Rotary Kiln Ring Formation Mitigation via Magnesium Additive

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Solution Overview

Problem

Pyro-metallurgical processes in rotary kilns are prone to kiln ring formation, leading to reduced production capacity and frequent shutdowns for cleaning, with existing methods like shotgun blasting and thermal shedding causing damage and inefficiencies.

Innovation Solution

Incorporating a magnesium-based additive in the rotary kiln at 0.5-9.5 wt.% of the total raw materials weight to counteract kiln ring formation, allowing rings to shed under their own weight and facilitating easier online cleaning, while reducing waste and impurities.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If shotgun blasting is used to remove kiln rings, then cleaning effectiveness is improved, but damage to refractory walls and kiln hot spots increase

Engineering Contradiction:

Improvekiln ring cleaning effectivenessVSAvoiddamage to refractory walls

Core Design Contradiction:

Ease of operationVSObject-affected harmful factors

Solution Approach 1:

The patent replaces the mechanical shotgun blasting system with a thermal field system. The burner assembly delivers concentrated thermal energy to the kiln ring, causing it to detach through thermal stress and expansion rather than mechanical impact. This substitution eliminates damage to refractory walls while maintaining cleaning effectiveness.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent uses a burner assembly that provides intense thermal energy (combustion process) to rapidly heat the kiln ring. This accelerated thermal process causes the kiln ring to expand and detach from the wall through thermal stress, replacing the need for mechanical blasting while avoiding damage to the kiln structure.

Inventive Principle:

Principle #38Strong oxidants (Accelerated oxidation)

2Ease of operation

If thermal shedding is used to remove kiln rings, then cleaning is achieved through temperature reduction, but damage to refractory brick and degradation of kiln centricity occur

Engineering Contradiction:

Improvekiln ring removal capabilityVSAvoiddamage to refractory brick

Core Design Contradiction:

Ease of operationVSObject-affected harmful factors

Solution Approach 1:

Instead of using thermal shedding (rapid cooling) to remove kiln rings, the patent inverts the approach by using rapid heating. The burner assembly delivers intense thermal energy to the kiln ring, causing it to expand and detach through thermal stress. This inverted thermal approach achieves ring removal without the damaging effects of rapid cooling on refractory brick.

Inventive Principle:

Principle #13The other way round (Inversion)

3Reliability

If periodic shutdown operations are performed to clean kiln rings, then production capacity is maintained, but lost production time increases

Engineering Contradiction:

Improveproduction continuityVSAvoidproduction time

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent enables continuous operation by allowing online cleaning of kiln rings without shutdown. The burner assembly can be activated to remove kiln rings while the kiln remains operational, maintaining continuous production flow. This eliminates the periodic interruptions required by traditional cleaning methods, thereby increasing productivity while maintaining reliability.

Inventive Principle:

Principle #20Continuity of useful action

4Use of energy by stationary object

If accumulation of particles on inner wall occurs, then heat transfer efficiency decreases, but production capacity is reduced

Engineering Contradiction:

Improveheat transfer efficiencyVSAvoidproduction capacity

Core Design Contradiction:

Use of energy by stationary objectVSProductivity

Solution Approach 1:

The patent applies preliminary action by proactively removing kiln rings before they significantly accumulate and impede heat transfer. The online cleaning capability allows periodic thermal shedding of rings during normal operation, preventing the buildup that would otherwise reduce heat transfer efficiency and production capacity.

Inventive Principle:

Principle #10Preliminary action

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 approach extends production campaign duration, reduces shutdowns, and makes kiln rings more susceptible to cleaning, with the resulting solid product being suitable for valorization in applications like road construction without extensive purification.

Implementation Method 1

said raw material is heated to produce a volatized material... which magnesium-based additive is heated together with said raw material

Methodology Applied

Scientific EffectHeating: Heating

Implementation Method 2

said raw material is heated to produce a volatized material

Methodology Applied

Scientific EffectVolatilization: Evaporation

Data Source

PatentUS12018345B2Pyro-metallurgical process in a rotary kiln

Publication Date: 2024.06.25 LHOIST RECH & DEV SA

AI summary

A pyro-metallurgical process for producing a non-ferrous metal or a compound thereof, wherein a metal raw material is fed into a rotary kiln, the metal being one of arsenic (As), antimony (Sb), lead (Pb), cadmium (Cd), mercury (Hg), silver (Ag), tin (Sn), nickel (Ni), or zinc (Zn). The raw material is heated to produce a volatized material, in which the non-ferrous metal or compound thereof is produced from the volatized material. A magnesium-based additive is additionally fed to the rotary kiln in an amount of between 0.5 wt. % and 9.5 wt. % relative to the total weight of the raw material. The magnesium-based additive is heated together with the raw material to produce the volatized material and a solid product while also counteracting ring formation in the rotary kiln.