CN108502902B - Comprehensive treatment method for salt production mother liquor and salt mud - Google Patents
Comprehensive treatment method for salt production mother liquor and salt mud Download PDFInfo
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- C01—INORGANIC CHEMISTRY
- C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
- C01D3/00—Halides of sodium, potassium or alkali metals in general
- C01D3/04—Chlorides
- C01D3/06—Preparation by working up brines; seawater or spent lyes
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- C—CHEMISTRY; METALLURGY
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- C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
- C01D3/00—Halides of sodium, potassium or alkali metals in general
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Abstract
The invention discloses a comprehensive treatment method of salt production mother liquor and salt mud. The method comprises the following steps: adding lime with the particle size of 30-100 meshes and the purity of more than 60% into an emulsifying tank containing salt making mother liquor for emulsifying for 20-40 min; the mass ratio of the effective component calcium oxide in the lime to the magnesium ions in the salt making mother liquor is (105-110) multiplied by the purity: 1; pumping the emulsified substances into a mother liquor stirring reaction tank, fully reacting for 3-5 hours under a stirring state, and adjusting the pH value to be more than 11.4 until magnesium chloride is completely removed; pumping the reacted slurry into an original reaction barrel to be mixed with original halogen with the pH value of 6.8 so as to remove iron ions and manganese ions to obtain purified halogen, and controlling the pH value of the purified halogen to be 9.6-10 by supplementing alkali liquor; and carrying out solid-liquid separation on the purified halogen, and using the obtained clear liquid for preparing salt by vacuum evaporation. The invention has obvious magnesium removal effect on the salt making mother liquor, low cost and thorough solid-liquid separation, not only saves a gypsum filter pressing system, but also eliminates a series of environmental protection pressure caused by solid waste generated on the ground.
Description
Technical Field
The invention belongs to the technical field of salt production, and particularly relates to a comprehensive treatment method of salt production mother liquor and salt mud.
Background
The elm forest city is located in the most northern part of Shaanxi province, is a national level history culture famous city at the junction of loess plateau and blackjack desert, is a national energy and chemical engineering base, and is known as the Chinese 'Kowitter' because various underground resources aquatic weeds such as coal, oil, natural gas and rock salt are extremely abundant. The salt rock resources in the elmin market are rich, and the method has the characteristics of large area, large reserve and high grade. The exploratory reserves of the salt rocks in the region are 8854.55 trillion tons, and the future reserves are 6 trillion tons. The elm rock salt mineral mainly comprises blocky rock salt, sylvite and anhydrite, has a small amount of carnallite and potassium ferric salt, most of the ore grade belongs to first-grade products, the quality is pure, the highest sodium chloride content is 99.8 percent, the lowest sodium chloride content is 81.46 percent, the average sodium chloride content is more than 95 percent, and the elm rock salt mineral is a rare fine ore deposit in the history of salt mines in the world.
The vacuum salt preparation is a main mode for preparing salt by rock salt at present, brine is taken as a raw material, and the process of heating, evaporating, crystallizing, separating and drying the brine is carried out to obtain sodium chloride. The production method of salt production uses brine evaporation as a main unit, the solution is concentrated until sodium chloride is supersaturated and crystallized and separated out, secondary steam generated by evaporation enters a shell pass of a next-effect heating chamber as a heat source, and the evaporation process is analogized to the last effect. Each effect of steam is sequentially pushed to negative pressure (vacuum) from positive pressure, secondary steam generated in the last effect is introduced into a mixed condenser, is condensed by cooling water and then is discharged out of a system, non-condensed steam is pumped out by a vacuum unit or a steam jet pump to ensure the negative pressure (vacuum) state of the system, the effective temperature difference between the effects is ensured, and multi-effect evaporation is realized.
The brine is used as a raw material for preparing salt, and the quality of the brine is crucial to the salt preparation production. For the halite of elm, the impurity components of the brine are neither mirabilite type nor gypsum type completely, but calcium sulfate-calcium chloride-magnesium chloride type, that is, the halite brine belongs to calcium type brine, wherein calcium exists in the form of calcium sulfate and calcium chloride.
