JPS60159180A - Inhibitor for acidic gas conditioning solution - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a corrosion control assembly 1>i used in an acid gas removal apparatus and a method of using the same.

[sweetening agent]
J 7'c Dilute aqueous solutions of eg potassium carbonate, alkanolamines such as monoethanolamine, diethanolamine and other weak groups A! ? Using a gas supply (e.g., natural gas and ancillary gases to convert fusible gases such as di-, l-carbons, hydrogen-hydrogens, and carbonyls) into
1: It is well known from the prior art that it can be removed.

Supply absorbent bath liquid t) 1. Contact with 4. +L
It is common practice to use a reboiler with a reboiler to regenerate the rich absorbent containing gaseous components into free absorbent.

This solution is then recycled to the contactor for reuse.

Many efforts have been made to solve the problem of metal corrosion in the equipment used in the above methods. The problem is that mild steel alloys are used in this equipment to save more money than when using newer alloys, such as stainless steel.

Especially acute and/or chronic. of course.

It is common practice to use stainless steel and nickel alloys in sensitive areas, such as 9-hole exchangers.

U.S. Patent No. 3,087,778 (April 30, 1963)
day) is 1,000 to 5,000 'I) pm arsenic,
Potassium carbonate m solution is suppressed by using trivalent oxide of antimony or bismuth.

U.S. Pat. No. 3,808,140 (April 3, 1974) suppresses alkanolamine solutions by using small amounts of panasium or antimony compounds.

U.S. Patent i3,896,044 (July 22, 1975)
(2) Fi, small amounts of nitro-1a-substituted aromatic compounds or their salts are used to suppress the alkanolamine bath solution.

United States Quit Permit No. 959.170 (May 25, 1976)
(Japanese) suppresses the release of alkanolamines by adding a small amount of Daiichi Sugakata.

U.S. Patent No. 4,071,470 (January 31, 1978)
C) The alkanolamine bath liquid is suppressed by additionally using a small amount of a reaction product of ξ, sulfur and alkanolamine.

U.S. Pat. No. 4,096,085 (June 20, 1978) discloses the use of small amounts of polyamines in the presence or absence of steel or sulfur.

Alkanolamine bath liquid is suppressed.

U.S. Patent No. 4.100.099 (July 11, 1978)
) The use of small amounts of quaternary birizonium salts and alkylene polyamines has been shown to suppress acidic gas conditioning fluids.

U.S. Patent No. 4.100.100 (July 11, 1978)
(Japan) suppresses acid gas conditioning fluids by administering small amounts of quaternary pyrisonium salts, thiocyanate or thioamide compounds, and divalent cobalt compounds.

U.S. House No. 4.102,804 (July 25, 1978)
(Japan) suppresses acidic gas conditioning solutions by using small amounts of bridged tetrapyridunium salts and monovalent thiocyanate compounds or thioamide compounds.

U.S. Patent No. 4.116.629 (September 26, 1978)
(Japan) inhibits corrosion of stainless steel (types 410 and 430) through the use of nickel salts when in contact with carbonate baths.

U.S. Patent No. 4;143,119-# (March 6, 1979)
(1999) by suppressing acid gas conditioning bath solutions by using small amounts of copper and in-situ generated polysalbuides.

Although the above compositions are effective, each of them has various drawbacks that limit their general use. For example, the compounds of cypress, antimony, and panadium are known to be positive, and their single use creates anti-communist issues. The use of quaternary pyridinium compounds is known to cause valve cutting problems in some cases.

We now demonstrate that corrosion of iron and steel in gas removal equipment can be effectively reduced by the use of gas conditioning solutions such as aqueous alkanolamines inhibited by active agents soluble thionitrogen compounds. discovered.

It is believed that the result of the interaction between the thionitrogen compound and the gold is naturally present in the gas removal bath used for 1IIIi.

If 4JA is missing, the gas conditioning solution is
Effective copper nickel, cobalt, calcium.

It can be modified by containing a soluble compound of copper, chromium, zinc, tin, aluminum or i-gnesium or more than Fi2af.

