The Italian Version

Blessed days as a student - albeit postgraduate, when I can take quite a lot of vacations. Indeed, tomorrow I'm off for a few days of pure rest. This is the place where I'm going:


Its exact name and location shall remain undisclosed, but thanks to DigitalGlobe ImageAtlas for the hi-res imagery: the best available for this area is 0.61 m...
And I'll be back blogging soon.
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Still too busy to write more about the Big Things, so I'm reduced again to scavenge through my traffic logs. Still, something cool always pops up.

Las visit I received was from the U.S. Department of State (domain state.gov), with the search word "dssa italy". Apparently, this is the page that attracted Google's and State Dept's attention. The visit was brief; I don't know whether I should be honored or worried about it (months ago I also received a visit from the IRS domain; that's more worrisome - if I had to pay taxes in the USA, that is).

La seconda curiosa visita viene anche questa dagli USA, ma é molto piú innocente: qualcuno che ha cercato "ricchi e poveri testi". Ma non riesco nemmeno lontanamente ad immaginare perché Altavista pensa di poterli trovare sul mio blog...
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I got my first spam comment on an old post. And it will also be the last, because I activated the proper countermeasures. And may all the spammers get acne conglobata!
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In questi tempi, nessuno tranne i pazzi furiosi si lamenta del fatto che la forza di gravitá applica agli oggetti una certa accelerazione diretta verso la Terra, oppure che un fluido che passa attraverso un letto poroso subisce una perdita di pressione proporzionale alla portata del fluido. Tutti sanno, o almeno riconoscono, che si tratta di fenomeni naturali che non possiamo alterare; possiamo soltanto adattarci alla loro esistenza.

Questo articolo, e la conseguente discussione (e pure quest'altro) sul blog dei Gemelli invece sono solo l'ultima dimostrazione del fatto che molte persone ritengono ancora che la competizione memetica ed il libero mercato siano costrutti umani*. Ovvero, non sono fanomenti fenomeni naturali ma creati dall'uomo, per cui se manifestano certe caratteristiche significa che sono stati progettati in questo modo. Il libero mercato promuove diseuguaglianza? Perché é stato creato da avidi, spietati capitalisti. La cultura americana sta vincendo la competizione memetica a livello globale? E' un complotto americano per aprire nuovi McDonalds e vendere films.

La realtá invece é diversa. La rivelazione puó essere quasi uno shock (per me lo é stato) ma la competizione memetica é un fenomeno naturale; ed il libero mercato é sostanzialmente equivalente alla competizione memetica. Le proprietá di questo fenomeno sono evoluzione lamarckiana e adattamento ambientale; effetto rete ed economie di scala. E questi aspetti sono sostanzialmente naturali, piú o meno quanto le forze trainanti. C'é pure una notevole componente di caoticitá - soprattutto nel libero mercato.

Il risultato finale é che questi enti si comportano in modi che sono governati da leggi interne che spesso producono risultati molto diversi dai nostri desideri, intenzioni o aspettative. E non possiamo fare molto per modificare la situazione; non é soltanto difficile, ma spesso proprio impossibile.

Per questi motivi il documento dell'UNESCO per la protezione delle particolaritá culturali (o come cavolo si chiama) é una farsa. Certe culture stanno scomparendo un po' per il declino demografico di certe etnie, ma principalmente perché non riescono ad interessare abbastanza persone al di fuori da una ristretta cerchia. Questo é il vero motivo, non una supposta concorrenza sleale dell'America.

Strano che i protezionisti culturali raramente si lamentino per il successo internazionale degli anime. Eppure, la cultura giapponese é piuttosto aliena per tutto il resto del mondo - escluse solo in parte Cina e Corea.

* Non sono i Gemelli a pensarla in questo modo, devo precisare. Ma evidentemente alcuni dei loro lettori si.
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Finally I found time to write an extensive article, and this one is going to be juicy: it deals with the foundations of my view of the world.

I am a mechanist agnostic.

Whether God exists or not, cannot be demonstrated deductively. This means, it takes an act of faith, of belief, to accept either of the propositions.

