Gas is supplied from the main pipeline of the gas station to the gas valve system. The electric regulating valve adjusts the gas flow; when abnormal combustion occurs in the hot blast stove, the pneumatic quick shut-off valve rapidly cuts off the gas to ensure system safety; when not in use for extended periods, close the manual shut-off valve and open the vent valve; the ignition solenoid valve controls the ignition head gas; the pressure transmitter measures gas pressure and outputs remotely; the high/low pressure switch prevents operation under ultra-low or ultra-high pressure; the pressure gauge displays gas pressure on-site; the gas leak detector monitors on-site gas concentration in the valve system and alarms if超标.

Air supply system mainly consists of: combustion air fan, main air duct, distribution air fan, distribution air duct, combustion air regulating valve, distribution air regulating valve.

The combustion air fan provides the oxygen required for diesel combustion in the burner; air volume is controlled by the combustion air regulating valve; the distribution air fan supplies secondary air for the combustion chamber and cooling air for the mixing chamber. Air volume is controlled by the distribution air regulating valve.

Control system:

This system uses blast furnace gas/coke oven gas/natural gas, etc. as fuel, adopts automatic control, automatic ignition, and automatically regulates fuel volume, combustion air volume, and distribution air volume according to load changes. Basic safety protections: The burner includes safety protections for ignition failure, high flue gas temperature, high gas pressure, low gas pressure, emergency stop, etc. The system uses PLC control, can communicate with the central control via data bus, enabling central control, with on-site manual intervention possible.

Electrical Flow Diagram:

Negative Pressure Heating System Measurement and Control Process Parameters:

Site Photos: