KR101275436B1 - Production of activated char using hot gas - Google Patents

Abstract

By devolatilizing and partially oxidizing the carbonaceous feedstock using a gas mixture preheated to high temperature using an oxygen-fuel, oxygen enriched air-fuel or air-burner burner to produce residual activated carbon that can be used for use with activated carbon do. The use of hot gases and pulverized carbonaceous feedstock minimizes the device, so that activated carbon is produced at or near the point of use, for example utility boilers or the like used to reduce mercury emissions from the stream as combustion gases Allow the production of activated carbon at close range.

Activated Carbon, Hot Gas, On-Site Manufacturing, Mercury Removal

Description

Manufacture of Activated Carbon Using Hot Gas {PRODUCTION OF ACTIVATED CHAR USING HOT GAS}

The present invention generally relates to methods and systems that enable the production of activated charcoal at or near the end use site.

Activated carbon is widely used as an adsorbent in industrial processes for removing contaminants from gas or liquid streams. Attempts have been made, for example, to meet pending mercury emission limits for fossil fuel-fired power plants by injecting powdered activated carbon (PAC) into the combustion gas upstream of the particulate control device to remove contaminants from the combustion gas.

It is very important to remove mercury from the flue gas stream of the combustion process. Mercury toxicity to humans has long been known. An example of the destructive effects of mercury exposure occurred in Minamata, Japan, in the 1950s, when organic mercury by-products of acetaldehyde production were released into bays in the area and consumed and metabolized by fish. It has been reported that neurologic damage and birth defects have become widespread in local populations due to its fish consumption.

Coal used in various combustion processes typically contains about 0.1 ppm of mercury. In the United States alone, about 50 tonnes of mercury are released as steam in the exhaust each year. Such mercury can be concentrated thousands of times in fish through chemical and biological processes and enter dangerous levels in human food supplies. In December 2000, the Environmental Protection Agency (EPA) made a regulatory decision that it needed to regulate the release of mercury from coal-fired power plants.

However, one barrier to the use of adsorbents is that both the manufacture of the PAC and its transport to its end use site are expensive. PACs are typically prepared from carbonaceous starting materials that do not initially have adsorptive properties, such as coal, wood, biomass materials, shells of nuts (eg walnut shells, palm fruits) or shells of nuts (eg coconuts) do. Carbonaceous starting materials are adsorbed higher by energy and capital intensive processes, including pyrolysis of the feedstock in a rotary kiln, activating carbon with an active medium (i.e. steam) and pulverizing or micronizing the resulting chars. Converted to PAC material with properties. The activated carbon material must then be transported to its final place of use, such as a coal fired power plant.

Attempts have been made to manufacture PACs near their final place of use. For example, the use of combustion processes to make mercury control chars has been discussed in the patent literature. U. S. Patent No. 6,451, 094 B1 (Chang et al.) Describes injecting feedstock into hot combustion gases to activate the feedstock in situ.

U.S. Patent No. 6,595,147 (Teller et al.) Discloses adding carbonaceous char to combustion gas at a temperature sufficient to devolatilize the material and form activated carbon in situ while the combustion gas is still in the resource recovery system. It is about.

Attempts have also been made to use the carbon found in fly ash to capture mercury from the combustion gases of the coal combustion process. U.S. Patent 5,787,823 (Knowles) has proposed a method for capturing carbon-containing fly ash upstream of the cyclone of a conventional particulate control device (PCD). The captured material is then injected into the duct to capture mercury. US Patent No. 6,027,551 (Hwang et al.) Teaches separating carbon from fly ash captured in conventional PCD and injecting the carbon enriched portion as a mercury sorbent.

U. S. Patent No. 6,521, 021 B1 (Pennline et al.) Teaches the removal of partially oxidized coal from a boiler combustion zone. The separated coal is injected further downstream as a mercury sorbent.

Lanier et al. (US Pat. No. 6,726,888 B2) proposed a control of the combustion process such that both the natural fly ash characteristics for NO _x emissions and mercury removal are controlled.

From both the constraints of general boiler operation and the fact that natural residual carbon decreases as it moves through the boiler, a separate activated carbon manufacturing process is more capable of producing activated carbon with properties suitable for the intended end use. Can provide better opportunities. Accordingly, it would be desirable to provide a system and method for onsite production of activated carbon suitable for a wide range of processes to improve the cost and efficiency of using activated carbon production.

Brief summary of the invention

The present invention provides a method and system for producing activated carbon that is sufficiently flexible and efficient so that activated carbon can be produced at or near its place of use. The methods and systems provided herein may be used in other arrangements. For example, the present invention can be implemented in a central facility that supports a number of utilities and the like by producing activated carbon as described above. In other embodiments, the present invention can be used in utilities that support activated carbon in their own plants and deliver surplus activated carbon to other locations.