I do not have a precise belief in this regard; but I firmly believe that an eventual God is irrelevant in the universe and material reality. If a God does exist, he created the universe but after this initial act ceased to interfere, completely, and left the whole thing to evolve spontaneously (this kind of entity is also known as Fred). He does not send messengers, he does not inspire humans, he does not send sons or other relatives among us. He watches, or something like that. In my most cynical moments, I think that maybe Fred is having a riot of fun watching how we struggle to cope with this crazy world.

This means that my world to function requires only the Laws of Nature. No supernatural entities, no intelligent designers, no universal justice or destiny are needed. This world is mechanistic, and there is beauty to be found even there; in the perfect hexagonal symmetry of a benzene molecule or the awesome sight of a distant galaxy. And we have the means to study this universe, but often it isn't trivial, and it is likely that some questions will never be answered.

Of course, it makes no sense to worship Fred, because he does not listen to prayer; does not dispense punishment or rewards; he offers no example, counsel or comfort.
He also does not give any moral or ethical teaching.

There is only one ethical system that can logically emerge from this view: utilitarianism - the way that nature works. And indeed, I am an utilitarist, but not a pure one. I think that there are values (life, liberty, happiness, honour) which trump at least some utilitarian considerations. But in the end, I am an ethical cynic too. This is a rather complicated situation to be in, because it takes quite a lot of system analysis to take difficult ethical decisions. It would be much simpler to read into a book and find the answer to any question, but it doesn't work for me.

I was raised as a Catholic, but I found that my belief grew weaker and weaker, to the point that all the those (which are in great part good, anyway) teachings just washed over me without having any effect.

In a sense, I am a moral relativist: I believe that there is no absolute truth regarding what is good and what is evil. But I am also very distant from the post-modernist relativists: they think that all actions have equal moral value; all ethical systems are equivalent, and thus trying to convince others to change their ways, casting judgements, or simply criticizing another ethical system is utterly wrong.

Instead, I think that actions have different moral value, that certain ethical systems are inferior or superior. I reserve to myself the right to criticize any other ethical system, and while I normally don't try to "convert" other people, if they try to force their beliefs upon me I will fight back.

This is why I often disagree with Christians and others, even regarding our common enemy (the partly casual Islamo-tranzist coalition): where they see a moral imperative, I see utilitarian considerations (not that I do not have moral imperatives, however). Where they see sins I see a different lifestyle, that I can largely tolerate. Where they see the power and will of God, I see the Laws of Nature at work.

Now please notice that I only exposed my position. I know better than trying to convince others (theists, mainly, but also militant atheists) that I am right and they are wrong. I would greatly appreciate if my readers did not try to convert me in turn.
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I am sorry for the typos in my posts. Despite my attentions, quite a few still end up in the final forms of my articles. Please bear with me.
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I'm busy with my experiments, elaborating those data, writing a paper, preparing a poster for a College event and other chores. No wonder I have little time left for blogging.

But this search word is too good to let it pass unrevealed: "search italy porno catania". (Catania is a city in Sicily)

This curious visitor comes from Mauritius, a small tropical island-state. Is Italian porn so popular? Or is this the work of some Italian folk on holiday over there?
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I'm not sure wheter my blogging about equations of state an fatigue fracture does really fit within this scheme of things. But that hot-rod wacko isn't sexy in the slightest, for god's sake! What is he going to write next, about the performance of his new racing gear stick??

I wasted my time on absolutely unimportant things, feh.


This post is an obscure joke, actually...
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La nuova legge elettorale per l'Italia é stata approvata dalla Camera; deve ancora essere votata dal Senato, ma le probabilitá che venga approvata sono molto alte.

Questa legge non mi piace; io preferisco pareccho un sistema totalmente maggioritario. Perché, per dirla in breve ma completamente, provvede un filtraggio molto migliore del segnale (la volontá della maggioranza degli elettori italiani) dal rumore di fondo (le innumerevoli differenze di opinione individuali e di gruppo)*.

Comunque, questa legge é legittima e costituzionale, non lo metto in dubbio.

A parte la mia preferenza per il sistema maggioritario, ci sono altre due circostanze che mi turbano, riguardo questa legge.

