Project Engineering Of Process Plants Howard F Rase Pdf Converter
Project engineering of process plants by Howard F. Rase, 1957,Wiley edition, in English. School of Engineering of Antioqu. This is an ebook in PDF format entitled piping design for process plants howard f rase. Project Engineering Of Process Plants Howard F Rase Pdf Editor. El Factor Aladino Pdf Converter. Log in Log out Edit. You can do it.
Summary 1) Power supply design is coming along 2) Final design will require an embedded Arduino Nano 3) Final design will use a laptop (or desktop) as display Random Status A lot of little things are happening with the project but nothing of special note, so I won't post this to the feed. My DigiKey order came in, I'm working up the various device interface software, nothing exceptional. I'm looking into generating Hydrogen on a small scale, and collecting plumbing for the experimental setup. I've resolved the safety issue using a lasercut holder for the transducer with rubber feet so it doesn't skitter across the table when energized, and a sculpted-foam parasol to catch the ultrasonic energy. (Which looks vaguely like to the starship enterprise.). at 06:29.
Summary 1) The new driver board works 2) An ATX supply makes a good DC supply for the driver 3) An ATX SMPS transformer can drive an ultrasonic transducer 4) I've ordered parts from DigiKey 5) My ears hurt, and I don't know why. ATX supply makes a good DC supply I'm using a discarded ATX supply as the DC supply for the ultrasonic driver board. With 12 volts at 15 amps, the system can supply 180 watts of drive power to the transducer circuit. The biggest transducer I can find on eBay is 120 watts, so the range is good. I mounted the supply on a board with decent bus connections and a current monitor tap.
Harbor Freight was giving out free DVMs at one point, so I got a bunch and use them as embedded current/voltage monitors. The system is pushing 5.23 amps in the image below. The new driver board works The driver board, which uses an SMPS transformer scavenged from a different ATX supply, works. The transformer generates enough voltage to drive quite a bit of power through the transducer at resonance - I've had the system 'accidentally' up to 17 amps, which is 200 watts, or double the rated transducer output.
It's a bit noisy, so I have to figure out some way of filtering. Also, I have to add some circuit protections such as zeners on the driver gates and such. Maybe a bypass cap on the gates as well.
The power driver is the perfboard sitting in front of the current meter (yellow-stripe transformer). SMPS is working, manually The SMPS circuit is working manually; meaning, I can adjust the frequency and duty cycle using two pots. I'm waiting on some parts from DigiKey, then I'll be able to hook the system up to an Arduino to monitor and control frequency and power. My ears are still ringing While attempting to get a picture of the system pushing 10 amps (120 watts), the system accidentally ran up to 17 amps for a few moments.
Despite immediately shutting down the system, the transducer managed to walk across the table (no mean feat at 28kHz) and my head has been ringing ever since. And I never heard a thing. I suppose this is the ultrasonic version of playing with lasers, I'll have to come up with some type of safety gear to protect myself. Maybe earplugs? Have to do some research. at 08:11. A quick interlude M.Bindhammer's proposes making hand-held chemical reactors for the synthesis of Aspirin.
Whether making Aspirin locally is cost-effective or not, I like the idea of hand-held chemical reactors that anyone can make. If the 'proof of concept' can be made with Aspirin, then his ideas may lead to a wide array of hand-held chemical processing components. We have a laser cutter at, so I offered to make and send him some prototypes.
The results are below. The first one on the left is a vacuum filtration system. You put a section of filter in the horizontal slot at the top, then connect a vacuum pump to the passage leading from the side. (Doesn't photograph well - see his project page for info.) The second one (middle) looks a lot like a reflux distillation system, which would be totally awesome if that's what it is & it can be made to work. The third one (right) is how the plastic comes from the laser: sticky paper protecting the surface, and without the intervening blocks removed.
These are comprised of 3 acrylic pieces: a clear face and back plate (upper left) with 0.3' ivory acrylic in between. To assemble, you line up the middles on the plates, then dribble a little methylene chloride (MEC) at the interfaces using a syringe. MEC, an acrylic solvent, gets soaked up by capillary action and dissolves some of the acrylic. Then it evaporates, leaving the acrylic pieces welded together.
If I understand his process, acrylic.should. tolerate the temperatures he needs for his synthesis, and should be immune to the reagents.
