CRUDE UNIT OVERHEAD CORROSION CONTROL USING MULTI AMINE
BLENDS
FIELD OF THE INVENTION
[0001] The present disclosure pertains to technical field of refinery processing of crude oil. In
particular, the present disclosure pertains to inhibiting corrosion of overhead equipment of a
distillation unit in petroleum refinery.
BACKGROUND OF THE INVENTION
[0002] Background description includes information that may be useful in understanding the
present invention. It is not an admission that any of the information provided herein is prior art
or relevant to the presently claimed invention, or that any publication specifically or implicitly
referenced is prior art.
[0003] Hydrocarbon feed stocks such as petroleum crudes, gas oil, etc. are subjected to various
processes in order to isolate and separate different fractions of the feedstock. The lower boiling
fractions, including naphtha, from which gasoline is derived, are recovered as an overhead
fraction from the distillation column. The fractions with intermediate volatility are withdrawn
from the distillation column as sidestreams. Sidestream products include kerosene, jet fuel, diesel
fuel, and gas oil. The overhead and sidestream products are cooled, condensed and sent to other
units to be processed into final products.
[0004] The distillation equipment is liable to corrosive activity of acids such as HCl, H2S,
organic acids, and H2CO3. HCl, the most troublesome corrosive material, is formed by
hydrolysis of calcium and magnesium chlorides originally present in crude oils. The problem of
corrosion caused by these acidic components as water condenses in the overhead condensing
system of distillation columns. The water condensate formed contains a significant concentration
of these acidic components, and high concentrations of the same render the pH of the water
condensate highly acidic and, of course, dangerously corrosive. Accordingly, neutralizing
treatments have been used to render the pH of the condensate alkaline to thereby minimize acidbased
corrosive attack at those regions of the apparatus with which this condensate is in contact.
[0005] The rate of corrosion is directly related to the concentration of hydrogen ions in the water
condensate. A particularly difficult aspect of the problem is that corrosion occurs above and in
the temperature range of the initial condensation of water. The term “initial condensate” as used
herein indicates a phase formed when the temperature of the surrounding environment reaches
-3-
the dew point of water. At this point a mixture of liquid water, hydrocarbon, and vapor may be
present. Such initial condensate may occur within the distilling column itself or in subsequent
columns. The top temperature of the fractionating column is normally maintained above the dew
point of water. The initial water condensate formed contains a high percentage of HCl. Due to
high concentration of acids dissolved in the water, the pH of the first condensate is quite low and
the condensed water is highly corrosive.
[0006] Several treatment methods using different types of amines, including highly basic
amines, have been proposed in the art to control or inhibit corrosion that ordinarily occurs at the
point of initial condensation within or after the distillation unit. However, treatment methods
utilizing the known amines have not been successful and specific problems have been reported in
connection with the use of these amines for treating the initial condensate. For example, US
patent No. 7,381,319 states that use of highly basic amines such as, morpholine,
methoxypropylamine, ethylenediamine, monoethanolamine, hexamethylenediamine, etc. for
treating the initial condensate has a problem relating to the resultant hydrochloride salts of these
amines which tend to form deposits in various parts of the distillation unit and thereby cause both
fouling and under-deposit corrosion problems.
[0007] The inability of some neutralizing amines to condense at the dew point of water tend to
form a highly corrosive initial condensate and thereby leads to formation of hydrochloride or
sulfide salts of those neutralizing amines on metallic surfaces of the distillation columns. The
salts appear before the dew point of water result in fouling and under-deposit corrosion, often
referred to as "dry" corrosion.
[0008] Further, it is difficult to assess the corrosion rate and determining the required dosage of
amines during the operating conditions of overhead condensing system. Traditional treatment
methods optimize the amine dosage depending on boot water pH, chloride and iron counts, but
these methods do not provide information as to optimal dosage of amines for system conditions.
