WO2005097685A1

WO2005097685A1 - Method for treatment of dangerous waste in liquid state and a plant to carry through the method

Info

Publication number: WO2005097685A1
Application number: PCT/SE2005/000337
Authority: WO
Inventors: Dennis Sogaard
Original assignee: Stena Miljöteknik Ab
Priority date: 2004-04-08
Filing date: 2005-03-09
Publication date: 2005-10-20
Also published as: SE0400938L; EP1732849A1; SE0400938D0; SE528087C2

Abstract

The invention relates to a method for the treatment of hazardous waste (1) in liquid form and in pastey form in a distillation plant (2) in the form of a heated horizontal pipe with an internal screw conveyor. In accordance with the invention, the thermal energy obtained in conjunction with the distillation is utilized in order to perform the distillation, whereby no thermal energy other than the organic content of the waste requires to be added apart from at the start-up of the aforementioned process for the distillation of the waste that contains water. The invention also relates to a plant that is suitable for the implementation of the method.

Description

Method for treatment of dangerous waste in liquid state and a plant to carry through the method

The present invention relates to a method for the treatment of hazardous waste in liquid form and in pastey form in a distillation plant in the form of a heated horizontal pipe with an internal screw conveyor. Energy is normally supplied continuously in the treatment of hazardous waste when it is wished to bring about distillati_on of waste in liquid form and in pastey form. US Al 4338199 is based on the oxidation of hydrocarbons in water under supercritical conditions, where the pressure must be at least 220 atm and the temperature must be at least 377 °C, and the oxidation takes place in the water. A great deal of energy is used in order to achieve the high temperatures and pressures under supercritical conditions. Waste that could compensate for all the supplied energy cannot be added to suchi a plant, however, as this would cause the process to become unstable . EP Al 0607 644 is based on partial oxidation in a gasification plant. The gasification process involves the introduction of oxygen in fairly small quantities at high temperature in order to take advantage of the heat content of the waste through oxidation in conjunction with heating. It is also based on the dewatering of digester sludge (mainly water and a little organic/inorganic material) by thermal and mechanical methods in order to produce a fuel from the digester sludge. GB B 2351283 is based on mixing the waste with a reactive chemical, in this case burnt line (CaO) . The reaction between the CaO and water and hydrocarbons produces an increase in the temperature of the waste, in conjunction with which the water evaporates and the hydrocarbons are broken down (oxidized) . The principal object of the present invention is thus to make available a method that is self-sufficient with regard to the consumption of energy in conjunction with the performance of the distillation of hazardous waste that is in liquid form or in pastey form, and in which no waste is produced that requires disposal. It is also proposed to generate a fuel in a surplus amount, which is suitable for use in other energy-intensive processes . The aforementioned object is achieved through a method in accordance with the present invention, which is characterized essentially in that the aforementioned distillation pipe is caused to be heated indirectly, in that a fuel is generated in a surplus amount in conjunction with the distillation for use in energy-intensive processes such as cement kilns, in that an industrial steam boiler with a ceramic-lined combustion chamber is used to enable the utilization of the energy content of the added waste at a combustion temperature between 850 and 1100 °C for a period greater than 2 seconds, and in that the thermal energy obtained in conjunction with the distillation is utilized in order to perform the distillation, whereby no thermal energy other than the organic content of the waste requires to be added apart from at the start-up of the aforementioned process for the distillation of the waste that contains water. Our assumptions are normal atmospheric pressure (1 atm) ,