(And if not, it's still a good material for a physical prototype.) Check out his for more info. His ideas hold a lot of promise. Power supply development is proceeding apace I figured out a lot about computer PSU transformers, and now have a good idea of which ones are good to use for this application; meaning, I can now write a build procedure that describes to others what to look for when scrounging for this part. If everything holds as I think it should, anyone who wants to build an ultrasonic supply can use one PSU for power and cannibalize another one for this singular-and-difficult-to-find part. I got my UC3525 SMPS controllers running on a breadboard, and made a new power control board, shown below. Testing starts tomorrow.
at 03:39. In the spring a young man's fancy lightly turns to thoughts of. More than a third of the Hackaday prize time has passed! Have to make some progress real soon or curtail the project goals! A status update follows.
The lathe at is still offline, so I haven't been able to do any more horn tuning. Next week 'fer sure.
I cast two new horns by way of a casting demo at the space - a 2nd horn for my small (50 Watt) transducer, and one for the large (100 Watt) transducer. I've got pics and intend to make a full blog post (two, actually) with instructions, tips and tricks, etc. (ProTip: Don't run the kiln from an extension cord, at the hackerspace, as a casting demo. Kilns and extension cords don't mix. Now I know.) After the abortive demo, one of the members offered me a piece of round-stock aluminum that's just the right diameter to make the bigger horn. That's about $30 of stock in one piece right there. Thanks, Adam!
And apropos of nothing, this is why I cast horns instead of, for example, ordering stock from McMaster Carr. I'm not Tony Stark. (But to be fair, Stark himself, so he too uses this method.) The PWM controller chips (ziplock bag in middle) have just now arrived, I haven't had a chance to breadboard any. My frequency generator has poor resolution at 28KHz, so I made up a 555-timer squarewave generator (leftmost board) with a 10-turn pot. The pot sits in the middle of the frequency range of the transducer, so there's a lot of resolution with little drift. I also breadboarded a SMPS transformer from a computer PSU and a drive transistor (lower-middle board).
I also pulled two more transformers for comparison (upper right). The good news is that the transformer generates 200 volts AC from a 12 volt supply! This is about the right voltage to run 100 watt transducers off-resonance, which means that anyone who wants to make the circuit can get the only expensive-and-hard-to-find part from a junked computer.
It also means said hacker can run the circuit from a 10-amp 12-volt supply - in all likelihood an old computer PSU will suffice. Time will tell if this is right.) But this also means I can't show any progress. The 200 volts would push too much power through the transducer, so I have to get a PWM circuit running that will control power before I can show anything working. Right now I'm limiting power by crowbar'ing a supply that doesn't have overcurrent protection, and that's not an optimal solution. THANK YOU to everyone who signed up to follow the project & gave out skulls! Getting the E-mail notices from followers/skulls makes me happy, and I save every one. (Not making that up.).
at 18:05. Summary I'm designing a hobbyist power supply for ultrasonic transducers in the 100 watt range, with these goals: 1) Automatic resonance seeking 2) Variable power output 3) Microcontroller measurement and control 4) Generally bullet-proof and safe Circuit and an explanation are posted below. More Difficulties Someone at took the lathe offline and didn't tell anyone, so I'm blocked from making transducer horns for the moment. They won't let me strangle him, but to be fair, they won't let anyone else strangle him either. So I'm concentrating on a new power supply circuit for hobbyists which won't burn out and has some useful features.
NOTE: This is very much a work in progress. I'm waiting on some parts, I haven't bread-boarded and tested, and it doesn't make sense to capture a circuit before you know it will work. Also, I'm not an electronics engineer and this puts me out of my comfort zone, so if you see something fundamentally wrong with the circuit, please let me know. Switcher Compare with the supply.
The switcher uses the same standard totem-pole configuration, but with a proper DC supply instead of cheaply-rectified AC mains. The user must supply their own 120 watt DC supply in the 12V - 80V range, but these are.common. A 30 volt 10 amp supply goes for $10 on eBay: it's safe, reliable, and cheap. You can even put two of them in series for higher voltages! (I've never done this, but I'm told it will work.) Switch mode supplies have isolated outputs, so it's OK to connect the outputs in series. I'd.like. a system that would work from 12V, thus driven from a computer PSU (those are.really.
common), but this depends on the specs of the SMPS transformer. I'll know more a bit later in the project. The transistors are a wee bit overspec for the application (35A, 600V). The difference between '50% more than needed' and 'insanely overpowered' is a couple of dollars (like, $2), and I want this to be bullet proof.
