1. The phenomenon of dust accumulation in the air preheater
If the air preheater deposits in the operating unit, it will cause the primary and secondary air pressure at the inlet and outlet of the air preheater to swing and rise, the pressure difference between the primary and secondary air pressure will gradually increase, and the air temperature at the outlet of the air preheater will be increased. Reduced, the current of the induced draft fan increased significantly under the same load.

Second, the reason analysis of air preheater dust accumulation
1. The heat transfer elements of the air preheater are closely arranged
The heat transfer elements of the air preheater are closely arranged. The flow area of ​​flue gas through the corrugated plate is very small and the flow process is very long. At this time, the fly ash in the flue gas is easy to deposit on the heated surface, causing the air preheater to block ash;

2. Combustion method under low load
In order to ensure the safe operation of the boiler under low-load operation of the unit, the unit is often mixed with coal and oil. Unburnt fly ash combustibles easily adhere to the heating element of the air preheater;

3. The presence of ammonium bisulfate (ABS) after denitration
The melting point of ammonium bisulfate is 147 ℃, which is mainly deposited in the smoke temperature range: 207-147 ℃, which will be transformed from gaseous state → liquid state → solid state, according to the temperature gradient distribution, combined with the temperature structure inside the air preheater, sulfuric acid Ammonium hydrogen usually exists in the middle of the cold end element of the preheater, adsorbs ash when the liquid state is converted to the solid state, and is deposited directly on the heat transfer element;

3. The hazards of ash plugging to the air preheater
After the heating surface of the air preheater is blocked with dust, the originally relatively small heat transfer area is further reduced, and the flow resistance of the flue gas is increased, which causes the load of the induced draft fan to increase and the power consumption rate of the plant to increase. In the case of serious ash blocking, the load of the unit is restricted due to the limited output of the induced draft fan. In addition, ash plugging reduces the surface heat transfer area of ​​the heat exchange element of the air preheater, resulting in a reduction in the amount of flue gas heat exchange per unit area and poor heat transfer effect. The flue gas temperature at the outlet of the furnace rises; at the same time, the pressure difference between the flue gas and the air at the inlet and outlet of the heated area is increased, which increases the speed of fly ash and accelerates the wear of the heated surface of the air preheater.

Soil remediation is a technical measure to restore the normal function of contaminated soil. In the soil remediation industry, there are more than 100 existing soil remediation technologies, and more than ten commonly used technologies, which can be roughly divided into three methods: physical, chemical, and biological.

Fundamentally speaking, the technical principles of remediation of contaminated soil can include:
(1) Change the existing form of the pollutants in the soil or the combination with the soil to reduce its mobility and bioavailability in the environment;
(2) Reduce the concentration of harmful substances in the soil.

Soil remediation techniques are summarized as follows:
1.  Thermodynamic remediation technology, using heat conduction, thermal blankets, thermal wells or thermal walls, etc., or thermal radiation, radio wave heating, etc. to achieve the restoration of contaminated soil;
2.  Thermal desorption repair technology, heating the soil contaminated with organic matter above the boiling point of the organic matter by heating, so that the organic matter in the adsorbed soil volatilizes into a gaseous state and then separated and processed;
3.  Incineration method, incineration of contaminated soil in an incinerator to volatile and semi-volatile high-molecular-weight harmful substances, and decomposition into low-molecular flue gas through dust removal, cooling and purification treatment to achieve flue gas emission standards;
4.  Landfilling method, using waste as a slurry, applying sludge into the soil through fertilization, irrigation, adding lime, etc. to adjust the nutrition, humidity and PH value of the soil to maintain aerobic degradation of pollutants in the upper layer of the soil;
5. Chemical leaching, soil leaching is a soil remediation method that uses the leaching solution to transfer the heavy metals in the solid phase of the soil to the liquid phase of the soil, and then further recycles the waste water rich in heavy metals. The leaching method is only suitable for medium-loam soil, sandy loam soil and sand soil with good water permeability. It is difficult to implement on clay, and sand can be added to increase the leaching rate. The leaching method has a good effect on the treatment of heavily contaminated soil, but it is easy to cause groundwater pollution. Although heavy metal ions can be leached out of the soil, it can also cause the loss of nutrients in the soil and cause the decline of soil fertility.

