What's the top secret you think when it comes to LNG liquefaction process? There are different technologies, such as C3MR by Air Products, Cascade process by ConocoPhillips, Single Mixed Refrigerant SMR by Black Veatch and Dual Mixed Refrigerant DMR by Shell. For each process, there are secrets for the optimum refrigerant flow, pressure and temperature. However, the top secret among all the secrets is the mixed refrigerant compositions. In general, process engineers spend days and nights to optimize the compositions. Yet, the solution might not be found. In this video, the top secret is unveiled to teach you how you can optimize the mixed refrigerant compositions in a matter of minutes.
To illustrate my point, let's take a closer look at the single mixed refrigerant process, which is patented by Black Veatch as PRICO.
Just like all the other liquefaction process, natural gas is sent to the main heat exchanger, in which it is liquefied into LNG. The compressed mixed refrigerant is also introduced to the main heat exchanger, cooled down to about -248 F, and then expanded to about 59 psia through the J-T valve. The cold is recovered in the main heat exchanger and then it is compressed in a two stage compressor to feed the main heat exchanger, thus it forms a close mixed refrigeration loop.
For an unoptimized PRICO process, the liquefaction power for 5 MMTPA is about 279,600 kW. Some readers might recall in my other blogs, for 5 MMTPA LNG plant, the C3MR process consumes about 179,900 kW. On the surface it seems there is no way for PRICO process to compete against C3MR or Cascade process.
Process engineers have a lot of challenges to optimize the PRICO process, especially the mixed refrigerant compositions. A magic box was developed by Guofu Chen, which can utilize HYSYS optimizer to automatically optimize the mixed refrigerant compositions.
The current power consumption is 279,600, kW, now watch the magic happens. Simply click the "Start" bottom on the optimizer, the power consumption is reduced to 209,500 kW, which is almost 25% power reduction.
Now let us take a look at the heat exchanger heat release curve. As you can see, there are almost 4 points which has a minimum approach of 4 F.
The compositions optimization used to take days. Now in just one minute, you will be very confident you have an optimum design, thanks to the HYSYS optimizer. For this particular application, the optimum compositions are: 34% Methane, 28% Ethane, 0% Propane, 11.5% i-butane, 19.5% n-butane and 7.5% N2.
Thanks for watching this video. It is brought to you by Guofu Chen. More interesting topics can be found at showcase.GuofuChen.com