The transistors are typically what burns out if the user makes a mistake, and we can let the fuse do its 'goddam job for once. On the output side, the capacitor and inductor form a low-pass filter that turns the square-wave into a sine wave. The mathematical formula for a square wave is: Where 'A' is the square wave amplitude, and 'f' is the frequency.
If the low-pass filter has a cutoff somewhere between f and 3f, the higher frequencies will be suppressed, presenting only the fundamental to the transducer. As a bonus, the result is slightly higher voltage than the original square wave due to the 4/pi term. The capacitor is TBD because the inductor is a SMPS transformer and I don't know what that inductance is yet.
Needs to be high voltage with low ESR - probably polypropylene. Synchronization and Power measurement In addition to the transducer, the output goes through an Allegro hall-effect current sensor via PWR-1 and PWR-2, from the switcher. The Allegro chip generates a voltage proportional to the current through the transducer. It has low resistance (a few m Ω), 2KV isolation, and an 80kHz bandwidth. This one chip solves a whole lot of issues. The signal from the Allegro chip becomes two outputs: a voltage proportional to current, and a frequency synchronous pulse train.
The lower path routes the sin wave through an active rectifier, followed by an RC integrator. The output is a DC voltage proportional to the current through the transducer, which is delivered as feedback to the PWM controller. The upper path requires a bit of explanation.
The SG2535 controller driving the switcher has a 'synchronize' input that can be used to slave the internal oscillator to an external clock. The slave signal is a pulse that switches the oscillator from its charge cycle to it's discharge cycle, so to synchronize the chip to the transducer we need to generate pulses at the.peaks. of the sine wave signal. That's what the top path does. Referring to the signal images in the circuit, the sine wave is presented to both inputs of an LM339 comparator (typo'ed as LM324) with one input delayed by an RC constant. Since the negative input is delayed, a rising signal will result in a positive output, and a falling signal becomes a negative output. The result is a square wave which is 90 degrees off from the original signal.
The square wave is presented to both inputs of an XOR gate, and once again one side is delayed by an RC constant. This results in a series of pulses at each transition of the square wave - at twice the original frequency.which is what the SG2535 wants to see for synchronization. (If I have interpreted the datasheet correctly. There's.very. little information available about this chip, and as far as I can tell no example circuits on the net use the synchronization feature. And if they did, they would be slaving one SG chip to another, without noting what signal that is.) PWM control The power and synchronization are presented to a UC3525 PWM management chip, which controls the switcher (first image) via PWM-A and PWM-B. The UC3525 has an onboard 5.1 volt reference, which runs through a digital potentiometer controlled by the microcontroller.
The voltage chosen by the micro is compared to the current signal from the transducer, and used to adjust the PWM width. As the transducer draws more current, the voltage goes up and the PWM controller reduces the pulse width to compensate. Negative feedback keeps the system fixed at a power level calculated by the micro, and the sync input keeps the frequency locked to the transducer/system resonant frequency. From the point of view of the micro, it's 'set and forget'.
Labels 'UC-xxx' represent connections to or from the microcontroller. For example, the micro can turn the output on or off using the SD ('shutdown') input to the switcher. Possible issues My biggest issue ATM is finding vendors and specs for SMPS power transformers, as found in computer power supplies. So far as I can tell, no standard vendor sells them (DigiKey, Farnell, Mouser, Coilcraft, et al).
Lots and lots of sellers on AliBaba, but no one has specs. I'd.like.
to say 'pull two transformers from old computer PSUs', because that would be an easy source for the hobbyist, but I suspect there's a lot of variation and being able to tell which ones are good to use is not a casual skill. I'd.also. like to point to a list of component vendors, in case the hobbyist just wants to buy the parts and put it together, and maybe sell a parts kit or something. That's hard without a specific vendor and proper specs. If anyone knows where to get SMPS transformers cheaply (meaning: not $50 each from a specialty brand) please let me know. If anyone sees a flaw in the logic, also please let me know.
at 22:10. Summary 1) The ultrasonic transducer power supply boards found on eBay are, um. Unsuited for hacker use. 2) Despite being careful, I managed to burn one out.
