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Ask Dr ClarkThe idea of the Ask Dr Clark feature is that lots of people in the cement industry around the world periodically ask Dr Clark for his advice on issues they are currently facing. Through Ask Dr Clark anyone is able to ask Dr Clarks advice on their current issues.

Q: sir in our kiln fine genration is too much in present days. so we are facing inlet presarisation frequently ? A: I am struggling to understand. You kiln is producing fine clinker so you have a lot of dust recirculation from the cooler? That is causing over-pressure in the kiln hood? The production of fine clinker might be associated with heavy recirculation of sulphur within the kiln. Back to Top Q: Sticky Clinker How to ride off the sticky clinker, Although it is not causing snow formation but the flow of the air through kids of IKN cooler is being effected. Furthermore how to control the cooler exit temperature. Best Regards Nasir A: The "kids" of the IKN grate must be restricted. Inadequate air flow through the grate will lead to more sticky clinker on the grate and also to high cooler exhaust gas temperature. I suspect you will have to stop and clean the "kids" of the IKN grate.

Back to Top Q: method of raw mix pile avg calculation according to hourly tonnage in excel? A: This requires that the weighted average of each oxide in the pile be calculated after each new sample using the analysis of the sample and the wieght of material added to the pile. The composition to correct the pile to target can then be calculated. Back to Top Q: effect of flame shape Dear Sir, What is the effect of flame shape on the kiln outlet oxygen and carbon mono oxide. A: It is important to have good mixing of the secondary combustion air and fuel in the main burner flame. If not then it is possible that there will be CO even with kiln inlet oxygen as high as 5%. The momentum of the primary air blown through the burner pipe must be sufficient to produce a short, hot, recirculating flame. The benchmark is that the momentum should be a minimum of 10 Newtons per MW of the burner. Back to Top Q: what are the factor affecting on the process bag filter fan efficiency? sir , regarding the fan efficiency, what i under stood that by changing stack height , ,changing impeller size or modified impeller , replacing motor with drive(VFD) but not by removing fan damper pressure loss ( if there is a damper ) is it write or wrong? A: Fan efficiency itself will be affected by the impellor design. Fan performance will be affected by the other factors. Back to Top Q: Preaheter cyclone efficiency, from down to the top cyclone.. sir i know the method for calculating the top cyclone efficency of preheater but my quistion is how to estimate the efficiency of remaing cyclone , i.e from 2cy to bottom cyclone indivisually ? A: This has to be done by reference to the loss on ignition of the material in each cyclone of the preheater making the assumption that no calcination is taking place in the upper stage cyclones. Back to Top Q: so3 content in fine coal ash why so3 increases in fine coal ash as compared to raw coal ash.IN OUR PLANT KILN FEED RETURN DUST GET MIXED HOT GASES ENTERING IN COAL MILL A: Possibly there is some absorption of SO2 from the preheater exhaust onto the fine coal in the coal mill. A volatile balance of the internal and external cycles needs to be developed to fully explain this. Back to Top Q: We have the clinker with 1380 litter weight.but still free lime problem. A:

There could be lots of reasons why a hard burnt clinker would have high residual free lime: (i) lime saturation beyond 100%, (ii) heavy recirculation of sulphate, (iii) excess K2O in clinker, etc. Much more detail is required. I recommend a technical audit to understand the problem. Back to Top Q: what is the technology of raw meal injection in before bypass bag house? now in our plant we will decrease the dust to bypass so we are afraid about chlorine blockage in bags of filter so i hear that the solution is injection of raw meal with bypass gases A: How will you reduce the dust losses through the bypass? Normally that is a good thing to do, but how? I have never heard of injecting raw meal after the bypass gas has been extracted from the kiln. Back to Top Q: What is the role of V seperator in closed circuit cement mill We are having both V seperator and dynamic seperator in our closed circuited cement mill. we are thinking to remove V sep from circuit . Please let me kow the effect on though put and power consumption. A: The V-separator will be making coarse, static, separation of the material. I would need to see the layout before I could understand the importance of the V-separator. Back to Top Q: Specific Ratings requirement of various equipment Kindly let me have gas velocities in various part of kiln requiredto maintain efficient preheater,and how to calculate it. Can i calculate with qty of coal dosing & O2 at back end. A: Gas velocity in the gas risers between the preheater stages should be c.18m/s. Lower as the gas exits the kiln to the preheater to minimise recirculation of material from the kiln to the lower stage cyclone. You need to develop a and energy mass balance for each section of the kiln. You can then convert the gas masses passing through each section into volumes. By dividing the volume by the cross-sectional area of the ducts through which the gaas is passing you arrive at the velocity. Certainly the coal dosing and oxygen at the back end of the kiln (and throughout the kiln process) will be part of that mass balance. Back to Top Q: cement strength development dear sir , our cement 3&7 day comp.strength usually are high (280&350kg/cm2) but 28d is low(440kg/cm2)What could be the reason and what can we do. clinker so3-1.4 , na2o-0.6 ,k2o0.42,mgo-2,c3s-62,c2s-15,c3a-6.9,c4af-11 A: The alkalis and aprticularly the Na2O in your cement are high. It is a well known phenomena that high alkali sulphates in cement leads to higher early strengths but lower 28-day strength. Is it possible to reduce the alkalis by selective quarrying of raw materials or changes in raw mix design? Back to Top Q: Process of clinker How to produce clinker from rew meal A:

