(19)
(11)EP 2 357 161 A1

(12)EUROPEAN PATENT APPLICATION
published in accordance with Art. 153(4) EPC

(43)Date of publication:
17.08.2011 Bulletin 2011/33

(21)Application number: 10829470.3

(22)Date of filing:  15.07.2010
(51)International Patent Classification (IPC): 
C04B 7/43(2006.01)
(86)International application number:
PCT/CN2010/075188
(87)International publication number:
WO 2011/057506 (19.05.2011 Gazette  2011/20)
(84)Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO SE SI SK SM TR

(30)Priority: 13.11.2009 CN 200910212645

(71)Applicant: Nanjing University Of Technology
Jiangsu 210009 (CN)

(72)Inventors:
  • SHEN, Xiaodong
    Nanjing Jiangsu 210009 (CN)
  • MA, Suhua
    Nanjing Jiangsu 210009 (CN)
  • DENG, Song
    Nanjing Jiangsu 210009 (CN)
  • CHEN, Lin
    Nanjing Jiangsu 210009 (CN)
  • LI, Xuerun
    Nanjing Jiangsu 210009 (CN)
  • ZHOU, Weiqiang
    Nanjing Jiangsu 210009 (CN)

(74)Representative: Strehlke, Ingo Kurt 
Patentanwälte Gesthuysen, von Rohr & Eggert Huyssenallee 100
45128 Essen
45128 Essen (DE)

  


(54)METHOD FOR SECONDARILY SYNTHESIZING CALCIUM SULPHOALUMINATE MINERAL IN PORTLAND CEMENT CLINKER


(57) A method for secondarily synthesizing calcium sulphoaluminate mineral in Portland cement clinker is provided. The method includes adding plaster into raw Portland cement and calcination, then heating twice to re-form calcium sulphoaluminate mineral that is decomposed at high temperature in the clinker. This method can increase the content of calcium sulphoaluminate mineral in the clinker, sufficiently exert the advantages of the calcium sulphoaluminate mineral in the clinker, enhance the early stage performance and long-term performance of the cement clinker, and increase the quantity of mixture in the cement.


Description

Field of the invention



[0001] The present invention relates to the preparation process of high gelling cement clinker, more specifically, it relates to secondary synthetic method of calcium sulphoaluminate mineral in Portland cement clinker.

Background of the invention



[0002] C4A3S mineral in Portland cement improves initial strength of cement, stimulates activity of composite material, and increases utilization rate of composite material in Portland cement, thus the formation of C4A3 S mineral in Portland cement clinker has significant importance.

[0003] The key issue in the preparation of Portland cement clinker containing C4A3S mineral is the problem of coexistence of C4A3S and Alite, wherein C4A3S mineral decomposes largely at 1350°C, while the formation of Alite in clinker starts at 1450°C, therefore, from thermodynamics point of view, C4A3S and Alite can not coexist in one same system. At present, Portland cement clinker containing C4A3S mineral is mainly prepared by doping fluorite and plaster to Portland cement raw meal which then is calcined at 1300~1400°C.

[0004] However, at present, most of cement is prepared via novel dry calcination in China, wherein the calcination temperature is around 1450°C and most of the formed C4A3S in cement clinker has been decomposed, therefore, only a small amount of C4A3S is left in cement clinker, leading to the deficiency of certain properties (such as initial strength) of Portland cement containing C4A3S mineral. Therefore, method for preparation of Portland cement clinker containing C4A3S has not been industrialized in China, and most of cement enterprises still produce traditional Portland cement clinker in pre-calcining kiln.

Summary of the invention



[0005] The object of the present invention is to improve the present calcining process of Portland cement clinker containing C4A3S mineral, and to provide a secondary synthetic method for preparation of calcium sulphoaluminate mineral in Portland cement clinker. As a result, the initial strength of said cement is improved and the requirements for production of Portland cement clinker containing C4A3S mineral in large pre-calcining kiln can be met.

[0006] To realize above mentioned object, the technical scheme of present invention is a secondary synthetic method for calcium sulphoaluminate mineral in Portland cement clinker, wherein it consists of the following steps:
  1. (1) Plaster is doped to Portland cement raw meal so that the content of SO3 in the raw meal is 0.5~6.0 wt%;
  2. (2) The prepared raw meal is calcined, the temperature is increased to 1400~1600°C at a rate of 1~25°C per minute and kept at said temperature, then it is naturally cooled;
  3. (3) The cooled clinker is heated to 800~1300°C at a rate of 1~25°C per minute, and kept at said temperature, then it is naturally cooled;
  4. (4) Said cooled clinker is ground to powder with the aid of ball mill;


[0007] Or it consists of the following steps:

(1A) plaster is added to Portland cement raw meal so that the content of SO3 in the raw meal is 0.5~6.0 wt%;

(2A) The prepared raw meal is calcined; the temperature is increased to 1400~1600°C at a rate of 1~25°C per minute and kept at said temperature, then it is transferred to a cooler, the temperature is reduced at a rate of 40~80°C per minute;

(3A) Keep the temperature when it is cooled to 800~1300°C, and then it is naturally cooled;

(4A) The said cooled cement clinker is ground to powder with the aid of ball mill.



