Paper engineering is a branch ofengineering that deals with the usage ofphysical science (e.g. chemistry and physics) and life sciences (e.g.biology andbiochemistry) in conjunction withmathematics as applied to the converting of raw materials into usefulpaper products and co-products.[citation needed] The field applies various principles inprocess engineering andunit operations to the manufacture ofpaper,chemicals,energy and related materials. The following timeline shows some of the key steps in the development of the science of chemical and bioprocess engineering:[1]
From a heritage perspective, the field encompasses the design and analysis of a wide variety of thermal, chemical and biochemicalunit operations employed in the manufacture of pulp and paper, and addresses the preparation of its raw materials from trees or other natural resources via apulping process, chemical and mechanical pretreatment of these recoveredbiopolymer (e.g. principally, although not solely,cellulose-based) fibers in a fluid suspension, the high-speed forming and initial dewatering of a non-woven web, the development of bulk sheet properties via control of energy and mass transfer operations, as well as post-treatment of the sheet with coating, calendering, and other chemical and mechanical processes.[2]
Today, the field of paper and chemical engineering is applied to the manufacture of a wide variety of products. The forestry and biology, chemical science, (bio)chemical industry scope manufactures organic andagrochemicals (fertilizers, insecticides, herbicides),oleochemicals, fragrances and flavors, food,feed,pharmaceuticals,nutraceuticals,chemicals,polymers and power from biological materials.
The resulting products of paper engineering including paper, cardboard, and various paper derivatives are widely used in everyday life. In addition to being a subset of chemical engineering, the field of paper engineering is closely linked toforest management, productrecycling, and the mass production of paper – based media.
In the process of mechanical pulping, "grinding" and "refining" are the two main methods used to create the pulp. Grinding is the method of pressing logs and chips against a turning stone to produce fibers. Refiner pulping is treating wood chips with chemicals or heat and then crushing the objects between two disks, one or both of which are rotating. There are four main types of refiner pulping, which includes refiner mechanical pulping, thermo-mechanical pulping, chemi-mechanical pulping, and chemithermomechanical pulping.[3] Further descriptions of each process are contained in this link:[4]Mechanical pulping, when compared to chemical pulping, is relatively inexpensive and has a high pulp yield (85–95%). However, the paper created is generally weak since it retains the lignin.[2]
The process ofchemical pulping is used to chemically disband thelignin found in the cell walls of the material undergoing the process. After thecellulose fibers are separated from the lignin, a pulp is created which can then be treated to create durable paper, boxes, and corrugated cardboard. Chemical pulping can be characterized by two main methods: sulfate (Kraft process) pulping and sulfite pulping, and these two methods have different benefits. Sulfate pulping can be performed on a wide range of tree varieties and results in the creation of a strong type of paper. Conversely, sulfite pulping results in a higher volume of pulp which is easier to bleach and process. However, sulfate pulping is more widely used since the product is more durable and the chemicals used in the process can be recovered, thus resulting in minimal environmental pollution.[5]
The pulp is then processed through an apparatus which renders the pulp as a mesh of fibers. This fiber network is then pressed to remove all water contents, and the paper is subsequently dried to remove all traces of moisture.
After the above processes have been completed, the resulting paper is coated with a minuscule amount ofchina clay orcalcium carbonate to modify the surface, and the paper is then re-sized depending on its intended purpose.
Generally, the material to be recycled first undergoes mechanical or chemical pulping to render it in pulp form. The resulting pulp is then processed in the same way normal pulp is processed; however, original fiber is sometimes added to enhance the quality and appearance of the product.
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Today, the field of paper and bioprocess engineering is a diverse one, covering areas frombiotechnology andnanotechnology toelectricity generation.
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Generally offered as a specialization within chemical engineering:[6]
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