That is done by heating the raw meal to over 1400 C at which temperature the raw minerals in the raw meal are converted into the cement clinker minerals. Back to Top Q: presention for cement technology i want to presentation of cement technology A: Whitehopleman provides training programmes in many aspects of cement and cement manufacturing technology. Please indicate the location for the training and the number of people and we can send you a draft proposal. Back to Top Q: Gas cooling before PH Fan Please explain that in which places is better for gas cooling by water spraying for capacity increasing: 1-top cyclone 2-downcomer duct 3- below the feed in the upper stage riser duct? then, please explain how can i calculate needed water(lit/Nm3)? with regards A: Evaporative cooling of the preheater exhaust gas is best applied in the downcomer duct. The amount of water needed depends on the drying requirements in the raw mill and coal mill (if any). Thee amount of water can be calculated by developing a mass and energy balance of the kiln and then varying the amount of water addition. Back to Top Q: white clinker kiln with natural gas Dear Mr. Clark, During white clinker production with firing natural gas, do we need high secondary air temperature? I have checked some process firing with coal, they have heat exchangers after C1 and heat ambient air to 200-300 C. They use this hot air as secondary/tertiary air. What if we fire natural gas, will we need this heat exchanger or can we directly use ambient (cold) air as combustiona air (secondary/tertiary)? How the combustion and flame will be affected? Thank you very much A: The combustion efficiency of the natural gas will be improved with preheated secondary/tertiary air. However, ambient air could be used with some loss of efficiency. Back to Top Q: fuel residence time how to fine the fuel (coal) residence time in calciner/flash furnace A: You need to calculate two things: (i) the internal volume of the calciner from the dimensions and refractory thickness, (ii) the stoichiometric volume of the gases in the calciner. Dividing one by the other will give the gas residence time in the calciner. Back to Top Q: Alkali bypass dust Dear Dr. Clark we are thinking to send the bypass dust to the cooler , is it a good idea and if yes what is the best point in the cooler to inject the dust . knowing that the ratio of the dust to clinker is 1-1.5% and also we have no issue on the level ofalkalis in cement A:

I would suggest adding the bypass dust to the clinker conveyor away from the cooler. Back to Top

Q: crossbar cooler efficiency optimization Dr Clark, I'm about starting a project to optimize our FLS crossbar cooler. What are the necessary parameters to check, and actions are needed to take? A: You need to develop a mass and energy balance around the cooler. Then you can adjust the speed of the cross bars and the airflow through the cooler fans to explore the impact of adjustments on cooler efficiency and find the best settings. Back to Top Q: Please elaborate the causes for ball formation in kiln ? along with remedial steps to eliminate the chances of ball formation in kiln . A: Unfortunately there are multiple possible causes of clinker ball formation in the kiln. Often they are caused by recirculation phenomena in the kiln connected with the adjustment of the main burner. Without more information it is impossible to be more specific. Back to Top Q: Can alkali in clinker be reduced Wet kiln, high alkali, any way of reducing it, or is it to late once it gets to this stage. A: Some of the alkali will be passing out of the kiln in the dust. Therefore some or all of that dust could be discarded to reduce the alkali content. You could increase the amount of alkali passing out in the dust by the addition of calcium chloride. Back to Top Q: Dear Sir, what is the possible effect of ID fan draft on raw meal to clinker factor A: The draft drawn by the preheater induced draft fan can affect the kiln feed to clinker factor because the amount of dust lost from the top stage of the preheater depends on the velocity of the exhaust gas drawn out of the top stage of the preheater. Back to Top Q: Effect of Sulpher Alkali ratio Hello Dr. Clark, Ideally the value of Alkali Sulpher ratio of clinker should be as close to 1 as possible - My asking is if this value decreases (say -4) or or increases (say +4) then what's the effect of produced cement because of this abnormal value? A: The immediate problem is usually on the coating formed in the preheater, which can become very hard if the alkali:sulphur ratio is low. There will be more subtle effects on the cement quality as the amount of soluble alkalis in clinker will be changed and some alkali will be present in the clinker minerals if the alkali:sulphur ratio is high. It might become difficult to fully combine the clinker if the K2O content is high. Back to Top