The inhibitor is advantageously constantly renewed or maintained in the gas conditioning bath liquid to obtain effective passivation.

The claimed combination of inhibitors reduces corrosion on all ferrous surfaces, i.e. on mild steels, but not on stainless steels (excluding 400 series stainless steels). It is unique in

The inhibitors of the present invention are particularly effective in aqueous solutions of alkanolamines, such as monoethanolamine, soethanolamine, methyljetanolamine, and related alkanolamines commonly used to remove acid gases from gas streams. It is true.

Impure gas/liquid feed MF that can be treated with the suppressed gas conditioning solution of the present invention to remove secondary carbon
, is generally several (1 to 5) ppm, J: not much H! S and/or sulfidation power rudenyl and 500
It can contain less than ppm of oxygen. CC500
A few hundred cubic feet of feed gas containing H,S (up to pp) is treated with the suppressed gas conditioning bath of the present invention by a simple test VC to select the appropriate metal phase action. be able to. For example, metals that form insoluble obtuses generally do not provide corrosion protection.

An example of a useful soluble nickel compound is nickel @e1
1. salts, nitrates, acetates, tartrates and nitrates.

Examples of useful soluble cobalt salts include halides of cobalt, such as chlorides, fluorides, odorants, sulfates of cobalt, nitrates of cobalt-+IJ'+; It is.

Other metals useful in the present invention are used in their related soluble J4 forms.

Useful soluble thioyano compounds are alkali metal thiocyanates, such as -potassium thiocyanate and sodium thiocyanate, and metal thiocyanates, such as steel thiocyanate and nickel thiocyanate. Ammonium thiocyanate is also useful and is a preferred species.

Other examples of soluble thiolated @compounds are formula % formula % () where A is a pyridyl group or a hydrocarbon group having 1 to 6 carbon atoms, and R is a hydrogen atom or a pyridyl group. A thioamide having 1 to 4 alkyl groups on the carbon atoms.

A specific example of a thioamide is thioacetamide, N.

N' Noethylthioacetamide, thiobenzamide.

#, #' Dimethylthioacetamide, thiocapramide,
N, N' soethylthiolopramide, and thionicotinamide.

The term "iB compound" for purposes of the present invention means that Compound J is sufficiently soluble in the aqueous 7F sconditioning bath used herein, i.e., the aqueous alkanolamine. It should be noted that

It has been found that the thionitrogen inhibitor must be maintained in the gas conditioning solution at levels above 50 ppm, preferably above 1100 ppm. As these compounds are depleted during one treatment.

A large amount, such as 500 ppm or more, can be used to start, and subsequent additions can be made in cycles to maintain the required effective amount in the bath solution. 50-1
．． The range of 000 ppm has been found to be an effective amount;
The preferred range is 100 to 300 ppm.

When a fresh supply of thionitrogen-containing gas conditioning solution is used in various Kinrou alloy-containing gas conditioning plants, the bath liquid must be cycled for about 2 to 4 days before immobilization occurs. 'Noru'
It turns out that there is a gap. It is believed that the gas conditioning bath liquid dissolves enough of the sensitive metal to act as a compatibilizer with the thionitrogen compound.

In applications of the present invention where the gas conditioning equipment is comprised solely of mild steel, one or more of the gold & l salts typically must be added in the 7h method shown above.

The invention will be further illustrated by the following examples.

These examples are not intended to limit the invention.

Example 1 A 50 x 10' cubic foot containing 18% CO,
Hydrogen gas flow of 1,4×10'rys”/day.

At a pressure of 3007 Jsi (2,0'IMPα).

18% monoethanolamine is brought into contact with water Mu, and the amine-rich solution reflux is produced in an IJ tower with an in-2 bath, and the spent bath liquid is sent back to the contactor. Ta. A suitable cross-combiner was used.

Stainless steel Q (304) and Monel (η1.ongl
) components were used in heat exchangers.

