successful in laboratory autoclaves and that economic evaluation is expected to be proved out in a 1 to 3 ton-per-day pilot plant now under construction at the Bureau of Mines' metallurgical re­search station near Albany, Ore. The pilot plant is expected to produce 3 bbl per day of a product resembling No. 6 fuel oil with a heating value of 13,000 to 14,000 Btu per lb.

The adaptation of coal conversion processes for waste disposal is also being pursued by Garrett Research & Development Co. Dr. James R. Lon-ganbach described for the petroleum division how Garrett is extending its pyrolysis technology to include a vari­ety of industrial and municipal wastes. Unlike the Bureau of Mines processes, the Garrett system operates at about ambient pressure. So far, coal and or­ganic wastes such as municipal refuse, tree bark, cow manure, grass, and straw have been treated successfully.

The organic material in the Garrett process is heated by contact with hot recycle char, made within the process, and is carried in a gas stream through a reactor where pyrolysis occurs with very short residence times (C&EN, Dec. 17, 1973, page 23). This method maximizes the volatile yield and mini-

Ï169th ACS NATIONAL MEETING

Antibacterial cotton fabric—useful for such items as hospital bed sheets, bandages, and perhaps even clothing —may be a reality within a few years, if research at the U.S. Department of Agriculture's Southern Regional Re­search Center in New Orleans pans out. The research, by chemist Tyrone L. Vigo and coworkers, is aimed at devel­oping methods for imparting durable bacterial resistance to cotton fabric. Whether there is a significant market for such products, however, is another matter, although their utility would seem desirable.

Existing antibacterial agents and treatments act after the fact, once bac­teria have invaded the fabric substrate. But "we want to prevent the bacteria from getting there in the first place," Dr. Vigo told the Cellulose, Paper, and Textile Division. The work is an out­growth of other research into perma­nent-press characteristics for cotton.

The concept is not entirely new, Vigo concedes. In Europe and the Soviet Union, work has been going on for sev­eral years. In the U.S., attempts have been made previously to develop a durable antibacterial finish, primarily for bandages and the like, but as yet a commercial product has failed to ma­terialize.

Now the USDA scientists in New Orleans have come up with two meth­ods that may be the first steps towards

mizes further cracking. Tars and gases are separated for further processing.

The emphasis in the solid waste py­rolysis process has been on liquid prod­ucts, since the gases are high in water and carbon dioxide. The pyrolytic liq­uids are intended primarily as fuels. Although the heat content per barrel of fuel is only two thirds that of residual fuel oil, feedstock is inexpensive and consumption of waste materials simul­taneously solves a disposal problem. The resulting oil is low in sulfur and nitrogen, and burns cleanly in large-scale combustion tests. Hydrogénation of the liquids from solid waste pyroly­sis is not contemplated by Garrett at present.

A typical product distribution from the Garrett organic waste pyrolysis process is 20% char, 40% pyrolytic oil, 12% water, and 28% gases. The pyroly­sis of municipal solid wastes is one of the objectives of a demonstration plant to be built in San Diego County, Cali­fornia. The plant will handle 200 tons per day of as-received materials and is expected to be completed in 1976. The joint project will cost $10 million and is being funded by Occidental Petrole­um Corp. (Garrett's parent firm) and San Diego County. D

producing cotton fabric that inhibits growth of bacteria. One of the methods is actually the intermediate step to the second, but both involve chemically reacting the cotton to achieve the de­sired results.

The first step is chlorination of the cotton fabric with phosphorus oxychlo-ride in dimethylformamide at 65 to 80° C. This yields a chlorine-substituted cotton of about 5% chlorine by weight that is antibacterial. But Vigo's group goes a step further. It reacts the chlori­nated fabric, in turn, with potassium thiocyanate in dimethylformamide to yield a cotton fabric that contains a thiocyanate group as part of the cellu­lose molecule. By using 20% by weight of potassium thiocyanate in the form-amide solvent at 150° C, more than 80% of the chlorine atoms in the chlo­rinated cotton are replaced with thio­cyanate groups.