[0008] Preferably, the holding time of step (2), (3), (2A) and (3A) is 5~120 min, respectively. Preferably, the specific surface area of ground powder of step (4) and (4A) is 340 360m2/kg.

[0009] Calcination of of the prepared raw meal in step (2) and (2A) is carried out under regular processing parameters.

Beneficial effects of the present invention:



[0010] The present invention relates to the thermal treatment of Portland cement clinker containing calcium sulphoaluminate mineral, through which calcium sulphoaluminate mineral which has been decomposed at high temperature is reformed, thus the content of calcium sulphoaluminate mineral in cement clinker is improved, the function of calcium sulphoaluminate mineral in Portland cement clinker is brought into full play, the short-term and long-term properties of cement clinker are improved and the doping amount of composite material in cement is increased.

Examples



[0011] The present invention is further illustrated with reference to the following examples, but the present invention is not limited to the following examples.

Example 1:



[0012] 0.30kg plaster (the SO3 content in plaster is 32.90 wt%) was doped to 5kg prepared Portland cement raw meal (the chemical compositions of cement raw meal are shown in Table 1), as a result, the SO3 content in raw meal is 1.86 wt%;
(1) The prepared cement raw meal was heated to 1480°C, calcined for 30min and cooled; subsequently, the temperature was increased to 1450°C at a rate of 5°C per minute and kept at said temperature for 30min, and then it was cooled;
(2) The cooled cement clinker was increased at a rate of 10°C per minute until it reached 1200°C, and kept at said temperature for 60min, and then it was cooled;
(3) The said cooled cement clinker was ground to powder with the aid of ball mill, the specific surface area of said powder is 350m2/kg; according to the test method of present inventor disclosed in CN200710302594.1, it was determined that the C4A3S content of cement clinker produced by Xuzhou Huaihai Cement Factory (without thermal treatment) was 0.5 wt%, and the C4A3S content of cement clinker of present Example (after thermal treatment) was 4.8 wt%;
(4) 4g plaster was added to 96g final obtained cement clinker, the said mixture was mixed uniformly, subsequently, 29mL water (ratio between water and cement w/c = 0.29) was added, the said mixture was stirred and molded to 20x20x20mm samples, and the 1d, 3d and 28d compressive strength was determined. Samples were first cured in a curing case for 24h, wherein the relative humidity was 90% and the temperature was 20±2°C, and then the demolded sample was cured in a water curing case at 20±1°C. The comparison of resulting strength is shown in Table 2.
Table 1 Chemical composition of raw meal
LossCaOSiO2Al2O3Fe2O3MgO
34.02 43.94 14.28 2.42 2.26 1.19
Table 2 Paste strength of Portland cement containing calcium sulphoaluminate mineral(MPa)
Examples1d3d28d
Xuzhou Huaihai Cement Factory      
(Portland cement clinker containing cal- 43.4 57.6 86.4
cium sulphoaluminate mineral)      
Example 1 55.7 66.9 94.2

Example 2:



[0013] 
(1) 0.28kg plaster (the SO3 content of plaster is 32.90 wt%) was added to 5kg prepared Portland cement raw meal (the chemical compositions of cement raw meal are shown in Table 1), as a result, the SO3 content of raw meal was 1.74 wt%;
(2) The prepared cement raw meal was heated to 1450°C, calcined for 60min and cooled; subsequently, the temperature was increased to 1400°C at a rate of 10°C per minute and kept at said temperature for 50min, and then it was cooled;
(3) The cooled cement clinker was increased at a rate of 15°C per minute until it reached 1250°C, and kept at said temperature for 90min, and then it was cooled;
(4) The said cooled cement clinker was ground to powder with the aid of ball mill, the specific surface area of said powder is 360m2/kg;
(5) 4g plaster was added to 96g final obtained cement clinker, the said mixture was mixed uniformly, subsequently, 29mL water (ratio between water and cement w/c = 0.29) was added, the said mixture was stirred and molded to 20x20x20mm samples, and the 1d, 3d and 28d compressive strength was determined. Samples were first cured in a curing case for 24h, wherein the relative humidity was 90% and the temperature was 20±2°C, and then the demolded sample was cured in a water curing case at 20±1°C. The comparison of resulting strength is shown in Table 3.
Table 3 Paste strength of Portland cement containing calcium sulphoaluminate mineral (MPa)
Examples1d3d28d
Xuzhou Huaihai Cement Factory      
(Portland cement clinker containing cal- 43.4 57.6 86.4
cium sulphoaluminate mineral)      
Example 2 54.5 67.0 93.8