The corrosion probe ↓ and the same metal Kinpo coupons used in this plant were placed in a cold amine-rich solution, a hot amine-rich solution, and a hot amine-depleted bath solution. Adjust the probe to reduce the corrosion rate to mils (1
1 inch OO1/0.0254m)/YearC
mpy').

The basic corrosion rate in the absence of inhibitors to carbon atoms in a hot amine-rich circuit is 740 ntpy (18,
8/year).

The basic corrosion rate in the absence of inhibitor for 304 stainless steel was -12 mplc O, 30 penalties/year).

The basic corrosion rate in the absence of an inhibitor for chlorine 400 is:
2 rrtpyc O, 051/year).

After the addition of -2 o ppm of ammonium thiocyanate, the corrosion rate for carbon steel drops to less than 2 mpyCO,051 m/year), so that the corrosion rate for stainless steel and Monel decreases to less than 1 rrtpy (0,0254 m/year).
m/year) decreased to a smaller territory.

Then, the amine size was increased from 18 qb to 25%,
And the g eating speed remained the same.

Example 2 In a plant for removing CO2 from flue gas, 18
With ~25% monoethanolamine (MEA), the feed gas? 'iθ~500 pprn of oxygen, and the MEA bath solution contained 1-5 ppruv nickel in the bath number. The corrosion rate is fJl 00 for carbon steel.
m, pHc 2.54 mm 1 year). The corrosion rate was reduced by first using a corrosion inhibitor of Ichikin (-).Ammonium thiocyanate was added at a rate of 200 ppm instead of heavy metal. was 18-25%, it remained at 1-3 mpi/(0,0254-0.0762 mpi/year).Example 3 In a plant similar to that described in Example 2, 1
250 ammonium thiocyanate instead of heavy metal
ppm 17) added at a rate of - and corrosion rate of 1 to 3
mpyc 0.0254-0.0762-7 years).

Example 4 In a water-based gas production plant using 18-25% monoethanolamine, the basic corrosion rate for carbon steel without side Jtljll agent is 350rnpyC8, 89mg/ヰ)
Met.

What is the Fanmoto corrosion rate for 304 stainless steel?

50 mlc 1.27 mm 1 year) in hot amine-rich circuits and d-depleted (oral) tracts.

After adding ammonium thiocyanate at 200 ppm, the corrosion rate t was 27FllV for both metal practices.
(0,0508 m7 years).

Example 5 Containing less than lppm nickel in monoethanolamine solution. In a plant similar to Example 4, the basic corrosion rate in the absence of inhibitors is 1 for carbon steel.
40 mpyC3,56 mm/year) and 10 mpyC0,254 mm/year) for 304 stainless steel.

Corrosion rate Vi15 mp for carbon steel after adding 300 ppm17) ammonium thiocyanate and 50p cobalt sulfate to the kiE A rr7 solution
3/(o, astmm/year) and the corrosion rate for stainless steel is 8-107yip3/(0,
203 to 0.254 dragons/year).

Example 6 In a plant for removing Co1 from natural gas using all carbon steel equipment and a 30% MEA solution, the basic corrosion rate was 1! , 60 mp'jlc 1.52 *tx/year).

With the addition of 200 ppm ammonium thiocyanate, the corrosion rate was 30~40rnpy (0,762~x, 0
2m/year). After a certain period of time, 3 p.
pm of nickel sulfate (NiSO,) was added and the corrosion rate decreased to less than 2 mpy (0,0503 orders/year).

Example 7 In a natural gas fA' plant similar to Example 6 using 16% MEA, the basic corrosion rate for carbon steel is Ml!; 12 mpy (0,305* It was found that the basic corrosion rate for 304 stainless steel pieces was 12 mpyCO, 305 order/year).

20 Of) 7) mf) After addition of ammonium thiocyanate, these corrosion rates are respectively 7'm'py(0
, 17811I+/year) and 36 mpy (0,91
4M! / year). After addition of 7 ppm tD nickel sulfate (NiSO,), the corrosion rate of both of these decreased to 0.1 mpy (0,00254 days/year).