Q: Ring formation Dear Dr. Clark, We are facing frequent kiln stoppages due to ring formation in 42-49m away from kiln discharge end. We are using mixture of pet coke and coal as a fuel. Clinker LSF is 95-96, SM 2.24-2.29, AM 1.5-1.6.Refractory used is in this area is high alumina brick (70%), not changed for 3 years. Fuel ash content is 11-12%. Liquid phase is 28-29% @ 1450 centigrades. Any help would be greatly appreciated. A: There could be many reasons. The chemistry of the clinker is not unusual. It is more likely a process related problem. Using a mixture of pet coke and coal as the fuel is likely to be a contributory factor. This is generally a bad practice. Back to Top Q: How we can increase output ? if kilnis wet based on wet lime sludge A: You make a major upgrade to the dry or semi-dry process or take steps to reduce the kiln feed slurry moisture content. Back to Top Q: reasons for yellow clinker being produced continously with good clinker.Solution to solve this problem. A: It is common to have yellow cores to the clinker due to high temperature reduction. Smaller clinker particle size will help to reduce these yellow cores to the clinker granules. Back to Top Q: What is the Minimum volume, Velocity of air required to convey the coal to bin and as well as to furnace. We need to convey the crushed coal to silo and also from silo extration to furnace through FK Pump so please advice the volume of air and velocity to be maintained to convey the coal. Material-Fine Pet Coke Operating Capacity-2 TPH Bulk Density -0.6 Cu M/T Max Moisture-2% Particle size-75 Micron with 2 % residue. A: The rule of thumb is that you need a minimum of 0.2kg of air per kg of fine coal. If transporting over a long distance then more. The pipework dimensions should be such to ensure an air velocity of more than 25 m/s. Back to Top Q: What the side effects if the loss of cyclone 5 is very low?Is there any effect on kiln coating and in which area? A: The danger with very low loss on ignition in the lower cyclone of the preheater is that the calcination will be completed in the preheater and then the temperature will rise quickly as the endothermic calcination reaction is no longer absorbing the energy input to the kiln. That rising temperature might lead to melt formation and clogging of the preheater. Back to Top Q: Setting time and water demand

We have one open circuit mill that we have been using for some time and the water demand and setting time has been o.k. We recently installed a new roller press (close circuit). With the same clinker and gypsum the water demand has been higher and the setting time longer.Sales dept are complaining. What can we do to shorten the setting time and water demand to what we have on the open circuit mill? A: This is a common problem when switching from open circuit grinding. There is not much that can be done as the particle size distribution of the cement willl be different. You can try adjusting the SO3 content of cement. Back to Top Q: What is the reason for kiln feed pipe blockage? Our kiln is 4 stage precalciner kiln. The average total alkali is 0.16% while average SO3 is 0.09%. The kiln feed pipe has been discovered to be blocking regularly now. can the alkali or SO3 be the reason? A: It is unlikely that the problem is caused by alkalis or sulphate. The kiln feed pipe blockages may be caused by chloride. There could also be a physical problem preventing the feed flowing freely from the pipe. Back to Top Q: Alkali bypass I newly start working in a plant, all lines are equipped with bypass system . in raw meal Cl = .03 , Na2O =0.1,K2O=.52, in Clinker Cl=.01, Na2O=.16 ,K2O=.85. we use crude oil as fuel . is it really necessary to have alkali by pass system with this chemical composition. I have already started reducing the by pass but at the same time the feed is reduced A: With that level of chloride in raw meal there is probably a need for a bypass to avoid chloride clogging of the preheater. The bypass fan provides additional drafting on the kiln which may explain why the production goes down as you close the bypass. Back to Top Q: Effect of SM and A/F ratio in raw meal on clinker grinding I would like to know the consequences of increasing/decreasing SM and A/F ratio on the raw meal in the later cement grinding. Is it possible that a high SM (around 3) increases the clinker hardness by adding silica to the clinker composition? Does a low A/F ratio (around 0,7) contributes to form dusty clinker due to the lack of cohesion/low melt viscosity, thus being unable to form big particles?. Thanks in advance A: Higher silica content of clinker might lead to harder to grind to clinker due to higher C2S content in clinker. It also depends on the lime saturation and combination degree. Low alumina modulus would not be expected to cause dustry clinker. That is more likely caused by high SO3 content due to SO3 volatilisation. That could be caused by poor combustion conditions in the kiln. Back to Top Q: Dear Sir, my question is about recarbonation. Sir, What exactly is recarbonation in cement process and where it is likely to happen. How do we know that it is happening and the effects of the same on process or production. We are having a