3) Apparently, no one else has been able to get these to work, either. 4) I'm a total coward when it comes to high-voltage measurements. Hackaday Fail For, I had originally planned to build and describe two types of ultrasonic experiment kits: a 'simple' unit based on an eBay power supply board with a timed relay, which would be simple to purchase and assemble, and a 'designed' supply with adjustable power and microprocessor control.
I've since played around with the ultrasonic power supply board that came with my transducer, and have concluded that these are pretty-well useless for hacker purposes. Additionally, I managed to burn one out despite being careful. My explanation of why these boards burn out so easily is below, after some background info about tuned circuits. (NB: Apologies for the large images - the system doesn't save the image size properly. It looks good while editing, but after posting the images go back to 'full size.'
) Powering a resonant circuit As mentioned in, an ultrasonic transducer is effectively a series resonant LC circuit: the piezo plate electrodes form a capacitor, and the resonating mass acts as an inductance. Since the transducer is an LC circuit, it presents different impedances to the driving circuit at different frequencies.
At its resonant frequency (28 KHz), it will appear to be a 25 ohm load, and when driven off-resonance, it will look like 1000. And driving the device at an intermediate frequency will result in an impedance omewhere between the extremes. (The high peaks in the plot are the parallel resonant modes, which should be avoided. Most of the off-resonance areas are about 1000 ohms.) The eBay transducers are rated at 100 watts, so the next question is: 'What level of drive voltage is needed to push 100 watts through the device?' Power is voltage squared divided by the resistance, which in this case is the impedance to the AC driving voltage, so the needed voltage depends on the driving frequency: Tuned horns and cleaning baths Most ultrasonic applications use a metal horn attached to the transducer to focus the energy into a small area, depending on the application.
The horn vibrates at its own resonant frequency, so the resonant frequency of the complete system (transducer+horn) is a melding of the two. Typically, one makes the horn extra long and 'trims' it to match the transducer resonance. An ultrasonic cleaner connects the transducer directly to a metal bath chamber where the ultrasonic energy gets bounced around a lot. 1) The chamber is square(ish), with rounded corners 2) You don't know ahead of time how much liquid is in the chamber 3) You don't know the density of the liquid (it might not be pure water) 4) You don't know what or how many things are in the water to be cleaned.
Because of this, the cleaner bath will never be in sharp resonance as one would get with a tuned horn. The ultrasonic cleaning system should present a high impedance to the driving circuit in all cases. The eBay ultrasonic transducer driver explained Here's the full schematic of the eBay driver board.
The 120 volt input is rectified (poorly) into 160 volts, then split into a balanced +/- 80 volts by C3/C4. One end of the T1 primary is held to the common midpoint, while Q1 and Q2 alternately switch the other end high (+80 volts) and low (-80 volts). The secondary of T1 amplifies this voltage, while T2 acts as a rude filter for the output waveform.
Note that T2 is only used as an inductor - the primary is shorted and grounded to keep it from generating any voltage. The transducer oscillations are picked up by L1-1 and delivered to Q1 and Q2 via L1-3 and L1-2.
As Q1 powers up the transducer, feedback from L1 will eventually turn it off and Q2 on to power the transducer in the other direction. As Q2 powers up the transducer, feedback from L1 eventually turns.it. off and Q1 turns on again. The output voltage at T1 is about 4x the input voltage from the rectifier/splitter (as gingerly measured using a variac). At full AC voltage, 80 volts becomes 320 volts at the output, which is about right for an off-resonance system. I believe this is a variation of a.
The system will find and keep the resonant frequency of the 'transducer plus system', whatever that may be. Problems with the eBay circuit 1) It burns out easily The biggest issue with the eBay circuit is that it has a tendency to burn out. Referring to the calculations above, the circuit generates voltage appropriate for a fairly high impedance. A bare transducer (nothing attached) will present as a highly tuned circuit with low impedance, drawing some 6x more current than the transistors expect. The transistors burn out within a few seconds (like, three seconds). (As an aside, this is why ultrasonic cleaner manuals warn about running with little or no fluid. For instance, the has the ominous: 'Do not allow the solution to drop more than 3/8 inch below the operating level line with heat or ultrasonics on.
Failure to comply may cause transducer and/or heater damage and will void your warranty.' ) 2) The generated waveform is crappy The output waveform is nowhere near a sine wave.
