【Ethylene cracking】Why are the convection modules of Sinopec’s cracking furnaces so tall?

The convection section is primarily for heat exchange, with no reaction taking place

You can tell by looking at the flue gas outlet temperature; the heights should be more or less the same. The elevation of the drum layer is around 52 meters, I guess.

Through careful organization and thorough coordination by the contractors of Sinopec Engineering Company, as well as close cooperation between the installation team of Shijian Company and the lifting company, and after 15 days of intense collaborative effort by the workers involved in installation, lifting, and scaffolding construction, the furnace tube box modules for the convection chambers of Reactors No. 3 and No. 6 in the 800,000 tons per year ethylene steam cracking unit of the Zhongke Refining and Chemical Project were successfully lifted and installed on April 18th and 21st respectively. The steam cracking unit is equipped with seven cracking furnaces in total: furnaces No. 1 and No. 2 have the same volume, furnaces No. 3 to No. 6 also have the same volume, while furnace No. 7 is of a different type. The first batch to arrive at the site consisted of 16 sets of convection chamber modules for reactors No. 3 and No. 6, with a total weight of 1,200 tons. For each pyrolysis reactor, the largest module in the convection chamber’s tube bank measured 15.25 meters in length, 2.44 meters in width, 3.14 meters in height, and weighed 133 tons. The installation elevation of the convective chamber furnace tube box modules ranges from 18 meters to 40 meters, presenting challenges such as high lifting difficulties and stringent technical requirements. The various tube box modules on each furnace are connected together using setting bolts; after installation and alignment, the two box assemblies are welded shut in accordance with the requirements specified in the drawings.

The elevation of the convection section of our cracking furnace ranges from 17.72m to 33.92m, and it includes the raw material preheating section, economizer section, super-high pressure steam superheating section 1 and 2, as well as the section for mixing raw materials with dilution steam for preheating. The cracking furnaces in the newly built ethylene plants are likely to have higher requirements regarding the Nox content in the flue gas; therefore, it is assumed that a space has been reserved near the raw material preheating section for installing denitration modules. In this case, the heights are roughly the same.

They’re more or less the same height; it’s just that the outer frame isn’t in place, which makes one stand out among the others. The attached figure shows Zhejiang Petrochemical’s cracking furnace.

That’s why it stands out from the others; it has more modules. Sinopec Refining has eight modules, and as mentioned above, some pyrolysis units have only six modules

Now, denitration devices must be added, installed in the convection section.

Environmental considerations, along with energy recovery