Hydrogen home heating

Stevetee,

Producer gas and water gas were products of basically burning fossil fuel - coal.

Producer gas was, one could say, a product of incomplete combustion of coal - leaving behind coke. The process was exothermic.

Water gas was produced by passing steam over that same coking system when hot enough

Making water gas was very much endothermic but produced a higher calorific fuel (no nitrogen in it, for a start!).

The usual mode of operation was to heat the system by passing air over the hot coals and then use water until the temperature dropped too low. The common system was, therefore, to maintain temperature by passing air and some steam over the coals to maintain the system temperature.

The gas produced was stored in low pressure gasometers and distributed fairly locally - often one in a large town - hence the name ‘town gas’.

Still a fossil fuel burning system (both in manufacture and usage), which we want to get rid of. So a non-starter.

All parts of the country were on natural gas by the very early 70s. Gasometers were retained mainly in steel producing locations as coke was needed for the steel manufacturing process🙂 . Our new school, in 1963, was converted to natural gas by the middle 60s.

Hope that enlightens you on the topic.

Edited By not done it yet on 19/05/2021 22:34:08

Edited By V8Eng on 19/05/2021 22:53:14

Edited By V8Eng on 19/05/2021 22:53:40

Michael

Many thanks for your reply, I thought that hydrogen was liquid at normal air pressure but I wasn’t 100% sure. Dave W

Some gasholders (not "gasometers" ) were retained in various places even after all the network was on natural gas.

The last of the two at Weymouth was taken out of use within only the last decade or so, and scrapped two years ago, last year maybe, complete with the buddlia bushes growing on its top. Yet the gas-works itself - with retort as well as producer and water gas, plant - had been demolished in the 1960s. The gas-holder had been retained as part of the local distribution point but it seems the primary pipework takes that role now.

The town gas-works' primary product was retort gas, produced by distilling the coal in sealed retorts heated externally by coke already made by that process. It and producer gas, which was made in a separate process from some of the coke (not raw coal) were carbon-monoxide. Water gas, also from coke, is mainly hydrogen.

'

Somewhere I have the proceedings of a 1980s symposium on the wood alternative, making gas from wood in small-scale power-plants. The wood was to be distilled in retorts and the gas used in i.c. engines driving alternators. Most of the proceedings covered the forestry side - the choice of tree best suited to this. Mainly willow as I recall, as it grows rapidly.

I hadn't realised that town gas wasn't hydrogen, but a mix of H2 and CO. Well theres that idea dead in the water then...

Don’t forget the nitrogen in the gas that diluted it (and would obviously reduce the flame temperature) and some carbon dioxide mixed in as well.🙂

Nothing new. Wood was used, as an alternative to petrol, when fuel was in short supply. WWII saw some novel designs for collecting the gas in a bag on the roof of the car. I think one or two even made conversions back in the fuel crises of the 1970s, but doubtless one-offs that were made just because it could. Not particularly relevant to modern cars, even back then - although THIS GUY did it jus a decade, or so, ago.

Check this out, if interested enough. **LINK**

Even some tractors had wood gasifiers fitted in WWII. Not, I would think, for excessively hard working applications - but maybe they were....

.

... which reminds me :

Late sixties, if I recall correctly ... I read that, in appropriate climates, the most efficient ‘total cost’ way of using Solar Energy was to grow ‘Water Hyacinth’ and burn it.

https://en.wikipedia.org/wiki/Eichhornia_crassipes

May no longer be true, because technology has progressed [*]

MichaelG.

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* This was at the time when people were using central-heating radiators as solar panels for heating domestic water

Edited By Michael Gilligan on 20/05/2021 08:48:01

I think that was metal hydride storage rather than a safety device.

Not really going back! Most of the world's Hydrogen is made today by a close relative of the Town Gas process described by NDIY.

Instead of spraying water on to white hot coke, it's done by reacting steam at about 1000°C with Natural Gas at about 300psi in the presence of a catalyst to produce a mix of steam, Carbon Monoxide and Hydrogen. Then the mix is passed over another catalyst to produce Carbon Dioxide and more Hydrogen before the Carbon Dioxide is removed by absorption. The output is almost pure Hydrogen.

Oil refineries are the biggest single user of Hydrogen. They use it to crack heavy oils to make petrol etc and also to remove Sulphur (nasty stuff). Next largest use is Fertilizer production, without which we all starve! Saudi Arabia makes more Fertilizer than anyone else because their oil fields are gassy at it would otherwise be flared off. Hydrogen has many other important applications; welding, Hydrochloric Acid, Margarine, as a coolant, and extracting metals. The Tungsten used in HSS and Carbide is obtained with Hydrogen.

The only reason Hydrogen is made from steam is Natural Gas happens to be cheap at the moment. Unfortunately Natural Gas is a declining resource; shortages will develop over the next 20 years causing prices to rise sharply, and this way of making Hydrogen will become uneconomic. So alternative sources will soon be needed, and cheap electrolytic Hydrogen made by surplus green energy is a practical option.

