Money For Nothing And Your Chips For Free - TAPPI · “Money for Nothing and Your Chips for Free”, to the tune of $340,000.00 to $570,000.00 annually. Sandwich belt high angle

Money For Nothing And Your Chips For Free

Amy D. Duncan – Marketing Manager of Dos Santos International

Joseph A. Dos Santos – President of Dos Santos International

Abstract

The first sandwich belt installation in wood chips, and lyrics from the popular Dire Straits song “I Want My MTV”

inspired the title of this presentation.

At the Boise Cascade Mill in Wallula, WA, a 500 HP blowline was being used to elevate screened wood chips to the

digester. The problem: the blowline badly damaged the chips enroute, reducing many of them to pins and fines,

lowering the pulp yield and the digester’s uptime when pins bridged at the transfers.

Boise Cascade’s attention was drawn to the claim that sandwich belt high angle conveyors are very gentle on the

conveyed material. Indeed documented tests demonstrated that conveying the most sensitive grains along the

sandwich belt resulted in no damage of any kind. Such tests were repeated with wood chips and the results were the

same, no damage.

So, a sandwich belt high angle conveyor of only 60 HP was installed in place of the 500 HP blowline. According

the the customer, the savings that resulted exceeded Boise’s expectations.

They reported that the system paid for itself in six months to a year. Beyond the payback period, it was then

“Money for Nothing and Your Chips for Free”, to the tune of $340,000.00 to $570,000.00 annually.

Sandwich belt high angle conveyors can be found in applications around the world in coal, municipal waste, tunnel

muck, cement, sulfur, and several more. While noting a wide variety of applications in general, this paper focuses

on the suitability of sandwich belt high angle conveyors for the elevating duty from receiving (rail and truck load

out) to the wood yard to the digester. The paper also discusses the ability of the sandwich belt high angle conveyor

to eliminate problematic plant shut downs due to costly material degradation and product loss, reduction in high

energy consumption and dangerous dust. Finally, the paper highlights the suitability of the system in sub zero

temperatures and the potential to create a greener environment with a footprint reduction.

INTRODUCTION

Development of the sandwich belt high angle conveyor concept has evolved since its first introduction in the early

1950s. Over the approximate thirty-year period, until about 1979, significant advances had been few and had only

come in spurts. Such advances did not significantly build on past developments; rather they were independent

developments which soon reached their technical limitations.

The latest significant development of this technology, beginning in 1979, is the first to take a broad view of the

industries to benefit from high angle conveyors, and of all significant developments to date. As a result, these latest

developments know few technical limitations, address a broad range of application and offer a forum for further

logical development or evolution.

The Sandwich Belt Principle

Dos Santos sandwich belt high angle conveyors represent logical evolution and optimization of the sandwich belt

concept. The sandwich belt approach employs two ordinary rubber belts which sandwich the conveyed materials.

Additional distributed force on the belt provides hugging pressure to the conveyed material in order to develop

sufficient friction at the material-to-belt and material-to-material interface to prevent sliding back at the design

conveying angle.

Figure 1 is a realistic model of the belt sandwich. An ample belt edge distance assures a sealed material package

during operation even if belt misalignment occurs. This model also illustrates the interaction of forces within the

sandwich. The applied or induced hugging load is distributed across and along the carrying belt sandwich. Of that

hugging pressure, only the middle pressure hugs the material load while the outer pressure merely bears against the

material free edges of the belt. Both belt surfaces apply their frictional traction on the material. From this model,

one can calculate the required material hugging pressure that will ensure the material does not slide back due to the

tangential gravity loads. This is expressed by Equation 1:

Where: µ = µm or µ = µb, whichever is smaller

Equation 1

SANDWICH BELT HIGH ANGLE CONVEYORS

When investigated anew in the late 1970s, it was clear that the sandwich belt concept offered the greatest potential

for a cost effective, operationally appropriate high angle conveying system to address the broad needs of the mining

and bulk materials handling industries.

