What is the reason for the relatively low ammonia content in the exports? ?

There are many factors that affect the ammonia output from the tower: 1. Pressure; 2. Temperature: whether the temperature distribution in the catalyst layer is appropriate. At the upper layer of the catalyst layer, when the gas first enters the tower, the ammonia concentration is low; therefore, increasing the temperature helps to accelerate the reaction rate. In the lower layer, since the ammonia concentration is already higher, the temperature can be reduced slightly to slow down the reverse reaction rate. Hence, the optimal operating temperature is generally set at the top layer. Of course, when the catalyst is used for a longer period of time, the shift of the hot spots downward is a different matter. 3. Circulation rate; 4. Ammonia fed into the tower: A high level of ammonia fed into the tower increases the rate of the reverse reaction. It is possible to increase the ammonia cooling load and the water cooling load, reduce the ammonia cooling temperature, and thereby lower the ammonia content entering the tower. Also, pay attention to the liquid level in the condenser separator – it should not be too high. 5. It is closely related to the gas composition; for example, if there are trace amounts of certain substances, or if the content of inert gases is high, or if the hydrogen-to-nitrogen ratio is incorrect ； 6. The activity of the catalyst also plays a significant role; higher activity results in a higher ammonia content in the output ； The quality of catalytic reduction depends on whether the loading is uniform. 7. The amount of cold shock during operation and the amount of supplemental air ； 8. There is also the structure of the tower internals and whether there are any defects, etc. Additionally, it is recommended that the original poster check if the links provided will be helpful: 1. Reasons for low ammonia output; 2. Low ammonia content at the outlet of the synthesis tower; 3. Reasons for low ammonia output at the outlet of the synthesis tower

Measure the composition of the gases entering and leaving the synthesis tower, and determine whether the composition of the outlet gases meets the limits imposed by chemical equilibrium. If equilibrium is achieved, it indicates that there is no problem with the catalyst’s activity. Then check the operating conditions, such as the fresh gas and inert gas as mentioned above, the hydrogen-to-nitrogen ratio, the system pressure, whether the space velocity is too high, and whether there is liquid ammonia present. . .

It is recommended to carry out a process simulation for ammonia synthesis; establishing the kinetics of the synthesis reactions can be somewhat complicated. Analysis and diagnosis can then be conducted on this basis in order to obtain optimized process parameters!

For a catalyst of 18M3 and over 50 tons, it should be a production facility with a capacity of 180,000–200,000 tons per year; the circulation volume needs to be only 12M3, and the temperature at the second outlet is 290°C. The first thing to suspect is that the synthesis reaction is not efficient. But it’s also surprising that the system pressure is only 24 MPa. A reasonable explanation is that the system equipment is not matched to the production load, resulting in overpowered equipment. You can tell by looking at your factory’s current production volume; by the way, what is your current production level?

The design capacity is 180,000 tons; due to the parallel operation of two systems, the total capacity is 240,000 tons.

(1) The ammonia content in the imported material is too high. It is necessary to reduce the content of imported ammonia; otherwise, the equilibrium concentration of ammonia will decrease, affecting its production. The best way to reduce imported ammonia is to lower the temperature of ammonia cooling; the lower, the better (our plant’s target range is -5°C to -15°C). The concentration of imported ammonia in our plant is around 1.5%. (2) Increasing the synthesis pressure can promote the ammonia synthesis process in a favorable direction, which helps to raise the outlet concentration of ammonia. At the same time, as the pressure increases, the efficiency of ammonia cooling also improves, which is beneficial for reducing the inlet ammonia concentration. However, as pressure rises, consumption may also increase; therefore, there needs to be a balance in this regard. (3) An appropriate hydrogen-to-nitrogen ratio, generally kept between 2.2 and 2.8.

