Grantville Gazette 38 gg-38

by Коллектив Авторов

  Temperature has several different effects. Higher temperatures shift the equilibrium point in favor of the reverse reaction, but the reaction is forced forward by continuously removing hydrogen and supplying fresh steam (Greenwood 275). The permeability of the iron to steam and hydrogen is reduced by fritting above 900oC. However, the reaction is very slow below 650oC. (Teel 88).

  In the Lane multi-retort system, dry steam is used at a pressure of 60-80 psi without any superheat; the exothermicity of the reaction raises the reaction temperature adequately. In a single retort system, the same pressure is used with partial superheat. (Taylor 51).

  Ideally, the "contact mass" of iron is porous (to maximize reactive surface area) yet robust (so it doesn't crumble into dust and create a back-pressure). Also, it is resistant to local overheating, which results in sintering. The choice of iron (spathic ore is best) makes a difference; "before 1917, American producers . . . imported their contact material, mainly from England." (29). Spongy iron-manganese ores will prove to work better than ordinary iron ore. (Ellis 495, 502). It may be possible to catalyze the reaction with copper, lead, vanadium or aluminum. (Ellis 502).

  As iron oxide is formed, it shields the remaining iron from the steam. (Teel 87). Hence, for large-scale economical operation, the iron (which was oxidized to iron oxide) is regenerated. (Ellis 485). That means that you may start with iron ore (Fe2O3) instead of iron. About six tons iron ore are needed to produce 3500 cubic feet/hour. (Teel 88). The iron oxide is reduced (probably with water gas), and then you introduce the steam to react with the iron and produce the hydrogen. Then you repeat the cycle. Typically, consumption of water gas is 2.5 cubic feet per cubic feet hydrogen in a multi-retort plant and 3.5 in a single retort one. (Teed 97).

  The water gas, in turn, is produced by the steam-coal process discussed earlier. Soft coke consumption is at a rate of about one ton for every 6500-7000 cubic feet hydrogen. (98).

  However, the water gas must be purified or the impurities will result in formation of adverse deposits on the contact material or gaseous contaminants (hydrogen sulfide, carbon dioxide, etc.) in the hydrogen. (Ellis 487ff; Roth 25). There is also sulfur in the iron ore (Teel 93), and sulfur compounds are especially problematic. (Greenwood 181). Measures taken to cope with these problems increase the volume of water gas required and also reduce the production rate. (Ellis 487). Even then, the iron eventually loses its activity. (Ellis 499). "An unsuccessful attempt at commercial production . . . was made by Giffard in 1878. The iron rapidly became inactive due to sintering of the material and to chemical reaction with impurities in the reducing gases used." (Taylor 27).

  Even in modern embodiments, the initial product contains a large fraction (61%) of steam; that can be condensed out. There will also be carbon monoxide (from the water gas) and nitrogen (presumably from dissolved air in the water used to make the steam). (Brewer 232). These are purified out.

  The most common factory implementation of the regenerative steam-iron process is the Lane process; it's relatively economical of fuel but there's more deposition of carbon and (thanks to side-reaction with steam) higher carbon monoxide content. A plant producing 3500 cubic feet/hour might have 36 vertical retorts, each 9 inches diameter and 10 feet high. (Greenwood 178). Despite the recommendations of 2002McGHEST, the typical retort temperature was 650oC, prolonging the useful life of the retorts. They last 12-18 months, and the ore is good for 6. Water gas is consumed at rate of 2-3 volumes per volume hydrogen, and the cost of hydrogen is 3/- to 4/- per 1000 cubic feet, excluding overhead. (182).

  High Pressure Water ("Bergius"). The temperatures are lower (200-300oC) but high pressure is used (150 atmospheres) to keep the water liquid as it reacts with iron (Ellis 513) or carbon (Ellis 527ff). Common salt, iron chloride or hydrochloric acid accelerate the former and thallium salts catalyze the latter. Bergius built a prototype that produced high (99.95%) purity hydrogen. Since the hydrogen is already pressurized it can be put into bottles without the need for a separate compressor. (Teel 64). While initial cost and floor space requirements were expected to be low (Greenwood 188ff)-a 10 gallon capacity generator supposedly can produce 1000 cubic feet/hour (Teel 65)-I don't think these reactions were ever practiced commercially. Bergius (1913) claimed that hydrogen could be produced for just 2 cents/cubic meter (Greenwood says 1s/4.5p to 1s/11p per 1000 cubic feet.)

  Electrolysis of Water. Water was first electrolyzed into hydrogen and oxygen in 1800. (Cleveland 128). Hydrogen is produced at the cathode and oxygen at the anode:

  Cathode (reduction): 2 H2O + 2e- -› H2 + 2OH-

  Anode (oxidation): 2 H2O -›O2 + 4 H+ + 4e-

  The net reaction is

  2H2O (36 grams) + electricity -› 2H2 (4 grams) + O2 (32 grams) .

  The reaction requires an electrolyte, so either base (such as potassium or sodium hydroxide) or acid (such as sulfuric acid) is added to the water.

  We will want an electrode material that is resistant to attack by the electrolyte, and minimizes the internal resistance. (Ellis 536; Greenwood 195). Acid electrolytes caused continuing corrosion problems and hence alkaline electrolytes became the norm. (Taylor 106). Taylor (105) recommends the combination of a nickel-plated anode and an iron cathode to minimize overvoltage.

  The level of oxygen in the hydrogen compartments shouldn't exceed 5.3%, and of hydrogen in the oxygen ones, 5.5%. (Greenwood 202). It's critically important that the cell be designed to prevent the mixing of the hydrogen produced at the cathode with the oxygen produced at the anode, which can result in an explosion. This is usually done with a diaphragm separating the two, although there are alternatives. (Ellis 561, 581; Greenwood 201). Likewise, the produced gases should be monitored to detect inadvertent mixing. (This can occur, for example, if the polarity is reversed-Ellis 585, or by injury to the diaphragm, blockage in the system, or too great current density-Greenwood 202.) . This can be done by sampling the gas and igniting the sample under controlled conditions; they should burn not detonate. (Taylor 73).

  From a portability standard, decomposing water with electricity has the advantage that you don't need to transport reactants. As to the weight of the apparatus itself, a Schukert 600 amp electrolyzer holding 50 liters solution and producing 5 m3/24h weighed 220 kg (Englehardt 86). A 110V, 150 amp, 16.5 kw Schmidt system producing 66 m3/24 h weighed 14,000 kg, while a 1.65 kw plant producing one-tenth that weighed 700 kg. (33). Unfortunately, because access to electricity is required, this is not really a method suitable for launch site production. (Batteries are heavy.)

  I have gotten mixed signals on the issue of the space requirements for electrolysis. Ells first says that it requires a "relatively large floor space." (570) and then that "for small plants electrolysis has much in its favor." (595; cp. Teel 132). It may depend on the design; Schuckert demands relatively more room (Greenwood 198) while Schmidt is compact (199). Still, there was a portable Schukert generator car weighing in at 2000 kg, used together with a scrubber car of 1700-2100 kg. (Ardery).

  The only apparatus for which I have specifics is the Levin generator; 100 will occupy 31 feet by 4.5 feet, and produce 320 cubic feet/hour at 200 amperes. (580). With normal room height, they can be installed in two tiers.

  But an electrolytic cell can be very small. With 12.2 watts of solar-based electricity, a modern homemade cell in a 3.5"x5.5"x1.5" plastic container produced 0.399 milliliters/second hydrogen. (Businelli). So the real question is, what is the required cell volume to achieve the desired production rate?

  One nice thing about electrochemistry is that you can predict performance. A chemist would expect that 96,500 coulombs (ampere-seconds) of electricity would liberate 1 gram of hydrogen and 8 grams of oxygen, those being the "equivalent weights" (ionic weight/ionic charge). So one ampere-hour produces 0.03731 gram-equivalents, which works out as 0.01482 cubic feet of hydrogen at STP (0oC, 760 mm Hg), 0.00741 cubic feet oxygen. At 20oC we do better; 0.01585 of hydrogen and 0.00792 of oxygen. (Taylor 103). The current supplied is typically 200-6
00 amperes. So, if the current were 400 amps, production would be 5.93 cubic feet hydrogen and 2.96 cubic feet oxygen per hour. (Ellis 536).

  Teed (39) considered electrolysis to be suitable only for production of up to 1000 cubic feet hydrogen/hour.

  In theory, the required voltage is 1.23, but because of secondary effects (overvoltage) it will probably be found that 1.7 volts are needed for continuous decomposition of water. (Taylor 104; Ellis 536). However, the diaphragm will tend to increase the resistance of the cell, necessitating a voltage of 2-4 volts. (106). As a result, energy efficiencies are in the 50-60% range. (Engelhardt 18, 20, 31).

  The first electrolytic oxygen generator constructed for laboratory purposes was that of D'Arsonval (1885), and the first large scale apparatus was that of Latchinoff (1888). (Taylor 108). The first with significant industrial adoption was probably Schmidt's (1899), which produced 99% pure hydrogen and 97% pure oxygen. (Engelhardt 31).