The method and system include preheating the gas mixture to high temperature using an oxygen-fuel, oxygen enriched air-fuel or air-fuel burner to form a hot gas stream. This hot gas stream is mixed and reacted with a carbonaceous feedstock (ie, a carbonaceous raw material) to devolatilize and partially burn the carbonaceous feedstock, producing residual activated carbon that can be implemented in a variety of applications using activated carbon. Be sure to

The use of hot gases and pulverized carbonaceous feedstock minimizes the apparatus, thus enabling the production of activated carbon at or near its place of use, for example, to reduce utility boiler mercury emissions from combustion gases.

The present invention includes a method for producing activated carbon at or near the end of use. The oxidizing gas stream at high temperature (preferably about 2,000 to 3,000 ° F.) mixes and reacts with the milled or micronized carbonaceous feedstock to produce powdered activated carbon having adsorption characteristics similar to powdered activated carbon made from the same carbonaceous feedstock. do. Alternatively, the inert gas can be heated and used for pyrolysis of the feedstock. Alternatively, by adjusting the ratio of oxygen to fuel, the hot gas stream may have any desired oxygen content or no oxygen at all (eg CO ₂ and / or H ₂ O). It may be strongly oxidizing, mild oxidizing, or even reducing. For example, a heat source for heat treatment of carbonaceous feedstock may be suitable for use in the present invention. Those skilled in the art will appreciate that the adsorption properties depend on the feedstock used. Those skilled in the art will also appreciate that although the adsorption properties of activated carbon may be sufficient for some applications, it may be necessary to modify the activated carbon for other applications.

Thus, the present invention differs from the ability to produce activated carbon at or near the end of use, a method for producing activated carbon which is less expensive and more efficient than large rotary kiln processes, and the fuel used in the main combustion process of a given plant. It offers several advantages, including but not limited to the freedom of choice to use carbonaceous feedstock for the production of activated carbon. As a result, the present invention provides the flexibility to modify the activated carbon properties for a particular application at or near the end point of use.

The surface area of the activated carbon produced according to the invention may be lower than the surface area of PACs available locally and in some cases may be significantly lower. However, due to the efficient and flexible methods provided herein, the use of activated carbon produced in accordance with the present invention may still be advantageous in terms of overall economics, even in situations where a more activated char may be needed compared to currently available PACs. .

Hot gas streams, which may include steam, oxygen, or gas mixtures, are prepared by preheating the gas stream with an oxygen-fuel, oxygen enriched air-fuel, or air-fuel burner to produce a hot gas mixture. Severe turbulence from hot gases serves to rapidly mix the carbonaceous feedstock with the hot gases. In a preferred embodiment of the invention, the elevated temperature and oxygen concentration of the hot gas cause rapid ignition, devolatilization and partial oxidation of the carbonaceous feedstock.

Elevated temperatures and high oxygen concentrations both have been shown to significantly increase the devolatilization rate of carbonaceous fuels, so the use of oxidizing gases reduces the residence time required to produce activated carbon materials. Consequently, small reactors can be used in place of the large rotary kilns typically used for making activated carbon. In addition, the by-products produced by this method (eg CO and H ₂ ) can be used as fuel for the main boiler or as reburn fuel.

The present invention provides a method and system that makes it possible to produce activated carbon having the desired properties (eg, adsorptive) for a particular application by separating activated carbon production from the main combustion process. For example, but not by way of limitation, the present invention enables the on-site (or close to end use) production of activated carbon for the removal of mercury from flue gas streams. Alternatively or additionally, the present invention enables the production of activated carbon to be optimized for use in fixed bed apparatus for wastewater treatment to remove hydrocarbons and other contaminants. Another advantage of the present invention is that it can be used as a useful fuel for the process by recycling the partial oxidation fuel to a hot gas burner or burning it in a boiler which may or may not be part of the process. For example, gaseous products can be sent to the boiler as reburn fuel for NO _x control.

As discussed above, the hot oxygen or hot gas burners used in accordance with the present invention enable local activated carbon production. The combination of high temperature and good mixing achieved by the burners enables the production of activated carbon in relatively small and simple process equipment (particularly in comparison with rotary kilns currently used for PAC production). Also, in contrast to the rotary kiln process, which typically requires a separate activation step, activation of the activated carbon of the present invention takes place as a result of the process.

Thus, the present invention not only improves both manufacturing efficiency and versatility, but also minimizes the need for transportation, thereby significantly reducing the cost of activated carbon for the end user.

For a more complete understanding of the present invention and its advantages, reference is made to the following detailed description in conjunction with the accompanying drawings.

1 illustrates a schematic diagram of an apparatus for producing activated carbon according to one embodiment of the present invention.

2 illustrates a schematic diagram of an activated carbon production apparatus according to an alternative embodiment of the present invention.

