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US 8,496,894 B2Granted
Method and system for controlling mercury emissions from coal-fired thermal processes
AssigneeADA-ES, Inc.
InventorsMichael D. Durham, Sharon Sjostrom, Kenneth E. Baldrey
Life of this patent
Estimating the term…
Abstract
The present disclosure is directed to the use of elemental or speciated iodine and bromine to control total mercury emissions.
Claims74
A method, comprising:
- providing a mercury-containing gas stream comprising vapor-phase mercury, a vapor-phase iodine, and particulates;
- passing the mercury-containing gas stream through a selective catalytic reduction zone;
- and
- thereafter removing particulates from the mercury-containing gas stream to form a treated stream, at least a portion of the vapor-phase mercury being removed from the mercury-containing gas stream with removal of the particulates, wherein at least one of the following is true:
- (i) the mercury-containing gas stream comprises about 3.5 ppmw or less vapor-phase iodine;
- (ii) in the mercury-containing gas stream, a molar ratio of vapor-phase iodine to vapor-phase mercury is no more than about 600;
- (iii) at an air preheater outlet, a concentration of vapor-phase iodine ranges from about 0.1 to about 10 ppmw;
- (iv) a concentration of the iodine is about 30 ppmw or less relative to a weight of a mercury-containing feed material producing the vapor-phase mercury.
5 more elements
A method, comprising:
- contacting a mercury-containing feed material with a halogen-containing additive to form a treated feed material, the halogen in the halogen-containing additive being one or more of iodine and bromine;
- generating from the treated feed material a mercury-containing gas stream comprising vapor-phase mercury, a vapor-phase halogen, and particulates;
- passing the mercury-containing gas stream through a selective catalytic reduction zone, a temperature of the mercury-containing gas stream in the selective catalytic reduction zone being at least about 250′Celsius;
- and
- thereafter removing particulates from the mercury-containing gas stream to form a treated stream, at least a portion of the vapor-phase mercury being removed from the mercury-containing gas stream with removal of the particulates.
2 more elements
A method, comprising:
- combusting a halogen-containing additive and a carbonaceous feed material to form a mercury-containing gas stream comprising vapor-phase mercury, particulates, and a vapor-phase halogen;
- thereafter contacting the mercury-containing gas stream with a mercury active agent other than the halogen-containing additive, the mercury active agent being capable of oxidizing elemental mercury;
- and
- thereafter removing particulates from the mercury-containing gas stream to form a treated stream, at least a portion of the vapor-phase mercury being removed from the mercury-containing gas stream with removal of the particulates.
1 more element
A method, comprising:
- providing a mercury-containing gas stream comprising vapor-phase mercury, a vapor-phase iodine and/or bromine, and particulates;
- passing the mercury-containing gas stream through a selective catalytic reduction zone comprising a selective catalyst reduction agent;
- and
- thereafter removing particulates from the mercury-containing gas stream to form a treated stream, at least a portion of the vapor-phase mercury being removed from the mercury-containing gas stream with removal of the particulates, wherein at least one of the following is true:
- (i) the selective catalyst reduction agent has an effective SO2-to-SO3 oxidation rate of lower than about 2%;
- (ii) an air preheater outlet temperature is no more than about 150° Celsius;
- (iii) an ammonia slip at a stack is no more than about 5 ppmv;
- (iv) the mercury-containing gas stream is formed from combustion of a feed material having no more than about 1 wt. % total sulfur (dry basis of the coal);
- (v) the mercury-containing gas stream is formed from combustion of a feed material having an alkali content of at least about 20 wt. % (dry basis of ash);
- and
- (vi) the mercury-containing gas stream has, at a particulate control device, a SO3 concentration of no more than about 7.5 ppmv.
8 more elements
A method, comprising:
- providing a mercury-containing gas stream comprising vapor-phase mercury and a vapor-phase halogen;
- contacting the mercury-containing gas stream with a particulate mercury active agent upstream of an air preheater;
- and
- removing the particulate mercury active agent from the mercury-containing gas stream, wherein at least a portion of the vapor-phase mercury collects on and is removed with the particulate mercury active agent.
1 more element
A method, comprising:
- generating, from a mercury-containing feed material and a halogen additive to the mercury-containing feed material, a mercury-containing gas stream comprising vapor-phase elemental mercury and a vapor-phase halogen;
- contacting the mercury-containing gas stream with a diatomic elemental halogen upstream of an air preheater, the non-halogen mercury active agent and vapor phase halogen converting elemental mercury into ionic mercury;
- and
- removing the ionic mercury active agent from the mercury-containing gas stream.
1 more element
Dependencies are inferred from the claim text.