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Process for removing mercury from flue gases

a technology of flue gas and mercury, which is applied in the direction of separation processes, dispersed particle separation, chemistry apparatus and processes, etc., can solve the problems of high additional capital costs, insufficient effectiveness of previous techniques for reducing mercury, and restrictive limiting values for legally permissible mercury emission, etc., to suppress free halogens and increase consumption of sulphur dioxid

Inactive Publication Date: 2020-05-12
BROMERC
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  • Application Information

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Benefits of technology

The patent text discusses a process for removing mercury from flue gases in a flue gas emission control system. The process involves adding bromine or bromine compounds to the furnace and allowing them to react with mercury in the presence of sulphur dioxide. The presence of sulphur dioxide is important for the removal of mercury, as it helps oxidize the mercury and allows it to be easily removed from the flue gases. The addition of a sulphur compound can be in the form of free or bound sulphur, or waste sulphuric acid, and the amount added can be controlled to maintain a steady state level in the flue gas. The process can also involve the formation of sulphur dioxide from the oxidation of sulphur and the control of sulphur dioxide in the flue gas to maintain steady state conditions. Sodium bromide can be added to the furnace and result in increased consumption of sulphur dioxide. Overall, the process described in the patent allows for efficient removal of mercury from flue gases.

Problems solved by technology

Owing to the high toxicity of mercury, in particular of organically bound mercury, which is also absorbed by humans directly or indirectly via the food chain, strict limiting values exist for the legally permissible emission of mercury, for example from incineration plants and power stations.
Previous techniques for reduction are not sufficiently effective and, owing to their sometimes high additional capital costs and the additional consumption of operating media are relatively expensive.

Method used

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  • Process for removing mercury from flue gases
  • Process for removing mercury from flue gases
  • Process for removing mercury from flue gases

Examples

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examples

[0034]Examples 1-4 have been carried out in a special hazardous incineration plant of Bayer AG in Leverkusen corresponding to the diagram in FIG. 1. The rotary kiln 3 as primary combustion chamber is fired with solid waste from the bunker 1 via a crane grab 2, with liquid waste from a liquid waste tank and with waste drams via a dram feeder. The afterburning chamber 4, as a secondary combustion chamber, is also fired with liquid waste. The flue gas is cooled via the waste-heat boiler 5 and then, as what is termed dirty boiler gas, fed to the wet flue gas emission control system (multistage scrubber), which encompasses a quench 6, an acid rotary atomizer scrubber 7, an alkaline rotary atomizer scrubber 8 and an electrostatic gas cleanup system involving partial condensation of steam 9. Via suction fans 10 the scrubbed dirty gas, as what is termed clean gas, passes into the downstream catalytic denitrification plant 11 (selective catalytic denitrification of the clean gas by means of ...

example 1

[0036]Over a period of 116 minutes, a series of samples of metallic mercury in plastic capsules (in total 3400 g, see Table 1) were fed to the secondary combustion chamber (afterburning chamber 4) via the inspection port 15. The feed was performed at intervals of approximately 5-10 minutes with increasing amount of mercury. The mercury introduced vaporizes within approximately 2-4 minutes; therefore, the instantaneous peak mercury concentrations occurring in the boiler flue gas at a volume flow rate of approximately 45·103 m3 S.T.P. db / h can be estimated. The estimation at the end of the experiment gives peak mercury concentrations of more than 130·103 μg / m3 S.T.P. db.

[0037]

TABLE 1Addition of Hg samplesTimeHg amount [g]TimeHg amount [g] 9:24 510:32180 9:32 1010:37200 9:38 1510:43220 9:49 2010:48240 9:54 4010:53260 9:59 6010:5828010:04 8011:0330010:0910011:0831010:1512011:1332010:2014011:2034010:26160Experimental time [min]Total Hg amount [g]1163400

[0038]During the experimental perio...

example 2

[0041]Over a period of 130 minutes, an aqueous HgCl2 solution was fed continuously to the secondary combustion chamber (afterburning chamber 4) via a nozzle in the afterburning chamber roof. The rate added was increased here at intervals of about 5 minutes. FIG. 3 shows the increase in mercury concentration thus induced in the boiler flue gas in the time between approximately 10:45 and 13:00. The mercury introduced is immediately released in the afterburning chamber as metallic mercury Hgmet. The total mercury concentration in the boiler flue gas increased in this manner to values of 18·103 μg / m3 S.T.P db (curve 31 and left y axis). The Hg concentration in the boiler flue gas was calculated from the mercury addition rate and the flue gas volume flow rate measured operationally. During the experimental period, by co-incineration of a highly brominated liquid waste (addition via a burner at the rotary kiln head) a bromine content of approximately 9·103 mg / m3 S.T.P. db was maintained i...

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Abstract

Process for removing mercury from flue gases of high-temperature plants, in particular power stations and waste incineration plants in which a bromine compound is fed to the multistage furnace and / or the flue gas in a plant section downstream of the furnace, the temperature during contact of the bromine compound with the flue gas being at least 500° C., preferably at least 800° C. The combustion is carried out in the presence of a sulphur compound, in particular sulphur dioxide. Subsequently to the furnace, the flue gas is subjected to an optional multistage cleanup for removing mercury from the flue gas, which cleanup comprises a wet scrubber and / or a dry cleanup.

Description

[0001]This application is a continuation-in-part of application Ser. No. 10 / 202,571, filed Jul. 24, 2002, still pending.[0002]The invention relates to a process for removing mercury from flue gases of high-temperature plants, in particular power stations and waste incineration plants.BACKGROUND OF THE INVENTION[0003]Owing to the high toxicity of mercury, in particular of organically bound mercury, which is also absorbed by humans directly or indirectly via the food chain, strict limiting values exist for the legally permissible emission of mercury, for example from incineration plants and power stations. Despite the currently already low mercury concentrations of clean gas,—the half-hourly mean value currently permissible in Germany for mercury emissions from waste incineration plants is 30 μg / m3 S.T.P. dry basis (S.T.P. db),—owing to high volumetric flow rates, for example from large power stations, considerable mercury loadings are achieved, so that further reduction of the curren...

Claims

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Application Information

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Patent Type & Authority Patents(United States)
IPC IPC(8): B01D53/64
CPCB01D53/64
Inventor VOSTEEN, BERNHARDKANEFKE, RICOKANEFKE, EWAMUELLER, CLAUSNOLTE, MICHAELKOESER, HEINZBEYER, JOACHIMBONKHOFER, THEODORE-GERHARDFLETH, OLAFSCHNITZER, ANDREAPOHONTSCH, ANDREAS
Owner BROMERC
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