JP4382639B2 - Method for producing dihydrate gypsum - Google Patents
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- JP4382639B2 JP4382639B2 JP2004333668A JP2004333668A JP4382639B2 JP 4382639 B2 JP4382639 B2 JP 4382639B2 JP 2004333668 A JP2004333668 A JP 2004333668A JP 2004333668 A JP2004333668 A JP 2004333668A JP 4382639 B2 JP4382639 B2 JP 4382639B2
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Description
本発明は、二水石膏の製造方法に関する。
特に本発明は、廃硫酸を炭酸カルシウムにより中和して硫酸カルシウムの二水和物（以下、二水石膏と称する）を製造する方法であり、安定的に結晶粒の大きい石膏を製造することが可能な二水石膏の製造方法に関するものである。
The present invention relates to a method for producing dihydrate gypsum.
In particular, the present invention is a method for producing calcium sulfate dihydrate (hereinafter referred to as dihydrate gypsum) by neutralizing waste sulfuric acid with calcium carbonate, and stably producing gypsum with large crystal grains. The present invention relates to a method for producing dihydrate gypsum that can be used.
石膏は、天然のものが産出される他に、排煙脱硫廃水や各種金属製錬で生じる廃水を中和することによっても製造される。排煙脱硫廃水には亜硫酸が含まれているため、これを硫酸に酸化した後に炭酸カルシウムを添加し、二水石膏として沈澱させて回収するようにしている。 In addition to producing natural products, gypsum is also produced by neutralizing flue gas desulfurization wastewater and wastewater generated by various metal smelting. Since the flue gas desulfurization wastewater contains sulfurous acid, it is oxidized to sulfuric acid, calcium carbonate is added, and it is precipitated and collected as dihydrate gypsum.
二水石膏は主に石膏ボードやセメント原料として出荷されるが、一般に出荷時の水分含有率は10％以下となっており、そのためには結晶を粗大化する必要がある。結晶粒径の小さい石膏は、脱水性が悪く水分含有率が高くなるため、輸送費用が割高になる。また、その流動性の悪さからホッパー内でブリッジを生じて安定的な切出しができなくなるなど、ハンドリングが悪いだけでなく、使用先では添加量のばらつきが生じるなど品質面でも問題がある。 Dihydrate gypsum is shipped mainly as a raw material for gypsum board and cement. Generally, the moisture content at the time of shipment is 10% or less, and it is necessary to coarsen the crystals. Since gypsum with a small crystal grain size is poor in dehydration and has a high water content, transportation costs are high. Moreover, due to the poor fluidity, not only is handling difficult, such as a bridge formed in the hopper, making it impossible to stably cut out, and there is a problem in terms of quality, such as variations in the amount added at the point of use.
石膏のような極めて難溶性の塩は、反応時に多数の微細な結晶核が生じ、かつ結晶成長の速度が極めて遅いため、結晶の粗大化が難しく、反応槽で特別な技術を用いずに硫酸と炭酸カルシウムを反応させて生成した石膏は粒径が10〜20μｍと小さいことが多い。 Extremely sparingly soluble salts such as gypsum produce many fine crystal nuclei during the reaction, and the crystal growth rate is extremely slow, making it difficult to coarsen crystals. Gypsum produced by the reaction of calcium carbonate with calcium carbonate is often as small as 10 to 20 μm.
結晶を粗大化させる技術の一つとして、数基の反応槽を持つ場合に炭酸カルシウムスラリーを反応槽内にできるだけ均一に分散或いは散布するため噴射させ、石膏スラリーを循環させる方法がありその一例として、特許3170234号（出願人：三井金属鉱業株式会社）（特許文献1）の開示がある。 As one of the techniques for coarsening crystals, there is a method of circulating a gypsum slurry by spraying calcium carbonate slurry to disperse or disperse it as uniformly as possible in the reaction tank when there are several reaction tanks. Patent No. 3170234 (Applicant: Mitsui Mining & Mining Co., Ltd.) (Patent Document 1).
