U.S. patent application number 16/090957 was filed with the patent office on 2019-04-25 for process for controlling corrosion in petroleum refining units.
The applicant listed for this patent is Dow Global Technologies LLC. Invention is credited to Frederick S. Foster, Stephen W. King, Lorenzo Spagnuolo, Runyu Tan.
Application Number | 20190119580 16/090957 |
Document ID | / |
Family ID | 56682213 |
Filed Date | 2019-04-25 |
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United States Patent
Application |
20190119580 |
Kind Code |
A1 |
Tan; Runyu ; et al. |
April 25, 2019 |
PROCESS FOR CONTROLLING CORROSION IN PETROLEUM REFINING UNITS
Abstract
A process for controlling corrosion and fouling in petroleum
refining units. The corrosion controlling agent comprises an amine
and an alcohol. The process comprises the step of adding the amine
and the alcohol to the overhead system of the petroleum refining
unit, either separately or in combination.
Inventors: |
Tan; Runyu; (Richwood,
TX) ; Spagnuolo; Lorenzo; (Milan, IT) ; King;
Stephen W.; (League City, TX) ; Foster; Frederick
S.; (Lake Jackson, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Dow Global Technologies LLC |
Midland |
MI |
US |
|
|
Family ID: |
56682213 |
Appl. No.: |
16/090957 |
Filed: |
April 27, 2017 |
PCT Filed: |
April 27, 2017 |
PCT NO: |
PCT/US2017/029760 |
371 Date: |
October 3, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C10G 75/02 20130101;
C10G 2300/80 20130101; C10G 2300/44 20130101; C10G 7/10 20130101;
C23F 11/122 20130101; C23F 11/141 20130101; C10G 2300/4075
20130101 |
International
Class: |
C10G 7/10 20060101
C10G007/10; C23F 11/14 20060101 C23F011/14; C23F 11/12 20060101
C23F011/12 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 29, 2016 |
IT |
102016000044341 |
Claims
1. A process for controlling corrosion in an overhead system of a
refining unit comprising water condensate and petroleum products
comprising the step of adding to the system an amine and an
alcohol.
2. The process of claim 1 wherein the amine is an alkylamine, an
alkanolamine, or mixtures thereof.
3. The process of claim 1 wherein the amine is dimethylethanolamine
(DMEA), dimethylisopropanolamine (DMIPA), ethylenediamine (EDA),
methoxypropylamine (MOPA), monoethanolamine (MEA),
dimethylaminopropylamine (DMAPA), morpholine, trimethylamine (TMA),
picoline, pyridine, or mixtures thereof.
4. The process of claim 1 wherein the alcohol is a polyol,
polyether diol, polyether triol, or mixtures thereof.
5. The process of claim 1 wherein the alcohol is a polyol based on
ethylene glycol reacted with ethylene oxide, a polyol based on
ethylene glycol reacted with propylene oxide, or a polyol based on
ethylene glycol reacted with ethylene oxide and propylene oxide, or
mixtures thereof.
6. The process of claim 1 wherein the alcohol is a polyol based on
glycerol reacted with ethylene oxide, a polyol based on glycerol
reacted propylene oxide, a polyol based on glycerol reacted
butylene oxide, a polyol based on glycerol reacted ethylene oxide
and/or propylene oxide and/or butylene oxide, or mixtures
thereof.
7. The process of claim 1 wherein the alcohol is ethylene glycol,
diethylene glycol, triethylene glycol, tetraethylene glycol,
glycerol, polyethylene glycol, polypropylene glycol,
polytetramethylene glycol, or mixtures thereof.
8. The process of claim 1 wherein the alcohol is diethylene glycol,
ethylene glycol, glycerol, or mixtures thereof.
9. The process of claim 1 wherein the amine and the alcohol are
added to the system separately.
10. The process of claim 1 wherein the amine and the alcohol are
added to the system together.
11. The process of claim 1 wherein the amount of the amine and the
alcohol independently range from 1 to 10,000 ppm based on the
petroleum products.
12. The process of claim 1 further comprising the step of adding
the amine and the alcohol to the system at a rate sufficient to
maintain the pH of water condensate in the system at a pH of equal
to or greater than 4.0.
Description
FIELD OF THE INVENTION
[0001] The present invention pertains to a process for controlling
corrosion in petroleum refining units by reducing buildup of
hydrochloride salts and minimizing fouling of the apparatus.
BACKGROUND OF THE INVENTION
[0002] Hydrocarbon feedstocks such as petroleum crudes, gas oil,
etc. are subjected to various processes in order to isolate and
separate different fractions of the feedstock. In refinery
processes, the feedstock is distilled so as to provide the various
valuable fractions, e.g., light hydrocarbons, gasoline, naphtha,
kerosene, gas oil, etc. The lower boiling fractions are recovered
as an overhead fraction from the distillation and vacuum columns.
