Lime is an indispensable and important raw material in the economy and is  widely used in metallurgy, building materials, petrochemical, environmental  protection, food and other industries. With the continuous development of the  global economy, lime production is showing an increasing trend year by year.  Lime is mostly used in steel, chemical industry, construction, building  materials, agriculture, medicine, and environmental protection. For the deep  processing industry of lime, such as the light calcium carbonate industry, its  use is more extensive, not only can be used in building materials industries  such as coatings, paints, putty powder, PVC pipes, but also in food, medicine,  daily chemicals and other industries. The development prospect is broad.

　　Lime kiln is the core equipment of lime production. Independent innovation  and development of new kiln types, new technologies, rational configuration of  lime kilns, and large-scale lime kilns are important ways for the scale and  specialization of the lime industry. Compared with other types of lime  calcinating kilns, rotary kilns have large production capacity, high product  activity, uniform and stable quality, and strong adaptability to raw materials.  The fuel ash has little pollution to the product, high degree of automation,  simple control system, easy operation, high labor productivity and simple kiln  structure, smooth air flow, sulfur-containing flue gas can be discharged in  time, and sulfur in fuel is not easy to adhere, so the product contains sulfur  It occupies a very important position due to the advantages of low quantity.

　　This paper focuses on the production process and technical characteristics  of the 5x 1000 t/d active lime rotary kiln project.

　　1. Project  scale, final products and construction scope

　　(1)  Design scale: 5 new 1000 t/d active lime rotary kilns are built,  among which 4 1000 t/d rotary kilns produce lime and 1 1000 t/d rotary kilns  produce light burned dolomite.

　　(2)  Product varieties: active lime block ash, active lime powder ash,  lightly burned white cloud stone ash. Light burned dolomite powder ash,  desulfurization powder ash.

　　(3)  the construction scope: including raw material storage system,  feeding system, calcining rotary kiln system, waste gas treatment system  (reserved denitration system), finished product storage, crushing screening  dispersed system, finished the blues pneumatic conveying system, coal  pulverizing system of desulfurizer, environmental dust removal system, water  supply and drainage system, circulating water system, PLC automatic control  system and instrument testing system, communication system, Monitoring system,  fire control system, etc.

　　2.  Design guidelines and main principles

　　(1)  Adopt mature and reliable new process and technology, so as to be technically  advanced, economical and reasonable, practical and reliable.

　　(2)  Pay attention to environmental protection, the use of efficient dust  removal facilities, so that it meets the environmental protection standards of  the location of the enterprise.

　　(3)  All dust dust recycling. In the design, the transport and drop of materials  should be reduced as far as possible, and dust collection should be divided into  different regions for all dust spots. Environmental protection standards should  be strictly implemented to achieve standard discharge.

　　(4)  In the selection of equipment, on the basis of the principle of  "reliable and practical, investment saving, advanced technology, energy saving  and consumption reduction", the specifications and models should be unified as  far as possible, in order to manage production and reduce the type and quantity  of spare parts.

　　3.  Production technology and equipment

　　3.1  Production process

　　(1)  Raw material feeding system

　　After screening by the raw material yard, the limestone and dolomite of  20~50 mm that meet the roasting requirements of the rotary kiln are transported  from the material yard to the limestone storage and dolomite storage of the lime  factory by belt conveyor respectively. The dolomite in the dolomite reservoir  and the limestone in the limestone reservoir are respectively sent to the  preheater by belt conveyor.

　　(2)  Rotary kiln roasting system

　　After entering the preheater, the limestone/dolomite is preheated by flue  gas at 1100 ℃ at the end of the kiln, and part of the limestone/dolomite is  decomposed in the preheater. The preheated material is pushed out by the  hydraulic push rod and transported into the rotary kiln through the transfer  chute. The material is roasted and decomposed in the rotary kiln, and the  roasted lime/dolomite enters the vertical cooler. After cooling by the cold air  sent from the bottom, it is discharged to the collecting hopper through the  vibration feeder, and then sent to the finished product system through the chain  hopper. The cold air is heated while cooling the material in the cooler, and  enters the kiln through the kiln hood to participate in combustion as the  secondary air of fuel combustion. The fuel used in the rotary kiln is sent to  the rotary kiln head workshop through the gas and pulverized coal pipes  respectively, and is burned in the rotary kiln from the kiln head through the  burner. The hot flue gas generated by fuel combustion is discharged from the end  of the kiln together with the waste gas generated by the decomposition of the  material after roasting and heating the material, and enters the preheater  through the transfer chute to preheat the limestone/dolomite. The flue gas after  preheating limestone/dolomite is discharged from the preheater and removed by  the dust collector and then discharged into the atmosphere by the exhaust  machine. Main technical parameters are listed in Table 1.