3 illustrates a schematic diagram of an activated carbon production apparatus according to another embodiment of the present invention.

Like reference numerals refer to like parts in some of the drawings.

The present invention provides a method and system for producing activated carbon at or near the end use site of activated carbon. Such methods and systems include preheating the gas mixture to high temperature using an oxygen-fuel, oxygen enriched air-fuel or air-fuel burner to form a hot gas stream. The hot gas stream is mixed and reacted with the carbonaceous feedstock (ie, carbonaceous raw material) to devolatilize and partially burn the carbonaceous feedstock to produce residual activated carbon that can be implemented for use with activated carbon. .

The use of hot gases and pulverized carbonaceous feedstock minimizes the apparatus, thus enabling the production of activated carbon at or near its place of use, for example, to reduce utility boiler mercury emissions from combustion gases.

The present invention includes a method for producing activated carbon at or near the end of use. High temperature (preferably about 2,000 to 3,000 ° F) oxidizing gas streams are mixed and reacted with pulverized or micronized carbonaceous feedstock to achieve similar adsorption characteristics as activated carbon prepared from the same carbonaceous feedstock from typical methods such as rotary kiln processes. Produce powdered activated carbon having Those skilled in the art will appreciate that this adsorption characteristic depends on the feedstock used. Those skilled in the art will also appreciate that although the adsorption properties of activated carbon may be sufficient for some applications, it may be necessary to modify the activated carbon for other applications.

Thus, the present invention differs from the ability to produce activated carbon at or near the end of use, a method for producing activated carbon, which is less expensive and more efficient than large rotary kiln processes, and coal used in the main combustion process of a given plant. It offers several advantages, including but not limited to the freedom of choice to use carbonaceous feedstock for the production of activated carbon. As a result, the present invention provides the flexibility to modify the activated carbon properties for a particular application at or near the end point of use.

Hot gas streams, which may include steam, oxygen, or gas mixtures, are prepared by preheating the gas stream with an oxygen-fuel, oxygen enriched air-fuel, or air-fuel burner to produce a hot gas mixture. The gas mixture is then rapidly mixed with the carbonaceous feedstock. In a preferred embodiment of the invention, the elevated temperature and oxygen concentration of the hot gas cause rapid ignition, devolatilization and partial oxidation of the carbonaceous feedstock.

Elevated temperatures and high oxygen concentrations have both been shown to significantly increase the devolatilization rate of carbonaceous fuels, so the use of hot oxidizing gases reduces the residence time required to produce activated carbon materials. Consequently, small reactors can be used in place of the large rotary kilns typically used for making activated carbon. In addition, the by-products produced by this method (eg CO and H ₂ ) can be used as fuel for the main boiler or as reburn fuel.

Accordingly, the present invention provides a method and system that makes it possible to produce activated carbon having the desired properties (eg, adsorption) for a particular application by separating activated carbon production from the main combustion process. For example, but not by way of limitation, the invention enables the production of activated carbon for micronized fuel combustion utilities for mercury removal in flue gas streams. Alternatively or additionally, the present invention enables the production of activated carbon to be optimized for use in fixed bed apparatus for wastewater treatment to remove hydrocarbons, water and other contaminants. Another advantage of the present invention is that the partial oxidizing gas can be used as a fuel useful for the process by recycling the partial oxidizing gas to a hot gas burner or burning it in a boiler which may or may not be part of the process. For example, gaseous products can be sent to the boiler as reburn fuel for NO _x control.

As discussed above, the hot oxygen or hot gas burners used in accordance with the present invention enable local activated carbon production. The combination of high temperature and good mixing achieved by the burners allows for the production of activated carbon in very small, relatively simple process equipment (particularly in comparison with rotary kilns currently used for PAC production). Also, in contrast to the rotary kiln process, which typically requires a separate activation step, activation of the activated carbon of the present invention takes place as a result of the process.

Thus, the present invention not only improves both manufacturing efficiency and versatility, but also minimizes the need for transportation, thereby significantly reducing the cost of activated carbon for the end user.

As discussed above, the present invention can be used to produce activated carbon suitable for a wide range of industrial processes. The optimal configuration for producing activated carbon for a particular use is thus strongly dependent on the end use and the desired char properties. For illustrative purposes, the ratio of hot gas to carbonaceous feedstock, residence time, temperature of hot gas and additives in the process can be determined based on the intended use of the activated carbon and economic factors.

Referring to FIG. 1, a schematic diagram of an activated carbon production apparatus according to one embodiment of the present invention is shown.

