Sticking in CEMENT

Castle Cement has supplied many tonnes of its products to some of the biggest engineering contracts of recent years: the Second Severn Crossing (see cover), the widening of the A1 and London Underground's Jubilee Line extension. But these prestige jobs have barely compensated for the past decade's decline in cement sales.

`In 1989, total cement sales for the UK industry were about 18-19m tonnes, but in 1996 that figure is likely to have been around 12m tonnes,' said Neville Roberts, general manager of Castle's Ketton works, in Lincolnshire. `There is no Holy Grail on the horizon.'

Compared with continental Europe, cement sales in the UK per capita are significantly smaller. British engineers do not utilise cement in as many bulk applications as do other Europeans. Continentals often use cement for road surfaces while the UK's civil engineers generally do not. The European switch to concrete rather than metal crash barriers has not taken off here either. The UK's prices are now Europe's lowest.

`Since 1989, Castle has had to cut its staff from about 2000 to 1200 and we had to close our Hertfordshire works in 1990, which had been producing 900kt/a. Unless the market picks up during 1997, we'll be faced with having to make kiln stops,' Roberts said.

Bagged sales have stubbornly remained at about 16 per cent of total sales and this market is shifting towards 25kg, rather than 50kg, bags. To maintain sales volume the company has to fill twice as many bags, which has required the installation of a new £2.5m packing line, becoming operational in August.

Although the 25kg bag is a relatively new product for Castle it is a development to maintain rather than increase sales. Further automation is on the way.

Fuelling recovery

One area where this process industry has been able to make real financial savings is its consumption of fuel and electrical power. The Ketton works alone draws 30MW/a out of the whole company's 70-80MW/a total, `more power than Burnley uses', according to Roberts.

The company burns around 400 000t/a of coal to produce the cement. Overall production from its two plants, the other being Ribblesdale in Lancashire, makes Castle the UK's second largest producer of cement.

Perhaps anticipating a squeeze on its margins, Castle developed Cemfuel in the early 1990s. Cemfuel is Castle's registered name for a blend of reprocessed waste solvents, such as white spirits and by-products from the pharmaceutical, chemical, paint and printing industries. The constituents of the fuel, which is largely acetone-based, would otherwise need to be incinerated commercially, used as landfill, or even being dumped.

`We wanted to design an artificial fuel and, after agreeing on the composition, we had to find somebody to make it as well as persuading HMIP (now part of the Environment Agency) to accept it,' Roberts explained.

Castle's conditions for accepting a supplier's secondary liquid fuel are quite stringent, ranging from the specific gravity of the blend to its maximum permitted levels of heavy metals. Castle has contracts with several secondary liquid fuel suppliers: Solrec, of Heysham; Safety-Kleen, of Sheffield; and CMR, based in Rye.

Roberts believes that because of the chemical industries' gradual move away from the use of organic solvents, availability of Cemfuel ingredients will diminish over time: `it has a shelf life'.

Money to burn

In the meantime, Castle is paid around £5/t by the suppliers to burn Cemfuel. This is instead of Castle having to pay at least £28/t for the coal the Cemfuel replaces. The recycled fuel does not completely replace the coal but it has constituted up to 20 per cent of fuel mixtures in cement production. Over the last year Neville estimates that Cemfuel has saved Castle about £1.5m.

`Looking around Europe, there are some cement plants that are already burning 100 per cent recycled fuels. We have been forced down this road because of the joint pressures of economics and the market's drive towards more environmentally sound manufacturing.'

Burning Cemfuel has enabled Castle to optimise the quality of its cement. The flame thus produced is more stable, so process optimisation is possible and kiln performance can be improved.

`There are some mineral improvements in the product quality of the cement, there have been fewer complaints from customers about the 40 parameters of the chemistry of the product.

`Sometimes, the supplies from the coal industry can make it difficult for us to get the right kind of coal, but because we can supplement the fuel value of poorer coal with Cemfuel we can now burn Scottish coal. Another environmental benefit is that we have switched 90 per cent of our coal transportation from road to rail,' he said.

Gaseous and particulate emissions have long concerned the communities that neighbour cement works (see box above), but Roberts believes that the burning of Cemfuel does not pose any worse threat to air quality than coal.

Assessments of Ketton's emissions, performed by AEATechnology in 1995, show that levels of most pollutant gases, particulates and metals are actually lower when the fuel mix contains Cemfuel than when the fuel is only coal.

Roberts added: `Emissions from cement manufacture are not related to the fuels that we use; they are related to the quality of the raw materials.'

OLD TYRES: NEW ENERGY

At the end of 1996, the Environment Agency gave Castle Cement permission to add waste tyres to its list of fuels. Trials are taking place until mid-1997 and if successful the company plans to burn 40 000t/a (1t=150 tyres). When permission was granted to Castle, Roberts announced: `Burning tyres will produce none of the smells and smoke associated with putting a tyre on the bonfire. The kilns operate at 1500 degreesC so every part of the tyre is consumed.'

The other main cement makers in the UK, Blue Circle and Rugby have also been moving into the alternative fuels arena. Not wanting to leave anybody out, Roberts said: `Castle is probably the best at burning solvents, Blue Circle is the best at tyres and Rugby is best at combination burning.'

* While not directly criticising cement manufacturers' choosing to burn secondary liquid fuels, the generic term for Cemfuel, the House of Commons Environment Committee last month lambasted the Environment Agency's handling of the issue of the burning of waste solvent-derived fuels (see News Analysis on page 12).