Introduction

In North America, most woody biomass is transported by truck, whether it is logs, lumber, pulp chips, shavings, sawdust, wood pellets or wastewood / hog fuel.   Trucks are versatile, plentiful, easily scheduled and economical over short distances. However, woody biomass is light and bulky and when transporting large volumes over long land distances, truck transport becomes costly; rail transport can be significantly less costly to use.

Transporting biomass by railcar has its challenges. Woody biomass takes many forms, shapes and sizes and can be a difficult-to-handle material, particularly getting it out of containers such as railcars.

Wood chip transport by railcar became popular in North America in the 60’s and 70’s with the determination that properly prepared sawmill residuals could be used for pulp chips.  Several hundred specially designed wood chip railcars were constructed and most of these railcars are still in use today.

Pulp chips make up the bulk of woody biomass being transported by rail in North America.  Pulp chips tend to be fairly uniform in size, but knit together after transport in box cars.  And, the chip moisture content can vary significantly, which can be a problem in very cold climates.  Wood chips will self-heat from biological action and oxidation if left to sit for awhile, and snow that might be sitting on top, melts and freezes at the bottom of the railcar.

Wood pellets are also transported by rail, more so as the world demand for pellets increases.

In BC, pulp chips and wood pellets are routinely transported hundreds of kilometers by rail from the BC interior to the ports in Vancouver and Prince Rupert for trans-loading onto ships. Continue reading →

1  Introduction

Pulpmills are among the largest users of woody biomass and typically store and process huge volumes of wood chips prior to the pulping process. Storage volumes of 120,000 BDt (750,000 m³) are not uncommon.  The value of these chips is in the tens of millions of dollars, so mills have very specific requirements for storing wood chips to minimize fibre losses and maximize fibre recovery.

Things to consider when designing chip storage piles include: the material being handled, total required storage volume, practical live-storage volume, fibre aging, pile turn-over, dry fibre loss, chip degradation and breakage, dust and fire control, inventory management, the methods of pile-building and reclaiming, etc. Continue reading →

INTRODUCTION

It has been well documented that a Kraft wood pulp digester fed with a uniform chip size and a controlled volume of pins and fines provides a measurable improvement to the pulping process and pulp quality. Chips less than 7 mm thick pulp more completely than thicker chips, giving a uniform raw material for easily controlled pulping and bleaching. Additionally, removing the `pins’ and `fines’ from the digester feed improves operating performance.

Chip thickness screening (CTS) is a wood chip segregation and conditioning process that removes the overthick chips from the chip furnish and processes them either by slicing or crushing so that they can be uniformly cooked along with the screen accepts.

Most mills recognized the benefits of CTS in the early 1990’s and installed CTS systems; however, there were significant technological advances in the late 1990’s that many mills missed and still have not upgraded their equipment to the latest, most efficient technologies.

Although the actual pulping process improvements resulting from the application of CTS may vary from mill to mill, generally improvements can be found in the following areas:

• Improved wood utilization.
• Increased digester maximum production.
• Increased yield.
• Decreased digester alkali application.
• Recovery boiler solids reduction.
• Increased chip screens system availability.
• Less mechanical damage due to foreign materials such as rocks.

This article provides a brief description of the CTS process and summarizes the potential benefits. For excellent reference papers on chip thickness screening and the benefits, see the references included at the end of this article. Continue reading →

Introduction

“Plastic is Drastic” is the theme of an environmentalist group that is concerned about plastic contamination in the oceans.  It has also been a constant refrain heard for decades in pulp and paper mills throughout the world.

Miniscule tramp particles of plastic are present in most pulp and paper, and can cause numerous and costly operating problems not only for the pulp producer but also for the end-user. Plastic particles become embedded in the pulp and can cause the sheet to tear during processing or will become coated on equipment and cause streaks in the pulp.  Additionally, plastic particles embedded in paper will not accept printing ink.

Indeed, plastic contamination in pulp is a small but significant and costly problem in pulp manufacture; the amount of plastic in one small plastic pen can ruin 1,000 tonnes of pulp.  Generally, the industry has done a great job of controlling the amount of plastic used in a pulp mill, but plastic contamination is still a significant problem that mill operators keep a `keen’ eye on.

Unfortunately, there is no `magic bullet’, when it comes to eliminating plastic contamination.  Removing plastic from pulp is almost impossible, so the best solution is to prevent plastic from getting into the wood chips and pulp in the first place. Continue reading →