Strongly basic amines for minimizing corrosion in systems prone to corrosive salt formation

A corrosive, volatile technology applied in the field of acid salts to solve problems such as not being able to help

Active Publication Date: 2015-08-05
BAKER HUGHES INC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Recent efforts to design new amine neutralizer options for overhead systems have not provided relief in all cases, as such amines will n...

Method used

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  • Strongly basic amines for minimizing corrosion in systems prone to corrosive salt formation
  • Strongly basic amines for minimizing corrosion in systems prone to corrosive salt formation
  • Strongly basic amines for minimizing corrosion in systems prone to corrosive salt formation

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Experimental program
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Embodiment 1

[0025] Theoretically, the hydrochloride salt of ethylamine should be less corrosive than the ammonium chloride salt. The ethylammonium ion has a pKa of 10.75, which is significantly weaker than ammonium's pKa of 9.25. The pH of ethylamine HCl salt is expected to be 0.75, which is higher than that of ammonium chloride. This means that ammonium chloride will generate 5.6 times more hydrogen ions and, theoretically, 5.6 times the corrosion rate. Table 1 shows the results for carbon steel exposed to a 5M molar solution of ammonium chloride and ethylamine HCl at 75°F (24°C) under approximately standard conditions. The difference is close to the predicted value. Corrosion rates for mpy are in mils per year.

[0026] Table 1 The effect of pKa on pH and corrosion rate

[0027]

Embodiment 2

[0029] Experiments were conducted at 160°F (71°C) on ammonium chloride, ethylamine (EA) hydrochloride and a 50 / 50 blend of the two. As mentioned, ammonia has a pKa of 9.25, while EA has a pKa of 10.75. The ammonia salt has a corrosion rate of 349 mpy (8.9 mm / yr) on carbon steel, while the EA salt only corrodes at 17 mpy (0.4 mm / yr). The mixture exhibited a corrosion rate of 146 mpy (3.7 mm / yr), demonstrating that the corrosivity of less basic HCl salts can be reduced by the addition of stronger bases.

Embodiment 3

[0031] Ammonia and monoethanolamine (MEA) are two common pollutants that form salts. Carbon steel coupons were exposed to 1M solutions of the HCl salts of each amine in a degassed environment. The resulting metal loss revealed a corrosion rate of 114 mpy (2.9 mm / yr) for the ammonia salt and 46 mpy (1.2 mm / yr) for the MEA salt. The HCl salt of the strong base amine di-n-butylamine (DBA) was also tested in the same manner, and the resulting corrosion rate was only 8 mpy (0.2 mm / yr). The HCl salt of DBA was then added to the ammonia and MEA salts so that the strong base represented 80% of the total salt. The resulting corrosive effect on carbon steel coupons was significantly reduced. The coupon exposed to the mixture with the ammonia salt showed a corrosion rate of 23 mpy (0.58 mm / yr), ie a drop of 80%. The coupon exposed to the mixture with MEA salt showed a corrosion rate of 14 mpy (0.36 mm / yr), ie a 70% drop. image 3 The figure in shows the results of this experiment.

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Abstract

Corrosion by ammonia/amine salts in hydrocarbon streams such as distillation overhead streams that contain a mineral acid and water can be prevented, avoided or minimized by adding certain strong amines to the streams. The amines have a pKa between about 10.5 to about 12 and include, but are not necessarily limited to, dimethylamine, diethylamine, dipropylamine, diisopropylamine, di-n-butylamine, diisobutylamine, di-sec-butylamine, di-tert-butylamine, pyrrolidine, piperidine, and combinations thereof. If the hydrocarbon stream further includes a nitrogen-containing compound such as ammonia, a tramp and/or a residual amine which can form a corrosive salt with the mineral acid, then the added amine is a stronger base than the tramp or residual amine, if present. The amount of added amine is greater than total amount of nitrogen-containing compound, so that any corrosive salts formed are less corrosive than the salts that would otherwise form from the ammonia and/or tramp amine.

Description

technical field [0001] The present invention relates to methods and compositions for forming acid salts in hydrocarbon streams that are less corrosive than those currently formed, and more particularly, in one non-limiting embodiment, to methods for using relatively strong amines to Methods and compositions for minimizing corrosion in systems containing hydrocarbon streams comprising water and mineral acids. Background technique [0002] In the refining of petroleum products such as crude oil, hydrochloric acid is produced which leads to high metallurgical corrosion rates of distillation units including overhead systems. Neutralizing amines are added to the overhead system to neutralize the hydrochloric acid (HCl) and make it less corrosive. Excess amines, however, form salts which also lead to corrosive effects. As a result, the refining industry has for many years been plagued by amine-hydrochloride deposits in crude distillation columns, tower overheads, and pumped recy...

Claims

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Application Information

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IPC IPC(8): C10G75/02C23F11/00C10G7/10
CPCC10G2300/80C10G2300/202C10G75/02C10G19/00C10G2300/4075
Inventor J·E·拉克
Owner BAKER HUGHES INC
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