A filter may be used in conjunction with the tank 66 in a pipe 68 to collect the carbon from the reaction product. The carbon is in turn recycled to bed Reactor 10 contains an inlet plenum 11 , distributor plate 60 with bubble caps and bed drain s 64 for discharge of the solid reaction products. Reaction zone 13 contains the bed 54 and at least one recycle port Optionally, there are observation ports 70 and a drain Reactor 10 also includes a larger diameter drying zone 15 with the black liquor spray assembly 12 , fill nozzles 74 , and product gas outlet As mentioned earlier, in the preferred embodiment, a hot fluidizing means 19 enters the plenum 11 at a pressure in the range of 6 to 12 psig with the preferred pressure of about 8 psig and at a temperature ranging from about F.
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The fluidizing means heats and fluidizes bed 54 at a preferred temperature range of F. Fluidizing means 19 includes oxygen, air, steam, carbon dioxide, malodorous gas, or mixtures thereof. In this embodiment, there are two fluidized beds 54 , 76 operating in series with respect to gas flow. Throughout the several views, like numerals designate like or similar features.
The fluidizing gases for the gasification reactions enter the process as relatively cold streams at the lower fluidized bed Air at this temperature is obtained in a steam coiled preheater 46 with 50 PSI steam. Processed steam 3 is also provided to the reactor 10 for the bed The processed steam 3 is generated using a flue gas waste heat boiler Both the air stream 2 and the steam stream 3 are too cold to add directly to the gasification bed A significant fraction of the total heat input is required just to bring them up to bed temperature.
Thus, a heat exchanger 78 is preferably used in bed Any other suitable external heating method may also be used. The air stream 2 and the steam stream 3 are heated to the operating temperature of the bed 76 which is approximately F. The fluid stream 19 will very rapidly cool or heat to the actual operating temperature of the upper fluidized bed 54 but does not heat the upper bed 54 above the particle melting point.
The lower fluidized bed 76 uses inert bed materials such as calcium sulfate, sand or aluminum oxides which have a high melting temperature. Because there is no danger of melting the bed material, the surface temperature of the lower heat exchanger 78 can be much higher than the temperature of the upper heat exchanger If desired, heat input 79 to the lower external heat exchanger 78 can be supplied by burning a fraction of the product gas 58 within the heat exchanger 78 , or any known combustion source like a natural gas burner can be employed. Any unreacted carbon removed by the filter at the dissolving tank 66 can be recycled back into the system.
By recycling the carbon, an improvement in the overall process gasification efficiency for the reactor 10 is provided. This recycling not only solves the problem of disposing of dregs but also maintains a high thermal efficiency for the reactor Another method of increasing the heating value of the product fuel gas 58 is to use pure oxygen 4 if available, as the gasifying medium in place of the air 2.
The use of oxygen increases the caloric value of the product gas. However, the use of pure oxygen 4 as a supplement to the air stream 2 results in oxygen enriched air and gains the advantage of increased heating value of the product gas 58 while maintaining adequate fluidization of the reactor Using pure oxygen 4 to enrich the gasifying air stream 2 is practicable in many paper mills. Oxygen bleaching is also widely used to replace chlorine bleaching in these mills. The use of oxygen in waste water aeration systems is not uncommon; and the additional oxygen demand of the gasifier should be enough for the paper mill to utilize an on-site air separation plant which would lower the overall oxygen costs for the paper mill.
Another source of air for the gasifier 10 is a malodorous gas source 5 such as a high volume low concentration HVLC waste gas which is a stream which originates in the vents and hoods at many locations of the mill. The waste gas stream 5 contains low concentrations of many malodorous gases such as mercaptans and is generally saturated with water vapor.
These gases are normally disposed of by incineration or as air supply to the lime kiln but are normally a thermal drain due to their high moisture content. Because both steam and air are used in the present invention, the malodorous gases 5 provide a means for solving the disposal problem encountered by the paper mills. Additionally, a low volume high concentration LVHC steam source can also be used as an oxygen source for the reactor This offers the advantage of capturing additional sulfur and reducing mill sulfur make-up.