100°C in conjunction with distillation (gasification and cleaning and 850 °C in conjunction with combustion in air). Entirely different plants are used for oxidation under supercritical conditions and for oxidation by combustion. A process in accordance with US Al 4338199 is operated under entirely different conditions than the process intended in accordance with the invention. As described in the present patent application, no gasification takes place, and steam is used to warm the waste indirectly in order to cause solvents and other volatile substances to be driven off in the gaseous phase. The oxidation in the present process is performed at an entirely different stage (intensive combustion chamber) . The aforementioned patent does not contain any process stage that resembles the technique in accordance with that covered by the patent application. In the present plant, no reactive chemicals will be used to oxidize the waste. Oxidation in the present case takes place in an intensive combustion chamber. The invention also relates to a plant for use in the implementation of a method for the treatment of hazardous waste in liquid form and in pastey orm in a distillation plant in the form of a heated horizontal pipe with an internal screw conveyor. The purpose of this is also to solve the problem of finding a plant which can utilize the energy content in the material that it processes in order to drive the process that is performed in the plant. The aforementioned additional object is achieved by means of a plant in accordance with the present invention, which is characterized essentially in that the plant also comprises an industrial steam boiler in order to achieve indirect heating of the waste in the distillation pipe, and in that fuel for the aforementioned steam boiler comes mainly from the waste in the distillation pipe. The invention is described below as a preferred illustrative embodiment, in conjunction with which reference is made to the accompanying drawings, in which Fig. 1 shows a schematic principle drawing of the plant for the implementation of a method in accordance with the invention, and Fig. 2 shows an enlargement of a principal part of the invention shown in Fig. 1. A method in accordance with the present invention for treating hazardous waste 1 in liquid form and/or in pastey form in a distillation plant 2, which is in the form of a heated horizontal pipe provided with an internal screw conveyor, involves utilizing the thermal energy that is obtained in conjunction with the aforementioned distillation in order to perform the distillation. No thermal energy other than the organic content of the aforementioned waste needs to be supplied for this purpose, except in conjunction with the actual start-up of the aforementioned process for distilling the waste that contains water. The gas released from the pastey/solid hazardous waste in the course of treatment in the screw conveyor contains energy- rich solvents. After condensation, this liquid is used in the intensive combustion chamber in order in turn to produce steam in a steam boiler, which condenses on the outside of the pipe containing the screw conveyor. A screw conveyor with the ability to do this with hazardous waste, which, among other things contains solvents, does not exist. The aforementioned distillation pipe 2 is caused to heat up indirectly. The idea is based on a closed process, in which "waste" from one part of the process is used internally in the next part. The water content is preferably caused to reduce in waste with an even higher water content than the waste that is fed into the distillation pipe 2, by causing it to pass through a circulating evaporation plant 3 before the waste that has been ewatered in this way is then supplied, to the aforementioned distillation plant 2. The unique feature of this process is the combination 1-3, which means that waste with a high water content is first treated semi-continuously in the circulating evaporator, which produces a highly viscous residue that is then pumped to the distillation plant. If the waste is highly viscous, on the other hand, it is supplied directly to the distillation plant, after which the condensed steam is treated in the circulating evaporator. An attempt is made to describe the process in Fig. 1. A combustion chamber which, together with an industrial steam boiler, satisfies the requirements of "Directive 2000/76/EC on incineration of waste" in respect of both the retention time and the temperature, which stipulates that the fuel must have been distilled in accordance with the foregoing, is unique. The Directive on the incineration of waste has been adopted into Swedish legislation since 2005. The aforementioned evaporation plant 3 is operated continuously or in batches, and the water content is brought down from ca 90% to ca 70%, so that the volume of waste in the outgoing waste is reduced in this way to ca one third. A fuel is generated in a surplus amount in conjunction with distillation, and this fuel is intended to be used in energy-intensive processes, such as cement kilns. In order to be able to utilize the energy content of the incoming waste and to achieve complete combustion, a ceramic- lined combustion chamber is used at a temperature between 1000 and 1100 °C for a period of at least 2 seconds in order to permit the flue gases to be used to produce the steam that is required for the various parts of the plant. Steam and/or water are also injected into the combustion chamber in order to achieve optimal, or at least more efficient combustion. The combustion of distilled hazardous waste in an incinerator in which steam and/or water are used with the help of compressed air for the purpose of atomizing the fuel means that carbon, which could coat the heat exchanger surfaces in the steam boiler, also forms "oxygen" (CO + H₂) together with the water. The surplus of oxygen in the air is used in the next stage to form carbon dioxide and water. A plant 5, which is suitable for use fox the implementation of a process in accordance with the present invention for the treatment of hazardous waste or some other product in liquid form and in pastey form in a distillation plant 2 in the form of a heated horizontal pipe with an internal screw conveyor, also comprises an industrial steam boiler 4 in order to achieve indirect heating of the waste in the distillation pipe 2. Fuel to drive the aforementioned steam boiler 4 comes mainly from the waste in the distillation pipe 2. The combustion chamber of the aforementioned industrial steam boiler is thus lined with a ceramic material, and nozzles are arranged for injecting steam and/or water into the combustion chamber. A circulating evaporation plant 3 is preferably included in the plant 5 as a whole, and this is so arranged as to be capable of reducing the water content of waste 1 in liquid form, which exhibits a high water content, before the waste is supplied to the aforementioned distillation plant 2. The entire plant 5, which is illustrated schematically in the drawings, can consist of a number of interconnected process stages . The entire plant 5 can thus comprise desired parts of the following units: - Circulating evaporation plant 3 - Distillation plant 2 - Separation plant 6 - Steam boiler with intensive combustion chamber 4 - Flue gas cleaner 7 - Azeotropic distiller 18 - Powerfuel processor 19

