The clinker burning part of the cement factory production line mainly consists of: preheater system, decomposition furnace, bypass windproof system, kiln tail high temperature fan, exhaust gas treatment system, rotary kiln, firing system, etc. What are the requirements? Let’s take a closer look!
The preheater system should be arranged in accordance with the following regulations:
(1) Under the premise of meeting the production requirements of the production line of the cement factory, it should be arranged compactly, occupy a small area, and the height of the preheater tower should be low;
(2) In addition to the main platform of each layer, the preheater tower shall be provided with a platform in the place where the skin is to be cleaned, operated and maintained, such as preheater and decomposing furnace, and a safe operation space shall be reserved;
(3) The position on the floor of each floor should be temporarily placed with refractory materials during maintenance;
(4) The compressed air system piping should be connected to the main platform of each layer of the preheater tower;
(5) The kiln tail tower should be equipped with a cargo elevator.
The preheater system shall be designed in accordance with the following regulations:
(1) The preheater system shall be arranged in a single row or in a double row according to the production capacity, and a five or six stage preheater shall be adopted;
(2) The technical performance of the preheater should meet the following requirements:
a. The separation efficiency of the top-stage cyclone of the preheater should not be lower than 92%;
b. The sealing performance of the system should be good, and the air lock device should be flexible;
c. The air duct and the material pipe of the preheater shall have measures to absorb thermal expansion;
The selection and design of the decomposition furnace should meet the following requirements:
(1) The furnace type and furnace structure parameters should be determined according to the original and fuel properties;
(2) The residence time of the gas in the decomposition furnace can be determined according to the type of the decomposition furnace and the original and fuel properties; the fuel should be completely burned in the decomposition furnace, the gas residence time should be greater than 5 s; the apparent decomposition rate of the human kiln material should reach 92%. the above;
(3) The proportion of coal used in the decomposing furnace should be 55%~65% of the total coal consumption; when the bypass is used, the proportion of coal used in the decomposing furnace should be adjusted according to different air release amounts.
The design of the bypass air release system shall comply with the following regulations:
(1) When the content of harmful components in raw meal and clinker exceeds the provisions of Article 5. 6. of this specification, the bypass system shall be added to the firing system. The proportion of the air release from the bypass ventilation system shall be based on the type of harmful components and The content is determined;
(2) The bypass air release quenching chamber shall be provided at the location where the dust concentration is the smallest in the airflow;
(3) The temperature of the venting gas is about 1100, and should be cooled to below 450 after passing through the quenching chamber;
(4) The venting gas should be mixed with cold air and then enter the bag dust collector, and discharged after the treatment reaches the standard;
(5) The return ash received by the bag filter should be sent to the bypass blast kiln for storage and proper disposal.
The selection and arrangement of the kiln high temperature fan should meet the following requirements:
(1) The fan efficiency should be greater than 80%, the fan should be resistant to temperature, wear and abrasion; the wind volume, wind pressure and maximum temperature of the fan should be adapted to the most unfavorable working conditions of the system, and the air volume and wind pressure should be 10 % of reserve;
(2) The fan speed control should select the frequency conversion speed regulation mode;
(3) The air inlet of the fan can be equipped with a regulating valve;
(4) When the high-temperature fan is arranged in the open air, rain-proof facilities should be added to the fan transmission part.
The exhaust gas treatment system shall be designed in accordance with the following regulations:
(1) The exhaust gas discharged from the system should be used for waste heat utilization, and the exhaust gas should be discharged after cooling and dust collection;
(2) The exhaust gas treatment system should use a bag type dust collector;
(3) High temperature wind cooling measures should be sprayed with kiln tail pipe, or humidification tower, air cooler and cold air can be used;
(4) The air duct, humidification tower and dust collector of the exhaust gas treatment system shall adopt insulation measures;
(5) Exhaust gas treatment The arrangement of hot air ducts should be compact and reasonable, and should not be arranged horizontally;
(6) The ash return conveying equipment of the humidification tower and the dust collector should have a reserve capacity of 1.5 times;
(7) The ash return of the exhaust gas treatment system shall be set to the facility for feeding the raw material homogenization tank or the kiln ash silo, or directly to the kiln feeding system; the factory with the bypass venting system shall be closed to the bypass venting To return to ash, the treatment plan should be implemented at the same time;
(8) The exhaust gas chimney outlet diameter should be determined according to the chimney outlet flow rate, and the outlet flow rate can be 1Om/s~16m/s. Exhaust gas monitoring and chimney height shall comply with the relevant provisions of the current national standard “Cement Industry Air Pollutant Emission Standards” GB 4915.
