Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23G—CREMATION FURNACES; CONSUMING WASTE PRODUCTS BY COMBUSTION
  • F23G5/00—Incineration of waste; Incinerator constructions; Details, accessories or control therefor
  • F23G5/08—Incineration of waste; Incinerator constructions; Details, accessories or control therefor having supplementary heating
  • F23G5/14—Incineration of waste; Incinerator constructions; Details, accessories or control therefor having supplementary heating including secondary combustion
  • F23G5/16—Incineration of waste; Incinerator constructions; Details, accessories or control therefor having supplementary heating including secondary combustion in a separate combustion chamber
  • F23G5/165—Incineration of waste; Incinerator constructions; Details, accessories or control therefor having supplementary heating including secondary combustion in a separate combustion chamber arranged at a different level
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23G—CREMATION FURNACES; CONSUMING WASTE PRODUCTS BY COMBUSTION
  • F23G5/00—Incineration of waste; Incinerator constructions; Details, accessories or control therefor
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F22—STEAM GENERATION
  • F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
  • F22B31/00—Modifications of boiler construction, or of tube systems, dependent on installation of combustion apparatus; Arrangements of dispositions of combustion apparatus
  • F22B31/04—Heat supply by installation of two or more combustion apparatus, e.g. of separate combustion apparatus for the boiler and the superheater respectively
  • F22B31/045—Steam generators specially adapted for burning refuse
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23G—CREMATION FURNACES; CONSUMING WASTE PRODUCTS BY COMBUSTION
  • F23G5/00—Incineration of waste; Incinerator constructions; Details, accessories or control therefor
  • F23G5/44—Details; Accessories
  • F23G5/46—Recuperation of heat
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23G—CREMATION FURNACES; CONSUMING WASTE PRODUCTS BY COMBUSTION
  • F23G2206/00—Waste heat recuperation
  • F23G2206/20—Waste heat recuperation using the heat in association with another installation
  • F23G2206/203—Waste heat recuperation using the heat in association with another installation with a power/heat generating installation
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E20/00—Combustion technologies with mitigation potential
  • Y02E20/12—Heat utilisation in combustion or incineration of waste

