Method for curing cement bricks by dead steam

Abstract

The invention discloses a method for curing cement bricks by dead steam. The method comprises the following steps: 1) the dead steam passes through a gas-liquid filter screen; 2) compressing the exhaust gas passing through the gas-liquid filter screen, and spraying the compressed exhaust gas into high-temperature carbon-containing gas to obtain mixed gas; 3) compressing the mixed gas to obtain high-temperature carbon-containing steam; and (4) curing the cement green bricks by adopting high-temperature carbon-containing steam. By adjusting the curing atmosphere of the cement brick, high-added-value resource utilization of dead steam, tail gas containing carbon dioxide and other industrial waste gas or waste heat can be achieved, and the mechanical property, the yield resistance, the water resistance and the like of the obtained cement brick product can be effectively improved; and the related maintenance method is relatively simple, convenient to operate, environment-friendly and suitable for popularization and application.

Description

Technical Field

[0001] The invention belongs to the technical field of building materials, and in particular relates to a method for curing cement bricks with exhaust steam. Background Art

[0002] At present, the most commonly used curing methods for cement bricks are natural curing and autoclave curing. When natural curing is used, the energy consumption is low, but the curing time is long and a larger yard is required; when autoclave curing is used, the curing time is short and the strength of the prepared cement bricks is high, but a large amount of high-temperature and high-pressure steam is consumed, which results in high energy consumption. Therefore, under the premise of ensuring high turnover efficiency of cement bricks, reducing energy consumption during the curing process has become an important direction for the current development of the industry.

[0003] During the calcination of cement clinker, a large amount of high-temperature exhaust gas (350-450°C) is generated at the kiln tail. Currently, it is mainly used for waste heat power generation to reduce production energy consumption. However, after the high-temperature exhaust gas at the kiln tail heats the boiler, the exhaust gas is still as high as 90-150°C, and the thermal efficiency is low. In addition, the high-temperature and high-pressure steam prepared in the boiler forms exhaust steam after waste heat power generation, and the temperature and pressure are greatly reduced, but the low-temperature and low-pressure steam also has a high enthalpy (the enthalpy of 45°C steam in the literature is 2636kJ / kg). At present, there are two main methods for exhaust steam treatment: direct discharge or recycling after condensation, but both treatment methods fail to fully utilize the latent heat of exhaust steam. Summary of the invention

[0004] The main purpose of the present invention is to address the problems and shortcomings of the prior art and provide a method for curing cement bricks by utilizing waste heat from cement plants to generate electricity and exhaust steam. By adjusting the curing atmosphere of the cement bricks, high value-added resource utilization of industrial waste gases or waste heat such as exhaust steam and tail gas containing carbon dioxide can be achieved, and the mechanical properties, shrinkage resistance and water resistance of the resulting cement brick products can be effectively improved. The curing method involved is relatively simple and easy to operate, and is suitable for promotion and application.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] A method for curing cement bricks with exhaust steam comprises the following steps:

[0007] 1) Exhaust steam passes through the gas-liquid filter to remove large-sized condensed water droplets;

[0008] 2) compressing the exhausted gas after passing through the gas-liquid filter and spraying it into the high-temperature carbon-containing gas to obtain a mixed gas;

[0009] 3) compressing the mixed gas to 0.3-0.8 MPa to obtain high-temperature carbon-containing steam;

[0010] 4) Use high temperature carbon-containing steam to cure cement bricks.

[0011] In the above scheme, the temperature of the exhaust steam is 40-80°C, and the pressure is 0.05-0.1MPa.

[0012] In the above scheme, the pore size of the gas-liquid filter is 500-1000 mesh.

[0013] In the above scheme, the pressure of the exhausted steam after compression is 0.12-0.15 MPa.

[0014] In the above scheme, the temperature of the high-temperature carbon-containing gas is 300-400° C., the pressure is 0.05-0.1 MPa, and the carbon dioxide concentration is 15-30%.

[0015] Furthermore, the high-temperature carbon-containing gas can be selected from high-temperature carbon-containing waste gas, specifically cement kiln tail gas, metal smelter waste gas or thermal power plant waste gas.

[0016] In the above scheme, the speed at which the compressed exhaust steam is injected into the high-temperature carbon-containing gas is 15 to 30 m / s.

[0017] In the above scheme, the mass ratio of the high-temperature carbon-containing gas to the compressed exhaust gas in the mixed gas is 1:1.2 to 1.8.