  2002McGHEST says that "although comparatively expensive, the process generates hydrogen of very high purity (over 99.9%). However, I think it's a mistake to count out the electrolytic process. Water, of course, is cheap, so the main expenses are those of providing electricity, and separating out the oxygen.

  1890-1910 prices for electricity ran around 0.25 cents/kwh for hydroelectric and 1.25 for coal-fired steam plants. (Engelhardt 17). (Ellis 538 assumes 1 cent/kwh, and 569 quotes prices of 3-4 cents in New York City and 0.5 cents in South Chicago.)

  Chances are that the recovered oxygen can be sold, thus defraying at least some of the production costs. In fact, the zeppelin hydrogen produced in 1934-38 was a byproduct of the electrolytic production of oxygen. (Dick 193). in 1904, oxygen sold for $1/m3 and hydrogen for $0.3125. (Engelhardt 40).

  Bear in mind that "a normal military balloon requires, in order to be filled in twenty-four hours, a plant of about 200 kilowatts." An airship requires a lot more hydrogen than that.

  Still, in 1904, the Italian, French and Swiss armies all relied on electrolytic hydrogen. (123).

  In 2004, the average cost of electricity in America was 5 cents/kwh and at that price, with 80% electrolysis efficiency and 90% compression efficiency, the power cost for compressed electrolytic hydrogen was $2.70/kg. (Doty).

  The higher the temperature, the less electrical energy is needed. If heat is cheaper than electricity, then higher operating temperatures are desirable. (Kirk-Othmer 13:868).

  Electrolysis of Alkali. Historically, the first electrolytic hydrogen was a byproduct of the processing of brine to yield sodium hydroxide (caustic soda):

  2Na+ + 2Cl- + 2H2O -› 2NaOH + H2 + Cl2

  With 100% current efficiency, each ampere-hour would produce 1.322 grams of chlorine, 1.491 grams of sodium hydroxide and 0.0373 grams of hydrogen." (Actual current efficiencies were 90-98%.) The caustic soda may be used to make soap, and the chlorine bleach, and of course there are other uses, too. (Taylor 120). At 15oC, each ton of salt electrolyzed produces 72320 cubic feet hydrogen. Hydrogen purity is 90-97%. (Greenwood 203). Naturally, you want to prevent intermixing of hydrogen and chlorine after production.

  In 1904, this was the method used to produce hydrogen for German army balloons. (Englehardt 123).

  Water Thermolysis. The thermal decomposition of water requires temperatures in excess of 2000oK, and of course reactor materials that can tolerate the temperature. (Yurum 24).

  Splitting Hydrogen Sulfide. The use of hydrogen sulfide as a source of hydrogen has been proposed, but not commercialized. One possibility is to react it with iodine, producing sulfur and hydrogen iodide, and then decompose the latter. Another is to react it with methane, forming hydrogen and carbon disulfide. (Kirk-Othmer 13: 874). These methods probably do not appear in Grantville literature.

  Thermal Decomposition of Hydrocarbons. When exposed to sufficient heat (1200-1300oC for methane, 500oC for acetylene), hydrocarbons dissociate into their component elements. (Ellis 471).

  The Rincker-Wolter system is of some interest because they started with oils and tars, and the demand for tar in163x is limited. The required temperature was 1200oC for the hydrogen to be of acceptable purity. In 1912, a plant producing 3500 cubic feet/hour would cost $2575 plus "erecting expenses," and with the oil at 4 cents/gallon, the hydrogen cost would be $1.75/1000 cubic feet. (Ellis 473ff). A semiportable plant with such capacity has been successfully mounted on two railway trucks. Greenwood 193 reports a cost of 550 pounds sterling for the plant and 2s/6p to 4s/0p per 1000 cubic feet.

  A variation on this is the Carbonium process; acetylene gas is compressed to two atmospheres and exploded by an electric spark, yielding carbon (deposited as lamp-black) and high purity hydrogen. You need an explosion chamber, and the lamp black is scraped off the walls. If there's a market for the lamp black (one kg per cubic meter of hydrogen), this method can be advantageous. (Ellis 473). The good news about the process is that it was used to supply hydrogen for the zeppelins at Friedrichshafen. The bad news is that the factory was destroyed by an explosion in 1910! Before this slight mishap, the cost of production was 4 shillings per 1000 cubic feet. (Greenwood 192).

  Catalytic steam-hydrocarbon reforming. Per McGHEST2002, volatile hydrocarbons (from natural gas) are reacted with steam over a nickel catalyst at 700-1000oC, forming hydrogen and carbon monoxide, the latter being converted to carbon dioxide by reaction with water at 350oC over an iron oxide catalyst. If the hydrocarbon were methane (which has the highest hydrogen:carbon ratio), the first reaction would be

  CH4+H2O-›CO+3H2.