Following the extensive study of past sandwich belt conveyors, the governing theory and constraints, and

development of the governing design criteria, a broader scope effort was undertaken in 1982 to develop the first

sandwich belt high angle conveyor to meet these needs. The resulting sandwich belt high angle conveyors are truly

evolutionary in judiciously selecting and advancing features while avoiding the pitfalls of the past. They conform

entirely to the governing theory, to the constraint equations and to the development criteria.

These sandwich belts fulfill all established operational requirements. The profiles can conform to a wide variety of

applications.

Figure 1: Sandwich belt model

Advantages of a Sandwich belt high angle conveyor:

The use of all conventional conveyor hardware allows for high availability and low maintenance costs

The use of all conventional conveyor components permits high conveying speeds. Available belts and hardware up to 3000 mm wide make possible capacities greater than 10000 t/h.

High lifts to 300 m are possible with standard fabric reinforced belts. Much higher single run lifts are possible with steel cord or aramid fiber belts. High angles up to 90 degrees are possible.

Sandwich belts lend themselves to multi-flight conveying systems with self-contained units or to single run systems using externally anchored high angle conveyors. A system may be shortened or lengthened or the

angle may be altered for the requirements of a new location.

Smooth surfaced rubber belts allow continuous cleaning by belt scrapers or plows. Smooth surfaced belts present no obstruction to quick repair by hot or cold vulcanizing.

During operation the material is contained within the belt sandwich from loading to discharge. Well centered loading and ample belt edge distance result in no spillage along the conveyor length.

Select Sandwich-Belt Installations

Dos Santos sandwich belt high angle conveyors are well established in the industry with the first commercial unit

beginning operation in 1984. Since then more than 150 units have gone into operation throughout the world.

Table 1 lists only select installations that make the distinct case for wood chip handling:

Table 1

Unit # Location Wood Chips

Rate (t/h)

Angle

(°)

Belt Width

(mm)

Speed

(m/s)

Top/Bott

(kW)

Year

007 Western, USA 173 53 1219 2.03 22.4/22.4 1989

010 Western, USA 66 90 914 2.03 7.5/7.5 1991

014 Eastern Canada 375 53 1219 2.67 44.8/44.8 1991

053 Eastern USA 145 63 1067 1.8 22.4 1994

054 Western USA 435 50 1524 2.94 56/56 1995

071 Western USA 22 45 762 1.02 11.2 1997

074 Eastern USA 245 90 1524 2.29 44.8/44.8 1997

088 Western Canada 203 45 1372 2.61 22.4/22.4 2000

101 Eastern USA 54 90 1067 1.52 7.5/7.5 2012

Handling Wood Chips

We now consider applications from receiving (rail or truck unloading) to the wood yard to screening and to the

digester. Since 1989, sandwich belt installations have filled some important conveying and elevating functions of

the wood chip handling industry.

Haulage From Train Or Truck Load Out

Unit 010 of Table 1 is depicted in Figure 1. In this case wood chips are

received from trucks or trains and delivered to an open stockpile or to the

first stage screening house. The accepts are fed by conveyor onto the

sandwich belt for elevating to the metering bins. The second stage is

screening the chips go on to the thermo-mechanical pulp mill. This 914mm

“S” Shape vertical sandwich belt lifts 66

t/h of chips 15.5 m to feed the pulp mill.

Figure 1: Unit 010 in Western USA elevates

wood chips to the metering bins for

screening.

Figure 2: Unit 014 in Canada is an

L-Shaped system.

Screening

Unit 014 of Table 1 is depicted in Figure 2. It is a part of a chip thickness screening system located in Canada. This

1219mm (L-Shape) high angle conveyor lifts 229 tph of chips at a 53 degree angle.

To the Digester

Unit 007 of Table 1 is depicted in Figure 3, it is the first Dos

Santos sandwich belt unit to elevate wood chips and the first to

replace a pneumatic conveyor system.

Tests on high grade grains had demonstrated that there is no

measurable degradation of material using the sandwich belt high

angle conveyor. It was the claim of no damage that prompted

Boise Cascade to seek then purchase Unit 007 for their Wallula,

WA pulp mill.