The function of the aforementioned parts is as follows : The circulating evaporation plant 3 is intended for waste in liquid form with a high water content and is capable of being operated continuously and in batches. It normally reduces the water content of the waste that is fed in from ca 90% to ca 70%, in conjunction with which the volume of waste is reduced to about one third of the quantity that is fed in. The distillation plant 2, which is in the form of an indirectly heated horizontal pipe 2 with an internal screw conveyor, althoug-h this is not shown in the drawings but is well known in the field of conveyor engineering, is intended for the treatment of waste both in liquid form and in pastey form. The plant can be operated continuously or in batches. After heating the waste therein, mainly water and solvents are driven off, which, after gravimetric separation as required, can also be treated in the distillation plant 2. The separation plant 6 is used to enable the water to be separated from tb-e solvent by utilizing the higher vapour pressure that exists in the solvent. The steam boiler with the intensive combustion chamber 4 consists of a conventional industrial steam boiler with a built- on ceramic-lined combustion chamber to enable the energy to be extracted from the energy content of the waste that is introduced. Combustion, which takes place at 1000-1100 °C, with a retention time of more than 2 seconds, can also deal with fuels with thermal values of < 16 MJ/kg. Steam and/or water can be injected into the combustion chamber in order to achieve optimal combustion. The flue gas cleaner 7 is formed by a horizontal vortex chamber for the separation primarily of dust and acid components from the flue gases. The water content of the waste in this case can be utilized in the flue gas cleaning plant 7 to cool and neutralize the flue gases 8. Since most of the condensed water from the distillation plant 2 has been used in the flue gas cleaning process to cool and neutralize the flue gases, any water remaining in the waste exits from the plant as steam. The azeotropic distiller 18 can be used to distil different mixtures of liquids which form azeotropes, with the primary purpose of removing organic compounds with a low flash point that could otherwise obstruct the continued use primarily of the fuel. The Powerfuel processor 19 homogenizes the fuel respectively for internal and external us e through high-speed mixing. In the entire plant, the various arrows between the units denote the following: waste 1 is conveyed into the distiller 3, which is designed for low-viscosity fluids, and dewatered waste l¹ is conveyed onwards from there to the main distiller 2, which is intended for viscous fluids. The discharged product is indicated by the designation 9. Hazardous waste fuel 10 is supplied to a designated steam boiler 4, and heat in the form of steam 11 is conveyed from there to the evaporation plant 3, the azeotropic distiller 18 and respectively to the distiller 2. In addition, the designation 12 is used for organic solvents, 13 for fuels, 14 for oil-based waste, 15 for water for cooling of the flue gas cleaning process 7, 16 for water from the distiller 2, and 17 for the recipient. The plant 5 is suitable for operation both continuously or for a limited period, for example during the daytime, although the plant does not produce any hazardous waste that requires dumping. Other advantages of the invention are that it is now possible to treat different types of hazardous waste in liquid form and in pastey form, and that a fuel (HC fuel or Powerfuel) is generated in a surplus quantity that can be used in other energy-intensive processes (such as cement kilns) . No additional source of thermal energy is required, furthermore, other than the organic content of the waste, in order to distil waste that contains water , and by converting the combustible fraction of the waste that contains water into energy in the plant, the energy-intensive process of distilling water can be performed without the addition of external thermal energy. The invention is subject to certain restrictions, however, and it does not propose to solve all the problems in the waste area. The plant is thus not intended or dimensioned for the treatment of waste with high levels of halogens (chlorine, bromine or fluorine) or with high levels of mercury. The plant is also not so arranged as to make it suitable for application to solid hazardous waste. The invention should have been clearly- appreciated from what is stated above and from what is illustrated in the drawings, and the invention is naturally not restricted to the embodiment described above and illustrated in the accompanying drawings. Modifications are possible, in particular with regard to the nature of the various parts, or by the mse of equivalent technology, but without departing from the area of protection afforded to the invention, as defined in the Patent Claims. No such method or no such plant as defined in the Patent Claims is evident, either individually or in combination, and what is stated in the foregoing also cannot be regarded as obvious to a person skilled in the art inter alia for the reason that are outlined above.

