CN1830863A - Method and device of obtaining active lime by vacuum calcining limestone - Google Patents

Abstract

A process for preparing high-activity lime by vacuum calcining of lime stone includes such steps as crushing lime stone, loading in tank, heating in electric vacuum furnace at 750-900 deg.C under 100-1000 Pa, and quick cooling. Its activity is 380-450 ml.

Description

The method of obtaining active lime by vacuum calcining limestone and device

Technical field:

The present invention relates to the lime production field, specifically a kind of method of obtaining active lime by vacuum calcining limestone and device.

Background technology:

At present, the main method of production quickened lime has two kinds---shaft furnace method and kiln process.Shaft furnace and calcined by rotary kiln band pressure P are 110～130kPa, calcining belt temperature t _ForgeIn a single day be 1000～1200 ℃, the activity degree of lime that calcined limestone obtains is generally less than 360ml under so high pressure and temperature, and long slightly in the high-temperature zone residence time, just can make lime generation sintering and becomes calcined lime, loses activity.The method of quickened lime also once appearred obtaining with the salt calcined limestone in recent years, but the activity degree of the lime that this method is produced is generally still less than 360ml, generally also low than shaft furnace method and kiln process, and because NaCl has negative impact to lime and furnace lining etc., so do not obtain promoting.In addition, the patent No. is respectively the disclosed quickened lime preparation method of Chinese patent such as 91103712.8,94215597.1,96114235.9,99113350.1,00229065.0 and 02245980.4 also all at normal pressure with greater than carrying out its limestone calcination temperature t under the normal pressure _ForgeGenerally all greater than 1000 ℃, (for example the patent No. is 96114235.9 Chinese patent) that has even up to 1400 ℃, at high temperature lower calcination Wingdale like this, the decomposition rate of Wingdale may be very fast, but be difficult to guarantee that lime has higher activity degree, very easily make lime generation sintering and became calcined lime.Because above-mentioned these patents all fundamentally do not reduce the decomposition boiling temperature t of Wingdale _Boil, just may not reduce the calcining temperature t of Wingdale yet _ForgeEven claiming of having in the above-mentioned patent can be produced quickened lime by calcined limestone under 800～950 ℃ of lesser tempss, but that is the quickened lime that obtains under the long condition of, calcination time slow in decomposition of limestone speed, for example the patent No. is the method that the disclosed calcined limestone of 99113350.1 Chinese patent is produced quickened lime, its calcining temperature is 950～1050 ℃, and calcination time reaches 40～50 hours.

In sum, all unresolved activity of lime of prior art and decomposition of limestone contradiction between speed---calcining temperature height, decomposition of limestone speed is fast, but activity of lime is low, even burning and losing activity; And calcining temperature is low, though activity of lime is higher, decomposition of limestone speed is slow, and calcination time is long; And calcining temperature is low, also might cause to give birth to and burn, and can reduce the activity degree of lime equally.

Summary of the invention:

The object of the present invention is to provide a kind of method and device of obtaining active lime by vacuum calcining limestone, it can solve activity of lime and decomposition of limestone contradiction between speed effectively, can guarantee that lime has very high activity degree, can guarantee that again Wingdale has higher decomposition rate.

The method that realizes this obtaining active lime by vacuum calcining limestone of the object of the invention realizes as follows:

(1) will meet the fritter that the above limestone crushing of Wingdale industrial standards level Four or level Four becomes 20～40mm, the batch can of packing into lifts batch can in the vacuum chamber of vacuum electric furnace again, covers sealing cover;

(2) starting vacuum system vacuumizes;

(3) treat that vacuum indoor pressure P reduces to 100Pa when following, begin the temperature in the vacuum chamber to be raise that Wingdale begins calcining under vacuum condition to electric furnace power supply heating;

When (4) treating that the vacuum room temp reaches a certain temperature in 750～900 ℃ of temperature ranges, by furnace temperature observing and controlling cabinet control electric furnace constant temperature, P is not more than 1000Pa by vacuum system control vacuum indoor pressure;

When (5) treating that vacuum indoor pressure P is reduced to less than 100Pa by maximum value, stop vacuum electric furnace power supply heating;

When (6) treating that the vacuum room temp is reduced to below 700 ℃, close vacuum system, and switch valve makes vacuum chamber be communicated with atmosphere, recovering vacuum indoor pressure P is normal pressure;

(7) open sealing cover, hang out batch can, draw off lime wherein, make it quick cooling, can obtain the active lime that activity degree is 380～450ml.

The inventive method is based upon on the following theoretical basis.

(1) CaCO _{3 (s)}The thermodynamic argument of decomposition reaction.

K in the formula---CaCO _{3 (s)}The equilibrium constant of decomposition reaction;

T---CaCO _{3 (s)}Decomposition reaction temperature (calcining temperature), K.