Looking at the circuit, note that the AC is rectified, but not smoothed. With no filter capacitors on the supply, the system is switching bouncy AC at 29 KHz through a high-frequency SMPS transformer. This might be OK for ultrasonic cleaning as it only makes the rubble bounce around more, but it's not good for the home lab. 3) There's no good way to adjust the power You could probably run the board from a variac while simultaneously measuring the current, but that's a lot of effort. Additionally, if the system goes out of tune for whatever reason (such as the transducer heating up) the power will drop, and if you adjust the power and the system comes.back. into tune you risk burning out your board.
It's a lot of trouble to go to, and you have to keep watching it. Also, the variac doesn't have much resolution at 1/6 full scale, and it's not clear that the feedback circuit would even work at that low voltage. 4) The circuit is nigh impossible to measure A scope probe pretty-much anywhere will change the circuit behavior in bad ways. Parting thoughts As near as I can tell, no one has posted a YouTube video demonstrating a home-built ultrasonic cleaner. (There are some posts that use motors and orbital sanders, but none that are both home-built and actually ultrasonic.) Additionally, suggests that.no one. has successfully home-built an ultrasonic cleaner. Is the only real home-built ultrasonic cleaner I could find, and he's using a $200 professional board (not the eBay board).and.
he burned one out in the process. I realize that used cleaners start at around $50 on eBay, but still - affordable 100 watt ultrasonic transducers would seem to have good hacker potential. I'm surprised no one else is using them for projects. I'm currently designing a power supply based on the PWM controller. These have a sync input which can be used to slave the device to an external clock. I think the transducer feedback can be used as this input, which would make the system self-resonant. at 02:49.
I'm a bit further along in the project than the build logs might suggest, and am stalled while I sort out a few issues. Here's what's going on ATM.
Handbook Of Commercial Catalysts
(Give feedback if you don't like these 'Peyton Place' type of status updates.) Transducer resonance isn't acting as expected I for Arduino hardware to automatically sweep through frequencies and determine the transducer resonance point, and this seems to work as expected. When I cut/paste data into LibreOffice and plot the results, there's an unaccountable spike in the data right at the resonance point. This is reproducible and not a bug in the program so far as I can tell, and it needs to be addressed in order to get accurate transducer measurements.
I made a list of possible explanations, and am in the process of testing and eliminating each. 1) A bug in the transducer program 2) Arduino hardware not powerful enough or otherwise not suitable for excitation 3) Poorly chosen component values for the interface circuit 4) An artifact of using square waves instead of sine waves to energize the transducer 5) Defective transducer/artifact of the transducer 6) Some other explanation (NB: The Y-axis scale is in AtoD counts, which is upside down from the normal impedance plot. Maximum AtoD voltage is minimum impedance.) Horn is much longer than needed I used the speed of sound in aluminum to calculate the proper horn length (1/2 wavelength), and then cast and turned down a step horn. 'Turns out, there's two speeds of sound in Aluminum, and I used the wrong one (.sigh.). The 6400 m/s value is the speed of sound in bulk material, but it's 5100 m/s in a cylinder.
I have no idea why the speeds would be different for different geometries, but there are definitely two values cited on the 'net depending on which source you use. Looking at as a comparison check indicates that my horn 25% too long.
Not a big issue, it only means I have to face off the horn to bring it closer to the required length. I should also shorten the casting form. Attaching horn to transducer has no effect I wrote a program for the PC which triggers the frequency sweep and pops up a chart (like the one shown above) so I don't have to keep cutting/pasting data into LibreOffice to see the results.
This means I can take my laptop to and shorten the horn using their lathe, then quickly see what this does to the resonant frequency. Hit uparrow/enter and it automatically triggers the sweep. (I'll put this program up on GitHub along with everything else.).and come to find that shortening the horn has no effect on the system resonance. Possible explanations: 1) Horn face is not flat, not making good contact with transducer 2) Problem with interface/electronics/program (see above) 3) Defective transducer 4) Other explanation I Need a better way to mount the horn in the lathe Learning to use the lathe has been a journey of discovery. I can hold the horn by either end in the chuck to face off a section (for tuning), but in doing so there's nothing holding the faced end. I can't use a tailstock center because it gets in the way of the facing operation.
