Fluid Bed Calciner for Lime Mud CO2 Recovery
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Solution Overview
Problem
The rotary kiln/LMD calcination process in Kraft paper pulp mills is energy-intensive and inefficient, relying on high-cost fossil fuels, and struggles to utilize low-cost biomass and waste fuels due to ash contamination and heat transfer fouling issues, limiting the ability to reduce fossil fuel consumption and improve energy efficiency.
Innovation Solution
A method involving a bubbling fluid bed calciner thermally linked by moving media heat transfer (MMHT) to a circulating fluid bed combustor, allowing the use of low-cost fuels like biomass and WWTP sludge, separating combustion and calcination stages to recover excess energy as superheated steam, and producing high-purity CO2 and calcined lime mud.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If rotary kiln/LMD calcination process is used, then calcination can be performed, but energy consumption is high and fossil fuel dependency increases
Solution Approach 1:
The invention separates the calcination process into two distinct stages: a drying stage using waste heat from combustor off-gases, and a calcination stage using a fluidized bed calciner. This segmentation allows each stage to be optimized independently, with the drying stage utilizing low-grade heat and the calcination stage using high-temperature combustion, thereby reducing overall energy consumption and fossil fuel dependency
Solution Approach 2:
The invention introduces a fluidized bed dryer as an intermediary component between the combustor and calciner. This dryer uses waste heat from combustor off-gases to pre-dry lime mud before it enters the calciner, reducing the energy required for calcination and allowing the use of lower-cost fuels with higher moisture content
2Ease of manufacture
If low-cost biomass and waste fuels are used, then fuel cost decreases, but ash contamination and heat transfer fouling occur
Solution Approach 1:
The invention separates fuel combustion from lime mud calcination into distinct units (combustor and calciner). The combustor burns biomass and waste fuels to generate heat and off-gases, while the calciner uses these off-gases to dry and calcine the lime mud. This segmentation prevents ash from fuel combustion from contaminating the lime mud product, enabling the use of low-cost biomass and waste fuels without quality degradation
Solution Approach 2:
The fluidized bed dryer acts as an intermediary that receives hot off-gases from the combustor and uses them to dry lime mud. This intermediary system transfers heat without direct contact between fuel ash and lime mud, preventing contamination while maintaining heat transfer efficiency and avoiding fouling issues
3Device complexity
If combustion and calcination are combined in one unit, then process complexity is reduced, but heat transfer fouling and energy efficiency decrease
Solution Approach 1:
The invention divides the thermal processing into separate combustor and calciner units, allowing the combustor to operate at high temperatures for efficient fuel combustion, while the calciner operates at lower temperatures suitable for lime mud calcination. This segmentation prevents heat transfer fouling that would occur in a combined unit and improves overall energy efficiency by optimizing each stage for its specific function
Solution Approach 2:
The invention creates a continuous heat recovery loop where off-gases from the combustor are used to dry lime mud in the fluidized bed dryer, and then these same off-gases are used to provide heat for the calciner. This continuous utilization of thermal energy minimizes energy losses and improves overall process efficiency
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 energy efficiency, reduces fossil fuel consumption, and produces high-quality CO2 and calcined lime mud, while avoiding ash contamination and heat transfer fouling, thereby improving operational efficiency and reducing costs.
Implementation Method 1
calcining calcium carbonate lime mud and converting said calcium carbonate lime mud to carbon dioxide and calcined lime mud
Implementation Method 2
thermally linked by moving media heat transfer (MMHT) to a circulating fluid bed combustor wherein the moving media heat transfer provides heat input for calcining the lime mud
Implementation Method 3
circulating fluid bed combustor wherein the moving media heat transfer provides heat input for calcining the lime mud
Implementation Method 4
separating said carbon dioxide from said steam by condensing the steam
Data Source
AI summary
Methods and systems are described for recovering carbon dioxide, for producing commercial quality carbon dioxide (CO2) of 90% to +99% purity using, wet calcium carbonate lime mud produced in a recausticizing process that also produces caustic soda, for instance, Kraft paper pulp mill lime mud (a.k.a., “lime mud”) as a feedstock to a multi-stage lime mud calcination process. High reactivity, high-quality calcined lime mud (a.k.a. re-burned lime, or calcine), required in the Kraft paper pulp mill's recausticizing process is also produced, and superheated high pressure steam and hot boiler feed-water is generated and exported to the mill's steam distribution and generation system as well as hot process water for use in the mill's manufacturing operation. The system for calcining calcium carbonate lime mud produced from a recausticizing manufacturing operation and converting it to calcined lime mud and CO2 comprises a calciner and a combustor linked by a moving media heat transfer (MMHT) system or apparatus. The MMHT system or apparatus thermally links separate fluid bed combustion (exothermic) and calcination (endothermic) stages with a solid particulate media. The system further comprises a flash dryer or spray dryer that utilizes exhausted enthalpy from the calcination stage.