formaldehyde-free urea granules · 2018. 3. 27. · uhde fertilizer technology b.v. roermond, the...

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Formaldehyde-free urea granules

THOMAS KRAWCZYK Uhde Fertilizer Technology B.V.

Roermond, The Netherlands

Urea formaldehyde is the currently state of the art urea granulation additive. Its use is absolutely crucial in order to achieve the required product quality such as crushing strength, bulk density or low caking tendency. Furthermore it is also an inherent granulation aid which ensures a proper performance of the granulation process itself by limiting the generation of dust and providing a high build up rate of the granules. Unfortunately there are also some negative aspects to the use of the pre-condensates of formaldehyde and urea (UF 80, UF85). A major disadvantage is that it still contains a considerable amount of free formaldehyde which is harmful to health. It is categorized as a carcinogenic substance by the IARC (International Agency for Research on Cancer). In addition to that UF solutions contain a certain amount of methanol. Hence, it contributes to a significant part to the VOC emissions from an ammonia/urea complex, which might be requested to be very low by the local authorities. Furthermore urea product treated with formaldehyde cannot be sold as technical grade for most applications. It is not within the specification for the preparation of DEF (Diesel Exhaust Fuel) also known as AdBlue®.

It was UFTs goal in the past years to develop an alternative additive which is capable to guarantee the same product quality as well as at least the same process performance parameters while not contributing to any environmental impact. The result of the development is an alternative additive, which shows a product quality and a granulation performance which is at least as good as the bench mark UF. Different from UF solutions it is not harmful to health or the environment, since it consists of components which are biodegradable and are allowed to come into contact with food. Additionally the application of the alternative additive bears the possibility of utilizing the same urea granules for fertilizer, technical and DEF applications. This extends the range of application of urea ganules and reduces the efforts with regard to logistics for all producers of multiple urea grades drastically.

T. Krawczyk

418 Nitrogen + Syngas 2017 International Conference & Exhibition (London 27 February-2 March 2017)

1. MOTIVATION For more than three decades formaldehyde has been known as a substance potentially causing cancer. Recent research confirmes what has been suspected by most of its users. Over 80% of today’s urea production which, exceeds 180 million tons per annum, is used as fertilizer. This fertilizer grade urea, granular as well as most prilled urea, is treated with formaldehyde mostly applied as urea-formaldehyde pre-condensate (UF80, UF85). In order to ensure certain process parameters such as

- a controlled granule growth rate and limited dust formation during the production process, - a good product quality (crushing strength, dust and caking),

remain stable over a long period of time, an additive is needed. Although the formaldehyde is applied in the form of a pre-condensate in which most of the formaldehyde has already reacted with urea to form methylolurea, it still contains with usually more than 23% by weight a substantial amount of free formaldehyde. Therefore extensive safety precautions are required in order to make the handling safe. The discussions about the toxicity of formaldehyde, its carcinogenic and mutagenic effect on humans and animals started in the early 1980s.. However the recent Report on Carcinogens released by the National Toxicology Program (NTP) of the US department of Health and Human Services leaves no doubt with respect to the causal relationship between the exposure to formaldehyde and cancer in humans. A vast number of epidemiological studies have evaluated this relationship, including cohort and case-control studies of different professional groups. In particular, the National Cancer Institute (NCI) cohort of over 25,000 workers within industries producing or using formaldehyde indicates the coincidence between the occupational exposure to formaldehyde and nasopharyngea, sinonasal and lymphohematopeotic cancer risk. While in the past formaldehyde was classified as “suspected of causing cancer”, the International Agency for Research on Cancer (IARC) as part of the World Health Organisation (WHO) classified formaldehyde in 2011 as “known to may cause cancer”.

Fig. 1: left: Pictogram for substances hazardous to the human health as implemented by the GHS

right: classification of the carcinogenity of formaldehyde

The European Union has placed formaldehyde on the list of Substances of Very High Concern. These compounds have been listed in the Substitute It Now List (www.sinlist.org). The European Union wants such compounds to be replaced as soon as possible. As a consequence of numereous studies and the evidence of coincidence of cancer and the exposure to formaldehyde the legal authorities and dedicated organizations have adapted their classification regarding the carcinogenity of formaldehyde. As a consequence of the introduction of the GHS, the Globally Harmonized System of Classification and Labelling of Chemicals and its subsequent implementation within the American OSHA and the European CLP, the hazards of formaldehyde are more than ever in focal point of interest.


