General > General Technical Chat
How to recycle plastics
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langwadt:

--- Quote from: Zero999 on August 03, 2022, 05:30:14 pm ---
--- Quote from: langwadt on August 03, 2022, 02:39:43 pm ---
--- Quote from: Zero999 on August 03, 2022, 02:28:22 pm ---
--- Quote from: AndyBeez on August 03, 2022, 02:19:13 pm ---Picture this... 500kg of VHS video tapes. That is what my last company had as surplus media in one store room alone. As studious studio employees, we tried to get them recycled. Easy? Not one UK e-waste company would touch them.

The issue is a typical video cassette contains at least six different types of plastic, often welded together. Plus there are metal screws, rollers and springs. Finally the video tape medium is rich in nasty phenols and pcbs.

The advice we received from our local council's business waste officer was to send them all into landfill. This was safer than burning them which requires a special hazmat license.

Even disassembled, a video tape is uneconomic to reclaim. How many tonnes of unused video tapes are there around the world?

--- End quote ---
Thermal depolymerisation could be used to turn them back into crude oil. In theory it should work with any organic material, including dead bodies, but it's probably only economical to do so with plastic.


--- Quote from: langwadt on August 02, 2022, 11:26:05 pm ---as long as we are burning fossil fuel to make heat and electricity, just incinerate the plastic to make heat/electricity, it is basically oil anyway

--- End quote ---
Gassification is another potential useful way to get energy from waste. The plastic and dry organic material is partially combusted to make carbon-monoxide, hydrogen and methane, which can power an internal combustion engine or turbine. This is more efficient that just burning them to create steam and it's easier to filter the fuel gas to remove the tar, than the flue gas.

--- End quote ---

how is adding more steps going to make it more efficient? generating steam and running steam turbines is very efficient, that is why pretty all powerplants do it ...

--- End quote ---
Not necessarily. For example hybrid cars are more efficient than those with plain old internal combustion engines.

--- End quote ---

in start-stop traffic sure, going down the highway not so much if at all


--- Quote from: Zero999 on August 03, 2022, 05:30:14 pm ---
Fossil fuel power plants burn coal or gas, which are consistent and still much cleaner than plastic, which will be mixed with other rubbish.

When rubbish is just burned, it releases a large volume of toxic gasses, as well as the CO2 and H2O. The advantage of gasification is a smaller volume of syngas can be cleaned, before it's burned in an internal combustion engine, which will have a very clean exhaust because the fuel is so clean. Another advantage of gasification is the syngas can be stored, although that requires a lot of space as it becomes unstable at high pressures.

--- End quote ---

coal plants already need lots of exhaust cleaning, so it is a matter of cleaning the exhaust or the gas with the loss in efficiency from an extra step


--- Quote from: Zero999 on August 03, 2022, 05:30:14 pm ---Internal combustion engines have a greater dynamic range and can be started and stopped fairly quickly. Turbines take awhile to get up and running and have to be run at a certain speed to achieve optimum efficiency.

--- End quote ---

Internal combustion engines quickly lose efficiency at part load, even more so with gas turbines, and in any case they usually have to run at a certain speed because they have to generate 50/60Hz
Zero999:

--- Quote from: langwadt on August 07, 2022, 08:20:49 pm ---
--- Quote from: Zero999 on August 03, 2022, 05:30:14 pm ---
--- Quote from: langwadt on August 03, 2022, 02:39:43 pm ---
--- Quote from: Zero999 on August 03, 2022, 02:28:22 pm ---
--- Quote from: AndyBeez on August 03, 2022, 02:19:13 pm ---Picture this... 500kg of VHS video tapes. That is what my last company had as surplus media in one store room alone. As studious studio employees, we tried to get them recycled. Easy? Not one UK e-waste company would touch them.

The issue is a typical video cassette contains at least six different types of plastic, often welded together. Plus there are metal screws, rollers and springs. Finally the video tape medium is rich in nasty phenols and pcbs.