Are both sets units with a capacity of 180,000 tons? The plant operates at only 60% of its production capacity, and moreover production takes place in parallel; it is highly likely that some units fail to reach even half of their designed capacity. Additionally, regarding the suggestion to return to the 7th floor, theoretically speaking, the lower the ammonia content entering the tower, the more ideal the reaction will be; however, it is necessary to properly calculate the economic parameters for the entire production line. For manufacturers that use ammonia in their processes, the pressure of gaseous ammonia can remain unaffected by the cooling load; reducing the ammonia content entering the tower is an effective way to optimize the synthesis reaction. For manufacturers that rely solely on chillers to recover gaseous ammonia, an ammonia content of ≤1.5% implies an ammonia cooling temperature below -10°C and a gaseous ammonia pressure below 0.06 MPa; the energy consumption associated with the chillers will thus influence the overall energy consumption in ammonia synthesis. This is just a brief mention here – ultimately, it is the economic indicators that should determine everything. Furthermore, in production practice, system pressure, space velocity, and net ammonia value are interdependent. The results of system optimization are ultimately reflected in output and energy consumption; economic indicators achieved through appropriate space velocity and pressure are likely to be much better than those obtained by simply aiming for high values. It’s better to give more role to the process engineers; in the end, it’s the data that matters.

The outlet temperature at the second stage of the synthesis tower is low; this may be due to excessive temperature control at the lower part of the tower or inaccurate temperature settings, resulting in an excessive amount of cold gas that dilutes the ammonia concentration. It is recommended to adjust the cold shock appropriately; the temperature at the lower section of the hot spot should be 5–10 degrees lower than that at the upper section.

There are many reasons for the low ammonia content at the outlet of the synthesis tower, such as the composition of the feed gas and the reaction conditions (temperature, pressure, flow rate). In general, these factors are difficult to change; however, it is also essential to adjust the hydrogen-to-nitrogen ratio appropriately. In normal production, this problem is largely directly related to the structural design of the components inside the synthesis tower and the performance characteristics of the catalyst. In other words, the level of ammonia content in the output stream depends on the reaction conditions in the synthesis tower; the higher the reaction intensity, the higher the ammonia content in the output stream, and vice versa. Therefore, to solve this problem: 1. Adjust the gas composition properly. Control the appropriate hydrogen-to-nitrogen ratio (based on the requirements of the catalyst performance) to minimize the ammonia content entering the tower. 2. Check for any issues with the internal components of the synthesis tower (during design, assembly, and operation). 3. Select a catalyst that suits the process characteristics of this plant (in terms of activity, resistance to toxicity, mechanical strength, etc.)

Guochang’s cryogenic internal components have an ammonia net value of around 10.5, which is slightly lower than that of non-cryogenic synthesis towers； The tower should operate under light load conditions; it is normal for the ammonia net value to be lower when it is not operating at full capacity ； The temperature at the second outlet is low; it’s necessary to check whether there is a problem with the packing between the second inlet and the second outlet ； Based on the current ammonia net value and circulation rate, it is possible to calculate the theoretical ammonia production under current conditions, and compare it with the actual ammonia production to see if they match ； Based on the current system pressure, there should be no major issues with this tower.

Could it be that there is a leak in the heat exchange packing, causing the gas to take a shortcut instead of entering the synthesis tower? If that is the reason, the pressure will be higher than the normal level.

The pressure of gaseous ammonia in our ammonia cooler is generally around 0.15 MPa to 0.18 MPa – isn’t that a bit high? Also, even in our normal production processes, not using the cold shock control system and instead relying on bypass routes for the circulators must also play some role in this! During normal production, there is now a problem of large temperature differences; it is suspected that it might be related to the catalyst filling This post was last edited by 7276166 on 2009-4-10 21:30.]

I suspect that there is a short-circuit in the radial tower gas of your ammonia synthesis unit; also check whether the pressure in the synthesis system is normal.

How could the pressure not be abnormal? What’s your stress level like? I have designed 2 units of the 6M180 machines; due to power issues, they have not been turned on yet. I plan to carry out maintenance on them in the next few days so that they can be integrated into the system. What about the ammonia content? Is it difficult to find a shortcut for the gas inside the tower? Is there a way to check it?