Uno, é difficile non sospettare che si tratti di una manovra berlusconiana per cambiare le regole a suo favore quando la partita si avvicina alla fine. Nulla di illegale, ma disonesto sí. Anche se, ad onor del vero, non é matematicamente sicuro che tornare al sistema proporzionale fará vincere la CdL.

Due, la legge elettorale in Italia cambia con una frequenza impressionante. Siamo andati dal proporzionale puro al maggioritario parziale per poi tornare ad un proporzionale quasi puro, il tutto negli ultimi dieci anni. Questo balletto di leggi é inutile e dannoso per il paese perché provoca incertezza ed instabilitá.

E' necessario fare qualcosa per risolvere questo problema, io ritengo. Una soluzione puó essere introdurre una norma costituzionale che faccia divieto di modificare la legge elettorale in un certo termine di tempo precedente la fine (programmata, non anticipata) di una legislatura. Ad esempio si potrebbe stabilire che non é possibile modificare la legge elettorale nell'ultimo terzo di una legislatura. Ma questa soluzione non mi piace. Penso che una Costituzione non debba occuparsi cosí puntigliosamente del funzionamento di uno stato. Ed inoltre, una tale norma non potrebbe tenere conto di circostanze eccezionali od impreviste (a meno che non si crei un labirinto legislativo aggiungendo una lista di eccezioni e condizioni).

Penso che l'unica strada praticabile per limitare le modifiche alla legge elettorale sia quella di renderla una legge speciale, che richieda una ampia maggioranza delle due camere unificate per essere approvata. In questo modo si renderebbero molto piú difficili questi colpi di mano.

Certo pure questa soluzione non é ottimale (forse nemmeno praticabile, dato l'ordinamento italiano. Scusate se ho scritto minchiate finora). La cosa migliore da fare sarebbe un cambiamento radicale: modificare la Costituzione in modo da rendere il processo elettorale fortemente maggioritario e basato sui candidati (alla Camera e/o Senato) come individui, invece che membri di questo o quel partito. Una variazione in senso americano, insomma. L'altra cosa da fare sarebbe ristrutturare il Parlamento: non piú un numero fisso di Deputati, ma un numero che cambi in proporzione alla popolazione delle diverse regioni (e della Circoscrizione Estero); quindi, tre o quattro Senatori per regione (ed Estero).

Ma putroppo, non vedo alcuna speranza di un simile cambiamento all'orizzonte.

* Merito al solito DenBeste per avere proposto questo modello a proposito dei sistemi elettorali.
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In the industrial, chemical and engineering practice, it is necessary to know many properties of fluids (gases and liquids) and occasionally solids, often to a good degree of accuracy.

Density of fluids is of fundamental importance for adsorption studies (the work I'm doing at the moment) but also for almost any operation involving handling of fluids; heat capacity and thermal conductivity must be known for anything regarding heat exchange; viscosity determinates how a fluid flows (and in the case of fluids like molten polymers, the situation is pretty complex); distillation requires knowledge of the liquid/vapor equilibria of mixtures; membrane separation is based on diffusivity differences; and more unusual applications require the knowledge of more exoteric properties (enthalpy, compressibility etc). All these properties vary greatly with temperature and pressure.

If you trade in compressed and liquified gases; you want to know at what temperature the pressure in your oxygen cylinders will get close to the design limit - for obvious safety reasons. Motor oil is a high-tech fluid, and among other properties its viscosity must be as constant as possible in a wide range of temperature in order to facilitate cold starts and retain good lubricating properties when the engine runs hot. If you want to design a steam turbine, you need to know the whole shebang: liquid/vapor equilibrium, density, viscosity, heat capacity, enthalpy content and probably even more of steam - which is quite a bitch of a fluid. Finally, if you want to cause the nuclear detonation of a mass of plutonium, you must know waht pressure is required to compress it above its critical density.

Most of these properties can be measured experimentally, but it easily becomes an exceedingly difficult, expensive and time-consuming job. And sometimes it's not possible.

