Ind. Eng. Chem. Res 1992, 31, 2164-2168
2764
k
9.80
durability testing is needed. Preparation of the prototype 1 blades was done using production methods for mixing and
9.00
-
molding the material. Two deficiencies of EPDM were identified for improvement. First, it would be desirable to improve the low-temperature properties, and second, a reduction in the cost would make it more competitive with NR. Registry No. Ethene-ethylidenenorbornene-propene co-
= 8.20 -
w
7.40
-
6.60 -100
polymer, 25038-36-2; graphite, 1782-42-5.
Literature Cited 80
-60 -40 -20 Temperature. O C
0
20
Figure 5. Storage modulus versus temperature for the baseline natural rubber compound (NR(82)) and EPDM compound R-1814. The EPDM compound starts to get stiffer a t higher temperatures than the natural rubber.
and NR. Figure 4 shows that the dynamic Tgof the EPDM compound is about 15 "C higher than that of the NR. In Figure 5, we observed that the elastic modulus (log E3 of EPDM compound is at a level that could affect the flipping action of the wiper blade. Second, the material cost of the EPDM compound was higher than that of NR. Resolution of these issues will be discussed in a subsequent technical paper.
Conclusion EPDM elastomers have excellent environmental resistance. Replacement of the current NR materials by EPDM would be expected to produce a longer lived blade. In this work it has been shown that the rubber-to-glass friction of EPDM can be controlled while maintaining the physical properties needed in a wiper blade by using relatively high loadings of graphite. Factors governing the wipe quality of the EPDM blades are carbon black size, graphite particle size, and graphite loading. The cure speed of the compound was accelerated by increasing the functionality of the elastomer. Lowering the modulus to accommodate changes in windshield curvature had no adverse effect on physical properties. Prototype blades have been made and have undergone preliminary vehicle evaluations. The results of the study indicated that EPDM blades could be a viable alternative to NR with further development, although longer term
(1) Batt, R. A. Windshield Wiper Systems Expand Plastic Use.
Automot. Eng. 1972,87 (3), 74-78. (2) McLellan, J. The Development of Windscreen Wipers. Rubber Deu. 1971,24 (41, 110-116. (3) Batt, R. A. "Plastic Components for Windshield Wiper Systems"; SAE Paper 790201; March 1979. (4) Nypaver, D. Competition Rouses Slumbering Wiper Giants. Rubber Plast. News 1983, Oct 24, 11-12. (5) Overman, G. R.; Davis, R. G. Squeegee. US.Patent 3,036,297, May 22, 1962. (6) Criegee, R. The Ozonolysis of Olefins and Acetylenes. Presented at the 120th Meeting of the American Chemical Society, Sept 10, 1951. (7) Criegee, R. The Course of Ozonization of Unsaturated Compounds. Rec. Chem. h o g . 1957,18, 111-120. (8)Dunn, J. R. Aging and Degradation. In The Stereo Rubbers; Saltman, W. M., Ed.; Wiley-Interscience: New York, 1977; Chapter 9, pp 511-582. (9) Borg, E. L. Ethylene/Propylene Rubber. In Rubber Technology, 2nd ed.; Morton, M., Ed.; International Thomson Education Publishing, Inc., reprinted by Robert E. Krieger, Co.: New York, 1973; Chapter 9. (10) Ruech, K. C.; Forrester, J. R. Frictional Characteristics of EPDM Windshield Wiper Blades. Rubber World 1971, 165, 54-56. (11)Symbolik, W. S. Squeegee Type Windshield Wiper Blade. U.S. Patent 3,080,596, March 12, 1963. (12) Studebaker, M. L. The Rubber Compound and its Composition. In Science and Technology of Rubber; Eirich, F. R., Ed.; Academic Press: New York, 1978; Chapter 9. (13) Hoffman, W. Sulfur Vulcanization. In Vulcanization and Vulcanizing Agents; Maclaren and Sons: London, 1967; pp 73-352. (14) Boyers, J. T. Fillers Part I: Carbon Black. In Rubber Technology, 3rd ed.; Morton, M., Ed.; Van Nostrand Reinhold: New York, 1987; Chapter 3. Received f o r review April I , 1992 Revised manuscript received August 10, 1992 Accepted August 31, 1992
Pyrolysis/Gasification of Wood in a Pressurized Fluidized Bed Reactor Guanxing Chen,* Krister Sjostrom, and Emilia Bjornbom Department of Chemical Technology, Royal Institute of Technology ( K T H ) , S-100 44 Stockholm, Sweden
The paper deals with pyrolysis and steam gasification of wood in a pressurized fluidized bed reactor. The objective is to study the effect of the treatment conditions on the yield and the reactivity of char. The work shows that in the studied range of the experimental conditions the yield of char is influenced by neither the treatment temperature nor the pressure (650-710 "C and 0.34-1.0 ma). The principal interest is focused on the reactivity of the char in the reaction with steam. It is shown that prolonged exposure of char to high temperature has a negative effect on ita reactivity in s t e a m gasification. Char produced by pyrolysis of wood in nitrogen is much less reactive in the following gasification reaction with steam compared to the char produced in simultaneous pyrolysis/gasification of wood in the presence of steam.
Introduction Gasification of wood is a feasible approach for production of gaseous fuels from biomass. The steam-char reaction is the rate-limiting step in gasification of wood. The
reactivity of char in steam gasification is strongly influenced by the treatment conditions under the pyrolysis and the gasification (Reed et al., 1980;Ekstrom and Rensfelt, 1980; van Dan et al., 1985; Katta and Keairns, 1989).
0888-588519212631-2164$03.00/0 0 1992 American Chemical Society
Ind. Eng. Chem. Res., Vol. 31, No. 12,1992 2765 Table I. Ultimate Analysis of the Wood (in wt W ) C H 0 N aeh 48.2
Slearn
Gas
analysis
f
-5 SICam
generator I-
-Water-
u
Figure 1. LDU fluidized bed reactor system.
Fluidized bed gasifiers are probably the most promising type gasifiers for large-scale utilization. Due to the high heat- and mass-transfer rates in such reactors the devolatilization of biomass and the formation of char are nearly instantaneous. The subsequent gasification of the char is, however, a slower process (Rensfelt et al., 1978). The present paper deals with pyrolysis and gasification of wood in a pressurized fluidized bed reactor.
Experimental Section Equipment. Figure 1 shows the laboratory development unit (LDU)used for the experiments in this study. The pressurized fluidized bed reactor has an inner diameter of 144 mm and a height of 600 mm. The transport disengaging part on the top of the reactor has an inner diameter of 200 mm and a height of lo00 111111. The whole body of the reactor is enclosed in a pressure vessel. The pressure in the system is controlled by a valve which is situated before the condenser. The working pressure of the unit is up to 3 MPa. The maximum working temperature is 900 “C for the reactor and 1100 “C for the reformer. The reformer was designed for further catalytic treatment of the gas, if it is desired. In the present study it was not utilized. The high-temperature filter, manufactured of sintered metal, has a working temperature up to 500 OC. The capacity of the whole unit is up to 15 kg/h biomass. The fluidizing agent, nitrogen and/or steam, enters the bottom of the reactor. The incoming gas is heated by an electric resistance heater situated in the pressure vessel under the reactor. The positive displacement gas meter for the product gas and the tar sample collectors, before and after the reformer, are not shown in the figure. The whole system is conneded to a computer which registers the temperature, pressure, gas flow rates, etc. An on-line computerized gas
5.9
45.2