Chemically reacting cotton fabric by these two routes doesn't dramatically change the physical characteristics of the material. This factor is important since antibacterial fabric for garment use would have to be processed just as conventional cotton fabric and have similar performance characteristics. Vigo hopes that antibacterial garments of this type may have an aesthetic ap­peal to consumers concerned about body odor. Resident skin bacteria, which such cotton would help fight, are the major cause of body odor. Gar­ments made from this material also may appeal to hygiene-conscious indi­viduals.

In addition, chemically reacting the cotton offers a method of producing durable antibacterial action, according to Vigo. After 10 wash cycles simulat­ing home laundering conditions, the reacted cotton from these experiments retained its antibacterial activity. Fab­ric samples were tested before and after laundering by the parallel streak method, a visual means of assessing bacterial infestation. Typical gram-positive (Staphylococcus aureus) and gram-negative (Escherichia coli) bacte­ria were used. Prior to laundering, the chlorine-substituted fabric had no un­dergrowth of bacteria, and the thiocy-anated fabric had very slight under­growth. After laundering, the reverse occprred. Untreated cotton subjected to the same test had extensive under­growth. Based on these results, says Vigo, both of the treated fabrics were rated as having moderate antibacterial activity.

USDA scientists also are taking a look at other· functional groups at­tached to cotton for bacteriostatic and bactericidal activity, particularly groups that work against a skin inhab­iting strain, Staphylococcus epider-mitis, that produces perspiration odor. Other improvements also will be need­ed. For one thing the 10-wash-cycle du­rability achieved thus far isn't particu­larly good by standards applied to other fabric treatments such as flame retardancy. For another, the chloro and cyanato cottons aren't particularly ac­tive against S. epidermitis, the odor-causing strain.

But some other, larger, questions re­main unanswered. For example, will an antibacterial fabric sell? Antibacterial hospital goods like bandages, dressings, operating room gowns, and the like, no doubt would be desirable. But this mar­ket is tiny compared with the garment industry. Also, will the consumer buy the aesthetic and hygienic aspects of such a material? It's hard to tell. At least one previous attempt at bringing sanitized clothing (although without a durable finish) to the market place was a flop, says a cotton industry technical consultant. And if the USDA work is to be economically successful, this is just the market it will have to penetrate, α

Prospects improve for gasifying coal in situ

t 169th ACS NATIONAL MEETING

After some changes of fortune in the recent past, the prospects for in situ gasification of coal may be stabilizing. It's too early to even predict eventual success for in situ gasification, but data currently being gathered by the Energy Research & Development Ad­ministration's Laramie, Wyo., energy research center are, at the very least,

USDA work aims at antibacterial cotton fabric

18 C&EN April 14, 1975

more consistent than they were as re­cently as 1973.

Dr. Charles F. Brandenburg of the research center believes that technolo­gy at hand ' is sufficient to produce a low-Btu gas from shallow (less than 1000 feet deep) deposits of bituminous, subbituminous, and lignitic coals. Re­cent experiments by the Bureau of Mines at Hanna, Wyo., he told the Di­vision of Fuel Chemistry in a sympo­sium on unusual fuels production, have been more favorable than previous ex­periments in at least two respects: A gas of higher-Btu content (125 Btu per scf) has been produced, and during more than six months of operation there was no leakage from the system.

Brandenburg notes that the impor­tant factors in building an under­ground reactor are the rate and pres­sure of water influx and the directional permeability of the coal seam. Ideally, strata above and below the coal seam must have permeabilities significantly lower than the seam itself.

The method used in the Hanna ex­periments was percolation or filtration. Success of this method depends on de­velopment of enough permeability be­tween vertical bore holes to maintain a sufficient flow of gasification agent and product gas. The most reliable method of linking vertical bore holes is reverse combustion. A fire is ignited in the bore hole to be vented and air is fed into this combustion zone by injection into an adjacent bore hole. The com­bustion front is thus propagated coun-tercurrent to the gas flow.

One practical advantage of this method is that the possibility that tars produced from carbonization will plug natural fractures in the coal is obviated because the tars are not driven into the coal ahead of the combustion zone. Also, directional control of combustion front movement is attained because the combustion front will proceed toward the source of air.

During establishment of linkage be­tween the bore holes, two distinct phases have been observed. Initially, air is injected at high pressures (250 to 300 psig) and low flow rates for several days. During this time the narrow combustion front proceeds toward the source of air. When breakthrough be­tween well bores occurs, an abrupt drop in pressure occurs, after which the flow of gas is unrestricted.

