Understanding the Steam Boiler Furnace: Key Components and Functions

Steam boiler is widely used in industrial production, heating system and energy field, and its furnace, as one of the core components, plays a decisive role in the thermal efficiency and operation safety of boiler. In order to fully understand the function of the furnace, we need to systematically analyze the structure, type, heating principle, operation mode and the relationship between the furnace and the boiler of the steam boiler.

The Anatomy of a Steam Boiler

A steam boiler has several key parts. These include the furnace, drum, heating surface, flue gas path, burner, control system, and water supply system. Each part plays a crucial role in the boiler's efficiency and safety.

Furnace

The furnace is the heart of the boiler. It's where fuel burns, releasing heat. The furnace must withstand high temperatures and resist corrosion.

Its design depends on the fuel type. This ensures efficient burning and less waste heat.

Drum

The drum is at the top of the boiler. It holds water and steam, keeping the pressure balanced. Inside, you'll find valves and other important parts.

The drum's size affects the steam quality and system stability. It's vital for the boiler's performance.

Heating surface

The heating surface absorbs heat from the furnace. It includes pipes and walls that help heat the water.

This surface is divided into radiation and convection areas. Together, they efficiently absorb heat.

By doing so, they heat the water effectively. Proper arrangement can boost efficiency and extend the boiler's life.

Flue Gas Path

The flue system carries hot gases out of the boiler. It also recycles some heat, improving efficiency.

This path includes primary and secondary flues, and the chimney. It's essential for waste gas removal and heat recovery.

Good design reduces exhaust temperature. This boosts energy efficiency.

Burner

The burner mixes fuel and air for ignition. It comes in types for different fuels.

It atomizes or gasifies fuel for efficient combustion. Smart designs adjust power based on load, saving energy.

Control System

Modern boilers have automatic control systems. These monitor temperature, pressure, and more for safe operation.

These systems handle ignition, alarms, and water management. They also offer remote control and fault diagnosis. Advanced systems connect to DCS or SCADA for centralized monitoring.

Water supply system

The water supply system adds water to the boiler. It keeps the water level right and replaces lost water.

It includes a pump, valve, tank, or deaerator. Together, they ensure water quality and quantity.

This system prevents dry burning and ensures water quality. Its efficiency is crucial for boiler longevity and reliability.

Safety Devices

Boilers are high-pressure equipment. They need complete safety accessories to prevent accidents.

Common safety accessories include safety valves, water level gauges, pressure gauges, and alarms. These help prevent explosions and remind operators to act quickly.

These accessories are crucial for safety. Their installation and regular checks are strict and cannot be ignored.

Types of Steam Boilers

Steam boilers come in many types, based on their structure and heat transfer. Fire tube and water tube boilers are the most common. Choosing the right type is key for efficiency and economy in industrial settings.

1. Fire-tube Boiler

The fire tube boiler has high-temperature flue gas inside the pipes. Water surrounds these pipes. Heat from the pipes warms the water, causing it to evaporate.

Applicable scenarios:

They are best for small to medium-sized industrial users. This includes food processing, chemical plants, and heating needs.

Advantages:

Simple structure: They are compact and easy to install and operate.

Low cost: They are affordable to make and maintain, great for those on a budget.

Fast start-up: They heat up quickly and handle load changes well.

Convenient maintenance: Their simple design makes maintenance easy.

However, fire tube boilers have limits. They can't handle large steam demands. Their pressure capacity is low, and their thermal efficiency is not as high as water-tube boilers.

2. Water-tube Boiler

The water-tube boiler has water inside the tubes and flue gas outside. This design is better for high-quality steam and large capacities.

Applicable scenarios:

They are used in industries like electric power, steel, and chemicals. These industries need a lot of steam and high-quality systems.

Advantages:

Adapt to high-pressure operation: They can handle ultra-high pressure and temperature.

Higher thermal efficiency: They have a larger heat exchange area, making them more efficient.

Better steam quality: They produce drier and more stable steam.

Stronger safety: Their design makes them safer, even in case of leaks.

Disadvantages:

Water-tube boilers are more complex. They require more expertise and resources. Their manufacturing and maintenance costs are higher.

Methods of Heat Application

The heart of a steam boiler's efficiency is its internal heat transfer system. The heat from the fuel is transferred to water, turning it into steam. This process uses radiation, convection, and conduction heat transfer.

These methods work together in the boiler. They make up the boiler's heat exchange system.

1. Radiation

Radiation heat transfer happens in the boiler's furnace. When fuel burns, it creates a high-temperature flame. This flame sends infrared radiation to the furnace walls and water pipes.

