I&EC REPORTS & C O M M E N T S Underground storage of cryogenic liquids
A stubborn waste disposal problem yields
STORING L I Q U E F I E D NATURAL GAS UNDERGROUND Tests show that a full-scale prestressed concrete tank can be cooled in a short time, jilled with a cryogenic fluid, and then permitted to warm without adverse efects on the structure
INSULATION-
HORIZONTAL PRESTRESSING WIRES
T o meet the peak loads of metropolitan areas, depleted oil or gas reservoirs and water-bearing formations have been used as repositories for natural gas. However, such facilities are not always available or have already been developed. Therefore, the American Gas Association instituted a study to examine alternate storage techniques to provide the peaking capacity that is becoming increasingly necessary. Preliminary work indicated that underground storage of the natural gas as a liquid was found to be the most favorable technique. In view of the potential savings to be obtained by placing a concrete tank belowground, a program with the following objectives was set up : -Evaluation of properties of materials at the low temperatures required for liquefaction -Development of a general design and more precise estimate of construction costs for a belowground prestressed concrete tank for LNG (liquefied natural gas) storage -Design, construction, and operation of a scale model demonstration tank Properties of Structural Components at Low Temperatures. Concrete designated as the principal structural component of the tank was so chosen because it provides the necessary rigidity for cylindrical walls, provides support for the roof, and withstands the inward radial forces exerted by the backfill around
the tank. The study by the Portland Cement Association indicated that compressive strength of moist concrete similar to that chosen for construction of the tank walls increased from about 5000 p.s.i. at 75" F. to over 17,000 a t -150" F., and remained essentially constant down to -260" F. Dry concrete showed no strength change with temperature change. Measurements made on the thermal conductivity of moist concrete indicated a =tlOyovariation from the values shown at room temperature, while high carbon steel prestressing wire at -250" F. showed a 20 to 30% increase in tensile strength over that indicated at room temperature. A thin steel barrier located over the concrete slab base to ensure liquid tightness was designed with 9% cryogenic nickel steel. General Design Features. Concrete known to have good strength under compression can take essentially zero stress under tension. By prestressing the concrete during construction the tank would withstand tensile loading. The wall of the proposed tank was to be composed of compacted backfill, a plastic film to prevent adhesion, insulation, pneumatic mortar, prestressing wires, a steel liquid barrier, and the concrete panels. The floor of the tank was designed in two parts: a central portion which formed the bottom of the liquid container, and an outer ring which supported the tank walls and the roof. The roof of the tank
CONCRETE VERTICAL
STEEL
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INSULATION
1
Concrete was selected as the principal structural material in the tank
would include a soil cover, a moisture barrier, insulation, a steel vapor barrier (if needed), and a reinforced concrete dome supported by a prestressed concrete ring, The concrete dome ring supporting the roof could be wrapped with sufficient prestressing wire to maintain compression in the concrete under the radial loading of the weight of the roof and soil cover. The roof of the tank designed to be covered with a relatively thin layer of soil would have a layer of nonabsorbing or reflecting paint as a radiation shield. Heating coils placed in strategic locations around the tank would prevent the formation of concentrations of ice which could lift the tank. Foam glass insulation placed between backfill and the tank would keep evaporation of the gas to 0.1 yostorage volume per day. (Continued on page 70) VOL. 5 6
NO. 1
JANUARY
1964
9
I&EC REPORTS
FomgIas block i d a t i o n , 3 i n c h lkick, shut, and then bandcd into place
100s
Demonstration Tank Test. Upon completion of the design study for a 285,000-barrel LNG tank, a one s k t h linear scale tank w a s chosen as large enough to provide data which could be applied directly to full scale tank design and still be small enough to be practical. Started on October
laid around the tank, moned with polycthylm
9, 1961, and completed on April 3, 1962, the 1000-barrel tank was progressively w l e d with liquid nitrogen until a temperature of - 260 F. was achieved, at which time it was filled with nitrogen and kept full from April 26, 1962, until May 4, 1962. Temperature measurements were gath-
DISWSINQ OF HALOQENATED
HYDROCARBON WASTE A simple combustion and absorption system may help answer a costly problem for the chmical i n d u r h y d i s posal of bypoduct residue from the manufacture of gdastics, inmticzdes, and refrigerants Chlorinated and fluorinated hydrocarbons are the worst. Those which are not biodegradable are usually buried in steel drums or fed to settling ponds with the possibility of ground water or atmospheric pollution. Now a new system of disposal on which a number of patents (Continued on page 12)
Hooker Chmtical's plant ot Niagoro Falls. Qn the n'gfitis thc rcsiduc reactm; left, two carbon t o w s 10
I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
ered by installing 150 thermocouples in key areas in the tank walls, roof, base, and surrounding backfill. Measurements were also recorded of tank movement and evaporation rates. Test Results. Structurally the tank performed satisfactorily and the tests met all objectives. It demonstrated that a belowground prestressed concrete tank could be cooled in a short time, filled with a cryogenic fluid, and then permitted to warm without adverse effects on the structure. The data obtained on heat influx rates and temperature distributions were adequate for checking the design scale-up procedures and also suggested changes in the insulation for the base and for the design of the base ring to improve thermal performance. These improvements incorporated into the final design of large volume belowground concrete tanks indicate that the use of concrete containers could reduce the L. cRmmEs cost of LNG storage.
