JPS62225224A - Absorbing liquid for carbon monoxide - Google Patents

Abstract

PURPOSE:To prevent corrosion of a structural material by adding PO<2->4 to CO absorbing liquid wherein CuCl is dissoved in hexamethylphosphoramide. CONSTITUTION:0.01-0.5mol/l PO<20>4 is added to CO absorbing liquid wherein CuCl is dissolved in hexamethylphosphoramide. PO<2->4 and HCl or Cl<-> perform competitive adsorbing action for a metallic material and thereby PO<2->4 is adsorbed on the surface of metal and corrosion of metallic material due to HCl and Cl<-> is prevented. When amount of PO<2->4 to be added is more than 0.5mol/l, absorbing liquid is flocculated in a jellylike state by heating and therefore >=0.5mol/l amount to be added is unreasonable.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a carbon monoxide absorption liquid, and particularly relates to a carbon monoxide absorption liquid (-carbon monoxide).
The present invention relates to an absorption liquid for separating, concentrating, and recovering CO from various gas sources containing CO (hereinafter referred to as CO).

(Prior art) A method for recovering high-concentration CO from process exhaust gas containing low-concentration CO, such as blast furnace gas from steel plants, is a method for recovering high-concentration CO from process exhaust gas that contains low concentrations of CO, such as blast furnace gas from steel plants. Because it is used as a

Conventional CO separation methods include an absorption method using a cuprous salt solution and a cryogenic separation method that is fundamentally different from this method.

The cryogenic separation method, which is one of the conventional techniques mentioned above, requires complicated cooling and
Since it consists of a heat recovery system and operates at low temperatures, it is necessary to use expensive equipment materials, which increases construction costs.

Furthermore, in order to obtain a lower temperature, it is said that there are problems such as an increase in power consumption "II!it".

On the other hand, as a cuprous salt solution as a CO absorption liquid used in the absorption liquid method, an ammoniacal cuprous salt aqueous solution or a hydrochloric acidic cuprous salt aqueous solution has conventionally been used; There was a problem that the amount of CO absorbed per unit volume was small.

In response to this, in recent years, a CO absorption liquid has been developed in which a complex (CuAfCj!3) of cuprous chloride (hereinafter referred to as C+IC12) and anhydrous aluminum chloride (hereinafter referred to as A7ICβ) is dissolved in toluene, and it has attracted attention. are collecting. This absorption liquid has a characteristic that the amount of CO absorbed per unit volume of solution is much higher than that of the aqueous solution described above. Therefore, when applied to the actual CO separation/concentration process, the operation in the absorption tower does not require high pressure or low temperature, and can be operated at room temperature and pressure, so there is no need for a pressure-resistant structure, and CO
It is said to have the characteristics that the amount of solution circulation can be small because the absorption load can be large.

However, A, which is a component of such an absorption liquid,
When 11Cl comes into contact with water or steam, it undergoes quantitative hydrolysis, which causes a problem in that the amount of CO absorbed also decreases.

On the other hand, the present applicant has developed a complex of CuC1 and hexamethylphosphoramide (also known as trisdimethylaminophosphine oxide, hereinafter referred to as hmpa), CuCj!
-hmpa) was developed (Japanese Patent Application Laid-Open No. 56-1187
No. 20, JP-A-57-19013). This absorption liquid has a much higher amount of CO absorbed per unit volume than an aqueous solution, and can selectively absorb and separate low-concentration CO at low cost and recover it as high-purity CO.

(Problems to be Solved by the Invention) However, when actually operating a process using this absorption liquid, if a large amount of water or dust gets mixed in due to an error or the like, or if the operation is performed at an abnormally high temperature, etc. Absorption liquid may be hydrolyzed. The hydrolysis reaction in this absorption liquid is as follows.

2CuCj! -hmpa+H20- CU2O↓+2HCA+2hmpa HCI (or H+, C1
″″) will corrode the materials of construction of the device.

For this reason, the equipment is made of high-grade stainless steel (SO331
6L or more) and titanium.Also, regarding the organic lining of the equipment, the desorption tower environment described later is relatively high temperature (~130℃), and the solvent such as hmpa In terms of chemical resistance, it is necessary to use expensive linings such as Teflon linings. Additionally, such linings have drawbacks such as difficulty in repair.

The object of the present invention is to obtain co
In the absorption liquid, the purpose is to prevent corrosion of the constituent materials due to the above-mentioned HCl1 or Cl-.

(Means for solving the problem) The absorption liquid of the present invention is a CO2 solution containing CuC1 dissolved in hmpa.
Phosphate ions (PO4
By adding ``-'' to an extent that does not inhibit the practical amount of CO absorption, the absorbent liquid can prevent corrosion of structural materials.