I can't mount the horn further into the headstock because it's too big for the hole in the middle. The steady rest badly(!) chews up the surface. Also, the lathe 3-jaw chuck bites into the end of the horn. This is not an issue for the horn, but it'd be nice to be able to make professional-looking turned items. So far I've been getting by on guts and liquor, but I really need a better solution. Possible solutions include: 1) Cut out wooden vice jaws and clamp the horn in the/use the Bridgeport mill for facing with a fly cutter.
2) Make/get a steady rest that uses bearings instead of brass fingers 3) Hold the horn by the small end in my hexagonal collet form 4) Find a bigger lathe The image below illustrates the problem using the 1:1 step horn, which doesn't have a skinny end. For the step horn I have to clamp the skinny end in the chuck and face the fat end hanging out in empty space. The horn doesn't fit any further into the chuck. Power supply from eBay is all busted up The power supply I ordered from eBay is a bit.
Pretty much all of the front panel controls are busted in some way or another: the power switch is broken permanently in the 'on' position, two of the latching PB switches are jammed or broken, and the digital display doesn't light up. The connectors in the back are rusted, and the outsides are covered with a fine white powder, which I'm privately hoping doesn't turn out to be poisonous or carcinogenic. The insides show signs of severe rusting, as if the unit has been outside for several months.
The good news is that despite all this, the system seems to work. It fires right up and generates a perfect sine wave. With the power control set to minimum the output sits at 200 volts. at 20:22.
TL;DR I purchased and reverse engineered a cheap eBay ultrasonic power supply, to see if it held any value for the hobbyist. This first post explains the process of reverse engineering the (or any) board. A subsequent post will discuss the specifics of this board.
NB: Can anyone tell me what R4 (1 ohm, 5 watt) does in the schematic below? How to reverse engineer a simple PCB Dave Jones posted a (from his ) showing how to reverse engineer a PCB. He prints and overlays transparencies of the board top and bottom, so that he can visually align the traces with the components. I did essentially the same thing, but within a paint program - eliminating the need for physical copies. This has some advantages over his method (zoom, annotation, and contrast adjustment), but some disadvantages as well (small visual aperture). Step 1: Take a picture of the top and bottom of the PCB Step 2 Flip and flood Flip the trace image left-for-right, and flood-fill the copper traces with a high-contrast color.
Use the pen/brush tool to touch up areas that didn't fill properly (ie - the shiny, reflective bit in the image above). Step 3: Make a sandwich image Compose a 3-layer image with the components image on top, the traces in the middle, and a white bottom layer. Set the bottom (white) layer opacity to 100%, and adjust the opacity of the trace and component layers to give a nice X-ray view of the board. Sean rowe the salesman and the shark. (This will be specific to your eye sensitivity and the characteristics of your display, so adjust to taste. For my setup, the best settings seem to be White: 100%, Trace 100%, Components: 78%.) Rotate and adjust the trace layer so that the holes in the trace layer line up with the components. Step 4: Zoom and annotate The image can be zoomed and annotated as needed. Also, sections and components can be erased once deciphered.
(I found this particularly useful - certain sections are 'distracting', and blocking them helps me concentrate on other sections.) The results: a shiny, new annotated schematic, ready for the surgeon's table: A high-resolution version of this (pdf and svg) will be available on GitHub presently, as well as the KiCad schematic. Discussion of this specific circuit will be in a subsequent log. at 00:49. Improving the Bosch-Haber process is a challenging problem, so before I embark on any particular action it's probably a good idea to see if there's any chance of succeeding.
As the saying goes, four hours in the lab will save you an hour in the library. NB: I am not actually a chem major, so if you see an error in the analysis, please let me know! Where to find information Several researchers have looked into ultrasonic nitrogen fixation. For the technical reader, by Supeno is a good starting point. The paper reviews the previous research and explains the various processes, including cavitation, chemical reactions, solubility, kinematics, and so on. If you want more information on the problem I'm trying to solve, that's a good place to start. For a good overview of the ways nitrogen may be fixed, try by Frank Ernst.
Published in 1928, it gives a little of the history of nitrate usage, and explains in detail the various methods of producing it. Chapter 1 (history) has an interesting take on WWI: It is quite generally believed that Germany declared war in 1914 only after assuring herself that she had a suitable source of fixed nitrogen within her own borders. The rate of consumption of nitrogen in explosives during this war was undoubtedly far beyond the expectations of any individual or nation. In order to meet this demand it was necessary, even with the enormous expansion of the rather young atmospheric nitrogen fixation industry, to stint agriculture. How great an effect this had on the eventual result is rather difficult to appraise, but there Is no doubt that the people of several of the warring nations suffered materially and still show the effects of malnutrition. If you just want the basics of the Bosch-Haber process, is pretty good. For more detail on why ammonia fixation plants are so expensive, check out by Howard F.
