exchemist

A bit on methane pyrolysis here from Wiki. Apparently this is called "turquoise" hydrogen, being intermediate between "blue" and "green" hydrogen: QUOTE Methane pyrolysis for hydrogen[edit] Illustrating inputs and outputs of methane pyrolysis, an efficient one-step process to produce Hydrogen and no greenhouse gas Methane pyrolysis[30] is a non-polluting industrial process for "turquoise" hydrogen production from methane by removing solid carbon from natural gas. This one step process produces non-polluting hydrogen in high volume at low cost (less than Steam reforming with Carbon sequestration). Only water is released when hydrogen is used as the fuel for fuel-cell electric heavy truck transportation,[31][32][33][34][35] gas turbine electric power generation,[36][37] and hydrogen for industrial processes including producing ammonia fertilizer and cement.[38][39] Methane pyrolysis is the process operating around 1065 °C for producing hydrogen from natural gas that allows removal of carbon easily (solid non-polluting carbon is a byproduct of the process).[40][41]The industrial quality solid carbon can then be sold or landfilled and is not released into the atmosphere, no emission of greenhouse gas (GHG), no ground water pollution in landfill. Volume production is being evaluated in the BASF "methane pyrolysis at scale" pilot plant,[42] the chemical engineering team at University of California - Santa Barbara[43] and in such research laboratories as Karlsruhe Liquid-metal Laboratory (KALLA).[44] Power for process heat consumed is only one seventh of the power consumed in the water electrolysis method for producing hydrogen.[45] UNQUOTE This looks quite promising. I'm not sure what we would do with all the elemental carbon this would produce, though. I have not looked into what applications there are for it. Maybe we just drop it down coal mines. That would be a fitting irony.

Agreed, it will be more costly than the industry price for electricity. But that price won't include the cost of the distribution network, so if electrically generated it could be little more than double the industry price of gas (assuming the marginal kWh will be generated from a heat engine, for some years to come), I should have thought. Alternatively, hydrogen could be generated from pyrolysis of natural gas. The economics of these methods will be one of the things that has to be optimised by competition. But the advantage of hydrogen for heating would be that it would avoid the huge capital cost and disruption to the householder of buying a heat pump and retrofitting underfloor heating to old housing stock. Don't get me wrong, I'm not necessarily wedded to hydrogen as the solution. I just think it has some obvious practical merits for certain applications and needs to be looked at seriously.

Hmm. I am more interested in what we can actually do, here and now, given the infrastructure we have inherited, than in revisiting what we might or might not have done differently years ago. Climate change can't wait for perfect solutions. And in my opinion (not being a man of the left) I think it would be a mistake to expect governments to pick winners. I think it is better for them to encourage different technologies, allow them to compete and over time we will see which ones turn out to have the most scope for optimisation. What I mean by optimisation, in this context, is not merely what is technically best, but all the things in society that enable a solution to gain traction. Then again, we may find it is better to diversify and use more than one route than to put all our eggs in one basket. Other contributors have spoken of hydrogen being "hyped". I must say I am not aware of any noticeable hype around hydrogen. Almost everything I read seems to be about the electric car issue. Not many people are talking about HGVs and those that are starting to talk in the media about domestic heating seem preoccupied with heat pumps, even those these cost 5 times as much as a gas boiler and put out heat at only 50C max, instead of the 65C for which most central heating system are designed. So there are huge issues to overcome to make heat pumps realistic for most householders. On a personal note, I have been thinking of getting a heat pump for my large Victorian house. This will cost me a bit, and will never pay back, given that electricity costs 3-4 times as much as gas, per kWh. However I do draw the line at ripping up all the floorboards as well, to install the underfloor heating pipes required to make the low-grade heat from the pump sufficient to warm the house. Millions of others will face this issue. This is one of the reasons why I can see the logic in converting the gas network to hydrogen, either fully or at 20% dose rate as a medium term measure.

Yes, that's what I assumed he meant by "jelly": the kids' dessert type thing. But I take @zapatos's point that you can make a fruit jelly, i.e. a stiff jam from strained fruit, with added pectin, i.e. without adding gelatin.

Pectin alone allows jam to set, but that is not really jelly. For jelly, my understanding is you need to add gelatin. Temperature is crucial. Jelly melts. To get it to set, you need it to cool. If it's boiling it will never set. But when making jam, you need to reach a certain temperature to release the pectin before you cool it, which is when it then sets. That may be what you have in mind. I'm not an expert on jam, but I do make a ham and parsley terrine, with gelatin, which one buys in sheets that are dissolved in warm stock before being poured over the terrine mixture. But then you need to pop it in the frdige for some hours to allow the gel to form.