特許文献１では反応槽の液温を60℃以上にすることが望ましいとされているが、本発明者等が検討した結果、40℃前後が石膏の溶解度が高く、石膏が成長するために良いことを知見した。
また特許文献1の方法では、加温装置の設置が必要であり、耐熱性のある材質への変更が必要となる。
さらに特許文献１の方法では炭酸カルシウムをスラリー化させる設備も必要となる。一般的に廃硫酸の場合、炭酸カルシウムと反応させ生じた石膏スラリーを濾過した際に生じる濾液には不純物重金属が含まれているため、濾液を中和して重金属を除去する。
また、炭酸カルシウムをスラリー化させた場合には、液量が増え、その中和工程設備の能力増強も必要となる可能性がある。
In Patent Document 1, it is desirable that the liquid temperature in the reaction vessel is 60 ° C. or higher. However, as a result of studies by the present inventors, around 40 ° C. is high because the solubility of gypsum is high and gypsum grows. I found out.
Further, in the method of Patent Document 1, it is necessary to install a heating device, and it is necessary to change to a heat resistant material.
Furthermore, the method of Patent Document 1 requires equipment for slurrying calcium carbonate. In general, in the case of waste sulfuric acid, the filtrate produced when the gypsum slurry produced by the reaction with calcium carbonate is filtered contains heavy impurities, so the filtrate is neutralized to remove heavy metals.
In addition, when calcium carbonate is slurried, the amount of liquid increases and the capacity of the neutralization process equipment may need to be increased.
本発明は、粒径の大きな二水石膏を製造することができ、上記したような問題を解決することができる二水石膏の製造方法を提供することを目的としている。 An object of the present invention is to provide a method for producing dihydrate gypsum that can produce dihydrate gypsum having a large particle diameter and that can solve the above-described problems.
本発明者らは、上記の問題を解決すべく、以下の発明を成した。
即ち本発明は、
（１）廃硫酸および炭酸カルシウムから二水石膏を製造する方法であって、反応槽を少なくとも2以上直列に接続し、内１以上の反応槽に炭酸カルシウムを微粉状で添加すると共に反応槽の滞留時間合計を処理廃硫酸液量に対して13時間以上に保ち、かつ、最下流の反応槽から最上流の反応槽に処理廃硫酸液量の2.75倍以上に相当する液量の石膏スラリーを繰り返す二水石膏の製造方法。
In order to solve the above problems, the present inventors made the following invention.
That is, the present invention
(1) A method for producing dihydrate gypsum from waste sulfuric acid and calcium carbonate, wherein at least two reaction vessels are connected in series, and calcium carbonate is added in fine powder form to one or more of the reaction vessels. Maintain a total residence time of 13 hours or more with respect to the amount of treated waste sulfuric acid solution, and add a gypsum slurry with a liquid amount equivalent to more than 2.75 times the amount of treated waste sulfuric acid solution from the most downstream reaction tank to the most upstream reaction tank. Repeated method for producing dihydrate gypsum.
（２）前記反応槽の液温を35〜45℃に調整する上記（１）記載の二水石膏の製造方法。 (2) The method for producing dihydrate gypsum according to (1), wherein the temperature of the reaction vessel is adjusted to 35 to 45 ° C.
本発明によれば、
（１）本発明によって石膏粒子を粗大化することができるので、脱水性に優れた良質な石膏を製造することができる。
（２）また、炭酸カルシウムをスラリー状にせず、粉状のままの添加でも水分含有率10mass％以下の石膏が製造可能となる。
According to the present invention,
(1) Since the gypsum particles can be coarsened according to the present invention, a high-quality gypsum excellent in dewaterability can be produced.
(2) Moreover, it becomes possible to produce a gypsum having a moisture content of 10 mass% or less even when calcium carbonate is added in the form of powder without making it into a slurry.
（３）平均粒径が約70μｍ以上の粒径の石膏とすることにより、水分10mass%以下の石膏が出来る。また遠心分離機での水分除去に、好適な粒径である。 (3) By using gypsum having an average particle diameter of about 70 μm or more, gypsum having a water content of 10 mass% or less can be obtained. The particle size is suitable for removing water in a centrifuge.
以下本発明に関して、詳細に説明する。
本発明に関する対象の液は、廃硫酸液である。例えば、廃硫酸は、硫酸濃度が、15〜30mass%である。従って、炭酸カルシウムと反応させたとしても濃硫酸から石膏を製造する場合のように、発熱反応によって著しく高温とはならない。
Hereinafter, the present invention will be described in detail.