Burner 1 can be used in a variety of ways, the burner design being changed as necessary depending on the manner of operation. In one preferred embodiment, burner 1 is an oxygen-fuel burner and operates on fuel 10 and oxidant source 11 to produce very hot combustion gases. In this embodiment, the oxidant 11 is pure oxygen. In another embodiment, the burner 1 is used in an oxygen concentration operation mode. More specifically, the oxygen concentration of the oxidant 11 is lower than pure oxygen, but higher than air (eg oxygen concentration of about 21 to less than 100%). This embodiment may be undesirable due to the presence of nitrogen in the air. N ₂ in the hot gas can act as a diluent to react with the carbonaceous feedstock and lower the temperature of the hot gas. In another embodiment, the burner 1 operates as an air burner. In this embodiment the oxidant 11 is air. This third embodiment may also be as undesirable as oxygen-fuel due to the presence of N _{2 in} the air. The presence of N _{2 in} the hot gas can act as a diluent for reaction with the carbonaceous feedstock and lower the temperature of the hot gas.

The fuel 10 and the oxidant 11 are supplied to the hot oxygen burner 1. Exemplary fuels as fuel 10 include, but are not limited to, natural gas (NG), methane, propane, hydrogen, diesel, LPG, fuel oil, and coke oven gas. Fuel 10 may be a liquid but is preferably a gas.

In some embodiments, it may be desirable to introduce reactant gas 12 into burner 1 to mix and react with oxidant 11 and fuel 10. Reactant gas 12 may be steam and may be used primarily to obtain the desired composition of gas stream 7 for proper reaction with carbonaceous feedstock in reactor vessel 3. Reactant gas 12 is also used to modify the characteristics of the activated carbon produced in the reactor vessel 3. For example, reactant gas 12 may be used to improve the surface area of the resulting activated carbon produced in reaction chamber 3. It will be appreciated that reactant gas 12 may not always be required.

In certain embodiments in which burner 1 is used in an oxy-fuel or oxygen enriched air-fuel mode, burner 1 is the same as that disclosed in Anderson, US Pat. No. 5,266,024, which is incorporated herein by reference in its entirety. It can be configured as the same hot oxygen burner. The hot oxygen burners can produce high speed, high temperature and high reactive gas mixtures known as "hot oxygen".

Regardless of whether burner 1 is operated in an oxygen-fuel mode, an oxygen enrichment method or an air mode, activated carbon with adsorption properties for the intended end use by burning and partial oxidation of the carbonaceous feedstock 13 It is necessary to have a sufficient amount of oxygen in the gas stream 7 to produce. The oxidation potential of the gas stream 7 is such that it partially oxidizes and does not completely burn the carbonaceous feedstock 13 to produce the desired activated carbon. The amount of oxygen in the gas stream 7 is thus adjusted based on the desired amount of reaction of the feedstock 13. The amount of oxidant 11 and / or fuel 10 may then be adjusted to produce an appropriate amount of oxygen in gas stream 7. It is important not to use too much oxygen to avoid burning too much feedstock 13 which results in poor product yield.

If excess oxygen is desired for stream 7 relative to fuel 10 (for example to enhance reaction with carbonaceous feedstock 13 when no other stream such as steam is available), burner ( The stoichiometric ratio of oxidant (11) fed to 1) will be very excess compared to fuel (10). In another mode of operation, the burner 1 will be operated with an oxidant 11 in which the amount of oxygen is close to the stoichiometric amount relative to the fuel 10 to a very excessive amount.

The hot oxygen burner 1 produces a hot gas stream 7 whose temperature is preferably at least 800 ° F. and most preferably more than 2,000 ° F. The temperature of the hot gas stream 7 is high enough to cause the desired reaction with the feedstock 13 (and any feedstock 13 supported material). Gas stream 7 is mainly composed of combustion products (eg, CO ₂ and H ₂ O), residual oxygen, any unreacted gas from gas stream 12, and when air is used as part or all of oxidant 11 It will probably contain N ₂ . In some embodiments, gas stream 7 may contain more than 70 volume percent residual oxygen and the remainder is combustion products.

As further illustrated in FIG. 1, milled or micronized carbonaceous feedstock 13 is fed to mixing compartment 2 and mixed with hot gas mixture 7. The carbonaceous feedstock 13 may be a carbonaceous raw material, such as various coal, petroleum coke, biomass materials (e.g. sawdust) or shells of nuts (e.g. walnut shells, palm fruits) or shells of nuts (e.g. Coconut). The carbonaceous feedstock 13 can be conveyed to the mixing section 2 by various methods.

The carbonaceous feedstock 13 may be conveyed to the mixing section 2 by entrainment in a carrier gas such as air or combustion gas, by air action, or as a slurry, such as a water slurry. Those skilled in the art will appreciate that other methods of transporting the feedstock 13 may be used, including feeding the feedstock itself without supporting or transporting material. Any oxygen in the carrier stream must be taken into account in the total ratio of oxygen to feedstock (ie the oxygen in the carrier stream is combined with the oxygen in stream 7).

