WO2001092783A1

WO2001092783A1 - Method and apparatus for combustion of waste, in particular pvc-containing waste

Info

Publication number: WO2001092783A1
Application number: PCT/EP2001/006334
Authority: WO
Inventors: Ron Zevenhoven
Original assignee: Ron Zevenhoven
Priority date: 2000-06-02
Filing date: 2001-06-04
Publication date: 2001-12-06
Also published as: FI20001331A; AU2001279642A1; FI117574B; FI20001331A0

Abstract

The invention relates to a method and an apparatus for combustion of solid waste, particularly containing PVC, wherein the apparatus comprises at least one first reactor (1) for de-hydro chlorination of the waste and at least one second reactor (3, 4, 5) for combustion of the waste, at least one of said reactors being a fluidized bed reactor. The process is useful for heat and electric power generation, chlorine is recovered as HCl.

Description

Method and apparatus for combustion of waste, in particular PVC-containing waste

FIELD OF THE INVENTION

The present invention relates to a method and an apparatus for combustion of solid waste, in particular PVC-containing waste. The process is useful for heat and electric power generation, chlorine is recovered as HC1.

DESCRIPTION OF PRIOR ART

There is a great interest in efficient use of solid waste as an energy source and possible chemical feedstock. There is a desire to conserve fossil fuel stock and waste such as municipal solid waste is inexpensive and widely available. Further, landfill disposal of municipal waste is an environmental problem because of the land wastage and the seepage of toxic decomposition products and greenhouse gases out of landfill areas. Furthermore, plastic waste particularly, contains significant reserves of energy that can be recovered through combustion processes.

Mass burning of solid waste as well as waste-to-energy processes with more emphasis on energy recovery is strongly limited by too large fractions of chlorine-containing compounds. In general, waste-derived fuels should contain less than 2 % by weight chlorine in order to avoid problems with the operation of an incinerator, combustor or' gasifϊer. Problems are related mainly to corrosion, which enforces low steam parameters, resulting in thermal efficiencies of the order of 20%. To a large extent this is related to the presence of PVC (poly vinyl chloride), a polymer that contains circa 55% chlorine (Cl). In Finland for example, PVC is responsible for more than 90% of the chlorine found in solid waste streams.

The temperature of inlet steam condition for the conventional incineration plant should be limited to below 500°C to avoid the high-temperature fireside corrosion in the superheat area, which is related to the aggressive nature of the flue gases. Thus, the low inlet steam condition to the steam turbine will decrease electricity production and thermal efficiency of the plant. In order to resist corrosion special materials are needed which increases capital and maintenance costs. Although the standard incinerators are capable of .handling municipal refuse containing plastics, they cannot usually handle waste with high contents of plastics. In order to avoid problems, the maximum amount of plastic waste that is incinerated in conventional incinerators should be about 5 % of the whole waste. Most of the conventional incinerators are not capable of supplying an adequate amount of air for complete combustion of plastics. During incomplete combustion, soot is produced which will stick to the pipe walls of the heat exchanger unit, affecting the performance. In processes designed for plastics, gas cleaning is necessary.

US Patent No. 3,716,339, relating to hydrogen chloride recovery incinerator for plastics containing hydrogen and chlorine, does not contribute to solving the problem of combustion of municipal waste and other PVC-containing wastes with high electrical efficiencies. Since the temperature for the decomposition of the plastics mixture is quite low, there is still significant chlorine in the decomposed scrap. According to the patent the scrap plastic partially decomposes in the kiln. As a result of this a water spray is needed for flue gas - cleaning. The conventional furnace used in said patent for combustion of decomposed scrap is not useful for generating electricity at a high electrical efficiency. The chlorine in the decomposed scrap is the main reason why high electrical efficiencies cannot be reached. In said patent the heat is used only to cause the partial decomposition not for generating electricity and moreover the advantages of using fluidized bed reactors do not apply.

SUMMARY OF THE INVENTION . - , -

The major object of the present invention is to supply a method and an apparatus, in which combustion of PVC-containing solid waste, which may contain otherwise problematic , chlorine, is used as an energy source. Recovery of at least energy or electricity and HC1 is possible. Thermal efficiencies of ~36 % (electric) may be reached, depending on pyrolysis or gasification temperature and the plastic content and type in the solid waste. The efficiencies are high because of the integration of the heat recovery from the combustor with the heat carrier such as sand recycling in the process.