I'm sure other income streams also help, but the big boys do hedge - and have been undercut by the people that don't, who are now going bust as a result [cue circus music and clowns]. The rest of your post sounds a bit Irish: "If I were you I wouldn't start from here". But from a thermodynamic efficiency point of view it made no sense in most countries to use electricity for heating of any kind. Norway and Switzerland had hydro-electricity, but the rest of us were stuck with heat engines, so we wasted over half the fuel we burnt before we even switched on our electric fires. (And cooking with electricity is crap, even to this day). It is only with our current knowledge of climate change and 20:20 hindsight that we can reappraise the 60s and say we got it wrong. As I think Charlton Heston's character says in one of the Planet of the Apes films, "We are here and it is now." The issue is what do we do, given the legacy infrastructure and the inertial effects in society we have inherited. It is in that context that hydrogen may have a place.

I find this unconvincing. Sure the risks are somewhat different with hydrogen but I don't see that they are qualitatively greater. Hydrogen may diffuse through a leak a bit faster than larger molecules but then it dissipates more rapidly too. Energy release per unit mass is not the relevant yardstick. Volume is more relevant in practice. There is a piece on the risks of hydrogen here, from a researcher at Washington State University: https://hydrogen.wsu.edu/2017/03/17/so-just-how-dangerous-is-hydrogen-fuel/ The conclusion seems to be the quote from an experienced hydrogen expert: “Hydrogen is no better, nor worse, than any other fuel. You just have to know the rules for working with hydrogen.”

Both, inevitably. Energy is big business, in terms of risk*, capital investment and profits, so it will always be to a large extent the preserve of big business. But obviously the people will also benefit, since replacement of fossil fuel by hydrogen, for transport fuel and heating, offers one way to combat climate change, which will adversely affect the whole of humanity. Big business is run by people too. *The gas crisis in the UK at the moment is one illustration: the small suppliers failed to hedge. And now they are going bust. A few years ago the fashion was to whine about supposedly excessive profits made by the suppliers. Now that the gas price has shot up, everyone is making a thundering loss and only the big companies that hedged can survive, because they planned (and priced) for that risk.

Buncefield. Ronan Point was first and foremost a building standards disaster, rather than a gas disaster: a properly built block would never have collapsed due to a domestic gas explosion. But yes, any inflammable fuel presents a hazard and there will be accidents, though we get better every year at preventing them. What I'm saying is I see no reason to think hydrogen will be fundamentally worse in that respect than the other liquid and gaseous fuels that we currently use.

Unlike you, perhaps, I was not alive in 1927 or 1934, so, er, no, I don't remember these two events. If you have to rake through the history of the early c.20th to find examples - at least one of which was apparently due to criminally negligent safety procedures - I think you make my point for me. Since that time, by the way, there have been great numbers of refinery and fuel storage explosions involving liquid hydrocarbon fuels, in spite of the vast improvements in safety that have been made in the 80+ years since these incidents. But for the application I was discussing, we are talking of hydrogen being blended into methane for heating. I can see no reason to think this would pose a greater risk than methane itself.

I must admit I don't see the relevance of this. So far as I can see there is nothing about hydrogen that makes it uniquely dangerous, compared to other combustible gases. At least, I am not aware of a track record of industrial disasters involving hydrogen that would suggest it is particularly risky. What do you have in mind? And the poisoning you refer to was carbon monoxide poisoning, due to the use of synthesis gas (CO+H2) for domestic purposes. But nobody is suggesting the use of synthesis gas as a fuel. (Though production of syngas from steam reforming of methane, followed by the shift reaction to convert the CO (+H2O) to CO2 plus more hydrogen, is one way to make the hydrogen, the problem of course being what to do with the CO2. Pyrolysis of methane should in principle be better, as the byproduct is elemental carbon).

Are you seriously asking this forum how to "take", i.e. steal, money from a bank in Baroda, in India?

Yes gold is a precious metal but so is platinum, which is widely used as a catalyst in industrial processes. You may well be right about hydrogen as transport fuel for cars, though it may be a good option for heavy goods vehicles, for which the size and weight of batteries is apparently a real problem. Also, one critical area of carbon emission you do not address is domestic heating, which is by natural gas in many parts of the world. Keele University has been trialling the use of hydrogen to augment methane in domestic gas supplies. Apparently you can mix 20% into the gas without any need for changing burners: https://www.keele.ac.uk/discover/news/2020/january/hydeploy-goes-live/at-keele-university.php. While this is obviously far from a full solution, we cannot afford to wait for perfect solutions to be developed. The use of hydrogen can make a real dent in CO2 emissions, even as a partial replacement for natural gas. Every little helps get a country towards its CO2 milestones. The beauty of it is that it can use existing infrastructure. By contrast, wholesale conversion to electric heat pumps will necessitate massive expenditure by the householder. Pumps are expensive AND you have to change all the radiators for underfloor heating, to get enough heat out of the low temperature (~50C max) heat that a heat pump produces. Eventually this will involve recabling all the streets to deal with the extra electricity demand (probably also necessary because of charging of electric cars of course). None of that is going to happen in a hurry. I think we need to be looking at a pathway to lower emissions that involves a series of partial, temporary and quick measures, as well as the longer-term full solutions that will be slower to implement. It seems to me that hydrogen may have a useful part to play in that. Once hydrogen is in production for adding to gas supplies, it will be an easier step to set up a hydrogen refuelling network for HGVs. In any commercial operation someone has to move first and then other applications will become viable and will follow. The world will benefit from a VHS/Betamax type commercial contest between hydrogen and electricity, in my opinion. We cannot foresee all the economics, the scope for optimisation or the knock-on effects (cobalt and rare earth mining may come to bite us in the arse in a number of ways, for example). So I think governments should encourage several approaches in parallel, rather than attempting to pick winners, and thereby harness the power and ingenuity of commercial competition.