  The encyclopedia notes that carbon dioxide may be removed by scrubbing with aqueous monoethylamine. However, there's a much easier method; pass the gas mixture through water under high pressure; the carbon dioxide reacts with water to form carbonic acid and dissolves; the hydrogen doesn't dissolve and bubbles to the surface.

  Even with these hints, the method may take a while to get working. In the old time line, experiments began in 1912, but the first real success, with methane over a nickel catalyst, came in the 1920s. It wasn't commercialized until 1931. (Smil 113). Note that the reforming catalyst isn't necessarily the simple metal; the 1962 ICI process used nickel-potassium oxide-aluminum oxide (Weissermel 18).

  In the 1632 universe, the likeliest source of the volatile hydrocarbons would be coal gas, but natural gas would also be an option. However, we do have to find the right catalyst, and the feedstock may include substances (sulfur, chloride) that poison the catalyst.

  Immediately prior to the RoF this was the dominant method of producing hydrogen. the Kirk-Othmer Encyclopedia of Chemical Technology reports that it had a thermal efficiency of 78.5%, versus only 27.2% for water electrolysis, and a net hydrogen production cost of $7.19 (1985 dollars)/100 m3, versus $22.63 for electrolysis. (13:853). The theoretical energy consumption is 300 BTU/scf hydrogen, and a typical one is 320. If the natural gas price is $4/million BTU, feedstock and utility costs are 65% total operating costs. (Udengaard).

  Catalytic steam-methanol reforming. This is a related process:

  CH3OH-›CO+2H2.

  Steam reacts with the carbon monoxide to form carbon dioxide and more hydrogen. The process has been proposed for modern field use, with a one ton trailer-mounted generator producing 150 cubic feet/hour with fuel consumption of just over one gallon/hour. (Philpott).

  In the old time line, it had higher operating costs but lower fixed costs than the hydrocarbon-based scheme. (Blomen, 150). Other advantages are that methanol is free of sulfur and the reaction can be run at a lower temperature (300°C). (Liu 65). However, the problem is that experimentation will be needed to find appropriate catalysts (likely to be copper, zinc oxide or palladium-based).

  Decomposition of Ammonia. The first problem is producing the ammonia. Nowadays it's made by the Haber process from nitrogen and hydrogen, but obviously if our goal is hydrogen, we are taking a different route. There is ammonium carbonate in New World guano deposits, and ammonium sulfate is a potential byproduct of the manufacture of boric acid in
Tuscany. We also must determine the decomposition conditions. Ammonia can be decomposed by heat alone but a catalyst helps. (Lunge 580ff) Ammonia is another possible target for catalytic reforming. (Udengaard).

  Fermentation. The Weiszmann process for the manufacture of acetone and butyl alcohol by fermentation of starchy foods (maize, potatoes) also produces hydrogen and carbon dioxide in equal volumes; 5.5 cubic feet of mixed gas per pound of maize fermented. (Taylor 166). Both acetone and butyl alcohol are quite important industrial chemicals, and so the sale of hydrogen needs to only cover the cost of its separation from carbon dioxide. The real problem is isolating the necessary fermentation organism.

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  Disaster Scenarios. As the hydrogen is produced, it mixes with any air that is present, soon creating flammable or even explosive mixtures. Ideally, several volumes of an inert gas (carbon dioxide, nitrogen) or liquid (water) are run through the production chamber first, to drive out the air. Also watch out for leaks from the gas hoses.

  If the reagents are stored close together, and their containers are ruptured, an uncontrolled reaction can occur.

  Some of the reactions are exothermic, so even if the reaction is in the proper vessel, the temperature has to be monitored.

  Comparative Operating Costs

  I was able to find some comparative operating cost data on the different production processes. Some sources include labor and overhead (interest and depreciation on fixed costs), and others don't.

  Figure that one 1900 US dollar is 4.2 contemporaneous British shillings, or 0.5 1632 shillings if deflated based on Allen's laborers' wage rates, and 1.25 if using Allen's London CPI. (Two shillings is equivalent to one Dutch guilder. ) That same 1900 dollar is $19.57 in 2000 if inflated using the Sahr CPI.

  The NTL economy in 1635 is going to be very different than that of pre-RoF Europe, and also different from that of OTL early-twentieth century Europe. Hence, be cautious about putting a lot of faith on cost conversions. It's probably better to use the table to get a sense of relative rather than absolute costs, but even that's dangerous; individual inputs (e.g., electrical energy) could be cheaper or more expensive in the new universe, even different from one region to another.