EAF Scrap Channel Blower Positioning for Off-Gas Preheating

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Solution Overview

Problem

Existing methods for continuous scrap feed into electric arc furnaces face challenges in minimizing false air infiltration and efficiently using off-gases for preheating scrap, leading to high energy consumption and inefficient dust extraction.

Innovation Solution

A single-stage blower with an intake opening oriented towards the smelting furnace, combined with a channel cross section adapted to the scrap size and movable flaps to minimize false air intake, allows for efficient off-gas extraction and preheating of scrap, reducing blower capacity and energy consumption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Length of moving object

If the blower is positioned at the scrap feed area to extract process gases over a long distance, then the extraction distance is increased, but the off-gases are cooled and require additional energy for reheating

Engineering Contradiction:

Improveextraction distanceVSAvoidenergy for reheating off-gases

Core Design Contradiction:

Length of moving objectVSLoss of energy

Solution Approach 1:

The blower position is inverted from the conventional location at the scrap feed area to a location closer to the smelting furnace. This reversal reduces the extraction distance to 1-3 meters, preventing off-gas cooling and eliminating the need for reheating, thereby reducing energy consumption.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The off-gases are extracted immediately after leaving the smelting furnace while still hot, before they have a chance to cool down during transport. This preliminary extraction at high temperature prevents subsequent cooling and the associated energy loss for reheating.

Inventive Principle:

Principle #10Preliminary action

2Object-affected harmful factors

If a second blower is added next to the exhaust with negative pressure control, then false air infiltration is reduced, but control cost and maintenance intensity increase

Engineering Contradiction:

Improvefalse air infiltrationVSAvoidcontrol system complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The problem of false air infiltration is solved by extracting off-gases at their source near the smelting furnace, removing the need for complex negative pressure control systems. The single blower positioned strategically eliminates false air infiltration without requiring additional blowers or sophisticated control mechanisms.

Inventive Principle:

Principle #2Taking out (Extraction)

3Object-affected harmful factors

If flow resistances are increased at the scrap feed inlet, then false air infiltration is reduced, but suction power and process gas extraction efficiency are compromised

Engineering Contradiction:

Improvefalse air infiltrationVSAvoidprocess gas extraction efficiency

Core Design Contradiction:

Object-affected harmful factorsVSProductivity

Solution Approach 1:

Movable flaps are introduced as an intermediary element in the channel to control flow resistance locally. These flaps can be adjusted to optimize the balance between preventing false air infiltration and maintaining efficient process gas extraction, without compromising overall system productivity.

Inventive Principle:

Principle #24Intermediary (Mediator)

4Productivity

If the channel cross section is enlarged to accommodate large scrap pieces, then scrap feeding capability is improved, but false air infiltration increases

Engineering Contradiction:

Improvescrap feeding capabilityVSAvoidfalse air infiltration

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The channel cross section is optimized locally at different positions. Near the smelting furnace where extraction occurs, the cross section is minimized to reduce false air infiltration. Further from the furnace, the cross section can be larger to accommodate scrap feeding requirements, creating different local qualities along the channel length.

Inventive Principle:

Principle #3Local quality

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This solution enables efficient scrap preheating and minimizes false air infiltration, reducing energy costs and environmental impact while effectively preventing dioxins and furans formation.

Implementation Method 1

off-gases from the smelting process which are guided through the channel and which serve to preheat the scrap

Methodology Applied

Scientific EffectHeat transfer: Conduction (thermal)

Data Source

PatentUS9097464B2Continuous scrap supply into an electric arc furnace (EAF)

Publication Date: 2015.08.04 SMS GROUP GMBH

AI summary

A continuous scrap feed into an electric smelting furnace (EAF) having a channel connected at one end to an opening in a wall of the smelting furnace and has at its other end a charging device for the scrap. An extraction device for the off-gases which are guided through the channel serve to preheat the scrap, this extraction device being connected to the channel between the two ends of the channel located closer to the smelting furnace than the scrap feed in relation to the total length of the channel. The extraction device is a single-stage blower whose intake opening is oriented in the direction of the smelting furnace, and the clear cross section of the channel between the extraction device and the scrap feed is adapted to the amount of scrap so that the height of the scrap charge substantially fills the clear cross section.