KR860000556B1 - Purfication of hydro chloric acid - Google Patents

Abstract

Purified hydrochloric acid was prepd. with low energy consumption by reaction between alkali chloride and sulfuric acid. Produced crude hydrogen chloride vapor(8) contg. reactants or byproduct such as alkali sulfate as impurities is circulated and washed in a packed tower(1) with satd. hydrochloric acid(6,7) at ambient temp. or 50≰C, and dissolved in water. Aq. soln. of HCl is distd. again to evaporate HCl vapor absorbed again in water.

Description

Method of producing purified hydrochloric acid

Figure is a hydrogen chloride gas washing apparatus used in the present invention,

* Explanation of symbols for main parts of the drawings

1: charging tower 2: charging unit

3: hydrogen chloride gas introduction chamber 4: saturated hydrochloric acid dispersion chamber

5: mist separator 6: saturated hydrochloric acid tank

7: pump 8: hydrogen chloride gas introduction pipe

9: saturated hydrochloric acid circulation pipe 10: hydrogen chloride gas outlet pipe after washing

11: mist separation valve 12: sampling valve

The present invention relates to a method for producing purified hydrochloric acid, and more particularly, to a method for directly producing concentrated hydrochloric acid containing less impurities from hydrogen chloride gas generated by reacting sulfuric acid with alkali chloride.

Hydrogen chloride is reacted with sulfuric acid to generate hydrogen chloride, which is then absorbed in water to obtain hydrochloric acid (hereinafter referred to as denaturation method), and does not consume a large amount of power like electrolysis of alkali chloride. It is a technique that can be thought differently when energy saving is desired since it can be obtained directly and useful alkali sulfate can be obtained simultaneously.

However, hydrochloric acid by the modification method is mixed with hydrogen chloride generated in dust or mist as impurities such as alkali chloride, sulfuric acid, impurities contained in them, or alkali sulfate generated during the reaction of the modification method. Therefore, hydrochloric acid prepared by absorbing such hydrogen chloride in water is more impure than hydrochloric acid from hydrogen chloride obtained by reacting chlorine and hydrogen, and requires purification by distillation and resorption for the chemical industry.

There is no known technique for producing purified hydrochloric acid directly from hydrogen chloride by the above modification method. Therefore, purified hydrochloric acid is produced by purifying hydrogen chloride generated by reacting alkali chloride with sulfuric acid in the modification method and then absorbing it in water. The technique to do is not known.

The present inventors have made a careful study on the purification method in which impurities in the modification reaction are not incorporated into the modified hydrochloric acid in consideration of this fact of hydrochloric acid by the modification method (hereinafter referred to as modified hydrochloric acid). The present invention was completed by finding that the hydrogen chloride generated by the reaction was reacted with saturated hydrochloric acid to sufficiently remove dust such as potassium sulfate and sulfuric acid mist (hereinafter sometimes referred to as mist sulfate).

As is evident from the above description, it is an object of the present invention to provide a method for producing a modified hydrochloric acid, which does not require a special purification step such as distillation and resorption. Another object is to provide purified hydrochloric acid prepared by the above method.

This invention is a method of following (1)-(5).

(1) A method for producing purified hydrochloric acid in which hydrochloric acid obtained by absorbing hydrogen chloride gas generated by reacting alkali chloride with sulfuric acid in water is distilled, and the hydrogen chloride gas generated is absorbed into water. Method for producing purified hydrochloric acid directly without distillation, characterized in that the first circulating washing with saturated hydrochloric acid at room temperature to 50 ℃ and then absorbed in water without absorption.

(2) The method according to the above (1), wherein the alkali chloride is sodium chloride or potassium chloride.

(3) The method according to the above (1) to (2), which contains 1 to 5% by weight of alkali sulfate in hydrochloric acid at a saturated concentration.

(4) The method as described in said (1)-(3) whose temperature of the hydrogen chloride gas at the time of washing | cleaning is normal temperature-100 degreeC, and the temperature of hydrochloric acid of saturation concentration is normal temperature-50 degreeC.

(5) The method according to the above (1) to (4), wherein the hydrogen chloride gas before washing is washed with sulfuric acid to cool the temperature of the gas to room temperature to 100 ° C.

Hereinafter, the configuration and effects of the present invention will be described in detail.

A) Hydrogen chloride gas (hereinafter referred to simply as hydrogen chloride gas) used in the present invention is obtained by reacting alkali chloride with sulfuric acid. This reaction may be a so-called dry method in which alkali chloride is reacted with sulfuric acid in a solid phase or a so-called wet method in which sulfuric acid is reacted with an aqueous solution of alkali chloride. However, in the case of the wet method, the generated hydrogen chloride is dissolved in the original alkali chloride aqueous solution, and it is necessary to separate the hydrogen chloride gas by separate distillation or the like, thereby increasing the required preprocess.