Definitions

• the present invention relates to a method of treating solid material such as wastes and biological sludges at a high temperature and of recovering heat from said process as we. crizl as of cooling generated process gases.
• FI patent 86471 suggests that a fluidized bed boiler were used in connection with the treatment of wastes, in which boiler the incineration fraction being generated in a separate waste pretreatment is incinerated.
• the biological fraction being generated in the same pretreatment forms biogas as a result of the treatment, which is suggested to be used for the increase of temperature in the flue gas channel subsequent to the fluidized bed boiler.
• According to said patent by performing this afterburning it is possible to decrease the generation of polyaromatic hydrocarbons harmful to the environment.
• the described afterburning is carried out, as also the superheating of steam in the flue gas channel subsequent to the combustion chamber.
• the incinerat-, _>n of wastes may be carried out also as grate incineration.
• This is an advantageous method, since it is possible to incinerate untreated waste on the grate.
• the pretreatment of waste is often a complicated multistage process, whereby the complete elimination thereof brings a significant advantage to the grate incineration compared with the economy of the fluidized bed incineration.
• the temperature may be raised to even 1200°C, thus ensuring an efficient incineration.
• the superheating temperature of steam may not be raised above about 400°C, more precisely 300- 420°C, by grate incineration alone, since the corrosion of superheating surfaces would increase excessively and the operational safety of the plant would substantially decrease.
• the purpose of the present invention is to provide a simple, efficient method of treating waste and other solid material at high temperatures, which is easy to use and in which the generated heat is mainly used for steam production.
• the purpose of the present invention is also to provide a method of recovering heat in connection with grate inceneration of waste, in which a higher temperature of the superheated steam is achieved than in those according to the prior art.
• the purpose of the present invention is to provide a method of treating waste at high temperatures by incinerating them on a grate, whereby generated heat is recovered as superheated steam and in which method, the efficiency of the electricity production of the plant, when used for electricity production gained is higher than that of the prior art.
• wastes may be treated at a high temperature by grate incineration, whereby a complicated waste pretreatment process is unnecessary, but substantially untreated waste may be incinerated and the generated heat may be used for the production of high temperature superheated steam and this again may be further used, for example, for the generation of electricity.
• said method comprises at least the following steps of: feeding substantially unpretreated solid material to the incineration chamber for treating solid material at a high temperature; heating or incinerating solid material at the presence of oxygen-containing gas at the temperature of > 1000°C; supplying circulating material into communication with the generated flue gases in such a way that gases and the circulating material are efficiently intermixed; passing the mixture of gases and circulating material further in the process simultaneously recovering heat therefrom; separating circulating material from the gases; passing the gases for further treatment; and passing the circulating material separated from the gases to the cooling process, in which the heat of the circulating material is used for the increase of the temperature of the steam generated in the grate incineration apparatus.
• wastes such as municipal waste is incinerated by grate incineration
• wastes may be incinerated substantially non- sorted without any pretreatment.
• the generated process gases may be, if desired, heated to a temperature of more than 1000°C, even more than 1200°C, for example, for destroying compounds harmful to the environment, such as chlorined hydrocarbons.
• the process gases generated in the grate incineration are brought into contact with the circulating material which absorbs at least a portion of the heat of the flue gases simultaneously warming up.
• the circulating material brought into contact with the gases and the gases are efficiently intermixed and pass into a separator, which is preferably a cyclone separator. At least a portion of the solid material is separated from the gas and from said separated portion further at least a portion is led to the cooling process of the circulating material which takes place in a cooler, preferably a fluidized bed cooler. One portion of the separated circulating material may be led, if desired, directly back to the process and be brought into communication with the gases generated in the grate incineration. Also yet another portion of the separated circulating material may be completely removed from the process.
• the separator of the circulating material is preferably a cyclone separator, in which a very efficient gas vortex is generated.
• Heat exchange means are provided in the cooler of the circulating material preferably for superheating steam.
• the steam to be superheated is preferably generated by steam generation means arranged into connection with the grate incineration apparatus.
• the steam to be led to the heat exchange means of the cooler may already be presuperheated or also saturated steam.
• heat surfaces for intermediate superheating steam may be located, if required, to the cooler, if the plant is, for example, combined to a two-stage steam turbine.
• the circulating material cools down superheating the steam flowing in the heat exchange means.
