Brown coal briquetting

Fig. 6.10-7 Flow diagram of one of the last lignite (brown coal) briquetting plants built in Germany [6.10.2.2]...

Brown Coal Briquetting in Germany and the former State-Trading Countries of East Europe Braunkohle (1992)11, 16-19. 

In brown coal briquetting plants, these dryers are heated by exhaust steam from the briquetting machines. The steam carries away oil droplets, which are carbonized, forming deposits on the tube walls. To ronove impurities from the dryer tubes, these tubes may be washed by circulation of trichloroethylene at 70°C-80°C for about 3 h. The spent trichloroethylene is distilled for reuse. 

The rotary-tube dryers are used widely for coal drying in brown coal briquetting plants. They are also used for drying of hard coals. These dryers are indirect dryers heated by saturated steam at pressures of 0.15 to 0.55 MPa. This dryer (Figure 43.3) consists of a sloping drum (1), in which the perforated walls... 

Gas and Fuel Corporation Morwell, Australia 1956 Town gas Brown coal briquets 22 6 X... 

Brown coals yield, on solvent extraction, 10—15% of a material that contains 60—90% light yellow or brown waxy substances. The remainder is a mixture of deep brown resinous and asphaltic substances. The yield may be increased by increasing the pressure during extraction, but this also adds dark colored dispersion products, and the resultant brown coal caimot be briquetted. 

The moisture content of peat or brown coal that is briquetted for fuel must be reduced to about 15% for satisfactory briquetting. Mechanical or natural means are used because of the cost of thermal drying. Moisture is sometimes desirable. About 8% is necessary for prevention of combustible loss from a chain-grate stoker. 

L.A. Crockett, The briquetting of brown coal in Victoria, Australia. Proc. Inst. Briquet. Agglom. Bien. Conf., 13 (1973) 237—250. 

UBC [Upgraded Brown Coal] A process for upgrading brown coal for use in power plants. The pulverized coal is mixed with light petroleum and asphalt and heated to >140°C, which expels the water and solvent, leaving a porous material containing asphalt in the pores. This material is briquetted and is then suitable for use in a power plant. Developed by Kobe Steel from 1993, piloted in Indonesia in 2004, and expected to be commercialized in 2012. 

There are many investigations and publications available on the briquetting behaviour of brown coals, both from the GDR and the Rhenish area (6 to 9). 

In order to establish statistically usable data on the briquetting behaviour of Rhenish brown coals, the 15 brown coal lithotypes were briquetted under identical conditions (water content, grain size distribution and mould pressure) with a laboratory press. 

A macro- and micropetrographical analysis with a view to before technological problems involved in the briquetting process allows one at the most to judge the briquettability of Rhenish brown coal on the basis of trend data. 

In 1858 the first Exter press was built for brown coal. Since then, modifications have been made, mostly to adopt modern drive and design methods as well as to use stronger or otherwise improved materials of construction. However, essentially the same press is still used today to produce most of the world s output of brown coal briquettes. Although the importance of brown coal briquettes is fading quickly, further improvements are still being made and new applications are developed, e.g. for the briquetting of biomass. 

To illustrate discontinuous extrusion compaction of soft, formable materials with inherent or added binding characteristics, the extrusion briquetting process employed by the brown coal industry will be discussed as a typical example. 

Fig. 6.10-12 Different briquette shapes that can be obtained with ram extrusion presses Fig. 6.10-13 Development of brown coal" (bituminous coal) briquetting in Germany [6.10.2.3]...

Both direct and indirect dryers are in use for coal drying. Combustion gases or steam may be used as the heating medium. Steam-heated dryers (e.g., drum, tray, and tube dryers) are used mainly for drying of brown coals in the coal briquetting process. Frequently, coal drying is carried out in convection dryers, such as the following ... 

In Australia, indirect drying has been used for many decades to prepare brown coal for briquetting. In this process, low-pressure steam is condensed on the outside of tubes conveying brown coal to provide process heat the more water removed in liquid form, the higher the efficiency. After reducing the moisture to nominally 15%, dried brown coal is compacted into strong briqnettes nsing stamp presses. 

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