Regenerative Afterburner SCR Catalyst Temperature Control
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Solution Overview
Problem
Existing regenerative thermal afterburning systems with selective catalytic reduction (SCR) face challenges in maintaining optimal SCR catalyst temperature, mechanical stress, and high energy consumption due to fluctuating temperature profiles and the need for excessive catalyst quantities, which limits the effectiveness in purifying organic components and nitrogen oxides.
Innovation Solution
A method utilizing a thermal afterburning system with at least two regenerators and a common combustion chamber, where exhaust gas is alternately sent to heated regenerators for thermal cleaning, and the thermally cleaned gas is used to heat the SCR reaction, maintaining a constant optimal temperature for the SCR catalyst, reducing mechanical stress, and minimizing energy input.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the exhaust gas flows through multiple regenerators and SCR catalytic converter in sequence, then the purification of nitrogen oxides and organic components is achieved, but the temperature profile fluctuates strongly in the direction of flow over the SCR catalytic converter
Solution Approach 1:
The system divides the regenerator into multiple sections (first regenerator section and second regenerator section) with different functions. The first section handles thermal oxidation at high temperatures, while the second section handles heat exchange at lower temperatures, allowing the SCR catalyst to operate in a stable temperature range throughout its volume.
Solution Approach 2:
Different sections of the regenerator are assigned different thermal characteristics and functions. The first regenerator section is designed for high-temperature operation to oxidize organic components, while the second section is optimized for heat recovery at lower temperatures, creating localized functional zones that maintain overall system stability.
2Productivity
If the SCR catalytic converter operates with fluctuating temperature profiles, then the purification process continues, but the SCR catalytic converter experiences high mechanical stress
Solution Approach 1:
By segmenting the regenerator into multiple sections with different thermal roles, the system isolates the thermal fluctuations to specific zones while maintaining a stable temperature environment for the SCR catalyst, thereby reducing mechanical stress on the catalyst structure.
Solution Approach 2:
The second regenerator section acts as a thermal buffer that absorbs and dampens temperature fluctuations before they reach the SCR catalytic converter, protecting the catalyst from sudden temperature changes and reducing mechanical stress.
3Productivity
If heat is released during NOx reduction, then the chemical reaction proceeds, but the maximum NOx inlet concentration is limited due to overheating risk
Solution Approach 1:
The system extracts the heat released during NOx reduction in the second regenerator section, where it can be used for heat recovery without causing overheating of the SCR catalyst. This separates the exothermic reaction zone from the catalyst zone, allowing higher NOx inlet concentrations.
Solution Approach 2:
The second regenerator section serves as an intermediary between the exothermic NOx reduction reaction and the SCR catalyst, absorbing the released heat and preventing it from directly heating the catalyst, thus enabling higher reaction rates without thermal damage.
4Productivity
If multiple regenerators with SCR catalysts are used, then the purification capacity increases, but the quantity of catalyst required increases dramatically
Solution Approach 1:
The SCR catalytic converter is designed to perform multiple functions: it catalyzes NOx reduction, handles heat exchange, and operates stably across varying flow conditions. This multi-functionality allows a single catalyst unit to replace what would otherwise require multiple separate catalyst beds, reducing total catalyst quantity.
Solution Approach 2:
The patent combines the SCR catalytic converter with the regenerator system, integrating the catalyst into the existing thermal management infrastructure. This merging allows the catalyst to utilize the thermal environment created by the regenerator sections, eliminating the need for separate catalyst units and reducing overall catalyst requirements.
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 efficient thermal denitrification and oxidation of organic compounds without external energy, maintaining the SCR catalyst at optimal temperature, reducing mechanical stress, and minimizing catalyst usage, achieving high cleaning performance and reducing emissions.
Implementation Method 1
The exhaust gas to be cleaned is alternately sent to a raw gas inlet regenerator, the heat storage bodies of which have previously been heated
Implementation Method 2
the thermally cleaned exhaust gas emerging from the combustion chamber is sent to a clean gas outlet regenerator for heating its heat storage bodies
Implementation Method 3
The exhaust gas is then heated to 800 ° C in the upper high-temperature regenerator section, with the organic substances being thermally burned in the subsequent combustion chamber
Implementation Method 4
the organic substances being thermally burned in the subsequent combustion chamber
Implementation Method 5
oxidizable, thermally cleanable compounds... are, in particular, volatile organic compounds (VOCs for volatile organic compounds), carbon monoxide
Data Source
Figure 1
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Figure 2b
AI summary
For the purification of exhaust gas containing nitrogen oxides in combination with CO, VOCs or nitrous oxide, in particular exhaust gas generated during the production of cement clinker, nitric acid, adipic acid, fertilizers or uranium trioxide, a regenerative thermal afterburner with at least two regenerators (A, B) is used, in which the CO, VOCs and nitrous oxide are thermally purified at a temperature of 800 - 1000°C in the combustion chamber (1) and the nitrogen oxides are thermally reduced by means of an SCR catalyst (6) by supplying a nitrogen hydrogen compound, wherein the already thermally purified exhaust gas is taken from the respective two-part regenerator (A or B) at a suitable point at approx. 300°C, passed in a constant flow direction over the SCR catalyst (6) and then fed back into the remaining section (A', B') of the regenerator (A or B).