The present invention uses a blend of air 2 , steam 3 , and oxygen 4 in order to achieve a higher Btu efficient product gas Carbon filtration and recycling provide an efficient carbon conversion and result in low external heat input. By burning the ungasified carbon 80 in the lower fluidized bed 76 , the indirect heat input is supplemented and increases the overall thermal efficiency of the reactor Additionally, the present invention provides a more efficient paper mill process by using the gasifier 10 in order to dispose of HVLC waste gas 5 produced by the mill.
Returning to FIG. An aspect of this invention uses a condensing heat exchanger CHX 26 as a heat recovery unit and H 2 S scrubbing system for the product gas resulting from gasification of fuels containing sulfur particularly black liquor from pulp and paper production. In the preferred embodiment, all surfaces exposed to product gas are covered with an inert substance or coating like polytetrafluoroethylene PTEF or other fluoroplastic such as fluorinated ethylene propylene FEP or tetrafluoroethylene TFE.
Other inert materials such as glass, graphite, alloys, metals, or other inert coverings can be used. This provides an environment where low temperature heat recovery can be accomplished without concern for gas side corrosion. Therefore, sensible and latent heat can be recovered and added back to the process for increased cycle efficiency. The coating also resists scale formation in the condensing section.
Potential of hydrothermal black liquor gasification integrated in pulp production plant
The result is a clean dry product gas. Product gas enters the first heat exchanger 82 at about F. Boiler feedwater 83 or process water can be used as the cooling fluid. The heated feedwater can be used elsewhere to generate necessary process steam. Process water could be used elsewhere in the system, or for reheating the product gas as in reheater Product gas is then channeled to the second heat exchanger 84 section which operates in a condensing mode. Product gas is cooled to below the adiabatic saturation temperature. In this section both particulate and H 2 S removal take place. Droplets form around the gas born particulate matter and condense on the cooled fluoroplastic coated tubes.
Reagent 88 in the form of typical green liquor is introduced such as by spraying 90 in the polishing section 28 and as required at the inlet 92 to and the exit from 91 the second heat exchanger section Other suitable reagents include soda ash, caustic soda, amines, alkali salts, water-soluble alkali salts, or mixtures thereof. H 2 S removal takes place in this condensing section. A sump 98 receives condensed liquid and liquor and supplies it to tank through a pipe where it is recycled via pump Water preferably at or below 80F.
The temperature and quantity of water can be varied to control the product gas temperature for optimum H 2 S removal and to minimize undersirable CO 2 absorption.
Black Liquor Gasification - Technopolis Group
The condensing section is followed by an optional polishing section 28 where counter current gas-liquid contacting and final H 2 S removal takes place. This section can utilize either a packed tower, trays or other mass transfer device, or an inert heat exchanger as previously described to supply the appropriate amount of mass transfer surface. Fresh chemical make-up 94 is supplied to the upper spray Zone 90 to optimize chemical usage and maximize H 2 S removal efficiency. A separator 96 such as a cyclone separator or mist eliminator follows the polishing section to remove mists or fluids from the product gas The system of the present invention is readily extendable to pressurized operation.
The entire system can be pressurized in one of two ways. The first option is to pressurize the entire system consisting of pressure vessels for each subsystem or component. The second option is to employ low pressure components or subsystems surrounded by a larger pressure vessel as seen in FIG. High pressure operation is desirable and often necessary for use with a gas turbine. Of course, the exported product gas may be pressurized just prior to use with a gas turbine. The system of the present invention is self-contained, i.
Feedwater intake and steam production are quite minimal. The system is adaptable to a variety of liquors from wood, bagasse, straw etc. There are no heating surfaces in contact with the bubbling fluid reaction bed in the embodiment of FIG. Some heaters may be used for start-up. The low temperature design eliminates the formation of smelt and the possibility of smelt-water reactions, reduces fouling potential, and reduces the need for cooling the gasifier vessel.
There are no moving parts nor mechanical devices except the fans, blowers, and rotary seals. The present invention includes reheat of the product gas for transport. The reheated gas will also facilitate the combustion of the low BTU gas in the boiler. The advantages of the CHX scrubbing system in the present invention include but are not limited to the following.