Therefore, brine needs to be purified before salt production. The existing brine purification mode adopts underground purification treatment, an underground dissolving cavity is used as a reactor, sodium sulfate is added into well injection water to react with dissolved calcium chloride to generate calcium sulfate so as to realize the aim of removing calcium, the solubility characteristic of the calcium sulfate is fully utilized, the solid-phase calcium sulfate is deposited at the bottom of the dissolving cavity of the salt well, and the calcium sulfate in the liquid phase returns to the ground. Along with the proceeding of an evaporation system, calcium sulfate is enriched in an evaporation tank, the content of feed liquid gypsum in the evaporation tank is controlled by discharging mother liquor, the mother liquor is concentrated by a horizontal screw centrifuge after being discharged, the centrifuged slag slurry enters a plate-and-frame filter press, the liquid phase enters a raw brine barrel for reutilization after being subjected to alkali addition and magnesium removal, and part of saturated brine is recovered. And (4) pressing and drying the centrifuged slag slurry by a filter press, conveying the slag slurry to an industrial refuse dump for treatment, and dissolving magnesium and iron in rock salt in brine and taking the rock salt out of a brine well. Impurity Ca in brine after underground purification treatment2+1.5g/l、Mg2+0.4g/l、SO4 2-2.7g/l、Fe2+17mg/l。
In addition, in order to ensure the quality of finished salt and the long-period stable operation of a production system, the purposes of removing iron, manganese and inhibiting magnesium ion enrichment are realized by adding sodium hydroxide into brine after underground treatment. Along with the continuous proceeding of the evaporation process, the gypsum forms enrichment in the salt making material liquid, and in order to ensure the stable operation of the salt making evaporation system and the quality of salt products, the gypsum is controlled by the way of discharging the salt making mother liquid. The external discharge capacity of the salt-making mother liquor is about 70m3The main components of the calcium sulfate, calcium chloride and magnesium chloride. The discharged salt-making mother liquor is centrifuged and filter-pressed to firstly separate solid-phase gypsum, and the gypsum mud is stacked in a factory and then transported to an industrial garbage factory for centralized treatment. The calcium chloride in the liquid phase is balanced by supplementing a certain amount of mirabilite, the magnesium chloride is controlled by adding sodium hydroxide into the centrifugal mother liquor, the centrifugal clear liquid is returned to the salt-making evaporation system, and the clear liquid is subjected to pressure filtration and injection into the well.
However, for salt production enterprises, the existence of magnesium ions not only affects the product quality, but also increases the concentration of the evaporated feed liquid due to the enrichment of magnesium ions in the evaporated feed liquid, so that the boiling point of the evaporated feed liquid is increased, and the energy consumption is increased; meanwhile, the hydrolysis can occur under certain conditions to cause equipment corrosion. The brine purification mode has the following problems in the actual operation process:
(1) the gypsum generated by the system is difficult to transport out for a while due to high moisture, and is accumulated in a factory, so that the environmental protection pressure is huge, and in addition, the dry basis treatment cost is expensive;
(2) the concentration of magnesium chloride in the system causes the boiling point of the feed liquid to be increased, and the magnesium chloride can be hydrolyzed under certain temperature and pressure to cause corrosion, thus endangering evaporation equipment;
(3) the salt production mother liquor centrifugation and filter pressing device has high failure rate and high maintenance cost;
(4) the expense for removing magnesium by using sodium hydroxide in the mother liquor is high, the precipitation is slow, the centrifugal clear liquid contains a large amount of gypsum and magnesium hydroxide solid phase substances, and the gypsum and magnesium hydroxide solid phase substances are returned to a salt making system to form vicious circle.
The 'green and clean' is the object pursued by the salt industry, and along with increasingly strict environmental protection requirements, the control measures mainly including circular economy, energy conservation and emission reduction are adopted, so that the resource consumption is reduced, the environmental pollution is reduced, the environmental protection is enhanced, the coordinated and sustainable development of economy, society and environment is realized, and the method is a necessary choice for the industry of the new century. In the process of producing salt by using rock salt as a raw material, the calcium magnesium mud and the gypsum mud which are byproducts in the production process are solved, and the problem of great environmental protection of all salt manufacturing enterprises including elm areas is solved.
Disclosure of Invention
The invention aims to provide a comprehensive treatment method of salt making mother liquor and salt mud, aiming at solving the defects of the prior art in the background technology.
The invention is realized in this way, a comprehensive treatment method of salt production mother liquor and salt mud, the method comprises the following steps:
(1) adding lime with the particle size of 30-100 meshes and the purity of more than 60% into an emulsifying tank containing salt making mother liquor for emulsifying for 20-40 min; wherein the concentration of magnesium ions in the salt making mother liquor is 0.38-0.42 g/L, and the mass ratio of the effective component calcium oxide in the lime to the magnesium ions in the salt making mother liquor is (105-110) multiplied by the purity: 1;
(2) pumping the emulsified substances into a mother liquor stirring reaction tank, fully reacting for 3-5 hours under a stirring state, and adjusting the pH value to be more than 11.4 until magnesium chloride is completely removed;
(3) pumping the reacted slurry into an original reaction barrel to be mixed with original halogen with the pH value of 6.8 so as to remove iron ions and manganese ions to obtain purified halogen, and controlling the pH value of the purified halogen to be 9.6-10 by supplementing alkali liquor; and (3) carrying out solid-liquid separation on the purified halogen in a dalton precipitator, and using the obtained clear liquid for vacuum evaporation to prepare salt.