1. Dry garbage, also called inorganic garbage (recyclable garbage):
It mainly includes five categories of waste paper, plastic, glass, metal and fabric, and also includes waste vehicles, household appliances and furniture, decoration waste, coal ash slag, muck, broken bricks and ash, etc. Most dry garbage can be Use after recycling. Waste paper mainly includes newspapers, periodicals, books, various packaging papers, office papers, advertising papers, paper boxes, etc., but it should be noted that paper towels and toilet papers are not recyclable due to their strong water solubility. Plastics mainly include various plastic bags, plastic packaging, disposable plastic lunch boxes and tableware, toothbrushes, cups, mineral water bottles, toothpaste skins, etc. Glass mainly includes various glass bottles, broken glass pieces, mirrors, light bulbs, thermos bottles, etc. Metals mainly include cans, cans, etc. Cloth mainly includes waste clothes, tablecloths, face towels, school bags, shoes, etc.

2. Wet garbage, also known as organic garbage (including kitchen waste, etc.):
It is waste that is easily decomposed under natural conditions, including leftovers, bones, root vegetable leaves, rotten fruits, melon peel, coffee and tea residues, eggshells, peanut shells, bread, cereals, garden and plant waste, crop straw , Bones, seafood shells, shrub branches, small wooden blocks, small wooden strips, waste paper, animal fur, hair, discarded feces and other food wastes, composted in situ by microbial fermentation treatment technology.

3. Harmful garbage:
Substances that cause direct or potential harm to human health or the natural environment, including waste batteries, waste fluorescent tubes, waste water silver thermometers, waste paint buckets, corrosive detergents, waste small electronic products, medical waste, radioactive waste, expired Drugs, pesticides, etc., these wastes need special treatment.

4. Other garbage:
Including bricks, ceramics, muck, toilet waste paper, paper towels and other wastes other than the above-mentioned types of garbage, hygienic landfill can effectively reduce the pollution of groundwater, surface water, soil and air.

Rotary kiln refers to rotary calcination kiln (commonly known as rotary kiln) and belongs to the category of building materials equipment. Rotary kilns can be divided into cement kilns, metallurgical chemical kilns and lime kilns according to different materials processed.

Cement kilns are mainly used for calcining cement clinker, divided into two categories: dry process cement kilns and wet process cement kilns. Metallurgical and chemical kilns are mainly used for magnetizing roasting of iron-poor ore in iron and steel plants in the metallurgical industry; oxidizing roasting of chromium and nickel iron ore; refractory plant roasting high alumina vanadium ore and aluminum plant roasting clinker and aluminum hydroxide; chemical plant roasting chromium ore And chrome ore powder and other minerals.

Lime kiln (ie active lime kiln) is used for roasting active lime and lightly burnt dolomite used in iron and steel plants and ferroalloy plants.

1. Direct heating method: that is, high-temperature gas (which can be direct combustion flue gas or clean air after heat exchange) is input into the kiln, and the gas and materials are fully mixed and contacted for calcination.

2. Indirect heating method: there is a calcination chamber on the outside of the cylinder, the heat generated by the calcination is transferred to the material through the cylinder, and the material is dried, decomposed, calcined and roasted at high temperature. (You can also install a central heating tube to heat the inner and outer cylinder walls of the rotary kiln at the same time, and conduct heat to the materials in the cylinder for calcination)

Rotary kiln calcination installation and commissioning

The installation of rotary kiln involves: lifting and transportation, installation of fitter technology, riveting technology, welding technology, pipeline technology and masonry technology.

1. Construction preparation

In order to ensure the smooth progress of the installation of the cement rotary kiln, the kiln must be inspected and accepted in accordance with the drawings, and the unqualified foundation should be corrected, the debris, chiseling, embedded standards and defense brackets should be removed, and then assembled Longmen hanger, equipment out of storage.

