Quality briquette

A completely different situation exists if the rollers are pocketed or corrugated, because the flow of material is stopped when the land areas between the pockets or the ridges of the corrugations are in close proximity. For such rollers virtually no minimum speed exists. As the filling of the cups is the controlling factor and the disintegrating forces discussed above diminish with reduced speed of compaction, briquette quality improves in most cases if the rollers are slowed down. 

The production of smokeless fuel briquettes, both for domestic and industrial use, from bituminous coal using a binder is an old art and there are several commercial processes available (Franke, 1930 Haake and Meyer, 1930 Rhys Jones, 1963 Schinzel, 1981 Perlack et al., 1986). But the increasing use of petroleum, gas, and electricity for heating purposes and the reduction in the number of individual heating plants have caused a reduction in the use of coal briquettes. In spite of this, and contradictory as it may seem, the increased use of petroleum has been of some value to the briquetting industry. During the last 20 years the intense competition from petroleum products, as well as an increase in demand by consumers for briquette quality, led to automation of the production of briquettes and a continuous improvement in quality. 

Grades, Quality Control. Fluorspar is marketed ia several grades metallurgical fluorspar (metspar) is sold as gravel, lump, or briquettes. The minimum acceptable assay is 60% effective calcium fluoride. The effective value is determined by subtracting from the contained calcium fluoride 2.5% for every percent of Si02 found ia the complete analysis apparently based on the following stoichiometry (1) ... 

Low Temperature Carbonization. The Lurgi Sptlgas process was developed to carbonize brown coal at relatively low temperatures to produce tars and oils (Fig. 5). A shaft furnace internally heated by process-derived fuel gas (Spblgas) is used. The product can range from a friable coke breeze to hard lump coal depending on the quality of the briquettes used in the feed. The briquettes, made in normal extmsion presses, break down into smaller sizes during carbonization. 

Quality Control. The spectrometer is the most suitable instmment for determining most low level residual impurities. ASTM E414 is the standard method for the measurement of impurities in copper by the briquette dc-arc technique (65). In this method, the sample in the form of chips, drillings, or powder is briquetted and excited in a d-c arc opposite a high purity copper rod. Impurities in the ranges noted can be measured ... 

A correlation analysis of the chemo-physical parameters of Rhenish brown coal and its briquettability gives only trend data as well. Therefore generally an anticipated quality assessment of the briquettes is restricted to the following points ... 

Although briquettes made in a single-row pilot plant may be of excellent quality, for some materials performance of a commercial multirow press may be unsatisfactory. Such problems are normally encountered with materials demanding high compaction ratios. 

In the case of multirow presses it may be impossible to achieve an adequately uniform distribution of the feed on the rollers. Part of the maldistribution may be due to uneven gas back-flow, particularly in the center of wide rolls (see above). The influence of uneven distribution becomes more critical as the briquette volume decreases. With very small pockets it becomes almost impossible to produce briquettes of uniform quality in multirow presses. 

In the case of wider rolls it is necessary to take special measures that result in sufficiently uniform overall distribution of the feed. A simple way to improve the quality of border zone briquettes is shown in Figure 289. The reduced feed rate is compensated by pockets with smaller volume in the two outer rows. Smooth compacting rollers are sometimes finished with a concave surface to accomplish the same effect. 

Figure 289. Cross section through a roll sleeve with reduced volume of the border pockets to improve quality of these briquettes...

Recycling offines and chips as well as briquettes of poor quality Figure 407 demonstrates schematically the recycling system. Reference should also be made to Figures 403(a) to (e) and 406. 

Excess feed that overflows through the chute (30), poor quality briquettes, or chips from the screen (17) as well as chips and fines from the load-out screen (20) are collected by conveyors (22 and 24) and transported to the reject hopper (23). From there, the material is extracted at a controlled rate and is conditioned... 

As far as the utilization of the seed cake is concerned, the research revealed that the seedcake could pressed into briquettes, which can be used as fuel in wood stoves or ovens. Using seedcake as fertilizer could be more promising because of its favourable nutritional qualities. This possibility was mentioned by several respondents, but it remains untested as yet. Potential actors in this domain are farmers who want to use the cake as fertilizer, and the oil pressing facilities, which generate jatropha cake as a by-product. 

Anhydrous hydrogen cyanide and a 50% solution of sodium hydroxide are fed into a reactor. The reactants are heated in a crystallizer to remove water and form the sodium cyanide crystals. The sodium cyanide is filtered, then dried on a conveyor. Mechanical devices (e.g., cyclones) are used to produce wither briquettes or granular products. The feed must be essentially pure to obtain high quality, 99% sodium cyanide [75]. Figure 4.6 is a flow diagram of the sodium cyanide process [76],... 

Other high-quality metal refuse that is suitable for remelting is not produced or collected in such large amounts as cast-iron borings or aluminum swarf, discussed above. Such materials are densified and shaped in newly designed small hydraulic punch-and-die presses. Fig. 6.9-25 shows a collection of briquettes from different... 

Fig. 6.10-16 High-quality pillow-and egg-shaped coal briquettes...

Smokeless fuel was expected to become again a consumer product with all its new requirements, especially excellent physical quality and pleasing appearance. The latter motivated one producer in the UK to dip the briquettes into a special gold bronze die during curing to eliminate the dirty black coal look . 

---