Nitrogen + Syngas 2017 International Conference & Exhibition (London 27 February-2 March 2017) 419

Although the carcinogenity of formaldehyde is evident, the different examinations also show that there is a dependency of its carcinogen effect and the related level of exposure in terms of concentration and duration. The German Institute for Risk Assesment (Bundesinstitut für Risikobewertung BfR) has conducted a study which came to the conclusion that at concentration of below 124 microgram per norm cubic meter (0.1 ppm) the cancer risk is neglieable. Vice versa, it can be concluded, that a repeated, considerably higher or prolonged exposure to formaldehyde may potentially cause cancer. Formaldehyde can be detected by its smell at concentration of 0.07 to 0.12 ppm if the sensivity for the detection is not reduced as a result of a prolonged exposure. This means that if formaldehyde is detected by smell then the concentration is already critical. Despite the difficulty of finding an appropriate threshold value for the exposure of a worker handling formaldehyde, the responsible authorities have adjusted the permissible exposure limits to accommodate the aforementioned findings as shown in table 1.

Table 1 Permissble Exposure Limits defined by different authorities.

Specification mg/m3 (ppm) USA (Occupational Safety and Health Administration - OSHA) PEL 0.92 (0.75) EU / Germany (TRGS 900) PEL 0.37 (0.3)

USA (National Institute for Occupational Safety and Health - NIOSH) REL IDLH CREL

0.02 (0.016) (10h-TWA) 24.56 (20) 0.12 (0.1)

USA (American Conference of Governmental Industrial Hygenists – ACGIH) TLV-C 0.37 (0.3) TWA – eight-hours time weighted average PEL – permissible exposure limit Max – maximum value on short-time basis REL – recommended exposure limit

IDLH – Immediately dangereous to life and health CREL – Ceiling recommended exposure limit TLV-C – Threshold limit value ceiling

In addition to the harmful nature of formaldehyde itself there is an additional, often over looked, limitiation to the application of urea-formaldehyde pre-condensate for urea production. The formaldehyde is produced via the catalytic oxidation of methanol therefore a certain amount of methanol remains in the UFC solution (e.g. 0.1 – 0.3 %wt Methanol). This methanol as a volatile organic compound is most likely released during the granulation process and emitted to the atmosphere. Consequently, it adds a quite significant amount of VOC emission to an ammonia/urea complex, which might be limited by local authorities. The absence of an adequate substitute and a partially ambiguous classification of formaldehyde have limited the efforts for a substitution of formaldehyde in by the fertilizer industry in the past, but this has changed now.

2. EFFECTIVNESS OF A GRANULATION ADDITIVE Before elaborating the route to such an alternative additive, it might be worthwile to have a closer look on how formaldehyde acts as an additive within the fluidized bed urea granulation process. Formaldehyde is both a granulation aid, which plays a key role during the granulation process itself, and an additive resulting in the desired product quality parameters for transport and handling. The mixing of urea with formaldehyde leads to a eutectical mixture. Although the urea solution is completely mixable in liquid state, there is an immiscibility of the corresponding solid phases. At the eutectic point the corresponding melting point is the lowest possible within all possible mixtures of urea and the additive and its reaction products. The presence of such an eutectical point leads to a liquid film on the surface of the granule which ensures a proper pick up of the sprayed material.

T. Krawczyk


Fig. 2: Reaction scheme between urea and formaldehyde to form urea formaldehyde resin

Furthermore formaldeyde reacts with urea to form methylolurea via polycondensation. The nucleophile addition of the formaldehyde occurs at different locations which leads to a cross linking effect, that makes up the backbone of the latter granule. This gives the product the desired crushing strength and reduces the amount of abrasion dust.

3. DEVELOPMENT OF AN ALTERNATIVE ADDITIVE Starting point for UFTs efforts to develop such an alternative additive was the collaboration with an well known and experienced specialist in the field of fertilizer additives: Holland Novochem. At first different agents were tested on lab scale with respect to their ability to act as a granulation additive for urea fluidized bed granulation. Only components which are not harmful to health or the environment were chosen. After identifying the potential specific effects of the different agents with regard to the desired product properties (e.g. particle growth, dust, hardness), different components and mixtures were tested in UFT’s batch operated pilot plant located in Leuna. With the data of the pilot plant trials it was possible to basically generate a database to carry out a product design for the alternative additives in terms of the desired urea product quality. Much lower dose of additive with much higher effect In a second campaign the potential additive compositions were applied in different combinations and dosages and benchmarked against urea formaldehyde. As a result, an alternative additive has been found which is at least as effective as urea formaldehyde. UFT’s newly developed alternative is composed of different functional polymers in combination with a carboxylic acid. All of these agents are much less toxic (non hazardous) and all of them have several FDA (Food and Drug Administration) approvals for direct and/or indirect food contact. The functional polymers are generally exempted from the European REACH programme due to their polymeric nature.The carboxylic acid is classified as a not hazardous substance. The dosage of the alternative additive which is necessary in order to achieve at least the same product quality as well as the same process parameters is less than half of the amount of formaldehyde. As shown in table 2 the new alternative additive formulations are able to produce a granular urea product which shows at least the same product quality as is possible with urea fromaldehyde. Furthermore this product opens up additional fields of application of the product not limited to the fertilizer industry.



Table 2 Comparison of product quality parameters for urea granules treated with urea

formaldehyde and UFT’s alternative additive.

