the versatile chemical
T.M
Now reaching beyond historic roles in building and agriculture, lime today has become just about the No. 1 chemical in both diversity and tonnage of uses. With remarkable effectiveness and cost-benefit ratios, among other things modern lime can:
ABSORB ALKALIZE BENEFICIATE CAUSTICIZE CLARIFY COAGULATE DEHYDRATE DISINFECT FLUX NEUTRALIZE PLASTICIZE PURIFY PRECIPITATE REFINE STABILIZE all this and more can be done with
LIME
B&W engineering manager Philip Leopold notes that polyphenylene sulfide has the highest modulus of any of the available thermoplastics and a high tensile strength—10,000 psi at 300° F. The graphite fibers have strengths to 400,000 psi and a modulus of elasticity near 35 million psi. The composite material, B&W says, is resistant to nearly all salt solutions, all alkaline solutions, aliphatic and aromatic hydrocarbons, chlorinated hydrocarbons, and nearly all acids except strong oxidizers, such as nitric. B&W carried out corrosion tests of the composite material, using machined coupons that were exposed for 12 months. It made flexural strength tests before and after exposure to determine the percentage of strength that would be retained. Exposed to 80% sulfuric acid at 200° F, the material retained 79% of its strength. For 19% sulfuric acid at 200° F, the strength retained was 81%. It was also 81% for exposure to 40% ferric chloride at 200° F, and 92% for exposure to sodium hypochlorite at 150° F. Exposed to dichlorobenzene at 200° F, the material showed an increase in strength to 126%, due to increased cross-linking. B&W designed the valve using common metal valve design practice. It is an endentry type valve, with standard length and flange bolting dimensions and a blowout-proof stem. Seats are of polytetrafluoroethyiene. To achieve flange strengths high enough for bolts to be torqued, B&W doubled the thickness of the flange, compared to that of a metal valve. The valve has a high enough bending and tensile strength, B&W says, to allow it to take metallic piping loads. Available in pipe diameters from 1 to 4 inches, the valve is rated at 300° F and 100 psi. The rating is 200 psi for temperatures from - 4 0 ° to 250° F. Du Pont's new pipe combines glassfiber-reinforced pipe with a Teflon fluorocarbon liner. The pipe is made by first extruding a Teflon tube and then bonding it to a wound or hand-laid glass-fiberreinforced plastic overlay. The bonding, Du Pont explains, minimizes the chance of liner failure—as can happen with Teflon-lined steel pipe, for example. And use of the two materials protects pipelines from exterior as well as interior corrosion. The pipe is now available in development quantities in diameter sizes ranging from 1 to 12 inches. When the pipe is commercial, Du Pont expects to sell it in complete systems as prefabricated shop assemblies. Pennwalt has introduced powder coatings of Kynar polyvinylidene fluoride. It is being offered in three grades—essentially, different particle sizes—for fluidized bed for electrostatic spray application and for rotational molding. A primer specially formulated for adhesion is used for the fluidized bed and electrostatic spray applications. Pennwalt intends the product for use in forming protective coatings on metal parts used in chemical process industry. D
Glass-fiber-reinforced plastic pipe has a Teflon fluorocarbon liner
Process control units use microprocessors In process control instrumentation, new items on view at the Chem Show ranged from individual loop controllers to complicated process computer systems. Large or small, most of them seemed to have one thing in common: microprocessors. For example, Sybron's Taylor Instrument division introduced its new singleloop controller with adaptive gain control, the Micro-Scan 1300. The controller incorporates an eight-bit microprocessor with 4000 bytes of "nonvolatile" memory· Unlike fixed-mode controllers, Taylor says, the Micro-Scan 1300 automatically adjusts its gain in response to changes in one or more process variables. The gain may be based on deviation, process, output, remote analog, or contact input, or any combination of those variables. The gain algorithm also may be set for independent effects above and below base gain for each function. Consequently, the controller automatically can compensate for valve characteristics, tank shape, major load changes, and other process variables. Adaptive gain control affords several benefits, according to the company. For instance, it reduces unnecessary manipulations caused by process or measurement noise. It also can produce overdamped averaging control without letting the process exceed specified limits, and it reduces the need for precise tuning to achieve adequate feedback control. Foxboro snowed its new FOX 3 process Dec. 19, 1977 C&EN