The liquid subject to the present invention is a waste sulfuric acid liquid. For example, the waste sulfuric acid has a sulfuric acid concentration of 15 to 30 mass%. Therefore, even if it reacts with calcium carbonate, it does not reach a very high temperature due to an exothermic reaction as in the case of producing gypsum from concentrated sulfuric acid.
本発明においては、反応槽を2以上直列に接続する。反応時間を保持すると同時に、石膏の溶質濃度をより均一にし、結晶成長に適切な過飽和度を維持するためである。
上記の内1以上に炭酸カルシウムを微粉状で添加する。炭酸カルシウムを添加する槽はできるだけ多い方が好ましい。
微粉とは、例えば 粒径が１〜100μmである。
ある程度の微粉である方が、表面積が大きくなり、硫酸とカルシウムの反応が進み易いからである。
In the present invention, two or more reaction vessels are connected in series. This is for maintaining the reaction time and at the same time making the gypsum solute concentration more uniform and maintaining a supersaturation level suitable for crystal growth.
Add calcium carbonate in fine powder form to one or more of the above. It is preferable to add as many tanks as possible to which calcium carbonate is added.
The fine powder has, for example, a particle size of 1 to 100 μm.
This is because the finer the powder, the larger the surface area and the easier the reaction between sulfuric acid and calcium.
反応槽での滞留時間は、処理廃硫酸量に対して、13時間以上が好ましい。
滞留時間が長い方が、粒子同士の結合或いは、晶出する時間も十分取れることから粒径の大きい二水石膏が得られるからである。
The residence time in the reaction tank is preferably 13 hours or more with respect to the amount of treated sulfuric acid.
This is because the longer the residence time, the longer the time for bonding or crystallization of the particles, and thus a dihydrate gypsum having a large particle size can be obtained.
また反応槽には、処理硫酸液量の2.75倍以上に相当する液量の石膏スラリーを繰り返す。
例えば、図１においては、最終の5槽目の反応槽から生成した石膏スラリーを繰り返している。
この繰り返しにより、局部的な石膏溶質濃度の上昇による微細結晶核の発生が抑制され、かつ繰り返された石膏の結晶がより成長するからである。
In the reaction tank, a gypsum slurry having a liquid volume corresponding to 2.75 times or more of the treated sulfuric acid liquid is repeated.
For example, in FIG. 1, the gypsum slurry generated from the final fifth reaction tank is repeated.
This is because by repeating this, the generation of fine crystal nuclei due to the local increase in the gypsum solute concentration is suppressed, and repeated gypsum crystals grow more.
反応槽での液温は、35から45℃が好ましい。この温度域が二水石膏の飽和準安定な濃度域が最も大きいと考えられるからである。飽和準安定な濃度とは、溶解度以上であり、かつ、核が発生し始める濃度である過溶解度より小さい濃度である。多くの研究者によるデータによると、二水石膏の溶解度が最も大きいのが約40℃である。また、一般に溶解度が大きいと飽和準安定な濃度域も大きくなるといわれている。
したがって粒径を大きく成長するために、好ましい温度と考えられるからである。
The liquid temperature in the reaction vessel is preferably 35 to 45 ° C. This is because this temperature range is considered to have the largest saturated metastable concentration range of dihydrate gypsum. The saturated metastable concentration is a concentration that is higher than the solubility and smaller than the supersolubility that is a concentration at which nuclei start to be generated. According to data from many researchers, dihydrate gypsum has the highest solubility at about 40 ° C. Further, it is generally said that the saturation metastable concentration range increases as the solubility increases.
Therefore, it is considered to be a preferable temperature in order to grow the particle size greatly.
図１に示す本発明に係わる石膏製造設備を用いて二水石膏の製造を行なった。なお、操業条件は下記の条件とした。
〔操業条件：〕
廃硫酸濃度：200〜250g/L
廃硫酸給液量：200L/min
廃硫酸温度：35℃
反応槽滞留時間：13.7h
石膏スラリー循環量：550L/min、270L/min
反応槽液温：40℃、50℃
反応槽3の溶液のpH：1.4〜1.8
シックナーの上澄液のpH：1.8〜2.2
石膏生産量：4t/h（乾燥重量）
この操業においては、底抜きをせず、溢流する（オーバーフロー）方式を採っているため、繰り返し量の多少に関係なく、滞留時間は、一定となる。
Dihydrate gypsum was produced using the gypsum production facility according to the present invention shown in FIG. The operating conditions were as follows.
