JPH03291390A - Corrosion inhibitor preventing heaping and blocking - Google Patents

Abstract

PURPOSE:To prevent heaping and blocking in an apparatus due to the formation of a neutral salt as well as to inhibit corrosion by an acid by adding 3- aminopropanol to a place undergoing severe corrosion by the acid in an oil refining or petrochemical process and increasing the pH of a liq. at the place. CONSTITUTION:In an apparatus for an oil refining or petrochemical process, especially an apparatus for distilling crude oil under ordinary pressure, HCl formed by the hydrolysis of NaCl, MgCl2, etc., in crude oil remarkably reduces the pH of drain water at the top of the distilling tower and the part is corroded by hydrochloric acid. In order to inhibit corrosion by the strong acid, 3- aminopropanol is added so that the pH of water is adjusted to >=4.0 at the initial condensation part of the apparatus. Since amino hydrochloride formed by the reaction of the 3-aminopropanol with hydrochloric acid has a low m.p., heaping and blocking in the apparatus are not caused.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention is useful for preventing corrosion in petroleum refinery equipment, particularly acid corrosion that occurs at initial water condensation points, or corrosion and blockage caused by acids and neutralized salts in petrification processes. This invention relates to a multipurpose and multifunctional corrosion inhibitor suitable for preventing the harmful effects of

[Conventional technology 1] In petroleum refining and petrochemical processes, severe acid corrosion on metal surfaces occurs due to pH reduction caused by acidic substances mixed with raw materials supplied into the system or acidic substances generated during the process. Occur.

Examples of these acidic substances include Has, Cot, HCJ, etc., and corrosion locations include various parts in the workplace, heat exchangers, etc.

For example, in a crude oil atmospheric distillation unit, hydrogen chloride, which is generated by the hydrolysis of chlorine compounds such as sodium chloride and magnesium chloride mixed in the crude oil, significantly lowers the pH of the drain water at the top of the column, resulting in severe Corrosion occurs.

In particular, extremely severe corrosion occurs in locations exhibiting temperatures below point n under operating conditions, such as condensers and piping at the top of the tower.

Further, similar problems due to acid corrosion occur in petrochemical processes such as the BTX refining process.

For this reason, in order to prevent and suppress corrosion and other harmful effects caused by acids, a method has traditionally been adopted to neutralize the acid by injecting ammonia, morpholine, cyclohexylamine, ethylenediamine, alkanolamine, or piperazine into the system. was. (Special Publication No. 57-17917, Japanese Patent Publication No. 6
3-15886).

[Problem to be solved by the invention]

When ammonia, which has been traditionally used, is injected into the top of a column to suppress corrosion in oil refinery equipment, ammonium chloride produced by neutralization undergoes hydrolysis and releases ammonia, lowering the pH of condensed water. , corrodes metal surfaces.

Thus, ammonia is unsuitable for inhibiting corrosion of the initial condensation zone.

On the other hand, morpholine, ethylenediamine, cyclohexylamine, and piperazine have good migration properties to the initial condensation zone and can suppress corrosion by increasing the pH, but the amine hydrochloride produced by neutralization has a melting point of Because it is a highly solid substance, it deposits in distillation columns, around the column pump, in the top pipes and heat exchangers, and causes clogging in the pipes.

Furthermore, there are other problems such as new sub-deposition corrosion due to the accumulation of hydrochloride.

If these hydrochloride deposits occur in the tower, problems such as tray clogging and tray loss due to corrosion will occur.
If it occurs in piping, problems such as fluctuations in operating conditions due to changes in flow rate also occur. In short, deposits and corrosion mutually cause or result in mutual promotion.

[Problem to be solved by the invention]

As a result of intensive studies to solve the above-mentioned conventional problems, the present inventors have found that the amine hydrochloride that is formed has good migration properties to the initial condensation zone, has an excellent corrosion inhibiting effect, and has a melting point of amine hydrochloride. The present invention was completed by discovering a neutralizing agent amine that is less likely to cause stains or clogging in the system due to its low

[Structure of the invention]

The corrosion inhibitor for petroleum refining or petrochemical processes of the present invention, which also prevents deposits and blockage, is composed of 3-aminopropanol as an active ingredient, and the corrosion inhibiting method also involves adjusting the pH of water in the initial condensation part of the process. 3-aminopropanol in an amount necessary and sufficient to maintain 3-aminopropanol above 4.0.

The corrosion inhibitor of the present invention may be directly injected into the target oil, or may be dissolved in water or the like beforehand and then injected.