The so-called dry method described above reacts KCI with concentrated sulfuric acid in the presence of alkali chloride, for example, in the following two steps of the following formulas (1) and (2).

KCI + H ₂ SO ₄ → KHSO ₄ + HCI... … … … … (One)

KCI + KHSO ₄ → K ₂ SO ₄ + HCI... … … … … (2)

Reaction of Formula (1) advances rapidly at the temperature before and behind 100 degreeC. On the other hand, the reaction of the formula (2) is an endothermic reaction, it takes a temperature of 300 to 400 ℃ and several hours to complete the reaction.

The so-called wet method described above is a mixture of alkali chloride, for example sulfuric acid, mixed with KCI aqueous solution to heat the reaction of the above formula (1) and (2) in an aqueous solution to obtain a K ₂ SO ₄ hydrochloric acid solution, This solution is distilled to generate hydrogen chloride gas. In the wet process, the reactions of formulas (1) and (2) proceed smoothly at a temperature of 200 ° C. or less, and are completed by distilling and separating HCI.

In the dry method, it is difficult to obtain 100% hydrogen chloride gas, and 30 to 60% by volume of air and water vapor are mixed, but the embodiment of the present invention is not affected. In the wet method, impurities (sulfuric acid, alkali sulfate) to be removed in the hydrogen chloride gas generated by distillation are significantly less than in the dry method, but can be purified by the method of the present invention.

In either case, the major solid or liquid phase impurities are sulfuric acid, alkali sulfate and iron, and it is natural that the target is hydrochloric acid because the moisture and air are not impurities. The concentration of these impurities is about 10 to 500 ppm of sulfuric acid (H ₂ SO ₄ ), 0.5 to 50 ppm of alkali sulfate and 0.5 to 20 ppm of iron (Fe) in the case of dry-modified hydrogen chloride gas. When concentrated hydrochloric acid is produced by absorption in hydrochloric acid, most of it moves into concentrated hydrochloric acid. This concentrated hydrochloric acid is distilled to produce hydrogen chloride, and about 20% dilute hydrochloric acid as distillation residue is reused for absorption of dry-modified hydrogen chloride gas.Alkali sulfuric acid sulfate and iron sulfate as impurities in the hydrochloric acid Accumulate and the absorption capacity is lowered. Therefore, in the method of the present invention, the modified hydrochloric acid gas with concentrated hydrochloric acid described in b) is washed for producing purified hydrochloric acid.

Prepared as described above, the "first generation hydrogen chloride gas" used in the present invention is not directly absorbed in water as in the conventional method, but is first washed with saturated hydrochloric acid as described below and purified into a gaseous phase. By this purification, the hydrogen chloride gas is purified to the extent that directly purified hydrochloric acid is obtained when absorbed into water.

B) The saturated concentration of hydrochloric acid (hereinafter referred to as washing hydrochloric acid) used in the present invention is not required to be produced by absorbing pure hydrogen chloride into pure water, and modified hydrogen chloride is used for water (chemical industry). It may be absorbed in raw material water or deionized water) and saturated. The concentration does not have to be strictly 35% by weight or more before the start of use, and may be a suitable concentration (for example, 20 to 32% by weight) in consideration of the increase in concentration or saturation due to absorption of hydrogen chloride gas in use. However, of course this concentration must reach a saturation concentration at a suitable stage after the start of the process of the invention. Otherwise, the yield of the hydrogen chloride gas after washing will fall. In addition, the hydrochloric acid for washing contains a small amount of sulfuric acid, alkali sulfate, and iron as a result of absorbing impurities in the gas to be treated during use, but the allowable concentration is 0 to 10% by weight as H ₂ SO ₄ , It is 0 to 10% by weight as alkali sulfate and 0 to 1,000 ppm as iron. If the concentration of H ₂ SO ₄ or alkali sulfate is more than 10% by weight or the iron content is more than 1,000 ppm, the mist or dust generated when washing with washing hydrochloric acid reverses the concentration of impurities in the hydrogen chloride gas after washing. There is concern to raise. What is unusual about the above allowable concentration is that 1 to 5% by weight of the alkali sulfate concentration (0 to 10% by weight) in washing hydrochloric acid is better than 1% by weight or more than 5% by weight. See example). Although this reason is not clear, it is thought that it is related with the physical property of a boundary membrane in the contact dissolution of alkali sulfate (solid dust) and a washing | cleaning liquid.

Using the hydrochloric acid for washing in the concentration and composition as described above, the hydrogen chloride gas described in a) above is washed under the conditions described in a).

