(96c) Improve Plant Flexibility for the Changing Feedstocks and Technologies

For a number of years past, we have been aware of the abundance of ethane and propane feedstocks and the low cost ethylene from the Mid-East areas.  However, there are indications recently that clients from the Mid-East are looking into cracking heavier feedstocks in order to enhance their ethylene co-product productions.

Recently, plants in the Americas are moving in somewhat different directions. The key aspects which influence our situation are as follows:

• Relative crude oil price vs NGL price ($/MMbtu) has been as high as 250%
• Increasing NGL recovery in USA is beneficial. Shale gas resourses have been increased which have extended natural gas availability. Relative cost of recovery of ethane & propane from NGL is minimal.
• FCC type technology units produce ~ 30% of the total propylene global co-product.  But the corresponding USA ratio is ~ 49% today and is anticipated to be ~58% by 2015.  Hence increasing ethane feedstock does not affect USA propylene production.

The relative ethylene production feedstock percentage ratios in USA have changed considerably in the past and are likely to keep changing in the future.    It is therefore very important for ethylene producers to be prepared to have the flexibility to process different feedstocks.        

                                                2005                             2010                             2015

Ethane                                     42                                  55                                 57

Propane                                  17                                  18                                 19

Butane                                      2                                     5                                   5

Naphtha                                  31                                  17                                 15

AGO/VGO                                 8                                    5                                    4

TOTAL (% Ethylene)            100                                100                           100

The key factor which encourages further natural gas consumption is the relative price between natural gas and crude oil.  In 2005, the ratio of $/MMbtu of NGL to Crude Oil was ~85%.  In 2010 that ratio was ~60% and is unlikely to even exceed 65% by 2015.  This is another indication for ethylene producers to have the flexibility to process different feedstocks.

From our technology point of view, there will be more and more integrated plants between refinery and petrochemicals.  The most improved refining technology is the FCC type higher propylene & ethylene production technologies.  Total olefins yields from high olefins FCC type units can be above 30% and the propylene : ethylene ratio can be well above 3:1.  

One type of technology that is gaining momentum in implementation is On- Purpose Propylene.  These technologies can be Heavier Olefins Conversion, Metathesis or Propane Dehydrogenation type to produce olefins, especially propylene.  So, it is important for refinery and petrochemical complex owners to consider how best to integrate their plants and for liquid cracker plants to consider implementing the newer technologies to improve the gross margins of their plants.

Another type of technology that may be implemented is the Refinery Off-Gas (ROG) recovery.  Since there are many valuable components in the ROG including ethylene, ethane, propylene and propane, their recovery will improve the gross margin of the plant. 

The preceding feedstock list above shows the proportional amounts of ethane and propane and butane installed in current and future units. The key olefin plant elements involved in such natural gas revamps and/or expansions are indicated basically as follows: possible feedstock pre-contaminant removal (eg. CO2 ), the furnaces, the quench oil/water towers, the CGC MW and flowrate, the cryogenic fractionation and refrigeration duties, and key recovery towers.  Based on these issues it is usually more convenient to only add a relatively small proportion of ethane as a recycle style feedstock to the naphtha cracker; but both propane and butane additional feedstocks can be much more incorporated. Related information and recommendations will be mentioned.

After deciding on the feedstock and technology to be implemented, the key question is how best to revamp the plant with minimum investment to achieve maximum flexibility?  The key is to find a reputable Licensor that is knowledgeable about the different processes such that they can provide you with the best scheme for revamp.  You can also work closely with the Licensor to identify all the potential bottlenecks to minimize the systems to be modified.  The most important consideration is to minimize downtime to implement all the modifications.  The more flexible you can modified your plant, the better you will be prepared to be profitable in the times of variable feedstock availability, feedstock cost, product values and technology changes.