What would be very useful is a mathematical model, an equation into which you can simply feed your temperature and pressure, and it will churn out the value of the property you want to know. Fortunately, these equations exist, and they are called equations of state (EOS).

The first of the kind, now known as ideal or perfect gas equation of state (IG EOS) was proposed in the 18^th, 19^th at latest century and it correlates Pressure, Temperature and molar volume in this fashion:

Pv = RT

R is a constant called the gas constant; it is necessary for the equation to work but it also constitutes a sort of indication of the energy content of a gas (science is full of constants of this kind)*. This equation is very simple, ad calculations can be done with just paper and pen - or even mentally for those versed in mental arithmetic. The molar volume of gases at 0 C and 1 bar is 22.4 liters - this is one of the results of this EOS.
Molar density is the inverse of molar volume (1/v), so it's pretty straightforward to calculate it, and all other properties can be calculated with manipulations of this basic equation and using other concepts of thermodynamics.

However, pretty soon people realized that real gases do not quite behave like ideal ones; hydrogen and helium are pretty close to being ideal, but oxygen and carbon dioxide (for example) are sensibly different. Not to mention hydrocarbons. Using the IG EOS to predict their properties will result in noticeable errors. So, scientists began seeking to improve the model and have more accurate predictions.

It's not the case to enter in the mathematical details, but the method used was to add a corrective factor to the equation, a new parameter to be calculated fitting the equation to experimental data - for example, a weighed amount of gas is placed into a strong sealed container, and the pressure is recorded while varying the temperature. Or you can work at constant temperature and vary the volume of your chamber. Then you have a series of data, and with proper techniques you can calculate the parameter(s) of your EOS - parameter(s) which sometimes are temperature-dependant themselves. Basically, each new equation was a bit, sometimes even a lot, more accurate than the previous ones.

The first alternative equations of state had one or two parameters characteristic for each substance; some have three or four. One of the most popular EOS, the Peng - Robinson (the two guys who developed it) has two parameters, one temperature-dependant. This equation is used extensively for hydrocarbons and their mixtures. Although not very accurate, it is pretty simple to implement with any calculus package (Mathematica, Matlab etc).

For the case of carbon dioxide - the fluid I work with - not even the PR EOS is enough for very accurate work. Two German researchers, Span and Wagner, did a monumental work of compiling thousands of experimental data for the properties of CO₂ and using all of them to fit a monstrous equation, with literally 30 or more parameters. But their efforts paid off, because now theirs is the state-of-the-art, international standard equation of state for carbon dioxide.

Problem is, it's a nightmare to encode; but fortunately institutions such as NIST have developed software packages that do the job. So I just had to buy the software, and now I can happily copy & paste my experimental data into it, and obtain high accuracy density values in just a few seconds. Marvels of this age.

Update - last night I was in haste, so I forgot a couple of things...

* The units used for all the quantities in the equation must be consistent; in the SI system, pressure is in Pa, volume in m3, temperature in K and quantity in mol. R thus is 8.314 J / K*mol. In the fractional system... I don't even want think about that perversion!

The IG EOS is valid only for gases, while other equations of state can be used for liquids too - and most importantly, for liquid-vapor equilibria. Also solids have their own equations of state, but I've never seen one, actually. Aside from nuclear technology, the modification of solids at high pressure is of interest in the field of geology, given that in the depths of the Earth pressure reaches unbelievable extremes.
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I almost wanted to title this post "I Love SDB", but even after a free dinner & drinks offered by BP I'm not out of my mind enough for that.

Anyway... Steven got a lot of referrers for a comment he made on some blog, and in response he posted two big pictures of cute anime babes in underwear¹ - and one of them wields Made in Tokyo Kalashnikov! That's very cool, almost outstanding.

Regarding his previous entry, the bright side of it is that the ferrocyanide ion is very stable, and it's hard like hell to make hydrocyanic acid from it, fortunately. And don't ask for details.

1. Either underwear or bikinis. For the future, scroll down to his 20051012 entry.
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During the early steam trains age, the owners of these trains (which sometimes were just sort of circus attractions, running on a small circular track) noticed a strange phenomenon: sometimes, steels rails - and even axles - just broke apart even if the load applied to them was well below the strength of the rails. Besides being curious in itself, this fact obviously had also serious implications: you cannot build a successful railway if your rails break apart for no apparent reason.