[0009] There is thus a need in the art for a new and improved neutralizing agent that facilitates
effective neutralization of acidic components at the point of initial condensation and/or
minimizes or eliminates deposits of salts on metal surfaces of distillation columns and thereby
avoids formation of fouling and under-deposit corrosion. Also, there is a need in the art for a
system and method to assess the corrosion rate and to optimize the dosage of neutralizing agents
during the operating conditions of overhead condensing system.
[0010] The present invention satisfies the existing needs, as well as others, and generally
overcomes the deficiencies found in the prior art.
-4-
OBJECTS OF THE INVENTION
[0011] It is an object of the present disclosure to provide a neutralizing agent for efficiently
neutralizing acidic components in overhead condensing system of distillation columns to inhibit
corrosion of the same.
[0012] It is a further object of the present disclosure to provide a neutralizing agent for
efficiently neutralizing acidic components at the point of initial condensation of water in
overhead condensing system.
[0013] It is another object of the present disclosure to provide a neutralizing agent for efficiently
neutralizing acidic components in overhead condensing system while preventing deposits of
unwanted salts on metallic surfaces thereof.
[0014] It is another object of the present disclosure to provide a method for inhibiting corrosion
in overhead condensing system of distillation columns.
[0015] It is another object of the present disclosure to provide a method for eliminating or
minimizing deposits of unwanted salts on metallic surfaces of overhead condensing systems.
[0016] It is another object of the present disclosure to provide a method for assessing corrosion
rate and optimizing dosage of neutralizing agents during operating conditions of overhead
condensing system.
SUMMARY OF THE INVENTION
[0017] The present disclosure provides a method for inhibiting corrosion on internal metal
surfaces of an overhead condenser of a crude distillation unit in which hydrocarbons, water and
amine hydrochlorides condense, the method comprising adding to the overhead condenser an
amine composition in an amount and at a rate sufficient to maintain the pH of water condensate
in the condenser above a pH of about 5-6.5, the amine composition consisting of a mixture of
monoethanloamine, methoxypropyl amine, morpholine and cyclohexylamine in a weight ratio
(vol %) ranging from about 25:30:25:20 to about 30:40:15:15.
[0018] The present disclosure provides a method for inhibiting corrosion on internal metal
surfaces of an overhead condenser of a crude distillation unit during fractionation of a mixture
comprising hydrocarbons, water and amine hydrochlorides, wherein the condenser has an upper
condensing zone which operates at temperatures below the water dew point of the mixture and a
lower condensing zone which operates at temperatures above the water dew point of the mixture,
-5-
the method comprising: adding to the condenser in the upper condensing zone an amine
composition in an amount sufficient to maintain the pH of water condensate in the condenser
above a pH of about 5-6.5, wherein the amine composition consists of a mixture of
monoethanloamine, methoxypropyl amine, morpholine and cyclohexylamine in a weight ratio
(vol %) ranging from about 10:20:40:30 to about 5:15:30:50.
[0019] According to one embodiment of the present disclosure, the method for inhibiting
corrosion on internal metal surfaces of an overhead condenser of a crude distillation unit can
utilize an overhead corrosion simulator to assess corrosion as a function of pH and chloride
concentration.
[0020] In yet another embodiment of the present disclosure, the method for inhibiting corrosion
on internal metal surfaces of an overhead condenser of a crude distillation unit can utilize an
electrochemical method for prediction of corrosion rate.
[0021] Various objects, features, aspects and advantages of the inventive subject matter will
become more apparent from the following detailed description of preferred embodiments, along
with the accompanying drawing figures in which like numerals represent like components.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] The accompanying drawings are included to provide a further understanding of the
present disclosure, and are incorporated in and constitute a part of this specification. The
drawings illustrate exemplary embodiments of the present disclosure and, together with the
description, serve to explain the principles of the present disclosure.
[0023] FIG. 1 is a graph illustrating neutralizing capacity of six amine compositions at 50 ppm
chloride concentration in accordance with embodiments of the present disclosure.
