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Final Report: Nanomaterial Solutions for Hot Coal Gas Cleanup
EPA Contract Number: EPD08046Title: Nanomaterial Solutions for Hot Coal Gas Cleanup
Investigators: Sankaran, Bala
Small Business: nGimat Co.
EPA Contact: Manager, SBIR Program
Phase: I
Project Period: March 1, 2008 through August 31, 2008
Project Amount: $69,999
RFA: Small Business Innovation Research (SBIR) - Phase I (2007)
Research Category: Small Business Innovation Research (SBIR) , SBIR - Control of Air Pollution
Description:
In the new, state-of-the-art integrated gasification combined cycle (IGCC) technique, the hot (900–1500°C) syngas generated from coal is efficiently used for powering both steam and gas turbines. Federal regulation dictates the generated syngas be nearly free of sulfur. With current method to desulfurize the syngas, it has to be cooled to 500°C and reheated again to continue the IGCC process cycle. Such cooling and heating is energy inefficient. Zinc oxide sorbents currently used in the purification of sulfur have a working temperature of less than 500°C. nGimat can now produce nanomaterials with a large surface area (20–100m2/g) with low temperature desulfurization capability and are working in this U.S. Environmental Protection Agency (EPA) Small Business Innovation Research (SBIR) project to remove sulfur at high temperatures over many cycles. Nanomaterials developed by nGimat via its proprietary NanoSpraySM Combustion technique are stable nanoparticles with excellent surface area retention at elevated temperatures. These new nanomaterials could be used in the hot coal gas cleanup without lowering the temperature to less than 500°C and then back up again, thus dramatically improving the energy efficiency of the IGCC cycle.
Summary/Accomplishments (Outputs/Outcomes):The versatility of nGimat’s proprietary NanoSpraySM Combustion technique allowed production of various compositions of mixed metal oxides, metals and metalloids nanomaterials. High T testing of the produced sorbent nanomaterials for H2S removal identified doped refractory oxide as a top candidate. Our earlier studies have shown this oxide to have good capacity for H2S adsorption and it can withstand high temperatures. Two larger batches (500 g each) of 8 percent and 16 percent metal-doped oxide nanopowders were produced with SSA of 26 and 29 m2/g. A pelletization study was conducted by varying the binder concentration, firing temperature and added alumina concentration, to achieve an optimum pellet with a surface area close to the original nanopowders and with good mechanical integrity. Some of the pellets made with the prime composition nanopowders were coated with other metals to further test the H2S removal capacity of the pellets. Two new bench-scale reactor systems were designed and built in-house with an operating temperature of 900°C and pressure of 150 psi. The materials used in building the reactor system were impervious to the syngas mixture, which was burnt as it exited out of the reactor setup for safety and environmentally friendly testing.
The syngas mixture was passed through a bed of sorbents at 5000 GHSV, 900°C and 150 psi. Sorption and desorption of H2S gas were run consecutively with syngas at 900°C at 150 psi and an air flow rate of 0.2 L/m at 25 psi and 500–600°C, respectively. The first sorption cycle runs for about 2 hours with the following sorption cycles having lower breakthrough time. The H2S sorption capacity for the doped oxide nanomaterials at syngas conditions are in the range of 29 to 37 percent. These H2S sorption capacities are comparable or even better than the commercially used sorbents, which are in the range of 20–25 percent.
Conclusions:A new composition of doped oxide nanomaterials have been produced and studied for their sorbent capacity for sulfur removal from the syngas mixture. The nanomaterials were optimized in their pellet preparation by varying a combination of parameters consisting of binder, surface area modifier (alumina), and the temperature of firing the green ceramic into pellets. A reactor system was designed and built to test the sorbent materials under syngas conditions of 900°C and 150 psi. The breakthrough time, for approximately 15 g of sorbent at 610 mL/min of syngas mixture, ranged from 110 to 160. The calculated capacities of materials were from 29 percent to as high as 37 percent for the first cycle run. We are performing further investigation to identify the source of sorption of sulfur in addition to our material in the reactor system. This is higher than the state-of-the-art sorbent materials used, which have a capacity of 20–25 percent at lower temperature.
With assistance from Foresight Science and Technology (courtesy of EPA), we identified two potential customers who are interested in the technology. We are in communication with these two customers about the nanomaterials we have developed in this program with assistance from EPA through the SBIR Program. The nanomaterials are useful for sulfur removal from any gas stream.
Supplemental Keywords:small business, SBIR, EPA, integrated gasification combined cycle, IGCC, coal gasification, coal gas, syngas, steam turbine, gas turbine, desulfurization, ammonia removal, zinc oxide, nanomaterials, nanopowders, sorption, gettering, nanopowders, nanoparticle, air pollution, desulfurization purification unit, ammonia purification unit, combustion chemical vapor condensation, CCVC, sorption-regeneration cycle life, diesel, automotive, oil, RFA, incineration/combustion, environmental engineering, nanotechnology, combustion byproducts, combustion technology, coal combustion wastes, air pollution control,
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Scientific Discipline, Waste, RFA, Incineration/Combustion, Environmental Engineering, nanotechnology, combustion byproducts, combustion technology, coal combustion wastes, air pollution control, coal fired gasifer combined cycles, desulfurization
Progress and Final Reports:
Original Abstract