Unloading Wood Chips for the Production of Paper Pulp

Posted in: , on 25. Mar. 2015 - 21:11


Unloading Wood Chips for the Production of Paper Pulp

Even in today's "paperless" world, there continues to be a huge demand for paper. Paper is made from wood pulp, which is also used to manufacture a wide variety of products from diapers to particle board to textiles. The pulp itself is the cellulose, lignin and hemicellulose components of wood fibers, which are separated from one another through steaming, cooking or mechanical grinding processes. Most pulp is made from a mixture of sawmill residue, logs, wood chips and recycled paper, and it is interesting to note that practically all of the fibers that end up as pulp originally existed as trees.

The precursors to modern paper were made of papyrus or animal skins, the latter of which were dried to become parchment. This evolved into a pseudo-paper that was made of cotton and linen fibers. This form of paper could be made of rags and discarded clothing, which made it a lot cheaper to produce than expensive parchment. This form is still in use today, as paper currency is made of 75% cotton and 25% linen. It was not until pulping was invented in the 1840s that paper could be very cheaply made out of wood fibers.

The process of pulping is to extract the fibers from the source, and wood is a fairly sturdy, durable material. A variety of different methods that use either mechanical or chemical approaches are used to free the fibers from the wood. The cellulose fibers are linked together with lignin and hemicelluloses that have to be broken apart to release the valuable cellulose fibers.

A pulp mill takes the bulk raw materials and makes a first pass at extracting the fibers. Most such mills utilize waste wood particles and convert them into crude fiberboard, market pulp, air-dried pulp and other products. Lumber mills ship sawdust and wood chips to pulp mills to be converted into pulp.

Although three different chemical pulping methods have been invented, the one most commonly used today is called kraft pulping. Mechanical pulping is cheaper than chemical pulping, but it does not remove the lignins. Therefore, paper made from mechanical pulping processes tends to turn yellow and become brittle after just a short period of time.

Recycling plants re-pulp waste paper. The paper first has to be stripped of its ink and converted back to fibers, or de-inked pulp. Recycled paper pulping is a simple process once the ink has been removed because the fibers have already been released from the complicated wood structures. However, paper made entirely from recycled pulp is never as good in quality as paper made from fresh pulp. Most paper is currently made from a mixture of fresh and recycled pulp.

After pulping, the fibers are shipped in pulp form to factories for further processing into paper and other products. Pulp can be shipped wet or as dried rolls, bales or boards. Wet pulp is usually shipped as plastic-wrapped bales.

Bulk materials are constantly on the move during the production of paper, from the pulping plant to the paper mill. None of these processes can happen if the raw wood chips are not unloaded at the original pulping site in an efficient manner. Paper producers must be mindful of that when unloading wood chips that will become pulp.

When transporting bulk wood chips by rail, Heyl & Patterson manufactures rotary railcar dumper systems that are exactly what is needed. The rotary car dumper is a cost-effective, all-purpose workhorse, and is often the choice for high speed automatic dumping of both rotary coupled cars and random car applications. Cycle times for dumping can be as fast as 35 seconds per railcar, and tonnage throughput can reach 5,000-plus tons per hour.

Site conditions can often impact the wood chip unloading process, and Heyl & Patterson design engineers ensure a proper fit. Such key considerations as site configuration and topography, soil conditions, existing rail installations, types of railroad service, complementary unloading equipment and facility capacities can all come into play.

Heyl & Patterson provides production-enhancing refinements and options, such as built-in electronic weighing facilities, train holding devices and car ejectors. The company's Aftermarket Division also supports all clients with replacement parts, upgrades and retrofits for the life of their equipment -- regardless of the original manufacturer. Extended component life means lower maintenance costs and less downtime.

For more information about Heyl & Patterson rotary railcar dumpers and how they can benefit the pulp & paper industry, contact us or click here.

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