An objective of the invention is also to supply an apparatus in which HC1 emissions from the combustor are below legislative emission limits without gas cleaning and no hot HC1- containing gases have to be handled during the process. The characteristics of fluidized bed combustion give a relatively clean combustion process, especially considering NOx.

Another object of the invention is to make use of the thermostability of PVC. Instead of solving the problem related to the removal of HCl from the flue gases by a sorbent, the waste fuel is more or less 'cleaned', in fact de-hydrochlorinated, giving a HCl gas stream and a chlorine-free waste-derived fuel that can be further combusted or sold as a chlorine free or low-chlorine waste-derived fuel as such. Although high-chlorine wastes are being treated, no high-chlorine wastes are combusted, which puts the process outside the definitions and regulations for hazardous waste incineration processes.

A further object of the invention is to supply an apparatus in which the HCl recovery from waste can be above 90%.

The objects defined above are achieved in accordance with the present invention as disclosed in the characteristic portion of the appended claims. Thus, the method according to the present invention is characterized in that solid waste is de-hydrochlorinated in at least one first reactor and de-hydrochlorinated waste is combusted in at least one second reactor and at least one of said reactors including fluidization of said waste. Accordingly the apparatus comprises at least a first reactor for de-hydrochlorination of the waste and at least a second reactor for combustion of the waste and at least one is a fluidized bed reactor.

The present invention discloses a method for production of electricity from waste and an apparatus therefore. According to the invention the system is composed of at least two reactors and at least one of said reactors is a fluidized bed reactor, preferably there are two fluidized bed reactors. However, any one of the reactors can for example be a conventional rotating kiln, preferably with a solid heat carrier. According to a favorable embodiment the de-hydrochlorination of the fuel takes places in a bed of hot heat carrier, such as sand, which is fluidized with nitrogen in the first reactor at 200 to 400°C, preferably at 300 to 400°C, most preferably at 350 to 400°C. The heat carrier is in direct contact with the waste. If an oxygen-free fluidization gas is used, this blocks the chemical routes to dioxins and furans, for which the temperature level and the presence of catalysts such as (especially) copper, form the other prerequisites. However the process is flexible for the gas atmosphere in the decomposition reactor. If air is used in the decomposition reactor there is a risk for dioxins and furans formation, but as the HCl/water mixture is separated as liquid hydrochloric acid after cooling, the remaining gases, which are not soluble in water, can be fed into the second reactor, where they will be incinerated. The same goes for other gases, such as CH or CO, which may be produced using temperatures needed to bring the amount of chlorine in the waste down to below 1%. The air that is used in the decomposition reactor can be used as secondary air in the combustor, after the HCl/water mixture has been removed.

Chlorine is released as a gaseous mixture of HCl with the moisture from the solid waste. The solid mixture of sand and chlorine-free waste-derived fuel is fed to another reactor where the chlorine-free waste is burnt at 700 to 900°C, preferably at 800 to 900° C, most preferably at 840 to 860°C. This heats up the sand and gives additional heat for steam generation and production of electricity. The hot sand is fed back to the earlier reactor after heat exchange, reducing its temperature to what is needed in the earlier reactor. It is also possible to exploit chlorine-free waste-derived fuel as such.

There is at least two phases in the two-stage process. They can be described as:

At low temperature: PVC + energy El -» HCl + hydrocarbon residue (Rl) t

At high temperature: hydrocarbon residue + air - energy E2 + CO₂ + H₂O (R2)

The two-stage combustion operates with an absence of air (pyrolysis) or in a partial oxidation mode (gasification) in the first stage. The second stage of the process uses air for the combustion reaction.

Other components than PVC in the waste fuel mixture remain preferably unchanged during process (Rl), apart from vaporization of moisture. These other components are combusted together with the hydrocarbon residue from PVC or other chlorine containing waste at higher temperature. With two-stage combustion it is possible to use temperatures above 500°C in the second reactor without any problems related to the HCl emission. The components can be combusted as any other chlorine-free solid waste-derived fuel. At the same time the electricity production and the thermal efficiency of the plant is high and the apparatus and method provides means, via heat carriers, for recovery of the heat of combustion for energy production, heat and electric power generation. It is also possible to increase the amount of plastic, such as PVC waste above 40 % and even to handle pure PVC

The present invention will now be described in more details with reference to favorable exemplifying embodiments and the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a schematic view of a preferred embodiment of the method used in combustion of solid waste.

