Heating of the urea synthesis tower

1. Heating rate 2. Temperature difference between upper and lower parts, as well as between the inside and outside 3. Prevention of liquid accumulation 4. When heating is interrupted for some reason, it is necessary to allow air to flow in and out promptly

What should the temperature increase rate be kept below?

Our company specifies a heating rate of 10–15 degrees per hour, and a pressure increase rate of 2.5 MPa per hour.

Here’s a plan for you: I. Preparation work 1. Connect the instruments and turn on the computer to check whether all temperature measurement points in the synthesis tower are functioning properly. 2. Valves to be closed: the main high-pressure steam valve, the second shut-off valve at the top of the synthesis tower, the first shut-off valve at the top of the synthesis tower, the insulation steam valve for the synthesis tower, the top drain valve, and the two steam valves used for leak detection at the bottom of the tower. 3. Valves to be opened: the first shut-off valve at the outlet of the synthesis tower, the single-line shut-off valve for the carbon dioxide pipeline at the bottom of the synthesis tower, and the on-site discharge valve at the tower bottom. Contact the dispatcher to send steam and introduce it. II. Preheating of steam entering the synthesis tower 1. Turn the preheating steam valve 1/10 turn, open the preheating check valve and the first preheating angle valve, and observe the temperature changes in the upper part of the synthesis tower. Once the temperature in that upper area rises suddenly, use this temperature as a reference to control the rate of temperature increase (6–8 degrees Celsius per hour). Adjust the steam valve accordingly based on the temperature changes, ensuring that the adjustment range is not too large. 2. Two hours later, the temperature at the upper part of the synthesis tower rises sharply; in this case, the heating rate should be controlled based on the temperature at the upper part of the tower (6–8 degrees Celsius per hour, the same applies hereafter). 3. Four hours later, the temperature in the middle section of the synthesis tower rises sharply; at this point, the heating rate should be controlled based on the temperature in that middle section. 4. Four hours later, the temperature at the lower part of the synthesis tower increased suddenly; therefore, the heating rate was controlled based on the temperature at the lower section of the tower wall. 5. The first stage of temperature rise in the synthesis tower is characterized by a sudden increase in the temperature at the lower part of the tower wall, along with a corresponding rise in the temperature at the upper part of the tower to 100 degrees Celsius. IV. Phase 2 1. Gradually reduce the flow rate of the valve at the bottom of the tower, increase the pressure inside the synthesis tower step by step, control the temperature in the upper part of the synthesis tower, and ensure a uniform increase in temperature in the lower part as well; the rate of temperature increase should be 8–10 degrees Celsius per hour. 2. Appropriately increase the steam valve at the top of the tower to raise the temperatures at the top and bottom of the synthesis tower to 150 degrees Celsius, while making sure to continuously remove the steam condensate from within the synthesis tower. 3. Once the synthesis tower has been properly preheated, if it is not started immediately, the second high-pressure inlet valve can be closed to maintain the temperature of the synthesis tower at 150 degrees Celsius. 4. Before starting the ammonia cycle, close the second high-pressure check valve feeding into the tower, as well as the bottom check valve and the discharge valve. 5. When raising the temperature, it is strictly prohibited to open the steam control valve widely; even if the temperature remains unchanged for a long time, one must wait patiently. The temperature difference between the temperature inside the tower and the wall temperature should be kept within 50°C.

The temperature rise should be less than 12 per hour; pay attention to the temperature difference between the top and bottom of the urine tower, as well as to the drainage of condensate water

The heating rate is 6–8 degrees per hour, with a maximum of 12 degrees per hour; the temperature difference between the top and bottom of the tower is less than 30 degrees

What types of manufacturing processes are you talking about? I wonder how the temperature differences between the upper and lower parts, as well as inside and outside, of the tower in the carbon dioxide stripping process are controlled The heating and pressure increase rates mainly depend on the material of the equipment; generally, the former is less than or equal to 12 degrees per hour, while the latter is 3.0 MPa per hour.

I guess most of what is mentioned refers to aqueous solutions! Is there a CO2 stripping method that involves directly adding steam to raise the temperature? Our plant has always used water for vaporization; this way of raising the temperature seems a bit incorrect.

In fact, all synthesis towers are the same in this regard – it is necessary to control the rate of temperature and pressure increase in order to protect the synthesis tower

Generally, heating is started using low-pressure steam as required; I wonder if this is being followed as specified? What if there are changes? How would that be?

I’ll be more detailed; please feel free to correct me: The main issue is that the utilization of heat is not efficient – in effect, secondary steam is being used. But if medium-pressure steam is used directly, controlling the rate of temperature increase becomes a problem, especially below 100 degrees. Also, the point where water is added to our plant is the high-pressure ammonium methanol condenser, which can easily lead to a shortage of water in the stripping tower and affect the passivation process. I’m not sure about the specific point at which air and steam are added for temperature-based passivation In our plant, air is introduced into the carbon dioxide pipeline, while water is added to the high-pressure condenser; it is then heated into steam by steam on the shell side. This post was last edited by cthlj2007 on 2009-3-9 23:37.]

Here is a link with a more detailed discussion: http://bbs.hcbbs.com/thread-317626-1-6.html