Low-Temperature Flue Gas Catalyst for NOx and HCN Purification
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Solution Overview
Problem
Current methods for coke oven flue gas treatment are inefficient in removing NOx and HCN at low temperatures, requiring high-energy processes and lacking a catalyst with high catalytic efficiency for low-temperature denitration.
Innovation Solution
A sol-gel method is used to prepare a synergistic catalyst (M-N/TiO2) by controlling pH, where highly active NH3 generated from HCN hydrolysis acts as a reducing agent to convert NOx into N2, eliminating the need for heating and reducing NH3 supply, thereby enhancing low-temperature denitration efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional SCR denitration process is used, then NOx removal efficiency is improved, but temperature requirement increases to 320-400°C
Solution Approach 1:
The patent changes the chemical parameters of the catalyst system by incorporating specific metal compounds (Mn, Fe, Co, Ni, Cu, Zn, Al, Ti, Zr, Hf) and controlling the NH3/NOx molar ratio (0.8-1.2) to enable low-temperature denitration. The catalyst formulation and reaction conditions are optimized to achieve high removal efficiency at temperatures below 200°C, fundamentally altering the operational parameters from conventional high-temperature SCR.
Solution Approach 2:
The patent employs composite catalyst materials combining multiple metal compounds with TiO2 support. The composite structure integrates the synergistic effects of different metals (e.g., Mn-Fe, Co-Ni, Cu-Zn) to enhance catalytic activity at low temperatures while maintaining structural stability and resistance to HCN poisoning, achieving both efficiency and temperature reduction.
2Reliability
If repeated heating and cooling processes are applied for desulfurization and denitrification, then pollutant removal is improved, but process complexity increases
Solution Approach 1:
The patent merges desulfurization and denitrification into a single integrated catalytic process. The catalyst system simultaneously removes both SO2 and NOx pollutants in one reaction zone without requiring separate heating and cooling cycles, significantly simplifying the process flow while maintaining effective removal of both pollutants.
Solution Approach 2:
The catalyst developed in the patent performs multiple functions: it acts as a desulfurization catalyst, a denitrification catalyst, and a HCN conversion catalyst all in one system. This multi-functional catalyst eliminates the need for multiple separate treatment processes, reducing equipment complexity and operational steps.
3Productivity
If high temperature heating is applied before denitration, then catalytic reaction efficiency is improved, but energy consumption increases
Solution Approach 1:
The patent changes the thermal parameters of the process by developing a catalyst that operates efficiently at low temperatures (below 200°C). This eliminates the need for high-temperature heating, reducing energy consumption while maintaining high denitration reaction rates through optimized catalyst formulation and NH3 dosing strategies.
Solution Approach 2:
The system utilizes the NH3 generated in-situ from HCN hydrolysis as the reducing agent for denitration, reducing the need for external NH3 supply and associated heating requirements. The process leverages the existing chemical energy in HCN to drive the denitration reaction, minimizing external energy input.
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
The catalyst achieves high-efficiency denitration at low temperatures, simplifies the process, reduces energy consumption, and effectively purifies NOx and HCN, eliminating the need for heating and minimizing NH3 supply, while maintaining a stable and long-lasting catalytic performance.
Implementation Method 1
the high-activity NH3 generated by hydrolysis of HCN at low temperature
Implementation Method 2
the high-activity NH3 generated by hydrolysis of HCN at low temperature is used as a strong reducing agent to catalytically convert NOx into N2
Implementation Method 3
a synergistic catalyst which has a high efficiency under low temperature is prepared by controlling the pH value in a sol-gel process
Data Source
AI summary
The present invention discloses a method of preparing a catalyst for low-temperature synergistic catalytic purification of NOx and HCN in a flue gas, and the use thereof. Citric acid is dissolved in ethanol to obtain a citric acid/ethanol solution; tetrabutyl titanate is added, mixed uniformly to obtain a tetrabutyl titanate-citric acid/ethanol solution; glacial acetic acid is added dropwise to react for 30-40 min to obtain a solution A; the metal salt solution was added dropwise into the solution A, mixed uniformly and added with nitric acid, ammonium hydroxide is added dropwise to adjust the pH value, and the temperature is raised at a constant speed to obtain a gel B; dried and then then baked at a temperature of 300-500° C. for 3-4 h, cooled in the furnace, pulverized, tableted and sieved to obtain the catalyst for the low-temperature synergistic catalytic purification of NOx and HCN in the flue gas.