CaCO _{3 (s)}Decomposes is as its decomposition pressure P _{CO2 (CaCO3)}When equaling system stagnation pressure (being the pressure in the limestone kiln) P, decomposition reaction is the most violent, is called to decompose boiling, and the equilibrium temperature of this moment is CaCO _{3 (s)}Decompose boiling temperature, be designated as t _Boil

T in the formula _Boil---CaCO _{3 (s)}Decompose boiling temperature, ℃;

P---system pressure (being the pressure in the limestone kiln), Pa;

P ^Θ---standard pressure, 10 ⁵Pa.

For making CaCO _{3 (s)}Significantly decompose, must make calcining temperature (being the temperature of calcining zone in the limestone kiln) t of Wingdale _Forge＞CaCO _{3 (s)}Decomposition boiling temperature t _BoilCalcining temperature t in the actual production _ForgeWith decomposition boiling temperature t _BoilThe pass be

t _Forge=t _Boil+ Δ t (iii)

T in the formula _Forge---limestone calcination temperature (being the temperature of calcining zone in the limestone kiln) ℃;

t _Boil---CaCO _{3 (s)}Decompose boiling temperature (calculating or measuring) ℃ by thermodynamic argument;

Δ t---superheating temperature (determining) ℃ by kinetic theory and knowhow.

T under the different pressures P-condition _BoilAnd t _ForgeAs shown in table 1.

The t of table 1 Wingdale under the different pressures condition _BoilAnd t _Forge

Annotate: the denominator of (1) table mid-score is a lower value, and molecule is a higher limit;

(2) superheating temperature Δ t is the empirical value in general limestone kiln in the table.

For obtaining the tiny active lime of crystal grain, must reduce the limestone calcination temperature t _ForgeAnd by formula (iii) as seen, reduce t _Forge, can only be by reducing t _BoilRealize.Aborning, certain decomposition rate is arranged, just must guarantee to have certain superheating temperature, so can not reduce Δ t for guaranteeing Wingdale.And by formula (ii) with table 1 as seen, have only the creation vacuum condition, reduce system stagnation pressure (being the stagnation pressure in the limestone kiln) P, could reduce t _BoilTherefore, the principle of obtaining active lime by vacuum calcining limestone can be expressed as:

(2) CaCO _{3 (s)}The kinetic theory of decomposition reaction.

CaCO _{3 (s)}Decomposition rate can be expressed as

$v=\frac{4\mathrm{\π}{r}^2{r}_0(1-P_{c{o}_2}/K)}{\frac{r_0}{k_{+}}+\frac{\mathrm{RT}}{K{D}_e}(r{r}_0-r^2)}---\left(\mathrm{iv}\right)$

V in the formula---CaCO _{3 (s)}Decomposition rate, mols ^-1

R---approximate globular CaCO _{3 (s)}Particle breakdown reaction interface radius, m;

r ₀---approximate globular CaCO _{3 (s)}The particle original radius, m;

P _CO2---CO in the system (limestone kiln) ₂Pressure component, 10 ⁵Pa;

K---CaCO _{3 (s)}The equilibrium constant of decomposition reaction;

k ₊---CaCO _{3 (s)}The positive reaction rate constant of decomposition reaction, molm ^-2S ^-1

D _e---CO ₂Effective diffusion coefficient in solid product (CaO) layer, m ²S ^-1

R---ideal gas constant, 0.082 * 10 ^-3～m ³Mol ^-1K ^-1

T---CaCO _{3 (s)}Decomposition reaction temperature (calcining temperature), K;

By formula (iv) as seen, under the certain condition of other conditions such as temperature T, utilize vacuum system to reduce the interior pressure P of vacuum chamber, promptly reduce P _CO2, when $P_{C{O}_2}=P\≈0$ The time, CaCO _{3 (s)}Decomposition rate v can reach maximum value.This explanation utilizes vacuum can accelerate the limestone calcination decomposition rate, shortens calcination time.

The device of realizing this obtaining active lime by vacuum calcining limestone of the object of the invention comprises:

A vacuum electric furnace;

The furnace temperature observing and controlling cabinet of monitoring and controlling this vacuum electric furnace working temperature;

The vacuum system of monitoring and controlling this vacuum electric furnace vacuum chamber pressure;

One places the batch can in this vacuum electric furnace vacuum chamber.

Produce the method and the device of active lime according to the present invention, compare with the production method of the described direct-heating type lime kilning of background technology, because Wingdale is a calcining and decomposing in the vacuum chamber of vacuum electric furnace, belong to the calcining of electric heating indirect heating type, therefore, solved activity of lime and decomposition of limestone contradiction between speed effectively, can guarantee that lime has very high activity degree, can guarantee that again Wingdale has higher decomposition rate; Solve lime effectively and be subjected to fuel or furnace gas pollution problems, sulphur pollution problem especially, the active lime that obtains is purer; And decomposition rate is fast in a vacuum because of Wingdale, and calcining temperature is low and calcination time is short, and calcination time is generally 2～3h, so heat waste is little, energy consumption is low.The lime that present method is produced has that product are tiny, porosity is high, volume density is little, specific surface area is big, activity degree high (be generally 380～450ml), hyperergic advantage, be more suitable in industrial circles such as metallurgy, process hides, papermaking, paint, coating, siccative, using.