Treated with UFC (UF80)

Treated with Alternative Additive

Total Nitrogen % wt > 46.2 > 46.2 Biuret Content * % wt 0.7 – 0.8 0.7 – 0.8 Formaldehyde % wt 0.4 0 Alternative Additive % wt 0 ~0.2 Moisture % wt 0.2 – 0.3 0.2 – 0.3 Crushing Strength kg 4.1 on ∅ 3.15 mm >4.1 on ∅ 3.15 mm Caking tendency - same or less Dust % same or less

Application Fertilizer Fertilizer,DEF,Technical,

Cattle Feed

4. TECHNICAL AND DEF GRADE UREA GRANULES The fertilizer grade urea demand is steadily growing due to the fact that there is a steady growth of the world’s population and its standard of living (change in diet towards more meat). However there is an even higher increase for the demand of non-fertilizer grade urea. The IFA forecasts the non-fertilizer demand will account for almost half of the net increase of the global urea demand. The root cause of the growth of the non-fertilizer urea demand is due to the increased usage for UF resins and deNOx applications. Due to stricter regulations concerning the emission figures for nitrogen oxides in all kinds of diesel engines the demand for DEF (Diesel Exhaust Fluid) has exploded in the last years. The annual production of DEF used as a consumable for the selective catalytic reduction of nitrogen oxides accounts for approximately 2.3 million metric tons of urea. Its contribution to the global urea production in 2020 is estimated to be more than 4 million metric tons. Currently the price for DEF solution on the US market is at about 2.80 $ per gallon, which can be converted into a urea price of more than 2,000 $ per metric ton assuming that the costs for deionized water can be neglected. In other words, the revenue for almost the same product is ten times the revenue of a regular fertilizer product.

T. Krawczyk


Fig. 3: Estimated development of future urea demand

The key for a today’s producer of fertilizer grade urea to enter the DEF market is the product quality. In order to comply with the requirements for the urea as raw material for DEF the composition of the solid material dissolved in deionized water must fulfill the requirements of the norms ISO 22241 or DIN 70070. Ultimately all impurities or contaminations contained in the solid material will be present in the final DEF solution. Primarily the tolerated amount of only 5 ppm of aldehydes forms the main obstacle which producers have to overcome. With UFT’s approach to a new alternative additive it is possible to produce granular urea which complies with the aforementioned norms specifying the requirements for DEF with limited additional costs. Why is it interesting to deliver DEF in solid form? Another major advantage of the production of DEF in its most reduced form namely as a DEF compliant solid which includes all benefits of a granular product with respect to the mechanical properties, is that the supply chain can be reduced to a minimum. The application of the alternative additive is carried out by simple substitution of the content of the urea formaldehyde tank. As it is illustrated by figure 4 neither additional equipment nor any other mechanical modification to an exisiting plant is necessary. Furthermore, all provisions within the urea synthesis to enable the production of DEF solution such as tanks, piping or instrumentation etc. are obsolete. In comparison to application ready DEF solution only a third of the tonnage needs to be stored and transported. .



Fig. 4: Benefits of “DEF granules”

The final dissolving of the urea in deionized water poses the only minor additional step within the supply chain. During the Integer Emission Summit & DEF Forum in 2013 the feasibility of the route via a solid distribution has been evaluated and found to be the most cost effective. The costs for blending DEF from dry urea were mentioned to be very low and amounting to the range of 5 to 7 $ cents per gallon. In line with these thoughts figure 5 shows a comparison of the relative production costs for DEF starting from the urea synthesis normed to the cost for the preparation via DEF complaint granules. Obviously the difference in costs is directly related to the transport distance between production and final consumption.

Fig. 5: Comparison of Production costs for DEF via granular urea and application ready DEF solution

5. SUMMARY AND OUTLOOK The perception of formaldehyde has changed and the need for its substitution is stronger than ever. Producers of urea already face difficulties to ensure the supply of formaldehyde due to limitations by stricter regulations. Furthermore studies, national and global regulations unambiguously confirm that banning of formaldehyde will turn a urea plant into a much healthier working place for the operators.

T. Krawczyk


Now a big step has been taken to be able to substitute formaldehyde as a chemical with a very high concern within a urea granulation plant. In addition UFT’s newly developed alternative additive also offers the opportunity to gain an added value for granular urea products far beyond fertilizer applications. It is now as easy as it gets to enter the still growing and higly profitable business of the DEF market for instance. Furthermore also other technical applications of the granular formaldehyde-free product are possible, which are more lucrative than the same product on the rather stagnant fertilizer market. The envisaged next step is the industrial application of the alternative additive, which is carried out by means of a simple refill of an existing urea formaldehyde tank with an alternative additive, neither being harmful to humans nor to the environment.

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formaldehyde-free urea granules · 2018. 3. 27. · uhde fertilizer technology b.v. roermond, the...

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