In the invention, the salt making mother liquor comprises calcium sulfate, calcium chloride, magnesium chloride ferric ions and manganese ion components.
Preferably, the method further comprises the following step after the step (3): (4) and (3) under the condition that the brine extraction pump normally injects water, pumping the sediment obtained after solid-liquid separation in the step (3) to an outlet of the brine extraction pump through a high-pressure sediment injection pump, and enabling the sediment and the injected water to enter the brine well.
In the invention, the sediment obtained after solid-liquid separation is salt mud, the main components of the sediment comprise calcium magnesium mud and gypsum mud, and the problem of waste solid accumulation is solved by injecting the salt mud into a well.
Preferably, in the step (1), the concentration of magnesium ions in the salt making mother liquor is 0.4g/L, and the mass ratio of the effective component calcium oxide in the lime to the magnesium ions in the salt making mother liquor is 107 × purity: 1.
preferably, in the step (1), the external discharge capacity of the salt making mother liquor is 68-72 m3/h。
Aiming at the defects in the prior art, the invention starts from the following aspects in the process of research and development according to defect analysis to eliminate the defects:
(1) the external discharge capacity of the salt making mother liquor needs to be continuous and stable, and the gypsum content of an evaporation tank needs to be stable;
(2) a magnesium removing agent is searched for again to replace liquid caustic soda, so that magnesium hydroxide can be precipitated, brine entering a tank is clear, and the cost for removing magnesium is reduced;
(3) thoroughly solves the problem of the direction of the gypsum and eliminates a series of environmental protection problems caused by the solid waste of the gypsum generated in the production process;
(4) the content of magnesium chloride in the feed liquid in the evaporation tank is effectively controlled through magnesium removal, and the hidden danger that equipment is corroded due to hydrolysis of the magnesium chloride is eliminated;
(5) the mother liquor centrifugation and filter pressing system is replaced by adopting a calcium-magnesium mud well injection mode, high operation cost and maintenance cost are eliminated, and a series of vicious cycles caused by incomplete solid-liquid separation are synchronously eliminated.
Furthermore, the present invention is directed to the characteristics of the raw halogen component, CaSO for the following reasons4、CaCl2、MgCl2The method is not processed in the original brine, but processed in the mother liquor discharged after salt evaporation and concentration:
the first reason is as follows: removal of CaSO from the raw halogen according to the characteristics of the components of the raw halogen4、CaCl2、MgCl2The treatment cost is too high and is not economical;
the second reason is that: the impurity content in the original halogen is in an unsaturated state, so that the scaling of a halogen conveying pipeline can not be caused;
the third reason is that: the salt-making evaporation system adopts a gypsum crystal seed antiscaling process, and CaSO in the raw brine4、CaCl2、MgCl2In the salt-making evaporation tank, enrichment is formed along with evaporation, and a solid phase CaSO is formed4Precipitating, discharging in gypsum material liquid form by a gypsum discharge system of the evaporating pot, and discharging solid CaSO in the discharged gypsum material liquid4The concentration of the CaCl in the liquid phase is 20-30 g/l2、MgCl2The content of (A) is below 10 g/l; the discharged gypsum liquid is separated from solid salt by a salt precipitator for preparing salt with 11 m layers, and then is conveyed to a filter pressing system through a pipeline, centrifugal clear liquid is removed of magnesium by adding liquid alkali, a small amount of mirabilite is supplemented, calcium is removed, and then the centrifugal clear liquid is removed from a reaction barrel, and under the condition that the pH value of purified brine is controlled to be 9.5-9.7, the purposes of removing iron and manganese are synchronously achieved; and (4) performing filter pressing on the centrifuged slurry to realize solid-liquid separation, wherein the liquid phase is sent to a well-injecting bucket, and the solid phase is sent to a gypsum storage yard.
Compared with the defects and shortcomings of the prior art, the invention has the following beneficial effects:
(1) through a large number of laboratory tests, the magnesium removal is successfully realized in the salt making mother liquor by using lime finally, the magnesium removal effect is obvious, the magnesium removal rate is 100 percent, the cost is low, and the solid-liquid separation is thorough; the method has the advantages that the magnesium is removed while the recovery and the utilization of a large amount of mother liquor (old brine) and heat are realized, the magnesium removal cost is greatly reduced, the turbidity of purified brine is obviously reduced, the magnesium removal effect of the mother liquor is obvious, the guarantee is provided for the stable operation of a subsequent evaporation system and the product quality, the national requirements of energy conservation, emission reduction and environmental protection are met, the benefit is higher, and the market prospect is better;
(2) the invention not only saves a gypsum filter pressing system, but also eliminates a series of environmental protection pressure caused by solid waste generated on the ground.