The sandwich belt high angle conveyor is used to elevate wood

chips continuously from the screen house to the digester bin. In

most mills this task has been accomplished with blowline

technology. However, it has long been known that elevation of

wood chips in blowlines – with the necessary elbows or flat backs

– causes degradation of the chips, producing pins and fines.

When a good sized chip is carried through a blower system, it goes through a feeder, flat backs, then it is dragged

along the edge of the pipe, and then into a cyclone. Eventually you break that chip down into smaller, thinner chips

called pins and into fines.

Every time you do this, you lose yield to the digester. The smaller the material, the harder it is to run the digester.

There are several places in a digester where this small material can create problems.

Industry experts agree that these pins and fines create a variety of operating problems and reduced yield from the

digester. Additionally, pins and fines delivered to the digester can ultimately result in a small reduction of the

bursting strength and tearing resistance of the paper that contains these degraded fibers.

For these reasons, as well as others, and after careful review of the alternatives available, the choice was made to

replace the existing blowline elevation system with sandwich belt high angle conveyor technology.

Since starting up the high angle conveyor, it has been verified that there isn’t any degradation and run ability is

improved. Any real reduction in chip damage prior to the digester is important to the mill especially in today’s

competitive environment. There is also a substantial energy savings with the 44.8 kW (60HP) motor replacing a 375

kW (500HP) blowline.

As an example, if you use a cost of $60 per ton for wood chips and if you degrade five percent of those chips, then

three dollars worth of the chips are degraded. Depending on the tons used per hour in a continuous operation, the

money in degraded chips can become large. In a system that processes 190 tons per hour, 24 hours a day, 300 days

per year, that number is more than $4,000,000.

One continuous digester expert says that degraded wood chips will yield six percent less pulp from the digester. On

four million dollars worth of degraded wood chips (five percent in our continuous operation example) that

represents a loss of $240,000 worth of fiber or yield from the digester.

Between fiber and energy savings, the sandwich belt high angle conveyors can provide a full payback, including

installation, in about one year in cases where five percent degradation had previously existed. In an application that

had been operating at a ten percent detain payback would occur in little more than six months. This was proven in

unit 007 of Table 1.

Figure 3: The first Dos Santos sandwich belt unit to

elevate wood chips and the first to replace a

pneumatic conveyor system.

These calculations do not take into account the savings derived from reduced down time – fewer pins and fines, less

screen plugging, no flat backs to replace etc.

Dust

To be clear, the sandwich belt high angle conveyor is not dust

suppression, nor does it claim to completely solve that issue.

Dust suppression is an entirely different entity that is left up to

the actual experts in that field. However, the sandwich belt high

angle conveyor can certainly reduce dust emissions during the

processes in wood chip handling facilities.

Combustible dust is one of the most under-recognized hazards

in industrial facilities. While dust is present in just about every

manufacturing facility, when materials are being segregated as

they are in a wood chip plant, the particle size may increase the

risk for a combustible dust fire. Aside from the potential for a

dust explosion and fire, there is also the exposure to workers

inhaling the dust leading to breathing problems and lung

disease.

Because of the sandwiching of materials between the belts in the sandwich belt high angle conveyor, reduces dust

along the carrying path. Additionally, because the material is no longer being broken down by an abusive blow line,

it eliminates the variety of particle sizes that can in fact create a combustible dust hazard.

Cold weather

In extremely cold conditions, it can be expected that wood chip products will be stored in open piles that can be

covered in snow for much of the year, causing the product to be frozen. On a conventional troughed conveyor,

frozen wood chips have the tendency to slide back due to slick and slide of the frosted chips on the frosted belt

surface. Experts in this field recommend reducing the conveyor slope, reducing the load size and reducing the belt

speed. While logical solutions, these recommendations are costly to a mill by slowing down operations and reduce

output. These recommendations are made without the consideration of the sandwich belt high angle conveyor which

does not suffer any slide back tendencies within the sandwich.

Reduction of the conveyor slope creates an added expense for the mill. Aside from the additional real estate, it may

require covers around the low angled conveyor system, or even a large building enclosure depending on how

extreme the temperatures get. With the sandwich belt high angle conveyor, the ability to convey at a higher angle

not only saves on real estate, but creates a more cost effective means of housing the conveyor system within a

smaller, heated building. Such was the case for five sandwich belt conveyors that were installed for the DeBeers

diamond mines in Canada. Because of the hostile environment, the facilities had to be enclosed and heated. The

smaller footprint for the plant was determined to be the optimal way to minimize environmental impact and cost.