peculiar observation now a days in the preheater of our kiln. This kiln is having a SLC I preheater with 6 stages. Recently we installed analysers at stage 6 outlet of both the strings to see the combustion efficiency. We observed that in the Kiln ILC string the o2 level is high at K6 outlet analyser but it is reduced by almost 1% at the same string outlet where as CO formation is in traces only. Both the analysers are checked for accuracy with various methods and found working correct. We checked the stage wise o2 and CO levels and found that from 3rd/ 2nd stage onwards the o2 level goes down and before that the same is increasing from 6th stage onwards. What is the possible explanation for this. Please guide us. Regards. A: This does not sound like a recarbonation phenomena. That is where CaO that has already been calcined is carried back up the preheater with the exhaust gas and recombines with the CO2 to reform CaCO3. That releases exothermic energy and leads to elevated temperatures in the higher stages of the preheater. Your phenomena sounds as if some fuel is being carried out of the ILC calciner and burning in the upper stages of the preheater. That would consume some oxygen. Back to Top Q: How to cope with High chloride in Raw mix Sir, We are using Mines Lime stone , Bauxite , Iron Ore and about 8-12 % Sweetener for our Raw Mix, Bag house dust being added after CF Silo extraction in homogenizing bin which also a part of Kiln feed . Recently we observed High Chloride in Kiln Feed average 0.02 %( Min 0.014 to Max 0.034 ) and in Raw meal average 0.017 (Min 0.003 to Max 0.068 ) . Bag house dust is having 0.030.035 % Chloride . Calcined material , collected from lower most stage , is having 0.56 to 1.25 % Chloride . How we can get rid of this without By pass system ? . We do not have any B Bypass system installed . Does it plays a role in forming heavy coating in burning zone ( 1.0 -1.20 meter thick ). Dose it promotes poor nodulization ? A: What you describe does not sound unusual. 1.25% chloride in hot meal should not cause any preheater blockage problems. There is little you can do without a bypass. It is possible that this is causing the heavy coating the burning zone, although that would be unusual. Back to Top Q: reasons for dusty clinker production and steps to get good nodules A: Dusty clinker is caused by low viscosity and surface tension of the liquid phase in the kiln. Most commonly that arises from high SO3 content in the hot meal. That arises from heavy recirculation of SO3 in the kiln. That arises from lack of oxygen and reducing burnign conditions at some point in the kiln. You need to increase the oxygen content in the kiln and improve the combustion conditions for the fuel. Back to Top Q: with the increasing of seperator RPM why blaine not increasing A: Perhaps the separator is overloaded? Perhaps the airflow through the separator is inadequate? There could be many reasons. Back to Top Q: Cement Mill,s operation As a CCR operator, What are those important parameters to monitor before and after taking the feed