(3) The invention has simple process, obvious effect and stable and reliable operation, and is an ideal process technology for solving the problem of gypsum solid waste removal.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Example 1 Experimental validation
1. Working principle and preparation work before experiment
（1）MgCl2Method for treating Fe and Mn
MgCl is removed by lime (main component CaO) method2The chemical reaction formula is as follows:
CaO + H2O ＝ Ca（OH)2digestion exothermic reaction
MgCl2+ Ca（OH)2＝ Mg（OH)2↓ + CaCl2(Xinsheng)
The literature search shows that the pH of the solution must be greater than or equal to 11.3 for the purpose of magnesium removal. The actual consumption of the raw halogen in the production is 530m3About/h, the amount of the produced salt production mother liquor is 70m3The salt making mother liquor amount is about 13 percent of the original halogen amount. Detection of MgCl in original halogen before experiment2The content is about 1.6g/l, and the content of evaporated rich product is increased to be MgCl in the original halogen after the salt is put into an evaporation tank for salt production2Ten times the content.
(2) Method for treating trace Fe and Mn
When the pH value of the original halogen is more than or equal to 9.2 and more than or equal to 8.7, most of Fe and Mn can be removed, and the quality of the salt can completely meet the requirements of users. The implementation method comprises the following steps: the method of mixing the mother liquor (pH is about 11.3) after adding lime to remove magnesium with the original halogen can realize the removal of Fe and Mn, and when the pH of the mixed purified halogen is less than 8.7, the purified halogen is adjusted by a small amount of supplementary liquid caustic soda (sodium hydroxide).
（3）CaCl2Is processed by
Is prepared from mirabilite (Na)2SO4) Method for removing CaCl2The chemical reaction formula is as follows:
CaCl2+Na2SO4= 2NaCl+CaSO4↓
the method has been applied in middle salt elmin company for 5 years, and has simple and reliable process, and can balance calcium ion introduced by lime.
(4) Taking mother liquor components by a salt preparation and precipitation device:
Ca2+：3.058g/l Mg2+：2.238g/l SO4 2-：3.089g/l
CaCl2：4.899 g/l MgCl2：8.767 g/l CaSO4：4.378 g/l
NaCl：299.76 g/l pH：8.2
2. experimental procedure
(1) Preparing a sample:
firstly, lime is ground into powder for preparing a sample for later use;
collecting the gypsum mother liquor, filtering and reserving clear liquid for later use;
preparing 30% liquid caustic soda by using analytically pure sodium hydroxide for later use;
fourthly, taking a proper amount of analytically pure sodium sulfate for later use;
fifthly, taking sufficient gypsum mother liquor in the salt making and precipitating device for standby.
(2) The comparison test of magnesium ions in the lime gypsum removal mother liquor and magnesium ions in the sodium hydroxide gypsum removal mother liquor, and the comparison test of magnesium ions in the lime gypsum removal mother liquor filtrate and magnesium ions in the sodium hydroxide gypsum removal mother liquor filtrate:
firstly, calculating the lime amount needed by theoretical magnesium removal, when 100 percent of lime is digested into calcium hydroxide solution, 2.238 g/l of magnesium ions in 1 liter of mother liquor are removed, 5.22g of calcium oxide is needed, but the calcium hydroxide is also a slightly soluble substance, and the conversion cannot realize 100 percent, so the aim of removing magnesium can be realized only by controlling the pH, and the pH is adjusted to be more than 11.3 according to the experience of removing magnesium;
taking four beakers, wherein the numbers of the beakers are 1#, 2#, 3#, 4#, 1# and 2#, respectively measuring 1 liter of gypsum mother liquor and 1 liter of mother liquor by using a measuring cylinder, and filtering clear liquor; measuring 1L of gypsum mother liquor and 1L of mother liquor filtered clear liquid respectively for No. 3 and No. 4;
③ adding weighed calcium oxide slowly into a No. 1 beaker, observing a pH meter while stirring, controlling the reaction speed to obtain magnesium hydroxide with larger crystal grains until the pH is adjusted to 11.4, and consuming 27.08g of calcium oxide (undigested, added in the form of solid);
adding lime slowly into the No. 2 filtered clear liquid (slaking), observing a pH meter while stirring until the pH is adjusted to 11.4, and consuming 21.07g of calcium oxide;
fifthly, adding 30 percent sodium hydroxide solution into the 3# gypsum mother liquor and the 4# gypsum mother liquor and the filtered clear liquor respectively, and adjusting the pH value to 11.4 for comparison;