The intermediate components are recovered as side cuts from the
distillation column. The fractions are cooled, condensed, and sent
to collecting equipment. No matter what type of petroleum feedstock
is used as the charge, the distillation equipment is subjected to
the corrosive activity of acids such as H.sub.2S, HCl, organic
acids, and H.sub.2CO.sub.3. The problem of corrosion caused by
these acid gases as water condenses in the overhead condensing
systems of distillation and vacuum columns is well known. The
consequent presence of acidic water leads to the undesirable
corrosion of metallic equipment, often rapidly.
[0003] The general mechanism of this corrosion is an oxidation of
metal atoms by aqueous hydrogen ions. The rate of corrosion is
directly related to the concentration of aqueous hydrogen ions. A
particularly difficult aspect of the problem is that the 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 the dew point of water. At this point a mixture
of liquid water, hydrocarbon, and vapor may be present. The initial
condensate may occur within the distilling unit itself or in
subsequent condensers and other equipment. The top temperature of
the fractionating column is normally maintained above the dew point
of water. The initial aqueous condensate formed contains a high
percentage of HCl. The chlorine comes from salts in the crude, and
recently the salt content of crude oil (especially Opportunity
Crudes) being used in refineries has increased, generating more
chlorides. Due to the high concentration of acids dissolved in the
water, the pH of the first condensate can be rather low. Thus, as
noted, the condensed water can be highly corrosive. It is important
that the first condensate is made less corrosive.
[0004] Conventionally, highly basic ammonia has been added at
various points in the system in an attempt to inhibit the
corrosiveness of condensed acidic materials. However, ammonia has
not been effective to eliminate corrosion occurring at the initial
condensate due to its volatility. In one non-limiting view, ammonia
may be ineffective because it does not condense completely enough
to neutralize the acidic components of the first condensate.
[0005] Amines such as morpholine and methoxy propylamine have been
used successfully to control or inhibit corrosion that occurs at
the point of initial condensation within or after the distillation
unit. Adding amines to the petroleum fractionating system raises
the pH of the initial condensate rendering the material
substantially less corrosive. The amine inhibitor can be added to
the system either in pure form or as an aqueous solution. In some
cases, sufficient amounts of amine inhibitors are added to raise
the pH of the liquid at the point of initial condensation to above
4.5; in some cases to between 5.5 and 6.5. Other highly basic
(pKa>8) amines have been used, including ethylenediamine,
monoethanolamine and hexamethylene diamine.
[0006] However, the use of these highly basic amines for treating
the initial condensate has a problem relating to the resultant
hydrochloride salts of these amines which tend to form deposits in
distillation columns, column pumparounds, overhead lines, overhead
heat exchangers and other parts of the system. These deposits occur
after the particular amine has been used for a period of time,
sometimes in as little as one or two days. These deposits can cause
both fouling and corrosion problems and are particularly
problematic in units that do not use a water wash.
[0007] Thus, it would be desirable if a process could be devised
that neutralizes acid environments in distillation overheads of
hydrocarbon processing facilities that minimizes or reduces
deposits of hydrochloride and amine salts.
BRIEF SUMMARY OF THE INVENTION
[0008] The present invention is a process for controlling corrosion
in an overhead system of a refining unit comprising water
vapor/condensate and petroleum products comprising the step of
adding to the system an amine compound and an alcohol, preferably
wherein the amount of the amine compound and the alcohol
independently range from 1 to 10,000 ppm based on the petroleum
products.
[0009] In one embodiment of the process disclosed herein the amine
compound is an alkylamine, an alkanolamine, or mixtures thereof,
preferably dimethylethanolamine (DMEA), dimethylisopropanolamine
(DMIPA), ethylenediamine (EDA), methoxypropylamine (MOPA),
monoethanolamine (MEA), dimethylaminopropylamine (DMAPA),
morpholine, or trimethylamine (TMA).
[0010] In one embodiment, the process disclosed herein above
wherein the alcohol is a polyol, polyether diol, polyether triol,
or mixtures thereof.
[0011] In one embodiment the process disclosed herein above the
alcohol is a polyol based on ethylene glycol reacted with ethylene
oxide, a polyol based on ethylene glycol reacted with propylene
oxide, or a polyol based on ethylene glycol reacted with ethylene
oxide and propylene oxide, or mixtures thereof.
