Processing chemical treatment

Figure 36. Schematic of the NST process chemical treatment of the fine tailings such that the floe or aggregate structure can support the coarse tailings, followed by the consolidation of the combined tailings to release water, and create a more stable tailings deposit.

The sweet water from continuous and batch autoclave processes for splitting fats contains tittle or no mineral acids and salts and requires very tittle in the way of purification, as compared to spent lye from kettle soapmaking (9). The sweet water should be processed promptly after splitting to avoid degradation and loss of glycerol by fermentation. Any fatty acids that rise to the top of the sweet water are skimmed. A small amount of alkali is added to precipitate the dissolved fatty acids and neutralize the liquor. The alkaline liquor is then filtered and evaporated to an 88% cmde glycerol. Sweet water from modem noncatalytic, continuous hydrolysis may be evaporated to ca 88% without chemical treatment. 

A wide range and a number of purification steps are required to make available hydrogen/synthesis gas having the desired purity that depends on use. Technology is available in many forms and combinations for specific hydrogen purification requirements. Methods include physical and chemical treatments (solvent scmbbing) low temperature (cryogenic) systems adsorption on soHds, such as active carbon, metal oxides, and molecular sieves, and various membrane systems. Composition of the raw gas and the amount of impurities that can be tolerated in the product determine the selection of the most suitable process. 

Certain chemical treatments can be employed during the TMP process to achieve improved strength. Sodium sulfite and hydrogen peroxide have been used either for chip pre- or post-treatment of the TMP pulp such pulp is called chemithermomechanical pulp (CTMP). The strength improvements, which may be 50%, are obtained at some sacrifice to yield and opacity. The yields of mechanical pulps are 90—95% the lower yields are associated with chemical treatment. No principal commercial pulps are produced in the next lower yield range, ie, 80—90%. 

Fusel Oils. The original source of amyl alcohols was from fusel oil which is a by-product of the ethyl alcohol fermentation industry. Refined amyl alcohol from this source, after chemical treatment and distillation, contains about 85% 3-methyl-1-butanol and about 15% 2-methyl-1-butanol, both primary amyl alcohols. Only minor quantities of amyl alcohol are suppHed from this source today. A German patent discloses a distillative separation process for recovering 3-methyl-1-butanol from fusel oil (93). 

Real irreversible processes can be subjected to thermodynamic analysis. The goal is to calciilate the efficiency of energy use or production and to show how energy loss is apportioned among the steps of a process. The treatment here is limited to steady-state, steady-flow processes, because of their predominance in chemical technology. 

When the pressure rises to the permissible maximum, the cartridge must be opened and the element replaced. Micronic elements of the fiber type cannot be cleaned and are so priced that they can be discarded or the filter medium replaced economically. Stone elements usually must be cleaned, a process best accomplished bv the manufacturer of the porous ceramic or in accordance with the manufacturer s directions. The user can clean stainless-steel elements by chemical treatment. 

Adsorption This is the most widely used of the physical-chemical treatment processes. It is used primarily for the removal of soluble organics with activated carbon serving as the adsorbent. Most liquid-phase-activated carbon adsorption reactions follow a Freundlich Isotherm [Eq. (25-21)]. 

The cellulose fiber in paper is attacked and weakened by sulfur dioxide. Paper made before about 1750 is not significantly affected by sulfur dioxide (11). At about that time, the manufacture of paper changed to a chemical treatment process that broke down the wood fiber more rapidly. It is thought that this process introduces trace quantities of metals, which catalyze the conversion of sulfur dioxide to sulfuric add. Sulfuric acid causes the paper to become brittle and more subject to cracking and tearing. New papers have become available to minimize the interaction with SO2. 

The general purpose of ultimate disposal of hazardous wastes is to prevent the contamination of susceptible environments. Surface water runoff, ground water leaching, atmospheric volatilization, and biological accumulation are processes that should be avoided during the active life of the hazardous waste. As a rule, the more persistent a hazardous waste is (i.e., the greater its resistance to breakdown), the greater the need to isolate it from the environment. If the substance cannot be neutralized by chemical treatment or incineration and still maintains its hazardous qualities, the only alternative is usually to immobilize and bury it in a secure chemical burial site. 

Chemical treatment is a class of processes in which specific chemicals are added to wastes or to contaminated media in order to achieve detoxification. Depending on the nature of the contaminants, the chemical processes required will include pH adjustment, lysis, oxidation, reduction or a combination of these. Thus, chemical treatment is used to effect a chemical transformation of the waste to an innocuous or less toxic form. In addition, chemical treatment is often used to prepare for or facilitate the treatment of wastes by other technologies. Figure 12 identifies specific treatment processes which perform these functions. 

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