It's an Ammonia fixation plant case study, and has all the gory details. Not for the faint of heart, guaranteed to make your head spin. Energy required for Bosch-Haber According to, Nitrogen from the Bosch-Haber process requires 34.5 Gigajoules per metric ton (mt) of nitrogen produced.
I can't tell if that's nitrogen produced or ammonia produced, but it doesn't matter because they weigh about the same and this calculation is only approximate. So Bosch-Haber requires over half a million joules to create one mole of ammonia. To put this in perspective, 1 mole of ammonia weighs 17 grams, and that many joules will run a 100 watt incandescent bulb for over 90 minutes. And this for a chemical reaction that gives off energy in the process.
Quite a lot of it, actually: To put that in perspective, this is about you would get from burning the same mass of wood. The reason the reaction doesn't easily happen - the reason we can't simply ignite the gases like so much paper - has to do with the interplay of the activation energy (breaking the N2 apart) and the entropy. When you heat the gases enough to start the reaction, the reaction is no longer favored and the reverse reaction happens instead.
Ammonia breaks down into nitrogen. This is actually a good thing, otherwise a lightning strike would ignite the atmosphere, oxidizing all the nitrogen and turning rain into nitric acid. I'll post a more complete explanation in a future log. For now, the target to beat appears to be about half a million joules per mole.
Howard F. Rase
Energy required for sonication According to Supeno paper, the maximum rate of ammonia produced was 4 nmol/min/W. Converting to Joules and moles: Target for this project Comparing the Bosch and sonification energies: So for purposes of this project, I need to improve the efficiency of sonification by a factor of about 25,000. This isn't quite as bad as it looks. For one thing, I think I can get a factor of 10 (and maybe as much as 100) using a highly tuned transducer horn.
It wasn't clear from Supeno's paper, but from his description it looks like he's using a water bath, similar to an ultrasonic cleaner, and he makes no mention of tuning the chamber or transducer. Even if he's running the system at resonance, he may not be running the transducer at resonance, and this will reduce his efficiency. There's also an interesting quote from his abstract: The decrease in the rate with bulk temperature suggests that kinetics, rather than thermodynamics, is the limiting condition for sonochemical synthesis of ammonia. There seems to be no chemical or physical reason why sonification can't work, and the comment above seems to indicate that changes in the experimental setup (geometry, reaction profile, and such) might affect the efficiency.
I'm quite looking forward to trying. at 04:35. TL;DR A few passive components and an Arduino can measure the resonant frequency of a transducer in an automated fashion. This will come in handy when tuning the horn. The circuit schematic is at the bottom of this post, and the program will be available on GitHub presently. Feel free to skip the gory details.
NB: As an experiment I am posting the circuit design in the style of an academic exercise in great gory detail, and I'm looking for feedback on presentation and style. Please help me out.
If you think this is tedious and wasteful and too simplistic or something let me know and I'll adjust the style in future logs. Measuring resonant frequency, the easier way If you don't have a sweep frequency generator and/or a scope and frequency counter you can use an Arduino to measure the transducer resonant frequency. We'll need to do the measurement several times to tune the horn, so it makes sense to have a way to do this with as little effort as possible. The block diagram circuit looks like this: But before we hook everything up, it's a good idea to see if this is likely to work. Design question 1: Can the Arduino source enough current? According to the Atmel 328P (table 28.1: Absolute Maximum Ratings) the maximum DC current per I/O pin is 40 mA. Assuming a worst case scenario when the transducer shows zero impedance, a 5V output will push 50 mA through the 100Ω resistor, and that's too much for the micro to handle.
However, the high-level output of the micro is less than 5 volts. According to the datasheet (Table 28-1. Common DC characteristics), the minimum high-level output is 4.2 volts with no 'typical' or 'max' values specified. Actually measuring the Arduino shows the output as 4.2 volts, so the measurement circuit will draw only 42mA. And since a square wave is only high for 50% of the time the effective current is cut in half, so the DC current is actually 21 mA. This is well within the rated 40 mA, so it looks like the Arduino can supply the necessary current.
