CN109369046A - A kind of technique that salt chemical engineering waste prepares high strength gypsum - Google Patents
A kind of technique that salt chemical engineering waste prepares high strength gypsum Download PDFInfo
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- CN109369046A CN109369046A CN201811376486.3A CN201811376486A CN109369046A CN 109369046 A CN109369046 A CN 109369046A CN 201811376486 A CN201811376486 A CN 201811376486A CN 109369046 A CN109369046 A CN 109369046A
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B11/00—Calcium sulfate cements
- C04B11/26—Calcium sulfate cements strating from chemical gypsum; starting from phosphogypsum or from waste, e.g. purification products of smoke
- C04B11/266—Chemical gypsum
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Abstract
The invention belongs to salt & chemical industry waste reutilization technology field, the technique that a kind of salt chemical engineering waste prepares high strength gypsum is disclosed, includes the following steps: step 1, calcium chloride solution and old halogen is mixed and stirred for, obtain the molten slurry of mixing of sodium chloride and dihydrate gypsum；Step 2, molten slurry desalination washing, the dihydrate gypsum slurry after being purified will be mixed；Step 3, dihydrate gypsum slurry is adjusted to acidity, and activity agent and crystal modifier is added, prepare alpha-semi water plaster stone using constant pressure hydro-thermal method；Step 4, it is separated by solid-liquid separation；Step 5, desalination depickling is washed；Step 6, dry, obtain high strength gypsum finished product.The beneficial effect comprise that the positive growth of effectively control intermediate dihydrate gypsum crystal, improves the intensity of high strength gypsum；Low energy consumption using water at atmospheric pressure thermal method, small investment, crystal form are easy to control；It effectively solves the problems, such as solid waste, meets Industrial Green sustainable development demand.
Description
Technical field
The present invention relates to salt & chemical industry waste reutilization technology fields, more particularly, to a kind of salt chemical engineering waste system
The technique of standby high strength gypsum.
Background technique
Chlor-alkali industry raw material salt either solid salt or liquid salt all there are problems that removing sulfate radical.It is currently used
Removing sulfate radical has traditional barium chloride method or newly-built embrane method, and wherein the barium sulfate of barium chloride method precipitating is as fixed-end forces,
Environment, the wasting of resources are polluted, while barium chloride is harmful to the human body；Embrane method is to be enriched with to obtain mirabilite hydrate to sulfate ion,
Excess capacity.
And utilizing the waste solution of calcium chloride of ammonia-soda process Sodium Carbonate Plant by-product is raw material, converts calcium sulphate dihydrate (i.e. for sulfate radical
Dihydrate gypsum), then further dehydration can prepare alpha semi-hydrated gypsum cementitious material, i.e. high strength gypsum.High strength gypsum is as one
Kind cementitious material has the characteristics that low intensity height, the heat of hydration, lightweight, volume stability are good, more in building, mold, light industry etc.
Aspect is widely applied.
The high strength gypsum size that prior art is prepared is less than normal, low strength, main cause are as follows: be used to prepare high-strength stone
The intermediate calcium sulphate dihydrate internal structural defects of cream are more, and crystal morphology cannot accurately control.
Summary of the invention
It is an object of the invention to overcome above-mentioned technical deficiency, propose that a kind of salt chemical engineering waste prepares high strength gypsum
Technique solves in the prior art the technical issues of high strength gypsum size is less than normal, low strength.
To reach above-mentioned technical purpose, technical solution of the present invention provides a kind of salt chemical engineering waste and prepares high strength gypsum
Technique, include the following steps:
Step 1, calcium chloride solution and old halogen are mixed and stirred for, obtain the molten slurry of mixing of sodium chloride and dihydrate gypsum；
Step 2, molten slurry desalination washing, the dihydrate gypsum slurry after being purified will be mixed；
Step 3, dihydrate gypsum slurry is adjusted to acidity, and activity agent and crystal modifier is added, utilize constant pressure hydro-thermal legal system
Standby alpha-semi water plaster stone；
Step 4, it is separated by solid-liquid separation, solution circulation is used for step 3, and solid enters step 5；
Step 5, desalination depickling is washed；
Step 6, dry, obtain high strength gypsum finished product.
Compared with prior art, the beneficial effect comprise that effectively controlling the positive of intermediate dihydrate gypsum crystal
Growth, improves the intensity of high strength gypsum；Low energy consumption using water at atmospheric pressure thermal method, small investment, crystal form are easy to control；It effectively solves solid
Useless problem, meets Industrial Green sustainable development demand.
Detailed description of the invention
Fig. 1 is process flow chart of the invention；
Fig. 2 is the dehydration rate of dihydrate gypsum crystal under the influence of activating agent；
Fig. 3 is the solubility of dihydrate gypsum in an acidic solution.
