Large vertical mill is widely used in modern cement industry and the maintenance of its supporting components is related to the normal production of vertical mill. The large reducer supporting the vertical mill should be included in this column. Once an accident occurs, the site maintenance is difficult, the technical content is high, and the maintenance cycle is long, which has a great impact on the normal production and operation of enterprises. Many cement enterprises' response measures are: to spend high costs to purchase spare machine, in case of a rainy day; Or the use of winter peak stop production opportunities, the machine back to the factory maintenance, is bound to spend high back and forth transportation costs. This shows that the on-site inspection and maintenance method of large reducer is very important.
Professional inspection: Device inspection is the most important method to discover potential faults.
Common faults: high speed shaft bearing damage, high speed shaft bevel gear tooth broken, high speed shaft two bearings between the interval sleeve loose, parallel axis external tooth spline shaft and internal tooth spline sleeve surface wear, equipment vibration
Fault maintenance: invite professional reducer maintenance team to enter the factory, selectively carry out on-site maintenance and return to the factory maintenance, reducer foundation shaking treatment
Review on incineration compatibility of hazardous waste
Feed compatibility of hazardous waste is the most basic and critical step in incineration disposal process, which is of great significance to the economic and reliable combustion process. Scientific and effective incineration compatibility is conducive to stable operation of incineration system, protection of system equipment, improvement of disposal capacity, pollutant discharge standards, and reduction of operating costs.
1. Ensure that the calorific value of materials entering the rotary kiln is stable within a certain range to ensure the economy and reliability of system operation.
2. Control the proportion of halide and organic matter to reduce the corrosion of waste heat boiler and flue gas treatment equipment caused by acid pollutants in flue gas produced by combustion.
3. Control the content of halides and heavy metals to ensure the treatment effect of incineration smoke and normal exhaust emissions.
4. Control the content of chlorine-containing organic waste in kiln, and reduce the generation of dioxins in incineration process from the source.
5. Control alkali metal and other low melting point content, control system coking and structure blockage, reduce the impact on refractory materials.
6. Make full use of a variety of feeding channels and stable burning conditions to avoid large instantaneous fluctuations when entering the kiln.
7. Control the moisture stability of materials to ensure the normal drying stage of waste and improve waste disposal efficiency.
The composition and structure of polymer waste are quite complex. In the process of combustion, they can be completely decomposed into low-molecule combustible gas through continuous multistage thermal decomposition reaction, and finally converted into combustion reaction, and release combustion heat.
When burning plastics, rubber, paint and asphalt in the air, the smoke can spread to 30-40 meters in the air. This is because: first, complete gasification is not equal to complete pyrolysis. Solid (liquid) polymer waste can be completely gasification, but complete gasification does not mean that the toxicity of organic pollution can be harmless; Second, thermal decomposition and combustion, conceptually, thermal decomposition and thermal combustion are two completely different reactions, thermal decomposition is endothermic reaction, combustion is exothermic reaction, only a relatively complete decomposition, can achieve a relatively complete combustion; Third, after the complete decomposition of the thick black combustible gas, the exothermic complete combustion reaction can be carried out, and the toxicity of organic pollution can be harmless. Billowing black smoke is caused by incomplete thermal decomposition, uneven combustion oxygen supply and incomplete combustion.
Technology | fourth-generation tail roller broken upgrade of grate cooler
1. Analysis of existing problems
The firing system of the production line is equipped with ф4.8m×72m rotary kiln, five-stage double-series preheater and grate cooler for the fourth generation of stepping grate cooler. The main problems before the transformation are as follows:
(1) The second and third air temperature of grate cooler is not high, and the second air temperature is about 1050~1100℃, and it is unstable.
(2) The grate cooler covers an area of only 138.3m². The outlet clinker temperature of the grate cooler is often higher than 120℃, and red material sometimes appears.
(3) Power generation per unit of clinker waste heat is low.
2. Solutions
(1) Automatic air volume control valve, save wind and electricity, help to ensure the thermal stability of the system;
(2) With the snowman elimination device, so that the grate bed layer is more stable;
(3) High heat recovery efficiency, generally guaranteed above 75%, to avoid the phenomenon of high temperature of outlet clinker;
(4) The use of decentralized independent single row hydraulic drive, high reliability of operation, greatly reduce the risk of kiln shutdown due to grate cooler failure;
(5) The use of cross rod conveying clinker, its high conveying efficiency, less wearing parts, low maintenance;
(6) Modular grate bed, grate plate fixed, only cooling effect, high reliability;
(7) The use of special sealing structure, no leakage, no leakage conveying device, low maintenance;
(8) Strong crushing capacity of roller, large diameter of crushing roller, and equipped with "lower roller" (increased crushing Angle, strong crushing capacity of large materials), frequency conversion speed regulation.
Concrete plans: overall demolition of the grate cooler ontology and cooling fan, according to Smith company design the shell at draught on docking with the waste heat power generation and waste gas outlet, the overall change of a cross bar grate cooler, make grate cooler and roller broken again, continue to use the original inclined zipper machine foundation, new grate cooler outlet discharge valve is directly linked to the inclined zipper machine.
3. Program implementation
The transformation will be carried out during the overhaul period after the Spring Festival of 2021, lasting a total of 40 days, to ensure the re-ignition and feeding of the production line to the maximum extent. So far, production has been stable.
The modification of grate cooler in front of middle roller break is shown in the diagram. For the grate bed and intermediate crusher after the new grate cooler roller is broken, the foundation shall be excavated and made again. The grate bed foundation of the section after roller breaking is about 2.3m below the ground. The base elevation of the zipper remains the same in order to minimize civil excavation. The transformation of the new grate cooler after the middle roller is broken is shown in the figure.
4. Technical transformation effect
After modification, the equipment runs stably, and the secondary air temperature runs stably above 1150℃. See the equipment configuration and effect comparison before and after the cooling machine transformation.
Grate cooler is one of the core systems of sintering equipment, which not only undertakes the tasks of clinker cooling and conveying, but also improves the quality of clinker, the grillability of clinker and the efficiency of heat recovery. Its use effect will directly affect the whole firing system operation rate, coal consumption, power consumption and other important indicators. Because of the importance of grate cooler, many cement enterprises are carrying out the optimization and transformation of grate cooler to further optimize the firing system index. This technical modification proves that compared with the tail grate cooler with broken roller, the central roller breaker can 100% ensure that the outlet clinker temperature of the grate cooler is lower than the ambient temperature +65℃, and is basically not affected by kiln conditions and clinker granation. Due to the position of the central roller breaker, more waste heat will be used for power generation, rather than wasted in nothing.
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