Claims

S212 P1PCT LG/KOEP a t e n t C l a i m s

1. A method for the treatment of hazardous waste (1) in liquid form and in pastey form in a distillation plant (2) in the form of a heated horizontal pipe with an internal screw conveyor, characterized in that the aforementioned distillation pipe is caused to be heated indirectly, in that a fuel is generated in a surplus amount in conjunction with the distillation for use in energy-intensive processes such as cement kilns, in that an industrial steam boiler (4) with a ceramic-lined combustion chamber is used to enable the utilization of the energy content of the added waste at a combustion temperature between 850 and 1100 °C for a period greater than 2 seconds, and in that the thermal energy obtained in conjunction with the distillation is utilized in order to perform the distillation, whereby no thermal energy other than the organic content of the waste requires to be added apart from at the start-up of the aforementioned process for the distillation of the waste that contains water.

2. A method as claimed in Patent Claim 1, characterized in that the water content of the waste in liquid form, which exhibits a high water content, is reduced, by causing it to pass through a circulating evaporation plant (3) before the waste is supplied to the distillation plant (2) .

3. A method as claimed in Patent Claim 2, characterized in that the aforementioned evaporation plant (3) is operated continuously or in batches, and in that the water content is brought down from ca 90% to ca 70%, so thtat the volume of waste is reduced in this way to ca one third.

4. A method as claimed in one or other of the above Patent Claims, characterized in that steam and/or water are also injected into the combustion chamber in order to achieve optimal, or at least more efficient combustion.

5. A plant (5) to be used to implement a method for the treatment of hazardous waste in liquid form and in pastey form in a distillation plant (2) in the form of a heated horizontal pipe with an internal screw conveyor, as claimed in one or other of Patent Claims 1-4, characterized in that the plant also comprises an industrial steam boiler (4) in order to achieve indirect heating of the waste in the distillation pipe (2), and in that fuel for the aforementioned steam boiler (4) comes mainly from the waste in the distillation pipe (2) .

6. A plant as claimed in Patent Claim 5, characterized in that the combustion chamber of the aforementioned industrial steam boiler is lined with a ceramic material,, and in that nozzles are arranged for injecting steam and/or water into the combustion chamber.

7. A plant as claimed in one or other of Patent Claims 5-6, characterized in that a circulating evaporation plant (3) is included in the plant (5) so as to be capable of reducing the water content of waste (1) in liquid form, which exhibits a high water content, before the waste is supplied to the aforementioned distillation plant (2).