Specific embodiment
In order to make the objectives, technical solutions, and advantages of the present invention clearer, with reference to the accompanying drawings and embodiments,
The present invention will be described in further detail.It should be appreciated that specific embodiment described herein is only used to explain this hair
It is bright, it is not intended to limit the present invention.
A kind of salt chemical engineering waste provided by the invention prepares the technique of high strength gypsum, includes the following steps:
Step 1, calcium chloride solution and old halogen are mixed and stirred for, obtain the molten slurry of mixing of sodium chloride and dihydrate gypsum.Institute
The calcium chloride concentration for stating calcium chloride solution is 30~45%；The sodium sulfate concentration of the old halogen is 20~35%；The calcium chloride
The temperature of solution and old halogen is 45~65 DEG C；The mixing is quickly to mix, and mixed process is completed in 5~15min；It is described
The rate of stirring is 60~90rpm, and the time is 1.5~3h.
Step 2, molten slurry desalination washing, the dihydrate gypsum slurry after being purified will be mixed.
Step 3, dihydrate gypsum slurry is adjusted to acidity, and activity agent and crystal modifier is added, utilize constant pressure hydro-thermal legal system
Standby alpha-semi water plaster stone.The dihydrate gypsum partial size of the dihydrate gypsum slurry is 100~300 μm；The temperature of the water at atmospheric pressure thermal method
It is 95~99 DEG C；The pH value of the acidity is 1~3；The activity agent is the calcium chloride solution that concentration is 23~27%；It is described
A kind of polycarboxylate, a kind of complex anion, close to neutrality can be selected in crystal modifier.
Step 4, it is separated by solid-liquid separation, solution circulation is used for step 3, and solid enters step 5.
Step 5, desalination depickling is washed.
Step 6, dry, obtain high strength gypsum finished product.
This technique, which can be divided into, prepares intermediate dihydrate gypsum, and prepares alpha-semi water plaster stone two parts, i.e., first by sodium sulphate and
Calcium chloride reaction, obtains dihydrate gypsum, then using dihydrate gypsum as raw material, prepares alpha semi-hydrated gypsum by constant pressure hydro-thermal reaction
Cementitious material.
Dihydrate gypsum acts as the role of intermediate in this system, in constant pressure hydro-thermal reaction process, dihydrate gypsum
Crystal habit is one of the deciding factor of alpha semi-hydrated gypsum performance quality.Influence calcium sulphate dihydrate crystal morphology it is main because
Element includes: reaction temperature, solution concentration, stirring condition, reaction time control, medium crystallization agent etc..
Temperature is that crystal morphology an important factor for influencing dihydrate gypsum crystal pattern, under normal temperature condition occupies for fine acicular
More, length is between 5~25 microns, and partial size is at 3 microns or less；It is warming up to 40 DEG C of crystal to significantly increase, length reaches 30
Micron or more (except some tiny broken grains), draw ratio variation it is little；And temperature, when reaching 50 DEG C and 65 DEG C, crystal particle diameter has
Larger promotion, the suitable temperature of preliminary judgement technique are 50~65 DEG C.
In order to accurately control reaction condition, further contrived experiment group is equidistantly set in 45~70 DEG C of sections respectively
Temperature is set, with the pattern for the dihydrate gypsum crystal that 700 times of electron microscope observations obtain.4h is reacted under conditions of 45 DEG C to obtain
The crystal morphology arrived are as follows: crystal homogeneity is preferable, and size is less than normal, and the reaction time is too long；3.5h is reacted under the conditions of 50 DEG C to obtain
Crystal morphology are as follows: crystal homogeneity is good, crystal length be 20~120 μm of sections；The crystalline substance that 2h is obtained is reacted under the conditions of 55 DEG C
Bodily form looks are as follows: the length of crystal is between 15~100 μm, and major diameter is bigger, and crystal is distributed in the section；In 60 DEG C of conditions
Lower 2h obtains crystal morphology, and crystal length is 20~100 μm, draw ratio 8~15；The crystalline substance that 2h is obtained is reacted under the conditions of 65 DEG C
Bodily form looks are as follows: 30~120 μm of length, draw ratio 5~10；The crystal morphology obtained under the conditions of 70 DEG C are as follows: crystal length 15~
120, draw ratio 5~15, uniformity is poor.Therefore, in terms of reaction temperature, high temperature is conducive to the growth of crystal on the whole, and then obtains
To larger-size crystal, but the homoepitaxial that excessive temperature is unfavorable for crystal is easy to produce more defect, and increases production
Cost and plant maintenance difficulty, therefore recommend in later period industrial production controlled at 45~65 DEG C.