The advice we received from our local council's business waste officer was to send them all into landfill. This was safer than burning them which requires a special hazmat license.

Even disassembled, a video tape is uneconomic to reclaim. How many tonnes of unused video tapes are there around the world?

--- End quote ---
Thermal depolymerisation could be used to turn them back into crude oil. In theory it should work with any organic material, including dead bodies, but it's probably only economical to do so with plastic.


--- Quote from: langwadt on August 02, 2022, 11:26:05 pm ---as long as we are burning fossil fuel to make heat and electricity, just incinerate the plastic to make heat/electricity, it is basically oil anyway

--- End quote ---
Gassification is another potential useful way to get energy from waste. The plastic and dry organic material is partially combusted to make carbon-monoxide, hydrogen and methane, which can power an internal combustion engine or turbine. This is more efficient that just burning them to create steam and it's easier to filter the fuel gas to remove the tar, than the flue gas.

--- End quote ---

how is adding more steps going to make it more efficient? generating steam and running steam turbines is very efficient, that is why pretty all powerplants do it ...

--- End quote ---
Not necessarily. For example hybrid cars are more efficient than those with plain old internal combustion engines.

--- End quote ---

in start-stop traffic sure, going down the highway not so much if at all


--- Quote from: Zero999 on August 03, 2022, 05:30:14 pm ---
Fossil fuel power plants burn coal or gas, which are consistent and still much cleaner than plastic, which will be mixed with other rubbish.

When rubbish is just burned, it releases a large volume of toxic gasses, as well as the CO2 and H2O. The advantage of gasification is a smaller volume of syngas can be cleaned, before it's burned in an internal combustion engine, which will have a very clean exhaust because the fuel is so clean. Another advantage of gasification is the syngas can be stored, although that requires a lot of space as it becomes unstable at high pressures.

--- End quote ---

coal plants already need lots of exhaust cleaning, so it is a matter of cleaning the exhaust or the gas with the loss in efficiency from an extra step


--- Quote from: Zero999 on August 03, 2022, 05:30:14 pm ---Internal combustion engines have a greater dynamic range and can be started and stopped fairly quickly. Turbines take awhile to get up and running and have to be run at a certain speed to achieve optimum efficiency.

--- End quote ---

Internal combustion engines quickly lose efficiency at part load, even more so with gas turbines, and in any case they usually have to run at a certain speed because they have to generate 50/60Hz

--- End quote ---
Have you actually bothered to read up about gasification, before attempting to debunk it? There are many reasons why it's preferable, than just burning the waste directly to generate heat. It's also used for coal. It's just more common for energy from waste because it can't be ground to a consistent powder like coal can.
https://en.wikipedia.org/wiki/Gasification
https://power.mhi.com/products/igcc
https://kleinmanenergy.upenn.edu/news-insights/waste-gasification-how-old-technology-can-solve-a-modern-problem/
langwadt:

--- Quote from: Zero999 on August 07, 2022, 08:55:35 pm ---
--- Quote from: langwadt on August 07, 2022, 08:20:49 pm ---
--- Quote from: Zero999 on August 03, 2022, 05:30:14 pm ---
--- Quote from: langwadt on August 03, 2022, 02:39:43 pm ---
--- Quote from: Zero999 on August 03, 2022, 02:28:22 pm ---
--- Quote from: AndyBeez on August 03, 2022, 02:19:13 pm ---Picture this... 500kg of VHS video tapes. That is what my last company had as surplus media in one store room alone. As studious studio employees, we tried to get them recycled. Easy? Not one UK e-waste company would touch them.

The issue is a typical video cassette contains at least six different types of plastic, often welded together. Plus there are metal screws, rollers and springs. Finally the video tape medium is rich in nasty phenols and pcbs.

The advice we received from our local council's business waste officer was to send them all into landfill. This was safer than burning them which requires a special hazmat license.

Even disassembled, a video tape is uneconomic to reclaim. How many tonnes of unused video tapes are there around the world?

