This paper introduces the technical development status of mechanized lime shaft kiln with mixed fuel in 2017 and proposes improving measures for the key technical problems,and proposes reflection and prospect for technical development and investment.
With the increasing diversification market demand, many kinds of products should be produced to meet the demand,and this is a focus of enterprise competition in the future.Our company takes the advantage of technology of the rotary kiln and manages seriously to obtain stable and high yield in multi-variety production process.
Based on current situation of beam lime kiln,this paper introduces the kiln structure configuration and roasting process,and analyzes the advantages and disadvantages of the beam kiln,which has significance for the customers with the requirements of low investment,small land occupation and undemanding lime quality.
For the reason of optimizing steel production capacity in China,as a lime production base for Xuan steel company,our company will produce higher quality lime for expanding export market. In this paper,burning experiments for producing calcium carbide with industrial form coke are carried out in new mechanized shaft kilns,and point out that using industrial form coke to produce higher quality lime.
In this paper，the effect of heat-resistant steel fiber (1%,1.5%,2%,2.5%,3%,3.5% respectively) on the properties of high purity corundum castable refractories were studied.The results show that when the heat-resistant steel fiber content is 2.5%，after low，medium and high temperature treatment，the high purity corundum castable refractories had higher volume density，suitable linear change,higher flexural strength and compressive strength.After 5 cycles of thermal shock by water cooling at 1 100℃，the residual crushing strength and residual compressive strength is still higher，with satisfactory thermal shock resistance is better.
This paper described the application of magnesia-carbon brick MT-14A in 65T GOR converter bottom and analyzed the sample bricks at the bottom of shorter service life.The results showed that the longest furnace life using 1 000mm-long magnesia-carbon brick MT-14A is 62 times and the average life is 50 times, and that using 800mm-long magnesia-carbon brick MT-14A is 41 times and the average life is less than 30 times.It’s also found that the magnesia-carbon brick MT-14A got fractured in service and proved not a suitable material to be employed in GOR converter bottom since the damage mechanism of MT-14A is melting loss of fused-magnesite and decar-bonization in working surface.
Low aluminum mullite brick was prepared with low aluminum mullite and high-voltage insulator waste as raw materials,quartz powder as additive and pulp waste liquid as binder.The above-mentioned materials were mixed in proper particle size distribution,formed under high pressure,dried and fired at 1 400℃.In the paper,the performances of this new type bricks were compared with normal silica mullite bricks and the effects of the high-voltage insulators waste addition amount on the properties of sintered samples were investigated.The results showed that low aluminum mullite brick has excellent alkali resistant and low thermal conductivity,which is appropriate for the preheating and calcining zone of cement rotary kiln.Meanwhile,the production of the bricks has practical significance for rational utilization of resource as recycling high-voltage insulator waste as raw material.
This paper introduces the process technical features of the active lime production lines of four 400m3 mechanical shaft kilns and the trials and application results of calcination for lime stone with small particle size.
This paper studies the physical and chemical performances of the dolomite ore and introduces the production processes of four dolomite products burnt at different temperatures, and expands the application domain as well.
When using pulverized coal as fuel in lime calcination,the pulverized coal distribution is crucial to lime quality and temperature distribution of the double-shaft kiln.And for Maerz kiln and CIM kiln,the pulverized coal distribution principles are quite different.Some points for attention are put forword in this paper for each pulverized coal distribution design by the theoretical calculations on two kinds of double-shaft kilns.
Based on engineering examples,this paper introduces the technology of coal powder or mixture fuel of coal and gas as the fuel for lime rotary kiln when coke oven gas is in short supply.
Calcium lignosulphonate is used as bonding agent in the production process of silicon nitride bonded silicon carbide.The pores provide favorable conditions for nitridation firing which are formed by calcium lignosulphonate ignition loss in nitridation firing process.Calcium lignosulphonate is now added in the forms of liquid and powder.This paper studies the effects of the two forms on the performance of silicon nitride bonded silicon carbide products, and the result shows that calcium lignosulphonate added in liquid is better than in powder.
The zirconia sizing nozzle was prepared by using raw materials of monoclinic zirconia sized 0.044mm & 0.002 6mm and partially stabilized fused zirconia as well as superfine secondary stability sized 0.149mm & 0.074mm mixed with Y2O3 and CeO2 composite rare earth additives，which was molded by 200t hydraulic machine under the pressure of 13MPa and sintered at 1 700℃.The results show that by adding 0.3% Y2O3 and 0.3% CeO2 composite rare earth additives and 15% superfine secondary stability zirconia，the product properties have some improvements，such as decreased apparent porosity，significantly increased bulk density and better thermal shock resistance.
Take a 180t·d-1 converter for example,this paper introduced operating conditions and common masonry method of refractories for different parts of converter,which had guiding significant for other converters.
This paper introduced the investigation of the major repair of a large sintering plant and the sample analysis to discuss the cause of lining damage.The conclusions are as follows: the sintered mixture contacts with the furnace lining at high temperature and sticks to the furnace wall and forms hanging slag; the slag gets into the refractory lining through pores and cracks,the main component of iron oxide gradually diffuses and reacts with the refractories,which result in deterioration,erosion until cracking and falling off.