[0024] FIG. 2 is a graph illustrating neutralizing capacity of six amine compositions at 100 ppm
chloride concentration in accordance with embodiments of the present disclosure.
[0025] FIG. 3 is a graph illustrating neutralizing capacity of six amine compositions at 200 ppm
chloride concentration in accordance with embodiments of the present disclosure.
[0026] FIG. 4 is a graph illustrating neutralizing capacity of an amine composition of the present
disclosure against ethanolamine at 50 ppm chloride concentration.
[0027] FIG. 5 is a graph illustrating neutralizing capacity of an amine composition of the present
disclosure against methoxypropyl amine (MOPA) at 50 ppm chloride concentration.
-6-
[0028] FIG. 6 is a graph illustrating neutralizing capacity of an amine composition at 200 ppm
chloride concentration, at different temperatures in accordance with embodiments of the present
disclosure.
[0029] FIG. 7 is a graph illustrating corrosion rates of carbon steel at various chloride
concentrations in accordance with embodiments of the present disclosure.
[0030] FIG. 8 is a graph illustrating corrosion rates of carbon steel at various pH concentrations
and determination of optimal dosage of amine composition in accordance with embodiments of
the present disclosure.
DETAILED DESCRIPTION OF THE INVENTION
[0031] The following is a detailed description of embodiments of the disclosure depicted in the
accompanying drawings. The embodiments are in such detail as to clearly communicate the
disclosure. However, the amount of detail offered is not intended to limit the anticipated
variations of embodiments; on the contrary, the intention is to cover all modifications,
equivalents, and alternatives falling within the spirit and scope of the present disclosure as
defined by the appended claims.
[0032] Each of the appended claims defines a separate invention, which for infringement
purposes is recognized as including equivalents to the various elements or limitations specified
in the claims. Depending on the context, all references below to the "invention" may in some
cases refer to certain specific embodiments only. In other cases it will be recognized that
references to the "invention" will refer to subject matter recited in one or more, but not
necessarily all, of the claims.
[0033] Unless the context requires otherwise, throughout the specification which follow, the
word “comprise” and variations thereof, such as, “comprises” and “comprising” are to be
construed in an open, inclusive sense that is as “including, but not limited to.”
[0034] Reference throughout this specification to “one embodiment” or “an embodiment” means
that a particular feature, structure or characteristic described in connection with the embodiment
is included in at least one embodiment. Thus, the appearances of the phrases “in one
embodiment” or “in an embodiment” in various places throughout this specification are not
necessarily all referring to the same embodiment. Furthermore, the particular features, structures,
or characteristics may be combined in any suitable manner in one or more embodiments.
[0035] As used in this specification and the appended claims, the singular forms “a,” “an,” and
“the” include plural referents unless the content clearly dictates otherwise. It should also be
-7-
noted that the term “or” is generally employed in its sense including “and/or” unless the content
clearly dictates otherwise.
[0036] In some embodiments, the numbers expressing quantities of ingredients, properties such
as concentration, reaction conditions, and so forth, used to describe and claim certain
embodiments of the invention are to be understood as being modified in some instances by the
term “about.” Accordingly, in some embodiments, the numerical parameters set forth in the
written description are approximations that can vary depending upon the desired properties
sought to be obtained by a particular embodiment. In some embodiments, the numerical
parameters should be construed in light of the number of reported significant digits and by
applying ordinary rounding techniques. Notwithstanding that the numerical ranges and
parameters setting forth the broad scope of some embodiments of the invention are
approximations, the numerical values set forth in the specific examples are reported as precisely
as practicable. The recitation of ranges of values herein is merely intended to serve as a
shorthand method of referring individually to each separate value falling within the range.
[0037] Unless otherwise indicated herein, each individual value is incorporated into the
specification as if it were individually recited herein. All methods described herein can be
performed in any suitable order unless otherwise indicated herein or otherwise clearly
contradicted by context. The use of any and all examples, or exemplary language (e.g. “such
as”) provided with respect to certain embodiments herein is intended merely to better illuminate
the invention and does not pose a limitation on the scope of the invention otherwise claimed. No
language in the specification should be construed as indicating any non-claimed element
essential to the practice of the invention.