Figure 2 is a flow sheet of one preferred apparatus for combustion of solid waste.

Figure 3 is a flow sheet of another preferred apparatus for combustion of solid waste.

Figure 4 graphically discloses the effect of the pyrolysis reactor temperature on HCl recovery.

Figure 5 graphically discloses the effect of the PVC in the fuel on the process thermal efficiency for a typical PVC.

Figure 6 graphically discloses the effect of the PVC in the fuel on the LHV of the total residue for a typical PVC. • ^'

Figure 7 graphically discloses the effect of the water content in the fuel on the process efficiency for a solid waste containing a typical PVC.

Figure 8 graphically discloses the effect of the stochiometric ratio, λ on the process efficiency a solid waste containing a typical PVC.

Figure 9 graphically discloses the effect of the PVC in the fuel on the process thermal efficiency for a typical PVC.

In Figure 1 the waste-derived fuel 31 is fed to a fluidized bed reactor 1, which is fluidized with nitrogen, air or another gas 32 (such as recirculated flue gas from 35). Chlorine is released as a gaseous mixture of HCl with the moisture from the solid waste 33. The solid mixture of sand and chlorine-free waste-derived fuel 34 is fed to a second reactor 3, 4, and 5 together with make-up sand 36. The chlorine-free waste-derived fuel is burnt and this heats up the sand and gives additional heat for steam generation in the form of flue gas 35. The hot sand 38 is fed back to the first reactor after cooling in a heat exchanger 24. Ash and sand 39 are eliminated from the process.

In Figure 2 the wood is dried in dryer 2 and then pyrolysed with PVC in the pyrolysis reactor 1. Thermal input for the pyrolysis reactions comes from the recycled hot sand from the fluidized bed combustor FBC 3, 4 and 5. A flow of nitrogen, air or another gas is used to fiuidize the bed in the pyrolysis reactor 1. The removal of water + HCl from the product gas is not included here for simplicity. The FBC is modeled as a burner 3 plus a hot bed 4 with a fluidized boiler (drum) 5. The chlorine free waste-derived fuel is burnt in the FBC, followed by heat recovery in a super heater 6, economizer 7 and air preheater 8.

Electric power is generated using a steam turbine 10, 11, 12, 13 and 14 where the first stage is a regulation stage, followed by three stage groups with bleeding of steam for the feed water tank 22 and the feed water heater 19 and final expansion in the last stages. Feed water from feed water tank 22 is re-heated in the economizer 7 and in the sand return cooler 24. The feed water reach the fluidized boiler 5 in a liquid phase and is then superheated in the super heater 6.

In Figure 3 the wood is dried first in a dryer 2 and then pyrolysed with the PVC in the pyrolysis reactor 1. Feed water from the feed water tank 22 is pre-heated in the economizer 8 and re-heated once more in the sand return cooler 25. Then it goes to the boiler 5 as a saturated liquid phase. The steam generated in the fluidized boiler will be superheated in a super heater 6. The steam is expanded in the steam turbine 11 and then reheated in a super heater 7. Also two feed water heaters instead of one give increased efficiency. The steam leaving the cooler 25 is still liquid.

EXEMPLIFYING EMBODIMENTS OF THE INVENTION

The temperature window at which a typical PVC is decomposed into HCl and a chlorine- free char is shown in table 1. At 350°C the amount of chlorine in the solid residue is less than 0.1%. De-hydro chlorination can be performed until at least 60 %, preferably 90 %, most preferably 100% of said waste is de-hydro chlorinated.

Table 1 The chlorine concentration in the residue versus temperature for a typical PVC

One favorable embodiment of the invention is shown in Figure 2. The process has been simulated by a software package for simulation of thermal processes. The input fuel is wet wood and wet PVC. First the wood is dried in the dryer 2 assuming that wood contains 15% water and then pyrolysed with the wet PVC (5% water content) in the pyrolysis reactor 1. The thermal input for the pyrolysis reactions comes from recycled hot sand from the FBC (fluidized bed combustor). A flow of is used to fluidize the bed in the pyrolysis reactor (this gives a fluidization velocity of 1-2 m/s in a bubbling fluidized bed, ^"for example). The removal of water + HCl from the product gas is not included here for simplicity. The FBC is modeled as a burner 3 plus a hot bed 4 with a fluidized boiler 5. The low-chlorine char from the PVC plus the wood are burnt in the FBC, followed by heat recovery in the super heater 6, economizer 7 and air preheater 8.