(starting operation) in cement grinding? A: The power drawn by the mill main motor. The power drawn by the elevator. The rejects return weigher. The microphone on the first chamber of the mill. The temperature and pressure profile through the milling system. Back to Top Q: changing from portland cement production into alkalie resistant cement Dear dr. what about the probable problems in changing production method from ordinary portland cement to alkalies resistant Portland cement if we add accurate needed amounts of iron oxide and silica especially if our kilns are FLS kilns with 175 m length and 5.75m d running in wet process method ? A: I preume you mean low alkali cement? and that you are replacing clay with the iron oxide and silica? if that is all you are doing then there should be no problems. The clinker may be more difficult to combine due to inhomogeneity. Why not try rejecting some of the dust from the dust filters? the alkalis should be concentrated there. Back to Top Q: What will happen to clinker C3S, C2S and C3A if SM target was increase? A: C3S and C2S will rise, C3A will reduce. Back to Top Q: Sir, Why we multiply with 2.8 to Sio2, 1.18 to Al2O3 & 0.65 to Fe2O3 in LSF formula i.e. CaO/ (2.8SiO2+1.18Al2O3+0.65Fe2O3) A: These are the coefficients in the Lea and Parker formula for the maximum combinable lime in Portland cement clinker. They are derived from the phase equilibria of the CaO-SiO2-Al2O3Fe2O3 system. Back to Top Q: what are the effects of high LOI of cement on quality? what are the effects of high LOI of cement on quality and what the reasons to control it? A: That depends on whether the high LOI is due to poor combination of the clinker or due to addition of limestone to the cement. Back to Top Q: How 5 or more components raw mix design are calculated ? it is too important for me please answer it to me A: By setting up 5 simultaneous equations with the 4 targets in the raw mix that you want to control. Then solvng those simultaneous equations. Back to Top Q: Preheater cyclone - foundation loads estimation due to blockage, full or partial material filling?

During the civil design of the preheater building, it is needed to provide the extra-ordinary live load due to material blockage in the preheater cyclones. Please advise if it is safe enough to assume the material filling in the conical part only, or it should be assumed that the material is filling the cyclone completely including the cylindrical part also? Thanks. A: For design you should assume filling completely. Back to Top Q: raw meal hail stone in ILC-Calciner Dear sir, sometime we've faced with a phenomenon in the calciner that 10 mm lumps of raw meal falling down to kiln inlet as hail, why might this be? A: There must be recirculation of gas in the calciner. You need to do computational fluid dynamics (CFD) study on the calciner. Back to Top Q: small size sticky clinker and snowman dear sir , our clinker is small size(30%-less than 3mm and 70%-5 to 15 mm) and soft sticky so that move up with kiln rotation and fall down on burner tip for this reason we have dusty clinker,snowman and damring. lsf93-95 , sm2.3-2.4 ,am1.3-1.4 ,lp27-28 ,r90-12% , hood temp 9001050c please help me for increase clinker size , decrease stick of clinker and prevention of snowman and damring formation. A: This is caused by high concentration of SO3 in hot meal. Most probably there is is lack of oxygen at some part of the kiln and reducing burning conditions. That will cause heavy recirculation of SO3. The high SO3 content of hot meal leads to low viscosity of flux and find clinker. The SO3 flux also causes snowmen in the cooler. Back to Top Q: Which is the period mentioned for Pre-Cooling of Clinker? Dear Dr.Clark, In Clinker microscopic studies, experts commenting the crystolography of Clinker on account of "Pre-Cooling". Is it the cooling takes place just after the buring zone until to the kiln discharge or until the sudden Quenching in the 1st compartment of the grate cooler? A: Pre-ccoling iss in the rotary section of the kiln before the clinker falls into the grate cooler. Back to Top Q: effect of 1.26000m3/hr of water to keep our cooler ESP temp. in control. Will it effect the 1 day strenth of the clinker. A: No, provided that the water is adequately atomised and fully evaporated to cool the cooler exhaust air. Back to Top Q: Dear Sir! What should be the refractory consumption (kg/ton clk) for white kiln? A: You would hope it would be less than 0.5kg per tonne of clinker produced. Back to Top Q: kiln speed dear sir,our kiln is 4000tpd(fls designing),diameter=4.8m,length=75m,ILC system,kiln inclination=3%,kiln filling=12.5% and according to fls instruction in feed=270tph(nominal feed), kiln speed is 4.2(to reach 12.5% kiln filling).if in this condition we run the kiln with speed 3.5 instead of 4.2 for a long time,what will be the bad consequence?in fact we want to know disadvantages of low kiln speed. A: Slow kiln speed can lead to the free lime liberated at the back of the kiln becoming stabilised and more difficult to fully combine into the clinker minerals. That then leads to the thermal energy consumption of the kiln rising and the clinker production rate falling. Back to Top Q: I am from ethiopia, in our cement factory the snowmen is within short period of time happened continously in grate cooler, what are the reason behind there? 1.Generally, in our cement factory there is so many problem but some of them are continuously snowmen formation in grate cooler or around clinker out late area for this what are the main causes for snowmen formation and methods of improving the systems etc. 2.what are the reasons for formations of more dust particles or blockages of Tertiary air duct and methods of improving A: I have been travelling to Ethiopia regularly over the last few years where I have been monitoring the construction of the Derba Midroc cement factory. Snowmen are caused by the clinker entering the cooler from the kiln continuing to have some melted phases. The only way to reduce the problem is by control of the alkali cycles within the kiln or operating with a lower secondary air temperature. Back to Top Q: lsf-92.90, sm-2.26 , am-1.30 , but kiln feed not increasing .what reason A: There could be many reasons. The kiln feed will not increase by itself. You need to respond to opportunities to increase the feed rate to the kiln. Back to Top Q: high silica modules what effct in kiln ? A: High silica modulus of kiln feed will render the kiln feed more difficult to combine. Therefore the