Personally, I don't believe there's much future for Hydrogen as a transport fuel - too many difficulties as already explained! But there's no technical reason why Hydrogen can't be mixed into the existing gas distribution system and burned in diluted form for domestic heating. My guess though is most Hydrogen will go to industry, especially to make fertilizer.

Dave

I think there is some confusion in terminology. The stuff that used to be in the gas mains supplying domestic premises, at least in the UK was coal gas, produced by heating bituminous coal in a closed retort. It's typical analysis by volume was Hydrogen 45%, Methane 33%, Carbon Monoxide 10%, Ethylene 5%, Carbon Dioxide 1%, Nitrogen 6%. Calorific value 568/618 BThU/Cu.Ft. These figures from Mechanical World Year Book 1950. The residue was coke, some of which was used to heat the retorts, some as a scrubber medium to clean the gas, and the rest sold

Producer gas is made by burning coke in a limited supply of air to produce Carbon Monoxide. All the Google results suggest that steam was admitted at the same time to make a mix of what I've always known as Producer Gas and Water Gas. The typical analysis by volume of this mix was Carbon Monoxide 25%, Hydrogen 16%, Carbon Dioxide 5%, the rest (54%) is Nitrogen. Because of the nitrogen content its calorific value is 120/150 BThU/Cu.Ft. Figures from same source. It was not used in town gas mains.

Producer gas was also known as suction gas. Many early gas engines ran on it, in the village of my childhood there was a sawmill driven by a big suction gas engine which used sawdust and offcuts as fuel. You could hear its slow steady beat from a mile or so.

Duncan's right about Producer Gas, but has missed that Water Gas was a major constituent of so called Coal Gas as described above. It's true the terminology is blurred.

In their day Gasworks were high-technology! Roasting coal in a retort produces many different valuable chemicals in small but useful quantities. With increasing heat:

• Watery: Ammonium Carbonate, Hydrosulphide, Sulphite, and Chloride
• Oily: Paraffin, Naphthalene, Pyrene and Chrysene.
• Gases
  • unsuitable for Town Gas: Hydrogen Sulphide, Carbon Dioxide, Carbon Bisulphide, Nitrogen, Oxygen and Ammonia
  • suitable for Town Gas: Ethylene, Acetylene, Methane, Propene, Butene, plus vaporous cyclic and straight chain hydrocarbons (mainly Naphthalene, but also Toluene, Benzene and Xylene). In early town gas these were important because the main use of gas was lighting and they burn with a bright flame.

Roasting coal doesn't produce Hydrogen or Carbon Monoxide in significant quantities. Instead they were made in the gasworks by spraying hot coke immediately after roasting with water. Most of the coke remains unchanged and was sold as a clean fuel, but the water and some carbon react to produce the mixture of Hydrogen and Carbon Monoxide called Water Gas. Water Gas was always made and added to 'Coal Gas' before distribution.

Several advantages:

• Spraying water on coke that's already white hot after roasting produces more fuel gas at almost zero cost.
• The mixture sold to customers is tamer and easier to manage than coal gas.
• The heat value of gas sold to customers can be kept constant by diluting coal gas with Water Gas as required. It allows different types of coal to be roasted around the country, or in the gasworks, without customers having to adjust a multitude of burners to compensate.

Before gas was was distributed, a well-engineered combination of physical and chemical processes were staged to extract impurities and valuable by-products. In 1880 a new Gasworks was one of the most impressive technical achievements on the planet, only knocked on the head when Natural Gas and Oil became cheaper...

Dave

There was an article in the times today (Sat 22nd) page 21 about JCB developing a hydrogen fuelled IC engine

using pressurised hydrogen tanks

it produces no co and nearly zero N0X.....just water out the exhaust

so where does the water come from? if you feed an engine with h2 and atmospheric air (turbocharged) and burn it what happens to the hydrogen and oxygen? Is it destroyed? Or does it recombine to form water?

as i said I’m not a chemist

Ian -

Your last question is the correct answer.

Two atoms of Hydrogen combine with one of Oxygen to create a molecule of H20 (please forgive the full-size rather than correct subscript 2!). I.e., a molecule of water.

The two gases, which are elements, are not "destroyed". Elements are formed of atoms that cannot be destroyed except by nuclear processes. Instead, chemical combinations simply stick the elements together to form compounds with, usually, physical and chemical characteristics vastly different from those of the individual elements. This is important, as I will show.

For example, in our case here:

- Hydrogen and Oxygen are colourless, odourless, taste-less gases, of quite different densities.

- Hydrogen is flammable but does not intrinsically support combustion (though it would certainly add to a fire).

- Oxygen is not flammable, but certainly supports combustion (high-rate oxidation that emits heat).

- Hydrogen burns in the presence of Oxygen, by the two gases combining to form water....

... which is a colourless, odourless, taste-less, fairly dense liquid that is neither flammable nor supports combustion!

'

Since both gases can be derived by electrolysing water the nett trade is neutral, since the exhaust from them is water-vapour that merely joins that already in the atmosphere naturally. The total exhaust from an i.c. engine will also contain some Nitrous Oxides, but a science-teacher explained to me that these can be, and are, broken down by catalytic converters using urea - the "Ad-Blue" fluid you see sold in garages.

