Heat removal tube set, method for controlling reaction temperature and method for producing unsaturated nitrile

A heat removal tube set (particularly a heat removal water tube set), characterized in that it is configured to be arranged in a heat removal section of a fluidized bed reactor, the heat removal section being disposed in a fluidized bed layer of the fluidized bed reactor, the heat removal tube set comprising:

• at least one first heat removal tube, which comprises n1 (2<n1<30, preferably 2<n1<20, and more preferably 2<n1<10) straight pipes a extending in parallel to the central axis of the fluidized bed reactor and n1-1 connecting fittings for connecting two adjacent straight pipes a in series and providing a fluid communication between them;
• and
• at least one second heat removal tube, which comprises n2 (2<n2<30, preferably 2<n2<20, more preferably 2<n2<10) straight pipes b extending in parallel to the central axis of the fluidized bed reactor and n2-1 connecting fittings for connecting two adjacent straight pipes b in series and providing a fluid communication between them,
• a cross section is obtained by transecting along a direction perpendicular to the central axis of the fluidized bed reactor at any position of the heat removal section (where the length of the heat removal section in the direction of the central axis of the fluidized bed reactor is set as L (in m), preferably within the entire region of the length L of the heat removal section, more preferably within the region from 49% L above to 49% L below the central point of the reaction heat removal section, more preferably within the region from 45% L above to 38% L below the central point of the reaction heat removal section, more preferably within the region from 40% L above to 8% L below the central point of the reaction heat removal section),
• the number of all of the straight pipes a of the first heat removal tube (where there are a plurality of first heat removal tubes, all of the first heat removal tubes) is the same as the number of all of the straight pipes b of the second heat removal tube (where there are a plurality of second heat removal tubes, all of the second heat removal tubes), and the ratio of the total circumference Lb of the outer contours of all of the straight pipes b of the second heat removal tube (where there are a plurality of second heat removal tubes, all of the second heat removal tubes) on the cross section to the total circumference La of the outer contours of all of the straight pipes a of the first heat removal tube (where there are a plurality of first heat removal tubes, all of the first heat removal tubes) on the cross section is 1.25-2 (preferably 1.3-2 or 1.5-2).