--- End quote ---
Thermal depolymerisation could be used to turn them back into crude oil. In theory it should work with any organic material, including dead bodies, but it's probably only economical to do so with plastic.


--- Quote from: langwadt on August 02, 2022, 11:26:05 pm ---as long as we are burning fossil fuel to make heat and electricity, just incinerate the plastic to make heat/electricity, it is basically oil anyway

--- End quote ---
Gassification is another potential useful way to get energy from waste. The plastic and dry organic material is partially combusted to make carbon-monoxide, hydrogen and methane, which can power an internal combustion engine or turbine. This is more efficient that just burning them to create steam and it's easier to filter the fuel gas to remove the tar, than the flue gas.

--- End quote ---

how is adding more steps going to make it more efficient? generating steam and running steam turbines is very efficient, that is why pretty all powerplants do it ...

--- End quote ---
Not necessarily. For example hybrid cars are more efficient than those with plain old internal combustion engines.

--- End quote ---

in start-stop traffic sure, going down the highway not so much if at all


--- Quote from: Zero999 on August 03, 2022, 05:30:14 pm ---
Fossil fuel power plants burn coal or gas, which are consistent and still much cleaner than plastic, which will be mixed with other rubbish.

When rubbish is just burned, it releases a large volume of toxic gasses, as well as the CO2 and H2O. The advantage of gasification is a smaller volume of syngas can be cleaned, before it's burned in an internal combustion engine, which will have a very clean exhaust because the fuel is so clean. Another advantage of gasification is the syngas can be stored, although that requires a lot of space as it becomes unstable at high pressures.

--- End quote ---

coal plants already need lots of exhaust cleaning, so it is a matter of cleaning the exhaust or the gas with the loss in efficiency from an extra step


--- Quote from: Zero999 on August 03, 2022, 05:30:14 pm ---Internal combustion engines have a greater dynamic range and can be started and stopped fairly quickly. Turbines take awhile to get up and running and have to be run at a certain speed to achieve optimum efficiency.

--- End quote ---

Internal combustion engines quickly lose efficiency at part load, even more so with gas turbines, and in any case they usually have to run at a certain speed because they have to generate 50/60Hz

--- End quote ---
Have you actually bothered to read up about gasification, before attempting to debunk it? There are many reasons why it's preferable, than just burning the waste directly to generate heat. It's also used for coal. It's just more common for energy from waste because it can't be ground to a consistent powder like coal can.
https://en.wikipedia.org/wiki/Gasification
https://power.mhi.com/products/igcc
https://kleinmanenergy.upenn.edu/news-insights/waste-gasification-how-old-technology-can-solve-a-modern-problem/

--- End quote ---


"
A major challenge for waste gasification technologies is to reach an acceptable (positive) gross electric efficiency. The high efficiency of converting syngas to electric power is counteracted by significant power consumption in the waste preprocessing, the consumption of large amounts of pure oxygen (which is often used as gasification agent), and gas cleaning. Another challenge becoming apparent when implementing the processes in real life is to obtain long service intervals in the plants, so that it is not necessary to close down the plant every few months for cleaning the reactor.
"
Zero999:

--- Quote from: langwadt on August 07, 2022, 10:41:10 pm ---
--- Quote from: Zero999 on August 07, 2022, 08:55:35 pm ---
--- Quote from: langwadt on August 07, 2022, 08:20:49 pm ---
--- Quote from: Zero999 on August 03, 2022, 05:30:14 pm ---
--- Quote from: langwadt on August 03, 2022, 02:39:43 pm ---
--- Quote from: Zero999 on August 03, 2022, 02:28:22 pm ---
--- Quote from: AndyBeez on August 03, 2022, 02:19:13 pm ---Picture this... 500kg of VHS video tapes. That is what my last company had as surplus media in one store room alone. As studious studio employees, we tried to get them recycled. Easy? Not one UK e-waste company would touch them.

The issue is a typical video cassette contains at least six different types of plastic, often welded together. Plus there are metal screws, rollers and springs. Finally the video tape medium is rich in nasty phenols and pcbs.

