JPH0257691A - Crystal deposition inhibitor for univalent metallic salt - Google Patents

Abstract

PURPOSE:To effectively prevent the deposition of crystals of a univalent metallic salt with a small amt. of a crystal deposition inhibitor added by incorporating polyacrylamide having a specified mol.wt. into the inhibitor. CONSTITUTION:Polyacrylamide having 500-1,000mol.wt. as an effective component is incorporated into a crystal deposition inhibitor. The rate of hydrolysis of the polyacrylamide is preferably <=50%. The resulting inhibitor is added to a soln. to be treated by about 0.01-50vol.%. When the inhibitor is added to LiBr as a refrigerant for an absorption type refrigerator, the deposition of crystals of LiBr as a univalent metallic salt is effectively prevented and the concn. of LiBr can be kept high.

Description

[Detailed Description of the Invention] Field of Use in the Ua Industry] The present invention relates to a crystallization inhibitor for monovalent metal salts, particularly LiBr (lithium bromide) used as a refrigerant in absorption refrigerators.
The present invention relates to an anti-crystallization agent that can effectively prevent crystallization of a solution with a small amount added.

[Prior Art] Li Br solution is used as a refrigerant in an absorption refrigerator, but the t,1 Br solution undergoes a crystallization phenomenon, becomes sherbet-like, becomes non-fluid, and causes various problems. For example, when the Li Br concentration in the evaporator increases due to overload operation, it crystallizes in the condenser, causing a blockage problem. For this reason, the LiBr concentration and operating temperature of the LiBr refrigerant 7 are limited.

For example, currently the Li Br concentration of Li Br refrigerant is 56~
62% by weight is used, but this concentration is 30% by weight.
It is set as a concentration that does not crystallize at a temperature of ℃. Similarly, in order to prevent crystallization phenomena, the temperature is generally controlled at 20±0.5° C. as the cooling water outlet temperature.

In this way, restrictions are placed on the operating conditions to prevent the crystallization phenomenon of LiBr refrigerant.
If there is an effective means for preventing the crystallization phenomenon of refrigerants, such restrictions will be alleviated, and absorption chillers are expected to be used in a wider range of applications, including low-level energy recovery.

Conventionally, to prevent the crystallization phenomenon of LiBr refrigerant,
LiBr refrigerant with ZnCj22. ZrB r 21 Ca
CJ: L21 Li Br + ZnCl12 system with Zn (N O3) 2 added as a crystallization inhibitor, Li
Br+ZnBr2 system, Li Br+CaC12+Zn
Refrigerant systems such as (NO3)2 system, LiBr+LiCu+ZnCu2 system, and Li Br+CH30H+ZnCIL2 system are known ("Refrigerant J Vou, 62. No. 7
11. P38).

[Problems to be Solved by the Invention] However, in the conventional refrigerant systems containing crystallization inhibitors, the amount of crystallization inhibitor added is large (usually is 10 to 2 for refrigerant
5-fold view%. In the case of Kanakura Cu2, about 25% by weight is required. ), there is a drawback that the amount of active ingredient of Li Br is relatively significantly reduced.

An object of the present invention is to solve the above-mentioned conventional problems and to provide a monovalent metal salt crystallization inhibitor that can provide a high crystallization prevention effect with a small amount added.

[Means for Solving the Problems] The monovalent metal salt crystallization inhibitor of the present invention has a molecular weight of 500 to 500.
It is characterized by containing ioooo polyacrylamide.

The present invention will be explained in detail below.

The polyacrylamide contained as an active ingredient in the crystallization inhibitor of the present invention has a molecular weight of 500 to 10,000. Even if the molecular weight of the polyacrylamide is less than 500 or more than 10,000, a sufficient crystallization prevention effect cannot be obtained.The molecular weight of the polyacrylamide is particularly preferably from 1,000 to 5,000.

Note that the hydrolysis rate of this polyacrylamide is preferably 50% or less. If the hydrolysis rate is high, the effect of preventing crystallization will decrease and the amount of the crystallization inhibitor of the present invention required to be added will be large, which is not preferable.

The anti-crystallization agent of the present invention varies depending on the type and concentration of the first metal salt contained in the solution to be treated, the required crystallization prevention effect, etc., but in general, the anti-crystallization agent is 0.01 to 50% by volume as the amount of acrylamide,
It is particularly preferable to add about 0.1 to 20% by volume.

In addition to polyacrylamide having a molecular weight of 500 to 10,000, the crystallization inhibitor of the present invention includes other crystallization inhibitors, anticorrosive agents such as molybdic acid and chromic acid, hydrazine, It may contain sterilizers such as EDTA, MBT, BTI, and other sterilizers that generate Ag ions.