[0038] The headings and abstract of the invention provided herein are for convenience only and
do not interpret the scope or meaning of the embodiments.
[0039] Reference will now be made in detail to the exemplary embodiments of the present
invention, examples of which are illustrated in the accompanying drawings. Wherever possible,
the same reference numbers are used in the drawings and the description to refer to the same or
like parts.
[0040] The following discussion provides many example embodiments of the inventive subject
matter. Although each embodiment represents a single combination of inventive elements, the
inventive subject matter is considered to include all possible combinations of the disclosed
elements. Thus if one embodiment comprises elements A, B, and C, and a second embodiment
-8-
comprises elements B and D, then the inventive subject matter is also considered to include other
remaining combinations of A, B, C, or D, even if not explicitly disclosed.
[0041] Various terms as used herein are shown below. To the extent a term used in a claim is not
defined below, it should be given the broadest definition persons in the pertinent art have given
that term as reflected in printed publications and issued patents at the time of filing.
[0042] In one aspect, the present disclosure provides a method for inhibiting corrosion on
internal metal surfaces of an overhead condenser of a crude distillation unit in which
hydrocarbons, water and amine hydrochlorides condense, the method comprising adding to the
overhead condenser an amine composition in an amount and at a rate sufficient to maintain the
pH of water condensate in the condenser above a pH of about 5, the amine composition
consisting of a mixture of monoethanloamine, methoxypropyl amine, morpholine and
cyclohexylamine in a weight ratio (vol%) ranges from about 10:20:40:30 to about 5:15:30:50.
[0043] As used herein, the term “corrosion inhibition” can refer to any cessation, prevention,
abatement, reduction, suppression, lowering, controlling or decreasing of corrosion, rusting,
oxidative decay, etc. Similarly, the term “neutralize” can refer to such corrosion inhibition by
reducing the acidity of the chemicals or components in the overhead condensing systems by
raising pH from acidity to basicity to some measurable extent. Furthermore, the nature of the
metal surfaces protected in the methods of this disclosure is not limited and may include iron
alloys, copper alloys, nickel alloys, titanium alloys, and these metals in unalloyed form as well,
etc.
[0044] The amine composition of the present disclosure is a mixture of four amines wherein the
amines can be monoethanloamine, methoxypropyl amine, morpholine and cyclohexylamine.
This amine composition can have relatively stronger basicity and can be more resistant to
hydrochloride salt formation than currently used amine neutralizers. The amine composition can
be optimally custom formulated with different weight ratios of the amine components to achieve
the desired pH elevation to corrosion protect the overhead condensing systems of distillation
columns. The amine composition of the present disclosure can facilitate greater neutralization of
corrosive acids in overhead condensing systems without increasing the potential to form
corrosive salts with hydrogen chloride. FIG. 4 and FIG. 5 depict neutralizing capacity of the
amine composition against ethanolamine and methoxypropyl amine (MOPA) at 50 ppm chloride
concentration in accordance with embodiments of the present disclosure.
-9-
[0045] In an exemplary embodiment, the weight ratio of monoethanloamine, methoxypropyl
amine, morpholine and cyclohexylamine can preferably be about 10:20:40:30 to about
5:15:30:50 respectively by weight of total weight of the amine composition.
[0046] The amine composition of the present disclosure can elevate pH of the water condensate
to corrosion-safe levels across the entire condensation zone, from the point of initial water
condensation, where highest chloride concentrations and lowest pH's are observed, through to
the overhead condensate drums where the overhead is totally condensed and bulk sour water is
accumulated, and at all intermediate water condensation points in the system. The amine blends
(compositions) of the present disclosure behaves as mixed type inhibitors i.e., they can retard the
corrosion reaction by blocking both anodic and cathodic sites of the metal.