This led to the pursuit of the sandwich belt high angle conveyor because of its space saving features.

Figure 4: Material sandwiched between

the two belts help reduce dust emissions

and protect wood chips from damage.

If enclosing the conveyor system is not an option, the sandwich belt high angle conveyor still has advantages that do

not require a slowdown of operations. Because material is gently hugged between the two belts, it can still protect

the product from the elements. There is no concern that frozen chips will roll back or that wind gusts would blow

vulnerable product off the belt as in a lower angled troughed belt. There is also no concern of additional freezing

along the conveying path. Even if a sandwich belt high angle conveyor is not enclosed in a building, the protection

of the material between the belts eliminates the chance of additional freezing of material.

SUMMARY

Sandwich belt high angle conveyors have found wide use in the marketplace along with recognition of substantial

savings. The system can be found in varying applications along with the benefit of environmental considerations.

Furthermore, sandwich conveyors have proven their suitability for applications in chip handling and proven that

once all cost saving benefit is calculated, the phrase “money for nothing and chips for free” rings true. The

replacement of blowlines and low angle conveyor systems with the sandwich conveyor system allows for cost

savings and the protection of money making commodities. The possibilities with sandwich belts are far from being

fully exploited.

Figure 5: Reduced footprint with the sandwich belt high angle conveyor offers cost savings options,

especially in freezing temperatures.

Gateway to the Future

MONEY FOR NOTHINGAND YOUR CHIPS FOR FREE

MATERIALS HANDLING & ENGINEERING SPECIALISTS

A Legacy of Innovation

PRODUCT OF EVOLUT ION

Elevating wood chipswithSandwich BeltHigh AngleConveyors

• Derived from the covers belts of the 1950s• Hugging pressure to resist material slide back.

• Then the loop belts of the 1970s• First use of radial pressure due to tension

• Sandwich belt high angle conveyor• Use of all conventional conveyor parts• Low maintenance, high reliability

SANDWICH BELT HIGH ANGLE CONVEYOR

A sandwich belt high angle conveyor usestwo smooth surfaced conveyor belts, face‐to‐face, to gently, but firmly, containmaterial being carried, hence making steepincline and even vertical‐lift runs easilyachievable.

• Saves on real estate

• Saves on power and energy

• Saves on operation and maintenance cost

• Preserves the quality of the product

2

5

4

1

3

1

Loading onto bottom belt between skirts.

3

5

4

2

1

2

Top belt meets bottom belt to sandwich material

5

4

23

1

Curve 1, bottom belt hugs material against top belt

3

2

5

3

4

1

Inflection 1 between curves 1 and 2. At this point the conveyor can become a Snake or a GPS

4

2

4

3

5

1

5

Material discharge at head pulley

Sandwich Belt High Angle Conveyors use all conventional conveyorequipment including smooth surfaced rubber belts that can be continuouslyscraped clean. They feature the operating characteristics of conventionalconveyors; reliabe, low O&M costs.

SANDWICH BELT HIGH ANGLECONVEYOR ADVANTAGES

I M P O R TA N T F E AT U R E S

C A PA C I T YUnlimited; with wide belts at typical belt

speeds rates can exceed 10,000 t/h

S P I L L A G E F R E EMaterial is sealed between the belts with ample space.

H I G H L I F T SLifts beyond 300 m (1000’) are possible. High

angles of up to 90° are possible.