thermal energy consumption of the kiln is likely to rise and the clinker production rate may decrease. Back to Top Q: How to get Excel based model of the alkali cycles, that your demonstrated at Cemtech in Dubai and Jakarta? Dear Dr.Clark, Could you please guide me to get the Excel based model of the alkali cycles, that you demonstrated at Cemtech in Dubai and Jakarta? A: The only way to gain access to Whitehopleman's Excel based model of the alkali cycles in cement kilns is to retain Whitehopleman as your technical consultants. Back to Top Q: low liter weight clinker and decrease product LSF X- RAY : 90-92 SIM : 2.3-2.4 ALM :1.3-1.4 LSF CHEMICAL :88-90 SIM :2.4 ALM 1.3 A: Well, it seems that you X-ray is reading high on CaO, if the chemical analyses are correct. That does not explain the decreased productivity. My suspicion that there is some other problem. Back to Top Q: How to calcualate or simulate the alkali enrichment in the preheater when alkali rich material is used as additive? I am substituting Trass for Sand to get silica in the raw mix. The trass contains 1.2% K2O and 3.2% Na2O. Consequently, the total alkalies in the raw meal inceases from 0.34 % to 0.56%. How calculate or simulate the alkali enrichment in the preheater circulation material? A: It is of course possible to do this with an Excel based model of the alkali cycles, as I demonstrated at Cemtech in Dubai and Jakarta. However, it is not just a question of calculating. That depends on yhe volatility of the Na2O and K2O, which is dependent on the amount of chloride and sulphate present. It is too complicated for a simple calculation and depends on a model. However at 0.56% total alkali there should be no problems. Back to Top Q: kiln speed dear sir,kiln feed is 275tph(nominal capacity)and kiln speed is 3.6 rpm .speed is at least 0.5 rpm less than required speed for the feed.if we run the kiln in this situation(kiln low speed),what will be the bad consequence ? A: How do you calculate the required kiln speed? 3.6 rpm sounds OK without knowing more about the kiln. I can't imagine any bad consequences (although I am normally in favour of high kiln speed). Back to Top Q: Slag Cement Vs Portland cement Dear sir, Please explaine me that, Why there is higher limit(Aprox 10%) of MgO in Slag Cement, while in Ordinary Portland Cement MgO limit is 6% only. A: I have never heard of that difference in the MgO specifications for OPC and slag cement. I presume it is because the slag contains more MgO and that MgO is combined in a mineral with silicate rather

than being present as free MgO (periclase). Back to Top Q: Dear Dr. Clark, My question is about the pneumatic conveying of coal through FK pumps The FK pumps for coal conveying is provided with nozzles through which the blower air is entering. My question is for a stand by system (Common for kiln and calciner) where we have two different volume requirements. The volume of transport air for kiln is dropping by around 40% due to change of kiln burner. If we keep the same FK pump with reduced volume what problems are expected and what is the remedial action. A: Your standby FK pump must have sufficient volume for the larger of the two coal transport requirements (probably the calciner). Too much volume and hence velocity is no problem. Too small volume and hence velocity can lead to drop out of the fine coal and pulsing of the fine coal to the burner - a very bad situation making the kiln uncontrollable. Back to Top Q: Replacement of kiln shell cooling blowers (quantity wise) Dear Sir, I am trying for energy saving project in which 24 blowers of 3 KW each(=72kw)are used for kiln shell cooling. I want to replace this 24 blowers with 4(12-15KW)high speed blowers each with header(pipe)and 6 outlet from each header. Motor used may be with FPR blades and/or air foil bearings.So, i want to know want points should i consider in its design A: How will you control the airflow through the different outlets of the manifold? With individual fans you can just run the fans where the kiln shell needs be cooled. With your proposed arrangements you will lose the ability to cool a particular part of the kiln shell. Back to Top Q: CKD Dear sir.some days before i had asked a question about cement klin dust and its impact on clinkarization if it is fed to kiln in un-blended form.please answer my question. A: Where will you feed it to the kiln? From where in the kiln does the dust come from? The exhaust gas dust filter? Or the bypass? If from the exhaust gas filter, but fed continuously with feed from the homogenisation silo then there should be no problem. Back to Top Q: what is LSF, SM , AM & what effect in raw mix A: See my answer a few Ask Dr Clark's ago for what they are. The higher the LSF and SM the more dificult to combine the clinker, so the higher the fuel consumption. But the clinker quality will be better up to 100% lSF. Back to Top Q: kiln heating-up time after brick repairs dear sir,after a repairs for lining(replacing old bricks in the zone 30-50 m from kiln outlet)if we want to increase heating up time from 24 hours to 72 hours,what will be the bad consequence? A: There will be no bad consequences from increasing the heating up time, other than lost output from