[0047] The amine composition may be added to the overhead condenser system at a rate
sufficient to maintain the pH of water condensate in the condenser at a pH of about 5.0 or higher.
The desired pH range for all points in the overhead condenser can range from about 5 to about
7.5, and preferably range from about 5 to about 6.5. The amount of amine composition may
range from about 1 to about 10,000 ppm, based on the amount of water condensate. In an
exemplary embodiment, the amount of amine composition may range from about 10 to about
200 ppm.
[0048] The amine composition of the present disclosure, in small amounts, can effectively
elevate pH of the water condensate to corrosion-safe levels and thereby reduce the cost of the
treatment, eliminate operating problems due to high amine concentrations in downstream units,
and mitigate or inhibit deposition of amine hydrochloride salt. FIGs. 1, 2 and 3 illustrate
neutralizing capacity of different amine compositions at 50 ppm, 100 ppm and 200 ppm chloride
concentration respectively, in accordance with embodiments of the present disclosure. Further,
the amine composition(s) can be suitable for overhead condensing systems with water wash
provision and also for systems without water wash provision.
[0049] FIG. 6 illustrates neutralization of water containing 200 ppm chloride concentration at
different temperatures using the amine composition(s) in accordance with embodiments of the
present disclosure. As shown in FIG. 6, the amine composition BPNA-5 can effectively
neutralize the water condensate even at very low temperature while preventing deposits of
unwanted salts on metal surfaces of the overhead equipment. Further, corrosion can be controlled
even at higher dosages of the amine composition of the present disclosure.
[0050] The amine components that form part of the amine composition of the present disclosure
are readily available and do not require elaborate or expensive handling procedures to meet
-10-
environmental and safety concerns. The amine composition can be thermally stable at
temperatures it will encounter during fractionation of crude oil. The amine composition can be
volatile enough to be in the gas phase at conditions upstream of the condensation zone, and also
can condense along with water in the condensing zone. Further, it can be more soluble in water
than oil.
[0051] In another aspect, the present disclosure provides a method for inhibiting corrosion on
internal metal surfaces of an overhead condenser of a crude distillation unit during fractionation
of a mixture comprising hydrocarbons, water and amine hydrochlorides, wherein the condenser
has an upper condensing zone which operates at temperatures below the water dew point of the
mixture and a lower condensing zone which operates at temperatures above the water dew point
of the mixture, the method comprising: adding to the condenser in the upper condensing zone an
amine composition in an amount sufficient to maintain the pH of water condensate in the
condenser above a pH of about 5, wherein the amine composition consisting of a mixture of
monoethanloamine, methoxypropyl amine, morpholine and cyclohexylamine in a weight ratio
ranges from about 10:20:40:30 to about 5:15:30:50.
[0052] In an embodiment, the method for inhibiting corrosion on internal metal surfaces of an
overhead condenser of a crude distillation unit can utilize an overhead corrosion simulator to
assess corrosion rate as a function of pH and chloride concentration. The overhead corrosion
simulator can be conveniently and effectively used to get data such as, water condensation rate,
pH/chloride concentration Vs corrosion rate and corrosion rate Vs temperature profiles.
[0053] The overhead corrosion simulator can have a liquid module, a vaporizer module and a
condenser module. The liquid module can include a hydrocarbon module and an aqueous
solution module and it can be configured to include a feed vessel, peristaltic pump with
adjustable flow rate and an inlet and outlet tube. The flow rates of hydrocarbon and aqueous
solutions can be adjusted according to the experiment requirements. The vaporizer module can
have a separate module for each hydrocarbon and aqueous solutions. The temperature of the
vaporizer module can be adjusted independently to attain desired vaporization of the
hydrocarbon and aqueous solutions. The condenser module can be configured to receive and
condense the vapors of hydrocarbon and aqueous solutions. The condenser module can further
include a provision to hang corrosion coupons at various locations and a thermowell with
temperature probes for measuring the temperature of the vapors. The overhead corrosion
simulator can simulate the upper trays and overhead condensing system of a crude oil distillation
-11-
unit. The weights of the coupons can be measured before and after the experiment to determine
the corrosion rates.
