It's Official

And this technology obviously benefits all the residents of Los
Angeles, Chicago, Houston, Milwaukee, New York, New Jersey,
Baltimore, Philadelphia, not to mention Sacramento and Ventura
County, in the oh so clean California.

The UK doesn't suffer from photochemical smog, see. Swathes of the US
do. QED.

 

A catalytic converter isn't a filter. And it certainly isn't intended to
compensate for poor design.

The raw stuff that comes out of a spark-ignition engine is exactly the same
stuff that went it -- carbon, oxygen, hydrogen, sulphur, nitrogen, etc. But
the burning process rearranges how the atoms are arranged, so you get oxygen
combining with carbon to give you carbon monoxide and carbon dioxide. You
get oxygen combining with nitrogen to give you nitrogen oxide and nitrogen
dioxide. Sulphur combines with oxygen to give you Sulphur dioxide. And so
on. These are mostly nasty compounds. The catalytic converter will
rearrange the atoms again, converting almost all the nasty compounds to
carbon dioxide, which was not (until recently) considered a pollutant.

The cat requires that the engine burn a stoichiometric mixture (about 14.7:1
for petrol). That's because the cat needs unburned hydrocarbons (i.e.,
fuel) and oxygen to do its work. The lean-burn engine can (obviously) burn
a much leaner mixture, but now the cat is unhappy because it's underfed.

 

Pip wrote

We used to, it was only the Clean Air legislation and our move away from
solid fuels for domestic use that stopped it.

Bristol does dunnit, or is it Swansea I am thinking about?

Not by a long way.

 

I remember that song.... wasn't it 'video'?

 

Thank the strong westerlies for that....

 

And don't forget that cats require rare metals that need to be
extracted and refined and the cats themselves have to be manufactured
at some cost to the environment.

Cars have been picked on simpy because they're an easy target, not
just politically but because it's easier and less disruptive to do
something about them.

If I've read a DEFRA chart on 2003 emissions properly, then road
transport only makes up just over a fifth of all our CO2 emissions.

 

It's a good selling point, agreed, but in addition - diesels have
torque. Lots of it. Some of us like that.

All of them. Or all built in the last decade or two.

In very, very limited quantities, from very few outlets. Effectively,
no.

Erm, which nation did not ratify the Tokyo protocols?

Now that you have demonstrated your ignorance in just about everything,
what will you do for an encore?

 

This, at least, has a grain of truth.

 

<snip>

Do you know what ts, on European roads, the cleanest internal combustion
engine? Amazingly, it isn't an engine running on compressed natural gas,
or propane.

It's a diesel. It's a diesel running with a cat and a CRT[1]

[1] Look it up.[2]
[2] I will grant that they're mostly fitted to commercial vehiucles, but
the point still rests.[3]
[3] Lower NOX, lower CO2, and (it's true) lower particulate
emissions.[4]
[4] Ask a truck expert for confirmation, if you don't believe me.

 

Yes, I know.

Yes, I have a chemistry 'A' level [1] from when a chemistry 'A' level
was worth something. It's a shame about CO2 not being recognised as a
pollutant until recently. So which is worse, a bit of smog or global
warming leading to catostrophic climate change? [2].

Ahh. Interesting. I didn't know the bit about cats actually requiring
the unburned hydrocarbons. Makes sense when you think about it though.

[1] An exam
[2] You don't have to answer this

 

No. Thank the Clean Air Act of 1956.

Look, you're arguing from a position of massive ignorance here, and
you're making yourself look a fool. Best give up.

 

I don't know but it's a good question and the sort of thing which is
often ignored by environmentalists.

 

Pip Luscher wrote

What do they say about Airlines?

 

<doffs white hat in Pip's direction>

Smog yes, photochemical no. With the possible exception of 'Teesside
Mist' in the 70's although that was as a result of chemical industry
emissions (and sunlight) rather than vehicles.

Dunno (check their air quality management reports), but in both of those
areas the culprit is more likely to be industry (Avonmouth in the case
of Bristol) , whereas this thread seems to be concentrating on vehicle
emissions.


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*Ding*. Maybe we could sue the population of CA over the damage to the
environment their domestic AC installations cause.

 

The modernisation plan of the 50s and 60s that led to the removal of
steam engines from the railways also went a long way in helping.

I have an early 60s B&W documentary of loco men at Newton Heath
(Manchester) talking about the passing of steam and the introduction of
colour light signalling. Excellent shots of the shed with 30 or so locos
so shrouded in smoke you can barely see the yard.

Beautiful period piece but, in all honesty, some of the scenes - such as
the men crowded round the pay window and roster cases or smoking and
drinking tea on the long forms and tables in the lobbies and cabins (mess
rooms) - have only recently disappeared.

Can't remember the bloody title though.

 

So you're as good at chemistry as is Gas Giant.
A cat can't convert nitrogen and sulphur to carbon.
You need the philosopher's stone for that, not a platinum film.
Cats don't need unburned hydrocarbons. The stoichiometric ratio
means there is exactly enough oxygen for the fuel....

 

Well, I only got a B.

This is true and I wish I'd read what he wrote more carefully now.

Only if combustion is perfect. Are you saying combustion is perfect in
an IC engine? Thought not. HCs are one of the pollutants removed by the
cat.

 

Emissions would have been reduced further if new cars were restricted to 1500Kg
and 2litres, for a start, instead of V8 behemoths with slushboxes and cats.

 

I didn't say that it did. Granted, I could have phrased it better.
Obviously there are sulphur
compounds and nitrogen compounds in the exhaust, as well as the carbon
compounds that I mentioned. But my point is still valid -- most of the
oxygen that was in the NOx, and most of the carbon that was in the HCs,
leaves the cat as CO2. Much of the hydrogen from the HCs combines with
oxygen to produce water.

There's no such thing as perfect combustion. There will always be some
unburned HCs in the exhaust. And these are oxidized (i.e., burned) in the
cat, thus contributing to an increase in temperature, which (withing limits)
will increase the efficiency of the converter.