Long-awaited . . . this one-source reference on accurate short-cut techniques f o r evaluation of jifixed capital investments . . . now here:
.MEN’TALS OF COST ENGINEEIRING CHEMICAL INDUSTRY l
by H. Carl Bauman, Manager, Cost Engineering Department, Engineering and Construction Division, American Cyanamid Company. of preparing estimates. Predicting cash flows during life of project. Current methods for chemical plant cost estimation. Methods for fixed capital cost control, with section on scheduling time and resources. Manufacturing cost estimation. Measuring profitability of ventures. Cost of construction plants abroad. Glossary of cost engineering terms. Tables of conversion data, sizes and weights. Charts covering most frequently used inflation indexes. 416 pages. 1963. $13.50.
For engineers who must be able to estimate costs of project construction and operation, in order to determine the potential profitability of new ventures this book is an invaluable aid. The distinction is made between the scientist, whose basic discoveries are not governed by costs, and the engineer, whose responsibility is to bring a product to the market, with all the cost limitations that may imply. The author has selected methods and techniques which have proved most profitable in use, and emphasizes those which yield greatest accuracy. Contents include: Role of cost engineer in the design, construction and operation of new plants and facilities. General picture of fixed capital costs. Suggested standard cost code. Predicting accuracy of fixed capital costs estimates. Tables of costs for equipment, materials and labor. Short-cuts for estimating cost of building, structures, and auxiliary facilities. Short-cuts for estimating piping systems, instrumentation, insulation and electrical installations. Factors in complete plant costs. Mechanics
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NO. 1
JANUARY
1964
11
I&EC R E P O R T S
New hightemperature antioxidant
IONOX@330 Antioxidant [l, 3, 5-trimethyl-2, 4, 6-tris (3, 5. di ferf butyl 4 hydroxybenzyl) benzene]
-
-
- -
330 is a very effective antioxidant for a variety of chemical products. IONOX
It possesses exceptionally low volatility and is particularly applicable to systems in which high temperatures are encountered in processing as well as use.
Properties Appearance
Colorless crystalline solid
Melting Point 244°C Solubility
Soluble in benzene and methylene chloride; insoluble in water
For product literature and a sample, write to: Product Development Department, Industrial Chemicals Division, Shell Chemical Company, 110 West 51st Street, New York 20, New York. @Registered Trademark
Circle No. 10
12
are pending has been used successfully with wastes containing up to 90y0chlorine. Such materials as hexachloropentadiene, carbon tetrachloride, benzoyl and benzyl chorides, and pentachlorophenol can be easily disposed of. Residues containing from 2 to 15% chlorine generally support combustion. Announcement of the new system was made at the 29th Chemical Industries Exposition in New York by the Carbon Products Division of Union Carbide Corp. under license from Hooker Chemical Corp. The system is designed to completely reduce halogenated hydrocarbons to water, carbon dioxide, and a residual halogen acid by high temperature combustion and subsequent removal of the acid from exhaust gases by absorption. I n four years of development and operation, Hooker has been successful in disposing of wastes containing from 2 to 90y0 chlorine. The two part system consists of a refractorylined burner and either a packed or falling film absorber with an intermediate spray tower to cool exhaust gases. The burner consists of two, concentric cylinders with the inner “chimney’) slightly shorter than the outer shell. Combustion of the residue occurs near the top of the chimney at temperatures of 1600’ to 2370’ F. Once the reaction temperature is reached with auxiliary fuel, the heat of combustion of the waste maintains the high temperatures without further auxiliary fuel. Thermal control of the reaction is maintained by preheating the entering air in the annulus via heat transfer through the chimney. Combustion products pass down the chimney and out the bottom to a carbon spray tower where they are adiabatically cooled before admission to a countercurrent absorber. No free chlorine, carbon monoxide, or hydrogen are discharged from the burner. Dilute
on Readers’ Service Card
INDUSTRIAL A N D E N G I N E E R I N G CHEMISTRY
acid exiting from the absorber may be discarded to existing drainage systems or alternative absorber designs may be used to permit rccovery of commercial strength acid for reuse. Residue systems operated to date have had burners ranging in internal volume from 76 to 1500 cubic feet, but the process has no practical size limitations. The designers estimate total installed cost of a system with a 1000 cubic feet burner and rated at from 4 to 7 gallons per minute or residue, to be about $250,000. Operating costs for such a unit, after initial investment, are estimated at about 6 cents per gallon of residue compared to about 10 cents per gallon for conventional drum disposal. Annual maintenance, material, and labor costs are estimated at about $16,000. Operation of the system is claimed to require less than one man per shift, depending on the degree of instrumentation and control. A built-in safety feature of the system is the integral blowoff lid over the burner. N o unusual safety problems have yet arisen in the experience of the developers. If the residue disposal system is operated to recover commercialstrength acid, the initial investment will be larger but operating costs and manpower requirements will be substantially the same as those cited above. The economy of the system is attributed to the heat recuperation feature of the burner which eliminates the need for additional fuel to maintain reaction temperatures. The virtual elimination of ground water and atmospheric contamination by halogenated wastes through the use of the new system should be welcomed by manufacturers attempting to abide by ever-changing pollution laws. And the added possibility ol recovering commercial-strength acid should be an inducement to those managers who must minimize disposal costs. J . H . S. H A G G I N
