GB2269388A

GB2269388A - Gasification of wastes and residues

Info

Publication number: GB2269388A
Application number: GB9305928A
Authority: GB
Inventors: Wolfgang Dipl Chem Rabe; Manfred Dipl Ing Duerlich; Lutz Dipl Ing Groeschel; Bernd Dr Rer Nat Buttker; Dieter Dipl Ing Mergemeier; Werner Dr Ing Hauptmann
Original assignee: LAUSITZER BRAUNKOHLE AG; Energiewerke Schwarze Pumpe AG
Current assignee: LAUSITZER BRAUNKOHLE AG; Energiewerke Schwarze Pumpe AG
Priority date: 1992-08-06
Filing date: 1993-03-22
Publication date: 1994-02-09
Anticipated expiration: 2013-03-22
Also published as: GB9305928D0; SK382592A3; PL298423A1; CZ280050B6; GB2269388B; FR2694566A1; PL170924B1; DE4226034C1; CZ382592A3

Abstract

A process for gasification of solid, pasty and liquid residues and waste substances, having a wide range of organic and inorganic noxious substances, comprises gasifying the residues and/or waste substances in a fixed bed pressure gasifier (1), with carboniferous condensates (15) and fine-grained ash (25) constituents from the solid bed gasification process being converted together with liquid residues eg spent oil (19), and/or waste substances in a flue current gasifier (23) and with the soot/water residue (30) from a quench (28) of the flue current gasifier (23) being returned to the fixed bed pressure gasifier (1). <IMAGE>

Description

2269388 T ITLE Gasification Process This invention relates to a process

for gasification of solid, paste or liquid residues and waste products.

Historically the least expensive method of disposing of solid waste was to deposit it in open or underground dumps. Dumps for unprocessed waste, however, cause serious problems. The ground water may easily be contaminated as a result of leaching. Valuable stretches of land are lostFires may occur.

A more advantageous method, which reduces these problems, is the sanitary filling of the ground by compositing and the covering of the waste with earth.

In large urban areas, however, this practice is proving less and less attractive, as the availability of suitable sites is continually decreasing. Both methods have been supplemented by the incineration of the refuse prior to the filling of the grounds. Although conventional incineration reduces the volume of waste and the pollution due to leaching it causes fresh environmental probleRLs such as air pollution and an increase in the, production -of contaminated residues such a5 filter dust and salt sludge although reductions of 80--- 2 90% in the volume are obtainable, the residue or ash is not always biologically inactive, so that filling of the ground is still necessary. In conventional incineration, furthermore, the recuperation of useful substances is generally minimal.

A proposed solution for the gasification of waste is provided by the Anderson method (US 3729298). In this process waste substances are introduced into the upper part and oxygen into the lower part of a vertical. shaft furnace. The process is carried out with uncompressed shredded refuse. The liquid slag occurring in the lower part is continuously run off. This method suffers from the drawback that the shredded refuse undergoes compression in the reactor, leading to ducted flow of material and to the known disadvantages of reduced performance and the danger of explosion.

DE 26 19 302 proposed the gasification of waste substances in the form of defined pellets of shredded refuse in a shaft furnace. This method can only be applied to the gasification of defined pellets at normal. pressure accompanied by the extraction of the liquid slag- DE 23 23 654 describes a process in which solid waste from household refuse As introduced into the upper part and liquid carboniferous condensates from gas 3 purification as well. as liquid waste are introduced into the lower part of the, reactor. This method suffers from the drawback than no planned transport or elimination of noxious substances is effected. The cooling of the gas to 300'C as proposed may be accompanied by a Denovo synthesis of dioxin and furans.

In a system proposed by DE 33 42 383 a suspension is gasified in a combined flue, current and a fixed bed pressure gasifier in a primary process while gasification material in lump form is gasified in a secondary process, the slag occurring being intercepted in a bath of molten sodium carbonate.

This method is used to avoid reactions between heavy metals, particularly vanadium and the brick lining.

This process suffers from the drawback that narrow limits are set to the use of solid and liquid waste and that in particular the destruction of the hydrocarbons and/or dioxin in the secondary reactor can only be incomplete.

This invention seeks to provide a method wherein liquid, pasty and solid residues and/or waste contaminated with inorganic and/or organic noxious substances can be economically utilised by a pressure gasifi.cati.on process without harm to the environment.

In accordance with this invention there is provided 4 a process for the gasification of solid, pasty or liquid residues and waste substances using parallel gasification in a solid bed pressure gasifier and in a flue current gasifier, in which process 1-80% solid or 1-60% solid and/or 1-20% pasty carboniferous residues and/or waste substances contaminated with organic and/or inorganic noxious substances are converted into useful gas in a fixed bed pressure gasifier, the time for which the residues and/or waste substances are heated in a reducing atmosphere to > 3500C and < 4000C and the time for which the residues and/or waste substances remain in the. fixed bed pressure gasifier up to direct contact with the current of crude gas generated, which has a temperature of over 3501C and which after leaving the fixed bed pressure gasifier is cooled down by a shock effect to < 20CC is longer than 1 hour, the condensates occurring in the cooling of the crude gas and dehydrated to a water content of 25% are converted in a flue current gasifier without or together with liquid carboniferous residues and waste substances contaminated with organic and/or inorganic noxious substances, into useful. gas in which process the residixes containing soot, heavy metal and salt and occurring in the gas and water preparation stages are returned preferably to the flue current gasification in the. fixed bed pressure gasifier and thc.

fine-grained ash constituents of the fixed bed pressure gasifier, in the extracts of which heavy metals may be present, are mashed together with the liquid residues which, in a proportion of 1-30% in the product with which the flue current gasifier is charged, effect scorifation of the fine-grained ash constituents of the fixed bed pressure gasifier accompanied by additional binding of heavy metal constituents of the liquid residues and/or waste substances.

