Improvements to CarBETe Dry Powder

Injector System

Critical Design Report

May 2005

Senior Design Team 05104

Edin Sehovic Mitsuru Ishihara

Martin Kuma

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Table of Contents Table of Contents ……………………………………………………… 2 Index of Figures ……………………………………………………….. 4 Index of Tables ………………………………………………………... 5 1 Needs Assessment 1.1 Introduction ……………………………………….……..…… 6 1.2 Product Description …………………………………………... 9 1.3 Scope Limitations ………………………………………..….. 10 1.4 Stakeholders …………………………………………………. 11 1.5 Key Business Goals …………………………………………. 11 1.6 Financial Parameters ………………………………………… 11 1.7 Preliminary Financial Analysis ………………..…………….. 12 1.8 Primary Market ………………………………………..…….. 12 1.9 Secondary Market …………………………………………..... 12 1.10 Order Qualifiers …………………………………………...… 12 1.11 Order Winners …………………………………………..…... 13 1.12 Innovation Opportunities ………………………………..….. 13 1.13 Formal Statement of Work …………………………...………13 2 Concept Development 2.1 Procedure ……………………………………………...…….. 14 2.2 Venturi Concept …………………………………………..… 15 2.3 Auger Concept …………………………………………….... 16 2.4 Snow Blower Concept …………………………………….... 17 2.5 Material Transfer Vacuum Pump ………………………..…. 18 3 Feasibility Assessment 3.1 Attribute Importance …………………………………….…... 19 3.2 Weighted Method Feasibility Assessment ……………….….. 19 4 Design Objectives and Performance Specifications

4.1 Design Objectives …………………………………………….. 20 4.2 Performance Specifications ………………………………....... 21 4.3 Evaluation Criteria ………………………………………..…... 23

5 Analysis and Synthesis 5.1 Powder Feed and Transport ………………………………..…. 24 5.2 Principle of Operation ………………………………..……….. 25 5.3 Holding Canister ………………………………………..…….. 26 5.4 Powder Collection Container ………………………………..... 28 5.5 Feeding Tube …………………………………………….…… 28 5.6 Design Integration and Prototype Testing ……………….…… 29

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5.7 Performance Assessment – Powder Mass Flow Rate …………. 30 5.8 Performance Assessment - Air Flow Rate …………………….. 32 5.9 Exit Velocity ………………………………………………...… 35 5.10 FLUENT Implementation ……………………………………. 36

6 Final Design

6.1 Bill of Materials ………………………………………… ……. 39 6.2 Container ………………………………………………………. 39 6.3 Vacuum Pump …………………………………………………. 40 6.4 Air Supply ………………………………………………...…… 40 6.5 Bleeder …………………………………………………………. 41

7 Conclusion ………………………………………………………….. 42 8 References …………………………………………………………... 43 9 Appendix ……………………………………………………………. 44

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Index of Figures Figure 1.1.1: Firetube Boiler …………………………………................ 6 Figure 1.1.2: Boiler Operation ……………………………………....….. 6 Figure 1.1.3: Typical Brock Turbulator ………………………………… 7 Figure 1.1.4: B.E.T. Automatic Tube Cleaner ………………………….. 7 Figure 1.1.5: Previous version of the CarBETe Dry Powder Injector System ……………………………… 8 Figure 1.1.6: Previous version of the CarBETe Dry Powder Injector System; (Illustration of the intended operation) ……………………. 8 Figure 2.2: Venturi Principle …………………………………………. 16 Figure 2.3: Auger Concept …………………………………………… 17 Figure 2.4: Snow Blower Concept …………………………………… 17 Figure 2.5: Vacuum Pump – principle of work ……………………… 18 Figure 4.2: Vacuum pump specifications ……………………………. 22 Figure 5.1.1: Vacuum pump photo …………………………………….. 25 Figure 5.1.2: Vacuum pump operation ………………………………… 25 Figure 5.3.1: Design layout used in powder dynamics assessment ……. 26 Figure 5.3.2: Tilt angle variation ………………………………………. 27 Figure 5.3.3: Holding canister – final design ………………………….. 27 Figure 5.5.1: Arrangement of bleeder holes in the

Feeding/Pre-mixing Tube …...…………………………… 29 Figure 5.7.1: Initial test setup ………………………………………….. 31 Figure 5.7.2: Final Test Setup …………………………………………. 32 Figure 5.8.1: Static Vacuum vs. Supply Pressure ……………………… 34 Figure 5.8.2: Vacuum Flow vs. Supply Pressure ………………………. 34 Figure 5.8.3: Air Consumption vs. Supply Pressure …………………… 34 Figure 5.10.1: 3-D Model of Vacuum Pump ………………………….. 37 Figure 5.10.2: Contour velocity at cross section (x=0, z=0) …………… 37 Figure 5.10.3: Path lines of flow from air inlet ………………………… 37 Figure 6.2.1: I-DEAS model of container ……………………………… 39 Figure 6.2.2: Funnel dimensions ……………………………………….. 39 Figure 6.4.1: Solenoid valve and switch Donated by sponsor ………………………………………. 41 Figure: 6.5.1: Air bleeder ¾” opening …………………………………. 41 Figure 7.0.1: Final Design I-DEAS model view 1 …………………….. 43 Figure 7.0.2: Final Design I-DEAS model view 2 …………………….. 43 Figure 9.0.1: Gantt Chart – rough schedule …………………………… 44 Figure 9.0.2: I-DEAS model - view 3 …………………………………. 45 Figure 9.0.3: Ideas model – container exploded view …………………. 45 Figure 9.0.4: Model view 4 ……………………………………………. 46 Figure 9.0.5: Model view 5 ……………………………………………. 46 Figure 9.0.6: Model view 6 ……………………………………………. 47 Figure 9.0.7: Model view 7 ……………………………………………. 47