sixthly, uniformly stirring the slurry after the reaction in the beakers of No. 1 to No. 4, pouring the slurry into a measuring cylinder of 1 liter, and observing the sedimentation and separation effects;
seventhly, timing and recording the clarified liquid level, wherein the trend of the clarified liquid level changing along with time is shown in the following table 1:
TABLE 1
Eighthly, taking 1 liter of gypsum mother liquor, slowly adding the lime after the grinding and digestion under the premise of continuous stirring, adjusting the pH value to 11.4, then calculating the amount of the newly generated calcium chloride for removing magnesium and the amount of the calcium chloride in the original mother liquor (10.35 +4.899= 15.249) according to the stoichiometric relation, wherein 19.5g of sodium sulfate is needed for the two, weighing 19.5g of analytically pure mirabilite, adding the analytically pure mirabilite after dissolving, and observing the sedimentation and separation effects, wherein the table 2 is as follows:
TABLE 2
| Time of day | 5min | 10min | 15min | 20min | 1h |
| Clear liquid level | 21% | 38% | 50% | 59% | 76% |
Ninthly, simulating sediment injection experiment, taking sediment after 1# sedimentation, taking appropriate amount of well injection water, adding 1 liter of liquid level scale, observing sedimentation effect, wherein the liquid level of clear liquid is 84% after 1h, the effect is obvious, and the sedimentation rate is as shown in the following table 3:
TABLE 3
| Time of day | 5min | 10min | 15min | 20min | 1h |
| Clear liquid level | 36% | 60% | 71% | 76% | 84% |
⑩ taking 1.5L of gypsum mother liquor, adding slaked lime under stirringAdjusting the pH value to 11.4, adding 29.3g of dissolved sodium sulfate to remove calcium, and reacting to obtain gypsum mother liquor for later use; 870ml of mixed halogen and 130ml of gypsum mother liquor after reaction are respectively taken (according to the volume ratio of 70 m)3:500 m3Calculated) is poured into a beaker and stirred for 1min, then the mixture is poured into a 1-liter measuring cylinder for timing and observing the precipitation separation effect, meanwhile, 1 liter of gypsum liquid after magnesium and calcium removal is compared, and the precipitation separation rate is shown in the following table 4:
TABLE 4
| Time of day | 5min | 10min | 15min | 20min | 1h |
| Clarifying the liquid surface after mixing with the original halogen | 95% | 96% | 96% | 97% | 97.1% |
| Clear liquid level of gypsum mother liquor | 20% | 32% | 40% | 49% | 72% |
The sedimentation rate of the gypsum mother liquor after the calcium of the mirabilite is removed by lime and the gypsum mother liquor is mixed with the raw brine is very rapid, the volume of the clear liquid can reach 95 percent after 5min, the clear liquid can reach 97.1 percent after 1h, the compactness of the precipitate is good, and the clear supernatant can obtain good effect.
3. Data analysis
(1) Data (g/l) for the supernatant after 1# sedimentation, as shown in Table 5 below:
TABLE 5
| Ca2+ | Mg2+ | SO4 2- | CaCl2 | MgCl2 | CaSO4 | NaCl | pH |
| 6.07 | Not detected out | 0.576 | 16.14 | Not detected out | 0.816 | 300.86 | 11.76 |
(2) The clear liquid analysis data (g/l) after the lime magnesium removal and the mirabilite calcium removal sedimentation are shown in the following table 6:
TABLE 6
| Ca2+ | Mg2+ | SO4 2- | CaCl2 | MgCl2 | CaSO4 | NaCl | pH |
| 1.966 | Not detected out | 3.141 | 1.82 | Not detected out | 4.45 | 285.35 | 12 |
(3) The analytical data (g/l) of the supernatant after mixing the water for injection with the sediment are shown in Table 7 below:
TABLE 7
| Ca2+ | Mg2+ | SO4 2- | CaCl2 | MgCl2 | CaSO4 | NaCl | pH |
| 3.32 | Not detected out | 2.66 | 6.12 | Not detected out | 3.77 | 66.81 | 12.4 |
(4) The gypsum mother liquor after magnesium and calcium removal is mixed with total bittern and then is settled to separate clear liquid analysis data (g/l), as shown in the following table 8:
TABLE 8
| Ca2+ | Mg2+ | SO4 2- | CaCl2 | MgCl2 | CaSO4 | NaCl | pH |
| 2.01 | 0.212 | 3.47 | 1.56 | 0.83 | 4.92 | 301.04 | 9.3 |
4. Conclusion of the experiment
(1) Lime is selected as a magnesium removing agent, so that magnesium ions in gypsum mother liquor can be completely removed;
(2) the magnesium removal and sedimentation effect of lime is much more obvious than that of sodium hydroxide, sedimentation and separation are thorough, and the obtained clear liquid is more than 80 percent (volume ratio), thus being beneficial to recycling of mother liquor;
(3) when lime is used for removing magnesium, calcium carbonate and calcium hydroxide which do not participate in the reaction have good settling-assisting effect;
