Like known kerosene, obtainable diesel fuel and gasoline with coal liquefaction conversion process. Obtainable gas fuel with coal gasification process. One of process that is simple is modification of coal becomes a coal mixture having the character of liquid that is coal water fuel can replace burning oil which is one of petroleum product.
a. RAW MATERIAL CWF
As component of standard utilized by coal having high caloric value (more or less 7000 kcal/kg) as compensation of usage of water so that caloric value CWF obtained enough heights also. Bitumen type coal raw material with high caloric value and wafting water content (inherent moisture) low is suggested so that constraint the low of caloric value cwf obtained able to be overcome. Actually earns also is utilized bitumen sub and or lignite, But both types of the has high wafting water content so that cwf yielded will have low caloric value. To overcome the thing must be done draining at temperature and high pressure.
Clauses of raw material CWF is ;
1. Low ash content
2. Matter content flies bigger than 20%
3. Number HGI height must
4. Fouling and slagging low index
5. Sulfur content less than 1 %.
Beside doesn't contaminate air, ash content must be low to lessen modification fare of stove at dismissal of base ash (bottom ash). Matter content flies > 20 % to water down en kindling. In making of CWF utilizes smooth coal (- 75 microns) hence required hulling. On that account number HGI height must to lessen grind fare. Height ash melting point must avoid precipitation to of ash which is easy melts at stove interior (boiler). The happening of fouling and slagging can stop operation, on that account fouling and slagging need to be cleaned to return high temperature switching. Index fouling and slagging influenced by alkalies content and brimstone in ash. Side that is sulfur content must be low to prevent environmental contamination and interior corrosion boiler.
b. ADDITIVE
Additive is material added into mixture CWF and functioning to add the stability, mean prilled of the coal doesn't decants during old (2 month or more). There is also functioning additive dispersion to prilled of the coal. Additive addition ranged from 0,1 to 1,5 depends on kinds of the additive. From result of research it is concluded that good additive in the form of surfactant (surface activator reagent item) what can be consisted of surfactant ionik (anionik or kationik) and surfactant non-ionik.
There is also other additive which the function to make mixture having the character of emulsion and stable. Because this surfactant type many variation, so is required research specially suited for coal is being used to raw material CWF. Clauses of good additive is must be effective, be combustible in process of combustion and cheap.
b. Making CWF
Making technology of CWF is including simple especially if using coal raw material having high caloric value (more or less 7000 kcal/kg). Coal having low ash content (< 10%) grind to become 10 mm and then is milled with ballmill. Hulling is done with concentration of high solid (more or less 70% coal). Result of grind is done at one particular size separation (size classifier) at winnow measure 75 microns. Big oversize 75 microns distribute to equipment of reduction of water (dewatering) if required. The biggest particle size of coal doesn't fetch up all standing by 75 microns only, earns also bigger or smooth depended from coal type. Level of concentration of mixture at squealer (mixing) determined when optimization of laboratory scale before all. For coal with quality of height, process of CWF earns more simple.
After hulling earns direct is done squealer where at this additive phase is added. At low level coal with high wafting water content need to be done draining in advance at high temperature. Squealer taken place only during few minutes with high rotation (> 6000) and yields high stability (> 2 month).