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Figure 9.0.8: Funnel view 1 – I-DEAS model ………………………….. 48 Figure 9.0.9: Model view 8 …………………….……………………….. 48 Figure 9.0.10: Model view 9 ……………………………………………. 49 Figure 9.0.11: Funnel installed – I-DEAS model ………………………. 49 Figure 9.0.12: Transparent canister view – I-DEAS model ……………. 50 Figure 9.0.13: Funnel dimensions ……………………………………… 50 Figure 9.0.14: Holding Canister Cap – I-DEAS model ………………… 51 Figure 9.0.15: Vacuum Pump I-DEAS model – “Wire” view 1 ……….. 52 Figure 9.0.16: Vacuum Pump I-DEAS model – “Wire” view 2 ……….. 52

Index of Tables Table 3.1: Attribute importance ………………………………………… 19 Table 3.2: Weighted method ……………………………………….…… 20 Table 5.7.1: Powder mass flow rate for initial setup ……………………. 31 Table 5.7.2: Powder mass flow rate for the final setup …………………. 32 Table 5.8.1: DF 7-6 (¾“ I.D.) material transfer vacuum pump performance; Air only………………………………... 33 Table 5.9.1: Max. delivery pipe length ………………………………….. 35 Table 5.10.1: FLUENT results ………………………………………….. 38 Table 6.1.1: Bill of Materials …………………………………………… 39 Table 6.3.1: Vacuum pump performance data at 60 psi ………………… 40 Table 6.3.2: CarBETe mass flow rate …………………………………… 40

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1 Needs Assessment

1.1 Introduction

Increasing energy cost is one of the major problems in the world today, and this

problem will almost certainly worsen in the future. Therefore, it is crucial not to waste

energy and resources. As a result, the focus of many companies is to minimize the waste

of energy of numerous industrial and home applications. Fuel Efficiency, LLC, the

sponsor of this design project, is one of them. Fuel Efficiency, LLC manufactures

products that increase efficiency and reduce the operating costs of boilers (Figure 1.1 and

1.2) and other heat transfer equipment. The company is located midway between

Rochester and Syracuse New York and it is best known as the manufacturer of Brock

"Fuel-Saver" Turbulators for firetube and cast iron sectional boilers.

Source: www.fuelefficiencyllc.com

Figure 1.1.2: Boiler Operation

Figure 1.1.1: Firetube Boiler

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Figure 1.1.3: Typical Brock Turbulator

During regular operation of a boiler there is a residual build-up in the tubes when using

fuels such as wood, coal and heavy grades of oil. Sulfur and Vanadium in the built up

soot cause pitting and corrosion of boiler tubes and baked-on soot eventually causes

boiler tube failures. To minimize this problem and increase boiler tube life Fuel

Efficiency came up with the B.E.T Automatic Tube Cleaner which uses timed puffs of

compressed air to clean the firetubes from soot. The tube cleaning system is operated by

programmable controller that electrically activates solenoid valves thereby generating

short bursts of air which clean the boiler tubes from soot (see Figure 1.4).

Figure 1.1.4: B.E.T Automatic Tube Cleaner (Source: www.fuelefficiencyllc.com)

In addition to the B.E.T Automatic Tube Cleaner there is another piece of

equipment called CarBETe Dry Powder Injector System (Figure 1.5) which is also

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designed to reduce soot formation in the boiler tubes. Detailed description on how the

injection system functions as well as the problems with the previous design are described

in the section 1.2, Product Description. This powder injection system was initially built in

1980 and due to performance problems and reliability issues Fuel Efficiency, LLC

discontinued the production of this product in 1986.

Figure 1.1.5: Previous version of the CarBETe Dry Powder Injector System

Figure 1.1.6: Previous version of the CarBETe Dry Powder Injector System; (Illustration of the intended operation)

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1.2 Product Description

The CarBETe dry powder injector is a system that delivers the powdered

combustion catalyst through a delivery tube into the firebox area of an industrial boiler.

The CarBETe combustion catalyst is a powder that drives the combustion reaction in the

combustion area of the boiler, so that oxygen is used more completely. It improves the

oxidation of residual oil to produce a cleaner flame and decreases soot formation as much

as 65% by weight, according to Fuel Efficiency, LLC. By decreasing soot formation

CarBETe saves fuel because soot accumulation in the firetubes will waste more of the

fuel. CarBETe also lowers stack emissions of toxic sulfur dioxide and at the same time

increases the amount of carbon dioxide, which is evidence of a more complete

combustion, according to Fuel Efficiency, LLC. CarBETe may be used in any type of

boiler fired with heavy oil (number 4, 5 or 6 grades of oil). It can be also used in

combination gas/oil fired boilers using residual oil or even with solid fuels, such as wood

and coal. The powder is injected into the firebox area of a boiler, either directly into the

flame, in a power burner situation, or onto a solid fuel burn pile.

The system prototype being designed is to be a stand-alone unit but it will mainly be used

in conjunction with the B.E.T Automatic Boiler Tube Cleaning System and share the

same controls. Programmable control will sequence the solenoid valve that creates short

bursts of air which transfer the powdered catalyst into the boiler. The CarBETe catalyst

is a chemical in powder form and is approximately 90% talc. It is relatively heavy and in

the current design it tends to get clogged within the injection system at various points,

primarily in the holding canister, according to Fuel Efficiency. The system our team will

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design shall eliminate clogging problems and provide a reliable operation. Additionally,

very high temperatures that could reach up to 3000 º F must be considered when

designing the end of the tube that will be at the boiler.

