JPS588882B2 - Corrosion prevention method for vacuum distillation column top condensing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a corrosion prevention method for a vacuum distillation column top condensing device, and more specifically, a method for circulating a portion of condensed water collected from a condenser in each stage to each condenser downstream from the second stage. The present invention relates to a method for effectively preventing corrosion in the top condensing device of a vacuum distillation column by injection.

In general, a device for condensing the top gas of a vacuum distillation column is constructed by connecting condensers in two or three stages. Various gases (non-condensable gas, oil vapor) and steam are sucked into the first stage ejector 2 and enter the first stage condenser 3, where the gases and steam that are not condensed continue to the second stage ejector. 4 and enters the second stage condenser 5,
When the condensers are arranged in three stages, the remaining gas and steam are further sucked into the third stage ejector 6 and enter the third stage condenser 7.

The gas and steam that entered the first to third stage condensers are liquefied and collected in the receiving tank 8, where they are separated from oil and water, with the oil being led to the indirect desulfurization equipment and the water being led to the wastewater treatment equipment. There is.

On the other hand, the gas that is not condensed in the condenser is pressurized by a compressor and sent to a gas cleaning device.

However, the vacuum distillation column overhead gas introduced into this condensing device is highly corrosive and easily corrodes the tubes and shells of each condenser. Injecting drugs is being carried out.

However, although this method is effective in neutralizing the condensed water in the first stage condenser, it has little effect on neutralizing the condensed water in the second and third stage condensers, and the pH is extremely high. (pH 5-5.5), corrosion in the condenser progressed very rapidly, and the tubes and shells had to be replaced frequently.

Therefore, the present inventor conducted extensive research in order to develop a method that can overcome the drawbacks of the conventional corrosion prevention methods and provide excellent corrosion prevention effects.

As a result, by circulating a portion of the condensed water collected from each stage condenser to each condenser from the second stage onwards, the corrosion inhibitor added at the inlet of the first stage condenser can be absorbed into each condenser. It was discovered that it can be evenly distributed throughout the country and can be expected to have an excellent anti-corrosion effect.

The present invention has been completed based on such knowledge, and the gist of the present invention is to provide a first-stage condenser of a condensing device in which condensers are installed in multiple stages for condensing the top gas of a vacuum distillation column. In a method for preventing corrosion of a vacuum distillation column condenser by injecting a neutralizing corrosion inhibitor into the fluid at the inlet, a portion of the condensed water collected from the condenser at each stage is transferred to each downstream stage from the second stage onwards. This is a corrosion prevention method for a vacuum distillation column top condensing device characterized by circulating injection into a condenser.

A device to which the method of the present invention can be applied is a condensing device having multiple stages, usually two or three stages, of condensers installed in series, and this device is attached to the top of a vacuum distillation column. (See Figure 2).

The method of the present invention will be explained based on FIG. 2 as follows.

First, various gases and steam discharged from the top of the vacuum distillation column 1 are sucked together with newly supplied steam into the first stage ejector 2 and enter the first stage condenser 3, where the condensed gases and steam are It is guided to the receiving tank 8.

On the other hand, gas and steam that are not condensed in the first stage condenser 3 are sucked into the second stage ejector 4 and enter the second stage condenser 5, from where they are guided to the receiving tank 8.

Gas and steam that are not condensed in the second stage condenser are further sucked into the third stage ejector 6, and then the third stage condenser 7
where it is condensed and led to a receiving tank.

Here, if we decide to separate the condensed top fraction and water collected in the receiving tank 8 into oil and water and take them out of the condensing device as is in the same way as in the past, the second stage and subsequent stages (in Fig. 2, the second stage Corrosion inside the condenser and ejector of the second and third stages progresses significantly.

The reason for this is that most of the neutralizing corrosion inhibitor added to the gas and steam stream coming out of the top of the vacuum distillation column 1 condenses in the first stage condenser 3 and is led to the receiver tank 8. Therefore, almost no neutralizing corrosion inhibitor is present in the gas and steam flowing into the second stage ejector 4 and the condenser 5 and beyond.

Therefore, in the method of the present invention, a part of the condensed water collected in the receiving tank 8 from the condensers of each stage is transferred to each downstream condenser from the second stage onward (
By circulating and injecting it into the second-stage condenser and third-stage condenser (in FIG. 2), an appropriate amount of corrosion inhibitor is present in the condensed water in these condensers, resulting in a corrosion-preventing effect.

In other words, conventionally, the top fraction and condensed water collected in the receiving tank 8 were separated into oil and water, and the entire amount of condensed water was treated as wastewater by being guided to the wastewater treatment equipment by the pump 9. With the presence of a large amount of corrosion inhibitor, p
H is also a little high, around 6.5, so pump 9 pumps this condensed water.
It is taken out from the discharge pipe 12 as a circulation pipe 11 through a separate pipe and circulated to the second and third stage condensers, which have a low pH, to raise the pH and prevent corrosion.

Generally, if the pH of the water in the condenser is 6.0 or higher, corrosion of the condenser will not progress, so the amount of condensed water to be circulated may be appropriately determined using this as a guide.

Note that the circulation of condensed water not only increases the pH of the water in the condenser, but also introduces a corrosion inhibitor, and both work extremely advantageously in terms of corrosion prevention.

As described above, according to the method of the present invention, it is possible to effectively prevent corrosion of the top condensing device of a vacuum distillation column, especially the second stage condenser, third stage condenser, etc. Corrosion protection can be achieved without any loss of condensation ability.

Therefore, the method of the present invention can be extremely effectively used as a corrosion prevention measure for a vacuum distillation column top condensing device.

Next, the method of the present invention will be explained using Examples and Comparative Examples.

Comparative Example The top gas and steam of a vacuum distillation column were condensed using the condensation apparatus shown in FIG.

At this time, a corrosion inhibitor (trade name: KN 2 0 2, manufactured by Kurita Kogyo ■) was added in front of the first stage ejector 2.

As a result, the pH of the condensed water flowing out from the first stage condenser 3 is 7.0, and the pH of the condensed water flowing out from the second stage condenser 5 is 7.0.
H was 5.8, and the pH of the condensed water flowing out from the third stage condenser 7 was 5.0.

Example The operation was carried out under the same conditions as in the comparative example except that the condensing device shown in FIG. 2 was used.

As a result, the pH of the condensed water flowing out from the third stage condenser 7 was 6.2, which was 5.2 in the case of the comparative example. The pH was increased compared to 0, which was extremely favorable in terms of corrosion prevention.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of a conventional vacuum distillation column top condensing device;
The figure is an explanatory view showing one embodiment of the vacuum distillation column condensation device of the present invention. 1...Reduced pressure distillation column, 2...First stage ejector, 3...First stage condenser, 4...
・Second stage ejector, 5...Second stage condenser,
6...Third stage ejector, 7...Third stage condenser, 8...Receiving tank, 9, 10...
・Pump, 11... Circulation piping, 12...
・Discharge piping.

Claims (1)

[Claims] 1. Vacuum distillation column column condensation formed by injecting a neutralizing corrosion inhibitor into the fluid at the inlet of the first stage condenser of a condensing device consisting of multiple stages of condensers for condensing vacuum distillation column gas. A method for preventing corrosion of a vacuum distillation column condensing device, characterized in that a part of the condensed water collected from the condensers of each stage is circulated and injected into each condenser downstream from the second stage.