1. Quick 🧵why you cannot run the same amount of light crude in a refinery that is designed to run medium or heavy crude. Why US need sCanadian and cant run US crud eoil.
The problem is the overhead system cannot take the volume of light ends that are produced.
The problem is the overhead system cannot take the volume of light ends that are produced.
2. It all starts in the pipework that takes the light ends from the distillation coilumn to the downstream secondary units.
The most important factor that this overhead pipework is designed to do is to minimise the pressure drop between the CDU and downstream
The most important factor that this overhead pipework is designed to do is to minimise the pressure drop between the CDU and downstream
3. Now if you introdcue more lightends by running light sweet crude instead of heavy sour. There are more light ends than normal. To get the extra out of the column you need one of two things to happen
4. The first is higher pressure in the column to compress the extra amount which is a gas down the line.
Now the top of CDU is designed to run ajust above atmospheric pressure at the top of the column. This is done because at low pressure seperation is much easier to acheive.
Now the top of CDU is designed to run ajust above atmospheric pressure at the top of the column. This is done because at low pressure seperation is much easier to acheive.
5. The higher the pressure the cut points of products changes and is much more difficult to achieve product quality
Compressing also means temperature of the gas gets higher which makes it more difficult to cool to storage temp in the heat exchanger downstream
Compressing also means temperature of the gas gets higher which makes it more difficult to cool to storage temp in the heat exchanger downstream
6. The second way to get more out of the CDU is by increasing the velocity in the pipe, i.e. make the gas move faster.
the problem with this is the faster a liquid(gas goes the more pressure drop it has per metre of line. This means again you need a higher pressure in the CDU
the problem with this is the faster a liquid(gas goes the more pressure drop it has per metre of line. This means again you need a higher pressure in the CDU
7. It also means that not only is it hotter leaving duue to a higher pressure, the gas will also stay less time in the heat exchanger to cool. resulting in the same problem as with compressing.
8. This is why crude quality is such an important factor in a refinery and why if outside the upper bounds of the light crude in the blend, the throughput capacity of the column falls
It is why, you cannot swap US shale for Canadian Oil sands
US oil independence is a myth
It is why, you cannot swap US shale for Canadian Oil sands
US oil independence is a myth
9. yes you can spend millions to upgrade your overhead system. But it also means changing your downstream equipment as well. In old refineries this may not be feasible. It will also take years to change
So, please Americans, stop telling me you can use US oil instead. You cannot
So, please Americans, stop telling me you can use US oil instead. You cannot
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