The velocity of the gas stream 7 produced from the burner 1 and fed to the mixing compartment 2 is such that the feedstock 13 is fed to the mixer 2 (eg entrainment in the carrier gas, by aerodynamic action). Regardless of the feed, feed as slurry), the carbonaceous feedstock 13 is sufficiently fast to entrain in the gas stream 7 with any carrier material.

Those skilled in the art will appreciate that the carbonaceous feedstock 13 can be selected based on various criteria, including the end use of the activated carbon produced according to the present invention. For example, in applications where activated carbon is used in a dispersed phase capture mode (eg, mercury capture in a flue gas stream), it may be desirable to use certain finely divided coal. Conversely, it may be desirable to use pulverized coal in applications where activated carbon is used in packed beds (eg, fixed bed apparatus for wastewater treatment to remove hydrocarbons and other contaminants from gas or liquid streams).

Those skilled in the art will likewise appreciate that the residence time in the reactor vessel 3 (discussed herein) will be influenced by the choice of the feedstock 13. For example, compared to the residence time of the milled feedstock, which may be in minutes, the residence time of the finely divided feedstock for the dispersed phase adsorption mode may be in seconds. The carbonaceous feedstock 13 is thus ground or finely ground to the desired size depending on the end use and the device design.

In some embodiments, it may be desirable to pretreat the carbonaceous feedstock 13 with a dopant. For example, the halide salts (eg, NaBr, KBr) can be pretreated so that the halide salts are dispersed in the carbonaceous feedstock 13 before introducing the carbonaceous feedstock 13 into the mixing compartment 2. This may be advantageous for applications where activated carbon is used for the capture and removal of mercury from flue gas streams. Halide salts (eg KBr) can improve activated carbon properties in this type of use. A preferred example of such a treatment is the United States, filed March 14, 2005, entitled "Catalytic Adsorbents For Mercury Removal From Flue Gas and Methods of Manufacture Therefor," which is co-owned by Chien-Chung Chao et al. US Patent Application No. 11, filed September 12, 2005, entitled "Catalytic Adsorbents For Mercury Removal From Flue Gas and Methods of Manufacture Therefor," jointly owned by Patent Application No. 11 / 078,509 and Chien-Cheng Chao et al. / 224,149, which are hereby incorporated by reference in their entirety.

The combined stream 8 thus contains a mixture of feedstock 13 and hot reactant gas 7. Stream 8 is introduced into reactor vessel 3. The reactor vessel 3 may be a refractory lined pipe which is cooled with water as needed. Alternatively, water spray can be used to control the temperature in the reactor.

As also shown in FIG. 1, other additive fluids, solids or gases 14b may be added to the reactor vessel 3. Typical additives 14b may include, but are not limited to, substance (s) having specific activity for the intended use of steam, N ₂ , water, and / or activated carbon. For example, stream 14b may be used to adjust the temperature inside reactor 3 and / or provide steam for the reaction inside reactor 3. Instead of or in addition to additive 14b, additive fluid, gas or solid (eg lime) 14a may be mixed with stream 8 before injection into reactor vessel 3.

As discussed above, the material in reactor vessel 3 causes devolatilization and partial oxidation to produce a product stream containing partial oxidizing gases (eg CO and H ₂ ) and activated carbon. Partial oxidizing gas and activated carbon are withdrawn from the reactor vessel 3 as stream 9.

Those skilled in the art will appreciate that the residence time, the ratio of residual oxygen to the carbonaceous feedstock in the gas stream (7), and the temperature of the reactor vessel (3) are controlled based on the desired properties of the carbonaceous feedstock (13) and activated carbon. . For example, if the residence time is too long, or if the ratio of hot oxygen to feedstock is too high, too much feedstock will be consumed. This can lead to reduced product (ie activated carbon) yields. If the residence time or reaction temperature is too low, the devolatilization and activity may be incomplete, resulting in reduced product (ie activated carbon) quality.

The partial oxidizing gas and activated carbon mixture 9 exiting the reactor vessel 3 is quenched with a quenching medium 15 to cool the product. In some embodiments, it may be desirable to include additives (eg, halide salts for activated carbon (eg KBr) for use in removing mercury from the flue gas stream) in the quenching medium 15 mixed with the activated carbon. A preferred example of such a treatment is US Patent Application No. 11 / 078,509, filed March 14, 2005, entitled "Catalytic Adsorbents For Mercury Removal From Flue Gas and Methods of Manufacture Therefor," which is co-owned by Chien-Cheng Chao et al. No. 11 / 224,149, filed Sep. 12, 2005, entitled " Catalytic Adsorbents For Mercury Removal From Flue Gas and Methods of Manufacture Therefor, " co-owned by Hu and Chien-Cheng Chao et al. Which are hereby incorporated by reference in their entirety.

