Pre-oxidized Ilmenite in Fluidized Bed Boiler Startup

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Solution Overview

Problem

The use of ilmenite particles in fluidized bed boilers can lead to sudden and drastic temperature increases during startup, causing damage to the furnace and nozzles due to rapid exothermal oxidation, which is not effectively managed by existing technologies.

Innovation Solution

Pre-oxidizing ilmenite particles before use in fluidized bed boilers to control the initial oxidation reaction and prevent excessive temperature increases, allowing for safe startup and operation by providing pre-oxidized ilmenite particles or gradually oxidizing fresh ilmenite particles within the boiler.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If fresh ilmenite particles are used in fluidized bed boilers, then the bed material can be utilized as an oxygen carrier and allow operation at lower air to fuel ratios, but sudden and drastic temperature increases occur during startup due to rapid exothermal oxidation

Engineering Contradiction:

Improveair to fuel ratioVSAvoidtemperature increase during startup

Core Design Contradiction:

Use of energy by moving objectVSTemperature

Solution Approach 1:

The patent applies preliminary action by pre-oxidizing ilmenite particles in a separate step before introducing them to the fluidized bed boiler. This preliminary oxidation converts fresh ilmenite into pre-oxidized ilmenite with reduced exothermic potential, thereby preventing sudden temperature increases during boiler startup while still allowing the material to function as an oxygen carrier during normal operation

Inventive Principle:

Principle #10Preliminary action

2Adaptability or versatility

If fresh ilmenite particles are used in fluidized bed boilers, then the reducing-oxidizing feature allows repeated oxidation and reduction cycles, but rapid exothermal oxidation causes damage to the furnace and nozzles

Engineering Contradiction:

Improvereducing-oxidizing capabilityVSAvoiddamage to furnace and nozzles

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies preliminary action by pre-oxidizing ilmenite particles before they are introduced to the fluidized bed boiler. This preliminary oxidation step reduces the exothermic potential of the ilmenite, thereby preventing rapid temperature increases that would cause damage to the furnace and nozzles, while preserving the material's ability to undergo repeated oxidation-reduction cycles during normal operation

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent applies preliminary anti-action by performing a controlled oxidation process on fresh ilmenite particles before they enter the boiler system. This pre-oxidation creates a state of reduced exothermic reactivity, effectively counteracting the harmful rapid oxidation that would otherwise occur during startup and cause thermal damage to equipment

Inventive Principle:

Principle #9Preliminary anti-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

Pre-oxidizing ilmenite particles prevents severe temperature fluctuations, enabling controlled startup and operation of fluidized bed boilers, reducing the risk of damage and ensuring stable combustion conditions.

Implementation Method 1

The natural occurring mineral ilmenite consists mainly of iron titanium oxide (FeTiO3) which can be repeatedly oxidized and reduced

Methodology Applied

Scientific EffectOxidation: Oxidation

Implementation Method 2

sudden and drastic temperature increases during startup, causing damage to the furnace and nozzles due to rapid exothermal oxidation

Methodology Applied

Scientific EffectExothermal oxidation: Exothermic Reaction

Implementation Method 3

Once the velocity of the fluidization gas rises above the minimum fluidization velocity at which the force of the fluidization gas balances the gravity force acting on the particles, the solid bed material behaves in many ways similar to a fluid and the bed is said to be fluidized

Methodology Applied

Scientific EffectFluidization: Fluidisation

Implementation Method 4

Usually oxygen containing gas, typically air, is used as the fluidizing gas (so called primary fluidizing gas or primary air) and passed from below the bed through the bed material, thereby acting as a source of oxygen required for combustion

Methodology Applied

Scientific EffectCombustion: Combustion

Data Source

PatentUS11414725B2Use of pre-oxidized ilmenite in fluidized bed boilers

Publication Date: 2022.08.16 IMPROBED AB

AI summary

The invention relates to a method for starting up a fluidized bed boiler, such as a circulating fluidized bed (CFB) or a bubbling fluidized bed (BFB) boiler, for operation with a predetermined concentration of ilmenite particles in the bed material. The invention also relates to a method for pre-oxidizing ilmenite, to pre-oxidized ilmenite and to the use of pre-oxidized ilmenite in a fluidized bed boiler.