1.2.1 Additional details about the CarBETe powder

• Components: Talc (non-asbestos) ~ 90%

Calcium Carbonate ~ 5%

Tricalcium Phosphate ~ 5%

• Solubility in water: Low

• Appearance and Odor: Fine, gray, powder with slightly musty odor and “slippery

feel”

• Not Flammable

• Incompatible with: Metal oxides, aluminum and magnesium metals and strong acids

1.3 Scope Limitations

The prototype of the CarBETe Dry Powder Injection System along with the

accompanying work shall be completed in 20 weeks and presented to the primary

customer by May 2005. Prior to that, the system shall be extensively tested and calibrated

for optimal usage. Combustion catalyst provided by the sponsor shall not be changed,

clogging must be eliminated and means of monitoring the level of powder in the

container should be provided if time permits. There is no budget limit set by the sponsor

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at this point; however, the prototype shall be cost effective. Resources available at the

sponsor’s site will be used first before acquiring outside materials and equipment.

1.4 Stakeholders

The primary stakeholder for the CarBETe Dry Powder Injector System is the Fuel

Efficiency, LLC. Secondary stakeholders are potential buyers, boiler operators and

maintenance workers.

1.5 Key Business Goals

Fully functioning prototype of the system shall set the basis for the next

generation of CarBETe powder injectors. The return of investment will be accomplished

in a short period of time and profits will be realized. The next step of the business plan,

which is the selling of the powdered combustion catalyst, will be made possible.

1.6 Financial Parameters

The budget for the project is not fixed but it is unofficially capped at $1000.

Materials and fabrication needs will be identified in more detail after the requirements

and specifications for the system are determined. However, since the customer will

develop the controls for the system the cost associated with electronic equipment and

sensors will not affect the team’s budget.

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1.7 Preliminary Financial Analysis

The main cost sources will most likely be the airflow regulation equipment and

pipes manufactured to tight tolerances needed to achieve smooth inner surfaces.

Fabrication shall be done by the senior design team and if necessary by the sponsor

which reduces fabrication cost.

1.8 Primary Market

The primary market is Fuel Efficiency, LLC.

1.9 Secondary Market

Regular households with small size boilers that could use a similar system where

an air compressor would blast the catalyst into the boiler.

1.10 Order Qualifiers – Minimum required performance

The following critical performance parameters are necessary for a successful project: • Develop a design that eliminates clogging • Increase performance by designing a reliable system • Provide means of monitoring powder level in the holding canister

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1.11 Order Winners – Desired Performance

Following goals shall be accomplished if time and schedule permit:

• Incorporate an adjustable powder-delivery system that is precise and easy to operate

• Optimize delivery adjustments and monitoring through testing and simulation

1.12 Innovation Opportunities

Potentially, the system could incorporate flow sensors in the piping system and

optical sensors in the container area to optimize controls. The introduction of an

advanced air drier system would increase reliability and eliminate moisture in the

pressurized air.

1.13 Formal Statement of Work

The team shall provide one fully functional prototype of the system by May 2005.

The prototype system shall transport the combustion catalyst from a holding canister into

the firebox area of the boiler. The main components of the system will be as follows:

holding canister, feed mechanism and piping. The main goal of the prototype is to

eliminate clogging of the powder in the system and to provide means of monitoring the

powder level in the holding canister. The team will not design the controls for the

prototype system. The system shall be a reliable stand-alone unit that is adaptable to wide

range of applications.

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Agreed

By: Edin Sehovic Date: 2/17/05 (Design Team Member)

By: Mitsuru Ishihara Date: 2/17/05 (Design Team Member)

By: Martin Kuma Date: 2/17/05 (Design Team Member)

By: Alan Nye Date: 2/17/05 (Faculty Mentor)

By: Joe Connelly Date: 2/17/05 (Customer Representative)

2 Concept Development

2.1 Procedure

The senior design team has conducted a brainstorming session to prepare a long

list of ideas. This session generated twenty different ideas that are recorded in the

engineering design guide binder. Using a consensus building technique the long list of

ideas was reduced to the short list of concepts that were then developed further. The

team selected most promising concepts by taking into account the problem of clogging

and the desire to have minimal number of complicated moving parts that could

challenge the reliability of the design. The three concepts selected were ‘Venturi’

concept, ‘Auger’ concept and ‘Snow Blower’ concept. Using a group-drawing

technique these three ideas were prepared on a conceptual level. At that point each

team member chose one of the concepts and developed a formal set of sketches

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together with a preliminary Bill of Materials that could be used further in the feasibility

assessment to compare the three designs. The formal forms of the three selected

concepts are included in the EDGE binder. Below are some detailed descriptions of the

concepts from the short list.

2.2 Venturi Concept

The main idea behind a venturi nozzle is to create a low- pressure region in a pipe

(see figure 3). By reducing the diameter of the pipe the velocity of the fluid flowing

through increases whereby the pressure decreases. This principle is easily explained by

the Bernoulli equation. This application was attractive to the senior design team

because of its simple nature and absence of any moving parts.

When the lower pressure region, generated in the pipe, is connected to a completely

sealed container that is at a higher pressure, the air in the container tends to flow

towards the lower pressure region. Thereby, the powder in the container is carried by

the air into the system and transported further. Materials and parts needed to

implement this design are pipes and tubes, container, air connectors, and the venturi

nozzle.

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Figure 2.2: Venturi Principle

2.3 Auger Concept

After extensive research and contact with the faculty, the team was able to

establish the auger concept that is robust in nature and less susceptible to the clogging

of the powder in the canister. The auger would be mounted at the bottom of the

container and would go through a feeding pipe into the air pipe (see figure 4). This

design requires a motor and a shaft that would turn the auger thereby moving the

combustion catalyst by pushing it through the pipe. Additional parts include pipes,

connectors and canister.

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Air flow

Figure 2.3: Auger Concept

2.4 Snow Blower Principle

This design would not require a feeding pipe but would push the powder directly

from the canister into the air pipe, where the air would blow it through the pipe until it

enters the combustion chamber of the boiler (see figure 5). Motor, shaft and a

combination of two augers would be needed, as well as a specially designed container.