According to this invention therefore, fixed bed pressure gasifiers and flue current gasifiers are operated simultaneously and in this process 180% of solid or 1-60% of solid and/or 1-20% of pasty carboniferous residues and/or waste contaminated with organic and/or inorganic noxious substances are converted in the fixed bed pressure gasifier into useful gas, the time taken to heat the residues and/or waste in a reduced atmosphere to > 3500 and < 4000C, and the time for which the residues and/or waste remain in the fixed bed pressure gasifier until direct contact occurs with the resulting current of crude gas, which is at a temperature of > 3500C and which after leaving the fixed bed pressure gasifier is cooled down suddenly to < 2000C, amounts to longer than 1 hour.

The solid and/or pasty residues and/or waste 6 comprise for example contaminated earth, plastic waste, wood, rubber products, oleaginous solid waste, residues of medical drugs, tar residues, dye product sludge or clarification sludge in fine-grained lumpy, pasty or agglomerated form which may be contaminated, for example, with aliphatic, aromatic or chlorinated hydrocarbon residues, polychlorinated biphenyls, dioxi.ns, furans, sulphur compounds and heavy metals.

In the fixed bed pressure gasifier volatile organic compounds are separated which occur as hydrocarbon fractions in the cooling of the crude gas in the closed system.

PCB's, dioxin and furans are completely destroyed when heated up to > 12000C in the fixed bed pressure gasifier in a reducing atmosphere.

If slight quantities are removed together with the crude gas these substances are caused by the oleaginous properties and solubility in oil to enter the liquid hydrocarbons separated in the condensation.

These, either without or together with liquid residues and waste containing organic noxious substances, are converted in the flue current gasifier at > 13000 and with a time of dwell of > 3 seconds into useful gas which after leaving the flue current gasifier is suddenly cooled down to < 20CC.

7 The liquid residues or waste capable of being pumped may consist, for example, of spent oil, solvents, lacquer and paint sludge and colouring matter suspensions which contain similar noxious substances to those mentioned above.

In the lower part of the fixed bed pressure gasifier the ash occurring undergoes planed granulation at > 12000C to non-elutriable melt compositions in which the heavy metals contained in the original product used are bound as prior constituents.

Elutriable fine-grained ash constituents are mixed into the liquid residues or waste in a proportion of 1-30% and gasified in the flue gas current at 1300OCIn this process the nonvolatile heavy metals of the liquid initial materials are bound in.

Volatile heavy metals enter the aqueous phase and are separated on a priority basis as sulphide, hydroxide, oxides and carbonates- This part is separated with the resulting bio-sludge in the soot water preparation and also in the subsequent biological preparation of the process water and returned to the solid bed pressure gasification to bound into the slag- In the total. process the sulphur constituents are separated from the current of gas by known methods and 8 obtained as useful material.

The method proposed provides a means of ensuring the complex utilisation, without harm to the environment, of solid, pasty and liquid residues or waste. The synergistic effects and combination effects ensure utilisation almost free of residue and with a high degree of efficiency in the conversion of the substance. The cleavage gas generated can be transported or stored as an energy carrying substance or else directly converted into raw materials for the chemical industry.

An embodiment by way of example is illustrated in the drawing and described in detail hereafter.

A fixed bed pressure gasifier 1, operated at a pressure of 25 bar, is fed with t of brown coal briquettes 2.

3 t of contaminated earth 3 with a hydrocarbon content of 5%, a dioxin content of 2000 ng/kg and 800 mg Chromium/kg, 800 mg lead/kg and 600 Cu/kg-..

3 t plastic waste 3.

3 t oil-contaminated wood 3_ 0.5 t residues from the preparation of process water 34.

Through the rotary grate 4 a mixture 5 of 2400 J i.N-oxygen/h and 15.6 t gasification vapour/h is 9 introduced into the fixed bed pressure gasifier 1. An ash/slag mixture 6 is fed to a sorting device of a known design also through the said rotary grate 4.

In this case if fine-grained elutriable ash 25 occurs, this can be separated and conveyed to a mixing device 24 for scorification in the flue current gasifier. The resulting slag granulate 36 of the fixed bed pressure and flue current gasifier can be utilised as a filling material or building aggregate.

In the solid bed pressure gasifier the hydrocarbons in the contaminated earth and in the mature wood are distilled off. The dioxin contained in the contaminated earth is destroyed in the fixed bed pressure gasifier in a reducing atmosphere at 300-800OC- If slight quantities find their way into the hydrocarbon fraction of the condensates 17 then the final conversion takes place in the flue current gasifier 23.

