Blast Furnace Stack: Exhaust Component for Gas Venting

Product Specifications

Technical details and manufacturing context for Stack

Definition

In a blast furnace structure, the stack is the tall, cylindrical component that serves as the primary exhaust and ventilation system. It is positioned above the furnace proper and is responsible for safely venting the high-temperature gases (primarily carbon monoxide, carbon dioxide, and nitrogen) produced during the smelting process, along with fine dust and particulates (flue dust). Its design is critical for maintaining proper furnace pressure, ensuring efficient combustion, and directing emissions to gas cleaning systems. The stack is typically constructed from refractory-lined steel, with the refractory protecting the steel shell from high temperatures and corrosive gases. Key design parameters include height (typically 30–120 m), inner diameter (2–8 m), wall thickness (12–40 mm), and operating temperature (200–400°C, with peak surges up to 500°C). Operating pressure is usually negative (draft) in the range of -0.5 to 0.5 kPa. Material grades for structural parts are commonly Q235B or Q345R, referencing GB/T 700 and GB/T 1591 standards. Corrosion allowance is typically 2–6 mm, based on flue gas composition. Design must account for wind load (0.5–1.5 kN/m² per GB 50009) and seismic intensity (6–9 degrees per GB 50011). The total weight, including lining and platforms, ranges from 50 to 500 tonnes. With proper maintenance, the expected service life is 20–30 years. These values are reference ranges; actual specifications must be confirmed with the legal manufacturer or supplier for specific applications. The stack's height creates natural draft (chimney effect), aiding gas flow. Gases exit the top and are often directed to downstream equipment for heat recovery and gas cleaning before release or reuse.

Working Principle

Hot gases and flue dust, generated from the combustion of coke and chemical reactions in the furnace hearth and bosh, rise due to convection and pressure differentials. The stack provides a controlled, vertical pathway for this gas stream. Its height creates natural draft (chimney effect), aiding in gas flow. The gases exit the top of the stack, often directed to downstream equipment for heat recovery (in stoves) and gas cleaning before release or reuse.

Common Materials

Refractory Lined Steel

Technical Parameters

Parameter	Typical range	Notes & selection driver
Height	30–120 m	Determines draft and dispersion of flue gases.
Inner Diameter	2–8 m	Affects gas velocity and pressure drop.
Wall Thickness	12–40 mm	Structural integrity and corrosion allowance.
Operating Temperature	200–400 °C	Peak surges up to 500°C.
Operating Pressure	-0.5–0.5 kPa	Negative pressure (draft) typical.
Material Grade	Q235B/Q345R	Carbon steel for structural parts.GB/T 700, GB/T 1591
Corrosion Allowance	2–6 mm	Based on flue gas composition.
Wind Load	0.5–1.5 kN/m²	Design per local wind zone.GB 50009
Seismic Intensity	6–9 degree	Higher intensity requires reinforced design.GB 50011
Weight	50–500 t	Includes lining and platforms.
Service Life	20–30 years	With proper maintenance.

Ranges are indicative industry figures for RFQ preparation, not a supplier commitment. Confirm every value and standard with the legal manufacturer before ordering.

Components / BOM

Refractory Lining Part
Protects the steel shell from extreme heat and chemical corrosion of the hot gases and abrasion from particulates.

Material: Fireclay, High-Alumina, or Silicon Carbide Refractories
Steel Shell/Casing Part
Provides the primary structural support and containment for the stack and its refractory lining.

Material: Carbon Steel or Low-Alloy Steel Plate
Gas Offtake
The opening or duct at the top of the stack where gases exit to the downcomer and gas cleaning system.

Material: Refractory Lined Steel

Applied To / Applications

This component is essential for the following industrial systems and equipment:

Blast Furnace Structure

View system integration details

Manufacturers of Stack

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Frequently Asked Questions

What is the primary function of a blast furnace stack?

The stack is the vertical exhaust structure that safely vents hot waste gases and particulates from the blast furnace, maintaining proper furnace pressure and directing emissions to cleaning systems.

What materials are typically used for the stack?

The stack is typically made of refractory-lined steel. The refractory protects the steel shell from high temperatures and corrosive gases. Structural parts often use carbon steel grades like Q235B or Q345R, per GB/T 700 and GB/T 1591.

What are typical height and diameter ranges for a stack?

Typical height ranges from 30 to 120 meters, and inner diameter from 2 to 8 meters. These values are reference ranges and must be confirmed for specific applications.

How does the stack affect furnace operation?

The stack's height creates natural draft, aiding gas flow. It also affects furnace pressure and combustion efficiency. Proper design is critical for safe and efficient operation.

Data Basis

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Preliminary Technical Classification

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pressure:	Near atmospheric (0-5 kPa gauge), negative pressure to prevent gas escape
flow rate:	50-500 m³/s depending on furnace size
temperature:	200-500°C (typical), up to 700°C with refractory lining
slurry concentration:	Not applicable - handles dry particulates and gases only

Stack

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