By XRD and SEM analysis on hercynites from different manufactures and hercynites from different batches of the same manufacture,as well as the ceylonite bricks produced with the above materials,it is found that a lot of β-Al2O3 and impurity phases exist in materials when hercynite fuses insufficiently,and they violently react with magnesia leading to cracking of the ceylonite brick influenced by external factors fluctuate,and the fully fused hercynite has a relative strong adaptability for firing.
This paper introduces the crystal structure,properties,chemical composition and mineral composition of dolomite,and its physical and chemical changes of in sintering as well as the production process of high quality dead burned high-calcium magnesite.
To meet the client’s requirements and maintain stable production,this paper introduces the modification of production process and production layout of the existing kilns,which is based on the calcination process condition of domestic gas combustion kiln.Using qualified light-burnt dolomite powder in calcination not only reduces the production cost,but also avoids suspend of gas combustion kiln.
Comparing with traditional drawing method，the new method draws line-style masonry figure of the ladle bottom with function of filling in custom patterns,which shortening the design time and increasing work efficiency and correct rate.
This paper analyzes the effects of unsintered and over sintered lime on energy consumption of calcium carbide industry,and demonstrates the comparative studies with living examples. The application of rotary active lime technology in calcium carbide industry can not only reduce the consumption of calcium carbide production,but also economize on energy source and improve the resources utilization efficiency by using the tail gas of calcium carbide furnace and semi-coke fly ash,which are produced in calcium carbide production process.
In the lime production process of vertical preheater—rotary kiln—vertical cooler,the preheater is an important equipment of rotary kiln production line and the preheating effectiveness is particularly important to the output and quality of the production line.Currently, there are two kinds of preheaters in the market,one is stepped preheating chamber preheater,the other is compartment preheater.This paper analyzes the structures,preheating principles and preheating effectiveness of both preheaters.
An automation renovation of production process was done in lime shaft kiln.The renovation improved the production process and increased the efficiency by downsizing staff and achieved the purposes of energy saving and green production.
Taking fume gas waste heat recovery based power generation engineering of the two 600t·d-1 lime rotary kilns for example，the ORC power generation technology for fume gas waste heat of the lime kiln is designed and developed，and the design of power generation system for organic working medium in kiln tail fume gas and its economic benefit are introduced and analyzed.This technology not only contributes to energy saving and pollutants reducing，but also brings economic benefit and social benefit.
Low porosity mullite bricks are prepared by mullite homogenized matericals，andalusite and α-alumina powder as main raw materials，adding with different proportions mullite homogenized matericals.It is found that this brick has the characters of low porosity，high cold crushing strength and good thermal shock resistance.Slag resistance of the low porosity mullite birck is studied by static crucible method compared with common high alumina brick and corundum-mullite brick，it is found that this brick has better slag resistance and apply to transition zone of laterite nickel ore rotary kiln.
The quality fluctuation of 3# Maerz kiln is analyzed.The problems such as gas valve blockage,gas ring pipe blockage,low calorific value of the gas,water leakage on gas booster is sovled,and finally the quality stability of Maerz kiln is improved.
This paper simply introduces the current status of the coke ovens，diagnosis and repair technology，coke oven refractories and suitable materials in coke dry quenching（CDQ）in Japan，and describes their property and application in detail.
The particle size of silicon powder has important effect on the performance of silicon nitride bonded silicon carbide.With the same silica total amount,the effects of the ratios of silicon powder with particle sizes of 400 mesh and 200 mesh on Si3N4-SiC physical performance,silicon nitride content and silicon nitride morphology of the fracture are studied in this paper.The results show that the samples with the ratio of 1∶1 has the best comprehensive properties.
Energy saving lime shaft kiln has been widely used with poor production condition.The old control system is modified by the advanced and mature PLC automation control technology.The modified new system runs steadily,it meets the requirements of production process,reaches the goals of cost decreasing,gains considerable economic benefit for the company.
Unburnt bricks are widely used in furnace lining of active lime rotary kiln,because of their advantages of low cost and no chromium pollution.In the burning zone of active lime rotary kilns of WISCO,phosphate bonded bricks take the place of magnesite\|chrome bricks and magnesia spinel bricks,which extends the lining life to more than three years.With many years applied experiences for unburnt bricks,and based on collection and compilation and analysis on the industry data,WISCO is responsible for setting industry standards and specifications for unburnt bricks in active lime rotary kilns to guarantee the stable operation of lime rotary kiln.
This paper introduces the RH impregnated snorkel castable, which is prepared with high-purity calcium aluminate cement as binder，active α-Al2O3 micro fine as additive and fused corundum as aggregate.It also studies the effects of the ratios for different kinds of corundum and addition of spinel on thermal shock resistance and erosion resistance.
Aim at the ringing problems of lime rotary kiln with pulverized coal as fuel，this paper analyzes the ringing causes by experiments and introduces the improvement measures,which achieving remarkable effects.