[0012] In one embodiment of the process disclosed herein above the
alcohol is a polyol based on glycerol reacted with ethylene oxide,
a polyol based on glycerol reacted propylene oxide, a polyol based
on glycerol reacted butylene oxide, a polyol based on glycerol
reacted ethylene oxide and/or propylene oxide and/or butylene
oxide, or mixtures thereof.
[0013] In one embodiment of the process disclosed herein above the
alcohol is ethylene glycol, diethylene glycol, triethylene glycol,
tetraethylene glycol, glycerol, polyethylene glycol, polypropylene
glycol, polytetramethylene glycol, or mixtures thereof.
[0014] In one embodiment of the process disclosed herein above the
amine compound and the alcohol are added to the system
separately.
[0015] In one embodiment of the process disclosed herein above the
amine compound and the alcohol are added to the system
together.
[0016] In one embodiment the process disclosed herein above further
comprises the step of adding the amine compound and the alcohol to
the system at a rate sufficient to maintain the pH of water
condensate in the system at a pH of equal to or greater than 4,
more preferably equal to or greater than 5.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a plot of the solubility of monoethanolamine
hydrochloride and ethylenediamine hydrochloride in diethylene
glycol at different temperatures.
[0018] FIG. 2 is a plot of the viscosities of room temperature
saturated solutions of monoethanolamine hydrochloride and
ethylenediamine hydrochloride in diethylene glycol at different
temperatures.
[0019] FIG. 3 is a plot of the viscosity of room temperature
saturated solutions of monoethanolamine hydrochloride and
ethylenediamine hydrochloride in glycerine at different
temperatures.
DETAILED DESCRIPTION OF THE INVENTION
[0020] Methods and compositions are disclosed for neutralizing acid
environments and controlling corrosion in distillation overhead
systems of petroleum product processing facilities, including, but
not limited to distillation columns, vacuum distillation columns,
preflash towers, and the like. The neutralizer composition
comprises an amine compound and an alcohol.
[0021] For decades, refiners have struggled with providing adequate
neutralization in overhead systems without forming corrosive salts.
Ammonia and several amines have been tried to control corrosion
with random successes and failures. The neutralizer compositions of
the invention will allow reduction of fouling tendency of the
corrosive salts without changing the neutralization power of
ammonia and amines.
[0022] The water vapor/condensate coming out of the overhead of the
crude distillation unit (CDU) in the refinery is very acidic
primarily due to the presence of acidic components, such as
hydrochloric acid (HCl), which is formed when the crude oil passes
through a heating furnace (composed of metal chlorides such as
MgCl.sub.2, CaCl.sub.2, etc.) prior to entering the CDU. Water
vapor and HCl rise to the top of the distillation tower along with
the light components of the crude oil such as liquefied petroleum
gas and naphtha. This stream passes through an overhead line and
then enters a condenser, after which the water stream will be
separated from naphtha and off-gas and sent to a water treatment
unit. The acidic HCl stream (often having a pH less than 2) is
highly corrosive and needs to be neutralized (preferably to a pH of
4 or greater, more preferably 5 or greater). The neutralizing
composition is added to the overhead system, traditionally,
neutralizers are injected into the overhead system between the CDU
and the condenser.
[0023] In one embodiment of the present invention, the neutralizing
composition may be added to the overhead system upstream of the
aqueous dew point. This addition point is usually the overhead line
off of the distillation column or the vapor line off of a dry first
condensing stage accumulator.
[0024] It will be appreciated that it is not necessary for
corrosion in distillation overheads or other equipment to
completely cease for the method of this invention to be considered
successful. Indeed, the inventive method should be considered
operative if corrosion is inhibited to a measurable extent. In the
context of this invention, the term "controlling corrosion" is
defined to include any cessation, prevention, abatement, reduction,
suppression, lowering, controlling or decreasing of corrosion,
rusting, oxidative decay, etc. Similarly, the term "neutralize"
refers to such corrosion inhibition by reducing the acidity of the
chemicals or components in the system such as by raising pH, but
does not require adjusting pH to be 7, but rather raising of pH and
moving from acidity to basicity to some measurable extent.
Furthermore, the nature of the metal surfaces protected in the
methods of this invention is not critical. The metals in which the
system operates may include, but are not necessarily limited to
iron alloys, copper alloys, nickel alloys, titanium alloys, and
these metals in unalloyed form as well, etc.
[0025] The first component of the neutralizing composition is an
amine compound, preferably one or more alkylamine or alkanolamine,
preferably dimethylethanolamine (DMEA), dimethylisopropanolamine
(DMIPA), ethylenediamine (EDA), methoxypropylamine (MOPA),
monoethanolamine (MEA), dimethylaminopropylamine (DMAPA),
morpholine, and trimethylamine (TMA). The one or more alkylamine or
alkanolamine is added in an amount of from 1 ppm to 10,000 ppm
based on the petroleum products.
