Oxyfuel Clinker Production Without Preheater Exhaust Recirculation
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Solution Overview
Problem
Existing cement clinker production processes rely on recirculation of preheater exhaust gases, which limits process efficiency and increases costs, necessitating improved methods that eliminate or reduce this recirculation for better economic and ecological performance.
Innovation Solution
A rotary furnace plant and process using an oxygen-containing gas with a high oxygen content (50% or more) and low nitrogen (15% or less) are introduced into the calciner and rotary tube furnace, eliminating the need for preheater exhaust gas recirculation, and featuring a cyclone preheater with a multistage cascade and a calciner with a higher solid-to-gas ratio, which allows for increased heat conversion and reduced plant size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If preheater exhaust gases are recirculated into the calciner, then process temperatures and volume flows remain stable compared to prior art, but plant size increases, heat losses increase, and economic and ecological performance deteriorates
Solution Approach 1:
The invention extracts and eliminates the recirculation of preheater exhaust gases from the process. By using pure oxygen instead of air in the calciner, the exhaust gas composition changes fundamentally, allowing the preheater exhaust to be discharged without recirculation while maintaining stable process temperatures through direct oxygen combustion control.
Solution Approach 2:
The invention changes the fundamental parameter of combustion air composition by using pure oxygen (100% O2) instead of atmospheric air (21% O2, 79% N2). This parameter change transforms the exhaust gas composition to contain minimal nitrogen, eliminating the need for recirculation and reducing heat losses while maintaining temperature stability through controlled oxygen injection rates.
2Quantity of substance
If preheater exhaust gases are recirculated, then volume flows and process conditions remain comparable to prior art, but device complexity and plant size increase
Solution Approach 1:
The invention removes the recirculation loop entirely from the process design. By injecting pure oxygen directly into the calciner and controlling the oxygen-to-fuel ratio, the system achieves stable volume flows without requiring complex recirculation piping, valves, and control systems that would be needed to manage exhaust gas recycling.
Solution Approach 2:
The system uses the heat and energy already present in the clinker cooler and preheater to maintain process temperatures without requiring recirculation. The pure oxygen combustion process generates sufficient heat in-situ, making the system self-sufficient and eliminating the need for external recirculation infrastructure.
3Stability of the object's composition
If recirculation of preheater exhaust gases is implemented, then process stability is maintained, but manufacturing costs and operational expenses increase
Solution Approach 1:
The invention extracts the recirculation requirement from the process design, eliminating capital costs for recirculation equipment and operational costs for pumping and reheating exhaust gases. Process stability is maintained through precise control of pure oxygen injection rates and fuel combustion ratios, which are simpler and more direct than recirculation control systems.
Solution Approach 2:
By changing from air-based combustion to pure oxygen combustion, the invention fundamentally alters the thermodynamic parameters of the process. This parameter change improves combustion efficiency and heat transfer, reducing energy costs and operational expenses while maintaining process stability through controlled oxygen feed rates.
4Temperature
If air is used in the calciner instead of pure oxygen, then nitrogen is present in exhaust gas facilitating heat distribution, but CO2 separation becomes more difficult and pollutant emissions increase
Solution Approach 1:
The invention replaces the nitrogen-rich atmospheric air environment with a pure oxygen environment in the calciner. This creates an inert atmosphere regarding nitrogen oxides formation, eliminating NOx emissions from combustion. The heat distribution function previously provided by nitrogen is replaced by controlled oxygen combustion and heat transfer through the clinker bed and preheater system.
Solution Approach 2:
By using pure oxygen instead of atmospheric air, the invention applies a strong oxidant that accelerates combustion efficiency and completeness. This reduces unburned hydrocarbons and carbon monoxide emissions while improving heat transfer efficiency. The accelerated oxidation process maintains temperature distribution through more efficient combustion heat release.
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 enables a more efficient and cost-effective cement clinker production by reducing plant size, minimizing heat losses, and enhancing thermal energy efficiency, while also simplifying CO2 purification and reducing pollutant emissions.
Implementation Method 1
an oxygen-containing gas having a proportion of 15% by volume or less of nitrogen and a proportion of 50% by volume or more of oxygen is fed into the calciner and optionally also into the rotary tube furnace
Implementation Method 2
cyclone preheaters, whose individual cyclones are connected to one another in a cascade-like manner, are used
Implementation Method 3
preheating of the starting material to the calcination temperature
Data Source
AI summary
Processes and plants for producing cement clinker, wherein no recirculation of preheater exhaust gases occurs and the ratio of solid fed in to exhaust gas in the preheater is set to greater than 1.0 kg of solid to gas.