The outgoing warehouse of the rotary kiln equipment must ensure the order of outgoing warehouses and be placed on the construction site reasonably to prevent the installation site from having unfavorable roads or chaotic back and forth transportation. The order of outgoing equipment from the warehouse is: anchor bolts → supporting wheel set → Kiln head cover → Cylinder body, wheel belt, retaining wheel → spring plate, large gear → gear cover → small gear, reducer → engine → auxiliary transmission → smoke chamber and kiln head kiln tail sealing device → burner, cutting device and other attachments.

Check the equipment at the time of leaving the warehouse, clean the equipment according to the relevant requirements, measure the length of simplified Chinese, and then carry out the basic pay-off, lay the horn, the upper surface of the horn should be along the longitudinal direction of the kiln and the slope of the rotary kiln To maintain consistency, the horizontal direction of the kiln must be kept horizontal. In order to accurately and quickly install the equipment at the specified location, there must be an installation reference line no matter the equipment or the specified location. That is, the equipment needs to be scribed, and the center lines of the equipment and equipment must be drawn.

2. Lifting and aligning

The order of hoisting and rectifying is steel base first, then cylinder, first hoist the steel base separately, assemble and perform elevation measurement and rectification on the foundation, when the steel base is adjusted, keep the anchor bolts for grouting and cement mortar pier After the health has reached the strength requirements, then the steel base is corrected for the second time, at the same time, the scraper shaft is scraped, hoisted and paired, and then the supporting roller bearing seat and the supporting roller are found, and the entire tug group is hoisted and aligned. Install the stop wheel.

Lifting and aligning the simplified Chinese, first assemble the cylinder and the wheel, and then align and align the cylinder, and align and align the segments of the cylinder, so that the connection of the center of rotation of each section of the cylinder is on a straight line. Then, connect the large gear ring to the cave body and carry out hoisting and alignment, followed by the positioning and alignment of the transmission device, and then perform the primary bolt grouting alignment and health maintenance, and then perform the secondary alignment of the transmission device.

3. Welding

After the installation and alignment of all the above equipment and the grouting are completed, the kiln body is welded. Generally, manual welding and automatic submerged arc welding are used. After welding, the welding quality is checked, and then the kiln head cover and sealing equipment are installed, followed by cooling and Lubrication system, and then install the coal collision tube, at the same time for the basic secondary grouting, and then carry out no-load debugging and trial operation of the rotary kiln.

4. Masonry refractories

In order to ensure the stiffness and strength of the rotary kiln and make it work normally, after passing the no-load trial operation of the rotary kiln, refractory bricks of different specifications and models are built in the kiln body to protect the rotary kiln from being burned by high temperature during use , Not worn by the material flow.

5. Commissioning

After the installation of the cement rotary kiln equipment is completed, first check whether the technical indicators of the equipment have met the requirements, and the commissioning and trial operation can only be carried out after the relevant departments confirm the qualification. Before commissioning, conduct a comprehensive inspection of the cement rotary kiln and its auxiliary facilities:

(1) Ensure that all fasteners are tightly tightened, and clear all debris inside and outside the kiln, and above and below the foundation, especially between the belt between the gear and the tug;

(2) Check whether there is leakage in each lubricating cold hydraulic system, whether the valve is flexible and reliable, fill oil in place, and the oil pressure, oil temperature and flow rate meet the design requirements;

(3) Check the rotation direction of all instruments, indicators and motors, and comply with the relevant drawings and regulations;

(4) Check the transmission device, there should be no abnormal noise such as impact and vibration, the meshing of the large and small gears should be normal, and the work should be stable;

(5) Check whether the wheel belt and the tug are in normal contact, the contact length is not less than 70%, and the kiln tube body should move up and down smoothly;

(6) Check whether there is any looseness in the devices everywhere, and whether there is friction between the sealing device and the local parts.

If all the technical indexes of the equipment meet the requirements, carry out debugging. When debugging, first debug the main motor. Click the main motor to check and adjust the rotation direction of the main motor so that the relevant parameters of the motor meet the design or regulations .