So they do use use copper salts. Interesting. Do you know how, I mean where one puts this in the tube?

Yes, thanks, that's what @joigus told me.

Right. But in gas discharge tubes? I doubt that CuCl2 is used, though if it were I assume it would be to produce a green colour. Krypton glows yellowish-green, I know. (Perhaps that accounts for the rather sickly yellow-green of older French traffic lights.) But, looking this up, I see that many of today's so-called "neon" lighting tubes are in fact fluorescent, relying on a coating on the glass to produce the colour, rather than direct emission from the gas inside. What I am having difficulty tracking down is what fluorescent material is used to produce green. My first guess would be an organic dye. Any idea?

Not quite, it is a proton (and an electron) that you would need to remove from an atom of mercury, in order to convert it to an atom of gold. It is the number of protons in the nucleus (and the corresponding number of electrons to keep it electrically neutral) that determines what element an atom is. But indeed, if you were to remove 2 protons and 2 electrons from a mercury atom, you would have an atom of platinum. N.B. If you were instead to remove neutrons from the nucleus, you would just have a different isotope of the same element as before. It is the electrons that determine the chemical properties that define an element, and the number of electrons goes with the number of protons.

I don't think this is quite right. Magnetism and induction play no part in the operation of a gas discharge tube, so far as I am aware, except to generate the high voltage needed to strike the discharge in the first place. It's simply an electrical discharge that ionises the gas, which then emits light of a characteristic colour as the electrons recombine with the ions. I am also unaware that CuCl2 is used to modify the colour. Can you provide a reference for this? Since the phenomenon is due to atomic emission, I'm not sure that sending a discharge through chemical compounds would do anything other than to excite the emission spectra of the constituent atoms.

Aha. Thanks very much.

I barely remember anything about catenaries, but I thought they were hyperbolic cosine functions, not tangents.

Look it up on the internet. There is no point in anyone here paraphrasing widely available basic science. If you have a more specific issue, by all means come back here and ask about it. If you are not a bot, that is.

I suppose what you are suggesting, in effect, is to develop cyanobacteria with a higher photosynthetic efficiency. From this Wiki article: https://en.wikipedia.org/wiki/Photosynthetic_efficiency there does appear to be scope for that, at least from the thermodynamic point of view. Interestingly, I see from the same article that cyanobacteria, today, are still thought to be responsible for 20-30% of the oxygen generation on the planet, in spite of all plants that now also contribute. So they can make a difference, certainly. I'll let the biologists comment on whether such a thing could be feasible. I imagine one issue would be that we would get a "bloom" of these super-efficient cyanobacteria in the oceans, due to the biomass they would generate from their enhanced photosynthesis. This might - probably would - screw up the ecosystem of the oceans in various unpredictable ways. It feels risky to me.

It is not clear to me what you mean by "slag". How does calling it that add to understanding? Slag is extraneous material, separated from the desired metal in the process of ore smelting, which is a chemical reduction, generally from oxides. So far as I know, it is not thought that a chemical reduction from oxides is how the metallic core of the Earth came to form. The evidence from meteorites seems to me to suggest that iron and nickel exist in space debris already in elemental form.

It's not p² if A and B are not present at the same concentration, which they are not in a buffer solution, for instance. As I say, I suspect the questioner's problem related to something like that. But since they have not been back, we can't know for sure.

Erm the numerator should be the product of the concentrations of the dissociated ions: [ A ]x[ B ]/[AB] = Kd And I think the questioner is asking about the situation in which [A]=/= [ B ] , e.g. an acetic acid/acetate buffer, or something like that. I suppose what the statement in question is driving at is that is if [ B ] << Kd, then the ratio [A]/[AB] will have to be >> Kd, so that when multiplied by [ B ] it gives Kd. But since, for weak acids and bases, K <<1 , it is not necessary for [A] >> [AB] to achieve that. .......I think...... For example, with acetic acid, Kd = 1.8 x 10⁻⁵ = [H+] x [acetate]/[acetic acid]. So if, for the sake of argument, [H+] is also 1.8 x 10⁻⁵, then the [acetate]/acetic acid] ratio would be 1/1. So I too am a bit baffled by the statement our questioner is querying.