The design of the rotary kiln should meet the following requirements:
(1) The specifications of the rotary kiln of the cement factory production line shall be determined according to the output of the firing system, the original, fuel conditions, altitude and preheater; decomposition furnace and chiller configuration;
(2) The ratio of the length to diameter of the rotary kiln should be 10~16, the slope of the sinus should be 3.5%~4.0%, and the maximum speed should be 4. Or/min~5.Or/min, the speed range should be 1:10;
(3) The rotary kiln shall be provided with a detection device for the simplified temperature;
(4) The main motor of the rotary kiln should adopt a stepless variable speed motor, and an auxiliary drive should be set. The auxiliary drive should be additionally equipped with a circuit connected to the factory security power supply.
The layout of the rotary kiln shall comply with the following provisions:
(1) The height of the center of the rotary kiln should be determined according to the type and arrangement of the clinker cooler; when there are more than two rotary kiln, the center distance of the two kiln should meet the layout requirements of the kiln head and kiln tail equipment;
(2) The installation dimensions of the rotary kiln shall be determined according to the cold kiln; the horizontal distance between the kiln foundations shall be determined according to the dimensions after thermal expansion; the axial thermal expansion calculation of the kiln shall be based on the center of the belt with the retaining wheel near the transmission. Expansion to both ends; the kiln foundation shall be provided with a joint walkway, and shall be connected with the kiln head platform and the kiln tail platform;
(3) The rotary kiln transmission part may not have factory buildings and special maintenance equipment, but rain protection facilities shall be provided. Insulation facilities shall be provided between the transmission part of the rotary kiln and the kiln cylinder.
The design of the cooling ventilator of the rotary kiln should meet the following requirements:
(1) Rotary kiln firing belt cylinder should be equipped with ventilation cooling system according to equipment requirements;
(2) For rotary kiln belts with air cooling and cooling requirements, an independent ventilation and cooling system shall be designed according to the required air volume and wind pressure requirements of the equipment;
(3) The air cooling of the main drive and other motors in the kiln should be designed according to the requirements of the equipment, and the filtering measures should be taken for the ventilation system.
The design of the tertiary air duct of the decomposition furnace shall comply with the following provisions:
(1) The tertiary air should be taken from the upper casing or kiln cover of the cooler;
(2) The tertiary air duct should be arranged in a slanted “one” shape, otherwise cleaning measures should be taken;
(3) The wind speed in the tertiary air duct should be 25m/s~32m/s.
The configuration of the pulverized coal burner of the firing system shall comply with the following regulations:
(1) Rotary kiln shall adopt multi-channel, low NOx burner; when incinerating alternative fuel, the type of burner shall be adapted to the nature and state of the alternative fuel;
(2) The burner shall be provided with an ignition device, and the length and angle of the burner shall be adjustable;
(3) The ratio of the primary air volume of the multi-channel pulverized coal burner to the theoretical combustion air demand should not exceed 15%, and the ratio of the primary wind to the coal supply wind and the net wind should be determined according to the burner type;
(4) The burner of the decomposition furnace should be determined according to the type of the decomposition furnace and the coal quality, and it is preferable to adopt a multi-layer multi-point arrangement and a staged combustion technique to reduce nitrogen oxides in the flue gas;
(5) The primary fan should be equipped with an accident fan or a backup fan. The kiln head platform shall be provided with equipment for hoisting refractory materials and the stacking position. The inspection and hoisting equipment shall take care of the inspection of the burner.
The configuration of the clinker basket cooler should meet the following requirements:
(1) The heat recovery rate of the basket cooler should not be lower than 72%, and the clinker temperature of the cooler should be less than the ambient temperature plus 65 ‘C;
(2) The amount of cooling water per clinker required for clinker basket cooling shall be determined according to the type of basket cooler;
(3) The residual air of the basket cooler should be fully utilized and can be used for drying or waste heat power generation of raw materials, coal and mixed materials;
(4) The centerline of the basket cooler shall be biased to the side where the material of the center line of the kiln rises;
(5) The dust collection of the residual wind of the clinker basket cooler should be carried out by a bag type dust collector, and a cooling device should be installed before the exhaust gas enters the bag type dust collector.
The above is about the relevant regulations that each part needs to follow during the clinker burning process. After the raw material is preheated and pre-decomposed in the cyclone preheater, the next process is to enter the rotary kiln for clinker firing. In the rotary kiln, the carbonate is further rapidly decomposed and a series of solid phase reactions occur to form equal minerals in the cement clinker. As the temperature of the material rises, the minerals become liquid, and the dissolved in the liquid phase reacts to form a large amount (clinker). After the clinker is fired, the temperature begins to decrease. Finally, the high temperature clinker discharged from the rotary kiln is cooled by the cement clinker cooler to the temperature that can be withstood by the downstream conveying, storage and cement machinery, and the sensible heat of the high temperature clinker is recovered, and the thermal efficiency of the system and the quality of the clinker are improved.