[0018] In the above scheme, the temperature of the high-temperature carbon-containing steam is 150-180° C., the pressure is 0.3-0.8 MPa, the carbon dioxide concentration is 8-12 vol%, and the relative humidity is 75-90%.

[0019] In the above scheme, the step of curing the bricks with high-temperature carbon-containing steam includes: first, vacuuming with a vacuum degree of -0.04 to -0.08 MPa; then, introducing high-temperature carbon-containing steam to adjust the kettle to a target temperature of 150 to 180°C and a target pressure of 0.3 to 0.8 MPa; performing a constant temperature treatment, and then cooling the kettle to 80 to 100°C to end the curing.

[0020] In the above scheme, the constant temperature treatment time is 4 to 6 hours.

[0021] Furthermore, during the process of introducing the high-temperature carbon-containing steam, the heating rate in the kettle is controlled (by controlling the flow rate of the high-temperature carbon-containing steam and auxiliary heating, etc.) to be 1.0-1.5°C / min.

[0022] Furthermore, the cooling rate of the cooling step is 2-3°C / min.

[0023] In the above scheme, the raw materials used in the cement bricks and their weight proportions include: 10-15 parts of ordinary Portland cement, 20-50 parts of aggregate, 30-80 parts of stone powder, and 8-12 parts of water; the raw materials are measured, stirred, sieved, and then pressed into shape to obtain bricks.

[0024] In the above scheme, the ordinary Portland cement is of P·O42.5 grade or above.

[0025] In the above scheme, the aggregate includes but is not limited to waste concrete, mine aggregate waste, slag, etc., with a particle size of 1 to 15 mm and a solidity index of 10 to 30%.

[0026] In the above scheme, the particle size of the stone powder is 0.01-1 mm, and the quartz content is less than 20 wt%.

[0027] In the above scheme, the stirring time is 2 to 5 minutes, and the stirring rate is 60 to 120 r / min.

[0028] In the above scheme, the sieve mesh used in the screening process has an aperture of 15 to 20 mm, and the material under the sieve is pressed and formed.

[0029] In the above scheme, the pressing molding pressure is 5 to 15 MPa.

[0030] The finished cement bricks prepared according to the above scheme have higher strength (strength grade can reach MU20) and lower shrinkage performance (drying shrinkage 0.02% to 0.03%).

[0031] The performance optimization mechanism of cement brick curing of the present invention includes:

[0032] 1) After the exhaust steam is filtered, the condensed water droplets with larger diameters are removed, and then the exhaust steam is mixed with the high-temperature cement kiln tail gas by high-speed injection. The condensed water droplets with smaller diameters are further dispersed, and heat exchange is quickly carried out to form high-temperature steam, which improves the preparation efficiency of high-temperature carbon-containing steam and can effectively control its relative humidity. During the curing process, the initial temperature of the brick is low. When saturated water vapor is used for curing, a large amount of condensed water is easily formed on the surface of the brick, which inhibits the diffusion of carbon dioxide into the interior of the brick; when high-temperature carbon-containing steam is used for curing, the water vapor is not in a saturated state, which can greatly reduce the condensed water on the surface of the brick, ensuring that the carbonization and hydration processes proceed simultaneously. In addition, a layer of carbonized product layer can be formed on the surface of the brick at the beginning of the curing of the brick, which inhibits the cracking problem caused by temperature stress caused by uneven heating of the brick during the curing process.

[0033] 2) During the curing process of the brick, the cement inside the brick accelerates the reaction under high temperature conditions to generate reaction products such as calcium silicate hydrate and calcium hydroxide, among which calcium silicate hydrate can provide higher gel strength, while calcium hydroxide basically has no contribution to strength and has strong water absorption, because the alkalinity and solubility of calcium hydroxide are higher than those of calcium silicate hydrate; under the high temperature, high pressure and high humidity carbon-containing steam curing conditions provided by the present invention, the hydration product calcium hydroxide is promoted to react preferentially with the carbon dioxide in the high temperature carbon-containing steam to generate calcite, effectively retaining the calcium silicate hydrate with higher performance (significantly avoiding the calcium silicate hydrate from participating in the carbonization reaction to form silica gel, etc.); and the obtained calcite has high strength, small shrinkage and good water resistance, which promotes further increase in the strength, shrinkage and water resistance of the brick.