The concentration of reaction solution has a certain impact to dihydrate gypsum crystal pattern, when the concentration of reactant is excessive, instead
The dynamic conditions answered promotes rapid reaction to carry out, and reaction carries out in a short time, in crystal nucleation and growth course, at
Epipole is more, and growth course is relatively on the weak side, and obtained crystal grain is less than normal, and crystal development is imperfect, and defect is in the majority；It is molten when reacting
When liquid concentration is too low, reaction is carried out at a slow speed, can improve that above-mentioned crystal is smaller, the problem more than defect, but works as the concentration of reaction solution
When too low, the consumption of water is increased in actual production, while extending the reaction time, reduces production efficiency.
On the basis of the test result of early period, different reactant concentrations is selected respectively, as shown in table 1, is observed
The pattern of dihydrate gypsum crystal.The temperature of reaction is set as 55 DEG C, the incorporation time of reactant is 3min.
Table 1
| Group | CaCl2Solution concentration (%) | Na2SO4Solution concentration (%) |
| A group | 20 | Saturation |
| B group | 40 | 5 |
| C group | 40 | Saturation |
| D group | 40 | 10 |
| E group | 40 | 20 |
| F group | 40 | 15 |
。
A group is 20%CaCl2Solution and saturation Na2SO4The crystal that solution is mixed to get, pattern are as follows: with long hair shape
Based on crystal, length is 50~60 μm or so, is horizontally differed greatly, range is 3-26 μm wider, and uniformity is poor.
B group is CaCl under other reaction condition unanimous circumstances2Solution is 40%, Na2SO4The concentration of solution is 5%, instead
Answer the dihydrate gypsum crystal that 2h is obtained, pattern are as follows: the uniformity of crystal entirety is preferable, and length is in 50~80 μ ms,
The draw ratio of crystal is 5~10:1, and the development of dihydrate gypsum whisker is more complete, but since the concentration of sodium sulphate is lower, and reaction needs
Longer time is wanted, the response parameter of the group is selected to reduce production efficiency in course of industrialization.
C group is CaCl under the conditions of other reaction conditions are consistent2Solution is 40%, Na2SO4The concentration of solution is
32%, react one hour obtained crystal, pattern are as follows: and crystal development is more sturdy, and the length of whisker is about 120 μm or so,
3~7:1 of draw ratio develops more complete.
D group is CaCl2Solution is 40%, Na2SO4The concentration of solution is 10%, reacts one hour obtained crystal, shape
Looks are as follows: crystal is more thin, and diameter differs greatly, uniformity is poor less than 10 μm compared with C group result.
E group is CaCl2Solution is 40%, Na2SO4The concentration of solution is 20%, reacts one hour obtained crystal, shape
Looks are as follows: the uniformity of crystal entirety is preferable, and the shape of parallelogram is presented, and is greatly improved relative to D group, but opposite
It is smaller in the diameter of C group crystal, only 10 μm or so.
F group is in CaCl2Solution is 40%, Na2SO4The concentration of solution is 15%, reacts one hour obtained crystal,
Pattern are as follows: crystal is comparatively fine.
Above-mentioned experiment mainly has adjusted Na2SO4The concentration of solution, from experimental result it can be seen that with Na2SO4Solution is dense
The increase of degree obtains crystalline size increase, works as Na2SO4It is 120 μm that (about 32%), which obtains crystal, when solution reaches saturation state,
3~7:1 of draw ratio develops more complete.The raising of solution concentration is conducive to the growth of crystal, but excessively high concentration can make
Reaction slurry is excessively thickened, and is unfavorable for the growth of industrial process operation and crystal.Therefore in terms of solution concentration, pushed away in industrial production
Recommending control calcium chloride concentration is 30~45%, and sodium sulfate concentration is 20~35%.
CaCl2Solution and Na2SO4Influence of the mixing velocity of solution to dihydrate gypsum crystal.(temperature under the same conditions
60 DEG C, CaCl2Solution concentration 44%, Na2SO4Solution saturation), divide and mixes twice quickly, at a slow speed, two water rapidly joined
Gypsum is having a size of 40~80 μm or so；The crystal that adding manner obtains at a slow speed, crystalline size is between 30~90 μm.Two kinds of comparison
The final crystal difference that situation obtains is little, all substantially conforms to require.But the crystal growth of the experimental group mixed at a slow speed larger one
A bit, especially on wide direction, but the experimental group crystal growth being added at a slow speed is slower, and 2h or more is needed to can be only achieved crystal
Size is basicly stable, and to can achieve crystal size basicly stable by the experimental group 1h rapidly joined.Therefore, in terms of incorporation time,
Above-mentioned experiment shows that influence of the incorporation time for crystal growth is not it is obvious that still affecting reaction speed to a certain extent
Rate, quickly mixing is advantageous for the raising of reaction rate, it is contemplated that the ease for operation in production efficiency and industrial practice is improved,
It is preferred that incorporation time is 5~15min.