[0026] Preferably the amine compound is added in an amount of equal
to or greater than 1 ppm, preferably equal to or greater than 1
ppm, more preferably equal to or greater than 10 ppm, and more
preferably equal to or greater than 100 ppm based on the petroleum
products. Preferably the amine compound is added in an amount of
equal to or less than 5,000 ppm, preferably equal to or less than
1,000 ppm, and more preferably equal to or less than 500 ppm based
on the petroleum products.
[0027] The second component of the neutralizing composition is an
alcohol. Any suitable alcohol may be used. Preferably, the alcohol
is a polyol, polyether diol, polyether triol, or mixtures thereof.
In one embodiment, the alcohol s a polyol based on ethylene glycol
reacted with ethylene oxide, a polyol based on ethylene glycol
reacted with propylene oxide, a polyol based on ethylene glycol
reacted with butylene oxide or a polyol based on ethylene glycol
reacted with ethylene oxide and/or propylene oxide and/or butylene
oxide, or mixtures thereof. In another embodiment, the alcohol is s
a polyol based on glycerol reacted with ethylene oxide, a polyol
based on glycerol reacted propylene oxide, a polyol based on
glycerol reacted ethylene oxide and propylene oxide, or mixtures
thereof. In yet another embodiment, the alcohol is ethylene glycol,
diethylene glycol, triethylene glycol, tetraethylene glycol,
glycerol, polyethylene glycol, polypropylene glycol,
polytetramethylene glycol, or mixtures thereof. The one or more
alcohol is added in an amount of from 1 ppm to 10,000 ppm based on
the petroleum products.
[0028] Preferably alcohol is added in an amount of equal to or
greater than 1 ppm, preferably equal to or greater than 1 ppm, more
preferably equal to or greater than 10, and more preferably equal
to or greater than 100 ppm based on the petroleum products.
Preferably the alcohol is added in an amount of equal to or less
than 5,000 ppm, preferably equal to or less than 1,000 ppm, and
more preferably equal to or less than 500 ppm based on the
petroleum products.
[0029] It will be appreciated that it is difficult to predict what
the optimum dosage rate would be in advance for any particular
system. The dosage will depend upon a variety of complex,
interrelated factors including, but not necessarily limited to, the
exact nature of the stream being fractionated, the temperature and
pressure of the distillation conditions, the particular amine
blends used, etc. In one non-limiting embodiment of the invention,
the dosage rate will be determined on a case-by-case basis
depending upon the acid content of the system. It may be desirable
to use computer modeling to determine the optimum rate.
Nevertheless, to provide some understanding of expected or possible
dosage rates, the amount of the amine compound and alcohol may
independently range from 1 to 10,000 ppm, based on the petroleum
products. In another non-limiting embodiment, the amount of the
amine compound and alcohol may independently range from 1 to 500
ppm.
[0030] The desired pH range for all points in the system is from 4
to 8.5, and in another non-limiting embodiment may be from 5 to 7.
Alternatively, to give another idea of expected dosage rates, the
neutralizing composition may be added to the system at a rate
sufficient to maintain the pH of water condensate in the system at
a pH of equal to or greater than 4.0. In another non-limiting
embodiment, the neutralizing composition may be added to the system
at a rate sufficient to maintain the pH of equal to or greater than
5.0.
EXAMPLES
[0031] The solubility of the monoethanolamine hydrochloride
(MEA.HCl) and or ethylenediamine hydrochloride (EDA.2HCl) in
diethylene glycol or glycerol is determined as follows: to 10 g of
diethylene glycol or glycerol is added an excess amount of the salt
and the reaction mixture is stirred rigorously for at least 1 h at
the desired temperature. The stirring is then stopped and the
reaction mixture is allowed to settle. The solubility of the salt
in ethylene glycol or glycerol is calculated from the chloride
concentration measured by Ion Chromatography. The viscosity of the
saturated solution is measured on a Stabinger Viscometer.
Example 1
[0032] The solubility of MEA.HCl and EDA.2HCl in diethylene glycol
at different temperatures is shown in FIG. 1 and the viscosity of
the room temperature saturated solution of MEA.HCl and EDA.2HCl at
different temperatures is shown FIG. 2.
Example 2
[0033] At 25.degree. C., the solubility of MEA.HCl and EDA.2HCl in
glycerol is determined to be 44.5 wt % and 12.8 wt %, respectively.
The viscosity of the room temperature saturated solution of MEA.HCl
in glycerine and EDA.2HCl in glycerine at different temperatures is
shown in FIG. 3.
* * * * *