I would like to ask the seniors: The urea product has a strong ammonia smell; what are some ways to address this issue?

A strong ammonia smell indicates a high level of biuret, and it is necessary to reduce the biuret content. This post was last edited by lxq700918 on 2009-2-21 19:21.]

I’m not sure what the temperature setting for steaming is at your end; could you please provide more details? Is the vacuum level fine, within the normal range?

A high ammonia smell indicates a high ammonia content in the urea product; in other words, the level of free ammonia in the urine is high during the evaporation process, and this ammonia does not evaporate away. Generally, a large amount of free ammonia can be flashed within evaporation and flash equipment; the first and second stages of evaporation are primarily used to remove water. If the vacuum level is too low, the ammonia content will be high, resulting in a high ammonia level in the product. In the preceding process, attention should be paid to the temperature and pressure of the first and second stage decomposition systems to ensure the ammonium decomposition rate and the total ammonia evaporation rate, thereby reducing the ammonia content entering the evaporation process.

A high ammonia smell indicates a high ammonia content in the urea product, suggesting that the level of free ammonia in the urine is high during the evaporation process. Free ammonia can generally be vaporized in large quantities within low-pressure decomposition and flashing equipment; the first and second stages of evaporation are primarily used to remove water from urine. If the vacuum level is low, the ammonia content will also be high, resulting in a high ammonia level in the product. Therefore, in the preceding processes, it is necessary to carefully control the ammonia-to-carbon ratio in the high-pressure synthesis system, as well as the temperature and pressure in the low-pressure decomposition system and the pressure in the flash evaporation equipment, in order to ensure the decomposition rate of methylammonium and the total ammonia vaporization rate, thereby reducing the amount of ammonia that enters the evaporation process.

The strong ammonia smell indicates that the ammonia content in the urea product is definitely high. Generally, to ensure product quality and reduce the formation of biuret, and provided that the upstream system can operate stably and optimally, a portion of the free ammonia is intentionally directed to the evaporation system. When the vacuum level in the evaporation system meets the process requirements, both the moisture and ammonia components should also meet the specified standards. Personally, I think the real source of the ammonia smell is the decomposition of methylamine.

If it’s due to the reasons mentioned by those teachers above, then that would be a waste of ammonia. Measures need to be taken as soon as possible to reduce costs. If the temperature of the finished product is too high, it could also cause urea to decompose and release ammonia – is that possible?

Suggestions for addressing the strong ammonia smell in urea products: 1. It is necessary to ensure the ammonium decomposition rate and the total ammonia evaporation rate in the decomposition process. I wonder what process the original poster’s urea production facility uses? It is recommended to take samples in segments (for aqueous solutions, for example, by sampling from the outlets of Tower 1 and Tower 2) to determine whether the ammonia content in the urine falls within the specified design range. If it is high and the ammonium decomposition rate as well as the total ammonia evaporation rate are low, the decomposition temperature should be increased appropriately. 2. To ensure the ammonium decomposition rate and the total ammonia evaporation rate in the decomposition system, optimized control of parameters such as pressure and temperature is necessary. That is, while ensuring the effectiveness of the absorption system and system water balance, the lower the pressure, the better; the higher the temperature, the better (it is necessary to prevent the formation of excessive biuret). 3. While ensuring smooth material transfer, the vacuum level in the flash tank should be kept at a lower value. 4. The evaporation temperature can be increased slightly, as long as the level of biuret does not exceed the specified limit. 5. When controlling the decomposition temperature and evaporation temperature, there is a general principle: it is better to increase the decomposition temperature appropriately rather than raising the evaporation temperature as much as possible. Otherwise, the level of the final product, biuret, is likely to exceed the limit. 6. On the condition of ensuring smooth material transfer, it is advisable to keep the evaporation vacuum levels in stages 1 and 2 at relatively low values.

With a better vacuum level and a higher temperature in the evaporation system (as long as the quality of the resulting biuret remains satisfactory), less elemental ammonia will be produced； Urea should be relatively stable ； By controlling the stripping efficiency and distillation efficiency properly, the decomposition rate of methylammonium and the total ammonia evaporation rate will be better, resulting in less ammonia odor.

Reduce the dust a bit, and the ammonia smell should also improve.

Has it had an impact on product quality, and is it within acceptable limits?

Thank you for all your suggestions. We use a full-circulation aqueous solution method; the ammonia-to-carbon ratio is kept around 4.0, resulting in a high ammonia content. The first steaming is carried out at a temperature of 155–160° under a pressure of around 1.77 MPa; the second steaming takes place at around 130°, with the pressure generally not exceeding 0.18 MPa. These process parameters have been in use for many years now, and the product quality is satisfactory with no issues. I would like to ask what equipment can be added in the packaging section to remove the ammonia smell? Moreover, the packaging workshop here has a strong ammonia smell

Install ventilation devices in the packaging workshop, and add exhaust hoods at the packaging machines; the air flow volume should be sufficient. If possible, install a scrubber tower after the exhaust fan to remove free ammonia. This post was last edited by CHEN333 on 2009-2-22 at 11:43

There are also cases where all the relevant parameters meet the specified standards, and the product is classified as first-grade. For the distillation tower, flash tank, and first-stage evaporator, the outlet temperature is 138°C, 85°C, and 132°C respectively; the absolute pressure is 0.3 MPa, 0.038 MPa, and 0.023 MPa respectively

OP, the first steaming and second steaming you mentioned should correspond to the first and second stages of decomposition based on the indicators, right? Was it typed by mistake?

I made a mistake; it’s actually 1 and 2

The binary decomposition temperature can be maintained above 140 degrees; this does not increase the content of biuret, but it improves the rate of secondary decomposition, allowing for maximum removal of ammonia vapor. Meanwhile, raising the primary decomposition temperature to 135 degrees should help reduce the ammonia odor associated with urea, as well as decrease ammonia consumption. The ammonia-to-carbon ratio fed into the synthesis tower can also be reduced appropriately; packaging ventilation is a temporary solution rather than a permanent one. That’s exactly what we do. The current results are very good, with the biuret content at around 0.68. This post was last edited by lxq700918 on 2009-2-25 00:32.]

I don’t quite understand what you mean; how could the biuret level be high? ? Could you please explain it in detail!

A strong ammonia smell in the finished urea indicates a high level of free ammonia. However, it has two sources: 1. Poor decomposition in the previous process, resulting in a high evaporation load and excessive free ammonia. 2. Improper temperature control during the evaporation process itself; if the temperature is too low, decomposition is incomplete, resulting in excessive free ammonia. If it is too high, a condensation reaction occurs, producing free ammonia. The solution is to control the decomposition effect and maintain the temperature properly. This post was last edited by Boating on the Five Lakes on 2009-3-11 22:47.]

Reduce temperature and shorten residence time

If the finished urea has a strong ammonia smell, it indicates high levels of free ammonia. The reasons for this have been explained in detail by many people who have discussed this issue earlier. As a reminder, the finished urea has a strong ammonia smell; it’s just a personal perception, but this characteristic can indeed be determined. The free ammonia level in our plant’s urea products is kept below 120 ppm, so there is practically no ammonia smell. A control level of around 200 ppm is normal; any higher value requires adjustments to the vacuum and temperature. . There are two additional guesses for reference: 1. The ventilation volume of the granulation tower is too low, which may result in a strong ammonia smell. 2. Too much formaldehyde was added to the urea, causing the smell of formaldehyde to be mistaken for that of ammonia.