Stirring rate has certain influence to the generation of dihydrate gypsum crystal.(temperature 60 C, CaCl under the same conditions2It is molten
Liquid concentration 44%, Na2SO4Solution saturation, incorporation time 4min), too fast stirring rate can make crystal grain uneven and whole
Body is less than normal, therefore from the angle for preparing bulky grain crystal, should use smaller stirring rate.It is contemplated that stirring rate
It is too small to be easy to cause reaction slurry dispersion uneven, or even the separation of solid and liquid of reaction slurry is caused, it is unfavorable for the uniform life of crystal
It is long.Therefore comprehensively consider, stirring rate should be controlled in 60~90rpm.
Reaction time influences the crystal morphology of dihydrate gypsum crystal.Reaction time crystal in 5min is fine particle,
Reaction condition is maintained, the long length of crystal in 20min, biggish size is at 10 μm or so, brilliant with the extension of time, in 1h
Body has grown to the size of 100 μm of grades, but uniformity is poor, continues insulated curing, when the time extending to 2h, crystalline size
In 100m or so, uniformity is preferable, and perfection of crystal can be increased by continuing extension soaking time, reduces lacking for plane of crystal
It falls into.Therefore it may determine that during preparing dihydrate gypsum crystal, two hours substantially can be realized the growth of crystal,
It does not influence that soaking time can be appropriately extended in the case where production.Therefore, in terms of the reaction time, in the case where not influencing production
Soaking time can be appropriately extended, the preferably control reaction time is 1.5~3h.
The characteristic (predominantly the impurity content of raw material is distributed with type and raw material particle size) of intermediate dihydrate gypsum whisker is right
Phase transformation has a major impact.It is analyzed by taking following four groups of experimental datas as an example.
A group: the length of dihydrate gypsum is 20~50 μm, and draw ratio is 1:5~10, and obtained alpha-semi water plaster stone partial size is 5
~10 μm, partial size is small, and the later period is separated by solid-liquid separation difficulty, and the thick water requirement of product mark is 58, and intensity is only 11.3MPa.
B group: the length of dihydrate gypsum is 50~150 μm, and draw ratio is 1:5~15, and obtained alpha-semi water plaster stone partial size exists
10~15 μm, increasing compared with A group, still whole partial size is still less than normal, and later period separation of solid and liquid is more difficult, and the thick water requirement of product mark is
52, intensity 17.5MPa.
C group: the length of dihydrate gypsum is 100~300 μm, and draw ratio is 1:5~15, obtained alpha-semi water plaster stone crystal
Pattern is preferable, and partial size is at 20~40 μm, and the later period, which is separated by solid-liquid separation, to be easy, and the thick water requirement of product mark is 36, intensity 37.2MPa.
D group: the length of dihydrate gypsum is 300~800 μm, and draw ratio is 1:5~8, although obtained alpha-semi water plaster stone has
A part of crystal morphology can be with, but react slowly, conversion ratio it is lower, there are more two water phases in product, send out later strength
It is unfavorable to open up, and measuring intensity is 24.7MPa.
Therefore, intermediate dihydrate gypsum partial size should control the high strength gypsum obtained under this condition at 100~300 μm
(alpha-semi water plaster stone) conversion ratio is higher, crystal habit is preferable and macro physical performance (marking thick water requirement and intensity) is more excellent.
Gypsum is each, and mutually dissolution-sedimentation equilibrium that may be present is as follows in electrolyte solution:
N=2,0.5 or 0 corresponding dihydrate gypsum (DH), semi-hydrated gypsum (HH) and anhydrous gypsum (AH), corresponding molten in formula
Spend product constant Ksp (dissolution-equilibrium constant) are as follows:
miFor the molar concentration for corresponding to ion in electrolyte solution, γiFor the activity coefficient of corresponding ion, αiTie substance
Activity, Ksp is only related with temperature, thus KSP at a certain temperature, DH, KSP, HH and KSP, AH are constants.
Transforming relationship that may be present between gypsum three-phase are as follows:
CaSO4·2H2O(s)(DH)=CaSO4·0.5H2O(s)(HH)+1.5H2O (6)
It is as follows that the thermodynamic equilibrium constant converted each phase can be released by formula (3) to (5):
By formula (7) and (8) it can be seen that the conversion temperature of each phase of gypsum depends on the activity of water in the solution, and water
Activity is determined by the component of electrolyte solution, that is to say, that the temperature of each inversion of phases changes with the concentration of electrolyte solution.
