CN101139101B - Method for removing magnesium ion and calcium ion in middle-degree brine in salt-field - Google Patents

Abstract

The present invention relates to a method to wipe off magnesium hydronium and calcium hydronium by the moderate brine of salt field so as to improve sodium chloride output and quality in a sea salt production zone. When the brine of salt field reaches to 10 to 18 degrees Be', the magnesium hydronium is wiped off by electric lime waste residues. The amount ratio of the electric lime to the brine is 1 : 2.5 to 1 : 4. When the concentration of the electric lime reaches to 30 to 60 g/l, the pH value of the brine in the magnesium wiping off process keeps on 11 to 12.5. When the brine approaches tosaturation, mirabilite and a few sodium carbonates are added in the brine to wipe off rest calcium hydronium. The invention leads the composition of beach field brine to generate qualitative change and reduces vaporizing impedance. The brine salt producing amount of unit volume and the potassium chloride content in the salt producing mother liquor have been improved greatly. The invention has notonly reduced crystallization area, improved salt quality, but also simplified salinization technics. Under the same output and irrigating pool depth, the invention can save 21 percent beach field area. The production can be increased by 10 percent under the same production area.

Description

The method that salt pan moderate bittern is removed magnesium ion and calcium ion

Technical field

The present invention relates to the Salt production district uses salt pan moderate bittern to remove magnesium ion and calcium ion to improve sodium chloride output and method for quality.

Background technology

Contain Na in the seawater ⁺, K ⁺, Mg ²⁺, Ca ²⁺, Cl ^-, SO ₄ ^2-Plasma, concentrate in the salt-making process at seawater, raising along with bittern concentration, most of calcium sulphate crystal is separated out in crystallization during 12～23 ° of Be ', bittern concentration reaches 24.8 ° of Be ' precipitated sodium chloride crystal gradually when above, but when the sodium-chlor crystallization, because the influence of weather, edaphic condition has comprised Mg in the space that sodium chloride crystal generation druse produces ²⁺, Ca ²⁺, SO ₄ ^2-Plasma, these ions also are adsorbed on sodium-chlor xln surface simultaneously, have reduced the purity of sodium-chlor.Generally, Exposure to Sunlight crude salt SO ₄ ^2-Content is 0.3～0.8%, Ca ²⁺Content 0.1～0.3%, high energy reaches 1%, mainly with CaSO ₄2H ₂The O form exists, and Mg ²⁺Content 0.1～0.4%, bigger to salt matter influence, and mainly with MgSO ₄7H ₂O, MgCl ₂6H ₂The form of O exists, Mg ²⁺Content determined the smooth degree of sodium chloride crystal structure and plane of crystal, the height of moisture content is proportional in its content and the crude salt.We can say Mg ²⁺, Ca ²⁺, SO ₄ ^2-Isoionic existence is the key that directly influences salt quality.Have, in salt-making process, along with the raising of bittern concentration, the magnesium chloride in the bittern, sal epsom isoconcentration improve gradually, and the viscosity of bittern is improved gradually again, and bittern evaporation intensity reduces, and the one-tenth halogen amount in the unit time is relative low with product salt amount.In addition, crude salt is as the raw material of chlor-alkali industry, and raw material contains higher Mg ²⁺, Ca ²⁺Ion need be dissolved as salt solution with salt, and adopts caustic soda one soda ash method to remove Mg ²⁺, Ca ²⁺Ion reaches the requirement of caustic soda or soda ash raw materials for production, therefore, reduces the Mg that contains in the salt ²⁺, Ca ²⁺Ion has improved the quality and the output of salt, has reduced the bittern purifying cost of chlor-alkali industry again.

Summary of the invention

In order to solve the deficiencies in the prior art, the invention provides the method that a kind of salt pan moderate bittern is removed magnesium ion and calcium ion.Technology of the present invention is as follows:

Reach 10～18 ° of Be ' times in Bittern of Salt Pan, adopt the Calcium Carbide Ash waste residue to remove magnesium ion, Calcium Carbide Ash and bittern amount proportioning are 1:2.5～1:4, and the concentration of Calcium Carbide Ash reaches 30～60g/l, and the pH value of bittern remains on 11～12.5 in the demagging process; Bittern is adding saltcake when saturated and a small amount of yellow soda ash is removed the residue calcium ion.

The concrete grammar step is as follows, as shown in Figure 1:

1) Ca (OH) ₂The preparation of ash breast

In the continous way settling vat that a band stirs, be 1:2.5～1:4 by weight ratio with Calcium Carbide Ash and bittern, grey Ruzhong Ca (OH) ₂Content is 30～60g/l, separates in settling vat simultaneously and discharges lime-ash;

2) remove Mg ²⁺

According to Mg in the bittern ²⁺Content, control Calcium Carbide Ash breast consumption is excessive in 10%, adopts continous way precipitation reaction groove, and the Calcium Carbide Ash breast that emulsification is good slowly joins in the bittern, and pH is controlled to be at 11～12.5 o'clock, Mg ²⁺With OH ^-Can be fully in conjunction with forming insoluble substance Mg (OH) ₂, Mg in the bittern ²⁺Content is 0; Mg (OH) ₂Separate from the bottom by the continous way subsider, enter thickener, obtain finished product Mg (OH) through dehydration, drying then ₂, subsider top bittern enters into the salt pan and continues evaporation.

