Bypass Gas Recirculation in Cement Clinker Production
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Solution Overview
Problem
Existing methods for reducing pollutants in cement clinker production, such as diverting kiln exhaust gases through a bypass line, often limit kiln performance and reduce clinker output due to preheater size constraints and inefficient gas handling.
Innovation Solution
A system that recirculates dedusted bypass gases from the kiln exhaust back into the calciner or tertiary air line, allowing them to be used as combustion air, thereby maintaining kiln performance and clinker output while reducing pollutant emissions, without significant heat consumption changes or additional NOx reduction systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If part of the kiln exhaust gases is removed via bypass line and cleaned, then pollutant emissions are reduced, but the clinker output of the kiln plant is reduced
Solution Approach 1:
The patent recovers the thermal energy from the bypass gas that would otherwise be wasted. The cooled bypass gas is used to preheat the raw meal in the preheater, recovering its heat value and utilizing it for the calcination process, thereby converting a waste stream into a useful resource
Solution Approach 2:
The bypass gas serves multiple functions: it is first used to cool the preheater sections, then the cooled gas is utilized as combustion air in the calciner. This multi-functional utilization maximizes the value extracted from the bypass stream while minimizing waste
2Object-generated harmful factors
If a denitrification device is arranged after the preheater for denitrification of bypass gases, then NOx reduction is achieved, but the device complexity increases
Solution Approach 1:
The patent merges the denitrification function into the existing preheater structure by arranging denitrification devices in the preheater sections. This integration eliminates the need for separate denitrification equipment and allows the preheater to serve dual purposes: cooling the bypass gas and performing NOx reduction
Solution Approach 2:
The preheater is given multiple functions: it cools the bypass gas, preheats the raw meal, and performs denitrification of the bypass gases. This multi-functionality reduces the need for additional dedicated equipment for each function
3Ease of operation
If the kiln exhaust gases are reduced to fit the preheater capacity, then the preheater can handle the gas flow, but the clinker output of the kiln plant is reduced
Solution Approach 1:
Instead of reducing or discarding the bypass gas flow, the patent recovers its thermal energy to preheat the raw meal. This allows the preheater to handle the full kiln exhaust gas flow while maintaining efficient heat transfer, thereby preserving clinker output
Solution Approach 2:
The patent changes the temperature parameter of the bypass gas by cooling it in the preheater sections before it enters the calciner. This temperature reduction allows the gas to be effectively utilized for preheating raw meal while maintaining suitable conditions for subsequent combustion
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 substantial unchanged clinker output while reducing pollutant emissions, utilizing existing NOx reduction systems, and improving heat balance through heat recovery, without the need for separate NOx reduction of bypass gases.
Implementation Method 1
the bypass gas is cooled in the cooling device by supplying air, as a result of which the gaseous pollutants in the bypass gas condense on the dust carried along
Implementation Method 2
a preheater for preheating cement raw material into preheated raw cement meal
Implementation Method 3
a calciner for calcining the preheated raw cement meal into calcined raw cement meal
Implementation Method 4
a kiln for finish-burning the calcined raw cement meal into cement clinker
Data Source
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AI summary
A bypass system is used in the system and method for producing cement clinker, wherein a portion of a furnace exhaust gas occurring in a furnace is channeled off as a bypass gas via a bypass line connected between the furnace and a calciner, cooled and dedusted. The dedusted bypass gas is then directed back to the calciner and/or into a tertiary air duct arranged between the cooling means and the calciner and/or into a region between the furnace and the calciner.