the kiln. Back to Top Q: making decide to replace or maintain old brick in coating area dear sir,during repairs time in kiln we have problem in making decide to replace old brick that is under coating in the length of 6-25 meters from kiln outlet. in this area,brick is covered by coating and if we want to be sure about old brick thickness or its condition to maintain or replace it ,we should separate the coating from brick and then measuring old brick thickness or drill a lot of points to get brick thickness that is very hard and dangerous to do. what is better way to do ? A: If you remove the coating them almost certainly you will have to replace the brick. It all depends what the shell temperatures are when the kiln is operating. If below 400C then no need to replace. Back to Top Q: what is LSF meanings . A: Lime saturation factor is the %CaO relative to the maximum %CaO that can be combined with the %SiO2, %Al2O3 and %Fe2O3 multiplies by their respective coefficients, Back to Top Q: what is silica modules & alumina modules give me defination. A: Silica modulus is the ration of the %silica to the sum of the %alumin and %iron oxide. Alumina modulus is the ration of the %alumina to %iron oxide. Back to Top Q: Dryer unit effect on kiln shell temperature I Want to install a dryer unit under the kiln shell in burning zone area for reducing the moisture of RDF whcih is 40% to 50%. Is this dryer unit have any effective on kiln coating in burning zone. What is your opinion. A: It should make no difference, provided it is not so close that the radiation of heat from the shell is impaired. The smell might be bad. Back to Top Q: Dear sir by Question is regarding Cement kiln Dust What about it? There are many types of cement kiln dust? What do you want to knoe? A: Back to Top Q: Dear Dr. Clark my question belongs to ring formation in the kiln I have a 4.75x75 m kiln producing 7600-8000 tpd clinker. i am using 90% pet coke in the kiln firing. The SO3 levels measured in the bottom cyclones is below 1.5 %. We are facing the ring formation between 50-54 m from kiln discharge. This creates a lot of nuisance and material starts falling from kiln inlet forcing us to reduce th feed rate. We try the remedial action like adjusting the burner (Insertion and retraction, feeding silica sand from kiln inlet, increasing the silica modulus in the kiln feed etc. but we loose heavily on production. We have a AM of around 1.65 to 1.7 and SM

around 2.12-2.16 and lsf around 1 in kiln feed. Our limestone is rich in Alumina aroud 3.85-3.9 % so inherently the alumina is high in the kiln feed. What is the remedy for this. We have this problem once in 2-3 months. We came to know through some people that feeding caustic soda with masonary sand in 1:5 ratio through kiln inlet will help removing the ring. Do you feel this will help. Please help me. Pls let me know if u need any further data. Regards. A: Yes, rings that far back from the discharge of the kiln are very problematic. I have never heard of the addition of caustic soda with masonry sand to combat kiln rings. I doubt that this will help. More information is needed. Is the material in the ring high in sulphate? The SO3 in the bottom cyclones is no problem but it is possible that sulphate spurrite is causing the problem at the 50-54m zone. The excess air in the kiln and the momentum of the main burner will affect sulphur volatility in the kiln. The refractory lining also has to be taken into consideration. Is there any change in the tryp of refractories or the length of time the refractories have been in service in this zone of the kiln? Back to Top Q: Cement is not setting Hi, Dr. Clark, we always 'the cement is not setting' comment from our clients. In our lab process the setting time shows 100 minutes initial setting time by the addition of 3% gypsum. Let me know how to control the cement setting time and what are the factors involved in the setting time other than gypsum. A: Hmmm. That is a difficult one. You have an initial setting time of 100 minutes using the Vicat needle penetration test? In that case there should be no problem unless the temperature is very low. Which country are you in? Back to Top Q: Reducing condition in kiln What is reducing condition in the kiln during clinker burning and what is oxidizing condition? How can this condition give impact on ring formation? A: Reducing conditions in the kiln are caused by there not being sufficient oxygen, or combustion air, to burn the fuel in the kiln or precalciner. The clinker minerals are all oxides and the cement kiln should be burnt under oxidising conditions, i.e. with an small excess of combustion air and oxygen. If there are reducing conditions then the volatility of sulphates in the kiln is increased and this can lead to ring formation and other operational problems. Back to Top Q: my guestion i need some data for how to save energy consumption on cement industry which taken hot gases from PH +cooler and by -pass to generated power about 4-16 MW A: There are many ways to save energy in cement manufacturing. The first step is undertake an energy audit to assess the current situation and identify the opportunities for savings. Generating electrical energy from the waste heat flow from the kiln could be one of the opportunities identified by such an energy audit. Back to Top Q: what is the throughput in a ball mill if i feeding say 170tph