The quench medium may be a mist of water droplets containing the desired additives, or a gas such as nitrogen.

The cooled mixture 21 can then be separated in the dust collector (or other particulate collection device) 4. The dust collector 4 may not always be necessary, for example in a direct injection use manner (see eg FIG. 3).

Subsequently, some or all of the partial oxidizing gas 16 (eg, carbon monoxide and hydrogen) discharged from the dust collector 4 is supplied to the boiler 5 as the reburn fuel 18a, or the combustion zone of the boiler as the fuel 18b. Can be reversed. Unlike or in combination with using the partial oxidizing gas 16 as the reburn fuel 18a and / or the fuel 18b, some or all of the partial oxidizing gas 16 is removed from the burner 1 in the burner fuel 19 Can be used as).

Activated carbon produced according to the invention is discharged from the dust collector 4 as stream 17 and processed for its intended end use. If activated carbon is used, for example, to capture mercury in the flue gas stream, stream 17 is entrained (not shown) with the carrier gas, injected into the flue gas at a location where the temperature is within the desired range for mercury capture. do. Activated carbon is then collected with fly ash in a particulate control device (PCD) 6 (eg, an electrostatic precipitator or filter fabric) similar to conventional PAC injection for mercury control. Alternatively, activated carbon can be injected downstream of the PCD so that the carbon content of the fly ash is not lost such that it cannot be sold as a cement component. In other embodiments, activated carbon in stream 17 is transported to its intended end use (eg, fixed bed for wastewater treatment).

The embodiment illustrated in FIG. 1 can be modified such that many process steps can be combined in an actual process facility. For example (but not by way of limitation), a laboratory-scale system for producing activated carbon according to the invention is shown schematically in FIG. 2.

In this embodiment, the burner 1 and the reactor 3 are combined in the process equipment. The experiment shows that the carbonaceous feedstock 13 (coal in this example) is ignited while in the mixing compartment 2 (not shown in FIG. 2), which indicates that the ignition is extremely fast. The mixing section 2 is attached to the reactor vessel 3, which is a fire resistant lining pipe. The design of the reactor 3 can be adjusted taking into account the residence time in the appropriate reaction zone 3. The additive fluid or gas 14, such as water or steam, comprises mixing upstream of the hot oxygen nozzle of the burner 1 or mixing in the reactor vessel 3 (as shown in FIG. 2), in the above embodiment. Can be blended anywhere in.

As further shown in FIG. 2, stream (9), in addition to the char produced in the reaction zone (3), is approximately 40 by weight of gas dry weight in CO, H ₂ , CO ₂ and N ₂ (eg, stream 9). % CO, 20% H ₂ , 20% CO ₂ and 20% N ₂ ).

Nitrogen (15) is used to quench the product sent to the dust collector (4). The use of nitrogen 15 as the quenching medium can be replaced with a cooling tube so that the composition of the stream 9 does not change. Alternatively, steam can be used as the quenching medium 15. In this case, the concentrations of hydrogen and carbon dioxide entering the dust collector can be changed differently from stream (9).

The dust collector 4 may be made of stainless steel. Combustible gases can be flared using a natural gas flame. Nitrogen 22 is used as the eductor gas to vent the gas out of the precipitator. Therefore, the gas 24 has a high concentration of nitrogen. The burner 26 shown in FIG. 2 is used as a safety precaution for burning the gas 24. As shown, the gas may pass through a natural gas-oxygen flame.

As also shown in FIG. 2, activated carbon 17 can be collected from the dust collector 4 and further processed and used as discussed above with reference to FIG. 1.

1 illustrates the use of the hot partial oxidizing gas 19 as the fuel of the burner 1 to replace some, if not all, of the fuel 10 for heating the oxidant 11. Another configuration of the present invention is shown in FIG. In this exemplary embodiment, the product 9 from the reactor vessel 3 can be injected directly into the combustion gas 20 for mercury removal from the combustion gas 20. It will be appreciated that stream 9 can be used for a direct injection scheme other than mercury removal. As also shown in FIG. 3, stream 9 may be quenched using stream 15 as discussed above.

In the embodiment illustrated in FIG. 3, the partial oxidizing gas is not combusted. Thus, the activated carbon and the partial oxidizing gas formed in the reactor 3 are injected together into the combustion gas 20. If no dust collector is used, the injection point of the stream 9 (containing activated carbon and partial oxidizing gas) will be more upstream of the combustion gas 20 compared to the configuration where the dust collector is used. This is due to the additional time required to completely burn the partial oxidizing gas. The additional residence time and temperature of the flue gas 20 allows the combustion of carbon monoxide (ie complete combustion). More specifically, the temperature of the flue gas at the injection point of the configuration shown in FIG. 3 may be about 2,000 ° F. in contrast to about 600 ° F. at the injection point of FIG. 1.