[Operating conditions:]
Waste sulfuric acid concentration: 200-250g / L
Waste sulfuric acid supply volume: 200L / min
Waste sulfuric acid temperature: 35 ℃
Reactor residence time: 13.7h
Gypsum slurry circulation rate: 550L / min, 270L / min
Reaction vessel liquid temperature: 40 ℃, 50 ℃
PH of the solution in the reaction tank 3: 1.4 to 1.8
Thickener supernatant pH: 1.8-2.2
Gypsum production: 4t / h (dry weight)
In this operation, since the bottom is not drained and the system overflows (overflow), the residence time is constant regardless of the amount of repetition.
表1から明らかなように温度を40℃に設定し、石膏スラリーを給液量（廃硫酸給液量：200L/min）の約2.75倍（550L/min）循環させることにより石膏粒子が平均71.6μｍと粗大化し、水分含有率が、9.8mass%と低く、脱水性が良くなることが確認された。 As shown in Table 1, the temperature was set to 40 ° C, and the gypsum slurry was circulated approximately 2.75 times (550 L / min) of the feed rate (waste sulfuric acid feed rate: 200 L / min). It was confirmed that the film was coarsened to μm, the water content was as low as 9.8 mass%, and the dehydrating property was improved.
また、比較例2の如く石膏スラリー循環量が、1.35倍の270L/minでは、平均粒径41μｍと大きいものが出来ず、水分含有率も14.3mass%と高く脱水性も悪いものであった。 Further, as in Comparative Example 2, when the amount of circulating gypsum slurry was 1.35 times 270 L / min, an average particle size of 41 μm could not be obtained, the water content was as high as 14.3 mass%, and the dehydrating property was also poor.
更に、比較例１では、石膏スラリー循環量を多くした場合であっても、反応温度が、50℃と高いと平均59.3μｍと好ましい粒径の二水石膏は、得られず、水分含有率も11.6mass%と高く脱水性も悪いものであった。
１ 反応槽１
２ 反応槽２
３ 反応槽３
４ 反応槽４
５ 反応槽５
６ 撹拌機
７ 撹拌機
８ 炭酸カルシウムホッパー
９ 微粉状炭酸カルシウム
１０ ポンプ
１１ 石膏スラリー循環配管
１２ 石膏スラリーのシックナーへの送液配管
1 Reaction tank 1
2 Reaction tank 2
3 Reaction tank 3
4 Reaction tank 4
5 Reaction tank 5
6 Stirrer 7 Stirrer 8 Calcium Carbonate Hopper 9 Fine Powdered Calcium Carbonate 10 Pump 11 Gypsum Slurry Circulation Pipe 12 Gypsum Slurry Supply Pipe to Thickener
Claims (2)
2. The method for producing dihydrate gypsum according to claim 1, wherein the temperature of the reaction vessel is adjusted to 35 to 45 ° C.
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| JP2004333668A JP4382639B2 (en) | 2004-11-17 | 2004-11-17 | Method for producing dihydrate gypsum |
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| JP4382639B2 true JP4382639B2 (en) | 2009-12-16 |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| MX2011001116A (en) | 2008-07-31 | 2011-05-23 | Yoshino Gypsum Co | Process for continuous modification of dihydrate gypsum and modified dihydrate gypsum obtained by the process. |
| JP6172011B2 (en) * | 2014-03-24 | 2017-08-02 | 住友金属鉱山株式会社 | Gypsum manufacturing method |
| CN105819485B (en) * | 2016-03-29 | 2018-06-22 | 云南华联锌铟股份有限公司 | The method and apparatus of output gypsum from the acid-containing solution of zinc abstraction |
| CN109336159A (en) * | 2018-11-09 | 2019-02-15 | 陕西黑猫焦化股份有限公司 | Acetylene-formaldehyde process produces waste acid treatment technique caused by 1,4- butanediol |
| JP7451333B2 (en) | 2020-07-16 | 2024-03-18 | 株式会社トクヤマ | Method for precipitation of gypsum dihydrate particles |
| CN115477485B (en) * | 2022-09-06 | 2023-08-22 | 常州大学 | Method for preparing alpha-hemihydrate gypsum by utilizing azo dye sulfuric acid wastewater |
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