China's cement industry has a large production capacity and many dust sources. It is a large user of bag dust collectors
. A large number of waste dust bags
in cement plants will be produced every year. At present, these waste dust bags
in these cement factories have not been properly treated. Most treatment methods are simply landfilled or stacked everywhere, which causes very serious damage to the ecological environment and restricts the sustainable development of China's cement industry. Incineration is one of the most effective ways to reduce waste and harmless waste bags. After incineration, the chemical fiber bag becomes CO2 and H2O, and the glass fiber bag becomes SiO2 after chemical reaction. Dust bag dust after incineration is a general waste and contains active components such as CaO, SiO2, Al2O3, etc., which has a high value for recycling. In addition, cement concrete can effectively cure harmful components, which has become a recognized effective way to deal with various wastes. In this paper, the waste ash bag incineration ash is used as a cement mixture. The effects of waste bag incineration ash on the physical properties, working performance and structure of the cement are systematically studied. Technical specifications, with a view to providing a practical technical route for the harmlessness and recycling of waste dust bags in cement plants. The School of Environment and Engineering of Guangdong University of Technology uses two waste cloth bags from a cement plant in Longmen County, Guangdong Province, puts them in a muffle furnace and burns them at 900 ° C for 1 hour, and then takes the incineration ash.
It was found that the burning loss of the chemical fiber cloth bag reached more than 75%. After the incineration, the slag was ground into a gray powder by a ball mill and stored under dry conditions for use. The loss on ignition of the fiberglass cloth bag is almost 0, but it turns into a hard and brittle solid after incineration. It is ground into a ball mill and pulverized into a white powder, and stored under dry conditions for use. The composition of chemical fiber bag ash is close to that of cement clinker, the content of CaO is slightly lower than that of cement clinker, and the content of SO3 is higher, up to 3.29%; the most content in glass fiber bag ash is SiO2, up to 48%, while The content of CaO, Al2O3 and other components is relatively small. According to GB2847-2005, the material used as a cement mixing material must have a loss on ignition of less than 10% (the loss on ignition of the slag after incineration of the two bags is much lower than 10%), the content of SO3 is less than 3.5%, and SiO2, CaO, and Al2O3 are relatively high. It can be seen that both types of bag incineration ash are suitable for use as cement mixture.
See the above burnt ash mixed with clinker, slag and gypsum in a ball mill to prepare cement in accordance with different experimental proportions. The specific surface area of the cement is controlled at (300 ± 10) m2˙Kg-1, and the cement standard is tested according to standard methods Consistency water consumption, setting time, stability and cement mortar strength.
With the addition of two types of bagged incineration ash, the water consumption of standard consistency of bagged ash cement is increasing, and the more the amount of incinerated ash added, the greater the standard consistency. The influence of chemical fiber bag incineration ash on the standard consistency of cement is obvious. When the ash content is 30% and 40%, the standard consistency reaches 32% and 34.4%, respectively. This is because the chemical fibers in the chemical fiber cloth bag incineration ash and some of the pulverized coal collected in the bag after combustion have left a lot of loose and porous substances. This substance has a strong adsorption capacity for moisture, resulting in the standard consistency of the chemical fiber cloth bag ash cement. Water consumption has increased significantly. The particle size of the silicon powder in the glass fiber bag incineration ash is small, which can fill the gaps between the coarse cement particles and produce a micro-aggregate effect. As a result, the particle size distribution of the system is more reasonable, and the water filled in between the cement particles can be replaced. This filling increases the available free water in the mixture and helps to reduce the water consumption of the standard consistency of the cement. However, because the particle size of the glass fiber bag incineration ash is small and the specific surface area is large, the surface adsorption of the system is caused The amount of water also increases, which decreases and increases, eventually leading to an increase in the consistency of the cement slurry. However, the increase in the consistency of the glass fiber bag ash cement was within a reasonable range.
The experimental results show that the incorporation of two kinds of bagged incineration ash will prolong the initial and final setting time of cement. When the content of chemical fiber bag incineration ash is 10% -20%, the setting time of cement will be extended slightly, and when its content exceeds 30%, the setting time of cement will be prolonged significantly, which may be related to the increase of water consumption. The addition of ash significantly prolongs the setting time of the cement. The setting time of the cement is more than doubled when the amount is 30% and 40%. The mechanism may be higher than that of the glass fiber bag incineration ash slag. CaO content is related.
