Regarding the elasticity issue of the device
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I would like to ask: the elasticity of a process unit is generally around 50~120%. The upper limit of 120% is easy to understand, but what factors usually determine the lower limit of 50%?
It is determined by the process reaction load, as well as the bottlenecks resulting from the low-load operation of key equipment: the performance of compressors, pumps, etc., has an impact on this
Many factors are limiting it. In addition to what was mentioned above, there is also the minimum operating line for the tower; if it is too small, the tower may not be able to function properly, such as in cases of leakage in sieve plate towers. The reaction temperature of the reactor must be maintained; if it is too low, it becomes impossible to ensure the appropriate reaction temperature, among other issues. There’s also the issue of cost-effectiveness; it’s not economical to operate it when it’s too small.
With unsold products and a weak market, when it’s necessary to control production, only 50% of the capacity is utilized, which means the operation rate is insufficient.
For units such as sulfur recovery, which are often operated at low load levels, the lower limit of operational flexibility is typically set at 30%.
There must be many constraints in such a low-load situation, right? Or rather, are two sets of equipment connected in parallel, with only one set being used when the production capacity is low?
Leakage from the tower, equipment vibration, the heat exchange network failing to reach the desired temperature – there are many issues!
Also, when starting a new unit for the first time, it is generally required to operate at low load first, and only after stable operation should the load be increased! ! ! ! ! ! ! ! ! ! ! !
All devices have a low-load mode; it’s impossible for them to operate at full load right from the start
There are many influencing factors; for example, in distillation columns and packed columns, operation is still possible even at 20%, while the valve plates in floating valve columns may fail early on.
The lower limit of the load is mainly related to the market; when the market price system is poor and operating at full capacity results in heavy losses, the load on the equipment will be lower. When operating at the lower limit, the energy consumption per unit of product is higher than under normal load; therefore, when product prices are good, operations are carried out at full capacity.