3) remove Ca ²⁺

Owing in bittern, added a large amount of Calcium Carbide Ash breasts, increased the Ca in the bittern ²⁺Content, when bittern concentration is 20～25 ° of Be/, Tanaka adds Na at salt ₂CO ₃, the CaCO of formation indissoluble ₃, Ca in the control bittern ²⁺Concentration drops to below the 300mg/l.

The waste residue that described Calcium Carbide Ash is discharged for chlor-alkali production factory.

Utilize salt manufacturing field moderate bittern at 10～23 degree Beaume, chlor-alkali plant is contained Ca (OH) ₂Calcium Carbide Ash and bittern be mixed with the Calcium Carbide Ash breast by a certain percentage, the settlement separate lime-ash part that goes out to be insoluble to bittern is with Ca (OH) ₂The ash breast joins in the bittern.Ca (OH) ₂With the Mg in the bittern ²⁺Take place to answer, the pH value of control bittern remains on 11～12.5, generates water-fast Mg (OH) ₂, add flocculation agent and make Mg (OH) ₂Be deposited to reactor bottom, because the Ca in the bittern ²⁺Ion content increases, and has increased CaSO ₄Degree of supersaturation, at this moment bittern continues evaporation and can separate out a large amount of calcium sulfate (CaSO ₄.2H ₂O), thus reduced the SO in the bittern ₄ ^2-, when saturated, adopt saltcake to remove Ca in the bittern at bittern ²⁺, remaining Ca ²⁺Remove with a spot of yellow soda ash.

Technological principle:

The first step reaction: Mg ²⁺+ Ca (OH) ₂=Mg (OH) ₂↓+Ca ²⁺

Ca ²⁺+SO ₄ ^2-＝CaSO ₄↓

Second step reaction: Ca ²⁺+ SO ₄ ^2-=CaSO ₄↓

Three-step reaction: Ca ²⁺+ CO ₃ ^2-=CaCO ₃↓

The present invention makes field, beach bittern form the variation that matter takes place, and has reduced evaporative resistance, and KCE content will improve greatly in the salt manufacturing amount of bittern unit volume and the salt-making mother liquor, both reduce crystal plane and amass, improved salt matter, simplify salinization technology again.Under with equal yield line and filling tank depth, can save 21% field, beach area; Under equal production area condition, can increase production 10%.

Description of drawings

Fig. 1: process flow diagram of the present invention.

Embodiment

Embodiment 1:

The waste residue Calcium Carbide Ash that selected chlor-alkali plant is produced is as the Mg in the basic raw material removal bittern ²⁺, make Mg ²⁺Separate out with the magnesium hydroxide form, select the Calcium Carbide Ash waste residue after chemical plant, Dagu, Tianjin produces acetylene gas for use.The bittern starting point concentration is 11 ° of Be/, and its concrete operations are as follows:

1) preparation of Ca (OH) 2 ash breasts

In the continous way settling vat that a band stirs, be 1:3 by weight ratio with Calcium Carbide Ash and bittern, grey Ruzhong, Ca (OH) ₂Content is 40g/l, separates in settling vat simultaneously and discharges lime-ash.

2) remove Mg ²⁺

According to Mg in the bittern ²⁺Content calculates Calcium Carbide Ash breast consumption, and the Calcium Carbide Ash breast consumption is excessive is controlled in 5%.Adopt a continous way precipitation reaction groove, the Calcium Carbide Ash breast that emulsification is good slowly joins in the bittern, and pH is controlled to be at 11 o'clock, Mg ²⁺With OH ^-Can be fully in conjunction with forming insoluble substance Mg (OH) ₂, Mg in the bittern ²⁺Content is 0.Mg (OH) ₂Separate from the bottom by the continous way subsider, enter a thickener, obtain finished product Mg (OH) through dehydration, drying then ₂, use as the boiler flue gas desulfurizer.Subsider top bittern enters into the salt pan and continues evaporation.

3) remove Ca ²⁺

Owing in bittern, added a large amount of Calcium Carbide Ash breasts, increased the Ca in the bittern ²⁺Content is 20 ° of Be ' times at bittern concentration, drops into saturated sodium sulfate salt Tanaka, removes most of Ca ²⁺, treating that bittern concentration reaches 24.8 ° of Be ', Tanaka drops into Na at salt ₂CO ₃, the CaCO of formation indissoluble ₃Thereby, with Ca in the bittern ²⁺Concentration drops to below the 200mg/l.

Embodiment 2;

Select the Calcium Carbide Ash waste residue after chemical plant, Dagu, Tianjin produces acetylene gas for use.The bittern starting point concentration is 13.6 ° of Be ', and its concrete operations are as follows:

1) Ca (OH) ₂The preparation of ash breast

In the continous way settling vat (Emulsion cask) that a band stirs, be 1:4 by weight ratio with Calcium Carbide Ash and bittern, grey Ruzhong

Ca (OH) ₂Content is 30g/l, separates in settling vat simultaneously and discharges lime-ash.