In pure water, the activity of water is about 1 in calcium sulfate saturated solution, is equal to KSP according to formula (8) KSP, DH, the temperature of HH is about
107.2 DEG C, in dense electrolyte solution, it is since the activity of water reduces that phase transition temperature, which is substantially reduced,.Therefore, this case is energy
The electrolyte that phase transformation temperature points are effectively reduced is known as activity agent.
It is prepared in high strength gypsum in constant pressure hydro-thermal, salting liquid can increase the solubility of alpha-semi water plaster stone and dihydrate gypsum
Difference can promote dihydrate gypsum crystal to alpha-semi water plaster stone crystalline transformation, accelerate rate of transformation.Sodium chloride solution and chlorination
Calcium solution, which has, promotes dihydrate gypsum crystal phase to act on to alpha-semi water plaster stone crystalline transformation, and sodium chloride solution is during the reaction
Na+ is adsorbed by crystal face, crystallizes to form Na with semi-hydrated gypsum2Ca5(SO4)6·3H2O mineral hinder the further transformation of crystal.
For various concentration calcium chloride solution, its difference between the effects is larger, and calcium chloride is a kind of raw material that can replace sodium chloride, as work
Spend agent.
The crystal morphology image obtained under the conditions of different activity agent solutions, other reaction conditions are as follows: medium crystallization agent 0.015%,
97 DEG C of temperature, solid concentration 50%.
A group:, can from image to react the crystal morphology image that 3h is obtained under conditions of mass fraction 23%
Out: for crystalline size in 8~15 μ ms, draw ratio is 2~5, is tested by the crystallization water, and moisture content is 6.54% close to half water
Crystal water of gypsum theoretical value, the crystal that can determine whether are CaSO4·0.5H2O phase, but crystalline size is smaller, dynamometry after molding
Intensity is bad, and 3d compression strength is only 7.8MPa.
B group: reacting the crystal that 3h is obtained for activity agent in mass fraction 24.5%, it can be seen that crystal from image
For size between 3-15 μm, crystal shows columnar form, close with αsemiwatergypsum hexagonal prism structure, but integral particle is too
It is small, the subsequent difficulty for being filtered, washed technique is increased, while normal consistency water requirement will increase, and then affect parget water
Change the mechanical strength of body, 3d compression strength is 26.7MPa.
C group: for the crystal morphology obtained under conditions of activity agent concentration 26%, it can be seen that crystal from image
Uniformity is poor, particle be 3~15 μm, it is still less than normal, but in experimentation it can be concluded that with activity agent concentration increase,
The trend that reaction time shortens, under the conditions of identical temperature in the system of 23% concentration, the time that fully reacting needs is about 5h
Left and right, when activity agent concentration increases to 26%, the time required for reacting completely foreshortens to 3.5h or so, obtained reaction
Product 3d compression strength is 25.6MPa, suitable with B group.
Activity agent concentration is continued growing, the test of D group is such as schemed, for the crystal shape that reaction 1h is obtained in 27% activity agent solution
Looks image, as can be seen that crystal is partial to elongate from image, draw ratio is 3~8 or so, and the particle of crystal is more equal
Even, it is 21.5MPa that the product standard water requirement under such form, which is 51%, 3d compression strength,.
The rate of water loss of A group to D group dihydrate gypsum crystal is as shown in Figure 2.
When continuing growing activity agent concentration to 28.5%, crystal homogeneity is preferable, and particle size is in 15~30 μ ms
Interior, uniformity is preferable；When activity agent concentration is 30%, crystalline size becomes smaller, and is between 5~15 μm, and reaction speed is very fast,
But the reaction product 3d compression strength obtained under two higher activity agent concentration conditions is 23.2MPa and 19.6MPa.
Known to theory analysis: in CaCl2In solution, SO4 2-Concentration is with CaCl2Solution concentration and hydro-thermal reaction thermostat temperature
The relationship of variation, with CaCl2Concentration increases to 30%, SO from 04 2-Concentration gradually decreases, this is because by common-ion effect
Influence, CaCl2Concentration is higher, and common-ion effect is more significant, SO4 2-Concentration is lower.Despite the presence of common-ion effect, make solution
In SO4 2-Concentration is smaller than in pure water, but Ca2+Activity still it is relatively high can enter lattice, at this time interface diffusion and it is right
The absorption of counter ions can be greatly promoted rate controlling step, in conjunction with the metamorphosis of αsemiwatergypsum, it is believed that α
It is surface integration control by growth unit step and fault location that semi-hydrated gypsum crystal, which is grown up,.In CaCl2In solution, with dampening
Thermal response thermostat temperature is increased to 100 DEG C from 85 DEG C, SO4 2-Changes in solubility it is little, thus degree of supersaturation increase degree has
Limit, causes influence of the temperature to its activity coefficient smaller.