So, the engineers of the age began to study the situation, and built machines that could simulate the operative loads on rails and carriage axles, and discovered a very interesting fact: if a stress below the maximum design load of a mechanical part is applied and released repeatedly (thousands of times), fractures will develop in the part until its strength is so low that it will break even under absolutely normal operative loads.
And this is fatigue. If you want to try it at home, take a piece of iron or copper wire of 3 - 5 mm diameter, some 30 cm long and try to bend it back and forth in the same point: after a certain number of cycles (that depends mainly from the properties of the specific wire) the wire will break at the bending point, revealing a peculiarly ruvid surface, with tiny crystal faces in view.

Since then, fatigue has been studied extensively, and down to the microscopic level of how these fatigue cracks form and grow in the material's structure. Metals are the prime candidates for fatigue cracking - especially light alloys - but almost any material can suffer from it. Cracks generally originate where a stress concentration occurs: it can be something macroscopic such as a gas bubble or piece of slag remaining inside the metal from its melting and forging, or a tiny crystal defect, or a notch caused by mishandling of the part, or the stress concentration at a square corner.

If you take another wire like the one in the example above, and make a notch in it with a hacksaw, file or chisel and bend it back and forth again, it will break after a smaller number of cycles. Avoiding square corners is common design practice in many cases: when I designed a small pressure vessel, the senior engineer supervising the project told me to design the vessel with radiuses instead of square corners at the wall-bottom junction and at the flange-body junction, expressly to prevent stress concentration.

A fatigue crack is born as a tiny one, just microns deep. But the stresses will concentrate at the tip of the crack, and make it a bit deeper with each cycle - until eventually the piece fractures. A crack's growth can also stop, if it encounters a region of material with different characteristics - but this is an issue I do not know very well.

Fatigue is an issue in almost all metal structures, but it becomes of life and death (not to mention economic) importance in aeronautics - and railways in the second place.

These are both fields of high stresses: trains travel at less than 300 km/h in general, but they are massive things, with big steel bogies, wheels and axles. With a huge mass, even a small accelaration is enough to produce a considerable force, and the rolling action of a wheel on a rail is a very violent phenomenon, that leaves the top layer (a few micrometers) of the rail completely messed up. Fatigue cracks can generate in this layer, and grow vertically in the rail with the bending loads that a train wheel applies to the rail. Following one serious accident in England, investigators discovered that, due to fatigue cracks, a 1 m long section of rail disintegrated in 200-odd pieces when the train passed over it.

Ah, finally Blogger behaved. Stay tuned for the second part then.
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It's Sunday, the classic day for cleaning and tidying up. So, while a lamb joint is roastin in my oven, I tidied up my blog.

I moved the inactive blogs in a special category, added the Tocqueville banner, moved The Belmont Club into the newly created Australia category - because Wretchard writes from Australia, not the USA as previously thought.

Good reading!
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"rising dump course with paraffina"

Via MSN Search, and notice that the first four words are English (more or less), while paraffina is Italian (it would be paraffin in English). Friggin' illiterates. (Via 82.56.102.# and interbusiness.it you sucker).
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This morning I took the bus, and things went even worse than usual. Normally, when I take the bus in the morning, the first few kilometers are of slowly-moving bumper-to-bumper traffic. This morning, it was stop-and-go traffic, for almost all of the journey. A road is partially closed because they're laying new water mains, and another one was blocked by a particularly dumb cabbie who decided to park his cab right in the middle of the road while loading a customer's luggage. A lorry driver expressed his disappointment at the situation shouting not exactly loving words at the cabbie. All in all, it took one good hour for a journey that usually lasts more or less half a hour, even during peak hours.