[0034] 3) High temperature environment can significantly increase the diffusion rate of carbon dioxide, and the moisture content of the bricks gradually decreases during the curing process, providing a rapid diffusion channel for carbon dioxide; promoting the carbonization reaction to proceed more evenly inside and outside the bricks, avoiding the performance degradation caused by uneven carbonization inside and outside the bricks.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] 1) Exhaust steam has a high enthalpy, and there is basically no loss in the process of mixing with kiln tail exhaust gas to prepare high-temperature carbon-containing steam. The thermal efficiency is much higher than that of using kiln tail exhaust gas to prepare steam; the treated exhaust steam is mixed with kiln tail exhaust gas by high-speed injection to increase the heat exchange rate between the two gases, and can effectively control the relative humidity of the mixed gas, effectively ensure the diffusion rate of carbon dioxide, and make the carbonization and hydration rates coordinated.

[0037] 2) The present invention uses high-temperature, high-pressure, high-humidity carbon-containing steam to cure cement bricks, and carbonization and hydration reactions are carried out simultaneously, with high reaction efficiency; in addition, the carbonization reaction is promoted by utilizing the characteristics of fast diffusion rate but low solubility of carbon dioxide under the above-mentioned curing conditions, mainly carbonizing the cement hydration product calcium hydroxide to improve performance, while effectively avoiding the problem of performance degradation caused by carbonization decomposition of hydrated calcium silicate; the obtained cement brick products have good mechanical properties and water resistance, etc.

[0038] 3) The preparation method involved in the present invention is relatively simple, can realize high value-added resource utilization of various industrial waste gases, has significant economic and environmental benefits, and is suitable for promotion and application. DETAILED DESCRIPTION

[0039] The present invention will be further described in detail below in conjunction with the embodiments to facilitate a clearer understanding of the present invention, but they do not limit the present invention.

[0040] In the following examples and comparative examples, the cement used to prepare cement bricks is P·O42.5 ordinary Portland cement, the aggregate is mine aggregate waste, the particle size is 1-5mm, the firmness index is 12%, the stone powder particle size is 0.01-0.5mm, the limestone content is 78wt%, the clay mineral content is 13wt%, and the quartz content is 8wt%.

[0041] The preparation method of the cement brick comprises the following steps: 12 parts (by weight, the same below) of ordinary Portland cement, 35 parts of aggregate, 53 parts of stone powder and 10 parts of water are stirred at a rate of 90 r / min for 5 minutes, passed through a 15 mm sieve, and pressed at a pressure of 12 MPa to obtain a brick.

[0042] In the following examples, the cement kiln tail gas was taken from Huaxin Cement Wuxue Plant, with a temperature of 375°C, a pressure of 0.1 MPa, and a carbon dioxide concentration of 22%. The cement plant waste heat power generation exhaust steam was taken from Huaxin Cement Wuxue Plant, with a temperature of 52°C and a pressure of 0.08 MPa.

[0043] Example 1

[0044] A method for curing cement bricks with exhaust steam, comprising the following preparation steps:

[0045] 1) Exhaust steam passes through an 800-mesh gas-liquid filter to remove condensed water droplets with larger diameters;

[0046] 2) compressing the exhaust gas after passing through the gas-liquid filter to 0.15 MPa, and injecting it into the cement kiln tail gas at a speed of 25 m / s through a gas injector to obtain a mixed gas, wherein the mass ratio of the cement kiln tail gas to the compressed exhaust gas is 1:1.2;

[0047] 3) Compress the mixed gas to 0.8 MPa to obtain high-temperature carbon-containing steam; the temperature is 180° C., the carbon dioxide concentration is 9 vol%, and the relative humidity is 78%.

[0048] 4) When curing the bricks with high-temperature carbon-containing steam, first evacuate the machine to a vacuum degree of -0.06MPa; then introduce high-temperature carbon-containing steam, and control the temperature in the kettle to rise to 160°C at a rate of 1.2°C / min, and the pressure reaches 0.6MPa; enter the constant temperature stage, and the constant temperature time is controlled at 6h; after the constant temperature ends, drop the temperature to 90°C at a rate of 2.5°C / min, then open the kettle to end the curing.

[0049] Example 2

[0050] A method for curing cement bricks with exhaust steam, wherein the curing method is substantially the same as that in Example 1, except that the temperature in the constant temperature stage is 180° C. and the pressure is 0.8 MPa.

[0051] Example 3

[0052] A method for curing cement bricks with exhaust steam, wherein the curing method is substantially the same as that of Example 1, except that the mass ratio of cement kiln tail exhaust gas to exhaust gas is 1:1.5, the mixed gas is compressed to 0.8 MPa to obtain high-temperature carbon-containing steam; the temperature is 165° C., the carbon dioxide concentration is 8 vol%, and the relative humidity is 86%.