From theory analysis according to above-mentioned test result: the concentration of activity agent could when must reach certain value
Dihydrate gypsum is effectively promoted to semi-crystal inversion of phases, concentration is bigger, and facilitation effect is more obvious, and the reaction time is shorter.But activity
Agent solution concentration should not be too large, and if F group is compared with D group, the reaction time shortens, and crystal development is imperfect in the short time, crystal shape
Looks are deteriorated, and tiny particle increased significantly in F group crystal, and average particle size particle size is smaller.Therefore recommend activity agent concentration 23~
27%, the selection of specific concentration can also be debugged according to actual production appointed condition.
When gypsum changes from dihydrate gypsum crystal phase to semi-hydrated gypsum, activity agent salting liquid can increase by two water phases and Ban Shui
The difference of phase increases reaction power for reaction.Energy demand required for reacting is provided by extraneous heating, i.e. reaction temperature
Phase transformation can be had an impact.See below the experiment of 6 groups of face.
The crystal morphology image that A is obtained under the conditions of being 94 DEG C, image are shown: crystal homogeneity is poor, and conversion ratio is relatively low
It (is tested by the crystallization water, half aqueous phase reforming rate is only that 47%), it is that shape is close that crystal indicates based on long hair shape, in figure
The crystal of hexagonal prism, measurement show dimensions as 22.16 μm, and 3d compression strength is 18.9MPa.
B is the crystal morphology obtained under the conditions of 96 DEG C, and indicating in image is conventional crystalline size, crystal grain
Between 11~20 μm, as can be seen that the crystal obtained under the conditions of 96 DEG C is more uniform from image, hexagon shape is presented,
But crystal is integrally less than normal, and it is 28.5MPa that mark thick water requirement, which be 46%, 3d compression strength, still needs to further adjust reaction condition.
The crystal morphology image that C is obtained under the conditions of being 97 DEG C, it can be seen that the crystal of this group has significantly from image
Hexagon shape, development is ideal, can be seen that crystalline size is crystal development between 20~25 μm from the mark in image
It is more complete, but have broken small crystal simultaneously, 3d compression strength is 32.6MPa.
3 hours of reaction obtain crystal morphology under the conditions of D is 98 DEG C, and image shows that crystal is more uniform, but broken small crystals
It equally exists, crystalline size is between 15~25 μm, and at round or long column shape, 3d compression strength is 30.7MPa.
E is the crystal morphology obtained under the conditions of 99 DEG C, may determine that from image crystal based on tiny crystal,
Biggish particle is 20 μm or so, but ratio is smaller, causes 3d compression strength not high, is 24.1MPa.
It is said from crystal nucleation-growth principle, the nucleation and growth process of crystal is only just able to achieve in temperature appropriate, temperature
Spend low, crystal is not easy to be nucleated, and the growth of crystal can not occur, and 85 DEG C and 90 DEG C in experiment belong to this reason；In temperature
(such as E, F group) crystal is easily nucleated under the conditions of excessively high 100 DEG C, and nucleation rate is very big, but is unfavorable for the growth of crystal, is occurred as soon as
Crystal exists in the form of fine grain or broken grain.
Nucleation-growing principle of binding crystal, the temperature of reaction is unsuitable too low, is not easy to realize crystal nucleation, also should not mistake
Height, causes to be not easy crystal growth to grow up.More suitable temperature is crystallized for alpha-semi water plaster stone for 95~99 DEG C in this reaction system
Condition.
The solution environmental of reaction system is another factor for influencing phase-change product, sees below 8 groups of experiments.
The crystal morphology that A is pH value when being 0.5 when reaction 1h, it can be seen that reaction does not carry out completely from image, but it is anti-
The crystal answered is based on fine particle, and most of in 1h all to be reacted, reaction speed is too fast, and crystal is too small.
B is that the obtained crystal morphology image of 2h is reacted in the reaction solution that pH value is 1, be may determine that from image and A
Group is compared, and crystal has increase tendency, reacts 2h substantially fully reacting, but crystal is still less than normal, and stock size is 8~12 μm,
The shape of particle is irregular, crystal development it is not perfect.
C is the crystal morphology image obtained when reacting 4h when pH value is 2, may determine that crystal homogeneity from image
Preferably, compared with A, B group, crystal continues the trend increased, and six sides are presented in 10~20 μ ms, partial crystals in crystal grain
Shape.
D is pH value reaction 5h is obtained when being 2.5 crystal morphology image, it can be seen that crystal is more mixed and disorderly from image,
Fine crystals coexist with short cylinder crystal, and uniformity is poor.
