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Stubby

Arson ?

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Chichester amenity tip went up in frames last night  . I could see the glow and plume of smoke from my loft window ( about 5 miles away ) . At the time it had been raining and hail stoning . Every where was pretty wet .  There is still a column of smoke this evening .  Pure speculation but arson ?

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3 hours ago, Stubby said:

Chichester amenity tip went up in frames last night  . I could see the glow and plume of smoke from my loft window ( about 5 miles away ) . At the time it had been raining and hail stoning . Every where was pretty wet .  There is still a column of smoke this evening .  Pure speculation but arson ?

My guess it it will normally be caused by a person, either inadvertently or deliberately, but spontaneous combustion of heaps of wood is fairly common and more likely the bigger the heap and  green matter and resinous material.

 

What seems to happen is mesophilic bacteria digest the volatile solids and get hot, up to 70C, as the heap is large the  heat does not escape easily, methane, steam, CO  and CO2 are given off, rise through the heap and the water condenses as it reaches cooler layers whilst the methane  CO  And CO2 escape.

 

We now have a warm dry area in the heap  into which air can diffuse. Any lipids, oils or fatty esters left  react with the air, in the same way oil paints or turpentine "dries" in paint. This is a form of oxidation so the temperature rises a bit more. It only has to reach about 200C for Oxygen atoms to dissociate and combine with  any degraded plant material ( like touchwood does) and true combustion starts. Initially smouldering as the pyrolysis offgases are well below their autoignition point but once the smouldering reaches about 450C then a flame can take hold.

Edited by openspaceman
Added temperature
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The resultant problem at this site is it is right next to the lakes ( Fishing water skiing etc )  which in turn drain into  Pagham harbor should they over fill .  Because of this the fire brigade wont heap tons of water for fear of contamination . They are dragging parts out and damping it down were they can .  I am 5 or 6 miles away in Lavant village but can small he burn now on the wind . 

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2 hours ago, Stubby said:

Because of this the fire brigade wont heap tons of water for fear of contamination . They are dragging parts out and damping it down were they can . 

Big heaps shed water and often there is enough oxygen in air in the heap to sustain pyrolysis, straw is a good case where there is enough air in the hollow stems to oxidise all the carbon in the straw, swamping it with water won't work, this is why thatch stays dry.

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11 hours ago, openspaceman said:

My guess it it will normally be caused by a person, either inadvertently or deliberately, but spontaneous combustion of heaps of wood is fairly common and more likely the bigger the heap and  green matter and resinous material.

 

What seems to happen is mesophilic bacteria digest the volatile solids and get hot, up to 70C, as the heap is large the  heat does not escape easily, methane, steam, CO  and CO2 are given off, rise through the heap and the water condenses as it reaches cooler layers whilst the methane  CO  And CO2 escape.

 

We now have a warm dry area in the heap  into which air can diffuse. Any lipids, oils or fatty esters left  react with the air, in the same way oil paints or turpentine "dries" in paint. This is a form of oxidation so the temperature rises a bit more. It only has to reach about 200C for Oxygen atoms to dissociate and combine with  any degraded plant material ( like touchwood does) and true combustion starts. Initially smouldering as the pyrolysis offgases are well below their autoignition point but once the smouldering reaches about 450C then a flame can take hold.

Very good info I did wonder how this happens

cheers 

Edited by alfieb2785

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