초록 ▼

Methods by which new or used boilers or furnaces ranging from small industrial to the largest utility units that are designed for coal or oil or natural gas or shredded waste or shredded biomass firing can substantially improve their technical operation and sharply reduce their capital and operating

Methods by which new or used boilers or furnaces ranging from small industrial to the largest utility units that are designed for coal or oil or natural gas or shredded waste or shredded biomass firing can substantially improve their technical operation and sharply reduce their capital and operating costs by implementing component modifications and process steps that (a) minimize the adverse impacts of coal ash and slag on boiler surfaces and particulate emissions thereby also facilitating the use of oil or gas designed boilers for coal firing, (b) drastically reduce the loss of water used to transport coal in slurry form to power plants, (c) essentially eliminate the combined total nitrogen oxides (NOx), sulfur dioxide (SO2), mercury (Hg), trace metals, and carbon dioxide (CO2) emissions, (d) separate and permanently sequester carbon dioxide released during combustion and (e) improve the coal and solid fuel combustion efficiency.

대표청구항 ▼

What is claimed is: 1. A method whereby slag formed from solid fuel ashes during combustion in boilers or furnaces is suppressed by introducing additional air in a post-primary combustion zone to lower the combustion gas temperatures below temperatures at which the ash softens or liquefies and adhe

