I want to make a complete evaluation of the cement lines in my plant by doing a mass and heat balance, how do recommend for me to do and how to start, I'm still new in the field and don't have much experience.

Your idea is a good one to understand the process and construct the mass and heat balances. First you need to measure every flow into and out of the process. The raw feed and fuel should be metered and therefore easy. The dust loss from the top of the preheater is more difficult and requires that you use dilution techniques. The preheater exhaust gas flow is comprised of the combustion products from the fuel, plus the CO₂ from calcination of the limestone, plus the excess air drawn into the kiln. Hopefully the air flow into cooler grate is measured, you can estimate the excess air from the changing oxygen contents through the process. The excess of the cooler air over the combustion and excess air is then the cooler exhaust. It is always worth cross-checking this by measuring the flow of the cooler exhaust. Having balanced the mass flow in this way you then need to calculate the energy flow associated with each of these mass flows and also the energy loss through the shell of the preheater, kiln and cooler. The difference in the balance is then the heat of clinker formation which will be in the order of 1700 kJ/kg clinker.

I wish to know if the test of consistency of cement pastes has any significance as regards the quality of cement, eg a cement of lower consistency (<25 per cent) is better than a cement of higher consistency (> 25 per cent water).
Secondly: it is observed that most of international cement standards set limits only to mortar compressive strengths although in practice the main usage of cement is in concrete applications. May I know why is that?

To calculate the velocity of the gases at the mill fan inlet you need the static pressure in addition to the dynamic pressure. If the mill fan has a capacity of 133 m3/s then you need to divide this by the cross-sectional area of the inlet ducting to arrive at the design gas velocity of the fan.

We are producing slag cement with VRM technology (500tpd). Our cement setting time is coming down at the time of dam ring height reduced. Setting time is increased when the dam ring height was increased. Both above cases percentage of gypsum is same. Please explain why it is happening.

We have received some suggestions regarding the possible effects of dam ring height from a major cement plant in North America as follows:
"I would suggest that the particle size distribution (PSD) be looked at for both instances. We have found that by changing internal settings in a VRM there are physical changes in the PSD which will impact the performance of the slag. By changing the PSD as little as 2 microns there is a significant change in the performance while not showing up in a simple test of Blaine." "If the dam ring height is increased the clinker and gypsum will stay on the grinding table longer and possibly be better ground when it exits the table and therefore the circulating load in the mill should be lower.
So the two things to look at are the amount of dehydration of the gypsum with lower dam ring height compared to the higher dam ring height and also the particle size distribution of the finished cement. With a lower dam ring there is the chance that there is more over grinding and a higher concentration of superfines."
Please let us know if you find there is a relationship between dam ring height and particle size distribution or gypsum dehydration as this would make an interesting case study for publication.

I want to know what is Roslin Ramler slope and characteristic value forcements? Do they have any relationships and how do you understand the fineness by using them.

The Rosin-Rammler-Sperling-Bennett particle size distribution for cement is found by measuring the residue on various sieves (25,32,45,63,90 micronsetc.) Alternatively you can use laser granulometry or some other method of measuring the residues. You then plot the natural log of the sieve sizes on the x axis (ln(sieve)), against the double natural log of 100 divided by the residue on the y axis (ln(ln(100/Residue))). The reason for using these axes is that for fine powders such as cement the plot approximates to a straight line. The slope of the line gives a measure of the "tightness" of the particle size distribution and varies from 0.8 to 1.1 for cements, dependent on the type of equipment used for grinding. The characteristic grain size is the sieve size where 36.8 per cent of the cement would be retained. This can be calculated from the slope and intercept of the RRSB line and is typically between 20 and 30 microns for cement.

We are currently using blast furnace slag as the only additive to our new product of masonry cement but we are failing to control the compressive strengths within the desired levels. We are getting on average 26MPa at seven days and we are add in 70 per cent slag. What’s the way forward and please tell me more about masonry cement as this a new area for me.

Masonry cement is usually made with Portland Cement clinker, gypsum, up to 30 per cent limestone addition and organic additives such as lignosulphonates to increase the workability of the mortar produced with the cement. High strength is not the property that is important with masonry cement. More important is high workability and adhesion to allow the mortar to bind masonry together or to be rendered onto the surface of masonry.

We are analysing particle size distribution of raw meal, coal mill product and cement mill product through CELAS PSA having facility to determine 0.7to 400 micron.
Q1. what is the best particle distribution (on various micron sizes) of raw mill in terms of best mill performance, burnability and kiln performance and which plant in the world is producing?
Q2. what is the best particle distribution( on various micron sizes) of coal mill in terms of best mill & kiln performance? Our coal ash is 28. Q3. what is the best particle distribution( on various micron sizes)of cement mill product to have optimum power consumption, best strength &good performance in concrete.

There is no straight-forward answer to your questions. For raw mix the optimum particle size distribution depends on the mineral composition of your raw materials. If you have a high content of quartz then you must have a very tight fine particle size distribution with low content of oversize particles where the quartz will concentrate. On the other hand with a homogenous raw mix with no quartz it is not beneficial to have too small a particle size distribution as this will increase the dust losses from the top stage of the preheater. Similarly with coal there is no hard and fast rule. It is said that the 90 micron residue should not be more than 50 per cent of the volatile content of the coal. Increasing the fineness beyond that is counter-productive. For cement the optimum particle size distribution depends on the cement performance characteristics that your customers have come to expect. Ring formation is caused by the formation of liquids in the kiln at a particular position. These penetrate the refractory lining and cause a localised thickening of the coating. Fe2O3 can be a cause of these problems and I am not surprised that raising the alumina modulus has solved the problem. Many cement factories operate with higher alumina modulus than1.7 and I would recommend keeping the kiln feed mix design with the higher alumina modulus. A snowman is the formation of a large build-up on the first grate of the cooler where the clinker falls from the kiln rather than a build-up in the kiln.

We at our plant intend to utilise high sulphate resistant cement for oil well cement. To produce low viscosity and slow-setting slurry we need to know the type of most suitable retarder and friction reducing additive to be used with SRC.

The key to producing oil well cement lies in the testing and meeting of the API performance specification. A high sulphate resisting cement with low C₃A content may well be a good starting point. Lignosulphonate is likely to be a useful retarder and friction reducing agent for this application.

It is known in all cement standards that the Initial Setting Time is 45 minutes minimum and the Final Setting Time is 10 hours maximum. Is there any definite time to be considered between end of initial setting and start offinal setting to ensure cement quality and workability.