Inherently concrete-compatible carbon sorbents for mercury removal from flue gas

a carbon sorbent, inherently concrete technology, applied in the direction of sustainable waste treatment, other chemical processes, separation processes, etc., can solve the problems of complex interaction between the sorbent and the aea during concrete manufacture, unfavorable adsorption of aea foaming agents, etc., to reduce the quality of fly ash, the effect of abundant and limited adsorption

Inactive Publication Date: 2016-04-14
CALGON CARBON
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The present invention is about a new sorbent that can remove mercury and other contaminants from flue gas without affecting the quality of fly ash for subsequent concrete use. The sorbent is made from a carbon material and has a specific pore structure that makes it highly effective for mercury removal and compatible with concrete-making foaming agents. The invention offers a cost-effective solution for the electric utility industry and ensures that the properties of the sorbent are optimized for efficient contaminant removal and compatibility with concrete.

Problems solved by technology

The pore structure is tailored such that the adsorption properties become optimally and inherently favorable to mercury removal when exposed to flue gas, yet substantially and simultaneously unfavorable to the adsorption of AEA foaming agents when entrained in fly ash that is used subsequently for concrete manufacture.
The interaction of the sorbent with the AEA during concrete manufacture is complex, involving a number of chemical and physical factors.

Method used

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  • Inherently concrete-compatible carbon sorbents for mercury removal from flue gas
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  • Inherently concrete-compatible carbon sorbents for mercury removal from flue gas

Examples

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example 1

[0031]In this example, the relationship between Iodine Number and the foaming tendencies (AEA exclusion) of the various carbon sorbents is shown in FIG. 1. Iodine Number is normally closely related to total BET adsorption surface area and adsorption pore volume. When compared to BET surface area, Iodine Numbers are usually within roughly 10% of the BET value (H. Sontheimer, J. C. Crittenden, and R. S. Summers, “Activated Carbon for Water Treatment” Second Edition (DVGW-Forschungsstelle, 1988), p. 102, which is incorporated by reference herein). As such, Iodine Number is generally a reasonable indicator of carbon sorbent performance in a given application. However, as shown in FIG. 1, it is clear that this parameter alone is insufficient to specify the composition of a concrete-compatible carbon sorbent independent of the material and process conditions used for its manufacture. For adequate mercury removal from flue gas some minimum Iodine Number or total surface area is generally n...

example 2

[0032]In this example, a relationship is established between the foaming tendencies of the various carbons (AEA exclusion) and a particular region of the carbon pore structure above about 0.01 microns (10 nm) as determined, for example, by mercury porosimetry or comparable techniques. In mercury porosimetry, elemental mercury is forced into the pore structure of the carbon under pressure. Under low pressure, the largest pores are filled first since they offer the least resistance to the flow of mercury. As the pressure is increased, pores with progressively smaller diameters are filled. From the data obtained during a run, the pore diameters and the cumulative and differential pore volumes and surface areas may be calculated for pore diameters roughly 0.003 microns (3 nm) and larger. In this example, it is seen that the pore region most closely related to the foam index of the carbon sorbent lies more in the region dominated by transport meso- and macro-pores having diameters above ...

example 3

[0034]In this example, the relationship between Molasses Number and foaming tendencies among the various carbon sorbents is shown in FIG. 8. Molasses Number is normally indicative of the pore volume of a carbon sorbent spanning the transition between larger diameter adsorption pores and the transport pores that lead to them. Historically, the test has had wide acceptance in the activated carbon arts, but chemical effects, such as pH, and other test variables may sometimes limit the applicability of the results from sorbent to sorbent. Surprisingly, for concrete-compatible applications, a relationship is seen between Molasses Number and the foaming tendencies of the sorbent that is largely independent of feedstock or manufacturing conditions, as shown in FIG. 8. Since the fly ash alone may produce a Foam Index of 4 to 8 drops of MB-VR™, a concrete-compatible carbon sorbent is defined as one with a foam index less than about 30 drops of MB-VR™. This would require a sorbent with a Mola...

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Abstract

A sorbent composition and process of making sorbent designed for the removal of contaminants from flue gas and subsequent use in cement or concrete formulations are discussed. The sorbent composition comprises a coal feed stock prepared to have a total BET surface area of at least 350 m2 / g, and wherein the sorbent has a cumulative surface area less than 10 m2 / g for pore diameters between 0.01 and 0.1 microns, a cumulative pore volume less than 0.055 cc / g for pore diameters between 0.01 and 0.1 microns, or both.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]The present application is a divisional of U.S. patent application Ser. No. 12 / 481,819, filed Jun. 10, 2009, which claims priority to U.S. Provisional Patent Application No. 61 / 060,225 filed on Jun. 10, 2008 and U.S. Provisional Patent Application No. 61 / 073,112 filed on Jun. 17, 2008.BACKGROUND OF THE INVENTION[0002]The preferred method of removing mercury from coal-fired power plant flue gas streams is to inject a sorbent. The preferred sorbent is a porous carbonaceous char, typically an activated carbon. After the carbon is injected into the flue gas stream, it is captured by the particulate capture devices in the power plant and becomes part of the fly ash. Many utilities sell the ash to companies that service the cement and concrete industry which use the ash as a cement substitute. However, the presence of carbon in the fly ash can adversely affect the quality of cement and concrete that is made from fly ash since it tends to adsorb...

Claims

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Application Information

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IPC IPC(8): C04B18/10B01J20/20B01J20/28B01J20/30
CPCC04B18/10B01J20/3042B01J20/28071B01J20/28061B01J20/28085B01J20/20B01D53/02B01D53/10B01D2253/102B01D2253/25B01D2253/306B01D2253/308B01D2257/602B01D2258/0283B01J20/027B01J20/28011B01J20/28064B01J20/28066B01J20/2808C04B18/084C04B28/02C04B2111/1093C01B32/30Y02W30/91C04B2103/304
Inventor POLLACK, NICHOLAS R.HAYDEN, RICHARD A.
Owner CALGON CARBON
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