Design question 2: Can the Arduino generate a fast enough frequency? The fastest clock prescaler in the Arduino is 1-to-1 with the CPU speed, which is also the crystal speed, which is 16 MHz. The resonant frequency of the transducer is nominally 28 ±1 kHz, so supposing we want to sweep between 24 and 32 kHz, the number of ticks per squarewave cycle is: Each square wave cycle has two parts: one counter cycle of high output, followed by one counter cycle of low output, so the actual counter values to generate the square waves are: This seems reasonable.
We can set timer 1 to one of these values or anything in between, set the OCR1A output to 'toggle on counter reset', and the system will automatically generate a squarewave output. Design question 3: Does the Arduino have enough frequency resolution? Looking at the fastest frequency (250 counts, 32 kHz), we note that the next lower frequency will be 251 counts which generates 31.872 Hz, for a difference of 127.5. Looking at the slowest frequency (333 counts, 24024 Hz) the next higher frequency will be 332 counts which generates 24096 Hz for a difference of 72 Hz.
So we can expect the Arduino to test and measure frequencies in steps of about 100 Hz. This isn't great resolution, but it's comparable to what you can get using an analog signal generator and a steady hand. There's a way to get much better resolution by doing extra processing in the micro, but I'll leave that for a later post.
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For now this should suit our needs. Designing the rectifier/integrator The transducer will turn the square wave into a sine wave which goes both above and below the ground plane. We need to block the negative half and convert from AC to DC before connecting to the analog input. (Any input of the Arduino will be damaged by a negative voltage, and the AtoD only measures DC.) So, something like this: Design question 4: What values of R and C should be used?
Now we need to choose values for R and C. Looking at the frequency/count table above, a full frequency sweep will test 250 through 333 counts inclusive, or 84 tests total.
For each test, if we generate the frequency for 0.1 seconds and then measure the AtoD, a full frequency sweep will take about 9 seconds, which seems reasonable. So we need the integrator to settle down to its final voltage within 0.1 seconds, which means that the time constant has to be short relative to that value. Perhaps 1/10 of that, so T = RC = 0.01 seconds. So reasonable values might be 0.1 uF for C and 100K for R. Design question 5: Will ripple be a problem?
Converting AC to DC leads to voltage ripple in the output waveform. The capacitor will charge in response to an AC pulse, then discharge when the pulse goes away. The end result is a slightly varying DC voltage, and the AtoD will see different values at different times. We need to see if this will be a problem. We can estimate the ripple by thinking of the capacitor discharging through the resistor after the voltage passes the AC peak. Starting with 'Ohms Law' for capacitors: We can rearrange this as: (T, being time, should be lower case here, but I can't seem to convince the HAD Latex editor to do that. Please bear with it.) The dt term is the time between pulses, which is 1/frequency.
The worst case in our frequency sweep is 24 kHz, for which the pulses arrive in 42 uS intervals (longest time between pulses, resulting in the longest decay time). The current term 'I' is the current taken away from the capacitor by the resistor, which is V (at the peak) divided by R. Substituting, we get: We noted previously that the maximum voltage is about 4.2 volts, minus the voltage drop of the diode (0.7 volts), so the worst cast voltage peak should be about 3.5 volts. And we supposed previously that our time constant T = RC is about 0.01 seconds, so plugging everything in we get: Since our peak voltage is 3.5 volts, that's a ripple voltage of 1 part in 238, or about 0.5%.
The Arduino AtoD input has 10 bits of precision, and so can measure as little as 1 part in 1024. The ripple voltage should be within the lowest 2 bits of the AtoD converter. In reality the peak voltage will be less than 3.5 volts since the transducer will never have zero impedance, and this will make the ripple voltage a bit less than calculated. Also, we approximated the ripple by assuming that the capacitor would discharge over the full time period. In reality, the capacitor only discharges to the point where the next pulse arrives, as shown here: We also played fast and loose with the differential in the equation above by breaking it into two pieces. In reality the capacitor discharges exponentially (not linearly, as shown), but this works out in our favor because beyond the first moment of discharge the capacitor discharges more slowly than calculated. The final circuit: So the final circuit looks something like this: I checked the output using a scope, and found not a hint of ripple.
More importantly, the output doesn't look like it will damage the Arduino. A little bit of perfboard, and here's the final result.