(4) after the lime and the mirabilite are used for magnesium removal and calcium removal, the obtained clear liquid has good quality, the data is shown in table 5, magnesium ions are completely removed, calcium ions are reduced to 1.966g/l from 3.058g/l compared with the mother liquid, the pH is =12, and the clear liquid can be completely recycled;
(5) the gypsum mother liquor obtained by removing magnesium from slaked lime and then removing calcium from sodium sulfate is mixed with the raw brine, so that the sedimentation of magnesium hydroxide and ferrous sulfide is facilitated, the sedimentation separation effect is very good, the compactness of the sediment is good, the solid phase content is only 3%, the sedimentation effect is better than the existing sedimentation effect of purified brine, the obtained brine is clear, the pH value is 10.3, and the aims of removing iron and manganese can be achieved on the premise of completely removing magnesium;
(6) after removing magnesium and calcium by using lime and mirabilite, the obtained calcium-magnesium gypsum mud is feasible for well injection;
(7) verifying whether the process of removing magnesium in the lime gypsum-removing mother liquor, the digestion reaction and the magnesium-removing reaction are feasible or not in a centralized way;
a plurality of salt-making mother liquors were taken on site, and the assay composition was as shown in table 9 below:
TABLE 9
| Ca2+ | Mg2+ | SO4 2- | CaCl2 | MgCl2 | CaSO4 | NaCl | pH |
| 3.52 | 3.14 | 2.51 | 6.85 | 12.30 | 3.56 | 299.47 | 8.1 |
By calculation, according to the fact that 50% of excess lime is directly added, 17g of 70% lime and 27g of mirabilite are weighed, then the lime is directly added into gypsum mother liquor, stirring is continuously carried out, after 1h, the pH is =9, the growth vigor is slow, and the pH is measured to be =11.8 the next day. Thus proving that: the direct removal of magnesium from undigested lime takes a long time and the reaction rate is slow. Therefore, a lime slaking procedure is first performed during the magnesium removal.
(8) Slaking lime with brine and mother liquor respectively to see the effect of magnesium removal, taking 1 liter of gypsum mother liquor (the content of magnesium chloride in the mother liquor is 8.767 g/l), weighing 17g of lime with the concentration of 70% (added according to the excess of 50%), slaking at the ratio of 1:3, adding the mother liquor, stirring for 30min, then adding pH =11.4, then adding 27g of mirabilite, settling for 1h, and then ensuring that the clear liquid amount is more than 70%, wherein the test data are shown in the following table 10:
watch 10
| Ca2+ | Mg2+ | SO4 2- | CaCl2 | MgCl2 | CaSO4 | NaCl | pH |
| 1.83 | Not detected out | 2.72 | 1.93 | 0 | 3.85 | 302.66 | 12.2 |
And (4) conclusion: lime can be digested with either mother liquor or raw brine, and the reaction time is comparable.
(9) To verify the volume change after lime slaking with 1:2 and 1:3 of the original halogen, 20g lime is taken and added with 40ml and 60ml of the original halogen for slaking, and the volume after slaking is increased by 8 percent and 12.5 percent, so the volume of the slaking pool is increased on a theoretical basis.
(10) The influence of the increase of the content of magnesium chloride on the sedimentation rate is verified
After 3 months and 26 days, lime is digested by a salt precipitator and the mother liquor (12.3 g/l of magnesium chloride) and the original halogen are added into 1 liter of the mother liquor (12.3 g/l of magnesium chloride) after the lime is digested according to a ratio of 1:3, the pH value is 11.7 after the stirring of the mother liquor for 24min, the pH value is 11.4 after the stirring of the mother liquor for 45min, 27g of mirabilite is respectively added and stirred for 5min, and the mixture is poured into a 1 liter measuring cylinder to observe the sedimentation effect, wherein the following table 11 shows:
TABLE 11
| Time of day | 5min | 10min | 15min | 20min | 1h |
| Clarifying the liquid surface after mixing with the original halogen | 0.8cm | 1.4cm | 2.0cm | 2.5cm | 6.5cm |
| Clear liquid level of gypsum mother liquor | 1.2cm | 2.5cm | 3.5cm | 4.0cm | 11.0cm |
According to the data, after the content of magnesium chloride in the mother liquor is increased to 12.3g/l, the excessive lime which is added in a 50% slaking way has poor clarifying effect and slow settling rate, so that the reaction and settling effect after the content of magnesium chloride is increased must be considered in the process of removing magnesium by using lime.
