Types of fly ash (1) "Desulfurization Ash" Circulating fluidized bed boiler technology can efficiently burn high-sulfur coal. In order to reduce SO2 emissions, it is often necessary to take desulfurization measures. The generated fly ash is CFB desulfurized fly ash. It contains a large amount of sulfide or sulfate (such as gypsum, etc.), which is different from traditional fly ash. If it is used in concrete without testing, it will cause serious concrete cracking and disintegration. Although the current fly ash standard has SO3 content limit, the inspection and judgment of "desulfurized ash" lacks pertinence. Today's fly ash contains a large amount of sulfide or sulfate (such as gypsum, etc.), which is different from traditional fly ash. If it is used in concrete without testing, it will cause serious concrete cracking and disintegration. Although the current fly ash standards have SO 3 content restrictions, the inspection and determination of "desulfurized ash" lack pertinence. (2) "Denitration ash" In order to reduce the emission of NO x in the coal combustion process, it is necessary to carry out "denitration" treatment during the coal combustion process. Improper denitration process may result in some residual NH4 in the fly ash. When the fly ash is mixed with cement, it will encounter alkali The natural environment will release NH 3 (ammonia gas), which produces a lot of gas in the plastic stage of concrete. (3) "Floating black ash" In modern coal combustion technology, in order to improve the efficiency of coal combustion or some special operating requirements of power plants, diesel or other oily substances are added as combustion aids in the coal combustion process. These combustion aids cannot be completely burned and will remain in the fly ash. Oil. Especially after the fly ash is sorted, the collected fly ash will contain more unburned oil, which is used to mix concrete. These oils float up and appear as floating black oil in the concrete. This kind of fly ash is called "floating black ash". How to identify? (1) How to see Experienced inspectors can often know the fineness and ignition loss of fly ash just by observing the color of fly ash. The appearance of fly ash is similar to cement, and the color varies from milky white to gray-black. The color of fly ash is an important quality indicator that can reflect the amount and difference of carbon content, and to a certain extent, it can also reflect fly ash. The fineness. The darker the color, the finer the particle size of fly ash and the higher the carbon content. Fly ash is divided into low-calcium fly ash and high-calcium fly ash. Generally, the color of high-calcium fly ash is yellowish, and the color of low-calcium fly ash is grayish. The fly ash particles have a porous honeycomb structure with a large specific surface area and high adsorption activity. The particle size ranges from 0.5 to 300 μm. In addition, the bead wall has a porous structure with a porosity as high as 50% to 80%, and it has strong water absorption. In addition to the natural appearance, you can also add water and stir to observe the fly ash. In a beaker of water, add an appropriate amount of fly ash to quickly stir evenly to check whether there is black ash floating on the water surface to check the amount of carbon in the fly ash; if the color of the fly ash is black and has a peculiar smell, Oil droplets, this kind of fly ash should be floating putty and should be returned. After desulfurization ash containing higher free CaO and SO3 is stirred with water, the solution becomes alkaline, and phenolphthalein reagent is dropped into it, which appears red. In order to prevent the concrete from cracking due to the volume expansion of Ca(OH) 2 and hydrated calcium sulfoaluminate, the product must be returned. Secondly, you can smell the smell. Take an appropriate amount of fly ash and cement in a beaker and add water and stir to form a slurry. If you can smell the pungent ammonia smell, the fly ash can be judged as denitrified ash. Look with a microscope! To identify fake ash, first sieving. Generally speaking, fly ash particles with a smaller particle size are more smooth and glass spherical under the microscope (using a microscope above 100 times), and the surface of the particles with a larger particle size is irregular but also Roughly spherical. If too much ground sand powder, stone powder, boiler slag powder is mixed, there will be more irregular particles in each particle size level, especially in the small particle size level, which will appear irregular and angular. Do I have to carry a microscope to distinguish it? A simple method is: take a little about 1kg of fly ash and put it into a basin, then add water to it, and stir while adding water until it is almost full, and see if there is a layer of white floating beads on the surface of the water, if there is Really, if it doesn't, it's fake. For fly ash, first sieving. Generally speaking, fly ash particles of smaller particle size class have more smooth glass balls under the microscope, and the surface of particles of larger particle size class is irregular but roughly spherical. If too much ground sand powder, stone powder, boiler slag powder is mixed, there will be more irregular particles in each particle size class, especially in the small particle size class. Real fly ash has strict national standards and application specifications, as well as strict chemical composition and radioactivity standards. Packaging specifications, clear grade standards. The color is black and yellow, powdery, the particles are very fine, the hand feels fine and dry, and the moisture content is very low. The fake fly ash is mainly made of stone powder, brick powder mixed with a small amount of fly ash or slag, and some or all of it is directly packaged with stone powder. False fly ash itself is not viscous and has no activity. The color is white, and some colors are very impure. The hand feel is rough, wet, and the packaging bag is irregular. Pay attention to the above issues when purchasing fly ash to ensure that you can buy high-quality fly ash. (2) How to do acceptance sampling? Change the traditional sampling method and position, that is, weld a special sampling tap on the fly ash feeding steel pipe with a diameter of 100mm at a vertical height of about 1.5 meters from the ground, which can be randomly selected at any time during the fly ash unloading process. Take samples and publicly inform the fly ash supplier that if the results of the two samplings are found to be different in the same vehicle, they will be severely punished. When sampling, you should pay attention to whether the fly ash in the two holes before and after the tanker is the same, and sample it flexibly! (3) Chemical testing Fly ash is sintered at high temperature. It will not react when mixed with hydrochloric acid or oxalic acid used by concrete companies to wash cars. The main cost of fake ash is that CaCO3 will generate bubbles immediately when it encounters acid.