23
computer system. FOX 3 incorporates proven features from earlier systems, Foxboro notes, such as conversational program-oriented language and a multiprograming operating system that per mits easy on-line program development. However, advanced microprocessor-based hardware has made it possible to reduce space, lower costs, and improve reliability. New software simplifies system design and operation. Control functions and terminologies are virtually identical with those used in conventional analog system design. Preprogramed control and com putational elements, called "blocks," can be linked together into custom-designed process control schemes. FOX 3 is a natural extension of Foxboro's SPEC 200 electronic control sys tem, the company points out. The average industrial process has dozens of complex control loops that can be improved by computer control. But there are many more loops for which conventional analog instrumentation is often preferable. In the majority of applications, a hybrid system will provide optimum control. With the SPEC 200/FOX 3 system, loops can be assigned to the electronic instrumenta tion, to the computer, or to both, accord ing to where control can best be per formed. Beckman Instruments' new PIDCOM centralized display/distributed control systems embody a somewhat similar
or module, an operations control console, a programable function module, and various input/output modules including cathode ray tubes, printers, and loggers. All these elements are tied together by the so-called ASCII data highway system, Beckman says. The "highway" is estab lished, the company explains, merely by plugging a single computer interface board into each controller. Data trans mission integrity is assured by 100% sender/receiver verification ("echo check") for each data character. The PIDCOM system provides all the benefits of operations console control. Under normal conditions, the plant can be controlled and monitored at the console. Nevertheless, Beckman emphasizes, the console is a supplemental operator inter face tool; individual loop controllers re tain their integrity. Even if part or all of the operations control is shut down, op erators still can run the plant through the individual loop controllers. Micro-Scan 1300 has an eight-bit micro The advent of the microprocessor also processor with 4000 bytes of memory may make it possible to provide smaller operations with the sort of sophisticated philosophy. Beckman notes that its sys control heretofore practical only for large tem is implemented with many discrete installations. Tetrahedron Associates, San computational elements rather than one Diego, intends to fill that particular niche large digital computer. Microcomputers with its Chemical Processing Robots. are embedded in each of the system's According to Tetrahedron, the micro three-mode process controllers. Micro processor-based robot can be "trained" to computers also are the basic functional control an entire reaction—sequencing a components of a communications process variety of operations, confirming that
HEXCEL
PERFORMANCE CHEMICALS
specialty chemicals
Phase Transfer Catalysts: Another of the diverse technological performance chemicals from HEXCEL. Phase-transfer catalysts can be used in nucleophilic substitution reactions, in the formation of carbenes, in alkylation reactions, oxida tion reactions, reductions, and condensations. Addi tionally, these quaternaries are used in elimination reac tions and addition reactions.
215 N. Centennial Zeeland, Michigan 49464 (616)772-2193 205 Main Street Lodi, New Jersey 07644 (201)472-6800
Phase transfer catalysts can also be used as alkaline catalysts when organic func tionality is desired. We invite your inquiries concerning these or other phase transfer catalysts. Call or write for detailed data sheets and samples.
