1156 posts
Burning Question 89
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.
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1156 posts
Re: Burning
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.
1156 posts
Burning Question 90
We are running for the last one year with a rapid build up at mix chamber, kiln housing and stage 4 riser and countering it with continuous manual cleaning. All the problems are due to the use of high sulphur coal at kiln head and at PC. But we never experience the build ups in PC vessel. For the last 20 days we experiencing this new strange problem. Here I would like to point out that at stage 3 feed pipe has a double pendulum flap valve one of which is stuck in open condition for 2-3 weeks, through which feed enters in to the PC and discharge of PC goes to the mix chamber. Because this flapper is stuck, short circuiting of air is expected. My question is that beside over-sulphatisation, could this short circuiting of air contribute to build-up in the PC. Furthermore our quality chief has an opinion that over burning/high litreweight is also an important factor for increasing the sulphur cycle as some of sulphates break down into SO2/SO3 and CaO/Na2O/K2O and sulphur starts recycling. What is your opinion?
1156 posts
Re: Burning
Possibly the feed flap from stage 3 being stuck open is causing short-circuiting of gases from the calciner and the disturbance in the gas flow through the calciner is the cause of the build-ups. Over-burning will increase the volatility of the sulphates and therefore contribute to a heavier alkali cycle and increased build-ups. However the combustion conditions are a much more important factor. If there is any CO formation in the burning then the vapour pressure of SO3 will increase dramatically. You must be sure there is no reductive burning in your current operations.