流)접촉방식이어도, 액중 가스취입방식이어도 좋으나, 대량의 가스속의 미량의 불순물을 제거한다는 목적에서 기, 액의 접촉면적을 최대한으로 하는 동시에 동력 소비의 절약이 가능한 접촉방식(예를들면, 충전탑 사용)이 바람직한다. 기, 액량비(용량비)는 처리량, 즉, 발생한 염화수소가스 N㎥/hr와 세척액 사용량N㎥/hr의 용량비로서 10 내지 1000, 바람직하게는 50 내지 500이고 사용하는 장치에 따라 다르다. 또, 액중 가스취입방식에서는 세척액을 순환시킬 필요가 없으므로 기, 액량비는 1내지 100처럼 세척액량을 향류(병류)접촉방식의 경우보다 많게 하지 않으면 안된다. 다음에 b) 온도는 염화수소가스와 세척액이 동일한 필요는 없고, 건식법으로 수득한 염화수소가스는 발생후의 냉각을 고려하여도 50℃내지 100℃인 것이 많으나, 본 발명 방법으로는 이 염화수소가스의 공급시의 온도가 상온 내지 100℃이면 적합하게 실시할 수 있다. 건식법 변성염산용의 염화수소가스의 온도는 변성로내의 온도가 350℃ 내지 400℃의 고온이므로, 변성로를 나온 후에도, 예를들면, 150℃내지 250℃의 온도를 유지하고 있다. 이것을 간접적으로 물로 냉각할 수도 있지만, 열 교환기의 전열벽면이 황산 미스트 등으로 오염되어 전열계수가 10일 내지 1개월 등의 단기간으로 대폭적으로 저하하기 쉬우므로 60내지 80중량%의 실온 내지 80℃의 황산으로 세척하여 당해 염화수소가스 온도를 100℃이하로 냉각시키면 쉽고 확실하게 냉각시킬 수 있는 기액(氣液)의 접촉 조건은 온도관계를 제외하고 본 발명 방법의 염화수소가스의 포화농도의 염산에 의한 세척에 준하여 행할 수가 있다. 그리고, 이 냉각방법에 의하여 냉각후의 당해 염화수소가스중의 황산 혹은 황산알카리의 농도가 증가하는 일은 없다. 한편, 세척액으로서의 포화 농도의 염산의 온도는 상온 내지 50℃이면 좋고, 염화수소가스의 세척에 의하여 당해 온도가 50℃를 대폭적으로 초과하는 경우는 당해 염산을 순환중에 별도로 냉각시키면 좋다. 또, b) 세척처리되는 염화수소가스의 압력은 한정되지 않지만 세척장치내에서의 압력손실을 고려하여 10내지 100mmHg/G정도이면 충분하다. 그러나, 물론, 예를들면 1kg/㎠등의 압력하에 세척하는 것도 상관없다.C) washing conditions of the method of the present invention, a) type and gas-liquid ratio, b) temperature and pressure, c) other. a) The type of washing is not limited and countercurrent or cocurrent

Although it may be a contact method or a gas injection method in a liquid, a contact method that maximizes the contact area of gas and liquid and saves power consumption in order to remove a small amount of impurities in a large amount of gas (for example, charging). Tower) is preferred. The amount / volume ratio (capacity ratio) is 10 to 1000, preferably 50 to 500, as a capacity ratio of the throughput, that is, the generated hydrogen chloride gas Nm 3 / hr and the amount of washing liquid used Nm 3 / hr, depending on the apparatus used. In addition, in the liquid gas blowing method, there is no need to circulate the washing liquid, so the liquid and liquid ratio must be higher than that of the countercurrent (cocurrent) contacting method, such as 1 to 100. B) The temperature does not have to be the same as that of the hydrogen chloride gas and the washing liquid, and the hydrogen chloride gas obtained by the dry method is often in the range of 50 ° C to 100 ° C even in consideration of cooling after generation. The temperature can be suitably carried out if the temperature is from room temperature to 100 ° C. Since the temperature of the hydrogen chloride gas for dry process modified hydrochloric acid is 350 degreeC-400 degreeC high temperature in a modified furnace, even after exiting a modified furnace, the temperature of 150 degreeC-250 degreeC is maintained, for example. It may be indirectly cooled with water, but the heat transfer wall surface of the heat exchanger is contaminated with sulfuric acid mist or the like, and the heat transfer coefficient is easily reduced in a short time such as 10 days to 1 month. The contact conditions of the gas-liquid which can be easily and reliably cooled by washing with sulfuric acid and cooling the hydrogen chloride gas temperature below 100 ° C are washed by hydrochloric acid in the saturated concentration of hydrogen chloride gas of the method of the present invention except temperature relation. Can be performed according to By this cooling method, the concentration of sulfuric acid or alkali sulfate in the hydrogen chloride gas after cooling does not increase. On the other hand, the temperature of the hydrochloric acid of the saturated concentration as a washing | cleaning liquid should just be normal temperature-50 degreeC, and when the said temperature greatly exceeds 50 degreeC by washing | cleaning with hydrogen chloride gas, the said hydrochloric acid may be cooled separately in circulation. B) The pressure of the hydrogen chloride gas to be washed is not limited, but 10 to 100 mmHg / G is sufficient in consideration of the pressure loss in the washing apparatus. However, of course, you may wash | clean under pressure, such as 1 kg / cm <2>, for example.

