Control method for avoiding a reboiler in instable transition boiling region
A transitional boiling and reboiler technology, which is applied in chemical instruments and methods, boiling devices, distillation adjustment/control, etc., can solve the problems of the heat transfer rate not rising but falling, and the temperature of the tower still falling, so as to achieve strong practical performance, The effect of reducing the flow rate of the heating medium and reducing the labor load
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Embodiment 1 and comparative example 1
[0064] The propane-propylene fractionation bottom reboiler model of a gas fractionation device is BJS500-2.5-55-6.0 / 25-4 (standard heat exchanger), the tube bundle arrangement is square and turns 45°, and the baffle form is single bow Plate, the center distance is 350mm, and the incision orientation is vertical. The mixture of propane and propylene as the reboiler medium is on the shell side of the reboiler, the operating pressure is 2.0MPaG, the critical pressure is 3.59MPaG, the inlet and outlet temperatures are 59.0°C and 59.1°C respectively, and the mass vaporization fraction is 0.25 , The heat transfer load is 3600kW.
[0065] The heating medium on the tube side of the reboiler is a gasoline component of a catalytic gasoline hydrodesulfurization unit, the operating pressure is 1.1MPaG, the flow rate is 97.6t / h, and the feed temperature is 166°C.
Embodiment 1
[0066] Embodiment 1 according to the process of the present invention ( figure 1 ) operation, Comparative Example 1 is operated according to the conventional control process of controlling the flow rate of the heating medium by the temperature of the tower kettle, and the main operating parameters and economic benefits of the two processes are compared as shown in Table 1.
[0067] Table 1 Comparison of main operating parameters and economic benefits of the two processes
[0068]
[0069] It can be seen from Table 1 that in comparative example 1, the Δt of the partial area on the boiling side of the reboiler shell side process medium is greater than Δt c , causing the reboiler at the bottom of the propane-propylene fractionation tower to operate in an unstable transitional boiling zone, the temperature of the tower still is difficult to control steadily, and the product quality pass rate is low; when embodiment 1 adopts the flow process provided by the present invention, th...
Embodiment 2 and comparative example 2
[0071] The methanol recovery tower reboiler of a catalytic light gasoline etherification unit uses a diesel component from a catalytic cracking unit as a heating medium (temperature is 192°C) to achieve the purpose of recovering heat and reducing energy consumption. The kettle temperature of the methanol recovery tower is 104.2°C. Comparative example 2 adopts the conventional control method of controlling the flow rate of the heating medium by the temperature of the tower kettle, but because the Δt in the partial area of the boiling side of the process medium in the shell side of the reboiler is 21.6°C, which is greater than the critical temperature difference of 19.1°C, the control of the methanol recovery tower is unstable. The methanol recovered at the top of the tower contains a large amount of water. When it is returned to the reaction part for further reaction, the water and the tert-amylene in the catalytic light gasoline will form tert-amyl alcohol under the action of...
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