Maintenance Benchmarking

2010-06-23 – Sitting in the lounge at Sao Paulo airport after a hard week undertaking a benchmarking review at a plant in Brazil followed by making a presentation on the benchmarking of the maintenance of a cement factory. Both very interesting, but now ready for a few days back in Blighty catching up with things in the office and around the home. Looks like we’ll be back in this part of the world in early August so there will be lots to do in the meantime.

Uncertainty continues to reign in the developed world with the UK’s austerity budget joining similar drives in most of Europe. Obama has sacked his general in Afghanistan and Kevin Rudd is being challenged from within his own party in Australia. This turmoil is no good for the cement business or Whitehopleman. Thankfully there are no such concerns in Africa, Asia or Latin America. In fact quite the reverse in Latin America where everyone is focused on seizing the moment while it is with them.

Looks like we’ll have more similar trips to do!

Brazil & Court Cases

2010-06-01 – Another week and another month has passed. We have had confirmation of our retention to do some benchmarking work in Brazil, so we will be on the road again in a couple of weeks time. Brazil is always an enjoyable experience so we will look forward to that. Bespoke and in-depth benchmarking continues to generate interest in the cement industry around the world. There is certainly a need to look in depth at the operations to identify the underlying reasons for performance variation and the routes to performance improvement.

Aside from that we are advising on a spoiled partial cargo of cement, where delays and interruptions in unloading might be the cause of the problem. These things are always somewhat speculative because it takes so long after the event for the dispute to mature into legal action. People who are not knowledgeable about cement make various assertions, which then have to be argued against. Anyway, it’s all part of the service!

Cemtech Workshop, Istanbul

2010-05-22 - World financial markets have had the jitters all week over the problems facing the Eurozone. This is not good for cement companies in Europe and not good for Whitehopleman’s customers there. No-one is going to start constructing major developments with the current uncertainties. It seems that Whitehopleman will have to continue focusing on Africa, Asia and Latin America.

That said we currently have a lot of Russian people on the CemNet on-line training courses (as well as a lot of people from Latin America). Russia is a country where there continue to be good prospects for the cement industry. Whitehopleman has submitted various proposals to assist with Russian projects but has not been retained there, as yet.

After a couple of quiet weeks we eceived two enquiries from established customers in Latin America this week, so it seems as if things are picking up again. That means we have to get on with the Pyroprocessing course while we have time!

We have been in discussions with Cemtech management this week and it has been decided that Dr Clark will chair and deliver a half-day workshop on the manufacture of low CO2 cements. This will be in Istanbul on Wednesday morning 29th September immediately following the Cemtech Europe conference. Hopefully we will meet some of our old friends and customers there. Maybe there might even be some Russians!

Pyroprocessing Course

2010-05-18 The weather has finally turned here in the UK and with temperatures in excess of 20C forecast everyone is feeling a bit brighter. Hopefully summer is here at last!

The development of the new “Pyroprocessing” course for the on-line training is making good progress. As you start to specify the course you realise what a massive subject it is. We have found it useful to use that mass and energy balance of cement kiln systems to define the course and its content. The starting point of any mass and energy balance is to define the boundaries of the system under consideration – exactly what we have had to do for the Pyroprocessing course.

Conventionally a kiln mass and energy balance includes the preheater, precalciner, rotary kiln and clinker cooler. Those and all the technology they involve will certainly be covered in the course. The next step is to measure the mass flows across the system boundaries, i.e. the feed, fuels and air into the system and the clinker, dust, exhaust gas and excess air flows out of the system. Our course will therefore also cover the technology involved in delivering these mass flows into the kiln system and transporting them away from the system. So gravimetric feeders, pneumatic and mechanical transport systems, process fans and pan conveyors.

Then the energy flows associated with the mass flows have to be calculated. These together with the energy losses as radiation and the energy consumed in the chemical reactions to form cement clinker make up the energy balance. The latter are already covered in our Cement Kiln Chemistry course. In this Pyroprocessing course we will need to consider this energy balance to explain the implications of different process technologies on pyroprocessing the kiln feed to produce cement clinker.

We had better get on with it if we are to meet our deadline of running the course for the first time in the final quarter of this year!

Real Clinker Mineralogy & Reactivity

2010-05-14 Now back in the office after a couple of days attending meetings in London and able to get back to the BLOG, Ask Dr Clark and other development projects. There is an interesting question from Eric Lalancette at Holcim Canada, an old on-line training participant. Eric is interested in monitoring clinker reactivity. IN my answer I’ve pointed him towards the techniques use by Cementaren Povazska in Slovakia. We were only there 2 weeks ago undertaking the latest instalment of our laboratory expert system development work with them. On that occasion the focus was on CO2 emission monitoring, but they are excited about their imminent installation of a COSMA on-line XRD spectrometer to continuously monitor the real mineralogy of their clinker.

On the development front the main project is a new “Pyroprocessing” course for the on-line training. This is something we have been wanting to do for ages and seen as a complement to the Grinding & Milling course focusing on the equipment in cement kiln systems in contrast to the Cement Kiln Chemistry course which focuses more on the material and chemical changes that it undergoes. It’s taken a long time to get round to writing this Pyroprocessing course because it’s a big job, but now there is some time and we can finally tackle it!