F L E X I B I L I T YFlexibility in planning and in operation allows for customization

• High power costs and energy consumption• Degradation of wood chips and reduced pulp yield• High wear and maintenance• Extreme cold conditions• Dust

MOST COMMON CHALLENGES

High power cost and energy consumption

• Very high power cost• More than 20 times that of a conveyor belt

•Low energy requirements

•Power goes directly into elevating the material

13

Degradation of wood chips and pulp yieldConveyed at 60° angle

Product 45.7m 91.4m 137.2m 182.9mSoybeans

Wheat

Seed Corn

NO DAMAGE

NO DAMAGE

NO DAMAGE

NO DAMAGE

NO DAMAGE

NO DAMAGE

NO DAMAGE

NO DAMAGE

NO DAMAGE

NO DAMAGE

NO DAMAGE

NO DAMAGE

Degradation of wood chips and pulp yield

High wear and maintenance

Extreme Cold Conditions

I lived through a fairly rough winter trying to feed hog fuel up an inclined belt and remembered thinking….That ain’t workin’

That’s the way you do it. There must be a better way…

DS 010

Sandwich Conveyorfor

Paper Mill, Western USA

Material ‐Wood Chips‐ Density ‐ 0.275 t/cu‐m (17.2 PCF)‐ Size ‐ 76 mm (3”) minus

Conveying Rate ‐ 65.3 t/h (72 STPH)Conveying Angle ‐ 90 degreesBelt Width ‐ 914 mm (36”)Belt Speed ‐ 2.03 m/s (400 FPM)Lift ‐ 15,500 mm (51’)Length ‐ 31,400 mm (103’)Drives

‐ Top Belt ‐ 7.5 kW (10 HP)‐ Bottom Belt ‐ 7.5 kW (10 HP)



Material ‐Wood Chips‐ Density ‐ 0.27 t/cu‐m (17 PCF)‐ Size ‐ 76 mm (3”) minus

Conveying Rate ‐ 173 t/h (191 STPH)Conveying Angle ‐ 53 degreesBelt Width ‐ 1219 mm (48”)Belt Speed ‐ 2.03 m/s (400 FPM)Lift ‐ 32,600 mm (107’)Length ‐ 49,300 mm (162’)Drives


DS 007


Pulp Mill, Eastern Canada




DS 014


Paper Mill, Eastern USA


Conveying Rate ‐ 145 t/h (160 STPH)Conveying Angle ‐ 63 degreesBelt Width ‐ 1067 mm (42”)Belt Speed ‐ 1.8 m/s (350 FPM)Lift ‐ 9,200 mm (30’)Length ‐ 16,700 mm (55’)Drive

‐ Bottom Belt ‐ 22.4 kW (30 HP)

DS 053


Paper Mill, Eastern USA



‐ Inner Belt ‐ 44.8 kW (60 HP)‐ Outer Belt ‐ 44.8 kW (60 HP)

DS 074

Sandwich Conveyorat

Pulp Mill, Western Canada

Material ‐Wood Chips‐ Density ‐ .24 t/cu‐m (15 PCF)



DS 088

DSI Snake Sandwich Conveyorfor

New Page Mill, Rumford, Maine, USA

Material ‐ Hog Fuel, (bark & wood waste)‐ Density ‐ 0.32 t/cu‐m (20 PCF)‐ Size ‐ 102 mm (4”) minus

Conveying Rate ‐ 54.4 t/h (60 STPH)Conveying Angle ‐ 90 degreesBelt Width ‐ 1067 mm (42”)Belt Speed ‐ 1.52 m/s (300 FPM)Lift ‐ 7,742 mm (27.6’)Length ‐ 16,642 mm (83.2’)Snake Drives

‐ Inner Belt ‐ 7.5 kW (10 HP)‐ Outer Belt ‐ 7.5 kW (10 HP)

DS 101

C‐SNAKE CONV. ELEVATION

Sandwich Conveyor Installations

DS 054





‐ Top Belt ‐ 56 kW (75 HP)‐ Bottom Belt ‐ 56 kW (75 HP)

22

• Chip quality; pulp yield

• Power and energy consumption

• Operating and maintenance

• Savings in improved plant availability

SAVINGS CONS IDERED

SANDWICH BELT HIGH ANGLE CONVEYOR

NO COST SOLUTION

QUESTIONS?

Amy Duncan, Marketing [email protected] Santos International

Thank you!

Documents

Money For Nothing And Your Chips For Free - TAPPI · “Money for Nothing and Your Chips for Free”, to the tune of $340,000.00 to $570,000.00 annually. Sandwich belt high angle