By adding the crystallization inhibitor of the present invention to the LiBr refrigerant of an absorption chiller, it can effectively prevent the precipitation of LiBr crystals and increase the LiBr concentration of the LiBr refrigerant to about 85% by weight. It is considered possible. In addition, the crystallization inhibitor of the present invention can prevent the precipitation of NaCl2 in smoke washing towers of garbage processing plants.
It can be used in a wide range of applications, such as salt production equipment, degassing towers, and deodorizing towers, which prevent adhesion and cause blockage of pipes due to the precipitation of NaCl2. Precipitation can be effectively prevented.

[Function] In cooling water systems, seawater desalination equipment, etc., poorly soluble gypsum, calcium carbonate, calcium phosphate, zinc phosphate, basic zinc carbonate, etc. form scales, so various scale inhibitors are used to prevent these scales. It is used. Incidentally, the scaling phenomenon is microscopically a crystallization or crystal growth phenomenon, and the scaling prevention technique is a crystallization prevention technique, that is, a crystal growth suppression technique. It is the sparingly soluble salts mentioned above that tend to cause scale damage, and the cations and scale inhibitors that constitute these salts are also sparingly soluble. At the growth point of the crystal, the crystal constituent ions reach a microscopically low equilibrium concentration, and the concentration of the crystal constituent ions in the interfacial double layer decreases, causing the scale inhibitor ions and crystal constituent cations, which have slightly higher solubility, to
It becomes insolubilized at the crystal growth point, and the steric structure and charge of the scale inhibitor prevents further bonding between crystal constituent ions and bulk ions. This is considered to be the mechanism of action of the scale inhibitor.

On the other hand, LiBr and NaCj! A salt of a strong monovalent base and a strong acid such as the above is an easily soluble salt that dissolves at a high concentration of several tens of grams or more per 100 grams of water.

Chemicals having the same function as the scale inhibitors mentioned above are considered to be effective for preventing the crystallization of these easily soluble salts, but scale inhibitors are effective against the monovalent cations targeted by the present invention. It was thought that there were no effective drugs because the solubility of the drug did not reach the required amount.

In the present invention, the reason why nonionic polyacrylamide exhibits a good anti-crystallization effect is considered to be due to the following effect. In other words, since polyacrylamide has weak ionicity, it can coexist with easily soluble salts in water at high concentrations, and the carboxyl groups generated in small amounts by hydrolysis within the interfacial double layer adsorb to the crystal growth points (crystal form effect), suppresses crystal growth. This means that ordinary scale inhibitors are Li
This is also confirmed by the fact that polyacrylamide does not become insolubilized, whereas it becomes violently insolubilized immediately after the addition of Br.

[Example] EXAMPLES The present invention will be described in more detail with reference to Examples below.

Example 1 Li Br was heated to make a 70% by weight Li Br aqueous solution, and 1 mJ2 of various chemicals shown in Table 1 was added to 10 mJl (purity 25%) of the solution (No.

1 was not added). The state of each solution was observed when it was cooled to 20°C in the refrigerator at the time of addition (30 minutes later) and when it was cooled to 10°C (1 hour later), and evaluated using the following criteria. The results are shown in Table 1.

Evaluation criteria O: No crystal precipitation observed.

Δ: Crystals precipitate and flow is difficult.

×: A large amount of crystals precipitates and does not flow.

From Table 1, it is clear that only the low molecular weight polyacrylamide exhibits the anti-crystallization effect under all conditions.

Example 2 Crystal precipitation was evaluated for the drugs shown in Table 2 in the same manner as in Example 1 except that the LiBr solution concentration was 80% by weight. The results are shown in Table 2.

From Table 2, only low molecular weight polyacrylamide has a very small amount of crystal precipitation.
It is recognized that a good crystallization prevention effect is exhibited even under the high concentration condition of a % by weight LiBr solution.

Note that when LiBr precipitated by cooling at 20° C. without the addition of chemicals (No. 1) was observed under a microscope, it was found that although the crystal form was amorphous, huge granular crystals were formed. On the other hand, when low molecular weight polyacrylamide was added (No.
, 10), the crystals precipitated upon cooling to 10°C had small crystal diameters and were rounded. This shows that low molecular weight polyacrylamide has the above-mentioned crystal type effect.

[Effects of the Invention] As detailed above, the monovalent metal salt crystallization inhibitor of the present invention has an extremely excellent crystallization prevention effect, and therefore can effectively inhibit monovalent metals such as LiBr and NaCu even when added in a small amount. Salt crystal precipitation can be prevented.

Therefore, by adding such a crystallization inhibitor of the present invention to the Li Br refrigerant of an absorption refrigerator, for example, it is possible to prevent the precipitation of Li Br crystals even in a high concentration Li Br solution, and to improve the By ensuring stable operation and increasing the Li Br concentration, device efficiency can be significantly improved.

Agent: Patent attorney Tsuyoshi Urino

Claims (1)

[Claims] (1) A monovalent metal salt crystallization inhibitor characterized by containing polyacrylamide having a molecular weight of 500 to 10,000.