Process Controls and Fluid Fundamentals

Posted February 02, 2016 in Pulp and Paper Industry by Elizabeth Tischer

 

Process Controls and Fluid Fundamentals

 

The main objective of process control and fluid mechanics as it relates to the papermaking process is to ensure that the main operating processes and their parameters are kept within the bounds of the reference value of the process. Many professionals in the paper and pulp industry refer to the process controls and the fluid fundamentals as the “automation process” of the industry. Paper production initiates with the process of making pulp. This is produced one of two ways – chemically or mechanically. In this brief guide, we will review these process controls and expound on the fluid mechanics associated with the paper and pulp industry so that you are better able to understand the process, as a whole.

 

Papermaking

 

Paper is composed of fibers, which are derived from the wood from trees. Wood is a special, organic-based material that includes fibers and a substance between these fibers, called “lignin”. According to studies, one piece of paper easily includes millions of individual fibers. These fibers are held together with hydrogen-based bonds. Today’s modern paper and pulp mills typically have thousands of very basic control mechanisms and loops. These devices control the fluid flows in the paper and pulp creation process, the temperatures of the materials required to make paper, the pH of the stock contained within the tanks, and various other aspects of the papermaking process.

 

Pulping

 

The main process control and fluid mechanics is the pulping process. As mentioned previously, this process may be further broken down into two processes: mechanical and chemical. Mechanical-based pulping is performed by grinding and/or refining wood. This process is highly dependent on energy. The chemical-based pulping is performed by cooking the chips of the designated wood in a special type of liquor that is within a specially-designed digester. This requires a form of mechanical-based refining at a paper and pulp mill. When mechanical pulp and chemical pulp are combined, the properties of the pulp, overall, may be strengthened.

 

Papermaking Process, As a Whole

 

In order to understand the process controls and fluid mechanics, it is first important to understand the papermaking process, as a whole. The following outlines this process – from start to finish:

 

1.     The trees are taken from the forest and transferred to the paper mill.

2.     The trees are placed into the boiler, which produces steam that is used for the turbines.

3.     The turbines are specially-designed devices that make the electricity for the various motors and assortment of pumps that are used at the paper mill.

4.     The steam dries the paper, and cooks the wood chips in the digester during the process control of pulping.

5.     The mixture that comes out of the digester then goes into a blow tank that is non-pressurized.

6.     Washers then start and initiate the process of cleaning the mixture of debris, such as chemicals.

7.     Then, the black liquor that remains from the washer’s process is then pumped into large evaporators. These machines remove the water.

8.     Then, it is combined with lime in a causticizer from a special kiln.

9.     The fluid is then pumped into a clarifier machine.

10           10.  The paper is then created and thoroughly bleached. In many events, certain amounts of paper are left unbleached. This unbleached paper may then be transformed into grocery bags and similar products.

 

Conclusion

 

As you can see from the information contained within this guide, there are many process control and fluid fundamentals that go into making paper products. Paper mills all around the country use this model or a similar model in order to create everything that is produced – ranging from tissue products to sheets of paper to recycled paperboard. Each process control must work in conjunction with another in order to ensure that all paper products are created appropriately.

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