Container with power

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Figure 2.4: Snow Blower Concept

Auger x2 w/ shaft in middle

Air pipe

2.5 Material Transfer Pump

Material transfer pump is a well-developed device widely used in various

industries. It is a vacuum pump that is capable of transferring solid materials ranging

from fine powder to bulk objects size of a tennis ball. It has no moving parts, does not

require maintenance, and only requires compressed air to operate.

The mechanism of the pump is simply based on the venturi concept, creating low

pressure or vacuum by increasing flow velocity. The geometric design of the pump

creates higher flow velocity inside to obtain vacuum in a pipe. The only difference

with the ordinary venturi pipe is the locations of air inlet port and air suction port. The

pump is designed to transfer materials in linear path instead of a path with some angle

change in path direction. To better understand the principles of the pump, an

simplified illustration is shown below.

Compressed Air

Mixed Flow of Air and Material

Suction Air Outlet

Path of Path of Compressed

High Velocity – Low Pressure Figure 2.5: Vacuum pump principle of work

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3 Feasibility Assessment

3.1 Attribute Importance

The final three concepts were subjected to a set of question established to

determine the positive and the negative attributes of each concept. First, the relative

weight of each attribute was evaluated as illustrated below in table 3.1.

Bas

e Li

ne

Snow

Blo

wer

Aug

er

Ven

turi

Mat

eria

lTr

ansf

er P

ump

Rel

ativ

e W

eigh

t

T1 sufficent skills 3.0 3.0 4.0 4.0 5.0 7.6%T2 availablity of equipment 3.0 2.0 3.0 4.0 5.0 1.5%E1 production cost 3.0 1.0 2.0 3.0 2.0 9.1%E2 Budget provided 3.0 3.0 3.0 3.0 3.0 13.6%E3 Future Prospects of the product 3.0 3.0 3.0 3.0 4.0 4.5%S1 Team's time constraints 3.0 2.0 2.0 2.0 2.0 13.6%P1 Feeding powder 3.0 4.0 4.5 4.5 5.0 16.7%P2 Monitoring powder level in the container 3.0 3.0 3.0 4.0 5.0 10.6%P3 Adaptable to other appliction 3.0 3.0 3.0 2.0 4.0 3.0%P4 Adjustable delivery system 3.0 3.0 4.0 4.0 5.0 3.0%P5 Number of moving parts 3.0 2.0 2.0 3.0 3.0 9.1%P6 Number of main components 3.0 1.0 2.0 2.0 3.0 7.6%

Weighted Score 3.0 2.6 3.0 3.2 3.6Normalized Score 82.5% 71.3% 81.5% 89.0% 100.0%

Table 3.1: Attribute Importance

3.2 Weighted Method Feasibility Assessment

The most important parameter is the performance of the feeding mechanism as

seen in the following two tables below.

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Table 3.2: Weighted Method

4.0 Design Objectives and Performance Specifications 4.1 Design Objectives

The design objectives of the Carbete injector system, comprising of the canister

containing the powder, the pipes, the vacuum pump and the regulatory valve with an

attached filter must be met, taking into account the powder that is supposed to flow

through the pipes. The canister should be made of PVC instead of cast iron to avoid

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particles of the powder sticking to the rough interior of the pipes. There should be a

filtering device to filter out moisture or water that otherwise can react with the powder to

cause clogging.

Since the need for this design was stimulated by the company’s plans to sell the Carbete

powder, and not the delivery system, incorporating less moving parts is important design

objective. Also, materials that can withstand temperatures (3000oF) about that of the

combustion chamber must be used, especially, in parts closer to the chamber. More so, as

the entire project is anchored by the effective sell of the carbete powder; our design

should be able to determine the quantity of powder blown, given pressure, time and the

diameter of the pipes. The inside diameter of the canister must be 4 inches wide and a

height of 2 feet. Finally, the ejection system should be able to eject powder into the

combustion furnace via a pipe of minimum length 10feet.

4.2 Performance Specifications

- The CarBETe injector system shall transport a small amount of powder through a small diameter tube ranging from one to ten feet in length.

- The system will be activated once an hour and shall transfer approximately five

grams of powder per blow sequence, which is comparable to the amount that fits into a regular soda bottle cap.

- The amount of powder being transferred shall be adjustable.

- The system must not clog up at any one of its sections.

- The end of the delivery tube that will be at the boiler must be able to withstand

high temperature, which could theoretically reach 3000°F.

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- The system shall be able to be easily modified in order to adapt to wide range of applications.

The vacuum pump used is a material transfer pump from Vaccon Co. Inc with

dimensions tabulated below.

Model I.D

A

B C D E F G H (NPTF)

I

DF 7-6 3/4 2 1 1/4 7 1/2 1 1/2 2 4 1 3/8

Figure 4.2: Vacuum Pump Specifications (www.vaccon.com)

The delivery system must also meet several performance criteria. In order to ensure

customers would continue to purchase the powder, there should be no clogging

whatsoever in any of the system’s compartments. In addition, customers should be able to

know how much powder they have left in the canister at a specific time and at a specific

pressure. The amount of powder delivered into the combustion chamber must be

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adjustable at different pressures. For safety issues, canister should be able to stand alone

without toppling over at the slightest push. The system should also be able to perform

consistently and smoothly at different pressures within a reasonable range with the aid of

a pressure regulator.

All units in the analysis must be in US customary units. Vacuum pump bought must

operate within the pressure requirements of our design.

4.3 Evaluation Criteria

Before installation of the product, and before shipping to the customer, it must

meet several evaluation criteria. The entire system would be modeled in Fluent,

simulation software to predict any current or future flaws as well as performance. Stress

and fatigue calculations would ensure that our NTP fittings and welded part if any does

not break under high pressures, such as 100 PSI.

