Patent Application
20080041762
The invention will now be described in conjunction with the accompanying drawings in which:
In the drawings, like reference numerals indicate corresponding parts in the different figures.
The present invention will now be described in greater detail in connection with the figures. The present invention aims to reduce fouling in heat exchangers and other components located within a refinery. This aim is achieved by a blended base crude oil, which may consist of a whole crude oil, a blend of two or more crude oils or fractions thereof with a predetermined amount of a high solvency dispersive power (HSDP) crude oil. The addition of HSDP crude oil mitigates both asphaltene induced fouling and particulate induced/promoted fouling. The high Sbn of these HSDP crude oils allows for the enhanced solubility of any asphaltenes in the rest of the crude oils and/or blends. The presence of TAN is believed to help disperse the particulates in the crude oil blend which prevents them from adhering to the heated surface. In order to achieve the reduction in fouling, the HSDP crude oil should have a total acid number (TAN) of at least 0.3. Higher TAN levels may result in improved fouling reduction and mitigation. The HSDP crude oil should have a solubility blending number (SBN) of at least 75. Higher SBN levels may result in improved fouling reduction and mitigation. The volume of HSDP crude oil necessary in the blended crude oil will vary based upon the TAN and/or SBN values of the HSDP crude oil. The higher TAN and/or SBN values of the HSDP crude oil, the lower the volume of HSDP crude oil necessary to produce a blended crude oil that will reduce and/or mitigate both asphaltene induced fouling and particulate induced fouling and/or promotion in refinery components, including but not limited to heat exchangers and the like. The HSDP crude oil preferably makes up between five percent and fifty percent of the total volume of the blended crude oil.
The blended crude oil is then processed within the refinery. The blended crude oil exhibits improved characteristics over the base crude oil. Specifically, the blended crude oil exhibits a significant reduction in fouling over base crude which contain particulates. This results in improved heat transfer within the heat exchanger and a reduction in overall energy consumption.
During the constant surface temperature testing, foulant deposits and builds up on the heated surface. The foulant deposits are thermally degraded to coke. The coke deposits cause an insulating effect that reduces the efficiency and/or ability of the surface to heat the oil passing over it. The resulting reduction in outlet bulk fluid temperature continues over time as fouling continues. This reduction in temperature is referred to as the outlet liquid ΔT or ΔT and can be dependent on the type of crude oil/blend, testing conditions and/or other effects, such as the presence of salts, sediment or other fouling promoting materials. A standard Alcor fouling test is carried out for 180 minutes. The total fouling, as measured by the total reduction in outlet liquid temperature is referred to as ΔT180 or dT180.
The present inventors have found that the addition of a crude oil having a high TAN and/or high SBN to the base crude oil reduces particulate-induced fouling. The degree of fouling reduction appears to be a function of the TAN level in the overall blend. This is believed to be due to the ability of the naphthenic acids to keep particulates present in the blends from wetting and adhering to the heated surface, where otherwise promoted and accelerated fouling/coking occur. Most high TAN crudes oils also have very high SBN levels, which have been shown to aid in dissolving asphaltenes and/or keeping them in solution more effectively which also reduces fouling that would otherwise occur due to the incompatibility and near-incompatibility of crude oils and blends. These crude oils are classified as high solvency dispersive power (HSDP) crude oils. There is a notable reduction in fouling when a predetermined amount of HSDP crude oil is added to the base crude, where the HSDP crude oil has a TAN as low as 0.3 and a SBN as low as 75. The predetermined amount of HSDP crude oil may make up as low as five percent (5%) of the total volume of the blended crude oil (i.e., base crude oil+HSDP crude oil).
Sample tests were performed to determine the effect the addition of HSDP Crude Oils A and/or B to a HSHA base crude oil has on the fouling of the base oil. The results are illustrated in
Sample tests were performed to determine the effect the addition of HSDP Crude Oils A and B on the fouling of the base oil. The results are illustrated in
Sample tests were also performed to determine the effect the addition of the HSDP Crude Oil A to a base oil containing either LSLA whole crude oil or HSHA blended crude oil has on the fouling of the base oil. The HSDP A crude oil having an approximate TAN of 4.8 and a SBN of 112. The results associated with the impact of the HSDP A on the HSHA blend are illustrated in
As shown in
The above illustrative examples of the benefits of the present invention were based upon the use of examples A and B crude oils as the HSDP crude oil. The present invention is not intended to be limited to only these examples of HSDP crude oils. Other HSDP crude oils having an approximate TAN of at least 0.3 and a SBN of at least 75 will achieve reductions in fouling.
It will be apparent to those skilled in the art that various modifications and/or variations may be made without departing from the scope of the present invention. It is intended that all matter contained in the accompanying specification shall be interpreted as illustrative only and not in a limiting sense. While the present invention has been described in the context of the heat exchanger in a refinery operation, the present invention is not intended to be so limited; rather it is contemplated that the present invention is suitable for reducing and/or mitigating fouling in other refinery components including but not limited to pipestills, cokers, visbreakers and the like. Furthermore, it is contemplated that the use of a HSDP crude oil, as described in connection with the present invention, may be combined with other techniques for reducing and/or mitigating fouling. Such techniques include, but are not limited to, (i) the provision of low energy surfaces and modified steel surfaces in heat exchanger tubes, as described in U.S. patent application Ser. Nos. 11/436,602 and 11/436,802, the disclosures of which are incorporated herein specifically by reference, (ii) the use of controlled mechanical vibration, as described in U.S. patent application Ser. No. 11/436,802, the disclosure of which is incorporated herein specifically by reference (iii) the use of fluid pulsation and/or vibration, which may be combined with surface coatings, as described in U.S. Provisional Patent Application No. ______ (Reference No. 2006EM009), filed on Jun. 23, 2006, entitled “Reduction of Fouling in Heat Exchangers,” the disclosure of which is incorporated herein specifically by reference (iv) the use of electropolishing on heat exchanger tubes and/or surface coatings and/or modifications, as described in U.S. Provisional Patent Application No. 60/751,985, the disclosure of which is incorporated herein specifically by reference and (v) combinations of the same, as described in U.S. Provisional Patent Application No. 60/815,844, filed on Jun. 23, 2006, entitled “A Method of Reducing Heat Exchanger Fouling in a Refinery,” the disclosure of which is incorporated herein specifically by reference. Thus, it is intended that the present invention covers the modifications and variations of the method herein, provided they come within the scope of the appended claims and their equivalents.