The plastic waste 3 contained in the mixture from the gasification in the fixed bed pressure gasifier is converted to the extent of 50-70% into gaseous constituents and to the extent of 20-50% into hydrocarbons. 2-5% goes to the ash/slag fraction 6.

The hydrocarbon parts of the mature timber used and also those of the contaminated earth used are distilled off, split up or converted into gas. The mature wood 3 - in itself is gasified and the residual constituents of the earth with a heavy metal content become a nonelutriable constituent of the ash/slag fraction 6.

The organic constituents of the residues from the preparation of process water 3 are converted into useful gas, while the inorganic constituents are melted into the ash/slag mixture 6.

Through the receptacle 7 for crude gas 19700 J i.N_ dry crude gas/h with an oil and tar content of 8OgM3 i.N. and 0.7 kg water vapour/m3 i.N- are conveyed into the washing cooler 9 through the crude gas outlet 8The quenched crude gas 11 is cooled down indirectly to ambient temperature in subsequent coolers 12 my means of cooling water 13. The cooled crude gas 14 reaches conventional gas purification plant and is then utilised as such or for energy purposes- The resulting condensates 15 are separated in a process water preparation stage 16 into a process water fraction 31 and a hydrocarbon fraction 17.

Approximately 1.58 t of hydrocarbons 17 via a pump 18, together with 12 t of spent oil 19 which is mixed in a mixing device 24 with 1-3 t of fine ash/h from the solid bed pressure gasification 25 and additionally with 10500 M3 j..N- oxygen/h 20 and 6.8 t high pressure steam/h 21 are converted into cleavage gas via the burner 22 in the flue current gasifier at 23-25 bar and 13500C.

The quantity of cleavage gas 26 of 45000 J i-N/h is cooled down with 60 t/h of quenching water 27 to 1950C, the cooled cleavage gas from the quenching chamber being utilised as such or for energy purposes via cooling and purification stages. The resulting granulate 36 contains non-elutriable heavy metal constituents of the ash used and also of the spent oil used and can be utilised in the building industry. The resulting soot water 30 is introduced together with the process water 31 into a process and soot water preparation stage unit 32 which consists of various process stages such as dephenolization, soot filtration and a biological purification stage- The resulting soot and bio-sludge residue 34 is returned to the fixed bed pressure gasifier 1, and the purified process water can be re-used or discharged into an outfall.

In the drawings the reference numerals identify the following component parts:

1. Fixed bed pressure gasifier 2. Brown coal briquettes 3. Solid waste and residues 4. Rotary grate 5. Mixture of gasification media 6. Mixture of ash and slag 12 - 7. Receptacle for crude gas 8. Outlet for crude gas 9. Washing cooler 10. Washing unit 11. Quenched crude gas 12. Cooler 13. Cooling medium 14. Cooled crude gas 15. Gas condensate 16. Preparation of process water 17. Hydrocarbon fraction 18. Centrifugal pump 19. Spent oil 20. Oxygen 21. Steam 22. Burner 23 Flue current gasifier 24. Mixing device 25. Fine-grained ash 26. Cleavage gas 27. Quenching water 28. Quenching chamber 29. Cooled cleavage gas 30. Soot water 31. Process water - 1 11 32. Preparation of process water and soot water 33. Purified waste water 34. Solid or pasty residue 35. Sorting device 36. Slag granulate.

14

Claims

1. Process for the gasification of solid, pasty or liquid residues and waste substances using parallel gasification in a solid bed pressure gasifier and in a flue current gasifier, in which process 1-80% solid or 160% solid and/or 1-20% pasty carboniferous residues and/or waste substances contaminated with organic and/or inorganic noxious substances are converted into useful gas in a fixed bed pressure gasifier, the time for which the residues and/or waste substances are heated in a reducing atmosphere to > 3500C and < 4000C and the time for which the residues and/or waste substances remain in the fixed bed pressure gasifier up to direct contact with the current of crude gas generated, which has a temperature of over 3500C and which after leaving the fixed bed pressure gasifier is cooled down by a shock effect to < 2000C is longer than 1 hour, the condensates occurring in the cooling of the crude gas and dehydrated to a water content of 25% are converted in a flue current gasifier without or together with liquid carboniferous residues and waste substances contaminated with organic and/or inorganic noxious substances, into useful gas in which process the residues containing soot, heavy metal and salt and occurring in the gas and water preparation stages are returned preferably to the flue current gasification in the fixed bed pressure gasifier and the fine-grained ash constituents of the fixed bed pressure gasifier, in the extracts of which heavy metals may be present, are mashed together with the liquid residues which, in a proportion of 1-30% in the product with which the flue current gasifier is charged, effect scorifation of the fine-grained ash constituents of the, fixed bed pressure gasifier accompanied by additional binding of heavy metal constituents of the liquid residues and/or waste substances.

2. Process for the gasification of waste substances substantially as described herein and exemplified.

3. Apparatus for carrying out the process of either preceding claim as described herein and exemplified with reference to the drawings.

1