Actual testing, under several different temperatures and pressures would be done to

confirm that the powder does not clog. The System must be able to deliver powder

through a 10 feet pipe, no back pressure can be generated from the combustion chamber,

total elimination of moisture in the compressed air and the entire system must be easy to

assemble and disassemble by the customer. There should be no necessary lubrication by

customer, and finally, the amount of powder delivered per minute should be precisely

known under the different pressures, and materials must be corrosion resistant.

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5.0 Analysis and Synthesis

5.1 Powder Feed and Transport

The apparatus used to transport the catalyst was a high flow vacuum pump for

material transfer (Fig. 1). It was chosen after extensive research of different powder

transfer methods because it provides a dual function. First, the vacuum pump creates a

vacuum on the ‘vacuum inlet’ which causes suction that serves as a feeding mechanism

for the powder. Second, it creates a high speed flow on the ‘exhaust output’ that is able

to transfer the powder over the required distances. The pump’s capability to create

instantaneous vacuum flow and high air velocity combined with its straight through,

smooth bore design allows the powder to pass directly through the unit without

interference or clogging.

Previous design incorporated a rotary actuator that was placed below the holding

canister for feed control. When the actuator would open the powder driven by gravity

would flow into the main transport tube and a compressed air burst would blow it

through a tube into a boiler. However, rotary actuators are at least two times more

expensive then the most expensive vacuum pumps. Additionally, rotary actuators are

bulky, have moving parts and require maintenance whereas vacuum pumps have no

moving parts, require no maintenance and their compact design facilitates placement

close to the work area for maximum efficiency and ease of installation.

The size of the vacuum pump chosen for this project was ¾ inch in diameter. The

decision to go with a relatively big diameter was due to the fact that the previous

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design built by the sponsor of this project incorporated tubes with a size of ⅜ to ½ of

an inch. However, that system was clogging, so in order to eliminate at least one

possible cause of clogging in the new design it was decided to go with a ¾ “ diameter.

Figure 5.1.1: vacuum pump

Material Transfer Vacuum Pump

Vacuum

3/4" Steel Pipe3/4" Tube

Compressed Air Inlet3/8" pipe

Exhaust

Figure 5.1.2: Vacuum pump operation

5.2 Principle of Operation

Compressed air is fed into an exterior annual ring that has six orifices leading into

the main tube of a transducer. As the compressed air exits from the orifices its velocity

increases to very high speeds. The air forced into the center of the tube rotates with a

twisting motion thereby creating cyclonic flow which creates a powerful vacuum

capable of drawing materials into, and through the transducer.

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5.3 Holding Canister

The CarBETe holding canister was the part of the system that was most

susceptible to clogging because the powdered catalyst tends to get packet after sitting

in the container for long time. Additionally, the transition area between the canister and

the feeding tube is critical because the powder must be able to flow and not get stuck

when leaving the holding canister. However, flow characteristics of CarBETe were

almost impossible to obtain theoretically due to lack of expertise on powder chemistry

and physical properties of CarBETe. Thus, the optimal container geometry was

obtained experimentally.

The first container was built out of Plexiglas and it was in a shape of a box. Plexiglas

was used in order to enable visual assessment of powder flow in the container. The

canister was connected to the rest of the injector system as shown in Figure 3 and

powder dynamics were observed and recorded through experiments. The bottom of the

canister was tilted in order to obtain an optimal angle at which the powder would flow

(see Figure 5.3.1)

Holding Canister

To boiler

Material Transfer Vacuum Pump

3/4" Steel Pipe

Compressed air inlet3/8" pipe

3/4" Transparent Tube

Plexiglas

Powder

Figure 5.3.1: Design layout used in powder dynamics assessment

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Powder

Bleeder Hole

φ

Figure 5.3.2: Tilt angle variations

After extensive testing the results showed that the angle φ has to be very high,

around 50 deg, in order to maintain continuous flow.

The box shaped holding canister made out of Plexiglas was a good first step but after

several test we realized the vacuum pump only sucked the powder in the middle

portion of the Plexiglas container. It was apparent that the shape of the canister did not

allow continues flow of the powder to its bottom, hence, creating no contact between

the powder and the surface of the suction portion of the pump. Also, taking into

account manufacturing and economic considerations a final decision was made to build

a canister from a 4” diameter PVC pipe which is cheaper and easier to modify than the

Plexiglas box. The cylindrical shape, allows the powder to flow to the bottom freely

and smoothly. This new design necessitated a new arrangement of the system as

shown in figure 5.

F

unnel4" Pipe

Powder

Cap

Figure 5.3.3: Holding Canister – Final Design

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One more step was taken to improve the flow of the powder, and that was the

implementation of a steep funnel into the bottom portion of the canister (Fig. 6). The

angle of the funnel used, measure vertically, changes from 0° at the tube wall to 30° at the

upper section of the funnel to 10° at the lower section of the funnel.

5.4 Powder Collection Container

The collection container in the prototype system was incorporated in place of a

combustion chamber of the boiler which would be used in a real situation. The boiler’s

combustion area is under atmospheric pressure as was the case with the prototype’s

collecting container. Therefore, the performance of the system will not deviate when

connected to a real boiler. The container is made of PVC instead of cast iron as in the

original design. Aside from the fact that PVC is lighter than cast iron, it also has a much

smoother inner surface which would enhance a smooth flow of the powder.

5.5 Feeding Tube

The feeding tube connects the holding canister with the vacuum pump, thus, it is

critical to the powder’s flow rate control and clogging factors. First lesson learned in the

first experiment run by the student team was that the feeding tube would clog if there

were no bleeder holes drilled in the tube. By enabling air to enter the tube the vacuum

pump was able to suck the air into the tube and mix it with the powder before

transporting the mixture through the system. The number, size and arrangement of the

holes were determined experimentally. The results showed the best configuration is the

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one where holes are arranged as shown in Figure 7 below. Even with this bleeder holes

working perfectly, we found out that it could only work efficiently for limited volumes of

powder. Further experimentation showed that by increasing the volume of air mixing

with the powder just before the inlet of the pump the better the delivery and reliability.