The problem from any "green" point of view is that water is a deceptively simple compound with some very odd properties and abilities including enormous molecular strength. So though breaking lots of it into worthwhile volumes of Hydrogen and Oxygen by electrolysis produces no awkward by-products, it demands a lot of electricity that has to be generated..... somehow.

'

From a Phsyics point of view, it absorbs a certain amount of energy (as electricity) to divorce the hydrogen from the bigamist oxygen, but when that hydrogen is then burnt the chemical reaction repays the energy (as emitted heat). Though the balance is never achieved in practical processes because they can never be 100% efficient.

'

There is actually nothing very new in all of this except that using hydrogen as a direct fuel in an i.c. engine has always proven difficult in the past, I believe due mainly to its combustion characteristics. I think the gas mixture compressed in the engine cylinder tends to detonate rather than "simply" burn, but I am not sure of that.

Nor is there anything new in storing hydrogen compressed into cylinders, and oxy-hydrogen rather than oxy-acetylene has long been the better combination for underwater flame-cutting. (The torch is lit before submerging it!)

Safety fears are somewhat specious because a cylinder of hydrogen is not only no more intrinsically dangerous than one of LPG, but leaking hydrogen can be vented to rise and disperse in the atmosphere. LPG and petrol vapour are fairly dense, collecting in low points such as car floor-pans and boat hulls. I think it is also non-toxic, though will suffocate if it displaces the oxygen available. The disadvantage is that hydrogen is odourless so a leak may not be evident, but that could be overcome with a suitable "scent" as is added to the mains supply of odourless methane that is natural-gas.

A good explanation, Nigel. Platinum and (more recently) Palladium catalysts are used to convert oxides of nitrogen and carbon monoxide emissions from petrol engine combustion to people-safe molecules. Ad-Blue is primarily used for removing the particulates from diesel engine combustion exhaust streams (although even petrol engines produce some particulates, they are ignored by most - as they are small, compared to those from diesel engines).

An ICE has advantages of a wide range of output power (roughly proportional to engine speed) whereas fuel cells generally operate at constant output (meaning that for a variable power use, some form of energy storage is required when the power required exceeds the fuel cell output)

Petrol fuelled IC engines are typically only about 25% efficient (hydrogen fuelled may be a little more) and diesels around 30%. Some very large diesel engines can be as good as 50% efficient (think multi MW marine drives).

A typical car alternator is around 50% efficient. That means that electricity for your car systems may only use 12% of the heated inputted from the fuel. Most large alternators are better than 85% efficient. Coal fired power stations typically operate at ~40% efficiency.

Electricity is regarded as a high grade energy source - it can be used effectively while being transformed into heat (100%), motive power (50-95% for conveyor belts, compressors, hydraulic pumps, driving cars, etc), chemical energy (electrolysing water for instance @70%, charging batteries @50-90+%) and a host of other uses in manufacturing and science.

The upshot of the above means that producing hydrogen by electrolysis @`70% efficiency is only viable when there is spare electrical power available at very low cost (we cannot store ‘electricity&rsquo. With renewable energy, the alternatives to transforming the excess electrical energy, to a ‘lower grade’ of energy, is to waste it (lots of wind energy generation is turned off at times for that very reason). Hydrogen production is just one option of the former.

The Danes are currently building a huge wind farm which will do just that - make electricity for immediate grid distribution or use any excess to produce hydrogen. They are streets ahead of the UK in this respect - but they do have a good resource and don’t waste as much the UK does.

This thread is a much more complex issue than envisaged by most. Local injection of high pressure stored-hydrogen might be one angle on reducing system leakages, but don’t let a load of mis-truths spoil a good news article on the beeb.

Burning hydrogen cleanly is not the same as producing it cleanly.

NDIY, Nigel is right regarding Ad-Blue. It is injected into the exhaust after the diesel particulate filter and reacts in the selective catalytic reduction system in the exhaust system to give a final outcome of nitrogen, carbon dioxide, and water. It is not designed to have any particulate reducing action. Ad-Blue is very pure urea in a de-ionized water mixture.

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Here’s an interesting update on that: **LINK**

https://www.smithsonianmag.com/smart-news/unearthed-footage-sheds-new-light-hindenburg-disaster-180977773/

MichaelG.

Why does mentioning "hydrogen" as a fuel lead some people to think "Hindenburg"? Not relevant!

As a digression though...

I did follow that link. I have seen the more complete newsreel than that usually shown, starting a moment before the fire first appears. It shows the airship approaching the mooring-mast but pitching more and more severely, with the crew trying to control it by discharging a lot of water from the bow tanks, for an appreciable time before the fire.

As it happens I listened to Mark Steel In Town this morning, an episode recorded in Bedford in 2017. He mentioned the modern airship that has been built locally, the largest in the world now; and as evidently many of the audience had done too, he saw it fly over the town earlier that day.

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But Neil didn’t actually reference ‘hydrogen as a fuel’ ... he referenced ‘Hydrogen gas supplies’

... somewhat more relevant

MichaelG.

OK, gas supplies... but it's still fuel. It was the 'Hydrogen' cue I picked up on.