　　(3)  Finished product storage and transportation system

　　After cooling, the lightly burned dolomite is sent to the lightly burned  dolomite cache by the conveyor, and the vibration feeder is set at the bottom of  the cache. The material is then transported by the vibration feeder, belt  conveyor and plate and bucket elevator into the double-layer double-buck screen  for screening. Among them, sieve material (0~ 3 mm) into the light fired  dolomite powder bin; Sieve feeding (15~50 mm) into the lightly burned dolomite  stone warehouse, can also directly into the lightly burned dolomite debris  warehouse; Sieve material (3~15 mm) directly into the lightly burned dolomite  debris storage. The material in the crusher is sent to the vertical composite  crusher for crushing, and the broken light burned dolomite enters the single  layer multiple frequency screen for screening. The sieve feeding (0~ 3 mm)  directly enters the light burned dolomite powder bin, and the sieve feeding  (> 3 mm) returns to the light burned dolomite crusher.

　　After cooling, the active lime is sent to the lime cache by the conveyor.  The bottom of the cache is set with a vibrating feeder. The material is  transported by the vibrating feeder, belt conveyor and plate chain bucket  elevator into the double-layer multifrequency screen for screening. Sieve  material (0~ 3 mm) into the lime powder bin; Sieve feeding (15~50 mm) into the  lime block bin, can also directly into the lime debris bin; Sieve material (3~15  mm) can be directly into the lime powder storage, but also into the desulfurizer  powder system. The material in the crusher is sent to the vertical composite  crusher for crushing, and the crushed lime enters the single-layer  multifrequency screen for screening. The material on the screen (> 3 mm)  returns to the lime crusher, and the material off the screen (0~ 3 mm) enters  the lime powder silo.

　　(4)  desulfurizer powder making system

　　The lime that enters the desulfurizer powder making system enters the  feeding bin of the mill, and the lime in the feeding bin is sent to the grinding  system by the belt metering feeder. After grinding, qualified size of lime is  collected by cyclone and cloth bag dust collector and then enters the  desulfurizer powder silo.

　　(5)  Finished product delivery system

　　Massive activated lime and lightweight burned dolomite are transported to  steelmaking transfer station by belt conveyor. The finished product block bin is  equipped with loading device, the finished products can be transported out by  car in special circumstances. Powdery active lime, powdery light burned dolomite  and desulfurizer are delivered to sintering plant and pelletizing plant by  pneumatic conveying. The finished product powder bin is equipped with loading  device, and the finished product can be transported out by tank car in special  circumstances.

　　(6)  Schematic diagram of lime process flow and lightly burned dolomite process  flow

　　See  Figure 2 and Figure 3 for the process flow of lime and light burned  dolomite. 

　　3.2  Characteristics of production technology

　　3.2.1  the size

　　The project is divided into two phases. In the first phase, 5 × 1000 t/d  rotary kiln is constructed, and in the second phase, another 3X1 000 t/d rotary  kiln is planned, which is of milestone significance for large-scale and  large-scale lime engineering.

　　3.2.2  products more

　　The raw materials of this project are not only limestone, but also  dolomite, with complex raw materials. At the same time, the production products  include lime block ash, lime powder ash, light burned dolomite stone ash, light  burned dolomite powder ash, desulfurizer ash. The complex types of raw materials  and finished products also put forward higher requirements for the design of the  whole production line.

　　3.2.3  Multiple systems and complex layout

　　The main system of the project includes the following parts:

　　(1)  Raw material feeding system : 1 limestone warehouse,1 marble  warehouse;

　　(2)  Rotary kiln roasting system : 5 rotary kilns;

　　(3)  Finished product cache system : 2 active lime cache library and 1  lightly burned dolomite cache library;

　　(4)  Finished product screening, crushing, storage and transportation system  :1 lime debris warehouse,1 lime powder ash warehouse,1 lime block ash  warehouse,1 lightly burned dolomite debris warehouse,1 lightly burned dolomite  powder ash warehouse,1 lightly burned dolomite stone ash warehouse;

　　(5)  desulfurizer powder making system : 3 mill feeding silos,1  desulfurizer powder silo;

　　(6)  Finished product delivery system: the lime and light burned dolomite  powder are transported to the sintering plant by pneumatic conveying, and there  are loading interfaces; The block ash is transported to the transfer station at  the interface of steelmaking plant by belt conveyor, and there is a loading  interface; The desulfurizer is sent to sintering plant and pellet plant by  pneumatic conveying, and there is a loading interface;

　　(7)  Pulverized coal storage and transportation system : 3 pulverized coal  warehouses, pulverized coal and gas pipelines.