Activity and cement performance indicators
The main index for judging whether a mixed material is an active or inactive mixed material is the compressive strength ratio of cement mortar 28d R28. According to GB2847-2005, R28 greater than 65% is an active mixed material, and R28 less than 65% is an inactive mixed material. .
The experiment found that when the amount of chemical fiber bag ash cement and glass fiber bag ash cement is 30%, the R28 of the activity test is 91.0% and 80.6%, which are much higher than 65%. From this, it can be considered that both cloth bag incineration ash has a relatively high activity and can be used alone as a cement mixture.
When the amount of chemical fiber bag ash cement is 10% -20%, its strength meets the requirements of 52.5R strength grade cement. When the content is 30% -40%, its strength meets the requirements of 42.5R strength grade cement. The strength of glass fiber bag ash cement meets the requirements of 42.5R strength cement when the content is 10%, 20%, 40%, while the strength of glass fiber bag ash cement is only 32.5R strength. It shows that the activity of chemical fiber bag incineration ash is higher than that of glass fiber bag incineration ash.
When the incineration ash content of the chemical fiber cloth bag is 10% -20%, the flexural and compressive strength of the chemical fiber cloth bag ash cement 3d and 28d reaches or exceeds the strength of the reference cement of the same age S number. When the content is more than 20%, the strength of the cement begins to decrease. When the content is 20% -30%, the strength of the chemical fiber bag ash cement decreases 3d and 28d, and when the content is 30% -40%, the strength decreases. Becomes smaller, the 28d flexural strength of H4 cement even exceeds that of H3 cement significantly; the 3d and 28d flexural strength of glass fiber bag ash cement show a downward trend when the amount is 10% -30% and 10% -20%, respectively, and They were rising at 30% -40% and 20% -40%, respectively. The compressive strength of glass fiber bag ash cement 3d and 28d generally decreases with the increase of the content, but the 28d compressive strength of B4 cement is higher than that of B3 cement. It can be seen that the flexural and compressive strength curves of the fiberglass bag ash cement show U-shaped changes. With the increase of the blending amount, the 3d compressive strength of glass fiber cloth bag ash cement has a larger declining range, the maximum declining range reaches 37.3%, while the 28d compressive strength declining range is smaller, the maximum declining range is 19.4%.
The strength variation of two types of waste cloth bag incineration ash with different mixing ratios of cement can be generally expressed as: when the amount of chemical fiber bag ash cement is less than 20%, its compressive strength reaches or even exceeds the same age S No. refer to cement. When the content of incineration ash in chemical fiber cloth bags is greater than 30%, the strength of chemical fiber cloth bag ash cement decreases sharply; as the content of glass fiber cloth bag ash cement increases, its strength generally decreases, and the flexural and compressive strength curves show U The change law of the type of glass fiber bag ash cement at 28d is less than that at 3d.
Cement dust bag
(1) Both types of bagged incineration ash have high hydration activity, and the indicators such as loss on ignition and SO3 content meet the GB2847-2005 standard, and can be used alone as a cement mixture.
(2) Within the range of chemical fiber bag incineration ash content of less than 20%, the flexural and compressive strength of cement at all ages reaches or exceeds the reference cement of the same age S number. When the content exceeds 30%, the strength of the cement decreases significantly; glass fiber When the amount of bagged incineration ash is less than 10%, the strength of the cement is almost unchanged compared to the reference cement of the same age S number. When the amount of incineration ash exceeds 20%, the 3d strength declines more, and the 28d strength decreases less.
(3) In the range of less than 40% of the incineration ash of the two kinds of cloth bags, except for the B3 sample, the other indicators of the cement stability, setting time and cement strength meet the 42.5R strength level in GB175-2007 Cement requirements, of which H1 and H2 cement meet the 52.5R grade cement strength requirements.
(4) Two types of waste bag incineration ash are used as the cement mixture, which not only expands the source of the cement mixture, but also realizes the harmlessness and resource utilization of the waste dust bag of the cement plant, which has better economic and environmental benefits.