How to modify low-pressure water after the carbon dioxide stripping process in series with low-pressure ammonium methoxide condensers
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Currently, many urea plants that use the carbon dioxide stripping method are undergoing technical upgrades to their low-pressure systems in order to reduce ammonia consumption. Add a low-pressure ammonium methoxide condenser. Please discuss whether to use co-current or counter-current cooling for the low-pressure ammonium methoxide condenser after connecting it in series. This post was last edited by lxq700918 on 2009-4-3 23:05.]
For the cooling of water at low temperatures, a control approach of \"high flow rate and small temperature difference\" is suitable. Therefore, it is recommended to adopt counterflow cooling. I ask the experts to continue sharing their insightful views.
The temperature difference entering the previous condenser should be smaller; otherwise, excessive absorption may occur, which could lead to crystallization in the first condenser. Countercurrent flow is preferable in such cases. It’s just my personal opinion; I’d appreciate some guidance from those who know more.
In my opinion, in principle counterflow can reduce the heat exchange area. However, since it is necessary to increase the concentration of the ammonium methylate solution in order to reduce ammonia consumption, raising this concentration increases the risk of crystallization when cooling is carried out using the original temperature of the adjusting water. Therefore, if counterflow cooling is used, the inlet temperature of the adjusting water must be increased appropriately, which results in an increased heat exchange area; detailed calculations are required for this
Although counterflow heat exchange can reduce the area. However, to reduce ammonia consumption, it is necessary to lower the temperature of the low-temperature cooling water and increase the concentration of the ammonium methoxide solution, which in turn increases the risk of crystallization. Therefore, I believe that co-current absorption should be used: in the first heat exchanger, the concentration of the ammonium methoxide solution is low but it carries a large amount of heat; thus, it allows for thorough heat exchange with the low-temperature cooling water, resulting in most of the medium condensing. Once the temperature of the low-temperature cooling water has increased, it then enters the second low-pressure ammonium methoxide condenser. Here, as the concentration of this medium increases, the temperature of the low-temperature water also rises accordingly, preventing crystallization blockages caused by heat exchange between this low-temperature water and the concentrated ammonium methoxide solution. Using co-current absorption can sufficiently reduce the low-temperature water temperature to 60 degrees Celsius
Are you using parallel flow operation? ?
When I arrived, it had already been set up in reverse flow, but now it’s difficult to lower the water temperature. If it decreases, the methylammonium pump fluctuates. I’ve tried many times already. Currently, the temperature of the low-temperature water is 70 degrees Celsius, while that of the ammonium methoxide solution is 75 degrees Celsius
What are the reasons for fluctuations in methanamide pumps? Is there crystallization in the condenser?
I would like to ask whether connecting heat exchangers in series can reduce the NH3 concentration in the vapor phase at the outlet of the ammonium methoxide condenser? After all, at the same temperature and pressure, the condensation of NH3 has already reached equilibrium; can this achieve the goal of reducing ammonia consumption? Did the poster increase the capacity of the ammonium methoxide condenser in order to raise the load on the system?