Hence, we made a bigger bleeder just before the T of the pipe thereby completely

engulfing the powder in air. This yielded the best results as would show in consistency of

the mass flow rate. The tube material used in the prototype was clear plastic tubing,

however, for the production version of the system an iron or steel pipe of same

dimensions should be installed in place of the plastic tube due to a high temperature

environment.

20

20

15

Figure 5.5.1: Arrangement of bleeder holes in the

Feeding/Pre-mixing Tube; Top View (left),

Side View (right); Dimensions in millimeters

5.6 design Integration and Prototype Testing

Another important consideration was the high temperature that the end of the

delivery tube would be exposed to. Since the material of choice for the pipe was steel

there was no problem because steel can be exposed to temperatures up to 3000 °F.

After the holding canister design was modified to perform consistently, the performance

29

of the injector system was based almost entirely on the vacuum pump which was driving

the whole system. The performance of the vacuum pump was assessed by testing the

same in two different configurations.

5.7 Performance Assessment – Powder Mass Flow Rate

The first configuration was designed to experimentally determine the mass flow

rate of CarBETe through the injector system prototype. Attempts to determine the mass

flow rate of powder theoretically were rather unsatisfactory because the ratio of

powder and air in the mixture depends on numerous factors that were not readily

available. Hence, the mass flow rate of CarBETe was determined experimentally by

measuring the time needed for the system to transport one pound of CarBETe from the

holding canister to the collection container. The supply pressure was varied from 60 psi

to 10 psi in increments of 10 psi. Higher pressure could because the maximum pressure

allowed in the lab is 60psi. At each supply pressure level three time measurements

were obtained and the average was used in calculating the mass flow rates. Results are

shown in Table 1.

As evident from Table 1, the mass flow rate of powder decreased as the pressure

decreased. At the pressure of 10 psi the vacuum level was not strong enough for any

suction to take place. At 15 psi, the powder was transported although the performance

was on the threshold. Therefore, for the CarBETe injector system comprising of a DF

7-6 series vacuum pump, the minimum supply pressure must not be less than 15 psi

(103.42 kPa).

30

The experimentally obtained data that establishes a relationship between the supply

pressure and powder mass flow rate was the main goal in terms of controlling the

amount of CarBETe injected into the boiler. However, it is important to remember that

the performance data was only for this particular vacuum pump model with a ¾” I.D.

In order to assess the performance of other vacuum pumps that might be used in

different configurations of the injector system we modeled the performance data using

air only. Next section of this report discusses that in detail.

Supply pressure

Weight of Powder Time

(PSI) (lbs) (sec) lb/sec grams/sec404543

avg. 42.7455045

avg. 46.7505055

avg. 51.7606060

avg. 60606560

avg. 61.79080100

avg. 9010 1 N/A* N/A* N/A*

* Suction below threshold - no powder transfer

0.016 7.4

0.011 5.0

0.019 8.8

0.017 7.6

20

15 1

1

1

1

40

30

1

Mass Flow Rate of Powder

1

60

50

0.023 10.6

0.021 9.7

Holding Canister

Material Transfer Vacuum Pump

3/4" Steel Pipe

Powder Collection CanCompressed air inlet3/8" pipe

3/4" Transparent Tube

Table 5.7.1: Powder mass flow rate for initial setup Figure 5.7.1: Initial test setup

31

p

Supply ressure

Weight of Powder Time

(PSI) (lbs) (sec) lb/sec grams/sec

252525

avg. 25.09080120

avg. 96.710 1 N/A* N/A* N/A*

* Suction below threshold - no powder transfer

15 1 0.010 4.7

Mass Flow Rate of Powder

20 - 60 1 0.040 18.0

Table 5.7.2: Powder mass flow rate for the final setup

Powder Collection Can

Material Transfer Vacuum Pump

3/4" Steel Pipe

Compressed air inlet3/8" pipe

3/4" Transparent Tube

Holding Canister

"T"

Figure 5.7.2: Final Test Setup

5.8 Performance Assessment – Air Flow Rate

The second configuration involves only air going through the pump. The data was

determined experimentally by the vacuum pump manufacturer for fifteen different

pump sizes and configurations. However, complete performance data at different air

supply pressures is only available for the DF 7-6 model used in the prototype system.

For other vacuum pump sizes the data is limited to the case where the supply pressure

is 80 psi. To determine the performance of other pumps with different sizes and

32

configuration it was necessary to first correlate the relationship between the

compressed air inlet, vacuum inlet and exhaust outlet for the DF 7-6 vacuum pump

used in the prototype.

First, mass conservation was applied with the assumption that the flow through the

pump is incompressible and steady. The continuity relation is shown in Equation (1).

outvacin mmm &&& =+ Eq. (5.8.1)

Since incompressible air is assumed Equation (1) is reduced to

outoutvacvacinin AVAVAV =+ Eq. (5.8.2)

VAQ = Eq. (5.8.3)

All areas were known because diameters were given. Also, from the flow rates given in

Table 2, for 60 psi supply pressure, the suction air velocity Vvac was determined from

the vacuum flow rate and the compressed air inlet velocity was found from the air

consumption flow rate. Standard ambient conditions were assumed for all calculations,

namely pressure is 1 atm or 14.7 psi, temperature is 20°C or 68°F and relative

humidity is 36%. Equation (2) was then solved for Vout, so that all variables were

known (Table 2). Sample calculation is shown below, Q = VA.