D) Degree of removal of impurities by washing (Effect): By washing the hydrogen chloride gas as a) above with saturated hydrochloric acid under the same conditions as above), each impurity can be removed as follows. That is, for example, sulfuric acid concentration is reduced from 200ppm to 0.3ppm, alkali sulfate concentration is 10ppm to 0.1ppm, iron concentration is reduced from 1ppm to 0.02ppm so that the purified hydrogen chloride gas is absorbed into water, Purified hydrochloric acid can be easily prepared with sulfuric acid concentration less than 1ppm 0.1ppm, alkali sulfate concentration 0.3-0.1, iron concentration 0.1-0.02ppm. Hereinafter, although an Example is described based on drawing, these do not limit this invention.

Example 1

Saturated hydrochloric acid is dispersed from the saturated hydrochloric acid tank 6 through the saturated hydrochloric acid circulation pipe 9, the pump 7, and the above pipe 9 in the saturated hydrochloric acid dispersion chamber of the packed column 1 having a diameter of 300 mm and a height of 3 m. Denatured hydrogen chloride gas 20N at 50 ° C. from the hydrogen chloride gas introduction tube 8 while the dispersed hydrochloric acid diffuses almost uniformly in the charging part 2 and flows downward to the saturated chloride channel 6 via the hydrogen chloride introduction chamber 3 and the circulation pipe 9. M 3 / hr is introduced. The concentration composition of the saturated hydrochloric acid is HCI 35% by weight, H ₂ SO ₄ 3% by weight, K ₂ SO ₄ 1% by weight, the circulation amount is 300kg / hr, the liquid temperature is 50 ℃. On the other hand, the composition of the hydrogen chloride gas supplied is 40 vol% of hydrogen chloride, and the remainder is a trace amount of impurities containing most of the air and impurities in the first table described later. As described above, the introduced hydrogen chloride gas rises while being washed with saturated hydrochloric acid in the packing part of the packed column 1 and reaches the hydrogen chloride gas outlet tube 10 after washing through the saturated hydrochloric acid dispersing chamber 4 and the mist separator 5, and thereafter, known hydrogen chloride gas. Absorption in water in an absorption tower produces purified concentrated hydrochloric acid. In addition, the mist separation valve 11 patted on the gas outlet pipe 10 separates the mist still remaining by the secondary mist separator 5 '(not shown) as necessary. The impurity amounts in the before and after washing of the hydrogen chloride gas carried out as described above are shown in the following first table. The gas was collected from the valves 12 and 11 using an analytical absorption bottle, and the impurity concentration in the first table was expressed as a reference value of 35 wt% hydrochloric acid.

[Table 1]

Impurity Concentration Before and After Washing (Ⅰ)

As is clear from the above table, the concentration of each impurity is greatly reduced by the saturated hydrochloric acid washing of the method of the present invention, and the hydrochloric acid obtained by absorbing the hydrogen chloride gas after washing in water is used for the chemical industry for these impurities. It is obvious that it is purified to a sufficient degree.

Example 2

Except using the diagram of the apparatus used in that 35% by weight of a saturated hydrochloric acid HCI, H ₂ SO ₄ 0.1 wt.%, K ₂ SO ₂ 0.1% by weight was prepared by performing the same. The results are shown in the second table.

[Table 2]

Impurity Concentration Before and After Washing (Ⅱ)

As is clear from the above table, the effect of removing impurities by washing is remarkable, and it is clear that the hydrogen chloride gas for hydrochloric acid for chemical industry is purified to a sufficient degree.

However, since the concentration of potassium sulfate in the washing saturated hydrochloric acid is lower than in the case of Example 1, the effect of removing K ₂ SO ₄ by washing is slightly lower than in the case of Example 1.

Claims (1)

In the method for producing purified hydrochloric acid, in which hydrochloric acid obtained by absorbing hydrogen chloride gas generated by reacting alkali chloride with sulfuric acid in water is distilled to absorb hydrogen chloride gas generated in water, the hydrogen chloride gas generated for the first time is not directly absorbed into water. Method for producing purified hydrochloric acid, characterized in that first circulating washed at room temperature to 50 ℃ with saturated hydrochloric acid and then absorbed in water.

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