The injection amount varies depending on the target to be treated, but for example, in the initial condensation section of an oil refinery, it is sufficient to raise the pH of the water in the initial condensation section to about 4.0, preferably about 5.0 or higher. It is preferable that

The injection method may be continuous injection or intermittent injection, but continuous injection is usually preferable, and it is preferable to inject while stirring sufficiently so that it is uniformly dispersed in the target oil.

In the case of an atmospheric distillation apparatus, effective injection locations include trapper side reflux lines and top reflux lines.

On the other hand, in petrochemical plants, it is effective to add it into the system where heat load is applied, immediately before it, or into the circulation system.

In addition, the present invention can be mixed with other coating agents or conventionally known neutralizing agents at any concentration, or used in combination, if necessary.

3-aminopropanol not only has good migration properties to the initial condensation zone and can increase the pH of the initial condensed water, but also has a low melting point and high water solubility of the amine hydrochloride produced by neutralization. It does not deposit and cause clogging in the distillation column, around the column pump, in the top piping, or in the top heat exchanger, nor does it cause corrosion due to the accumulation of the hydrochloride formed.

Therefore, by using the corrosion inhibitor of the present invention,
Not only can it suppress acid corrosion inside the plant and condenser as a neutralizer, but it can also prevent blockage of trays and piping caused by compositions conventionally used as neutralizers, and changes in operating conditions due to changes in flow rate. Problems such as this can also be resolved.

〔Example〕

The present invention will be described in more detail with reference to Examples below, but the present invention is not limited to the following Examples.

Example 1 Hydrochloride salts of various amines shown in Table 1 were prepared and their melting points were measured.

The prepared hydrochloride was allowed to stand in a freezing room at -20°C or lower for 10 days to ensure complete crystal formation.

The results are shown in Table-1.

Table 3 - APOL: 3-aminopropanol MOPA
:3-methoxypropylamine CHA
, cyclohexylamine MOR, morpholine EDA, ethylenediamine Example 2 The present invention was evaluated using a glass O1dershaw type distillation apparatus (shown in Figure 1) equipped with a repoiler and an overhead system similar to the crude oil distillation apparatus.

HCJ containing naphtha and 200ppm chlorine to repoiler l
An aqueous solution was supplied, and aqueous solutions of various amines shown in Table 2 were injected into the column top 3 so as to maintain the pH of all condensing sections 6 at 6, and continuous distillation was performed.

The test time was 8 hours, and the state of the neutralized salt adhering to the initial condensation section 4 and the inside of the apparatus were visually observed, and the results are also shown in Table 2.

Table 2 Example 3 Using the same equipment as in Example 2, the migration to the initial condensation section 4 was investigated by using a mixture of the corrosion inhibitor of the present invention and a conventionally used neutralizing agent or coating agent. Ta.

Table 3 Amine A: Morpholine amine B Nidichlorohexylamine coating agent C: N-stearylpropylene diamine Example 4 In conventional neutralizing agents (CHA, MOR, EDA, etc.), the melting point of the hydrochloride generated in-house is The high temperature caused problems such as tray blockage.

In addition, in the case of a neutralizing agent using an amine that simply has a low melting point of the neutralized salt and has poor migration to the initial condensation zone, corrosion inside the column may occur.
Major problems such as blockage of the side reflux and even missing trays occurred.

On the other hand, the corrosion inhibitor (3-APOL) of the present invention was applied to an actual device (
As a result of continuous injection into the side reflux section at a concentration of 5 ppm/processed crude oil (8-produced 110,000 barrel crude oil atmospheric distillation unit), no problems occurred during continuous use for about 24 months, and the above-mentioned trouble was resolved. It was done.

[Effects of the Invention] By applying the corrosion inhibitor and/or the corrosion inhibition method of the present invention, the corrosion inhibitor can be efficiently added to petroleum refining and petrochemical processes, particularly in the initial condensation part thereof, where a small amount of acid corrosion occurs. Not only can it be effectively suppressed by
Since all problems such as deposition and clogging inside the process caused by the neutralized salts caused by the addition of the inhibitor are solved at the same time, this method has a great effect on the operation and maintenance of process-related steps.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the system of the test distillation apparatus used in Examples 2 and 3. 1: Reboiler 2: Column 3: Tower top 4: Initial condensation section 5: Initial condensation section outlet 6: Total condensation section 7: Separator

Claims (1)

[Scope of Claims] 1) A corrosion inhibitor for preventing deposits and clogging for petroleum refining or petrochemical processes, characterized by containing 3-aminopropanol as an active ingredient. 2) A process characterized by adding 3-aminopropanol in an amount necessary and sufficient to maintain the pH of water in the initial condensation part of the petroleum refining or petrochemical process at 4.0 or higher. Corrosion control method that also prevents deposits and blockages.