Chain Grate Steam Boiler

High-Efficiency Energy Generation

INTRODUCTION

Chain-grate steam boilers are crucial for industries that need steam for production or electricity generation. They harness heat from combusted fuels—such as coal, firewood, rice husk, and biomass—to heat water and convert it into steam at various pressures and temperatures based on specific requirements. These boilers are typically classified into energy, industrial, and civil boilers, each designed for particular operational purposes.

Among various combustion chamber designs, the chain-grate boiler stands out due to its high level of automation. It features a continuously moving chain grate, ensuring efficient combustion. The chain-grate boiler can achieve a maximum capacity of 40 MW and produce up to 120 tons of steam per hour.

SPECIFICATION

Calculation & Design: according to ASME and TCVN

Fabrication: According to ASME and TCVN

Evaporation Capacity : (10,000-200,000) kg/h

Design Pressure : ( 10-100) bar(g)

Fuel: Indonesia coal & Biomass

Boiler Efficiency: 87%

Steam Quality: Saturated or Superheated

CHAIN GRATE STEAM BOILER LAYOUT

Chain Grate Steam Boiler

STRUCTURE AND OPERATION PRINCIPLE

1. Fuel supply system to the furnace:

The fuel supply system includes equipment such as excavators, fuel hoppers, conveyors, and screws. These devices work together to control and automate fuel feeding into the boiler. A weight scale is also included to monitor fuel consumption accurately, ensuring optimal operation.

2. Chain Grate – Combustion Chamber

The feed hopper, positioned outside the combustion chamber, uses gravity to distribute fuel evenly onto the chain grate. The chain grate moves the fuel through the combustion chamber, where it burns progressively. This continuous movement of the grate ensures the fuel burns efficiently.

As combustion occurs, chemical reactions between the fuel elements (carbon, hydrogen, oxygen, nitrogen, and sulfur) and oxygen from the air generate heat. This heat is absorbed by the steam-generating tubes surrounding the combustion chamber. The heated water inside these tubes eventually turns into steam, which is then sent to the steam drum.

Once steam is generated, it is separated from any residual water in the steam drum. The un-evaporated water returns to the steam generator tubes via downpipes, initiating a natural circulation process. When the boiler operates at high pressure, a circulation pump may be used to support water movement. The steam produced is initially saturated, and if superheated steam is required, it passes through a superheater to increase its temperature.

Chain burner

Chained Boiler Body

3. Air and Water Recovery System

The exhaust gases from combustion still carry significant heat after passing through the convection tubes. To maximize energy efficiency, this heat is recovered using a feedwater heater and air dryer system. The feedwater heater pre-heats the water before it enters the boiler, reducing energy waste.

Chain Grate Steam Boiler

Boiler Degassing Water Tank

The air dryer utilizes the heat from the exhaust gases to preheat the incoming air, ensuring it enters the combustion chamber at the optimal temperature. This process also helps prevent chimney corrosion caused by condensation of harmful gases like SO2 and NOx.

Chain grate boiler water and wind recovery unit

4. Dust filtering system:

To meet environmental standards, a dust filtering system is essential. The system may include a bag dust filter, electrostatic precipitator, or wet filter tower. These devices remove dust particles from exhaust gases, ensuring that the smoke released into the atmosphere complies with environmental regulations.

5. Exhaust fan and chimney:

The exhaust fan plays a crucial role in maintaining the pressure inside the combustion chamber. It ensures a consistent negative pressure to prevent dangerous accidents, while also drawing exhaust gases through the system and releasing them into the chimney. The chimney then discharges the filtered smoke into the environment.