Driving a car would not help much, however. Actually, it is more likely to provoke stress if not road rage. So what's the solution? For me, this is the solution:


A cool supermoto: scorching acceleration and great manoeuvrability (plus the satisfying rumble of a single-cylinder 4-stroke engine) make it the ideal city vehicle, to slalom between traffic and queues. I also already have a motorcycle driving licence; I only lack the budget, dammit...
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Capita spesso di sentire e leggere discorsi, anche lunghi, a proposito di "occupazione illegale" - di Cipro da parte della Turchia, nel caso specifico; oppure del "diritto di esistere" di Israele; oppure del "diritto al nucleare" dell'Iran.

Ma cosí come sono posti questi ragionamenti non hanno senso. E' inutile cercare di discutere sui contenuti di queste posizioni, perché non contengono nulla. Nel campo dei rapporti internazionali, diritto, leggi e pure trattati valgono la carta sulla quale sono scritti. Quello che conta davvero é la forza, politica, economica e militare di un Paese, e la volontá di eventualmente usarla per i propri interessi particolari.

I fattori importanti sono intenzioni e capacitá, non quello che sta scritto nei documenti dell'ONU. Quando é possibile esistere per uno Stato? Quando i suoi cittadini hanno l'intenzione e la capacitá di formare uno Stato e difenderlo da nemici sia domestici che stranieri. Questo spesso richiede di formare alleanze con altri Stati (meglio se i piú potenti), ma non é il consenso internazionale che definisce la legittimitá di uno Stato.

Una legittimitá concessa in questo modo potrebbe anche essere ritirata: per fare un esempio paradossale, pensate se l'ONU in seduta plenaria un giorno deliberasse che la Francia (uno stato preso a caso, eh...) deve essere smembrata in un certo numero di staterelli indipendenti...

Quando é possibile per uno Stato occupare un territorio? Quando ne ha le intenzioni e le capacitá militari. Tutte le risoluzioni ONU e le "parole di ferma condanna" non bastano nemmeno a fermare un singolo camion da trasporto militare.

Quando é possibile per uno Stato dotarsi di un arsenale nucleare? Quando i suoi leader ne hanno le intenzioni, e riescono ad ottenere le capacitá. Possono procurarsi armi giá pronte, oppure tutte o parte delle tecnologie ed attrezzature necessarie. E le ispezioni dell'IAEA non hanno mai fermato nessuno. Solo se un'altra potenza ha la volontá e la capacitá di bloccare con la forza il tuo programma nucleare si arriva da qualche parte - come la distruzione del reattore Osirak da parte di Israele ci insegna*.

Questa é la realtá; nei rapporti internazionali é il piú forte ad avere ragione. E non basta immaginare un mondo diverso, oppure scriverlo su carta, per cambiare le cose.

* Quella missione non finisce mai di meravigliarmi. Era difficile, pericolosa e faticosa, eppure é stata pianificata ed eseguita in modo pressoché perfetto. Un hurra! per la IAF.
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I haven't received many weird visits lately, but today something tasty was in the logs.

A visit from the domain dolcegabbana.it (IP begins with 62.94) that reached my blog searching for "nitrato ammonio" (ammonium nitrate). A couple of gay metrosexual fashion designers and an explosive chemical are a disturbing combination, I tell ya...

Another visit from Republic of Korea (ISP Korea Telecom); this one searching for "sri lanka sex gals". If I were you, I'd be content enough with Korean girls...
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The accident that happened yesterday in my laboratory did not have any serious consequence - except some economic damage - but it's a good exaple of how a failure in a complex system can trigger a series of events ending in serious trouble. The accident wasn't fault of anyone in particular either; laymen always want to find a culprit but engineers know better.

However, before explaining the accident in detail, I have to introduce a few basic concepts of reaction engineering. For a chemical reactor, conversion is the fraction of reactants that is converted into products, and it depends from the residence time (among other factors): residence time is defined as the average time the reactants spend inside the reactor; it is easily calculated dividing the reactor volume by the volumetric flow of the reagents. In my case, the reactor volume is 300 mL, and with a reactant flow of 300 mL/min the residence time would be 1 minute.

Generally, research reactors work at low (10% or less) conversion. There are a number of reasons for this; one is that at high conversion it is not possible to study certain phenomena. But the main reason is that in case of exothermic reactions, keeping the conversion low will produce only a little amount of heat, amount that can easily be handled without recurring to cooling systems. To accomplish this, the simplest way is to have short residence times, and thus pretty high feed flow - compared to the reactor volume.