　　Kiln end area: the kiln end area is mainly the dust removal system, raw  material warehouse, comprehensive electrical room, circulating water system and  other facilities of the rotary kiln. The raw material warehouse is arranged on  the east side of the land area, close to the steel raw material yard, and the  belt connection length is shortened as far as possible. The dust removal systems  of five rotary kilns are centrally arranged at the kiln tail, and the  comprehensive electrical room is located near the facilities with large power  load.

　　Rotary kiln area: mainly includes 5 rotary kilns and kiln head factories. 5  rotary kilns are arranged side by side and connected with kiln head  factories.

　　Kiln head area: mainly including lime finished product warehouse, dolomite  finished product warehouse, pulverized coal storage and transportation system,  dust removal system and other facilities. This area is the main transportation  area of this unit and is likely to produce dust. Centralized arrangement of  finished goods warehouse and dust removal system can reduce the impact on the  lime unit office area (comprehensive electrical room).

　　To sum up, the overall layout of the factory is reasonable, convenient  management, smooth technological process, obvious functional zoning, relatively  concentrated and compact facilities, not only save land, save investment, but  also ensure safety, conducive to construction, production and maintenance.

　　3.2.4  Application of new rotary kiln technology

　　Through years of independent research and development and accumulation of  practical experience, our company has applied a large number of new rotary kiln  technology in this project, to ensure that the rotary kiln system energy saving,  environmental protection, high efficiency. The specific new technologies applied  are listed in Table 2. 

     3.2.5  Realize automatic control, monitoring and process control  functions

　　In order to ensure security and facilitate the management and monitoring of  the operation and operation of the main production equipment, camera monitoring  points are set up in the raw material feeding system, finished product caching  system, finished product screening and crushing, storage and transportation  system, finished product shipping system and other places. The network video  signal is connected to the network switch of the video surveillance system and  the corresponding video server through optical cable, and the large screen  display unit is set in the control room. Toxic gas detection and alarm system  shall be set at valve group and burner of kiln head workshop. The system  consists of gas alarm controller, toxic gas detector (carbon monoxide medium)  and sound and light alarm.

　　The process control scope includes automatic control and monitoring of the  production process of 5x1000 T/D rotary kiln system and its auxiliary  facilities. It mainly includes supporting systems such as rotary kiln, fuel  system, raw materials and finished products, dust removal of calcining system,  circulating water and external lines for dust removal of raw materials and  finished products (including kiln head and transfer station).

　　Automatic control system adopts two levels of control, basic automatic  control system (L1), to control system as the core, the overall structure of the  system to consider EIC integrated design, PLC as the control core, with data  acquisition and processing, sequence control, process control, parameter  indication. Overlimit alarm, equipment status monitoring and other functions,  constitute a reasonable function division, clear hierarchy and safe, efficient,  open automatic control system.

　　Limekiln integrated control system (L2), to the production management  system as the core, the realization of data acquisition, integration, storage  and query, through the analysis of process data and processing, using  mathematical model to calculate and make the system stable operation under the  state of the economy, optimize and reduce the intermediate operation effect, to  produce high quality products, improve labor productivity, Reduce production  cost and energy consumption.

　　4.  Conclusion

　　Lime production enterprises are numerous, but their technical equipment  level and product quality are uneven, with the increasing awareness of energy  conservation and emission reduction. In recent years,1000 t/d and above large  rotary kiln with its output, quality, energy consumption, occupation,  investment, automation control, energy conservation and emission reduction  advantages, rapidly recognized and popularized by the market, which is in line  with the development trend of large-scale and energy-saving metallurgical lime  industry, has broad application prospects. Our company's 5x1000 T/D rotary kiln  project integrates the current advanced technology in China and represents the  future development direction of lime industry. This process will make an  important contribution to the global active lime industry.