Al2O3-SiC-C castables were prepared with brown corundum as aggregate and fines (67%),SiC and pitch spheres (20% in total),active α-Al2O3 and silica fume (10% in total) as main raw materials.The effects of silica fume addition,the dispersing agents (sodium hexametaphosphate and sodium tripolyphosphate) and the types and additions of explosion-proof fibers on spalling resistance were tested respectively.The results showed that different construction thickness (weight) corresponded to different spalling resistance temperatures,the thicker the construction,the worse the permeability and the spalling resistance; in the tests,the increasing of silica fume was disadvantageous to spalling resistance,whereas the increasing of water did not have obvious influence on spalling resistance; the increasing of fibers or choosing low melting point fibers could greatly improve the spalling resistance of the castables.
Purging plugs play an important role in molten refining process.As the refractory products, purging plugs can wear out during use,which will affect production and even cause breakout accident when they badly wear out.Based on the work environment of purging plug in refining ladle,causes of purging plug break out are analyzed and effective measures for improvement are proposed.
Rotary kiln is widely used for burning metallurgical lime and cement in China，and a mass of high temperature flue gas will be produced，resulting in heat loss.Our company applies superconducting heat transfer device in rotary kiln after thermal calculations.It has brought high economic benefits after putting into operation，responded to the government order of energy conservation and emission reduction and gotten positive social effects.
Etching of silicon nitride thin films is one of the key technologies for manufacturing microelectronic devices.The etching effect directly influences the performance of electronic components.The silicon nitride film is etched with reactive ion etching method, then the etched silicon nitride film is analyzed with atomic force microscope (AFM),optical microscope (OM) and surface profilometer characterization method.The results show that when the ratio reaction gases is NH3∶SiH4=40∶10,the thickness of the prepared silicon nitride film is uniform,so do the colors;the optimum etching time is 3 minutes,at this time the surface of the silicon nitride film is relatively smooth,and the boundary between the silicon nitride film and the Si substrate surface is distinct.
With development of continuous casting and secondary refining,the out-of-furnace refining treatments mainly proceed in steel ladle.The refractories for ladle lining are easy to constructed and have excellent metallurgical effects.MgO-CaO refractories can meet the above-mentioned requirements,and they are beneficial for clean steel production,but the applications for MgO-CaO refractories are limited by the hydration characteristics.The high quality MgO-CaO refractories fill the blank of ultra-high temperature researches especially above 1 900℃.
This paper introduces the development of the refractories for connecting crossover tunnel in double-D kiln and the main problems in use,and proposes improvement measures.The magnesia bricks for connecting crossover channel were replaced by high quality alumina bricks.With these improvements,the service life of the double-D kiln increased,and refractories didn’t peel off in the last four and a half years.
There is some big differences between quicklime for glass fiber production and metallurgical lime in qualities and performance requirements.This paper introduces the requirements and control measures of composition,partical sizes,transportation and storage of quicklime for glass fiber.
This paper analyzed the status of lime production in china and stated the technology ideas and advantages of lime powder suspended calcining process.It pointed out that the heat exchange rate is high when preheating,decomposing and cooling in suspension state;calcium carbonate powder decompose with high rate and high degree; suspension calcinator with uniform and controlled temperature can improve products quality stability.This process increased high quality resource utilization rate,because lime stone with different sizes can be milled into powder as raw material.
By-products from different locations of the lime production lines were collected and analyzed.The absorbent suitable for LJS sintering fume dry desulfurization was prepared by compound method using different kinds of by-product samples.According to the characterization of TGA,BET,XRF,etc.,the compound of 90% screening by-product and 10% suspension kiln by-product was qualified to be used as absorbent for sintering fume.The analysis results showed that absorbent prepared from the above mentioned compound contains more than 60% Ca(OH)2,the BET surface above 19m2·g-1 and D50 below 45μm,Fe2O3 is below 0.2%,Cl is below 0.007%,with little risk for the equipment corrosion and erosion.Using by-products from lime kiln for sintering fume cleaning in the same iron and steel plant is technically feasible with good economy.
This paper described the process and affecting factors of pulverized coal combustion in details and emphasized that pulverized coal combustion plays a dominant role in rotary kiln production from perspective of coal properties,pulverization process,four channel burner principle and oxygen-enriched combustion,etc.
A chemical treatment for recovery dust and gravel is proposed through experiments.In the method, the recovery dust and gravel are dissolved by acid hydrolysis, the insoluble materials are filtered, the impurities such as iron, aluminum and heavy metal are precipitated and the light calcium carbonate with high purity and high brightness is obtained by carbonization method.In addition, high purity calcium oxide and calcium hydroxide are obtained by calcination and digestion, which can be applied in high purity products required for fine chemical, environmental protection, pharmaceutical and electronic industries.
ISSN 1673-7792 CN 21-1544/TQ Sponsor:ACRE Coking & Refractory Engineering Consulting Corporation,MCC Postal Code:8-29