Example 1

Several samples of activated carbon were prepared using the experimental equipment illustrated in FIG. 2. Referring to Figure 2, natural gas was used for stream 10, oxygen was used for stream 11, Powder River Basin (PRB), North Dakota Lignite (NDL) ) Or Utah coal was used in stream (13). The halide salt was added to the coal powder by dry or wet mixing.

Listed in Table 1 are the stoichiometric ratios (SR) and chars produced for the production of activated carbon. For comparison, the Nori bit of America, Inc. (Norit America, Inc.) commercially available powdered activated carbon available from the Darko (Darco) ^® FGD characteristics of were also listed in Table 1.

SR _HOB was calculated by dividing the amount of oxygen fed to stream 11 by the amount of oxygen required to complete combustion of the natural gas fed to stream 10. The SR reactor vessel was calculated by dividing the amount of oxygen injected into the reactor vessel 3 by the amount of oxygen required to completely burn the coal fed to the stream 13.

The carbon content of the activated carbon was determined by drying the activated carbon sample using a muffle furnace and then igniting the dried activated carbon sample. The carbon content was then calculated by dividing the difference between the initial mass and the final mass of the ignited sample by the initial mass of dry activated carbon.

The BET surface area of activated carbon was measured using a Micromeritics ^® ASAP 2000 analyzer. Note that the BET surface area of the raw PRB coal is five.

Yields were calculated using the carbon content of activated carbon and performing a mass balance on the ash content of coal fed to stream (13). The ash content on the wet weight basis was 4.47% for PRB coal and 7.4% for North Dakota lignite. Mercury removal by activated charcoal is from the Western Energies' Pleasant Prairie Power Plant, Pleasant Prairie, Wisconsin, 605 MW unit, and also Western coal with a conventional finely divided coal boiler rated at 350 MW. -The combustion utility was evaluated using the Power Research Institute (EPRI) Pollution Control System (PoCT). Both plants burned PRB coal. PoCT was a retention chamber used to simulate the injection of large scale ESP into the first site of use. During the mercury removal evaluation, a slipstream located upstream of the particulate control device at the host site was extracted and injected into the PoCT. Retention times of about 2 and 4 seconds were tested and an activated carbon injection rate of about 6 lb / MMacf was used. Percent mercury removal was calculated by subtracting the mercury emission concentration from the mercury injection concentration, then dividing the total mercury by the injection mercury concentration and multiplying by 100. Experiment number 3 did not evaluate mercury removal. A more detailed description of mercury removal experimental equipment is described in Sjostrom, et al., "Assessing Sorbents for Mercury Control in Coal-Combustion Flue Gas," Journal of the Air and Waste Management Association, Vol. 52, p. 902-911 (August 2002).

The coal used in the experiment numbers 1-3 of Table 1 was PRB. In Experiment No. 4, PRB coal with 1% by weight of NaBr formed by dry mixing was used, and in Experiment No. 5, NDL coal with 0.5% NaBr formed by dry mixing was used. In Experiment 6, PRB coal with 7 wt% KBr formed by dry mixing was used. In Experiment 7, PRB coal with 7 wt% KBr formed by dry mixing was used. In Experiment 8, Utah coal with 1 wt.% NaBr formed by dry mixing was used. In Experiment 9, NDL coal with 1 wt.% NaBr formed by dry mixing was used.

In Table 1, "ND" indicates no measurement. As shown in Table 1, as the SR _HOB decreases, the SR reactor vessel remains constant, but the surface area increases. This is believed to be the result of the increased temperature and the amount of steam in the stream exit compartment 1 of FIG. 2. Temperature, amount of oxidant and exposure time of char to oxidant are important factors in surface area measurements. In general, an increase in any one of these three factors increases the surface area.

In addition, as the SR reactor vessel increased, yield and carbon content decreased, surface area increased and mercury removal increased. The decrease in yield and carbon content is believed to be because more oxygen was supplied to the reactor vessel and as a result more carbon was consumed. It is also believed that the surface area has increased as a result of the explanation given above for the increased surface area due to the increase in SR _HOB .

In experiments 7-9, steam was injected into the product from FIG. 2 (17). It is known to those skilled in the art that steam activation can improve the adsorption capacity of activated carbon. Although steam activation may not be necessary in all cases, it is believed that steam activation with the addition of halide salts is responsible for the high mercury removal in Experiments 7-9.