The crystal morphology that E, which is pH value, to be obtained when being 3, from image observed by several crystal can be seen that crystal is presented
Apparent six sides short cylinder is partially the hexagon of sheet, and biggish particle can reach 80 μm, and crystal development is complete, more manages
The crystal morphology thought, 3d compression strength reach 34.2MPa, for suitable strength in the test of this group.
The crystal morphology image that F, which is pH value, to be obtained when being 4, it is close with the draw ratio of raw material based on strip, pass through
The measurement of the crystallization water, the crystallization water of reaction product is close to dihydrate gypsum theoretical value, it can be determined that: in 6h, dihydrate gypsum is basic
Upper no dehydration.
G, H is respectively the obtained crystal morphology of reaction solution that pH value is 5,6, and two groups obtain when relatively low for H+ concentration
The crystal arrived, the two are crystal whisker-shaped, and major diameter is bigger, can be sentenced from two groups of reaction product crystal water content test results
It is disconnected, both based on two water phases, dehydration does not occur substantially and turns brilliant reaction.
Fig. 3 is variation of solubility of the dihydrate gypsum in acid with acid concentration, it can be seen that dihydrate gypsum is in salt
Solubility in acid reduces afterwards as the increase of concentration of hydrochloric acid first increases.PH value is that 1 or so, DH solubility is larger, degree of supersaturation
Larger, the motive force of reaction is larger, so the reduction reaction time with PH shortens.
The pH value of reaction solution influences the solubility property of solution, and when different PH, the concentration of H+ ion is different in solution,
Being in solution, oversaturated degree is different, and it is different to show different groups of rate of water loss.Degree of supersaturation is that the important of reaction pushes away
Power, when different saturation, the speed of crystal plane relative growth that can be different in α-HH crystal growing process is different, thus
The pattern of crystal is caused to be not quite similar.By comparing above-mentioned test result, it can be deduced that the pH value of solution has shadow to phase-change product
It rings, with acid increase, obtains crystal and have the tendency that shortening, thicker, rate of water loss is accelerated, the reaction time shortens.But it examines
Consider that acidity too strong in actual production process is more demanding to production equipment, increases the washing of product and the place of cleaning solution
Difficulty is managed, therefore the pH value of reaction solution is more suitable at 1~3.
The influence of double of water gypsum product of crystal modifier, as shown in table 2.
Table 2
| Serial number | D21 | D22 | D23 | D24 | D25 |
| Volume % | 0.05 | 0.10 | 0.15 | 0.30 | 0.5 |
| Transformation time min | 240 | 300 | 360 | 420 | > 500 |
| Dry compression strength MPa | 7.68 | 18.14 | 32.85 | 20.42 | - |
As can be seen from Table 2: as NS volume increases to 0.5% from 0.05%, the dihydrate gypsum phase transformation reaction time is obvious
Extend, when volume is 0.5%, under equal conditions hydro-thermal reaction 500min also turning brilliant sign to dihydrate gypsum does not occur.It produces
Also there is the trend of first increases and then decreases in the over dry compression strength of product, and the sample D23 compression strength in 0.15% volume of NS
There is maximum 32.85MPa, while the intensity of blank sample B19 of the intensity of D22 and D24 than not mixing NS under equal conditions is also bright
It is aobvious to improve.From the crystal morphology of corresponding product in terms of blank, NS volume changes practises influence to the brilliant of two water a semi-hydrated gypsums
It is obvious, sample D23 (a) crystal development of 0.10%NS is mixed than more complete and neat, and 15~35 μm of crystal diameter is (flat
20.7 μm of mean value), 70~120 μm of length (83.7 μm of average value), draw ratio be about 2~8 (average values 4.4)；It is mixed when increasing NS
It measures to 0.15% (sample D24), 10~45 μm of 10~25 μm of crystalline product diameter (17.6 μm of average value), length (average values
21.4 μm), the short cylinder crystal (b) of draw ratio 0.5~2.0 (average value 1.2), can from the SEM image (d) of the crystal
Crystal is six side's water chestnut columns out, and crystal face development is than more complete and neat, wherein being mingled with trace impurity particle；And NS volume is
Then slowly development is tripartite or hexagonal flake to 0.3% sample D24 crystal (c), and partial size is 5~40 μm, and intensity declines.
Thus, NS can be used as the efficient medium crystallization agent that dihydrate gypsum prepares high-strength a- semi-hydrated gypsum.
The above described specific embodiments of the present invention are not intended to limit the scope of the present invention..Any basis
Any other various changes and modifications that technical concept of the invention is made, should be included in the claims in the present invention
In protection scope.
