JPH0470246B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a bleaching solution containing calcium hypochlorite as a main component, and more specifically to a dry carbide slag produced as a by-product from a so-called dry acetylene gas generator in which acetylene gas is obtained by sprinkling water on calcium carbide. The present invention relates to a method for safely and stably producing a useful bleaching solution using the present invention. When calcium carbide reacts with water, acetylene gas is generated, and this acetylene gas is widely used in organic synthesis and dissolved acetylene. At this time, a large amount of carbide slag is produced as a by-product, and its main component is calcium hydroxide, but it is said to be almost unsuitable for use in chemical synthesis because it contains various impurities. It's here. There are wet methods and dry methods for generating acetylene gas from calcium carbide.
In the case of the wet method, processing is extremely difficult because muddy carbide slag is produced as a by-product. For this reason, in recent years, dry methods have been increasingly adopted in place of wet methods. However, although the carbide slag produced by the dry process is obtained in powder form, it has only been used as a neutralizing agent for soil and the like. Therefore, if dry carbide slag can be used in the synthesis of chemicals in the form of lime emulsion, it will have a great effect on the treatment of dry carbide slag, which has low utility value. The purpose of the present invention is to meet these demands. The dry method for generating acetylene gas differs from the wet method in the following points. In the wet method, calcium carbide is poured into a large amount of water, whereas in the dry method, a small amount of water (2 to 3 times the theoretically required amount) is sprinkled on the calcium carbide to generate acetylene gas. The temperature is extremely high, and as a result, a small amount of side reaction products such as decomposition or polymerization of acetylene gas are contained in the generated acetylene gas or by-product carbide slag, and a small amount of unreacted residual carbide is present. It has been known for a long time that it exists in carbide slag. Therefore, not only when using dry process acetylene gas, but also when using dry process carbide slag, it is necessary to give due consideration to the aforementioned side reaction products or residual carbide, and to take measures such as removal treatment. It was hot. In fact, when chlorine gas was absorbed into a lime suspension made from unremoved dry carbide slag,
It was discovered that in the latter half of the reaction, ignition and explosion occurred at the liquid interface, a peculiar phenomenon that was extremely important for safety. Although the detailed reason is unknown, it is safe to use dry carbide slag to absorb and react chlorine gas into the dry carbide slag suspension to produce a bleaching solution whose main component is calcium hypochlorite. This method had extremely serious drawbacks. The present inventors have conducted intensive research on a method for producing a bleaching solution using dry carbide slag, which has low utility value, as a raw material. As a result, we have discovered that chlorine gas of less than a specific concentration can be absorbed into the dry carbide slag suspension. The present invention was based on the discovery that a bleaching solution can be produced safely and without any harm by doing so. That is, in the present invention, water is added to dry carbide slag produced as a by-product from a dry acetylene gas generator that generates acetylene gas by sprinkling water on calcium carbide, and chlorine gas is added to the resulting dry carbide slag suspension. In the method of producing a bleaching solution containing calcium hypochlorite as a main component by introducing the chlorine gas into the dry carbide slag suspension and causing an absorption reaction, the chlorine gas is
It is an object of the present invention to provide a method for producing a bleaching solution using a dry carbide slag, characterized in that it is introduced into the dry carbide slag suspension at a concentration of less than 97% by volume. The dry carbide slag used in the present invention is a carbide slag obtained by sprinkling 2 to 3 times the theoretically required amount of water on calcium carbide to generate acetylene gas, and has a water content of about 10% or less and no residual carbide. It is a fluid powder of approximately 0.5% or less, containing calcium hydroxide as the main component and various impurities. Next, an example of analysis of the composition of dry carbide slag and wet carbide slag will be described.

