Ammonia Injection Ejector for Exhaust Denitration
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional exhaust smoke denitration systems face issues with handling high-temperature gases, nozzle clogging due to sulfur oxides, and potential dioxin production, particularly in municipal incinerator applications, which complicate the ammonia injection unit and reduce reliability.
Innovation Solution
The system employs an ammonia injection unit with an ejector and compressed air blower to mix exhaust gas with air, diluting the gas and reducing temperature, thereby preventing ammonia oxidation, inhibiting dioxin production, and avoiding nozzle clogging by regulating the exhaust gas flow and temperature to maintain a safe range for ammonia water evaporation and injection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high-temperature exhaust gas is used for ammonia water evaporation, then evaporation efficiency is improved, but ammonia oxidation occurs and thermal stress increases
Solution Approach 1:
The exhaust gas flow is divided into two paths: one path goes through the evaporator to provide heat, while another path bypasses the evaporator and mixes with the evaporated ammonia gas. This segmentation allows the system to utilize high-temperature exhaust gas for evaporation while preventing direct contact between high-temperature gas and ammonia, thus avoiding oxidation.
Solution Approach 2:
A bypass passage acts as an intermediary channel, allowing exhaust gas to mix with ammonia-containing gas without passing through the evaporator. This intermediary path enables temperature control and prevents harmful thermal effects on ammonia while maintaining evaporation efficiency.
2Productivity
If high-temperature exhaust gas is used for ammonia water evaporation, then evaporation efficiency is improved, but thermal stress on equipment increases
Solution Approach 1:
The system segments the exhaust gas flow into evaporator flow and bypass flow, allowing selective heating of ammonia water while preventing high-temperature gas from directly contacting ammonia-containing passages, thereby reducing thermal stress on equipment.
Solution Approach 2:
The bypass passage serves as an intermediary that mixes cooled exhaust gas with ammonia-containing gas, acting as a thermal buffer that protects equipment from direct thermal exposure while maintaining evaporation efficiency.
3Productivity
If sulfur oxide-containing exhaust gas is used, then denitration can proceed, but nozzle clogging occurs
Solution Approach 1:
The bypass passage acts as an intermediary mixing zone where exhaust gas mixes with ammonia-containing gas before reaching the injection nozzle. This mixing dilutes sulfur oxide concentration and prevents direct contact between sulfur oxides and the nozzle interior, avoiding clogging while maintaining denitration capability.
Solution Approach 2:
By changing the flow parameters and mixing ratios in the bypass passage, the system controls the concentration of sulfur oxides and other harmful substances reaching the nozzle, preventing clogging while maintaining effective denitration.
4Productivity
If exhaust gas circulation system is added for ammonia water evaporation, then evaporation can be achieved, but device complexity increases
Solution Approach 1:
The system merges the exhaust gas circulation function with the ammonia water evaporation function by using the same evaporator for both purposes. The bypass passage is integrated into the existing exhaust gas flow path, combining multiple functions without adding separate dedicated systems.
Solution Approach 2:
The evaporator and exhaust gas passages are designed to serve multiple functions: heating ammonia water, cooling exhaust gas, and enabling controlled mixing. This multi-functionality reduces the need for separate dedicated equipment, thereby reducing overall system complexity.
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 effectively reduces thermal stress, prevents nozzle clogging, and inhibits dioxin production by maintaining the ammonia-containing gas temperature within a safe range, enhancing the reliability and efficiency of the denitration process while avoiding the need for costly cooling systems and protectors for blower components.
Implementation Method 1
an ejector (7) that extracts the exhaust gas, provided at a front end of the exhaust gas supply passage (6)
Implementation Method 2
a compressed air blower (8 or 8′) that supplies compressed air to the ejector (7)
Implementation Method 3
an ammonia water evaporator (10) that mixes the mixed gas of an exhaust gas and air from the mixed gas supply passage and the ammonia water from the ammonia water supply passage (12) and evaporates the ammonia water
Implementation Method 4
ammonia water regulated to a necessary flow by an ammonia injection control valve 11 is injected into the evaporator 10, and is heated by the exhaust gas inside the evaporator 10
Implementation Method 5
a denitration catalyst layer (2) disposed on a passage of an exhaust gas discharged from a gas turbine
Implementation Method 6
injects ammonia as a reducing agent for a denitration reaction from an ammonia injection unit at an upstream side of a disposing part of a denitration catalyst, sufficiently mixes the ammonia with the exhaust gas, and then causes a denitration reaction on the denitration catalyst
Data Source
AI summary
An exhaust smoke denitrating apparatus in which using an NH3 injection unit, compressed air is fed from blower to ejector for extracting of exhaust gas from HRSG1, and with thus obtained mixed gas, NH3-containing gas is produced from NH3 water by NH3 water evaporator, the NH3-containing gas injected through NH3-containing gas injection nozzle of the HRSG1 disposed on a front stream side of denitration catalyst layer. As any high-temperature exhaust gas is cooled and diluted by compressed air, there is no danger of oxidation of NH3 during the stage of evaporation of NH3 water. The moisture level of exhaust gas can be lowered, thereby enabling inhibition of any drain generation in exhaust gas extraction piping. Air warming within NH3 water evaporation system can be carried out at an early stage. The temperature of NH3-containing gas obtained by evaporation of NH3 water can be lowered, and a lowering of thermal stress within NH3-containing gas piping can be easily accomplished, so that denitration of exhaust gas can be easily accomplished. Even when sulfur oxides are contained in exhaust gas, it is feasible to avoid any problem of clogging of the NH3 water injection nozzle.