Claims (9)
1. a kind of salt chemical engineering waste prepares the technique of high strength gypsum, include the following steps:
Step 1, calcium chloride solution and old halogen are mixed and stirred for, obtain the molten slurry of mixing of sodium chloride and dihydrate gypsum；
Step 2, molten slurry desalination washing, the dihydrate gypsum slurry after being purified will be mixed；
Step 3, dihydrate gypsum slurry is adjusted to acidity, and activity agent and crystal modifier is added, prepare α-using constant pressure hydro-thermal method
Semi-hydrated gypsum；
Step 4, it is separated by solid-liquid separation, solution circulation is used for step 3, and solid enters step 5；
Step 5, desalination depickling is washed；
Step 6, dry, obtain high strength gypsum finished product.
2. the technique that a kind of salt chemical engineering waste according to claim 1 prepares high strength gypsum, it is characterised in that: step 1
In, the calcium chloride concentration of the calcium chloride solution is 30~45%, and the sodium sulfate concentration of the old halogen is 20~35%.
3. the technique that a kind of salt chemical engineering waste according to claim 1 prepares high strength gypsum, it is characterised in that: step 1
Described in the temperature of calcium chloride solution and old halogen be 45~65 DEG C.
4. the technique that a kind of salt chemical engineering waste according to claim 1 prepares high strength gypsum, it is characterised in that: step 1
Described in mixing be quickly to mix, mixed process is completed in 5~15min.
5. the technique that a kind of salt chemical engineering waste according to claim 1 prepares high strength gypsum, it is characterised in that: step 1
Described in stirring rate be 60~90rpm, the time be 1.5~3h.
6. the technique that a kind of salt chemical engineering waste according to claim 1 prepares high strength gypsum, it is characterised in that: step 3
Described in the dihydrate gypsum partial size of dihydrate gypsum slurry be 100~300 μm.
7. the technique that a kind of salt chemical engineering waste according to claim 1 prepares high strength gypsum, it is characterised in that: step 3
Described in water at atmospheric pressure thermal method temperature be 95~99 DEG C.
8. the technique that a kind of salt chemical engineering waste according to claim 1 prepares high strength gypsum, it is characterised in that: step 3
Described in acid pH value be 1~3.
9. the technique that a kind of salt chemical engineering waste according to claim 1 prepares high strength gypsum, it is characterised in that: step 3
Described in activity agent be calcium chloride solution that concentration is 23~27%.
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| CN110589869A (en) * | 2019-09-09 | 2019-12-20 | 湖北工业大学 | Method for preparing alpha high-strength gypsum by using chlor-alkali byproduct salt gypsum and chemical waste salt in normal-pressure salt solution method |
| CN111170667A (en) * | 2020-01-10 | 2020-05-19 | 江苏一夫科技股份有限公司 | Dihydrate gypsum and preparation method thereof |
| CN112876111A (en) * | 2021-01-29 | 2021-06-01 | 江西晶昊盐化有限公司 | Alpha-type high-strength gypsum |
| CN113354319A (en) * | 2021-07-13 | 2021-09-07 | 山东大学 | Method for preparing alpha-type semi-hydrated gypsum by using desulfurized gypsum and high-salinity wastewater of power plant |
| CN113582215A (en) * | 2021-08-13 | 2021-11-02 | 苏州聚智同创环保科技有限公司 | Treatment process for preparing alpha high-strength gypsum from brine produced in well and mineral salt production |
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| CN111170667A (en) * | 2020-01-10 | 2020-05-19 | 江苏一夫科技股份有限公司 | Dihydrate gypsum and preparation method thereof |
| CN112876111A (en) * | 2021-01-29 | 2021-06-01 | 江西晶昊盐化有限公司 | Alpha-type high-strength gypsum |
| CN113354319A (en) * | 2021-07-13 | 2021-09-07 | 山东大学 | Method for preparing alpha-type semi-hydrated gypsum by using desulfurized gypsum and high-salinity wastewater of power plant |
| CN113354319B (en) * | 2021-07-13 | 2023-08-08 | 山东大学 | Method for preparing alpha-hemihydrate gypsum by using desulfurization gypsum in cooperation with high-salt wastewater of power plant |
| CN113582215A (en) * | 2021-08-13 | 2021-11-02 | 苏州聚智同创环保科技有限公司 | Treatment process for preparing alpha high-strength gypsum from brine produced in well and mineral salt production |
| CN113800868A (en) * | 2021-08-26 | 2021-12-17 | 淮南北新建材有限公司 | Method for optimizing performance of paper-surface gypsum board |
| CN113800868B (en) * | 2021-08-26 | 2023-08-15 | 淮南北新建材有限公司 | Method for optimizing paper gypsum board performance |
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