[0053] Comparative Example 1

[0054] A curing method for cement bricks, which is substantially the same as that of Example 1, except that saturated steam (temperature 195°C, pressure 1.3MPa) is used to cure the bricks, and the bricks are cured at a constant temperature of 180°C and a pressure of 1.1MPa for 6 hours.

[0055] Comparative Example 2

[0056] A curing method for cement bricks, which is substantially the same as that of Example 1, except that: the mass ratio of cement kiln tail gas to exhaust gas is 1:2, the mixed gas is compressed to 0.8 MPa, and the high-temperature carbon-containing steam is obtained at a temperature of 152°C, a carbon dioxide concentration of 6 vol%, and a relative humidity of 92%; the bricks are cured at a constant temperature of 152°C for 6 hours.

[0057] Comparative Example 3

[0058] A method for curing cement bricks, which is substantially the same as that of Example 1, except that the mass ratio of cement kiln tail gas to exhaust gas is 1:0.6, the mixed gas is compressed to 0.8 MPa, and the high-temperature carbon-containing steam is obtained with a temperature of 212° C., a carbon dioxide concentration of 14 vol%, and a relative humidity of 59%.

[0059] Comparative Example 4

[0060] A method for curing cement bricks, which is substantially the same as that of Example 1, except that the exhaust gas used is not passed through a gas-liquid filter and is directly used to prepare a mixed gas, and the mixed gas is compressed to 0.8 MPa to obtain high-temperature carbon-containing steam; the temperature is 171°C, the carbon dioxide concentration is 7 vol%, and the relative humidity is 93%.

[0061] Comparative Example 5

[0062] A curing method for cement bricks, which is substantially the same as that of comparative example 1, except that: after the bricks are autoclaved and cured, they are carbonized and cured for 3 hours (carbon dioxide concentration 20%, temperature 195°C, pressure 0.3MPa, relative humidity 90%)

[0063] The cement bricks obtained in Examples 1 to 3 and Comparative Examples 1 to 5 were subjected to performance tests according to standard GB / T 2542-2012. The results are shown in Table 1.

[0064] Table 1 Cement brick performance test results

[0065]

[0066] The present invention is not limited to the above-mentioned embodiments. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention. The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in this field.

Claims

1. A method for curing cement bricks with exhaust steam, characterized in that: The steps include: 1) Exhaust steam passes through gas-liquid filter; 2) compressing the exhausted gas after passing through the gas-liquid filter and spraying it into the high-temperature carbon-containing gas to obtain a mixed gas; 3) compressing the mixed gas to obtain high-temperature carbon-containing steam; 4) Use high temperature carbon-containing steam to cure cement bricks.

2. The method according to claim 1, characterized in that The temperature of the exhaust steam is 40-80° C., and the pressure is 0.05-0.1 MPa.

3. The method according to claim 1, characterized in that The pore size of the gas-liquid filter is 500-1000 meshes.

4. The method according to claim 1, characterized in that: The pressure of the exhaust steam after compression is 0.12~0.15MPa.

5. The method according to claim 1, characterized in that: The temperature of the high-temperature carbon-containing gas is 300-400° C., the pressure is 0.05-0.1 MPa, and the concentration of carbon dioxide is 15-30%.

6. The method according to claim 1, characterized in that The mass ratio of the high-temperature carbon-containing gas to the compressed exhaust gas in the mixed gas is 1:1.2-1.

8.

7. The method according to claim 1, characterized in that The high-temperature carbon-containing steam has a temperature of 150-180° C., a pressure of 0.3-0.8 MPa, a carbon dioxide concentration of 8-12 vol%, and a relative humidity of 75-90%.

8. The method according to claim 1, characterized in that The steps of curing the bricks with high-temperature carbon-containing steam include: first, evacuating the air with a vacuum degree of -0.04 to -0.08 MPa; then introducing high-temperature carbon-containing steam to adjust the kettle to a target temperature of 150 to 180°C and a target pressure of 0.3 to 0.8 MPa; performing a constant temperature treatment, and then cooling the kettle to 80 to 100°C before opening the kettle to end the curing.

9. The method according to claim 1, characterized in that: The raw materials used in the cement brick blank and their weight proportions include: 10-15 parts of ordinary Portland cement, 20-50 parts of aggregate, 30-80 parts of stone powder and 8-12 parts of water.

Images