Description of drawings:

Fig. 1 is the system architecture synoptic diagram of limestone calcination device of the present invention.

Fig. 2 is the batch can structural representation of limestone calcination device of the present invention.

Fig. 3 is the batch can section structure synoptic diagram of limestone calcination device of the present invention.

Embodiment:

Below in conjunction with drawings and Examples in detail the present invention is described in detail.

The device of the obtaining active lime by vacuum calcining limestone that present embodiment provides is made up of furnace temperature observing and controlling cabinet 1, batch can 2, vacuum electric furnace 3, vacuumometer 4, oil diffusion pump 5, vacuum valve 6, bypass 7, lobe pump 8, mechanical pump 9.This vacuum electric furnace 3 is 700～1400 ℃ no pot type vacuum resistance furnace for heating power 120kW, vacuum chamber useful volume φ 20mm * 400mm, working temperature; This furnace temperature observing and controlling cabinet 1 is electrically connected with vacuum electric furnace 3, is used to monitor and control the working temperature of this vacuum electric furnace 3; Monitor and control the vacuum system of these vacuum electric furnace 3 vacuum chamber pressures and be made up of oil diffusion pump 5, lobe pump 8, mechanical pump 9 and vacuumometer 4, vacuum valve 6, bypass 7, its pumping speed is 600Ls ^-1, final vacuum is 6.67 * 10 ^-2Pa; This batch can 2 places in the vacuum chamber of vacuum electric furnace 3, and batch can 2 inside are uniform-distribution with heat-conducting plate 11, and tank skin 10 and inner heat-conducting plate 11 thereof all are welded tank skin 10 outer setting hangers 12 by the heat-resistance stainless steel plate.

Its final vacuum of vacuum system among the present invention and pumping speed require with the output of active lime and activity degree and decide, and the volume size of batch can 2 should be decided with the ability of the output requirement of active lime and roasting assembly.

According to method steps of the present invention, present embodiment has carried out 5 calcining experiments, and what CaO content w (CaO)=51.7% was packed in each experiment into meets Wingdale industrial standards Wingdale 7kg, 850 ℃ of calcining temperatures, pressure P in the vacuum chamber fluctuates calcination time 2h in 100～1000Pa scope.The activity degree of the active lime that 5 experiments obtain is respectively 435mL, 441ml, 450ml, 429ml, 447ml.

Claims (5)

1, a kind of method of obtaining active lime by vacuum calcining limestone, its step is as follows:

(1) will meet the fritter that the above limestone crushing of Wingdale industrial standards level Four or level Four becomes 20～40mm, the batch can of packing into lifts batch can in the vacuum chamber of vacuum electric furnace again, covers sealing cover;

(2) starting vacuum system vacuumizes;

(3) treat that vacuum indoor pressure P reduces to 100Pa when following, begin the temperature in the vacuum chamber to be raise that Wingdale begins calcining under vacuum condition to electric furnace power supply heating;

When (4) treating that the vacuum room temp reaches a certain temperature in 750～900 ℃ of temperature ranges, by furnace temperature observing and controlling cabinet control electric furnace constant temperature, P is not more than 1000Pa by vacuum system control vacuum indoor pressure;

When (5) treating that vacuum indoor pressure P is reduced to less than 100Pa by maximum value, stop vacuum electric furnace power supply heating;

When (6) treating that the vacuum room temp is reduced to below 700 ℃, close vacuum system, and switch valve makes vacuum chamber be communicated with atmosphere, recovering vacuum indoor pressure P is normal pressure;

(7) open sealing cover, hang out batch can, draw off lime wherein, make it quick cooling, can obtain the active lime that activity degree is 380～450ml.

2, the method for a kind of obtaining active lime by vacuum calcining limestone as claimed in claim 1 and device comprise:

A vacuum electric furnace;

The furnace temperature observing and controlling cabinet of monitoring and controlling this vacuum electric furnace working temperature;

The vacuum system of monitoring and controlling this vacuum electric furnace vacuum chamber pressure;

One places the batch can in this vacuum electric furnace vacuum chamber.

3, the device of obtaining active lime by vacuum calcining limestone according to claim 2 is characterized in that this vacuum electric furnace is a vacuum resistance furnace, and working temperature is 700～1400 ℃.

4, the device of obtaining active lime by vacuum calcining limestone according to claim 2 is characterized in that this vacuum system is made up of oil diffusion pump, lobe pump, mechanical pump and vacuumometer, vacuum valve, bypass.

5, the device of obtaining active lime by vacuum calcining limestone according to claim 2 is characterized in that this batch can inside is uniform-distribution with heat-conducting plate, and batch can wall and inner heat-conducting plate thereof all are welded tank skin outer setting hanger by the heat-resistance stainless steel plate.

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