Next, the MEA concentration was increased to 27% using the above combination of ammonium thiocyanate and nickel sulfate.
increased to The corrosion rate is 0.1 mpy (0,0025
4 m/year) (carbon steel) and 0.6 mpy (0,015
2xm1 year) (stainless steel car).

Example 8 In a hydrogen gas purification plant using 16-27% MEA liquid control, the basic corrosion rates for carbon steel and 304 stainless steel are 70'yL7)l/(1,7
8/year) and 15 mpyC0,38111Il/
year).

This rate was reduced to values as low as 12 mpyc O,0508 tries/year for both metals with the arsenic inhibitor.

When using 200 pprdD ammonium thiocyanate and 5ppnuy) nickel sulfate instead of the above inhibitors, the corrosion rate for both v;M is 2 m
p7/C080508/year).

As can be seen from the above, the use of thiocyanate compounds reduces the corrosion rate of mild steel equipment when equipment i also contains heavy stainless steel or nickel alloys.

Examples 9-103 The effectiveness of the corrosion inhibitors of the present invention was determined using a static coupon corrosion test. In this test, 25
and 30% by weight of monoethanolamine CMEA) was saturated with CO2.

This Ma simulates the amine-rich, 4-liquid fluid commonly present in gas conditioning.

35Q+++t of this bath solution containing the inhibitor was then placed in a 2 inch x 10 inch (50.8 inch x 254 inch) Teflon lined cylinder, the prepared mild steel test coupon was inserted and the cylinder C was heated. I closed it and bolted it in place.

Next, the cylinder and its respective turns were heated to 121'C (
250°F) for 24 hours. The coupons were then removed, cleaned, and weighed. Calculate the corrosion rate using the following formula:

[Surface Area (cim') [Time (days)] Convert the result to battles/year.

1 using mild steel (1020&S) in the manner described above.
Corrosion rates for 24 hours at 21°G (250°F) are shown in Table 1.
Describe in ■. The inhibitor used in these tests was ammonium thiocyanate.

Known substances like nickel sulfate, cobalt sulfate, zinc sulfate, preparative salt and calcium sulfate? , a. In each example, experiments were generally conducted postmortem. The corrosion rates reported are the average of two experiments.

The other experiment is listed in ML as (, S7+').

51 asCo+2 + 5Cαli + 2052 2
0 Ca+” + 35 Ca+2 + 2053 2
0 Ca+” + 5 Ca+” +2054 ' 1
0Co+2 + asc'α+2 + 2055 10
Co+2 + 5 Ca+" -4-20565Ca
+” + 5Ca+2 + 2057 5 Co+2
j 5 Ca+2, + 2058 35 CO+”
+' 35 Ca+" + 3859 35 Mg+"
+ 35 ppm Ca+” +60 35 Al+
” + 35 Ca+2 + 2061 10 Ca+
” + 10A#+' + 10* Numbers are in ppm.

**28 experiments.

o 5CN-o, 9 o, o 229 0 5CN-1,650,0419 08CN-1,750,0444 05CN-3,150,0800 08CN-3,55,0,0902 0SCN"" 1,75 0.04440 8CN”-
2,40,061O Ni 2+200SCN-2,5500648200S
C1f 17.45 0゜443208CN-17,9
0,4547 Ca' +2008CN-1,10,027973 2
00ppmSCN + 74 200ppmSCN + 75 200ppmSCN 176 200ppmSCN + 77 2007Jpm SCN + 78 200ppm 5CN-+ 79 200ppmSCN + 80 200ppmSCN + 1 8 1 200ppmSCN + 2 * Average of 64 flashes.

25 ppm Ni+2 4.2 (3 experiments) 0.10
6106740pp+2 7.8 (SR) 0.198
150 ppm Ni” 3.7 (3 experiments) 0.0
94050 ppm Ni” 4.3 (31% test)
0.109250 ppm Ni+25.1 (1*experiment) 0.12955oppmNi” 3.4 0.08
6455 ppm Ni” 6.8C8R> 0.17
2700 ppm Ni+23.9 (3*test) 0.
099100 ppm Ni+2 18 (3 pea
) 0.0 7 1 110.1 5 0Cr”+
2 oo Zn-1-” +102 1ONi” +
10co+2+103 4ONi” + 20oZn+
``10* The number is ppm.

