2. HOW CAN WE AVOID AMMONIA?
Urea to Ammonia Hydrolysis
Why Urea Hydrolysis?
- Stable
- Non-volatile
- Environmentally benign material
- Safely transported, stored and handled
- Readily available in solid form, prill and granular
- Essentially 100% conversion
- Economical compared to 19% ammonia
Urea is the material of choice to avoid risk associated with ammonia. Some utility SNCR systems use urea to avoid ammonia. However, direct urea injection can cause damage to boilers. Converting urea to ammonia on site reduces the risk of boiler tube damage. Finally, direct urea injection is less economical to use than hydrolysis of urea to ammonia, since a significant percentage of the urea pyrolysis products are undesirable chemicals that do not participate in NOx reduction.
| U2A™ | Competing Systems |
|---|---|
| U.S. patent issued | Must avoid U2A™ patent |
| Once through process | Recycle process |
| Urea solution only storage - odor free | Recirculation of water leads to - "ammonia smell" |
| Indirect heat exchange | Direct steam addition |
| Closed water balance | Open water balance |
| Reactor at equilibrium | Equilibrium not maintained |
| Simple process control | Complicated process control |
| Easy shutdown | Difficult shutdown |
| Standard materials of construction | More expensive materials of construction |
| Standard reactor | Custom reactor |