2) remove Mg ²⁺

According to Mg in the bittern ²⁺Content calculates Calcium Carbide Ash breast consumption, and the Calcium Carbide Ash breast consumption is excessive is controlled in 5%.Adopt a continous way precipitation reaction groove, the Calcium Carbide Ash breast that emulsification is good slowly joins in the bittern, and pH is controlled to be at 11.8 o'clock, Mg ²⁺With OH ^-Can be fully in conjunction with forming insoluble substance Mg (OH) ₂, Mg in the bittern ²⁺Content is 0.Mg (OH) ₂Separate from the bottom by the continous way subsider, enter a thickener, obtain finished product Mg (OH) through dehydration, drying then ₂, use as the boiler flue gas desulfurizer.Subsider top bittern enters into the salt pan and continues evaporation.

3) remove Ca ²⁺

Owing in bittern, added a large amount of Calcium Carbide Ash breasts, increased the Ca in the bittern ²⁺Content is when bittern concentration is that 23 ° of Be ' add Na salt Tanaka ₂CO ₃, the CaCO of formation indissoluble ₃Thereby, with Ca in the bittern ²⁺Concentration drops to below the 280mg/l.

Embodiment 3:

Select the Calcium Carbide Ash waste residue after chemical plant, Dagu, Tianjin produces acetylene gas for use.The bittern starting point concentration is 18 ° of Be ', and its concrete operations are as follows:

2) Ca (OH) ₂The preparation of ash breast

In the continuous emulsifying bucket that a band stirs, be 1:2.5 by weight ratio with Calcium Carbide Ash and bittern, grey Ruzhong Ca (OH) ₂Content is 60g/l, separates in settling vat simultaneously and discharges lime-ash.

2) remove Mg ²⁺

According to Mg in the bittern ²⁺Content calculates Calcium Carbide Ash breast consumption, and the Calcium Carbide Ash breast consumption is excessive is controlled in 10%.Adopt a continous way precipitation reaction groove, the Calcium Carbide Ash breast that emulsification is good slowly joins in the bittern, and pH is controlled to be at 12.5 o'clock, Mg ²⁺With OH ^-Can be fully in conjunction with forming insoluble substance Mg (OH) ₂, Mg in the bittern ²⁺Content is 0.Mg (OH) ₂Separate from the bottom by the continous way subsider, enter a thickener, obtain finished product Mg (OH) through dehydration, drying then ₂Subsider top bittern enters into the salt pan and continues evaporation.

3) remove Ca ²⁺

Owing in bittern, added a large amount of Calcium Carbide Ash breasts, increased the Ca in the bittern ²⁺Content, when bittern concentration is 24.5 ° of Be ', Tanaka adds Na at salt ₂CO ₃, the CaCO of formation indissoluble ₃Thereby, with Ca in the bittern ²⁺Concentration drops to below the 300mg/l.

The present invention proposes the method that salt pan moderate bittern is removed magnesium ion and calcium ion, be described by on-the-spot preferred embodiment, person skilled obviously can be in not breaking away from content of the present invention, spirit and scope to structure as herein described with the preparation method changes or suitably change and combination, realize the technology of the present invention.Special needs to be pointed out is, the replacement that all are similar and change apparent to those skilled in the artly, they are regarded as being included in spirit of the present invention, scope and the content.

Claims (1)

1. the method that salt pan moderate bittern is removed magnesium ion and calcium ion is characterized in that when Bittern of Salt Pan reaches 10～18 ° of Be/, adopts the Calcium Carbide Ash waste residue to remove magnesium ion, and the concrete grammar step is as follows:

1) Ca (OH) ₂The preparation of ash breast

In the continous way settling vat that a band stirs, be 1: 2.5～1: 4 by weight ratio with Calcium Carbide Ash and bittern, grey Ruzhong Ca (OH) ₂Content is 30～60g/l, separates in settling vat simultaneously and discharges lime-ash;

2) remove Mg ²⁺

According to Mg in the bittern ²⁺Content, control Calcium Carbide Ash breast consumption is excessive in 10%, adopts continous way precipitation reaction groove, and the Calcium Carbide Ash breast that emulsification is good slowly joins in the bittern, and pH is controlled to be at 11～12.5 o'clock, Mg ²⁺With OH ^-Can be fully in conjunction with forming insoluble substance Mg (OH) ₂, Mg in the bittern ²⁺Content is 0; Mg (OH) ₂Separate from the bottom by the continous way subsider, enter thickener, obtain finished product Mg (OH) through dehydration, drying then ₂Subsider top bittern enters into the salt pan and continues evaporation;

3) remove Ca ²⁺

Owing in bittern, added a large amount of Calcium Carbide Ash breasts, increased the Ca in the bittern ²⁺Content, when bittern concentration is 20～25 ° of Be/, Tanaka adds Na at salt ₂CO ₃, the CaCO of formation indissoluble ₃, Ca in the control bittern ²⁺Concentration drops to below the 300mg/l.