Entrained-Flow Calcinator Placement for Cement Heat Recovery
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Solution Overview
Problem
Conventional cement clinker production plants face limitations in energy balance for electrical energy generation, leading to excessive nitrous gases (NOx) and reduced cement quality due to high energy load and inefficient waste heat utilization.
Innovation Solution
Reversing the precalcination and preheating sequence by placing the co-current flow calciner before the heat exchanger and combining cooler exhaust air to enhance heat recovery for electrical energy generation, while maintaining the quality of cement clinker and reducing NOx formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If heat is extracted from the production process for electrical energy generation, then electrical energy production increases, but the energy balance becomes skewed and NOx control becomes difficult
Solution Approach 1:
The patent segments the heat extraction process by providing multiple heat exchangers at different locations (outlet of rotary kiln, outlet of calciner, outlet of preheater) to extract heat at various stages. This segmentation allows optimization of heat recovery while maintaining process stability and controlling NOx formation by distributing the energy extraction load across multiple points rather than concentrating it at one location.
2Power
If conventional heat extraction points are used, then process stability is maintained, but electrical energy generation is limited
Solution Approach 1:
The patent implements multi-functionality by enabling the cement production system to simultaneously perform its primary function (cement clinker production) and secondary function (electrical energy generation) through multiple heat exchangers. The system can extract heat at three different locations (rotary kiln outlet, calciner outlet, preheater outlet), making it universally adaptable to maximize energy recovery while maintaining reliable cement production.
3Loss of energy
If cooler exhaust air is returned to the process at high temperature, then heat recovery efficiency is high, but the temperature of usable exhaust air is limited
Solution Approach 1:
The patent adds a spatial dimension to heat recovery by utilizing multiple locations along the production process (rotary kiln outlet, calciner outlet, preheater outlet) rather than relying solely on cooler exhaust air temperature. This multi-dimensional approach allows heat extraction at different temperature levels and locations, overcoming the limitation of single-point heat recovery and enabling comprehensive energy utilization.
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 allows for a higher energy balance in favor of electrical energy production without compromising cement quality, reducing NOx emissions, and optimizing heat utilization across multiple points in the system.
Implementation Method 1
at least one flow-through calciner for pre-calcining (deacidifying) raw meal... allowing all the cooler exhaust air to be directed into the base of a flow-through calciner
Implementation Method 2
at least one heat exchanger downstream of the rotary kiln in the direction of gas flow for recuperating process heat from the at least one rotary kiln
Implementation Method 3
at least one clinker cooler downstream of the rotary kiln in the direction of material flow for cooling the sintered cement clinker
Implementation Method 4
at least one rotary kiln for sintering the cement clinker from pre-calcined raw meal
Implementation Method 5
the conversion of the carbonate-containing material in the form of calcium carbonate (CaCO3) into quicklime (CaO), which consists essentially of calcium oxide (CaO), through heat treatment. During this deacidification process, calcium carbonate (CaCO3) is converted into calcium oxide (CaO) with the release of carbon dioxide (CO2)
Data Source
Figure 1
Figure 2
AI summary
The invention relates to a system (100, 200) for producing cement clinker, having at least one rotary kiln (113) for sintering the cement clinker from pre-calcinated raw meal (101), at least one heat exchanger (112) which is connected downstream of the rotary kiln (113) in the gas flow direction for recuperating process heat from the at least one rotary kiln (113), at least one entrained flow calcinator (102) for pre-calcinating (deacidifying) the raw meal (101), and at least one clinker cooler (105) which is connected downstream of the rotary kiln (113) in the material flow direction for cooling the sintered cement clinker, wherein a line is provided for conducting the cooler exhaust air (104) for recuperating heat into the system (100, 200). According to the invention, the entrained-flow calcinator (102) is arranged upstream of the heat exchanger (112) in the material flow direction. The aforementioned assembly allows the system to be operated with high excess heat which can be coupled out in order to generate electric energy.