Urea Gasification for Low-Temperature Ammonia Generation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing processes for generating ammonia from urea are inefficient at low temperatures, leading to byproduct formation and equipment fouling, which complicates low-temperature applications such as SCR and ESP operations.
Innovation Solution
A two-stage process involving thermal gasification of urea followed by controlled catalytic hydrolysis, where the first stage produces ammonia and isocyanic acid, and the second stage converts isocyanic acid to ammonia with careful temperature and water control to minimize byproduct formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If thermal gasification of urea is used, then ammonia production efficiency is improved, but byproduct formation and equipment fouling worsen at low temperatures
Solution Approach 1:
The process is divided into two distinct stages: a high-temperature gasification stage (700-1400°F) that converts urea to ammonia and isocyanic acid, and a low-temperature catalytic hydrolysis stage (above 370°F) that converts isocyanic acid to ammonia. This segmentation allows each stage to operate at optimal temperatures, preventing byproduct formation while maintaining high ammonia production efficiency.
Solution Approach 2:
The invention changes the temperature parameter between stages - maintaining high temperature (700-1400°F) in the gasification reactor to prevent byproduct formation, then transitioning to a lower but still controlled temperature (above 370°F) in the hydrolysis reactor. This parameter change enables efficient ammonia production without the equipment fouling problems that occur at low temperatures in single-stage processes.
2Device complexity
If single-stage thermal gasification is used, then process simplicity is improved, but byproduct condensation and catalyst fouling worsen
Solution Approach 1:
The single-stage process is segmented into two reactors with distinct functions: the first stage performs thermal gasification at high temperature to produce ammonia and isocyanic acid without byproducts, while the second stage performs catalytic hydrolysis at lower temperature to convert remaining isocyanic acid. This segmentation eliminates byproduct condensation and catalyst fouling while adding only one additional reactor to the process.
3Use of energy by moving object
If low temperature operation is used, then energy consumption is reduced, but urea decomposition completeness worsens
Solution Approach 1:
The decomposition process is segmented into two stages: high-temperature gasification (700-1400°F) that achieves complete urea conversion to ammonia and isocyanic acid without energy-wasting byproducts, and low-temperature catalytic hydrolysis (above 370°F) that efficiently converts isocyanic acid to ammonia. This segmentation ensures complete decomposition at lower overall energy consumption compared to single-stage high-temperature processes.
4Object-generated harmful factors
If high temperature gasification is used, then byproduct formation is reduced, but equipment material requirements worsen
Solution Approach 1:
The process segments the high-temperature requirement to only the gasification stage (700-1400°F), where it is needed to prevent byproduct formation. The subsequent hydrolysis stage operates at a lower temperature (above 370°F), reducing material requirements for the second reactor and downstream equipment. This segmentation optimizes material requirements while maintaining low byproduct formation.
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 ammonia production at low temperatures without byproduct condensation or equipment fouling, enabling effective operation in low-temperature applications like SCR and ESP systems.
Implementation Method 1
When aqueous urea is heated, a number of chemical reactions, controlled by temperature-dependent rate constants, determine how urea is broken down
Implementation Method 2
The HNCO will be converted as follows: HNCO + H2O → CO2 + 2NH3
Implementation Method 3
the HNCO, unless hydrolyzed or maintained very hot can form solid byproducts
Data Source
AI summary
Disclosed are methods and apparatus for providing an ammonia feed for a low-temperature process. The process includes two defined stages, gasification and hydrolysis. In a first stage thermal reactor, an aqueous urea solution is fed to a gasification chamber and heated gases are controlled in response to demand from a low temperature process requiring ammonia. The heated gases and aqueous urea are introduced into the gasification chamber upstream to fully gasify the solution of aqueous urea to a first stage gas stream comprising ammonia and isocyanic acid. The first stage gas stream is withdrawn and maintained hot enough to prevent solids formation. All amounts of urea feed, water and heated gases fed into the first stage thermal reactor are monitored and adjusted as necessary to achieve efficient hydrolysis in the second stage hydrolysis reactor. The second stage gas stream is withdrawn from the second stage reactor responsive to demand from a low temperature process requiring ammonia.