To further verify the effect of the amount of generated precipitate on the clarification effect, 700ml of the mother liquor after the reaction was taken and 300ml of the original halogen was added for dilution, and the effect was significant as shown in the following table 12:
TABLE 12
| Time of day | 5min | 10min | 15min | 20min | 1h |
| Clear liquid level | 2.5cm | 4.3cm | 6.5cm | 8.3cm | 25cm |
Then taking 700ml of mother liquor (12.3 g/l of magnesium chloride), adding 300ml of original halogen, adjusting the content of the magnesium chloride to 8.91g/l, adding excess 50% of slaked lime, adding mirabilite, stirring for 5min, and observing a clarifying effect, wherein the clarifying effect is obvious after 1 hour.
Experiments prove that: the concentration of magnesium chloride is low, which is beneficial to sedimentation effect.
(11) The lime granularity is increased (more than 0.6 mm), the lime is added according to the excess of 100%, the pH value is increased very slowly (is not easy to dissolve), and when the content of magnesium chloride is higher, the sedimentation effect is not changed obviously (5-10 min sedimentation effect).
(12) In 2016, 3 and 21 days, the feasibility of the determination of the effective calcium oxide in the lime by the sucrose method is verified by calcining the existing analytically pure calcium oxide, and after 1 hour of calcination, the content of the effective calcium oxide is about 90 percent, which proves that the determination of the effective calcium oxide in the lime by the sucrose method is feasible.
(13) The calcium oxide samples of 30 meshes, 60 meshes and 100 meshes are respectively prepared by a screening method, and are subjected to magnesium removal after being digested respectively, so that the consumed lime amount is equivalent, and the influence on the reaction is small when the granularity is 30-100 meshes, therefore, 30-100 meshes of lime can be selected as a magnesium removal agent in the production process.
Example 2 Industrial operation
1. Operation conditions of lime magnesium removal
According to the conclusion of a laboratory simulation experiment, the magnesium removing agent is lime with the particle size of 30-100 meshes and the purity of more than 70%; firstly pumping the salt-making mother liquor into a mother liquor stirring reaction barrel through a mother liquor transfer pump, obtaining the content of magnesium chloride in the mother liquor through analysis, adding excessive 50% of lime according to the stoichiometric relation, emulsifying the lime for 30 minutes through an emulsifying tank, then pumping the lime into the mother liquor stirring reaction barrel through the emulsifying pump, and starting stirring to fully react. And detecting that magnesium ions in the slurry of the stirring reaction barrel are not detected within 4 hours, wherein the pH value is more than 11.4, and then starting a treated mother liquor delivery pump to deliver the treated mother liquor into the original reaction barrel.
2. Brine recycling and turbidity change conditions
The treated mother liquor enters a reaction barrel for iron and manganese removal, the pH value does not reach more than 9.2, the purified brine pH can be increased only by supplementing liquid caustic soda, and the average addition of the liquid caustic soda is 0.9m after one month of trial operation3The slag discharge (sediment) of the dalle precipitator is not increased but reduced, the average slag discharge is 14m3And/h, the recovery utilization rate of the mother liquor is more than 80 percent. The solid gypsum (sediment) enters the underground along with the well injection water and settles at the bottom of the salt well dissolving cavity, thus eliminating the groundThe generation of solid waste of gypsum solves a series of environmental protection problems caused by the solid waste of gypsum.
After the invention is put into operation for 24 hours, the turbidity of purified brine is obviously reduced, and the purified brine is clear and transparent and can completely obtain the expected purpose. The discharged gypsum mother liquor of the salt making system is continuous, stable and controllable, the processes of magnesium removal, iron removal and calcium removal are stably operated, and the gypsum filter pressing system is completely shut down.
The invention eliminates the processes of salt making mother liquor centrifugation and filter pressing, simplifies the mother liquor treatment process and saves the operating cost; the invention changes the mother solution magnesium removing agent, keeps a certain amount of coarse-grained heavy insoluble substances in the magnesium removing process, plays a role in assisting precipitation, accelerates the precipitation of magnesium hydroxide and greatly reduces the magnesium removing cost; the treated mother liquor directly enters the crude brine settler, the salty mud plays a role in assisting sedimentation, the sedimentation rate is accelerated, the compactness of sediment is improved, the recycling of the salt making mother liquor is realized, and the turbidity of brine is reduced.
3. Analysis of economic benefits
(1) Raw material cost comparison
The raw material purchase charge of the invention is determined according to the consumption quota and the predicted market price, and the amount of mother liquor returned per hour is 70m3And about/h, the factory price of mirabilite is 240 yuan/ton, the factory price of lime is 570 yuan/ton, the factory price of liquid caustic soda is 3700 yuan/ton, and the effective production time of the production system is 330 days/year.