The advice we received from our local council's business waste officer was to send them all into landfill. This was safer than burning them which requires a special hazmat license.

Even disassembled, a video tape is uneconomic to reclaim. How many tonnes of unused video tapes are there around the world?

--- End quote ---
Thermal depolymerisation could be used to turn them back into crude oil. In theory it should work with any organic material, including dead bodies, but it's probably only economical to do so with plastic.


--- Quote from: langwadt on August 02, 2022, 11:26:05 pm ---as long as we are burning fossil fuel to make heat and electricity, just incinerate the plastic to make heat/electricity, it is basically oil anyway

--- End quote ---
Gassification is another potential useful way to get energy from waste. The plastic and dry organic material is partially combusted to make carbon-monoxide, hydrogen and methane, which can power an internal combustion engine or turbine. This is more efficient that just burning them to create steam and it's easier to filter the fuel gas to remove the tar, than the flue gas.

--- End quote ---

how is adding more steps going to make it more efficient? generating steam and running steam turbines is very efficient, that is why pretty all powerplants do it ...

--- End quote ---
Not necessarily. For example hybrid cars are more efficient than those with plain old internal combustion engines.

--- End quote ---

in start-stop traffic sure, going down the highway not so much if at all


--- Quote from: Zero999 on August 03, 2022, 05:30:14 pm ---
Fossil fuel power plants burn coal or gas, which are consistent and still much cleaner than plastic, which will be mixed with other rubbish.

When rubbish is just burned, it releases a large volume of toxic gasses, as well as the CO2 and H2O. The advantage of gasification is a smaller volume of syngas can be cleaned, before it's burned in an internal combustion engine, which will have a very clean exhaust because the fuel is so clean. Another advantage of gasification is the syngas can be stored, although that requires a lot of space as it becomes unstable at high pressures.

--- End quote ---

coal plants already need lots of exhaust cleaning, so it is a matter of cleaning the exhaust or the gas with the loss in efficiency from an extra step


--- Quote from: Zero999 on August 03, 2022, 05:30:14 pm ---Internal combustion engines have a greater dynamic range and can be started and stopped fairly quickly. Turbines take awhile to get up and running and have to be run at a certain speed to achieve optimum efficiency.

--- End quote ---

Internal combustion engines quickly lose efficiency at part load, even more so with gas turbines, and in any case they usually have to run at a certain speed because they have to generate 50/60Hz

--- End quote ---
Have you actually bothered to read up about gasification, before attempting to debunk it? There are many reasons why it's preferable, than just burning the waste directly to generate heat. It's also used for coal. It's just more common for energy from waste because it can't be ground to a consistent powder like coal can.
https://en.wikipedia.org/wiki/Gasification
https://power.mhi.com/products/igcc
https://kleinmanenergy.upenn.edu/news-insights/waste-gasification-how-old-technology-can-solve-a-modern-problem/

--- End quote ---


"
A major challenge for waste gasification technologies is to reach an acceptable (positive) gross electric efficiency. The high efficiency of converting syngas to electric power is counteracted by significant power consumption in the waste preprocessing, the consumption of large amounts of pure oxygen (which is often used as gasification agent), and gas cleaning. Another challenge becoming apparent when implementing the processes in real life is to obtain long service intervals in the plants, so that it is not necessary to close down the plant every few months for cleaning the reactor.
"

--- End quote ---
That applies to many energy from waste systems, not just gasification.  Its more of a problem for waste containing large amounts of water i.e. soiled nappies and medical waste, which requires large amounts of energy to dry, irrespective of whether it's burnt directly or gasified first.  It isn't an issue for dry waste such as plastics and biomass i.e. nut shells.

Getting net energy from gasification is easy using dry fuel. Pure oxygen isn't required.  It's an old technology first used to convert coal to provide gas to homes. It fell out of favour for cheaper, cleaner natural gas. There are numerous videos on YouTube of people running gasifiers to power vehicles and electric generators and it works very well.
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