[Table] The impurities in dry carbide slag are unique in comparison to the impurities in wet carbide slag in that they contain a large amount of residual carbide and nitrogen, with most of the nitrogen content being ammonia. Water can be added to this dry carbide slag to obtain a dry carbide slag suspension. For example, the above-mentioned dry carbide slag is mixed with water in a mixing tank equipped with an agitator and used as a dry carbide slag suspension, generally having a concentration of 5 to 15% by weight. Next, the chlorine gas used in the present invention can be approximately 100% liquid chlorine or chlorine discharged from an electrolytic tank, but it can be diluted with an inert gas such as nitrogen gas or air to have a chlorine gas concentration of less than 97% by volume. , preferably used at 90-96% by volume. If the chlorine gas concentration exceeds 97% by volume, phenomena such as ignition and explosion will occur at the liquid interface of the dry carbide slag suspension, making it impossible to safely and stably produce an exposure solution. Also, if the chlorine gas concentration is too dilute, the amount of gas introduced will increase, which is undesirable.
Capacity% or more is better. In the present invention, the method of introducing chlorine gas into the dry carbide slag suspension and causing an absorption reaction is to add water to general slaked lime, and make the resulting lime emulsion absorb and react with chlorine gas to produce a bleaching solution. This can be carried out by a conventionally known method. For example, a chlorine gas absorption tower and a lime emulsion circulation tank are installed, lime emulsion is sprayed or showered from the top of the chlorine gas absorption tower, and chlorine gas is introduced from the bottom of the chlorine gas absorption tower. Then, while the lime emulsion is flowing down, chlorine gas is absorbed and reacted with the lime emulsion. The bottom liquid of the absorption tower is received in a liquid circulation tank and sent to the top of the absorption tower again by a pump, and the effective chlorine concentration of calcium hypochlorite is successively increased to complete the reaction. A method in which fine bubbles of chlorine gas are blown into the bottom of a tank-type lime emulsion tank equipped with an agitator using, for example, a Natsushi pump, and the lime emulsion absorbs and reacts, gradually increasing the effective chlorine concentration to complete the reaction. A method in which chlorine gas is blown into an eductor installed in the middle of the circulation lime emulsion piping to cause an absorption reaction in the lime emulsion. It can be manufactured by a batch method or a continuous method. The present invention will be explained in more detail below with reference to Examples. Example 1 Fill a 1 m ³ tank with a stirrer with 780 ml of water,
Dry carbide slag (manufactured by Company A, calcium hydroxide 93.8%, moisture content 5.8%, impurities are
A dry carbide slag suspension was obtained. This suspension was circulated by a pump, and a water cooler was installed in the middle to keep the temperature of the suspension below 25°C. Next, nitrogen gas was injected into the chlorine gas at a concentration of 99.9% by volume obtained from a chlorine cylinder, and the chlorine gas diluted to a concentration of 96.8% by volume was gradually added in small bubbles from the bottom of the tank to generate unreacted chlorine gas at the liquid interface. While controlling the amount of dilute chlorine gas introduced, the effective chlorine concentration can be increased.
We were able to safely and stably produce an 8.4% bleaching solution without any ignition phenomenon. Example 2 Dry carbide slag is calcium hydroxide manufactured by Company B
86.1%, water content 1.1% (impurities are from Company B analysis values in Table 1), and the chlorine gas is 97.8% by volume chlorine gas generated from a salt electrolyzer, and waste gas from the production of liquefied chlorine is used. (Chlorine purity: 78% by volume, impurities include oxygen, carbon dioxide, nitrogen, etc.) was mixed in small amounts to dilute it to a purity of 96.4% by volume. This chlorine gas was introduced under stirring in the same manner as in Example 1, and a bleaching solution containing 7.8% available chlorine could be safely and stably produced without any ignition phenomenon. Comparative Example 1 The 99.9% by volume chlorine gas obtained from the chlorine cylinder in Example 1 was directly introduced into the dry carbide slag suspension without dilution. In the latter half of the reaction, when the liquid pH is below 11.9, 10
A small spark ignition phenomenon occurs at a frequency of 15 times per minute.
The introduction of chlorine gas was discontinued. Comparative Example 2 In Example 1, nitrogen gas was injected into 99.9% by volume chlorine gas obtained from a chlorine cylinder, and the chlorine gas diluted to 97.6% was introduced into the dry carbide slag suspension. The ignition of small sparks was observed on several occasions, and the introduction of chlorine gas was discontinued. Comparative Example 3 In Example 2, when the mixture of liquefied chlorine waste gas was stopped and raw chlorine gas with a purity of 97.8% by volume from the electrolytic tank was used as it was, ignition was observed at a frequency of once every 10 minutes. , the introduction of chlorine gas was discontinued.

Claims (1)

[Claims] 1 Sprinkle water on calcium carbide to generate acetylene gas, add water to the dry carbide slag produced as a by-product from a dry acetylene gas generator, introduce chlorine gas into the resulting dry carbide slag suspension, In a method for producing a bleaching solution containing calcium hypochlorite as a main component by absorbing and reacting the dry carbide slag suspension, the chlorine gas is added to the dry carbide slag suspension at a concentration of less than 97% by volume. A method for producing a bleaching solution using dry carbide slag, which is characterized by introducing the bleaching solution into the solution.