Edition 01/16

The Dyckerhoff cement plant in the “Münsterland” region is a unique location in Germany for so-called deep well cement. The material is put into the bore holes of gas fields and crude oil fields all over the world to seal and stabilise the outer walls at depths of between 6,000 and 8,000 metres. The prevailing temperatures and pressures pose a real challenge for deep well cement, which is why the parent rock, and additional aggregates, must be of very special compositions. Within Germany, these materials are available only in Lengerich.

Specialists for deep holes

Whether it’s for simple Portland cement, special types of cement for civil engineering, blast furnace slag cement, or mixtures with nanocrystalline structures, Dyckerhoff’s basis is always limestone, found right on their doorstep, and a composition of aggregates. These materials are mixed, well ground and then heated in a rotary kiln. To obtain this material, the mixture is exposed to a sintering process. The sintering zone in rotary kiln 8, with a length of 58 metres, reaches temperatures of about 1,500 degrees Celsius. The kiln is one of two rotary kilns in Lengerich which Dyckerhoff commissioned in 2001, and which is still one of the most modern kilns in Europe due to its high energy efficiency.

Blower technology for fuel supply

Hot process air is one of the most important energy sources, as heat ultimately determines the production process. Dyckerhoff uses fuel oil for heating up, and then switches to pulverised lignite which is blown into the rotary kiln by means of a burner lance. The lignite burns immediately. Dyckerhoff can also burn derived fuels in these kilns. This fibrous mass is called “fluff,” which is accrued during the reclamation process for recycling sacks.

For the supply of the burner, Dyckerhoff also uses the principle of pneumatic conveying technology. AERZEN Displacement Blowers (GM25, 304 to 1452 m³/h, 55 kW max) of the series Delta Blower are used here. The packaged unit supplies volume flow of 16 cubic metres per minute at a motor connected load of 36 kW for the transport of the pulverised lignite and the fluff. With the new Generation 5 of Delta Blower, AERZEN has a series in the market which is extraordinary in terms of its effectiveness. Both units at Dyckerhoff ensure that the fuel from the silos reaches the burner nozzle under optimal pressure and in sufficient quantity. The biggest cost driver in cement production is increasing energy costs. As a result, the company has responded by increasingly using derived fuels. Burning fluff brings a lot of advantages in ecological terms, as primary energy sources are conserved. One ton of fluff provides almost as much energy as one ton of lignite.

Dust generated during the production process, which consists of raw material, is separated by electrical gas cleaning (EGR) and collected in silos. Afterwards, the EGR dust is returned into the process – this is achieved by means of a conveying system where AERZEN Delta Screw packages (VML 18, 380 to 1.190 m³/h, 75 kW max) provide the necessary volume flow of 18 cubic metres per minute in the piping. Today, electrical filters are an established technology for removing dust from exhaust air and for ensuring that the amount of pure dust is significantly below 10mg/m³. Dyckerhoff applies smaller positive displacement blowers (GM4 S, 46 to 342 m³/h, 15 kW max) from AERZEN, which blow air into the silo via a pneumatic ground, and which regularly mix the material with an air volume of six cubic metres per minute. This procedure avoids agglutination of fine material in the silo.

The unit is located in the area where the raw preparation of the untreated meal takes place. A vertical mill crushes the limestone into a fine pre-dried meal, which is then blown from the storage silo through transport piping into the heat exchanger which is more than 100 metres high. Here, the raw meal is brought to temperature and flows through zones which are progressively hotter and hotter, until finally the furnace intake of the rotary kiln is reached. Delta Screw packages type VML 18, with a motor rating of 45 kW, a pressure of 2.25 bar and a volume flow of 1,080 cubic metres per hour each, are those which keep the transport network running from the storage silo to the kiln. AERZEN offers single-stage, oil-free screw compressors in different sizes, with volume flows of between 950 and 15,000 cubic metres per hour. The units are designed as universal tools, dimensioned for maximum energy efficiency, offering the possibility of combining any compressors and accessory components on a modular basis. The compressors can thus be adapted to suit the relevant application. 

Close co-operation in service as well 

Rotary kilns are designed for continuous operation because of the high energy consumption during firing alone. Furthermore, these units are very sensitive to temperature changes - the lining of the interior would suffer damage because of alternating hot and cool phases. If this were to happen, repairs would be necessary, and these would cause a week of standstill - a long period of production downtime for Dyckerhoff.

Therefore, the group exclusively applies technology which ensures maximum availability – supported by servicing. Because of that, the co-operation with AERZEN is very close on the service level and goes hand-in-hand on preventive maintenance: as soon as the service technician from AERZEN sets off, the maintenance team in Lengerich begins the preparation work.