+
+ CH 2 Ν (CH 3 ) 3
CH 2 Ν (CH 3 ) 3
OCH,
Benzyl Trimethyl Ammonium Methoxide + CH 2 Ν (CH 3 ) 3
OH
Benzyl Trimethyl Ammonium Hydroxide 24
C&ENDec. 19, 1977
CI
Benzyl Trimethyl Ammonium Chloride I
/
ν
Ι+ CH 2 N(CH 2 CH 3 ) 3
Benzyl Triethyl Ammonium Chloride
CI
C2H5SH
5
^C>y
JfC Wmi $^éM
r>&
(ù&
THE THIOCRAT
they're being carried out, signaling on completion or in case of malfunction, and even disposing of wastes. Each robot is designed for the specific process it is to control. By reducing manpower requirements, the company says, a robot can pay for itself in a year. D
Coal liquefaction uses oil refining know-how Demonstrated petroleum refining technology could provide the most practical route to a coal liquefaction process. Reasoning from this thesis, Exxon Research & Engineering has moved a major step toward a large demonstration plant for its donor solvent coal liquefaction process. Construction will begin next spring on what still will be called a large pilot plant, to be used to provide data for designing a commercial-size plant. The pilot unit will cost about $110 million and will handle 250 tons a day of coal to be processed into liquid hydrocarbons. These hydrocarbons will have properties that make them suitable as gasoline components and fuel oils. Total cost of the project will be $240 million, with the Department of Energy paying half. Exxon affiliate Carter Oil, the Electric Power Research Institute, and Phillips Petroleum will fund the other
half. Exxon R&E will manage the program and Carter Oil will operate the pilot plant from early 1980 to mid-1982. A 1 ton-a-day pilot plant has been operating for some time at Exxon R&E's Baytown, Tex., facilities to provide process and engineering data on use of various kinds of coal and lignite. Earlier laboratory-scale work began in 1966 on the donor solvent process, so named because a recycle solvent donates hydrogen atoms to combine with the carbon of coal or lignite. This atomic hydrogen plus about an equal amount of molecular hydrogen is used to raise the hydrogen-to-carbon ratio enough to produce useful liquid hydrocarbon products. As designed for the 250 ton-a-day pilot plant and operated in small plants, the Exxon process is energy self-sufficient. Product yields higher than 30 to 45% of the dry feed coal can be obtained if outside energy is supplied. Key to the process is the supply of both molecular and atomic hydrogen, according to Dr. Bertram T. Fant and others working on the coal liquefaction technology. The molecular hydrogen is produced in a hydrogen plant, typical of such plants to supply hydrogen for petroleum refining processes such as desulfurization. The atomic hydrogen comes from part of the recycled liquid product in the process. In effect, the recycled solvent becomes
more aromatic as it gives up hydrogen to the coal. The aromatization of the solvent is changed by hydrotreating, similar to such treating of gas oil being fed to a cracking unit in a refinery. In the process, the hydrogenated solvent, feed coal, and molecular hydrogen are heated, compressed, and sent to a series of reactors where liquefaction occurs. Operating conditions for satisfactory yield and product quality are temperatures from 700 to 900° F, and pressures of 1500 and 2000 psig. These temperatures are less than those needed for other coal conversion processes—pyrolysis at 900° to 1200° F, gasification at 1300° to 1800° F, and direct burning at 3000° F, and up. Pressures are higher than for these other processes, which range between 0 and 500 psig. Effluent from the liquefaction reactors is fractionated at atmospheric pressure as well as under a vacuum to gaseous and liquid products. The light hydrocarbon gases, after removal of acid gases, go to the hydrogen plant. The naphtha makes an excellent gasoline component. The lowsulfur fuel oil—0.8% sulfur from coal containing 4% sulfur—can be sold. Part of this stream is recycled as the solvent. The heavy materials go to afluidcoking process such as the Exxon Flexicoker (C&EN, Dec. 2,1974, page 17). Additional fuel oil is produced along with a char containing the ash from the coal. As part
NIPARison #6: RETARDED Compare the un retouched photos. Same lacquer finish. The difference? NiPar S-30™ in the solvent. The NiPar S-30 finish has superior film integrity. No cotton-like precipitate or milky discoloration. When formulated correctly, NiPar S-30 retards blush, decreases dry time, provides better flow and superior performance in fast air dry systems. Ni-Par S-30 can save you money. NiPar S-30 (nitropropane solvents). It solves your problems... without creating new ones.
26
C&EN Dec. 19, 1977
Without NiParS-30