Gas produced during the linking pro­cess is usually of a higher Btu content (175 to 200 Btu per scf) with the high methane and low carbon monoxide contents typical of a carbonization pro­cess. Once breakthrough is achieved, gasification rather than carbonization becomes the dominant mode. Gasifica­tion is characterized by high carbon monoxide and low methane content of the product gases.

The total amount of coal affected during the trials at Hanna was 2986 tons, with 1171 tons being carbonized only and 1815 tons being totally gasi­

fied. These results are based on the linkage and gasification of three path­ways of 80, 90, and 100 feet radiating from the original ignition point to three different bore holes used as air injec­tion points. Assuming that a cylinder of coal 30 feet in diameter was accessi­ble to gasification for each pathway, about 4700 tons of coal were available for gasification.

Brandenburg calculates that coal utilization efficiency in the trials was about 63%, and that the average ener­gy recovered from the coal was 58%. The product of these two efficiencies yields an overall energy recovery effi­ciency of about 37%. Brandenburg re­gards this as encouraging. He also notes that a second experiment is cur­rently under way at Hanna in which a target of 50% overall energy efficiency has been set. α

Hydrogen in gasoline boosts mileage ^ 169th ACS

··** NATIONAL MEETING Although the hydrogen-powered auto­motive engine seems relegated to the distant future, the addition of hydro­gen to conventional fuels well may pro­vide benefits in the nearer term. Ex­periments at Jet Propulsion Laborato­ry, Pasadena, Calif., indicate that hydrogen additions to gasoline can re­duce most undesirable emissions and provide a significant improvement in mileage as well.

At a symposium on chemistry of combustion in engines, Dr. John Houseman of JPL's technical staff told the Division of Petroleum Chemistry that reduced nitrogen oxides (NOx) emissions in internal combustion en­gines can be obtained with the lower flame temperatures that result from lean combustion. However, combustion of gasoline at its lean flammability limit produces NOx emissions that are still greater than the 1978 Environ­mental Protection Agency standard of

0.4 gram per mile. If hydrogen is burned in the engine at its lean flam­mability limit, the NOx emissions will fall well below the 1978 standard and even below the EPA ambient air stan­dard of 0.255 ppm.

Houseman explains these results by noting that hydrogen has a very low equivalence ratio (0.1) compared with that for gasoline (0.6). The equivalence ratio is defined as the stoichiometric amount of air necessary for combustion of all fuels present divided by the actu­al amount of air present. Houseman further notes that it has been postulat­ed that mixtures of hydrogen and gas­oline could be burned at equivalence ratios below the lean flammability limit of gasoline. This means that only small amounts of hydrogen are re­quired to extend the operating range of gasoline into the ultralean region to meet 1978 EPA standards.

To operate at an equivalence ratio of 0.5 would require addition of about 4% hydrogen to gasoline. This mix would result in emissions that meet the EPA standards for NOx and carbon monox­ide. Still unresolved is how to operate at an equivalence ratio of 0.5 and meet the hydrocarbon emission require­ments. As equivalence ratio is dropped, the quantity of unburned hydrocar­bons, or underburned hydrocarbons, increases. If the hydrogen content of the gasoline is increased to 10%, how­ever, even the hydrocarbon emission standard is met.

Just how an automotive engine could be equipped for hydrogen additions to the fuel is still undetermined. At JPL, some experiments were made by me­tering hydrogen from a storage tank into the fuel as it enters the engine. An alternative procedure might be to di­vert some of the gasoline to feed a hy­drogen generator synchronized with the fuel demand of the engine. However it is done, the addition of 4% hydrogen to fuel an engine operating at an equiva­lence ratio of 0.5 results in a thermal efficiency of about 38%. This result translates into an increase in fuel econ­omy of 40% over conventional fuels, a fact that is prompting continued inves­tigation at JPL. D

Research setup tests addition of hydrogen to gasoline

Rotameters Sonic orifice Hydrogen -•-

Air

Atomizer air

j Atomizer Engine exhaust W / Crankcasevent

Filter Main engine air

Gasoline > WÊÊÊ

Electric motor

Sample line to exhaust analysis bench 4-

April 14, 1975 C&EN 19