EXAMPLES
[0054] The present disclosure is further explained in the form of following examples. However,
it is to be understood that the foregoing examples are merely illustrative and are not to be taken
as limitations upon the scope of the invention. Various changes and modifications to the
disclosed embodiments will be apparent to those skilled in the art. Such changes and
modifications may be made without departing from the scope of the invention.
Example 1: Neutralization capacity of Amine blends (compositions) at varying chloride
concentrations:
[0055] Different amine blends (compositions) were prepared with their composition as provided
in Table-1 below and were tested against varying chloride concentrations. The results of the
experiments are as illustrated in FIG. 1, 2 and 3 for chloride concentrations of 50 ppm, 100 ppm
and 200 ppm respectively.
Table-1 Amine Compositions
Name Monoethanloamine
(vol%)
Methoxypropyl
amine (vol%)
Morpholine
(vol%)
Cyclohexylamine
(vol%)
BPNA-1 5 30 45 20
BPNA-2 12 28 30 30
BPNA-3 30 25 30 15
BPNA-4 10 12 38 40
BPNA-5 36 31 16 17
BPNA-6 40 30 15 15
Example 2: Determination of corrosion rate (CR) at various chloride concentrations of
water condensate:
[0056] Effect of chloride concentration on corrosion of carbon steel was experimented using an
overhead corrosion simulator, with and without addition of amine composition of the present
disclosure and the results are shown in FIG. 7. Naphtha containing different concentration of
chloride salts was used for the experiment. It was noticed that the corrosion rate increased with
increase in chloride concentration without the presence of amine composition BPNA -5. Dosages
-12-
of amine composition were optimized with respect to overhead operating conditions and chloride
concentration. Further, it was observed that the corrosion rate increased with increase in chloride
concentration of the water condensate. As shown in FIG. 7, addition of small amount of amine
composition, for example 20 ppm for a chloride concentration of 20 ppm, decreased the
corrosion rate. Further, the required amounts of amine composition for varying levels of chloride
concentrations were determined and the data is provided in below Table-2.
Table-2 Amounts of amine composition for varying levels of chloride concentrations
Amine Dosage
(ppm)
Naphtha + 20
ppm chloride
Naphtha + 40
ppm chloride
Naphtha + 60
ppm chloride
Naphtha + 80
ppm chloride
pH
CR
(MPY)
pH
CR
(MPY
)
pH
CR
(MPY)
pH
CR
(MPY)
0 3.2 10.97 2.9 19.45 2.7 28.55 2.6 36.45
5 5.2 8.20 4.3 15.26 3.9 20.55 3.5 28.44
8 5.8 3.16 5.3 8.65 4.6 14.66 3.8 18.55
10 6.1 2.25 5.8 6.52 4.8 10.44 4.2 15.22
15 -- -- 6.3 4.89 5.5 8.88 5.3 10.21
20 -- -- 6.2 3.51 5.9 5.61 5.9 7.55
25 -- -- 6.1 2.65 6.0 3.55 5.8 4.52
30 -- -- -- -- 6.3 2.89 5.9 3.20
Example 3: Determination of corrosion rate at various pH levels of the water condensate:
[0057] Effect of pH on corrosion of carbon steel was experimented using an overhead corrosion
simulator. Naphtha containing 40 ppm chloride was treated with 25 ppm BPNA-5 and the pH
was monitored. It was observed that at lower pH (2.0-4.5) the corrosion rate was very high, but
at the pH range 5.75 - 6.25 the corrosion rate was comparatively low. As shown in FIG. 8, the
-13-
pH slowly increased and became almost stable in the range of 5.75 - 6.25. It was observed that
25 ppm of amine composition is optimal dosage for 40 ppm chloride solution.