What is claimed is: 1. A method whereby slag formed from solid fuel ashes during combustion in boilers or furnaces is suppressed by introducing additional air in a post-primary combustion zone to lower the combustion gas temperatures below temperatures at which the ash softens or liquefies and adheres to boiler or furnace surfaces. 2. The method in accordance with claim 1, wherein the slag formation is suppressed with metal oxides particles, including at least one of calcium, magnesium, iron, chrome oxides, that are injected in dry or slurry form, and in quantities that increase fuel ash softening and melting temperatures above the gas temperatures wherein the ash particles are entrained. 3. The method in accordance with claim 2, wherein the metal oxides also control gas emissions, including at least one of NOx, SO2, CO2, and trace metals including at least one of arsenic, lead and mercury. 4. A method in accordance with claim 3, wherein a selection of the metal oxides is determined from temperature and composition phase diagrams based on combined chemical compositions of metal oxide additives and the fuel ash. 5. A method in accordance with claim 4 to suppress the deposition and adhesion of ash or slag particles on a boiler or furnace by injecting quantities of metal oxides that are less that the quantities required to impact chemical properties of fuel ash as determined from the solid phase diagrams of the ash and the ash control additives but sufficient to deposit as solids on to the surface of fuel ash particles that operate in boiler or furnace gas temperature zones high enough to soften and melt the ash particles but not high enough to soften or melt the solid additives, which are injected at concentration that can be as low as one percent, thereby rendering the fuel ash friable and sharply reducing or even eliminating ash or slag deposition on furnace or boiler surfaces. 6. The method in accordance with claim 1, wherein, for use in high ash coals, greater than 10%, fluxing agents including limestone are used in air-cooled, slagging combustors to remove up to about 80% of coal ash as liquid slag, while a balance of ash exiting a combustor is treated as in claim 1 to suppress ash deposition on the boiler or furnace to which the combustor is attached. 7. The method in accordance with claim 1, wherein, for use in coals with about 5% of less ash, a conventional pulverized coal burner is used for the boilers and furnaces. 8. A method comprising fueling a coal fired power plant fueled by a coal-water slurry pipeline, wherein an air-cooled slagging combustor replaces coal burners to achieve efficient combustion, and exhaust combustion gases are cooled with water droplets sprays to about 150° F. in order to condense and recover a bulk of the slurry water. 9. A method comprising a final combined level of reduction of nitrogen oxides, (NOx), at an exhaust stack by reducing fuel rich operation of low-NOx burners in a primary combustion zone of coal fired boilers or furnaces followed by reducing in a post-combustion zone final combustion air and followed by removing Selective Catalytic Reduction (SCR) system, and in its place reducing a resultant increased NOx emissions in the post combustion zone by a Selective Non-Catalytic Reduction (SNCR) process that has no adverse impact on ammonia slip, and adding reburn with biomass to duplicate NOx emissions achievable with an original operation of the low NOx burners and the SCR. 10. The method in accordance with claim 9, wherein any additional NOx emission reduction is accomplished by purchase of NOx emission allowances. 11. The method in accordance with claim 9, wherein the SNCR process comprises inserting multiple flat plane air atomized droplets of aqueous solutions of urea or ammonia at an edge of an entire boiler or furnace post-combustion gas cross-section wherein the NOx reducing reaction is effective 12. The method in accordance with claim 11, wherein diluting water flow for urea or ammonia is increased as needed to lower combustion gas temperature to a range at which NOx reduction is optimum, between 1800° F. and 2000° F., and wherein power lost by the gas cooling is replaced by increasing coal flow. 13. The method in accordance with claim 9, wherein a degree of NOx reduction by low NOx burners is reduced to enable firing of low volatile, low sulfur coals to reduce sulfur dioxide emissions, SO2, without any significant loss of unburned carbon in boiler or furnace exhaust. 14. The method in accordance with claim 9, wherein mass flow of biomass utilized for reburn is increased to reduce non-renewable flow of carbon dioxide, CO2, exiting to atmosphere by about 15% or more from levels achieved with 100% coal combustion. 15. The method in accordance with claim 9, further comprising operating coal fired boilers and furnaces to minimize emission and minimize capital and operating costs. 16. A method whereby coals, primarily bituminous coals that have most or all of their mercury in pyrites in concentrations related to arsenic content in the pyrites, have the mercury removed by utilizing air-cooled slagging combustors and impacting the mercury containing coal slag particles in a slag layer lining a wall of a combustor and draining and water quenching the slag from the combustor within about 3 to prevent the mercury trapped in the slag from re-evolving from the slag as a gas into the combustion gases. 17. A method for controlling in boilers or furnaces slag and ash depositions on refractory and metal walls exposed to ash and slag laden particles from coal combustion by co-injecting with coal in a primary combustion zone or in an immediate post-combustion zone metal oxide particles in concentration of less than 1% of total coal feed for attaching to a surface of coal ash or slag particles, thereby inhibiting adherence to each other and to the metal walls. 18. The method in accordance with claim 17, wherein metal oxide additives are selected from phase diagrams of coal ash and injected metal oxide mixtures which have liquefaction temperatures that are higher than liquefaction temperatures of the coal ash. 19. The method in accordance with claim 18, wherein the metal oxides particles in a 10 micron range are dispersed in air atomized, aqueous droplets of varying diameters throughout combustion gases in the primary combustion zone and post-combustion at gas temperatures above about 2000° F. 20. A method whereby lime particles, nominally of about 9 microns in diameter are dispersed in water at concentrations up to 30% by weight and injected as air atomized droplets to intercept post-combustion gas flows in a temperature range of 1800° F. to 2400° F., utilizing injectors with capacities to disperse aqueous lime mixtures at up to a mol ratio of calcium oxide to sulfur dioxide of three (3), and sufficient water flow capacity to cool a combustion gas zone being treated to gas temperatures at which CaO--SO2 capture reaction is maximum, being about 1800° F., with additional coal being fed through primary burners to recover energy lost in cooling the combustion gases to said temperature range. 21. The method in accordance with claim 20, wherein limestone of essentially identical particle size replaces lime, and a concentration of the limestone is increased by use of stabilizers and surfactants to increase the limestone concentration in water to up to nominally 50%. 22. The method in accordance with claim 21, wherein, if lime or limestone is used excess limestone recovered in particulate collection systems of a boiler or furnace is to be used to form emulsions comprising liquid carbon dioxide, water and the limestone to form calcium bi-carbonate for sequestration underground or in Oceans at depth sufficient to prevent release of carbon dioxide as gas. 23. The method in accordance with claim 22, wherein the emulsions are augmented with finely pulverized limestone to further increase a quantity of carbon dioxide reacted to form the calcium bi-carbonate. 24. The method in accordance with claim 23, wherein air-cooled slagging combustors are utilized as primary coal combustors for boilers or furnaces to remove about 75% of coal ash as slag and thereby increase a ratio of the limestone to coal ash or, if necessary, simplify removal of the coal ash prior to preparation of the water-carbon dioxide-limestone emulsion. 25. The method in accordance with claim 20, wherein the CaO--SO2 reaction replaces flue gas desulfurization processes. 26. The method in accordance with claim 24, wherein emulsion preparation is utilized to augment removal and sequestration of CO2 by compression of nitrogen-carbon dioxide exhaust gases followed by dispersal in water and removal of the compressed nitrogen by expansion in a gas turbine and pumping high pressure carbon dioxide-water solution into underground limestone formations to form calcium bi-carbonate. 27. The method in accordance with claim 21, wherein the lime or limestone is used for SO2 capture, and porous calcined calcium oxide particles that are not reacted with SO2, react with atomic and molecular mercury and other trace metal including arsenic for removal from the combustion gases in the downstream sections of a boiler or furnace that are at severl 100 degrees Fahrenheit. 28. The method in accordance with claim 20, wherein any additional SO2 emission is accomplished by purchase of SO2 emission allowances. 29. The method in accordance with claim 20, further comprising operating coal fired boilers and furnaces to minimize emission and minimize capital and operating costs.