JPS6153398A - Detergent of acrylonitrile polymer scale - 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 [Industrial Application Field] The present invention relates to a cleaning agent for removing acrylonitrile polymer scale generated in distillation columns, heat exchangers, etc. of an acrylonitrile plant.

[Conventional technology]

In an acrylonitrile plant, crude acrylonitrile containing cyan gas is introduced into a distillation column and allowed to flow down a tray section laminated with perforated plates, and the liquid in the column is heated and circulated from the bottom of the distillation column through an external heat exchanger. is separated by distillation and discharged from the top of the distillation column, and purified acrylonitrile is taken out from the bottom of the distillation column. In such acrylonitrile plants, acrylonitrile polymers are generated and adhere to distillation columns and heat exchangers, forming scales and clogging trays and heat exchangers.

Conventionally, in order to remove such scale, a method of dismantling and cleaning the plant, and a method of washing with high pressure water after alkaline washing have been used.

[Problem that the invention seeks to solve]

The above method of dismantling and cleaning is inefficient as it involves manual and mechanical cleaning, and the combination of alkaline cleaning and high-pressure water cleaning requires a complicated process, and special equipment for high-pressure water cleaning is required. There were problems such as the need for additional work.

[Means for solving problems]

The present invention is intended to solve the above-mentioned conventional problems, and provides a cleaning agent for acrylonitrile polymer scale that can be efficiently cleaned and removed by simple cleaning operations.

The present invention is an acrylonitrile polymer scale cleaning agent characterized by containing an alkaline agent and a peroxide as active ingredients.

Alkaline agents are those that become alkaline in the form of an aqueous solution.1
For example, sodium hydroxide, potassium hydroxide, etc. can be used. Peroxide is an oxide having 022-, ammonium persulfate, potassium dichromate.

Sodium hypochlorite, potassium permanganate, potassium ferrate, etc. can be used.

The cleaning agent has an alkaline concentration of 3 to 10 when used for cleaning.
% by weight, and the peroxide concentration is 1 to 10% by weight. The alkaline agent and peroxide may be mixed in advance and dissolved in water, or may be dissolved separately in water, or may be mixed at the above concentration from the beginning. can be arbitrarily determined depending on the amount of scale attached, solubility, etc. In addition to the above-mentioned components, the cleaning agent may contain other components such as a dispersant.

[For production]

The cleaning method involves contacting the scale with a cleaning agent to break up and solubilize the scale. The alkaline agent is effective in swelling the polymer, and the peroxide is effective in breaking up and dissolving the swollen polymer, and these act synergistically to remove scale. Use the amount of cleaning agent necessary to remove scale.

A suitable temperature for washing is 60 to 100°C.

High temperature range is effective for fine scale fragmentation and solubilization. Cleaning time is until scale removal is completed.

Generally it is 4 hours or more, preferably 6 to 8 hours.

The contact method may be any method such as dipping or spraying. A preferred method is to form a loop between the upper and lower parts of the distillation column using temporary piping with a pump, and circulate the cleaning liquid within the loop as well as through the heat exchanger. As a result, the cleaning liquid comes into contact with the perforated plate and the heat exchanger to remove scale. After cleaning with a cleaning agent, main cleaning is performed to complete the cleaning.

〔Effect of the invention〕

According to the present invention, since the sulkali agent and the peroxide are used as active ingredients, the acrylonitrile polymer scale can be efficiently removed by cleaning by a simple operation of contacting with a solution-like cleaning agent.

〔Example〕

When we examined the scale of the distillation column (20 meters high) at an acrylonitrile plant, we found that the upper part contained more HCN and was black in color, while the lower part contained less HCN and was white.

Therefore, the scale at the bottom was collected and a dissolution test was conducted by stirring the solution with the scale fixed in the middle of the aqueous drug solution shown in Table 1.

The results are also listed in Table 1.

From the results in Table 1, it can be seen that the cleaning effect of the combination of alkaline agent and peroxide is ah. In addition, the scale has better solubility as it contains more HCN, and the scale at the top and center was sufficiently finely divided and dissolved using the Na9 to Na12 chemicals shown in Table 1 at a scale/liquid volume (g/mu) of 11,500. .

Claims (4)

[Claims] (1) An acrylonitrile polymer scale cleaning agent characterized by containing an alkaline agent and a peroxide as active ingredients. (2) The cleaning agent according to claim 1, wherein the alkaline agent is sodium hydroxide or potassium hydroxide. (3) The cleaning agent according to claim 1 or 2, wherein the peroxide is ammonium persulfate, potassium dichromate, sodium hypochlorite, potassium permanganate, or potassium ferrate. (4) The cleaning agent according to any one of claims 1 to 3, wherein the alkaline agent concentration is 3 to 10% by weight and the peroxide concentration is 1 to 10% by weight.