Example 3:



[0014] 
(1) 0.3kg plaster (the SO3 content of plaster is 32.90 wt%) was added to 5kg Portland cement raw meal (the chemical compositions of cement raw meal are shown in Table 1), as a result, the SO3 content of raw meal was 1.86 wt%;
(2) The prepared cement raw meal was heated to 1450°C, calcined for 60min and cooled; subsequently, the temperature was increased to 1450°C at a rate of 5°C per minute and kept at said temperature for 30min, and then it was transferred to a cooler, the temperature was reduced at a rate of 55°C per min;
(3) The temperature was cooled to 1250°C, and kept at said temperature for 60min, and then it was cooled again;
(4) The said cooled cement clinker was ground to powder with the aid of ball mill, the specific surface area of said powder is 340m2/kg;
(5) 4g plaster was added to 96g final obtained cement clinker, the said mixture was mixed uniformly, subsequently, 29mL water (ratio between water and cement w/c = 0.29) was added, the said mixture was stirred and molded to 20x20x20mm samples, and the 1d, 3d and 28d compressive strength was determined. Samples were first cured in a curing case for 24h, wherein the relative humidity was 90% and the temperature was 20±2°C, and then the demolded sample was cured in a water curing case at 20±1°C. The comparison of resulting strength is shown in Table 4.
Table 4 Paste strength of Portland cement containing calcium sulphoaluminate mineral(MPa)
Examples1d3d28d
Xuzhou Huaihai Cement Factory      
(Portland cement clinker containing 43.4 57.6 86.4
calcium sulphoaluminate mineral)      
Example 3 47.2 64.2 91.5

Example 4:



[0015] 
(1) 0.28kg plaster (the SO3 content of plaster is 32.90 wt%) was added to 5kg Portland cement raw meal (the chemical compositions of cement raw meal are shown in Table 1), as a result, the SO3 content of raw meal was 1.74 wt%;
(2) The prepared cement raw meal was heated to 1450°C, calcined for 60min and cooled; subsequently, the temperature was increased to 1400°C at a rate of 10°C per minute and kept at said temperature for 50min, and then it was transferred to a cooler, the temperature was reduced at a rate of 50°C per min;
(3) The temperature was cooled to 1200°C and kept at said temperature for 30min, and then it was cooled;
(4) The said cooled cement clinker was ground to powder with the aid of ball mill, the specific surface area of said powder is 340~360m2/kg;
(5) 4g plaster was added to 96g final obtained cement clinker, the said mixture was mixed uniformly, subsequently, 29mL water (ratio between water and cement w/c = 0.29) was added, the said mixture was stirred and molded to 20x20x20mm samples, and the 1d, 3d and 28d compressive strength was determined. Samples were first cured in a curing case for 24h, wherein the relative humidity was 90% and the temperature was 20±2°C, and then the demolded sample was cured in a water curing case at 20±1°C. The comparison of resulting strength is shown in Table 5.
Table 5 Paste strength of Portland cement containing calcium sulphoaluminate mineral (MPa)
Examples1d3d28d
Xuzhou Huaihai Cement Factory      
(Portland cement clinker containing cal- 43.4 57.6 86.4
cium sulphoaluminate)      
Example 4 45.2 65.8 92.0



Claims

1. A secondary synthetic method for calcium sulphoaluminate mineral in Portland cement clinker, wherein it consists of the following steps:

(1) Plaster is added to Portland cement raw meal so that the SO3 content of raw meal is 0.5~6.0 wt%;

(2) The prepared raw meal is calcinated, the temperature is increased to 1400~1600°C at a rate of 1~25°C per minute and is kept at said temperature, and then it is naturally cooled;

(3) The cooled clinker is heated to 800~1300°C at a rate of 1~25°C per minute,and kept at said temperature, and then it is naturally cooled;

(4) Said cooled clinker is grpund to powder with the aid of ball mill;
Or it consists of the following steps:

(1A) Plaster is added to Portland cement raw meal so that the SO3 content of raw meal is 0.5~6.0 wt%;

(2A) Said prepared raw meal is calcinated, the temperature is increased to 1400~1600°C at a rate of 1~25°C per minute, and kept at said temperature, and then it is transferred to a cooler, the temperature is cooled at a rate of 40~80°C per minute;

(3A) The temperature is cooled to 800~1300°C and kept at said temperature, and then it is naturally cooled;

(4A) The said cooled cement clinker is ground to powder with the aid of ball mill.


 
2. The method according to Claim 1, wherein the holding time of step (2), (3), (2A) and (3A) is 5~120 minute, respectively.
 
3. The method according to Claim 1, wherein the specific surface area of powder ground by ball mill in step (4) and (4A) is 340 360m2/kg.
 





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Cited references

REFERENCES CITED IN THE DESCRIPTION



This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

Patent documents cited in the description