what is the throughput in a ball mill if i feeding say 170tph A: The output of a ball mill equals the feeding rate. We cannot create mass in a ball mill (or any other process). So conservation mass means that what goes in must come out. Back to Top Q: sir kiln burning temp. 1450 but free lime free lime frequently comin what reason A: There could be many reasons. Perhaps the lime saturation of the clinker is more than 100%. Perhaps there is breakdown of CaSO4 to CaO and SO2 in the burning zone. Perhaps there is variable granulometry of the kiln feed. Perhaps there is variable ash content of the fuel used to fire the kiln. Perhaps the 1450C burning zone temperature is inaccurate. Back to Top Q: kiln feed to clinker factor & raw mill to kiln feed factor give me process A: The raw meal to clinker factor is given by 1/(1- Loss on ignition at 1000C). The kiln feed to clinker factor is this raw meal to clinker to factor plus the dust losses from the top of the preheater, with appropriate adjustment for the incorporation of the ash from the fuel used to fire the kiln into the clinker. Back to Top Q: Sulphur-to-alkali ratio Hi Dr. What is the normal used formula for sulphur-to-alkali ratio and what is its preferred control range and why? A: (K2O/94 + Na2O/62 - Cl/71)/(SO3/80). Ideally the value should be as close to 1 as possible, i.e. the alkalis and sulphate should be in molar balance. That means the alkali will be present as sulphates. There will not be excess sulphate present as calcium sulphate and there will not be excess alkalis which can inhibit combination of the clinker. Back to Top Q: free CaO Dear Dr. Clark is there an estimate of 1% free CaO increase in clinker on its calorific consumption (kcal/kg of clinker)? A: I don't think there is a direct method of calculating that. FL Smidth's method of calculatng the heat of formation of clinker could perhaps be adapted to give an estimate. Back to Top Q: kiln feed What are the targets for kiln feed MA,MS and LPH A: That depends on the clinker composition you want to manufacture, the fuels used to fire the kiln and their ash content. It is part of the process of raw mix design. Back to Top

Q: white cement like grey cement can we install tretiary air duct from kiln to preheater as in white cement kiln hood gets always posative. A: Due to the clinker being quenched in water as it falls from a white cement kiln it is difficult to preheat the combustion air for firing the fuels in the kiln by recovering thermal energy from the clinker. Therefore a tertiary air duct is not normally provided and ambient air preheated through heat exchangers is used to provide the combustion air for the precalciner. Back to Top Q: Environmental Bench Marking Dear Dr.Clark How are you? This is prasad pamarthi from Qassim Cement Co, Saudi Arabia, I am preparing a presentation on Best Practices in Environment, I need your assistance on the following information being in practice in Europe, US and other countries.Any additional inputs form you are very well, and ofcourse adds value to me.Best regards 1. What is the annual / daily average (Particulates) dust emissions in Kilns in milligrams /Normal cu.mtr 2. What is the annual / daily average (Particulates) dust emissions in Mills in milligrams /Normal cu.mtr 3. Fugitive dust emissions generated in Quarry. How they are controlled??? 4. Gaseous emissions like SO2 , Nox and CO2 are they addressed?? If so how?? 5. Total Energy spent Kwh / ton of cement 6. Total Fuel spent . Kcal / Kg of clinker. A: I'm fine, thank you Prasad. Best practice for particulates emissions would be