• the cooler of the circulating material when the cooler of the circulating material is a fluidized bed type cooler, it is possible to supply fluidizing gas of the circulating material to the cooler, so that the heat exchange means arranged to operate as a superheater of steam are in a heat exchange contact with the circulating material.
• the heat in the circulating material may be recovered in the form of high temperature superheated steam of more than 420°C without a significant corrosion risk in the superheating surfaces.
• the fluidizing gas to be led to the cooler of the circulating material may be led from the fluidized bed cooler, for example, back to the furnace shaft or to the vicinity of the grate to act as primary, secondary or tertiary air in the waste incineration.
• the cooled circulating material is supplied either back into communication with the gases generated in the grate incineration or then it may be either completely or partially removed from the process.
• a substantial improvement over the prior art technique is that by utilizing the method in accordance with the present invention it is possible to incinerate unpretreated waste by grate incineration and simultaneously to generate superheated steam, the superheating temperature of which may be raised higher than with the methods in accordance with the prior art.
• the steam temperature may be raised even to 420-550°C, preferably to 500-550°C, without any corrosion risk in the superheating surfaces. By this arrangement it is possible to significantly raise the temperature of the superheated steam compared with the prior art technique.
• the cooler of the circulating material By utilizing the cooler of the circulating material it is possible to cool the circulating material, thus also simultaneously to superheat the steam, outside the actual process beyond the re ch of corroding flue gases generated in the grate incineration, whereby the conditions prevailing in the external treatment apparatus do not depend on the conditions of the actual waste treatment process, whereby the superheating temperature of the steam may be raised above 420°C, even to the temperature of 420-550°C, preferably to 500-550°C, because the corroding substances being released in the waste treatment, such as chlorine, are not present.
• the cooler which is preferably a fluidized bed cooler, it is possible to choose a non-corroding substance to act as fluidizing gas.
• Possible fluidizing gases are, for example, inert gas, such as nitrogen, or if required also oxygen gas may be used as fluidizing gas. Air, however, is preferably used as a fluidizing gas.
• inert gas such as nitrogen
• oxygen gas may be used as fluidizing gas.
• Air is preferably used as a fluidizing gas.
• the temperature of steam to be superheated with circulating material may be raised high in this way without a risk of corroding heat surfaces, for example, due to chlorine.
• the gases from the separator of the circulating material are supplied to the further treatment, which may comprise according to a first embodiment cooling of the gas in the waste heat boiler in accordance with the prior art, to ⁇ which heat surfaces are arranged for heating or steaming of the medium. Further treatment may also comprise cooling of gas in a fluidized bed reactor according to a second embodiment of a method in accordance with the present invention.
• the circulating material to be used may contain one or more of the following substances: a substantially inert solid material, a substance binding sulphurous oxides, a catalyte disperging oxides of nitrogen.
• Fig 1 schematically illustrates an apparatus for realizing the method in accordance with the present invention.
• Fig. 1 illustrates a waste incineration plant 1.
• the unpretreated waste is preferably introduced into a furnace 2 of the incinerator in the incineration plant through an opening 3.
• the waste flow along a grate 4 to the lower part of the furnace and incinerate forming flue gases.
• Air is supplied through the grate to the furnace.
• the flue gases rise upwards in a furnace shaft 5, to which, if desired, for example, additional burners may be mounted to ensure a complete incineration and/or the dispersion of substances harmful to the environment.
• additional air may be brought to the furnace shaft, such as secondary air so that the incineration in the furnace shaft 5 takes place by staged air supply, whereby the amount of oxygen may be efficiently optimized in view of the incineration.
• the furnace shaft is preferably formed of a wall construction which may be cooled, such as a so called membrane wall, which is preferably lined, for example, by silicon carbide lining.
• the furnace shaft is provided within a distance from the grate with means 6, 17, by means of which circulating material is brought into contact with gases being •released from the grate incineration so that the gases and the circulating material are efficiently intermixed and heat exchange takes place between the gases and the circulating material cooling the gas and heating the circulating material. Also material exchange may take place.
• Members 17 comprise according to the invention means for facilitating the maintenance of the suspension formed of the circulation material, preferably comprising at least the zone of the furnace shaft, in which the cross-sectional flow area is decreased.
• An efficient mixing may be provided by arranging a spouted bed of circulating material above the construction.
• the mixture of gases and circulating material flows upwards in the furnace shaft and simultaneously it may release heat for evaporating the medium flowing on the wall of the furnace shaft. For the sake of clarity this has, however, not been illustrated in the drawing.
• the upper portion of the furnace shaft is connected to the separator 7, in which solid material is separated from the gases.