Another thing to notice is that the catalysts used in industry tend to deactivate - they lose their catalytic activity with time. This can be due to contamination with substances that bond to the active sites on the catalyst (sulphur is the most common), or to modifications of the physical/crystal structure of the catalyst itself. Obviously, chemical industries are interested in finding ways to reactivate their catalysts in situ, because it potentially saves money.

Thus, this Big Chemical Industry contacted my supervisor and his job was to find a way to reactivate a catalyst being used by this BCI. For the task, he used a Berty reactor, that is a sort of sturdy metal container (made at least of stainless steel, but probably of something even more resistant to chemical attacks) with a bolted cover, a stainless steel or copper seal, a heating system and a stirrer. Yes, because if the contents of a reactor are well mixed, one does not have to worry about concentration inhomogeneties inside the reactor itself. For this reason, the catalyst is placed in a fine mesh basket, in turn fitted inside an impeller that can turn at different speeds thanks to an electronically controlled electric motor.

To avoid the severe complication of a high-temperature, high-pressure seal around a rotating shaft, the impeller is driven magnetically: the shaft connected to the motor rotates a magnet just underneath the bottom of the reactor, and this magnetic field in turn rotates the impeller (that probably has a magnet embedded into it too). However, even with this design the stirrer shaft gets hot, and it rotates on a water-cooled bearing. Total cost of the new rig, around £40 000.

The furnace heating system has three zones each one with an indipendent controller, plus a fourth controller for the interior of the reactor itself, connected to a thermocouple placed inside the reactor. All these controllers work together to keep the temperatures at the set levels within less than 1 K deviations - and are set to shut off the heaters if the temperature exceeds a certain setpoint.

So, my supervisor performed a certain procedure for the reactivation of the catalyst and when it was completed he begun feeding reactants (a mixture of hydrogen and carbon monoxide, I think - I'm not working on that project) to check whether the catalyst was reactivated properly.

But at certain point, for reasons under investigation, the automatic shutoff valve on the feed line tripped and shut off the reactant flow - or better, allowed only a very small floe through it. With a very small flow, the residence time increased sharply, and the reaction went to almost 100% conversion, producing a large amount of heat. The temperature in the reactor increased to 300 C in an occurrence known as runaway reaction, and even if the automatic protections shut off the heaters it was too late: heath transferred through the stirrer shaft damaged its bearing. My supervisor could do nothing but turning all the whole thing off, and feeding the reactor with a mixture of hydrogen and nytrogen while it cools down. Now, he's stuck with a non-working reactor loaded with a pyrophoric catalyst and so it cannot be opened to check for eventual damage, and it is not possible to run reactions in order to proceed with the project - and the BCI isn't very happy about that. The catalyst had been reactivated, because an inactive catalyst does not cause a runaway reaction, but there are no useful data to measure the catalyst activity. The stirrer shaft bearing will have to be replaced, but the shaft itself may have been scratched. And the rig was produced by an US company that has no service centres in Europe.

So, a stupid incovenience caused cascading failures that led to a rather serious accident - that fortunately did occur during the day and not at night. And if things are already bad enough on this scale, on industrial scale a runaway reaction can cause serious economic damage, and even catastrophic explosions with several casualties. For these reasons, chemical plants have features such as relief valves, emergency cooling systems, nitrogen injection lines (nitrogen is inert, so it will flush the reactants away and help with cooling) and even reaction inhibitors injection systems.

Update 03/20: No, the catalyst basket does not rotate; only the impeller at the bottom of the reactor does. But the catalyst basket has vertical baffles at its periphery to generate turbulence and hence improve mixing. However, the graphite bearing of the impeller disintegrated in the accident, and it needs to be replaced - with considerable loss of time and expense.

There is another aspect to runaway reactions: the rate of chemical reactions increases with temperature, so when a reaction produces excessive heat (you can see it as power expressed in Watts) it also becomes faster, thus producing even more heat in a vicious circle.
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