Supply Pressure (psi)

Vacuum Level (Hg")

Vacuum Level (psi)

Vacuum Flow (SCFM*)

Air Consumption

(SCFM*)0 0.0 0.0 0.0 010 1.5 0.7 51.7 1020 3.0 1.5 73.0 1830 4.5 2.2 87.8 2740 5.7 2.8 90.5 3750 6.7 3.3 97.0 4360 7.8 3.8 97.1 4670 8.6 4.2 98.2 4780 9.5 4.7 98.2 48

Table 5.8.1: DF 7-6 (¾“ I.D.) material transfer vacuum pump performance; Air only. [2]

33

Static Vacuum Level vs. Supply Pressure

0.02.04.06.08.0

10.0

0 20 40 60 80 100

Supply Pressure (psi)

Stat

ic V

acuu

m L

evel

("

Hg)

Vacuum Level -Static ("Hg)

Figure 5.8.1: Static Vacuum vs. Supply Pressure

Vacuum Flow vs. Supply Pressure

0.020.040.060.080.0

100.0120.0

0 20 40 60 80 100

Supply Pressure (psi)

Vacu

um F

low

(scf

m)

Vacuum Flow (scfm)

Figure 5.8.2: Vacuum Flow vs. Supply Pressure

Air Consumption vs. Supply Pressure

0102030405060

0 20 40 60 80 100

Supply Pressure (psi)

Air C

onsu

mpt

ion

(scf

m)

Air Consumption(scfm)

Figure 5.8.3: Air Consumption vs. Supply Pressure

Eq. (5.8.4) sm

sft

ftAQ 418

)(60min ==

34

inin

ft

Vin

inin 127

12458.0

secmin146

22

222

3

⎟⎠

Eq. (5.8.5)

Eq. (5.8.6)

⎞⎜⎝⎛

⎠⎝==π

⎟⎞

⎜⎛

ssftA161528

(==

mft

inin

ftQV

vac

vacvac

124)75.0

sec60min1

min1.97

22

222

3

⎟⎠⎞

⎜⎝⎛

==π

⎟⎠⎞

⎜⎝⎛

ssin

ftin

ft

AmftQV

out

outout 237777

124)75.0(

secmin1

22

222

3

==⎟

60min143

⎠⎞

⎜⎝⎛

⎟⎠⎞⎛

==π

⎜⎝

5.9 Reasons for Calculating the Exit Velocity

The exit velocity of the pump was calculated in order to determine whether or not

the pump was capable of delivery the powder through the 10 feet pipe. This can be

determined using the Bernuolli equation with a head loss along a streamline.

The head loss equation states that along a streamline ρ

PcP −3 = HL where P3 is the

exit pressure and Pc the pressure in the combustion chamber.

Head loss is also defined as HL=Dvfl

∗

−

2 where f is the friction factor, l the length of

the pipe (10feet long), the average velocity and D the inside diameter of the pipe. −

v

Eq. (5.9.1)

Eq. (5.9.2)

Eq. (5.9.3)

Table 5.9.1: Max. delivery pipe length

DVfLPPH L

2

=2

21−ρ

Supply pressure (PSI) Maximum delivery pipe length (ft)

60 25.3

380000Re ==ρVD

−

µD

50 20.3

40 15.1

30 10.2

20 5.1

Supply pressure (PSI) Maximum delivery pipe length (ft)

60 25.3

50 20.3

40 15.1

30 10.2

20 5.1

Supply pressure (PSI)Supply pressure (PSI) Maximum delivery pipe length (ft)Maximum delivery pipe length (ft)

6060 25.325.3

5050 20.320.3

4040 15.115.1

3030 10.210.2

2020 5.15.1ρ2

2Vf

pD∆L =

35

5.10 FLUENT Implementation

The values obtained theoretically in the previous section were used to set up a

simulation in the CFD software FLUENT. By simulating the configuration of the vacuum

pump, as used in the prototype, it is possible to change the parameters such as the inner

diameter, pressure, velocity and flow rates to determine the performance of other pumps

available on the market. By looking up a vacuum pump (must have published flow rates

for minimally two out of three ports) at any supply pressure in a catalog or the web that

seems to fit a particular injector system application it is possible to determine what the

performance specifications are for that particular material transfer vacuum pump.

Pressures, flow rates and air velocities can be obtained by changing the parameters in the

FLUENT simulation in order to determine if that pump is feasible for the given situation

and requirements.

At this point the simulation was optimized for only one application, namely, the DF 7-6

pump used in the prototype system. However, performance assessment for additional

pump sizes is in works and will be available in the Senior Design II Final Report.

36

Air Inlet

Vacuum Inlet

Outlet

Figure 5.10.1: 3-D Model of Vacuum Pump (left); Internal Volume (right)

Figure 5.10.2: Contour velocity at cross section Figure 5.10.3: Path lines of flow from air inlet (x=0, z=0)

37

Results

Location Mass Flow Rate (kg/sec)

Velocity Magnitude (m/sec)

Air inlet (Fixed Value) 0.02598 127 Vacuum inlet (Fixed Value) 0.05605 161

Outlet -0.08204 211.0482 Total -3.166e-08 N/A

Table 5.10.1: FLUENT results

( ) ( )( ) %11

2370482.211237 Accuracy

sec 237

0 08 116.3

≈⎟⎠⎞

⎜⎝⎛ −

==

=

≈−−==+

η

mV

eQQQQ

Analyticaloutlet

outlet

outletvacuuminlet

38

6.0 Final Design

6.1 Bill of Materials

Qty Supplier Price1 Vaccon $157.501 McMaster-Carr $3.771 McMaster-Carr $0.681 McMaster-Carr $0.751 McMaster-Carr $4.761 McMaster-Carr $7.001 McMaster-Carr $7.001 McMaster-Carr $16.381 N/A $2.501 McMaster-Carr $0.751 McMaster-Carr $75.191 McMaster-Carr $0.751 McMaster-Carr $52.351 McMaster-Carr $0.751 McMaster-Carr $8.321 McMaster-Carr $0.96

$339.41

N/A

44615K4434457K42

44615K465

44615K4434370K11

44615K4434910K82

Pipe size = 3/4" / Lengths = 4"(Threaded both ends)