• the separator of the circulating material is preferably a cyclone separator, in which a very efficient gas vortex is generated.
• the air supply to the incineration grate and furnace shaft may be adjusted to very close to the stoichiometric value, because due to the efficient mixing of the cyclone the unburnt material of the gases, mostly carbon monoxide, efficiently comes into contact with the unreacted oxygen and thus it is possible, due to the accurate adjustment of the combustion air to decrease unnecessary emissions caused by the nitrogen in the air and at the same time hardly any unburnt oxygen remains in the gases.
• the complete incineration taking place due to said efficient mixing it is possible to shorten the furnace shaft subsequent to the furnace, because the separator subsequent to the shaft ensures an efficient, complete incineration.
• the circulating material separated from the gases in the separator, or at least a portion thereof, is introduced into a cooling apparatus 8 via a channel 10.
• One portion of the separated circulating material may be supplied, if required directly back into contact with the gases generated in the grate incineration through a channel 9.
• Said transfer path of the circulating material is schematically illustrated as a separate channel, but it may also be an integrated portion of the cooling apparatus. Additionally, one portion of the separated circulating material may be completely removed from the process. Said flow of the circulating material is not illustrated in the drawing, but the circulating material may be removed from the desired place, preferably after it has cooled down in the cooling apparatus 8.
• Heat exchange means 11 are provided in the cooler of the cooling apparatus, said heat exchange means being provided with conduits 14, 15 for introducing steam and further for the discharge thereof. Saturated steam is preferably introduced into heat exchange means for superheating it, but in some cases also reheating of already superheated steam may come into question.
• the circulating material led thereto in the cooler cools the steam flowing in the heat exchange means while it is superheated to a temperature of above 420°C, preferably 500-550°C. At least a portion of the cooled circulating material is led back to the furnace shaft into contact with the gases generated in the furnace incineration by means of means 12 and 6. A portion of the circulating material may also be removed from the process. Additionally, fluidizing gas is supplied by means of means 13 to the cooling apparatus, which is preferably a fluidized bed cooler. Fluidizing gas may be led from the fluidized bed cooler, for example, to the back to the furnace shaft along channel 16 to the vicinity of the grate to operate as primary, secondary or tertiary air in the waste incineration.
• means 6 and 12 as well as 9 and 10 may as well be means integrated in the cooling apparatus or furnace shaft and they do not have to be separate, as is illustrated for clarity in Fig. 1. Additionally, the whole cooling apparatus may be integrated in the grate incineration furnace.
• the method in accordance with the present invention is compared in the following by means of examples with the arrangement in accordance with prior art.
• the heat being released from the gases is used for the generation of superheated steam when the superheating surfaces are covered, according to the invention, from the untreated process gases containing corroding substances.
• the superheated steam is used in a conventional steam turbine process in the same way as in a condense power plant to generate only electricity .(Example 1) or as a district heating plant for a combined generation of electricity and heat (Example 2) .
• Case A illustrates waste incineration in accordance with the prior art, in which steam may be superheated only to a temperature of about 420°C and this is compared with Case B, in which in a process in accordance with the present invention it is possible to raise the superheating temperature of steam, for example, to 520°C.
• Example 2 Combined electricity and district heat production.
• the cases of the example correspond to the cases of Example 1.
• the process values are given in Table 2.
• the beneficial method of treating waste in accordance with the present invention is significantly more efficient and advantageous than the methods of the prior art.
• the method in accordance with the present invention offers an especially advantageous solution in cases where the steam turbine may be chosen to endure superheating temperatures of the steam to be generated by the method in accordance •with the present invention, in other words in new waste treatment plants, or in cases where the already existing turbine allows the use at temperatures above 420°C.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Treatment Of Sludge (AREA)
• Glass Compositions (AREA)
• Processing Of Solid Wastes (AREA)

Priority Applications (4)

Applications Claiming Priority (4)

Publications (1)

Family

ID=26159534

Family Applications (1)

Country Status (8)

Cited By (5)

Families Citing this family (2)

Citations (4)

• 1993
  • 1993-09-09 FI FI933961A patent/FI933961A/fi not_active Application Discontinuation
• 1994
  • 1994-06-22 CN CN94192577A patent/CN1125980A/zh active Pending
  • 1994-06-22 AU AU70745/94A patent/AU7074594A/en not_active Abandoned
  • 1994-06-22 EP EP94919687A patent/EP0705411A1/en not_active Withdrawn
  • 1994-06-22 CA CA002164981A patent/CA2164981A1/en not_active Abandoned
  • 1994-06-22 KR KR1019950705577A patent/KR960703221A/ko not_active Application Discontinuation
  • 1994-06-22 WO PCT/FI1994/000279 patent/WO1995000804A1/en not_active Application Discontinuation
• 1995
  • 1995-12-22 NO NO955252A patent/NO955252L/no unknown

Patent Citations (4)

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