It combines heat recovery with H 2 S removal. Sensible and latent heat are recovered for improved cycle efficiency. It removes fine particulate. There is selective H 2 S absorption by controlling scrubbing conditions such as temperature and chemistry. There is selective H 2 S absorption by controlling chemical make-up location. The system provides corrosion resistant gas side heat transfer and mass transfer surfaces. The system also provides scale resistant gas side heat transfer and mass transfer surfaces.
It allows for boiler feedwater heating for improved efficiency. While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles. Effective date : Year of fee payment : 4. Year of fee payment : 8. A system and method for producing product gas using residual waste liquor is described with a gasifier reactor having a fluidized bed located therein. The gasifier reactor is heated to a predetermined temperature range with either an external heater or a second fluidized bed located at a position below the first fluidized bed.
Condensing heat exchanger means recovers heat from the product gas and condenses an acid gas therefrom for recycling the chemicals. A reagent is sprayed in the condensing heat exchanger means to clean the product gas. Pressurization allows the cleaned product gas to be directly fired in a turbine.
This is a divisional of application Ser. Field of the Invention The present invention relates, in general, to fluidized bed gasification systems and in particular, to a new and useful self-contained system for gasifying a residual waste such as black liquor. Description of the Related Art In the pulp and paper production industry, recovery processes are used to generate steam and to recover certain chemicals used in the pulping process.
Other advantages of the present invention include but are not limited to the following. What is claimed is: 1. A method for producing a product gas, comprising the steps of: introducing a residual waste liquor into at least one fluidizing bed of a gasifier reactor;.
Black Liquor Gasification
A method for producing a product gas as recited in claim 1, wherein the introducing step comprises the steps of: spraying a residual waste liquor into a top of the gasifier reactor;. A method as recited in claim 1, further comprising the step of reheating the product gas after the spraying step to facilitate transport and combustion of the product gas. A method as recited in claim 1, further comprising the step of pressurizing the product gas prior to firing in a turbine.
A method as recited in claim 1, further comprising the step of providing means for pressurizing the product gas. A method as recited in claim 1, further comprising the steps of providing polishing means downstream from and connected to the second condensing heat exchanger means for scrubbing the product gas exiting the second condensing heat exchanger means in a counter current gas liquid contacting manner in the polishing means.
A method as recited in claim 6, further comprising the step of spraying reagent into an exit of the polishing means. A method as recited in claim 1, wherein the heating step includes the at least one fluidizing bed of the gasifier reactor comprising a first and a second fluidizing bed, the second fluidizing bed being positioned beneath the first fluidizing bed in the gasifier reactor and supplying a heated fluid stream thereto for simultaneously heating and fluidizing the first fluidizing bed.
A method as recited in claim 8, further comprising the step of supplying a member selected from the group consisting of an oxygen source, a malodorous gas source, air, steam, and mixture thereof to the second fluidizing bed to achieve a high Btu efficient product gas.
USA true USA Division USA en. JPB2 en. CNA en. BRA en. CZA3 en. DEA1 en. ESB1 en.
Methanol production via black liquor gasification with expanded raw material base
RUC1 en. SKA3 en. TWB en. Plant for treating refuse by pyrolysis and for producing energy by means of said treatment. The combustion of the organic material and recovery of the chemicals are accomplished in a black liquor recovery boiler, but there are many shortcomings to this approach.
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These boilers are relatively inefficient with respect to production of steam and power, have relatively high pollutant emission levels and present safety issues associated the molten salt produced in the boiler. Black liquor gasification offers an alternative to recovery boilers, and a recent publication indicated that there are energy and financial benefits to be gained by switching to gasification of black liquor. In addition to the kraft process, two less 1 frequently used pulping processes, known as the semi-chem process and the sulfite process, produce waste streams that can be gasified in the same fashion as the kraft black liquor.
The most significant difference is the sulfur content of the liquor: that from the semichem process has small or negligible amounts while liquor from the sulfite process contains about twice the sulfur of kraft liquor. These two processes are fundamentally different. In the low temperature process developed by Manufacturing and Technology Conversion International, Inc. In the high temperature gasification process developed by Chemrec AB, Stockholm, Sweden, the temperature of the process is maintained 3 well above the melting point of the salt.