Part #DF-7-6-TV-75-TE-75

4513K1444615K43544615K44347865K224880K584880K5948925K98

Pipe size = 3/8" / Lengths = 2"(Threaded both ends)Pipe = 3/8" / 60 scfm max

Pipe size = 3/8" / Lengths = 2"(Threaded both ends)Pipe size = 3/4" / Lengths = 36"(Threaded both ends)

Pipe size = 4" / Do =4.5" Di = 4.026" / Max. Press = 220 psi / Funnel (80 deg => 86 deg)

Pipe size = 3/8" / Lengths = 2"(Threaded both ends)Desiccant Air Dryer -- Pipe size = 3/8 "

Pipe size = 3/8" / Lengths = 2"(Threaded both ends)Pipe size = 3/8" / End-to-End Length = 1 49/64"

Pipe size = 4" / Di = 4 1/2"Pipe size = 4" / Di = 4 1/2"

DescriptionMaterial Transfer Pump

90 Degree / Pipe size = 3/4"Pipe size = 3/4" / Lengths = 1 1/2"(Threaded both ends)

container_inner_wall

air_inlet_pipe4 long_feeding_pipe

Feeding Pipe

Part Name Vaccon DF7-6

elbow connecting_pipe

Manual_valve Bottom_cap

air_inlet_pipe

TOTAL

air_inlet _pipe_3 filter

air_inlet_pipe_2 dryer

Top_cap container_body

Table 6.1.1: Bill of Materials

6.2 Container

Figure 6.2.1: I-DEAS model of container Figure 6.2.2: Funnel dimensions

39

Four inch inner diameter PVC pipe used for the container. In order to introduce air into

the container four 1/8” holes have been drilled through the cap.

6.3 Vacuum Pump

The size used in the prototype is ¾” inner diameter. Following performance result

have been established in the analysis part of the report,

At 60 psi:Supply

pressure Weight of Powder Time

(PSI) (lbs) (sec) lb/sec grams/sec

252525

avg. 25.09080120

avg. 96.710 1 N/A* N/A* N/A*

* Suction below threshold - no powder transfer

15 1 0.010 4.7

Mass Flow Rate of Powder

20 - 60 1 0.040 18.0

Q = 46 fV

t3/min (0.022 m3/s) = 418 ft/s (127 m/s)

Q = 97.1 ft3/min(0.046 m3/s) = 528 ft/s (161 m/s)

t3/min (0.068 m3/s)V = 777 ft/s (237 m/s)

Outlet

Air Inlet

Vacuum Inlet

V

Q = 143 f

Final mass flow rate data

Table 6.3.1: Vacuum Pump Performance data at 60 psi Table 6.3.2: CarBETe mass flow rate

6.4 Air Supply

Electrically activated solenoid valve was used to open and close the air supply to

the vacuum pump. The design team was not required to incorporate the solenoid valve

but the sponsor of the project donated it for the prototype setup to improve the overall

completeness of the project because a solenoid valve will activate the blow sequence of

air in the real application.

40

Figure 6.4.1: Solenoid valve and switch Donated by sponsor

6.5 Bleeder

Three holes in the feeding tube allow the air to be pre-mixed with the powder

before it enters the vacuum pump.

Another ¾” bleeder hole on the other side of the container allows the vacuum pump to

draw in the powder more efficiently. The reason behind this is that the pump has to

overcome smaller distance to reach the air on he other side of the powder volume and

therefore functions more consistently than if no ¾” bleeder is used.

References

Figure: 6.5.1: Air bleeder ¾” opening

41

7.0 Conclusion

Desired Outcomes Actual outcomes

Fully functional prototype that transports

powder from holding canister into the

boiler

• No clogging of powder in the

system

• Powder level monitoring

• Adjustable flow rate

• Adaptable to wide range of

applications

- Industrial use

- Residential use

Fully functional prototype that transports

powder from holding canister into the

boiler

• No clogging of powder in the

system

• Powder level monitoring

• Adjustable flow rate

• Adaptable to wide range of

applications

- Industrial use

- Residential use

FINAL DESIGN

No maintenance

no moving parts

no lubrication necessary

Long lasting because non-corrosive materials used

Transfers 18 grams of powder per second (0.04 lb/s)

Holding canister capacity is 11 lbs (5 kg)

42

Figure 7.0.1: Final Design I-DEAS model Figure 7.0.2: Final Design I-DEAS model View 1 view 2

The Design Team met all the desired outcomes

The senior design team successfully re-designed the dry powder injection system

Future recommendations:

- Rugged, maintenance free design achieved but the amount of powder being

transferred cannot be controlled very accurately

- Future versions should improve on accuracy of powder transfer

8.0 References

[1] Vaccon, www.vaccon.com/material.html

[2] Vaccon, e-mail correspondence, 4/21/05

[3] White, M.F., 2003, Fluid Mechanics, 5th Edition

43

9.0 Appendix

Figure 9.0.1: Gantt Chart – rough schedule

44

Figure 9.0.2: I-DEAS model - view 3

Figure 9.0.3: Ideas model – container exploded view

45

Figure 9.0.4: Model view 4

Figure 9.0.5: Model view 5

46

Figure 9.0.6: Model view 6

Figure 9.0.7: Model view 7

47

Figure 9.0.8: Funnel view 1 – I-DEAS model

Figure 9.0.9: Model view 8

48

Figure 9.0.10: Model view 9

Figure 9.0.11: Funnel installed – I-DEAS model

49

Figure 9.0.12: Transparent canister view – I-DEAS model

Figure 9.0.13: Funnel dimensions

50

Figure 9.0.14: Holding Canister Cap – I-DEAS model

51

Figure 9.0.15: Vacuum Pump I-DEAS model – “Wire” view 1

Figure 9.0.16: Vacuum Pump I-DEAS model – “Wire” view 2

52