Application pulp paper industry

Because these variables have a very pronounced effect on the current density required to produce and also maintain passivity, it is necessary to know the exact operating conditions of the electrolyte before designing a system of anodic protection. In the paper and pulp industry a current of 4(KX) A was required for 3 min to passivate the steel surfaces after passivation with thiosulphates etc. in the black liquor the current was reduced to 2 7(X) A for 12 min and then only 600 A was necessary for the remainder of the process . From an economic aspect, it is normal, in the first instance, to consider anodically protecting a cheap metal or alloy, such as mild steel. If this is not satisfactory, the alloying of mild steel with a small percentage of a more passive metal, such as chromium, molybdenum or nickel, may decrease both the critical and passivation current densities to a sufficiently low value. It is fortunate that the effect of these alloying additions can be determined by laboratory experiments before application on an industrial scale is undertaken. 

Wood is one of the oldest constructional materials. Historically it was important in world exploration and trade, and the defence of that trade, in the provision of merchant ships and navies. It was also important in the early days of railway engineering and in building construction. Although in many applications wood has been replaced by other materials, this renewable resource now supports the growing industries of manufactured wood products. Prominent amongst these are the panel materials chipboard, flake-board, strandboard, plywood and blockboard, hardboard and softboard, wood-cement products and the products of the very large pulp and paper industries. 

Biocides are also used in the pulp and paper industry for the protection of processing materials. The main biocides used in this application fall into the preservative range and can be different from others employed within the paper processing. 

The types of biocides used in this application vary from the rest of the pulp and paper industry. These require to be longer lasting, i.e. sometimes up to 1 years protection is storage tanks and hence fall into the category of preservatives. 

Dumont, G. A., Application of Advanced Control Methods in the Pulp and Paper Industry - A Survey, Automatica, 22 143 (1986)... 

The biotechnological potential of laccases—working with air and producing water as sole by-product—has led to applications from the textile to the pulp and paper industries, from food applications to bioremediation, as well as their use in organic synthesis. 

No doubt the cost of xylanolytic enzymes will be one of the factors determining their application in the pulp and paper industry as well as in other areas. Economically feasible xylanase production can be achieved in paper mills employing xylanase-positive transformants of common industrially used microorganisms that are capable of utilizing inexpensive carbon sources originating there. A substantial improvement in the production of xylanolytic systems can be expeaed from mutants of non-cellulolytic microorganisms that are resistant to catabolic repression. Such mutants usually exhibit hyperproduction of extracellular enzymes. 

Thermophilic Anaerobic Reactor Applications. Pulp and paper industries typically discharge warm (50°C) effluents, and conventional reactors operating under mesophilic conditions require cooling of such wastewaters. Attempts have been made periodically by various groups to investigate the possibility of applying thermophilic anaerobic processes to pulp and paper discharges, but to date there is no conclusive evidence to prove the superior performances of thermophilic reactors as compared to their mesophilic counterparts. 

As enzymatic oxidative transformation of the PVA polymer can act as a multiple simultaneous event on the polymer with concurrent chain fission by the appropriate enzymes, the polymer can be broken down into small oligomers that can be channelled into the primary metabolism. This picture is not complete because PVA is usually more or less acetylated. The DH is a pivotal factor in almost every aspect of PVA application. Surprisingly there are very few data dealing with the enzymes involved in the deacetylation of not fuUy hydrolysed PVA polymer. In technical processes, esterase enzymes are widely applied to deal with PVAc structures. A good example is from the pulp and paper industry [85], where PVAc, a component of stickies , is hydrolysed to the less sticky PVA. Esterases from natural sources are known to accept the acetyl residues on the polymer as substrate but little detailed knowledge exists about the identity of acetyl esterases in the PVA degradative environment [86]. 

Chlorine (from the Greek chloros for yellow-green ) is the most abundant halogen (0.19 w% of the earth s crust) and plays a key role in chemical processes. The chlor-alkali industry has been in operation since the 1890s and improvements in the technology are still important and noticeable, for example, the transition from the mercury-based technology to membrane cells [60]. Most chlorine produced today is used for the manufacture of polyvinyl chloride, chloroprene, chlorinated hydrocarbons, propylene oxide, in the pulp and paper industry, in water treatment, and in disinfection processes [61]. A summary of typical redox states of chlorine, standard potentials for acidic aqueous media, and applications is given in Scheme 2. 

Supercritical fluid extraction is a new separation technique that finds a number of applications in the natural products, biochemicals, food, pharmaceuticals, petroleum, fuel, and polymer industries (1-8). There is now an interest in applying this technology in the pulp and paper industry (9,10). In a recent comprehensive study on the interaction of supercritical fluids with lignocellulosic materials, it has been shown that lignin can be not only extracted from wood by reactive supercritical fluids but also separated as solid products in solvent-free form by reducing the extraction fluid pressure from a supercritical to sub critical level (11,12). 

Uses. The dominant use of sulfur dioxide is as a captive intermediate for production of sulfuric acid. There is also substantial captive production in the pulp and paper industry for sulfite pulping, and it is used as an intermediate for on-site production of bleaches, eg, chlorine dioxide or sodium hydrosulfite (see Bleaching agents). There is a substantial merchant market for sulfur dioxide in the paper and pulp industry. Sulfur dioxide is used for the production of chlorine dioxide at the paper (qv) mill site by reduction of sodium chlorate in sulfuric acid solution and also for production of sodium dithionite by the reaction of sodium borohydride with sulfur dioxide (315). This last application was growing rapidly in North America as of the late 1990s. 

The applications of CE analysis to inorganic anions are already numerous and are rapidly growing. The application ranges include, e.g. clinical chemistry [53], the pulp and paper industry [55], environmental samples [49], waste waters from processing plants [56], process control, industrial applications [43,57-59], explosive residue analysis [48], biological samples [60], or drugs and intermediates [61,62]. 

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