** 64 disasters! Y average.

200 SCN, 22.6 0.5740C8It
) 200Zn+2+ 2008CN-1,90,0483
(S) [) 200 SCM 2.6 0.0660C8R) Examples 104-106 A masterbatch of aqueous 30% monoethanolamine (MIIA) was prepared for each series of experiments and heated with CO2 overnight in a bottle. It was saturated by 1. Enough ammonium thiocyanate was added to the 4009 tone P of this MEA to produce 200 ppWD thiocyanate ion gold during the final bath. In a similar manner, so ppn! →1 N$ or co7 N i SO4・611. O
Or thiocyanate Himekasa, in the form of CoSO4.71i20, was added to some of the earth solution. The bath solution was then divided into three approximately equal portions and placed into 4 ounce (11 & 3d) glass jars each containing a 1020 cup of Kuhn's powder, each having a surface area of 35 cTI.

Next, the sample was filtered through a filter (δ
parkler FiHgr) (water bath with closed lid) - 30 psigc with CO2
Pressure was then increased to 207 kPa-'r''-no). The pressure was then increased to 4 psiyc31 okpa, k-no) with oxygen. All samples were then heated to 130 DEG C. for 24 hours using the steam jacket of the water bath. When cooled,
The corrosion rate was calculated using the volume loss of each coupon. The corrosion rates reported in Table ■ are the average of three individual measurements.

T, afternoon rod toto toto S, Good S.

RG1.飄0 Ro Ro Examples 107-109 Middle 7ii 6 In a manner similar to that described in Examples 104-106, a sufficient amount t7) Ni(SCN), -CoC3C
N'J.

or Co(SCN), 311. O to CO, saturated ME
In addition to bath A, 200 ppm of 5UN- final 0)
caused a degree. The waste evaluation procedure was the same as in the previous example. The results are listed in Table X.

Table X Control 6 None 36.50.9271

Claims (1)

Claims: 1. Corrosion inhibited gas conditioning Mi containing a gas sweetening agent in an aqueous medium, wherein an effective amount of a thionitrogen compound is further present. Wherein, A is a hydrocarbon group having 1 to 6 carbon atoms, and each 11 is independently a hydrogen atom. or an alkyl group having 1 to 4 carbon atoms and 11 to 1 carbon atoms. 3. The composition according to claim 1, which is a liquid. 3. One or more types of Kinkyun selected from the group consisting of cobalt, nickel, calcium, copper, chromium, zinc, tin, aluminum and magnesium. 4. The composition according to claim 1, further characterized in that an effective amount of metal-rich metal soil is present. 4. A patent further characterized in that the amount of iJm metal-rich metal is present in an amount of 2 to 200 ppm. The composition according to claim 3. 5. The composition according to claim 3, further characterized in that the gold salt is a nickel-sweet chromium salt!. 6. 7. The composition according to claim 1, further characterized in that the thionitrogen compound is a bathable thiocyanate.7. 8. The composition according to claim 6, further characterized in that the thiocyanate is an alkali gold maple thiocyanate. 9. The composition according to claim 6, wherein the thiocyanate is an alkali gold maple thiocyanate. The composition according to claim 1, further characterized in that the composition is present in an amount of 50 to 1,000 ppm.10. LF, 1. The composition according to claim 1. 11. Consisting of recirculating a gas conditioning bath solution containing a gas sweetening agent and a corrosion-inhibiting agent through an acid gas removal joint. Corrosion of ferrous metal surfaces by a gas conditioning solution in an acid gas removal kiM in which the solution is brought into contact with a gas containing or not containing CO7 and li, Sf acid systems, for example θ1c. 2. A method for suppressing gas conditioning, wherein the gas conditioning solution is a bath liquid according to claim 1.