Wood pulp industry

Many aldehydes are particularly fragrant. A number of flowers, for example, owe their pleasant odor to the presence of simple aldehydes. The smells of lemons, cinnamon, and almonds are due to the aldehydes citral, cinnamalde-hyde, and benzaldehyde, respectively. The structures of these three aldehydes are shown in Figure 12.21. The aldehyde vanillin, introduced at the beginning of this chapter, is the key flavoring molecule derived from the vanilla orchid. You may have noticed that vanilla seed pods and vanilla extract are fairly expensive. Imitation vanilla flavoring is less expensive because it is merely a solution of the compound vanillin, which is economically synthesized from the waste chemicals of the wood pulp industry. Imitation vanilla does not taste the same as natural vanilla extract, however, because in addition to vanillin many other flavorful molecules contribute to the complex taste of natural vanilla. Many books made in the days before acid-free paper smell of vanilla because of the vanillin formed and released as the paper ages, a process that is accelerated by the acids the paper contains. 

However, the rapid development of the young wood pulping industry, especially in Sweden, finally stimulated the interest of scientists in... 

Wintzer, P. 1980. Enticklung und Trend der Chlordioxid-Bleiche mil iniegrierler Chlorat-Electrolyse fUr die Zellslojf-Indusirie (Developments and trends in chlorine dioxide-bleaching with an integrated chlorate electrolysis for the wood pulp industry), Chem. Ing. 52, Tech. 392-398. 

Organic sources include natural organic complexes that are byproducts of the wood pulp industry, as well as synthetic chelates which are generally more effective than inorganic salts. The synthetic chelates are relatively expensive to use. 

The United States Pulp Producers Association, Inc., of New York, issues annually Wood Pulp Statistics (17) which is available to anyone interested in the wood pulp industry. Data on the production, consumption, and sales of wood pulp are assembled monthly, and on production facilities, biennially. These are restricted to members. 

Substances often called dioxins have been present as contaminants in many pesticide formulations and in some bactericidal products. Dioxins are found in smoke from refuse incinerators and in effluents from the wood pulp industry, which uses chlorine as a bleaching agent. The magnesium industry used a production method that caused the formation of many "dioxins" (strictly speaking, dibenzofurans). Car exhaust fumes and cigarette smoke also have a low concentration. But dioxins may also be formed from more natural processes such as forest fires and cremations. Forest fires are suspected of producing 59 kg of dioxin per year in Canada alone. Humans have thus been exposed to dioxins long before the modern age. 

Vanilla can also be extracted from plants other than Vanilla planifolia, such as potato peels and pine tree sap. The most economical source of the product, however, is waste material left over from the wood pulp industry. That waste material consists primarily of lignin, a complex natural polymer that, along with cellulose, is the primary component of wood. The wastes from wood pulping can be treated to break down and separate the lignin. This leaves behind a complex... 

One of the driving forces for developing new designs of kiln is that substantial quantities of calcium carbonate are available in a finely divided form. The sugar and paper/wood pulp industries, for example, produce a calcium carbonate sludge (see sections 30.4 and 32.16), which can be calcined and recycled. Many plants use rotary kilns for this purpose, while some use fluidised bed kilns [16.6,16.48,16.49]. 

The terms a-, jS-, and y-cellulose are used slightly differently in the wood-pulp industry. Here, a-cellulose is the high-molecular-weight component. jS-cellulose is the fraction that is soluble in 17.5% alkali and that is precipitated by neutralization. y-Cellulose is the component that remains soluble during neutralization. Both P- and y-celluloses have low degrees of polymerization (200) and are partly oxidized. 

A most important aroma compound worldwide, vanillin, is obtained primarily by alkaline hydrolysis of lignin (sulfite waste of the wood pulp industry), which yields coniferyl alcohol. It is converted to vanillin by oxidative cleavage ... 

Another source of plant sterols is tall oil. This is a by-product of the wood pulp industry formed when coniferous woods are digested under alkaline conditions ( tall means pine in Swedish, but pine oil has long been used as a commercial name for the lighter volatile terpene fractions of wood extraction). The fatty and resinous substances contained in the wood are brought into alkaline aqueous solution and are recovered as skimmings . These are the sodium salts (soaps) of fatty and rosin acids, together with neutral substances such as plant sterols and long-chain fatty alcohols. After acidulation, the tall oil soap is processed by a sequence of distillations into different fatty acid and rosin acid products. 

TTiere remains an unused potential source of wood sterols in the side-streams of the wood pulping industry. At the end of 2001, the global production of wood-derived sterols was estimated to be 1500 tonnes/year. However, the maximum potential has been estimated to be 20 times higher. Constraining factors are the high capital investment, with sterols being, so far, the only product. In contrast, when sterols are recovered from vegetable oil distillates most of the capital investment has already been covered in the production of natural tocopherols. 

The awareness of the need to monitor paper and pulp mill effluent is not novel. The reduction, and even elimination, in the use of chlorine in the bleaching of pulp has focused environmental concern on the other elements present in wood pulp. Pulp and paper mill effluent may contribute to elevated metal concentrations in receiving waters and sediments. Consequently, the wood pulp industry, along with statutory monitoring bodies, make regular use of sensitive and quantitative techniques such as DCP AES and GF-AAS in attempts to reduce metal levels. 

This system has been extensively examined because of its technological significance in the wood pulp industry. In the current textbooks sulfur dioxide is stated to have a high solubility in water because of the chemical reactions symbolized as... 

The usual source of commercial lignin is waste liquor from the wood pulp industry. It contains sodium ligninates or lignin sulfonates. Previously, liquefaction of lignocellulosic products was achieved using several hard treatments. One consisted of treatment at 320-400 °C in aqueous or organic solvents (Widsten et al, 2002). A second treatment used an acidic catalyst... 

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