If the present invention is used to produce activated carbon in a central plant, such as a utility or cement kiln, or in a plant that can burn offgas, the partial oxidizing gas can be used in a boiler (or burner) and the cooled activated carbon is otherwise Can be stored for use. Alternatively or additionally, further treatment of activated carbon (ie post-treatment) to achieve certain desirable properties (eg steam treatment for increasing surface area) or co-owned by Chien-Cheng Chao et al. "Catalytic Adsorbents For Mercury Removal, co-owned by US Patent Application No. 11 / 078,509 and Chien-Cheng Chao, filed March 14, 2005, entitled Adsorbents For Mercury Removal From Flue Gas and Methods of Manufacture Therefor. Activated carbon may be doped with a halide salt, as disclosed in US Patent Application No. 11 / 224,149 entitled "From Flue Gas and Methods of Manufacture There for".

In another embodiment of the present invention, a hot gas stream other than hot oxygen can be produced and used to activate the carbonaceous feedstock material. For example, steam can be dramatically superheated by mixing steam with near stoichiometric amounts of oxygen-fuel burners. The superheated steam will then be used to react with and activate the carbonaceous feedstock. Those skilled in the art will appreciate that if only pyrolysis (ie without combustion) is desired, other gases such as nitrogen may also be superheated in a manner similar to pyrolysis of coal. In this particular embodiment, residual oxygen will not be present in stream 7 (see above figure).

As discussed above, the present invention provides a method and system for producing activated carbon that is sufficiently flexible and efficient so that activated carbon can be produced at or near its end use location. However, it will be appreciated that the production of activated carbon according to the invention is not limited to local production. The methods and systems provided herein may be used in other devices. For example, but not by way of limitation, the activated carbon produced by the present invention can be manufactured in a central plant and used to support a number of utilities and the like. Another exemplary embodiment may include making activated carbon in the utility of its own plant and transporting the surplus activated carbon to another location. It will also be appreciated that the activated carbon produced according to the present invention can be used to replace the PAC product used for other uses. The present invention thus provides versatility and flexibility for manufacturing sites.

Those skilled in the art should understand that the specific embodiments described above may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. Those skilled in the art will also appreciate that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims.

Claims (68)

delete delete delete delete delete delete delete Producing at least one gas stream containing an oxidant and having a temperature of at least 800 ° F., Mixing a carbonaceous feedstock with the one or more gas streams such that the carbonaceous feedstock is devolatilized and partially oxidized to produce activated chars and byproducts, and Quenching powdered activated carbon with a quenching medium comprising a fog of water droplets and a dopant for doping activated carbon. The method of claim 8, wherein the dopant is KBr. Producing at least one gas stream containing an oxidant and having a temperature of at least 800 ° F., Mixing a carbonaceous feedstock with the one or more gas streams such that the carbonaceous feedstock causes devolatilization and partial oxidation to produce activated carbon and by-products, and Quenching the powdered activated carbon with a quenching medium comprising a mist of water drops, A method for producing activated carbon, wherein the activated carbon is further treated with steam to increase its surface area. Producing at least one gas stream containing an oxidant and having a temperature of at least 800 ° F., Mixing a carbonaceous feedstock with the one or more gas streams such that the carbonaceous feedstock causes devolatilization and partial oxidation to produce activated carbon and by-products, and Quenching powdered activated carbon with a quenching medium containing nitrogen. The method of claim 11, wherein the activated carbon is further treated with steam to increase its surface area. delete delete delete delete delete delete delete delete Producing at least one gas stream containing an oxidant and having a temperature of at least 800 ° F., and Mixing a carbonaceous feedstock with the one or more gas streams such that the carbonaceous feedstock causes devolatilization and partial oxidation to produce activated carbon and byproducts, Generating the one or more gas streams comprises mixing an oxidant and a fuel, further comprising mixing steam with the oxidant and a fuel. delete delete delete delete delete delete delete delete delete delete delete Creating a superheated gas stream having a temperature of at least 800 ° F., Mixing a carbonaceous feedstock with the superheated gas stream such that the carbonaceous feedstock causes devolatilization and partial oxidation to produce activated carbon and by-products, and Quenching powdered activated carbon with a quenching medium comprising a fog of water droplets and a dopant for doping activated carbon. The method of claim 33, wherein the dopant is KBr. Generating a superheated gas stream having a temperature of at least 800 ° F, and Mixing a carbonaceous feedstock with the superheated gas stream such that the carbonaceous feedstock causes devolatilization and partial oxidation to produce activated carbon and by-products, and Quenching the powdered activated carbon with a quenching medium, A method for producing activated carbon, wherein the activated carbon is further treated with steam to increase its surface area. Generating a superheated gas stream having a temperature of at least 800 ° F, Mixing a carbonaceous feedstock with the superheated gas stream such that the carbonaceous feedstock is devolatilized and partially oxidized to produce activated carbon and byproducts, Quenching powdered activated carbon with a quenching medium containing nitrogen. 37. The method of claim 36, wherein the activated carbon is further treated with steam to increase its surface area. delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete

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