Example 4 Amine blend test results with variation of acid strength:
[0058] Effectiveness of amine blends, realized in accordance with embodiments of the present
disclosure, was checked against different acid strengths i.e. against 0.0001N HCl and against
0.001N HCl. The results of the experiment are as provided in the Table 3 below. It could be
observed that the amine blends, realized in accordance with embodiments of the present
disclosure, are effective against varying acid strengths.
Table-3 Effectiveness of amine blends against different acid strengths
Amine
blend
Acid strength
0.0001 N HCl 0.001 N HCl
Dosage
(ppm)
pH Dosage
(ppm)
pH
Before After Before After
BPNA-5 5 3.8 6.4 5 2.5 6.4
8 3.8 7.0 8 2.5 7.0
BPNA-4 10 3.8 6.5 10 2.5 6.5
17 3.8 7.0 17 2.5 7.0
Example 5: Electrochemical data of amine blend
[0059] Working electrodes of carbon steel cylindrical sample with resinous material in between
reference and working electrode was used after polishing with 1/0 to 4/0 of emery papers. The
specimens were then washed with distilled water and finally degreased with trichloroethylene. A
platinum foil was used as auxiliary electrode. All the experiments were carried out at constant
temperature of 30 ±1°C and at a scan rate of 1mV / sec at open circuit potential. The polarization
curves were recorded after immersion of the electrode in the solution for 30 minutes (until steady
state is reached).
[0060] The cathodic and anodic polarization curves were obtained for mild steel in 1.0 mol dm-3
in the absence and presence of the system containing naphtha + acidic impurities, with and
without corrosion inhibitor and amine blend BPNA -5.
[0061] Electrochemical parameters such as corrosion current density (Icorr), corrosion potential
(Ecorr) and inhibition efficiency (IE) were calculated from Tafel plots. The values of Icorr
-14-
decreased significantly in the presence of good inhibition system. The presence of amine blend
with inhibitor did not exhibit any significant change in Ecorr values suggesting that these
compounds behaves as mixed type inhibitors i.e., they retard the corrosion reaction by blocking
both anodic and cathodic sites of the metal.
Table-4 Electrochemical polarization parameters for the corrosion of mild steel in HCl
containing amines in system
System
Ecorr
( mV)
Icorr
(mA cm-2)
IE
(%)
1 N HCl -461 0.360 -
1 N HCl + BPNA-5 -480 0.033 90.83
1 N HCl + BPNA-3 -476 0.056 84.44
Example 6: Refinery plant trial
[0062] The trials of BPNA-5 were conducted at two different refineries, i.e. refinery-1 and
refinery-2. Crude -1 was processed in refinery-1 and Crude -2 was processed in refinery-2. The
typical properties of crude oils are shown in Table-5 below. The desalter conditions are provided
in Table 6 below.
Table-5 Crude oil properties
Properties Crude -1 Crude -2
Density at 15°C, kg/m3 830.2 872.9
0API 38.9 30.6
Acidity, mg KOH/g 0.10 0.14
Sulphur, wt% 0.09 2.80
Viscosity, cSt (at 40 0C) 3.4 11.1
Pour Point, 0C 30.0 -27.0
Wax, wt% 11.8 6.0
Table-6 Desalter Performance
Refinery-1 Refinery-1
Desalter inlet
Salt content in crude oil, ptb 2.6 2.0
-15-
BS&W, % 0.10 0.05
Wash water pH 9.0 7.5
Chloride, ppm (in wash water) 7.1 11.0
Desalter outlet
Salt content in crude oil, ptb 0.37 0.80
BS&W, % 0.10 0.20
Brine pH 8.6 6.5
Chloride, ppm (in brine) 173.0 120
[0063] BPNA-5 as shown in Table- 1, was injected in atmospheric column overhead of refinery-
1 and refinery-2 to neutralize the acidic environment. Condensed water from naphtha
accumulator boot was collected and analyzed. The ppm dosage of BPNA-5 was calculated on the
basis of total column overhead flow rate. The performance of BPNA-5 is provided in Table 7
below.
