1. Compromise in Design Peter Fransham, PhD VP Technology ABRI-Tech Inc. Namur, Quebec TERM 7 DESIGN CLASS

2. Theory VS Reality Rule #1 there is never enough time to do the design you want Rule #2 There are a number of very high powered programs -eg finite element that would be great to use, but the cost is high and client enthusiasm is low - budget. Rule #3 Experience and personality play a large role in design.

3. Competing Forces Human factors including team profile  Unnecessary complexity because complexity is associated with knowledge  Inability to retreat and start over  We have done it this way for 20 years and we are not changing now Client requirements – course requirments Budget – time balancing with other course. Risk – factor of safety – what are the consequences of failure Engineering associations – ethics - legal

4. First Steps in Design What is the outcome you want Write down a few simple statements  Producing a concrete kayak  Has to float  Egonomic factors – has to fit a human body comfortably You need a fixed point on the horizon but there are many paths to that point Unlikely there will be an optimum path as the competing forces will select or force certain options.

5. Design Creep Almost all of us have been taught that failure is bad. We will alway tend to err on the conservative side. For small projects this is not generally too much of a problem because the number of components is too small. Complex project this is a real issue.  Designing an aircraft – large team with multi- diciplines  Nobody wants their part to fail so they make the part a little stronger and an little heavier than it really has to.  Design ends up being so heavy the plane can't fly or the kayak sinks. You have to be aware of Design Creep and continuously strive for the best design even if it is a simple one.

6. Design Creek Corollery With design creep comes cost creep. The project ends up over budget and may not perform according to specifications. Now you have a major problem – you have no more time, no budget and a hostile customer. Another rule – keep it simple even if you want to look intellegent by a complex design.

7. Case History – Two Pyrolysis Systems Pyrolysis is a thermo-chemical process to convert biomass into liquid fuels. Wood is a polymer and we are cracking that polymer into smaller molecules, some of which are liquid. Objectives: maximize liquid yield and quality for use as a fuel. For now we will assume there is a market for the fuels. Heat transfer from heat carrier to biomass

8. What are the Primary Constraints? Selling gigajoules – a commodity with a price that varies internationally. The amount of revenue is largely out of our hands. Capital and operating costs – The first rule of business is “don't loose money”!! You don't necessarily have to make money, just don't loose it.

9. DESIGN #1 CIRCULATING FLUID BED BLOWER

10. CIRCULATING BED Circulating hot sand Verical tube mixing sand and biomass For commercial scale tube is 10 – 15 m high Residence Time about 1 second Velocity 10 – 20 m/sec Circulating gas has to be continuously heated and cooled All biochar and NCG gas is burned to provide process heat

11. As Built

12. DESIGN #2 AUGER WITH STEEL SHOT

13. AUGER PYROLYSIS CIRCULATES STEEL SHOT AROUND A LOOP BIOMASS IS INCORPORATED INTO HOT SHOT AND PYROLYZED CHAR STRIPPED FROM SHOT WITH CIRCULATING FAN AND CYCLONE SIMPLE TUBE AND SHELL CONDENSERS SYSTEM OPERATES AT +1 CM H2O

14. As Built

15. OBVIOUS COMPARISONS AUGER CFB Mecanical mixing Intimate contact Dense high thermoconductivity heat carrier Reactor temp 470 C No fluidization blower and no carrier gas to heat and cool Pneumatic mixing Disperse contact Low density low thermoconductivity heat carrier Reactor temp 515 C Energy consumptive blower and carrier gas

16. HEAT TRANSFER CARRIER AUGER CFB Q= cp*Delta T* M cp shot 0.5 kJ/kg-K Thermconductivity 43 W(m-k) Density 4.5 kg/l Delta T 20 C 45 kJ/l Pyrolysis heat 1000 kJ/kg 22 litres of shot per kg of biomass Q= cp*Delta T* M cp sand 0.8 kJ/kg-K Thermconductivity 0.15 W(m-k) Density 0.5 kg/l Delta T 20 C 8 kJ/l Pyrolysis heat 1000 kJ/kg 125 litres of sand per kg of biomass Plus the inert gas moved

17. Basic Ecoomics What is important: Capital cost Operating cost Revenue from products sold

18. Capital Cost Need to minimize capital cost Interesting problem Use cheaper parts to minimize capital cost Push maintenance onto the owner Risk having reputation as a poor product No simple answer.

19. Operating Cost Labour – Output per manhour OSHA and Labour Legislation Feedstock cost – need to minimize yet get quality Maintenance – this is a big one For many industries maintenance is between 3% and 5% of capital cost. Back to the design and pushing the capital cost down at the expense of maintenance. Since maintenance is a percent of capital it is important to design to minimize capital cost and keep it simple

20. Back to Case History 100 tonne per day ParameterAugerCFB Capital Cost$5 million$20 million Electricity.25 mW1.3 mW Operating hours 7500 Electricity Cost $175,000$975,000 Maintenance 5% Capital $250,000$1,000,000 Total$425,000$1,975,000 Production T/yr21,45023,100 Cost per tonne$19.80$85.50 Sale price Bunker C$175/tonne Biomass Cost $/dry tonne$60.00 Minimum Profit 10%$17.50

21. Summary Always look for the simplest solution Avoid the trap of trying to look smart by a complex design Continuously evaluate the factor of safety to make certain the design is safe but not excessively so. Don't be afraid to back up and redesign – it is better than the concrete kayak that sinks.