This heat transfer is fast and efficient. It's the main heat source in the boiler's initial heating.

2. Convection

Convection heat transfer occurs in the boiler's back and flue system. The temperature difference between the flue gas and heating surfaces transfers heat to water or steam. This happens in areas like convection tube bundles and economizers.

Convection is crucial for improving the boiler's thermal efficiency. Its efficiency depends on flue gas velocity, temperature difference, and surface area.

3.Conduction

Conductive heat transfer happens in the boiler's heated structure. Heat moves from the high-temperature flue gas to the low-temperature water or steam through metal pipe walls and furnace linings. Although slower than radiation and convection, it's essential for heat transfer inside the boiler.

How Steam Boilers Operate？

Steam boiler operation involves start-up, operation, and shutdown. Each step must follow strict specifications for safe, efficient, and stable operation. This includes start-up, shutdown, safety measures, daily maintenance, and efficiency.

1. Start the program

Starting the boiler requires caution. Temperatures and pressures should be raised gradually to prevent accidents.

Check the water level and fuel supply: Ensure the water level is safe and fuel supply is stable.

Power on and check the control system: Verify the automatic control system is working. Check sensors, alarms, and actuators.

Start the blower and ignite: Ensure enough air for combustion and ignite safely.

Slow heating and gradual pressurization: Control heating rates to avoid metal stress.

Switch to automatic operation after reaching the operation parameters: After stability, switch to automatic control for normal operation.

2. Shutdown procedure

Shutting down a boiler should be done step by step to keep equipment safe:

Turn off the burner and stop the oil/gas supply: stop the fuel supply and stop the flame.

Slowly reduce pressure and temperature: prevent structural stress caused by quenching and keep the system stable and cool.

Removal of residual steam: the residual steam in the system is discharged through the steam exhaust valve to prevent the condensed water from corroding the equipment.

Check whether all indicators of the system are normal: confirm that all parameters have returned to the safe range.

Carry out regular sewage discharge: discharge the sediments and impurities in the pot to keep the water clean.

3. Safety measures

Boilers are high-temperature and high-pressure equipment. They need a perfect safety system for safe operation:

Check the safety valve, pressure gauge and water level gauge regularly: ensure that all safety devices are accurate and sensitive and meet the requirements of laws and regulations.

Set automatic alarm and shutdown device for overpressure and overtemperature: automatically alarm and stop the furnace when the pressure or temperature is abnormal to prevent accidents.

Prevent dry burning and low water level: configure low water level alarm and protection device to prevent equipment damage or explosion caused by water shortage.

4. Maintenance inspection

A scientific maintenance system is key to ensuring boilers operate safely for a long time:

Regularly clean the furnace and flue pipe to prevent scaling and dust accumulation: maintain heat exchange efficiency and prolong service life.

Check whether the pipeline and welding parts are leaking: avoid pressure leakage or structural damage.

Maintain the sensitivity of burner and control system: ensure accurate and reliable ignition, flame control and gas proportion adjustment.

5. Efficiency indicators

Boiler efficiency is a key measure of its performance. It includes several important aspects:

Thermal efficiency: the thermal efficiency of high-quality steam boilers should be more than 85%, and some high-end boilers can reach more than 90%.

Reasonable smoke exhaust temperature control: control the smoke exhaust temperature within a reasonable range (usually 150 ~ 250 C) to prevent waste of heat energy.

Full combustion, no black smoke: Good combustion condition means proper air volume and good atomization, and there is no obvious black smoke emission from the chimney.

Steam Boilers vs. Furnaces

"Steam boiler" and "furnace" are often mentioned together in thermal energy systems. However, they are different in function and structure. Understanding their relationship is crucial for improving boiler design and operation efficiency.

1. Main differences

A steam boiler is a complete heating system. It includes combustion, heat exchange, steam storage, and control. It is used in various fields like industry, energy, and heating. On the other hand, a furnace is just a core part of the boiler system. Its main role is to provide a space for fuel combustion and transfer heat to the heating surface.

In simple terms, a boiler is like a "steam-making machine", and the furnace is its "heat source heart". Although the furnace is just a part of the boiler, its design and operation state greatly affect the boiler's thermal efficiency and emission performance.

2. Comparison of advantages and disadvantages

Conclusion

The steam boiler is crucial for industrial thermal systems. It affects energy use, production, and the environment. Knowing how it works and its furnace's role is essential for picking and running an efficient system.

EPCB steam boilers have special furnace designs and advanced burning tech. They also have smart safety systems for top thermal efficiency and safe use. EPCB aims to help industries save energy and cut emissions, making steam generation smarter and greener.