Urine tower vapor vent control (carbon dioxide stripping process)

It is possible to add on-site stop valves, but I don’t think it’s necessary to include a remotely controlled discharge control valve. During normal operation, this valve must be closed; otherwise, substances such as ammonia and urea will leak out directly, contaminating the environment. If it is a control valve, internal leakage can be very troublesome, as it increases the number of leak points in the system. The function of this valve is to replace CO2 during the initial startup, in the case of a high-pressure startup method; it has no other special functions. Therefore, this valve is used infrequently, and adding an on-site shut-off valve will suffice.

However, due to the extremely high pressure in the synthesis tower, it is too dangerous to have someone operate this valve; therefore, we might consider installing shut-off valves before and after the control valve.

There should be a control valve, with a shut-off valve placed in front of it; this is crucial for emergency handling as well as during startup and shutdown operations, and it must be installed

It would be more helpful to understand the opinions of experienced operators who have actually worked with urea plants! This is mainly because the operators are in direct contact with the device’s operation moment by moment, and they have an understanding of the details of actual production; they know best the specifics of the control process. Therefore, when it comes to setting up the control system (including valve settings), their opinions are by far the most valuable. Last edited by ysd168 on 2009-2-8 08:55.]

Well, as mentioned on the third floor, one of the disadvantages is that it depends on what your supervisors decide. If safety is a concern and you’re not afraid to spend money, then installing a control valve would be a reasonable solution.

There is absolutely no need to install a control valve, for the following reasons: 1. The vapor vent valve of the urea tower is used only during the initial startup of the urea production plant; it is not needed at other times, meaning its usage frequency is very low – perhaps only 1 to 2 times a year at most. If there is too much, it indicates that the device’s operating cycle is short or that it has been operating abnormally for a long time, which suggests a problem. 　　2. When using this vent valve, the pressure in the high-pressure circuit is at most a little over 8.0 MPa, and CO2 is released, so there is no danger involved. If starting up using the low-pressure method, there is no need to operate that vent valve; in other words, it can be omitted. 　　3. During normal operation, if there is a problem with the high-pressure circuit and overpressure occurs, according to current environmental protection regulations, it is not allowed to relieve pressure by opening this valve (it is known that some companies do do this). Otherwise, it will cause environmental pollution. For a company, it would be irresponsible to do so. 　　In summary, it is not necessary to install a control valve in the vapor phase of the urine tower; a stop valve is sufficient. This is just my personal opinion for reference only. This post was last edited by lxq700918 on 2009-2-8 10:03.]

Indeed! On the high-pressure startup device, the gas-phase vent is used to displace CO2; it is only utilized during initial startup. Our device is equipped with a shut-off valve and a control valve, with the shut-off valve usually being in the open position and the control valve closed. This vent valve needs to be opened and adjusted during temperature elevation for passivation purposes, as well as during major shutdowns for displacement.

I’d like to say a few things as well: 1. The startup process for the CO2 stripping method can be carried out either at low pressure (in this case, apart from the safety valve at the gas outlet of the urea synthesis tower, there is no need to install a remotely controlled vent control valve; this is also how it is designed in current design projects) or at high pressure (in designs from before the 1990s, such a valve was used, with a designation of HPV-203). 2. In the high-pressure startup method, one function of this control valve is to displace CO2 (this is used very rarely); the other function is to release pressure directly when there is overpressure in the high-pressure system. Given today’s strict environmental regulations, few companies would be willing to bear the consequences associated with this, so this function can be disregarded. 3. During production, it is also necessary to consider the actual performance of this control valve (is there internal leakage? High maintenance frequency, etc.). Taking all of the above into account, I strongly agree with lxq700918’s opinion; adding just one shut-off valve will suffice. This post was last edited by ymtuegj12 on 2009-2-8 11:40.]

What was discussed upstairs makes sense; for the carbon dioxide stripping urea process, it is highly beneficial to install a control valve on the gas outlet pipeline of the urea synthesis tower. Although the design institute did not include such a control valve in the design, based on the many years of operational experience of some manufacturers, it is still necessary to install this control valve. First, it is necessary to clarify the function of this control valve: it is used only during startup heating for passivation and during shutdown procedures for process purging; it is not used in normal production, nor is it intended for relieving high pressure or overpressure. During startup and shutdown processes, with this control valve, it is possible to **reduce the time required for heating or cooling the synthesis tower, as well as to shorten the time needed for process purging. There are many advantages to this; saving time means improving efficiency. This post was last edited by ttlkk on 2009-2-21 11:15.]