White Paper | Confidential and Proprietary | March 2012 

## Urea Sourcing Issues

Dry urea is an available commodity on a worldwide basis, with many off

- shore urea production facilities being located near economical sources of natural gas, which is a key raw material required for urea production. Once dry urea is manufactured, it is shipped worldwide to meet the demands of a wide range of markets.

S olid commercial grade and agricultural grade dry urea is very hygroscopic , and can create a storage and handling problems if the dry urea is not manufactured with an anti

- caking agent

. Dry urea is also very friable and can break down into a powder during storage and handling. The powder has a high surface area , which is even more hygroscopic

. Untreated dry urea exposed to moisture or even in humid environment s will stick and compact during shipment, creating shipping and handling problems.

In order to prevent the problems with handling dry urea, manufacturers will add a small amount of conditioning
agent to the hot urea liquor . This urea liquor is an intermed iate product of the urea production process. The conditioning agent is a formaldehyde

- based additive, which is consumed in a polymer reaction to form to a methylenediurea (MDU) coating . The MDU is what binds the dry urea together and acts as an anti

- caki ng agent for the dry urea once it is made into prill or granular form

. Most MSDS sheets for dry urea reference MDU, since
when the hot urea liquor and conditioning agent are added, t he formaldehyde is consumed in the reaction. The
MDU is not a threat to t he environment or a personnel hazard

.
Some urea manufacturers have marketed a "formaldehyde free ” urea product (FF). The 70% urea liquor is typically taken right from the urea production process as an intermediate product. Whether shipping by truck or rail, the hot 70% liquor will lose about 1.5 ° F per day in transit. To avoid crystallization of the hot liquor, its temperature needs to be maintained above 135 ° F . Unfortunately, hot urea liquor also undergoes an isomer shift to ammonium cyanate that libera tes copious amounts of free ammonia

, which can be potentially hazardous . The shift is irreversible and relentless, and t he chemical reaction accelerates with increasing temperature. At 135 ° F

, the reaction is rather slow, but at 1 50 ° F

, it moves at a quicker rate

. T he principle can be identified that urea liquor of increasing concentration takes higher temperatures to keep it in solution, and that higher temperatures accelerate the rate of conversion from urea to free ammonia

.

As a result, rail shipments o f FF urea have proven to be quite challenging. Due to the uncertainty with rail delivery times, shipping the product at higher temperatures in order to avoid crystallization may solve one problem, but may create an even larger problem. Truck shipments w here the product can be delivered in a day or two have been the practical limit of shipping 70% urea liquor. A 60% or 50% urea solution can be created from the urea liquor, which can then be delivered via rail. These concentrations would involve dilution prior to shipment, and would add to the shipping costs of the product.

FF urea may be a good economic choice based on the jobsite proximity to the FF source, however, dry urea with MDU has more shipping flexibility, and a result, more worldwide sources of the product are available. Dry urea can be solutionized at individual plant locations or at regional production facilities to any required concentration.White Paper | Confidential and Proprietary | March 2012 

## Urea Quality Impact on Fuel Tech Processes

Fuel Tech’s NOxOUT SNCR/RRI systems, as well as t he NOxOUT ULTRA equipment are both completely insensitive to MDU dry urea sources, or for FF urea sources. This includes any urea solutions created by solutionizing dry urea, or by the dilution of FF urea.
The SNCR system typically uses a 50% urea solut ion as the base feedstock. Prior to injection into the furnace to reduce NOx emissions, the urea solution is typically diluted down to levels below 25% concentration prior to injection. The final urea concentration is determined during final startup and op timization, where system performance is optimized while trying to minimize urea solution consumption. For the RRI systems, the urea concentration is usually 30

- 50% at the point of injection.

Since dilution water from the plant site is used in both systems described above, there is a water quality specification associated with the systems to ensure that the dilution water does not cause pluggage of the system or loss of NOx reduction performance. In many cases, plants do not have dilution water which is o f boiler makeup water quality, and the use of some of these water sources may create problems at the plant site.

When dilution water sources are not of boiler makeup or demineralized water quality, NOxOUT A and NOxOUT
HP urea solutions are available from independent reagent suppliers. The NOxOUT A and HP help enable the systems to function properly when dilution water quality may be questionable or to provide plant flexibility in selecting dilution water sources. These NOxOUT end products include small amounts of two different concentrates, ACONC or HPCONC accordingly, which are mixed in by the licensed reagent suppliers to create the final urea solution products prior to delivery to the jobsite.

Unstabilized urea solution can be used where there is hi gh quality dilution water available at a plant site. All of the urea solutions, whether unstabilized urea solution, NOxOUT A or NOxOUT HP, are not affected by the source of the urea, whether the urea came from a dry source which had MDU, or whether it the urea started from a “formaldehyde free” product.

The NOxOUT ULTRA process will generate ammonia on the plant site for use with an SCR system to reduce NOx emissions, as an alternative to either anhydrous or aqueous ammonia. There are no issues with the use of the FF urea solution or dry urea containing MDU, or any urea solution created using this dry urea. It is our understanding based on market reports, that there are other urea conversion technologies to generate ammonia

on

- site for use in SCR applic ations which require FF urea as the source. The use of urea containing MDU, or any solution created from this urea source, seems to cause potential problems within these other systems. The NOxOUT Ultra process provides the maximum flexibility in selectin g urea sources to be used for on

- site generation of ammonia. 

## Summary

Fuel Tech’s complete line of NOxOUT systems are unaffected the source of the urea feedstock, whether a dry urea production containing MDU, or a “formaldehyde free” urea source, providing maximum sourcing flexibility when meeting the urea specifications. For a list of licensed urea suppliers offering NOxOUT A and NOxOUT HP urea solutions for use with the SNCR and RRI systems when plant dilution water quality is a potential issue, go to
www.ftek.com

.