6 replies to this topic

[panoskagiou]

In furnaces, very high pressure steam is produced from waste heat. This waste heat is actually is recovered from the convection section. By producing this very high pressure steam, then this steam is used in the cracked gas turbines and then there is steam extraction to lower steam levels, such as MP, LP, etc. MP steam for example is used from the turbines, which drive the compressors in the refrigeration cycle. The refrigeration cycle is used from different condensers in distillation columns. Consequently, why we need to reduce the energy of these columns? If we reduce the energy of these columns, that means condenser or reboiler duties reduction. That means steam reduction, which means less recovery of waste heat? Why to reduce the use of the waste of heat, since it is available?

 

 

Thank you in advance!

[PingPong]

Depending on its actual design, the operating Ethylene Plant will either export or import steam.

 

More steam production therefor requires less steam import, or more steam available for export to other process units in the complex.

[panoskagiou]

Thank you so much Ping! From your answer, I can conclude that it is always good to reduce the steam consumption in the downstream, because that means either we will export more steam or we will reduce the import steam. Also, if you know the amount of import steam is an important value comparing to the steam produced by furnaces?

[PingPong]

I am not sure what exactly you mean, but generating steam from waste heat (convection bank ethylene furnaces) is always cheaper than importing steam produced in a boiler burning fuel somewhere in the complex.

[panoskagiou]

Yeah I know that. But, my question is mostly if it is worthy to reduce the energy required in the downstream. A simple example a cryogenic distillation requires refrigerant for the condenser. That means steam for the turbines, which drives the compressors of refrigeration cycle. And my question is why to reduce this energy if it is available as waste from furnaces. Is it more clear now?

[PingPong]

As I indicated before: saving energy reduces steam import (which is a cost) or increases steam export (which has a value).

 

Licensor of ethylene plants (Linde, Lummus, Technip, et cetera) make a design that minimises the specific energy consumption as that is one of the factors that potential clients evaluate when choosing a licensor for their new plant. The value of export steam, and the cost of import steam are included in that specific energy consumption.

[panoskagiou]

Thanks Ping Pong. It is clear!