Hung Parliaments & Returning Customers

Here in the UK the weekend has been dominated by talk of the hung election and whether the Conservative and Liberal Democrat parties will be able to agree to form a stable coalition government. Meanwhile the financial crisis in Greece is dominating the Eurozone and the USA is struggling with the massive oil spill in the Gulf of Mexico. None of this is good for investor confidence and will not harbour well for the cement industries in the UK, Europe or the USA. What is not good for the cement industry is not good for Whitehopleman.

Against this gloomy backdrop we were very pleased to welcome an old customer from Saudi Arabia back into the benchmarking fold. We never really know why cement companies drop out, or why they then decide to come back. Probably personnel and priorities change and benchmarking drops down the list of priorities for a period. Whitehopleman just has to continue offering the service for when it becomes relevant to individual cement companies’ priorities again.

High Free Lime Clinker

A few days ago Dr Clark was contacted by an old colleague who is now the Technical Manager for a major Middle Eastern cement company. That company had switched the firing of their kilns from natural gas to coal and were now encountering the problem of high free lime clinker whenever the LSF rose above 93.5%. When the kilns were fired with natural gas there was no problem combining the clinker when the LSF was 96% or above. What could be the possible cause of this high free lime clinker problem?

The first and obvious thought was whether the ash content of the coal was being correctly adjusted for? The LSF of the kiln would need to be raised to compensate for the ash contribution from the coal, but was there an overcompensation due to lower than expected ash content or silica content of the ash? Dr Clark’s old colleague has many years experience and was immediately able to confirm that this was not the case. Some more complex reason must be causing the high free lime clinker.

Next thoughts turned to whether the chemistry of the clinker had changed significantly and whether there was now some inhibiting species present that would be preventing the clinker from being combined? In particular was there a significant excess of K2O over and above the SO3 in clinker? Again Dr Clark’s old colleague confirmed that alkalis had fallen and sulphate had risen, meaning the stoichiometric balance had improved. Alkalis in clinker were low enough to produce low-alkali cement. Again this could not be the cause of the difficulty in combining the clinker.

Just because the alkalis and sulphate were in balance in the clinker did not necessarily mean that they were in balance in the hot meal. What were the levels in the hot meal? Bingo! The alkalis were concentrating up the expected 2 to 3 times, while the sulphate was concentrating to 20 times that in clinker. This must mean that some sulphate was present as calcium sulphate in the hot meal. This can breakdown in the burning zone to produce free lime, sulphur dioxide and oxygen:

CaSO4 ↔ CaO + SO2↑ + ½O2↑

The free lime can formed so late in the process that there is no time for combination with C2S to form C3S and the clinker contains high levels of uncombined, free lime. Such high levels of recirculating sulphate often result in the clinker becoming dusty with low particle size grading as the flux viscosity is reduced. It was confirmed that the kilns had become increasingly dusty and that the problems were worse on the kiln with no alkali bypass installed. Corroborative evidence that the problem was related to recirculating volatile species. But what could be causing the very high sulphate recirculation?

This is where the ½O2↑ term on the right hand side of the equation for the breakdown of calcium sulphate is important. This is an equilibrium reaction and if there is a deficiency of oxygen then the reaction is driven to the right, i.e. the breakdown of calcium sulphate into free lime, sulphur dioxide and oxygen. Was there any deficiency of oxygen in the kiln?

Kiln inlet oxygen was reported to be 8%, so apparently not. However, there could still be local reducing conditions due to coarse grinding of the coal or poor mixing of the coal and combustion air in the burner. Poor mixing of the coal and combustion air would arise from insufficient momentum of the primary air delivered through the main burner of the kiln where a minimum of 10 N/MW of energy delivered by the burner is required to obtain good mixing of the coal and combustion air. Dr Clark’s former colleague is currently checking the coal fineness and momentum of the kiln main burner!

Launch the BLOG

2010 has been a busy year for Whitehopleman so far with projects and visits in Uruguay, Malaysia, Singapore, Australia, India, Brazil, Ethiopia and Slovakia. We haven’t really had time to draw breath. Anyway we now have a few days in the office and are tackling some website updates that we’ve been being asking for for some time. One of these is this BLOG that you are reading now. The idea is that Dr Clark will regularly update the BLOG setting out what we and he are involved in, and what our and his thoughts are. We hope it will be topical and at times even entertaining!

Other new features on the website are an “Ask Dr Clark” feature and “On-Line Benchmarking”. Lots of people in the cement industry around the world have Dr Clark’s email address and periodically ask for his advice on issues they are currently facing. Recent examples are a company in the Middle East who are facing problems of high free lime in clinker since they switched to firing their kiln with coal from natural gas. Another who would like to know the relationship between kiln feed residue and clinker grindability. Yet another wonders about the affect of ball media grading and surface area on grinding efficiency. The idea of “Ask Dr Clark” is for anyone to be able to ask Dr Clark’s advice on their current issues.

Whitehopleman’s benchmarking services are ongoing and now in their eleventh year. The idea of “On-Line Benchmarking” is for people to be able to benchmark any aspect of their current operations against the Whitehopleman database of cement factory performance via the www.whitehopleman.com website. The aim is for the service to be easy, inexpensive and instant. You don’t need to benchmark every aspect of your cement factory operations but can zoom in on those aspects that are relevant to your current projects.

While we are making these updates we are also taking the opportunity to update the Latest Projects and Training areas of www.whitehopleman.com.