Lime Mud Bed Material in Fluidized Bed Gasifier
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Solution Overview
Problem
Conventional lime kiln operations face issues with fouling and reduced capacity due to the use of bed materials like dolomite or sand in circulating fluidized bed gasifiers, which contaminate the end product and require excessive fuel gas for biomass gasification.
Innovation Solution
Employing lime mud as bed material in a circulating fluidized bed gasifier, where a portion is calcined and used to produce fuel gas, reducing fouling and increasing kiln capacity by using bio-based fuels like bark, wood chips, or peat.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dolomite or sand is used as bed material in the gasifier, then the gasifier can operate effectively, but the bed material flies to the lime kiln and causes fouling of lime mud and end product
Solution Approach 1:
The harmful bed material (dolomite or sand) is extracted and removed from the system by using lime mud instead. Lime mud is taken from the chemical circulation after causticization and used as bed material in the gasifier, preventing fouling of the end product while maintaining gasifier operation.
Solution Approach 2:
Lime mud that would otherwise be discarded or require separate treatment is recovered and reused as bed material in the gasifier. This transforms a waste stream into a functional component, eliminating the need for external bed materials that cause fouling.
2Power
If a circulating fluidized bed gasifier is used for gasifying biomass, then fuel gas can be produced, but a great amount of gas is needed because the thermal value of the product gas is small
Solution Approach 1:
The gasifier and lime kiln operations are merged into a combined system. Lime mud is fed to the gasifier where it is partially calcinated and used as bed material, and the resulting product gas is directly utilized in the lime kiln. This integration optimizes the overall process efficiency and reduces the total gas requirement.
Solution Approach 2:
The thermal characteristics of the system are optimized by changing the bed material from conventional materials to lime mud, which has different thermal properties. Lime mud can be partially calcinated in the gasifier, releasing additional energy and improving the thermal value of the product gas.
3Productivity
If the capacity of the lime kiln is increased, then more burnt calcium can be produced, but fouling from bed material and ash reduces the effective capacity
Solution Approach 1:
The lime mud serves multiple functions within the system: it is the feed material for the lime kiln, the bed material for the gasifier, and the source of product gas. This self-service approach eliminates the need for external bed materials that would cause fouling and limit capacity.
Solution Approach 2:
Lime mud is used for multiple purposes: as fuel feedstock for the lime kiln, as bed material in the gasifier, and as a source of calcium for the final product. This multi-functionality maximizes the utilization of the material and eliminates fouling issues associated with conventional bed materials.
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 enhances the purity of burnt calcium oxide by minimizing contamination and increasing the lime kiln's production capacity while utilizing bio-based fuels efficiently.
Implementation Method 1
A part of the lime mud is fed to the gasifier. Thus, lime mud is calcinated partly or entirely and is conveyed with product gas to the lime kiln.
Implementation Method 2
Fuel gas is formed by a circulating fluidized bed gasifier, where a part of the lime mud is used as bed material.
Implementation Method 3
A lime kiln, in turn, is an oven, where lime mud is burnt to calcium oxide, i.e. to burnt calcium (CaO) and carbon dioxide (CO 2 )
Implementation Method 4
Fuel gas is formed by a circulating fluidized bed gasifier, where a part of the lime mud is used as bed material.
Data Source
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AI summary
A method for treating lime mud, in which method the lime mud is conveyed to a lime kiln (1), where fuel gas is used as fuel, which fuel gas is formed by a circulating fluidized bed gasifier (2). A calcium compound is used as bed material in the gasifier (2). In addition, the invention relates to the use of a calcium compound in a lime mud treatment plant, as well as to a lime mud treatment plant.