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Thread: Plastic recycling problem

  1. #1 Plastic recycling problem 
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    Nowdays a big issue is made of plastic recycling up to the point that countries started to prohibit plastic bags.

    Meanwhile I don't understand what prevent simply burn plastic bags/boxes and...generate energy. Plastic is
    often almost pure hydrocarbons. Power generation is still largely based on burning hydrocarbons. What principal
    difference does it make if people will burn oil and gas or if they will produce plastic from oil and gas and than
    burn it and generate electricity or heat?


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  3. #2  
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    Quote Originally Posted by Stanley514 View Post
    Nowdays a big issue is made of plastic recycling up to the point that countries started to prohibit plastic bags.

    Meanwhile I don't understand what prevent simply burn plastic bags/boxes and...generate energy. Plastic is
    often almost pure hydrocarbons. Power generation is still largely based on burning hydrocarbons. What principal
    difference does it make if people will burn oil and gas or if they will produce plastic from oil and gas and than
    burn it and generate electricity or heat?
    Because:

    1) a large proportion of plastic bags are not returned into recycling schemes,
    2) the collection and sorting involved in recycling schemes is resource-consumng and costly,
    3) a significant proportion of plastic packaging results from unimaginative policies on the part of manufacturers, supermarkets and other actors in the distribution chain (e.g. on-line purchased items delivered to the customer).

    Far better, therefore, to challenge the acceptability of plastic packaging and use consumer pressure on the suppliers to cut down on it at source, rather than just trying to manage the disposal of it afterwards.


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  4. #3  
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    burning of plastic releases toxic substance hence they should be done in controlled environment which mean higher cost for disposal.
    burning plastic doesn't release same amount of specific heat as gasoline so they cant be used as fuel
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  5. #4  
    Genius Duck Moderator Dywyddyr's Avatar
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    Quote Originally Posted by gdpvk View Post
    burning plastic doesn't release same amount of specific heat as gasoline so they cant be used as fuel
    Wrong.
    It simply mean that more should be burnt to provide the same energy.
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  6. #5  
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    pvc specific heat is 840-1140 j/kg-C
    gasoline specific heat is 2220 j/kg-C
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  7. #6  
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    Quote Originally Posted by gdpvk View Post
    burning of plastic releases toxic substance hence they should be done in controlled environment which mean higher cost for disposal.
    Which exactly toxic substances? More than coal or heating oils?
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  8. #7  
    Genius Duck Moderator Dywyddyr's Avatar
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    Quote Originally Posted by gdpvk View Post
    pvc specific heat is 840-1140 j/kg-C
    gasoline specific heat is 2220 j/kg-C
    And your point would be... what?
    For a station that produces power from burning the plastic is readily available and burning it will give heat while getting rid of the plastic which would otherwise cause problems.
    Fine, so you only get 40-50% of the energy that you would from gasoline but it frees up that gasoline for other (vehicular etc.) uses while still producing useful heat and getting rid of that plastic. It's a win-win situation.
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  9. #8  
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    Quote Originally Posted by Stanley514 View Post
    Quote Originally Posted by gdpvk View Post
    burning of plastic releases toxic substance hence they should be done in controlled environment which mean higher cost for disposal.
    Which exactly toxic substances? More than coal or heating oils?
    Yes, but it depends according to studies by the EPA and World Health Organization which show even incineration often processes substantial amounts of dioxines and other highly dangerous chemical emmisions.

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  10. #9  
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    Quote Originally Posted by gdpvk View Post
    pvc specific heat is 840-1140 j/kg-C
    gasoline specific heat is 2220 j/kg-C
    Specific heat, or specific heat capacity, is the amount of heat needed to raise the temperature of a gram, or kg, of the substance by 1 degree C.

    It has nothing to do with heat released by burning. For that you need the calorific value, or heat of combustion.

    If that is what you meant, it seems that the heat of combustion of gasoline is ~ 44MJ/kg. PVC seems to be about a quarter of that value.
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    yes my bad, i meant Heating value, thanks for pointing out exchemist
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  12. #11  
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    Quote Originally Posted by Dywyddyr View Post
    Quote Originally Posted by gdpvk View Post
    pvc specific heat is 840-1140 j/kg-C
    gasoline specific heat is 2220 j/kg-C
    And your point would be... what?
    For a station that produces power from burning the plastic is readily available and burning it will give heat while getting rid of the plastic which would otherwise cause problems.
    Fine, so you only get 40-50% of the energy that you would from gasoline but it frees up that gasoline for other (vehicular etc.) uses while still producing useful heat and getting rid of that plastic. It's a win-win situation.
    Why use PVC as an example.

    PVC is resistant to heat, and it barely burns, unless at extremely high temperatures. Depending on the type and composition of the PVC itself.

    It has intermediates (i mean waste products) like HCl gas, and Cl2 gas, higher odds to create CO and O- radicals, unless supplied with a higher oxygen concentration than normal fire.

    Plastics can also contain aluminium, nickel, chromium, zinc, PAH's, organic colorants and much more. These can form harmful compounds when burned.


    It seems you forget that a fire should provide energy to heat something up. To burn a plastic properly, the temperature needs to be higher, more oxygen needs to be added, the exhaust needs to be filtered, and the internals of the oven need to be corrosion/coating resistant. It is nearly impossible to keep a plastic furnace going, without it clogging, rusting, cracking or spilling into the atmosphere.

    Gas/Oil/coal is great. It has little impurities, a stable structure, a stable temperature it burns, a low temperature it will burn at, and it is easy to obtain.

    Getting rid of plastic is one of the biggest problems we face today. Burning it will not be a perfect solution. I won't say it will not help at all, but it is costly, inefficient, and difficult.

    The energy gained by burning it shouldn't even be something to point out, as it will be a minor benefit to burning it.

    If you want to burn plastic, you need to mix it with wood and other plant/animal materials. So that the total emissions will be within the acceptable parameters.
    Last edited by Zwolver; February 9th, 2018 at 08:14 AM.
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