Refining, char

Char Refining. The dried char is pulverized into fine powder (carbon black) by a Jet mill. A small amount of binder is added to the carbon black. The carbon black is compacted into flakes by rolls and is pelletized by a breaker. 

Char formation and reduced monomer production are observed for all of these additives upon reaction with PMMA. Char formation increases as a function of temperature, for the hydrido cobalt compound, there is 5% char at 262°, 8.5% at 322°, 15% at 338°, and 19% at 375°C the cobalt(lll) cyanide produces 3% char at 338° and 11% at 375°C the cobalt(ll) cyanide yields 11% char at 375°C. At the highest temperature, 375°C, the amount of monomer formation is 22% for K3Co(CN)5, 11% for K3Co(CN)6, and 10% for HCo[P(OPh)3]4. Ideally one would hope to observe no monomer formation and complete char production. Such is not the case here, these materials probably have no utility as flame retardant additives for PMMA since monomer formation, even at a reduced level, will still permit a propagation of the burning process. While somewhat positive results for these three additives do not prove the validity of the hypothesis, we take this to be a starting point in our search for suitable additives, further work is underway to refine the hypothesis and to identify other potential hydrogenation catalysts and other additives that may prove useful as flame retardants for PMMA... 

The refining effect of ion exchange treatment is of sufficient magnitude to permit the elimination of a substantial portion of activated carbon, or bone char requirement. At least a portion of the cost of operation of the ion exchange unit is thus paid for by the savings in requirement of color adsorbent. 

The refinements that can be made to the model for coal char oxidation are seemingly endless (51). A few of these will be discussed briefly. 

A detailed history of the development of the bone char process for refining raw cane sugar is beyond the scope of this discussion, and those... 

The ability of bone char to function as an alkaline buffer, so essential in sucrose refining, is a definite disadvantage in the refining of dextrose where it is desirable to operate on the acid side of pH 6. It has been shown that the optimum pH range is as low as 3.0 to 3.5.3 However, since solutions of this acidity would attack storage vessels, char filters and pipe lines, it is impractical to operate in the optimum pH range unless acid resistant equipment is employed. Consequently pH 5 is a practical lower limit for the process. 

To achieve a pH of 6 or lower for the effluent from a char filter, it is necessary to acid temper the rebumed bone char after it has been returned to the filter, i.e., to treat the char with dilute acid. It is evident, therefore, that bone char is not well adapted, in this respect, to dextrose refining. Consequently, one obvious direction in which an improvement in the conventional process could be made would be the devising of an adsorbent which would buffer on the acid side of neutrality instead of on the alkaline side. 

For the refiner trying to mitigate the problem of spontaneous combustion, probably the two most important parameters to control are as follows (1) spent filter cake temperature and (2) oil content. Although the actual temperature marking the onset of second-stage charring will vary from plant to plant depending on type of oil and clay activity, the most important point is that spontaneous combustion should not occur if the spent filter cake temperature can be sufficiently lowered before exposure to the atmosphere. Obviously, water addition is one way to lower temperature and this approach is probably the simplest and most reliable method. 

The electrohydrothermoprobe (EHT) (W Matek et al., 1983) is a refinement of the monopolar probe. It allows a stream of water to be directed through the probe the site of bleeding can thus be irrigated and rendered more easily visible, and at the same time, charring of the tissue in contact with the probe is prevented. In 92% of reported cases, definitive haemostasis was achieved, with recurrent bleeding in 11% of patients. 

Basic scheme of the white, refined sugar manufacturing process in a raw sugar refinery. Clarification can be phosphatation or carbonation, and decolorization can be with granular carbon, bone char, or ion-exchange resins. Filtration is not required if phosphatation clarification is utilized... 

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