(Function) The phosphate ions added to the absorption liquid of the present invention have a competitive adsorption effect on HCl or CZ- and the gold mud material.
As phosphate ions become adsorbed on the metal surface, H
This will prevent attack (corrosion) of the gold mud material by Cj2 or Cl-.

In the present invention, phosphate ions (PO
42-) is added in an amount of 0.01 to 0.5 mo j! /l is preferred.

(Example) Figure 1 shows the CuC1-hmpa absorption liquid and PO42 in the same wave.
- using an absorption liquid containing 0.5 mol/1 of stainless steel 5US304 and 5US3 at 80°C.
The results of a corrosion test on 16L are shown below. As is clear from the figure, pitting corrosion could not be completely prevented in the case of 5US304, but in terms of pitting depth, it was less than 1/3 compared to the one without PO42-. In addition, in the case of 5US316L, the occurrence of pitting corrosion could be completely prevented. Furthermore, for the purpose of preventing the occurrence of pitting corrosion of 5US304, the amount of PO4'' added was Q, 5 m o
I tried increasing the amount more than 0.5 m o 1 / 1, but it turned out that the absorption liquid aggregated into a jelly-like form due to heating.
It was found that it was impossible to add more than one. This is thought to be due to the formation of polyphosphate.

Next, a general process for absorbing CO in a CO gold-containing gas using this absorption liquid and recovering it as concentrated CO will be described.

FIG. 2 is a diagram showing the principle flow of a CO separation/concentration process using the absorption liquid of the present invention. After the Co-containing gas is pretreated in the pretreatment device 1 as necessary, it enters the absorption tower 2 through the raw gas line 11, where CO is selectively absorbed. The exhaust gas from the absorption tower 2 is discharged into the atmosphere through the exhaust gas line 21 after entrained components and the like are appropriately removed. On the other hand, the liquid that has absorbed CO is sent from the absorption line 31 to the separation column 3 via the heat exchanger 4 to diffuse CO. The gas from the separation column 3 contains a high concentration of CO, but after removing entrained components, it is recovered via the gas line 41 and becomes a product gas. The absorption liquid from which CO has been separated returns to the absorption tower 2 via line 51 and is recycled for use.

The trenching temperature and pressure when this absorption liquid is used in an actual COD condensation/separation process can be changed as appropriate depending on the CO content in the gas, the contact time, the composition of the absorption liquid, etc. In general, lowering the absorption temperature increases the amount of CO absorbed, but requires a cooling device to lower the temperature, increases the viscosity of the absorption liquid, and sometimes causes the absorption liquid to solidify. If the temperature is increased too much, the amount of CO absorbed becomes small, so the absorption temperature is preferably 10 to 80°C. On the other hand, the higher the absorption pressure, the larger the amount of CO absorbed and the faster the absorption speed, but a gas compressor is required, and the device must also have a pressure-resistant structure, which increases construction costs. From these points, the absorption pressure is preferably 0 to 20 kg/cd in gauge pressure.

The temperature of the absorption liquid that has absorbed CO is raised above the absorption temperature.
Also, by reducing the pressure or by contacting with an inert gas, such as water vapor, benzene vapor, etc.
Furthermore, depending on the use of CO, CO may be diffused by contacting with H2 gas or the like. Of course, CO can also be easily diffused by a combination of these. Note that concentrated CO gas can be obtained by collecting the emitted CO, and these can be used directly as fuel or raw material gas for chemical synthesis.

The addition of PO42- in the present invention is similar to CuCl2-hmpa
It is effective for all absorption liquids in the system, for example, CuC1・h m
CuC1・hmp with toluene added to p a absorption liquid
It also exhibits its effect on a-toluene systems, etc.

(Effects of the Invention) According to the present invention, an absorption liquid that can be operated at normal temperature and pressure without reducing the absorption performance of an absorption liquid with a very high CO absorption amount and is safe against corrosion is provided. Therefore, it is possible to manufacture the device using ordinary structural materials, and it is possible to provide a highly efficient and economical CO separation/concentration process without using expensive materials or linings.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the results of a corrosion test using the absorbent of the present invention, and FIG. 2 is a diagram showing the principle flow of a CO separation/concentration process using the absorbent of the present invention. DESCRIPTION OF SYMBOLS 1... Pretreatment device, 2... Absorption tower, 3... Separation tower, 4... Heat exchanger, 11... Raw material gas (Co containing gas) line, 21... Exhaust gas line, 31...CO
41... Concentrated CO gas line; 51... Absorbent line that diffused CO.

Claims (2)

[Claims] (1) A carbon monoxide absorption liquid characterized by adding phosphate ions to a liquid containing cuprous chloride and hexamethylphosphoramide. (2) The carbon monoxide absorption liquid according to claim 1, characterized in that the concentration of phosphate ions is 0.01 to 0.5 mol/l.