PROCESS DESIGN AND  PLANT OPERATION RESEARCH      

             Dr. Miguel Bagajewicz

INCREASING DISTILLATE YIELDS

IN CRUDE DISTILLATION

The University of Oklahoma has developed two new technologies to enhance the yield of gas-oil and diesel in crude fractionation columns. We have tested these technology for a variety of oils. We give results for a heavy oil below. We will be very glad to test any other crude oil on request. The important remarks are:

• The gaps are maintained

•  The combined yield of atmospheric gas oil and diesel can be increased over the yield of the conventional case from 12% to 43%.

• The total amount of distillates increases 6.5% to 21% over the yield of the conventional case.

• The yield of the rest of distillates remains the same.

• It can have a similar effect in the case of units processing a light crude and using a prefractionator.

• The inventions do not rely on manipulating the furnace temperature, the overflash ratio, the pressure or other known methods to increase yield.

-         When applied to vacuum columns the distillate yield increases between 4% and 5%, when technology 2 is used.  Other additional remarks that are not central to the invention but worth mentioning are:

-         The technologies can be implemented independently or together. The implementation of one does not prevent the subsequent implementation of the other.

-         The energy expenditure associated to the implementation of these technologies is minimal and if energy retrofits are made it could lead to added savings.

-         It can be useful in debottlenecking projects.

-         The payout time for a retrofit implementation is low.

DETAILS OF CASE STUDY

1.      Feedstock and Specifications:  Crude oil, 20.0 API, 120,000 BBL/day. TBP data and light-ends composition are shown in Table 1 and 2. table 3 lists the specifications used.

                                                               Table 1: TBP Data

                                          Table 2: Light-ends Composition of Crude

2.

                                                                 Table 3: Product Specifications

3.      Comparison

                                             Table 4. Comparison between the Conventional Design and this new design

                                                 (*)  The minimum approach in exchangers used was 40 °F and a grassroots design is assumed.

The combined yields of diesel and gas oil increase by 12%, 16% and 42%, respectively! The total amount of distillates increases by 6%, 8% and 21%. Notoriously, for the case of Technology #2 the yield of gas-oil increases by 50% while the rest of the distillates yields remain the same.  It is believed that these yields can be further adjusted. The energy consumption (assuming maximum recovery for all cases) decreases a little to later increase. The behavior of energy consumption for a retrofit needs to be assessed on a case-by-case basis.

4.     

             Investment: Preliminary cost calculations have been performed and indicate a cost smaller than a million dollars. Since we do not have a large expertise in costing, we do not want to elaborate further and prefer to do this analysis on a cases-by-case basis.

5.     

            Revenues and payout:  Assuming a value of $10/bbl of difference between gas-oil and residue proces and with the yields increase of 88, 110 and 286 bbl/hr for inventions 1, 2 and their combination, the investment is far smaller than the revenues, which are around 8, 10 and 25 millions (USD) per year respectively. We also consider the energy requirement changes a minor effect. Even if the energy expenditure increases, which could be the case of a retrofit (the numbers in table 4 are for optimal grassroots designs), the amount involved is substantially smaller than the new revenues generated.

Implementation of these technologies in a vacuum column

 A conventional atmospheric column followed by a vacuum column was run. Technology 2 was used in the vacuum column only. We have carefully chosen conditions such that the temperature of the flash zone and the steam injection in the vacuum column is maintained the same. The atmospheric column remains the same in all cases.

 The resulting % increase in LVGO+HVGO for a heavy crude chosen is in the range of 2-4.2%. The range is rather smaller for a light crude (1-2%), as we expected. Yields increase due to a variety of factors and that is why we have included a range.  We have found that Technology 1 plays a less important role here and that one can apply technology 2 only, with the above good results. We have also monitored the D1160 90% point of the HVGO and it does not go up significantly (about 20 ^oF for the heavy crude and 4 ^oF for the light).  This is rather different from the case of the atmospheric unit where such a number can be maintained constant.

 Economics: Assuming a difference of $8/bbl between heavy gasoil and vacuum residue, the expected revenue can be as high as $3.5 million for the heavy crude and proportionally lower for a light. The investment is lower than the indicated in the previous case study because of the smaller throughput.

 Asphaltenes and Metals: We do not have expertise in this matter. However, we offer the following reasoning: If solid asphaltenes find their way up to the HVGO by means of pure entrainment, our technology would not have any effect because the flowrate of steam is maintained constant. If organometallic compounds reach the HVGO because of their vapor pressure, this is again not a major concern because our temperatures of the flash zone remain constant.

CONTACT

We seek support for the final development stage. We would be pleased to reveal the details of the invention and discuss future projects.  If you desire more information on this technology, please contact the Office of Technology Development, (405) 325-3800, to arrange completion of the necessary confidentiality agreements.  Once the agreement is signed and received, we will forward the complete confidential disclosure.

 Please, contact Regina K. Hewatt in the Office of Technology Development, rhewatt@ou.edu or (405) 325-3800, or Dr. Bagajewicz.  We look forward to hearing from you and working with you on such an exciting opportunity.