Conversion of Sulfite-Rich Scrubber Sludge into Value-Added Products

FINAL TECHNICAL REPORT

March 15, 1998, through August 15, 1998

Project Title: CONVERSION OF SULFITE-RICH SCRUBBER SLUDGE INTO VALUE-ADDED PRODUCTS

ICCI Project Number: 6-23120

Principal Investigator: Vivak M. Malhotra, Southern Illinois University at Carbondale

Other Investigators: Y. Paul Chugh, Southern Illinois University at Carbondale

Project Manager: Wayne Bahr, OCDM/DCCA

ABSTRACT

The main goal of our project was to convert sulfite-rich scrubber sludge into value-added products by designing and fabricating decorative materials. These materials were to be formed from scrubber sludge and from specially developed, but cheap, clay-polymer binders. The major deliverable product at the end of this project was to be decorative materials of dimensions 6" X 6" X 0.2". We successfully demonstrated for the first time that it is feasible to form decorative materials from scrubber sludges. To the best of our knowledge no such technology existed for flue gas desulfurization scrubber sludges. We also successfully established that it is possible to fabricate composites in different colors and in different sizes, at least up to 6" X 6" X 1". These materials are versatile in that they can be sawed, even with an ordinary hacksaw, can be drilled, and can be glued. Since our materials are considerably cheaper to fabricate than current products and will not burn, this technology provides an economic edge, sounder environmental utilization of the sludge, and potentially safer product.

Pages 1 to 11 contain proprietary information.

EXECUTIVE SUMMARY

The main goal of our project was to develop technology steps required to convert sulfite-rich scrubber sludge from Illinois sources into value-added products. These materials were to be formed from scrubber sludge and from specially developed, but cheap, clay-polymer binders. Specifically, the following objectives were to be the focus of our research for this five months project: a) to develop protocols and engineering procedures for the development and fabrication of value-added products from sulfite-rich scrubber sludge, b) to enhance the mechanical strength of decorative, value-added materials, c) to optimize the types of fiber used and their content for enhanced durability and textural appearance, and d) to upscale the size of the value-added decorative material, produced from sulfite-rich scrubber sludge, from size of 2 inch X 2 inch to 6 inch X 6 inch material.

In support of the aforementioned goals, we fabricated composites in the form of 2.25 inch disks using various variables. The formed materials were evaluated using scanning electron microscopy (SEM), differential scanning calorimetry (DSC), dynamic mechanical analyzer (DMA), and thermomechanical analyzer (TMA) techniques. From these measurements we ascertained:

(a) The composites formed from nylon fibers gave the best modulus values among the three fibers we tested, i.e., nylon, glass, slag fibers.

(b) Our results suggest the mode of mixing of the ingredients has a profound effect on the mechanical properties of the composite formed from scrubber sludge. If they are mixed prior to grinding, the flexural modulus of the composites was much higher than if the composites were formed from a mixture which was mixed just before hot pressing.

(c) The static stress versus displacement in three-point bending mode suggests that the Young's modulus is not affected by the type of modified-polymer used. However, the modulus of rupture was strongly affected. It appears rubber-modified polymer gave the best modulus of rupture for the composites formed from scrubber sludge.

(d) with minor modifications of the procedures developed for forming 2.25 inch disks, we successfully upscaled our composites to 4" x 4" size, primarily in blue, red, and green colors. The composites formed showed excellent structural integrity. Based on these results, we believe that our process will be successful in forming decorative materials at least in the size of 4" X 4" on a large scale.

(e) We also fabricated composites in the size of 6" x 6" x 0.6" range, primarily in green, black and red colors. Initially, we found that the surfaces of our samples were physically deformed due to larger thermal gradient across the sample. This problem was corrected by simply wrapping the die with fiberglass insulation.

(f) Even though we were able to overcome the physical deformation of the sample at the surfaces, there was evidence of the binder burning on the surface. However, on reducing the mass of the ramping plunger we noticed that the burns disappeared. Unfortunately, this was not possible for the present 6 inch die. However, we plan to reduce the thermal mass of the plunger by machining a new plunger of 2 inch thickness size than the current plunger of 5 inch thickness size. This will be done in the future.

(g) We also conducted simple experiments in which we demonstrated that our samples can be sawed with an ordinary hacksaw and can be easily drilled and glued.

(h) We attempted to undertake surface treatment of our composites using various polymers. Generally, depositing EVMX coatings on our composites was successful. We were able to use different color coatings to change the texture of our composites. However, we realized that the injection molding technique would be more successful in generating smoother surfaces meant for table top materials. Recently, we also developed a procedure using YVMA which shows even more promise of generating smoother and lighter color table top materials. We plan to develop lighter color composites next year.

Recommendations for Future Work: The following is proposed:

(1) It will be more beneficial to fabricate table top materials from sulfate-rich scrubber sludge. This is expected to provide better compaction of the composite resulting in better texture and smoother surfaces.

(2) The decorative window sills and decorative tiles should be fabricated from sulfite-rich scrubber sludge.

(3) Recently, we developed a procedure using YVMC which shows considerable promise of forming smoother decorative materials in light colors. This approach needs to be further explored.

The remainder of this report contains proprietary information and is not available for distribution except to the sponsor(s) of this project.