Sulfur Foam and Commercial-Scale Field Application Equipment

13

Sulfur Foam andCommercial-ScaleField Application Equipment

Downloaded by UNIV OF TEXAS AT DALLAS on July 11, 2016 | http://pubs.acs.org Publication Date: March 1, 1978 | doi: 10.1021/ba-1978-0165.ch013

R. W. CAMPBELL, G. L. WOO, E. P. ANTONIADES, and C. B. OLSON Chevron Research Co., Richmond, CA 93802 J. W. ANKERS Chevron ChemicalCo.,SanFrancisco,CA94105

Newly developed sulfur foams were installed with pilot-scale field equipment in 1974 as road subbase insulation to prevent frost penetration at Anderson Road in Calgary and to prevent thawing of underlying permafrost at Dempster Highway near Inuvik. Surveillance of these installations shows satisfactory performance in both cases. A prototype commercial field unit which operates at temperatures as low as —50°F chill factor and lays foams at 800 lb/min has been built. The foaming equipment is housed inside a 43-ft long trailer, which is moved by a specially equipped tractor. The foaming mixture is discharged through multiple nozzles in the spreader at the rear of the trailer. Operation of this equipment was demonstrated recently in Calgary illustrating the practical application of sulfur foam in the field.

Oulfur foam can be used to protect the permafrost by using a combina^ tion of sulfur foam and local embankment materials for road, airfield, and other construction to reduce both the overall cost and the amount of embankment material that needs to be quarried in the arctic wilderness. The use of sulfur foam as subbase insulation prevents thawing of permafrost, which can cause subsidence during the warmer months. Another application uses sulfur foam with conventional pavement construction material for subbase insulation in frost-susceptible areas to prevent frost heave which is caused by freezing of the underlying soil. 0-8412-0391-l/78/33-165-227$05.00/0 Bourne; New Uses of Sulfur—II Advances in Chemistry; American Chemical Society: Washington, DC, 1978.


228 NEW USES OF SULFUR—II

Bourne; New Uses of Sulfur—II Advances in Chemistry; American Chemical Society: Washington, DC, 1978.

13.

CAMPBELL E T A L .

Sulfur Foam and Application Equipment

229

Two field tests were conducted in 1974 to evaluate the above applications of sulfur foam. These tests were jointly sponsored by Chevron and the Sulphur Development Institute of Canada (SUDIC). The first test, installed on a section of Dempster Highway about 40 miles south of Inuvik in the Northwest Territories, was designed for permafrost protection. The 45-ft wide and 130-ft long sulfur foam test pad averaged 4.4 in. in thickness and 11 lb/ft in density, with an average compressive strength of 46 psi. The foam was installed on top of the 1.5-ft thick pioneer fill and then was covered with 3.5 ft of granular overfill, in this case ripped shale, to complete the road section. The second test, placed on a section in the east-bound lanes of Anderson Road in Calgary that had a history of frost heave problems, was designed to prevent frost heave. The sulfur foam pad, 140 ft long and 40 ft wide, was laid on the surface of the existing asphalt concrete road. The average thickness of the foam was 3.4 in. The average compressive strength of the 19-lb/ft foam pad was 163 psi. Following the application of a 1-2-in. leveling course of asphalt concrete, it was covered by 10 in. of asphalt concrete. The hot asphalt application caused no deterioration of the foam surface. The sulfur foams for these tests were foamed-in-place with pilot field equipment at a foaming rate of 100 lb/min. Installation, instrumentation, and performance of these tests have been reported in detail (1,2). Field surveillance data and sample analysis over two years so far indicate design insulation effectiveness and property integrity (Figures 1 and 2, Table I ).


3

3

Table I.

Dempster Highway Installation Performance Original (1974)

Compressive strength (psi) Moisture content (vol %)

44 ± 5 0

Two Years in Service 41 ± 5 0.5

Large-scale uses for this type of foamed-in-place insulation and application equipment are anticipated as the Canadian Arctic is developed. Successful results from these field tests and the prospects of commercial uses of the sulfur foam prompted Chevron Chemical Co. to proceed with the design, engineering, construction, and demonstration of a commercial-scale sulfur foam field application unit. The Sulfur Foam System The proprietary process for making sulfur foam was developed at Chevron Research Co. and uses carbon dioxide as the preferred blowing


230

NEW USES OF SULFUR—II


agent (3,4). Sulfur foams prepared by various methods and their applications have been described previously (5,6,7). Chemically modified sulfur is first made in the form of a concentrate (Chevron Furcoat concentrate), which can be mixed with elemental sulfur to make foam precursor as needed. Molten precursor is then mixed with a polyisocyanate foaming agent (Chevron Furcoat foaming agent) to produce foam. A very small amount of surfactant is also used. Foam concentrate (20-^30 parts)

-f-

Local molten sulfur (70-SO parts)

Foam precursor (100 parts)

Foam precursor (85-95 parts)

+

Foaming agent (5-15 parts)

Sulfur foam (100 parts)

Foam precursor can also be manufactured at a central plant. In this case, it is melted at the field site for use in the foam operation.

Sulfur Foam Properties Sulfur foams with a wide spectrum of properties can be prepared by this process. Properties generally vary with density, which may range from 3 to 45 lb/ft . However, while density is kept constant, properties such as compressive strength, flexural strength, and closed-cell content may be altered by formulation changes. Some of the more common properties are listed in Table II. 3

The biological oxidation rate of sulfur foam depends on available surface area, temperature) and access of necessary nutrients, as well as on foam composition. Preliminary test data indicate that in all cases the oxidation rate is less than that of elemental sulfur. Soil p H around the foams at Dempster Highway measured two years after installation was never lower than the p H of the surrounding native soil (Figure 3). Sulfur foams low toxicity is indicated by the L D of > 5 g A g (rat) and the 100% survival rate in a fish bioassay with stickleback (96 hr) (8). 6 0

Commercial-Scale Field Application Equipment A commercial-scale field foaming unit and melter-mixers have been built and demonstrated. Both were designed to operate at field temperatures as low as —50°F chill factor, which is considered about the coldest practical temperature for carrying out construction work in the arctic. Operation of the overall Furcoat system is illustrated in the Appendix. Mobile Foaming Tractor and Trailer Unit. The components of the foaming unit are enclosed inside at 43-ft long trailer (Figure 4). The


13.

Sulfur Foam and Application Equipment

CAMPBELL E T AL.

Table II.

231

Typical Properties of Rigid Sulfur Foams" Density (lb/ft?)

ASTM Method Thermal condctivity at 8 6 ° F (Btu-in./ hr-ft -°F)> Compressive strength (psi) ' Compressive modulus (psi)' Flexural strength (psi) Flexural modulus (psi) Tensile strength (psi) Resilient modulus (psi) ' Coefficient of linear thermal expansion

D2326

0.24

6.5

10

0.25

0.28

0.34


2

4

( o

F

D1621

25

D1621

~

D790 D790 D1623

~

11

D696

170

50

40

2,500

60 25 5,000 5,000 24 9 16,000 ~ 36,000 19 Χ ΙΟ"" 13 X 10"

e

- l )

Dynamic loading (cycles to failure at 15 psi) ' Water vapor permea bility (perm-in) core one skin intact Water absorption (vol%)' Closed cell content (% of total voids) *

> 10

e

C355

D2127

11 0.8 1.5

9 1.5

D 1940- < 5 62T

Sulfur Foam and Commercial-Scale Field Application Equipment

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