Table-7 BPNA-5 plant trial performance
Refinery-1 Refinery-2
BPNA-5
dosage, ppm
pH (Naphtha accumulator
boot water)
BPNA-5
dosage, ppm
pH (Naphtha accumulator
boot water)
2.3 5.5 2.3 5.5
2.4 5.7 2.5 5.8
2.5 5.8 2.8 5.9
2.7 6.0 3.0 6.0
2.9 6.2 3.2 6.3
3.0 6.4 3.5 6.5
ADVANTAGES OF THE PRESENT INVENTION
[0064] The present disclosure provides an improved neutralizing agent capable of neutralizing
acidic components while not permitting the resulting amine salt to deposit on overhead
condensing equipment surfaces.
[0065] The present disclosure provides a neutralizing agent that eliminates or reduces fouling of
overhead condensing system and thereby reduces system down time and productivity loss due to
cleaning and/or replacing fouled equipment.
-16-
[0066] The present disclosure provides a neutralizing agent that is highly effective and it
requires less quantity to increase the pH of the water condensate to corrosion-safe level
compared to known neutralizing agents.
[0067] The present disclosure provides an improved neutralizing agent that can be formulated
using readily available amines.
[0068] The present disclosure provides a method for inhibiting corrosion in overhead condensing
system of distillation columns that is simple, reliable and highly economic.
[0069] The present disclosure provides a method for inhibiting corrosion in overhead condensing
system using an overhead corrosion simulator that facilitates optimization of overhead operating
parameters such as neutralizing agent dosing rate and corrosion rate more accurately.
[0070] The present disclosure provides a method for inhibiting corrosion in overhead condensing
system of distillation columns which obviates the disadvantages associated with the known art.

We Claim:
1. A method for inhibiting corrosion on internal metal surfaces of an overhead condenser of a
crude distillation unit, the method comprising adding to the overhead condenser an amine
composition in an amount and at a rate sufficient to maintain the pH of water condensate in the
condenser above a pH of about 5, the amine composition consisting of a mixture of four amines
wherein the amines are monoethanloamine, methoxypropyl amine, morpholine and
cyclohexylamine present in a specific weight ratio.
2. The method of claim 1, wherein the specific weight ratio of monoethanloamine,
methoxypropyl amine, morpholine and cyclohexylamine in the amine composition ranges from
about 25:30:25:20 to about 30:40:15:15.
3. The method of claim 1, further comprising the steps of using an overhead corrosion simulator
to assess corrosion rate as a function of pH and chloride concentration.
4. The method of claim 1, further comprising the steps of using an electrochemical method for
prediction of corrosion rate.
5. The method of claim 1, wherein the amount of the amine composition ranges from about 1 to
about 10,000 ppm based on an amount of the water condensate.
6. A method for inhibiting corrosion on internal metal surfaces of an overhead condenser of a
crude distillation unit during fractionation of a mixture comprising hydrocarbons, water and
amine hydrochlorides, wherein the condenser has an upper condensing zone which operates at
temperatures below the water dew point of the mixture and a lower condensing zone which
operates at temperatures above the water dew point of the mixture, the method comprising:
adding to the condenser in the upper condensing zone an amine composition in an amount
sufficient to maintain the pH of water condensate in the condenser above a pH of about 6.5 to 7.0
the amine composition consisting of a mixture of four amines wherein, the amines are
monoethanloamine, methoxypropyl amine, morpholine and cyclohexylamine present in a weight
ratio ranging from about 25:30:25:20 to about 30:40:15:15.
7. The method of claim 6, further comprising the steps of using an overhead corrosion simulator
to assess corrosion as a function of pH and chloride concentration.
-18-
8. The method of claim 6, further comprising the steps of using an electrochemical method for
prediction of corrosion rate.
9. The method of claim 6, wherein the amount of amine composition ranges from about 1 to
about 10,000 ppm based on an amount of the water condensate.