The usage amount of mirabilite is increased by 8m on the original basis3H, mean concentration 249kg/m3The price of 1.992 tons of mirabilite is 478.08 yuan, and the cost is increased by 478.08 yuan per hour; the lime consumption is 0.5 ton/hour (4 ton/class), and 285 yuan is increased per hour; the consumption of the stock solution alkali is 0.52 ton/hour (hundreds), the current consumption is 0.25 ton/hour (hundreds), the consumption is reduced by 0.27 ton/hour (hundreds), and the consumption per hour is reduced by 999 yuan; after the invention is implemented, because serial equipment such as a horizontal spiral centrifuge, a plate-and-frame filter press and the like are cancelled, the annual maintenance cost can be reduced by 70 ten thousand, the filter cloth replacement cost is about 15.6 ten thousand per year, and the accumulated equipment maintenance cost can be saved by 85.6 ten thousand yuan per year. The total cost of raw materials is reduced by average per hour (999-478.08-285) =235.92 yuan/hour, and the raw material cost is saved by 186.85 ten thousand yuan/year in a cumulative way.
(2) The labor cost and the welfare cost are basically equivalent to the original cost.
(3) Reduced gypsum processing costs
Discharging 70m of gypsum mother liquor in the process of producing salt per hour3H, the brine recovery rate is 80 percent, and the newly produced gypsum amount is 14m3The total amount of the gypsum after the original centrifugation and pressure filtration is at least 2 ten thousand tons per year, the cost for treating each ton of gypsum is 50 yuan, the treatment cost is at least 100 ten thousand yuan per year, and the environmental protection penalty and the adverse social effect caused by storage and transportation are eliminated.
(4) Electric charge accounting
Through actual measurement, the original power consumption is basically equivalent to the power consumption of the existing power consumption equipment.
The invention has simple process and convenient operation, comprehensively considers the cost and can save 372.45 ten thousand yuan per year.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.
Claims (4)
1. A comprehensive treatment method for salt production mother liquor and salt mud is characterized by comprising the following steps:
(1) adding lime with the particle size of 30-100 meshes and the purity of more than 60% into an emulsifying tank containing salt making mother liquor for emulsifying for 20-40 min; wherein the concentration of magnesium ions in the salt making mother liquor is 0.38-0.42 g/L, and the mass ratio of the effective component calcium oxide in the lime to the magnesium ions in the salt making mother liquor is (105-110) multiplied by the purity: 1;
(2) pumping the emulsified substances into a mother liquor stirring reaction tank, fully reacting for 3-5 hours under a stirring state, and adjusting the pH value to be more than 11.4 until magnesium chloride is completely removed;
(3) pumping the reacted slurry into an original reaction barrel to be mixed with original halogen with the pH value of 6.8 so as to remove iron ions and manganese ions to obtain purified halogen, and controlling the pH value of the purified halogen to be 9.6-10 by supplementing alkali liquor; and (3) carrying out solid-liquid separation on the purified halogen in a dalton precipitator, and using the obtained clear liquid for vacuum evaporation to prepare salt.
2. The integrated treatment method of salt mother liquor and salt mud as claimed in claim 1, characterized in that, after the step (3), the method further comprises the steps of:
(4) and (3) under the condition that the brine extraction pump normally injects water, pumping the sediment obtained after solid-liquid separation in the step (3) to an outlet of the brine extraction pump through a high-pressure sediment injection pump, and enabling the sediment and the injected water to enter the brine well.
3. The integrated treatment method of the salt manufacturing mother liquor and the salt slurry as claimed in claim 1, wherein in the step (1), the concentration of magnesium ions in the salt manufacturing mother liquor is 0.4g/L, and the mass ratio of the effective component calcium oxide in the lime to the magnesium ions in the salt manufacturing mother liquor is 107 x purity: 1.
4. the comprehensive treatment method of the salt manufacturing mother liquor and the salt slurry as claimed in claim 3, wherein in the step (1), the external displacement of the salt manufacturing mother liquor is 68-72 m3/h。
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| CN101289200A (en) * | 2007-04-16 | 2008-10-22 | 中国盐业总公司 | Technological process for purifying bittern |
| CN101792204A (en) * | 2010-02-11 | 2010-08-04 | 山东海天生物化工有限公司 | Method for refining underground brine by utilizing kalk waste sand discharged from soda ash production |
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| CN101289200A (en) * | 2007-04-16 | 2008-10-22 | 中国盐业总公司 | Technological process for purifying bittern |
| CN101792204A (en) * | 2010-02-11 | 2010-08-04 | 山东海天生物化工有限公司 | Method for refining underground brine by utilizing kalk waste sand discharged from soda ash production |
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| 芒硝型卤水杂质铁、锰元素的深度去除;蒋璨等;《盐科学与化工》;20170930;第46卷(第9期);第6-7页 * |
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