Start the main motor, run it for 2 hours separately, then drive the main reducer for 4 hours by the main motor, and turn on the cooling and lubrication system, then drive the rotary kiln for 8 hours by the main motor drive transmission system no problem.

According to the survey results of the Ministry of Health, the amount of garbage generated in rural areas can reach 0.86 kg per person per day, 300 million tons per year, and the garbage pollution situation in China’s towns is very severe. Recently, the coordinated disposal of garbage through cement kilns has received widespread attention in the cement industry. In the face of inadequate rural management systems, most townships have insufficient funds, and the township domestic garbage cannot be effectively treated. The advantages are obvious. At present, the pollution pattern of township garbage is increasing towards the total amount of pollution, and the sources of pollution are complex and diverse, which seriously endangers the ecological environment safety and residents’ health.

At present, the main treatment methods of domestic garbage in most villages and towns are open storage, composting and incineration. Due to the lack of reasonable scientific and technical guidance, these treatment measures may cause secondary pollution and fail to achieve the purpose of fundamental treatment. Although a few villages and towns have built landfill sites or incineration plants, they are small in scale and constrained by factors such as funding, management level, and human resources, and ultimately cannot be used to “detoxify” domestic waste. In recent years, various experts and scholars have put their hopes on the treatment and disposal of domestic waste in the cement industry, that is, using the new dry cement kiln with high process temperature, large heat capacity, alkaline atmosphere, negative pressure environment, and no ash and other natural advantages This method has great prospects for the disposal of domestic garbage.

The use of cement kilns to co-process waste has broken through the field of waste treatment systems and established a new domestic waste treatment model. A variety of technologies have been developed at home and abroad for the use of cement kilns to co-process domestic waste:

1. Hot plate furnace mode
A process for setting up an online waste incinerator in a cement kiln system to dispose of domestic waste, that is, using three winds and part of the hot raw materials as a heat source to incinerate domestic waste, and the flue gas and slag generated during the return to the clinker for burning Further disposal in the system.

2.CKK mode
The CKK (Conch Kawasaki Kiln System) mode is a process for parallelly setting up a waste incineration and gasification furnace outside the cement kiln system to dispose of municipal solid waste, that is, using the tertiary air of the kiln system as the main heat source, Incineration, and the incinerated flue gas and slag are introduced into the kiln system for disposal.

3.RDF mode
The RDF (Refuse derived fuel) mode is to build a special domestic waste pretreatment plant to crush, ferment, dry, and sort a series of mixed domestic waste to make an alternative fuel for the cement industry to consume A process of domestic garbage.

The above three models have better adaptability to large amount of investment, large amount of domestic garbage, and better classification and collection of urban domestic garbage. However, the waste disposal cost of the CKK mode is relatively large; the RDF mode and the hot-plate furnace mode have a great transformation effect on the kiln.

Due to the decentralized characteristics of villages and towns, the above model is not suitable for the treatment of villages and towns. Aiming at the domestic garbage of villages and towns, and relying on the technical basis of the new dry-process cement kiln production line, related research proposes a simple mode of co-processing of village and town domestic garbage with cement kiln. This model requires simple pretreatment process of village and town domestic garbage, less transformation of cement kiln, low processing cost, and solves the difficult problem of garbage sorting. The treated domestic garbage meets the requirements of “reduction, harmlessness, and recycling”.

At present, many cities in China and surrounding areas basically have new dry-process cement production lines. Without affecting cement production and product quality, each ton of cement clinker produced can coordinately process 0.06-0.15 tons of domestic waste. China currently has about 1.8 billion tons of new-type dry-process cement clinker production capacity. If all of the domestic garbage can be disposed of collaboratively, more than 110 million tons of domestic garbage can be disposed of annually, and most of the domestic garbage discharged each year can be disposed of. The simple model of cement kiln co-processing village and town domestic garbage has certain reference significance to villages and towns with a small amount of garbage collection and insufficient financial funds.