Electric power is generated using a steam turbine 10+11+12+13+14 where the first stage is a regulation stage followed by three stage groups with bleeding of steam for the feed water tank and the feed water heater and final expansion in the last stages. The isentropic efficiency for the turbine is assumed 0.86. Two feed water heaters instead of one give increased efficiency. The first feed water pressure is 1.17 bar and pressure for the second one is 0.24 bar. Table 2 gives the specifications for this design case.

Table 2 Two-stage combustion of high PVC waste power plant (design case)

Pyrolysis reactor:

Fuel input (20%PVC+80%Wood) 0.5 kg/s PVC +2 kg/s Wood

PVC conversion % 99.8%

Pyrolysis reactor temperature 350°C

Sand input temperature 410°C

Water content in the PVC 5%

Water content in the wood 15%

LHV of wood 17.8 MJ/kg

LHV of CnHm (from PVC after decomposition) 38.2 MJ/kg

Fluidized bed reactor:

Combustion efficiency 0.98

Fluidized bed temperature 800°C

Air factor, stoichiometry 1.1

Steam cycle:

Steam turbine isentropic efficiency 0.86

Condenser pressure 3 kPa

First feed water heater pressure 117 kPa

Second feed water heater 240 kPa

Deaerator pressure 0.3 MPa

Superheater temperature 510°C

Steam pressure 7.8 MPa

Steam mass flow rate 14.24 kg/s

Net plant output 15.9 MW

Thermal efficiency (LHV) 36.7%

Flue gases mass flow rate 17.84 kg/s

HCl recovered 0.276 kg HCl/s

HCl emissions (no gas cleaning) 37 mg/m³ _Sτp dry at 2% O₂

= 20 mg/m³sτp dry at 11% O₂

Minimum stack temperature 150°C

Feed water from feed water tank with 12.24 kg/s mass flow rate, 133°C and 78 bar is reheated in the economizer 7 to 152°C and to 293°C in the sand return cooler 24. The feed water reach the fluidized boiler 5 in a liquid phase and is then superheated in the super heater 6 to 510°C/78 bar. The steam parameters 510°C/ 78 bar are optimal for the heat available in the super heater. Pressure was increased from an initial value of 60 bar to 78 bar in order to increase the saturation temperature from 276°C to 293 °C as to utilize the heat in the return sand cooler 24. At a lower pressure than 78 bar the feed water will be partly evaporated inside the sand cooler before it goes to the evaporator 5. This would result in a two-phase mixture in the sand cooler, which would increase the size of the sand cooler and the piping. The approach temperature is 0°C i.e. the steam leaving the cooler 24 is at the saturation temperature for 78 bar but it is still in liquid phase. This is the optimum case to utilize the heat in the sand that is returned to the pyrolysis reactor.

The minimum stack temperature of 150°C is selected to insure that there will be no condensation of aggressive compounds from the flue gases that will cause corrosion. It would be possible to go below 110°C for the design case to reduce the energy losses and increase the thermal efficiency.

For the design case, with 43.18 MW fuel thermal input, the thermal efficiency is 36.7% (16.046 MW, electricity output), which has been calculated, accounting the power needed to drive the pumps (0.1568 MW) and the blower (0.016 MW).

The chlorine content in the fuel for the FBC is then 0.025%-wt. The temperature of the FBC is chosen at 800°C as to reduce operational problems, which are related to ash behavior when firing biomass or waste-derived fuels. The FBC is fired with air at 2 % oxygen in the dry flue gases (stoichiometric ratio, λ = 1.1).

The pyrolysis reactor temperature range between 250 to 400°C has been selected here. A typical PVC starts to decompose already at 250°C with a conversion of 21% (conversion ratio here means the conversion of the PVC to HCl and residue). The influence of the temperature in the pyrolysis reactor has an effect on thermal efficiency, chlorine content in the fuel that is burnt in the FBC and the HCl emissions from the FBC. Results of an analysis with pyrolysis temperatures from 250 to 400°C are given in Table 3. The thermal efficiency of the process appears to vary from 36.7% to a maximum of 37.1% for pyrolysis at 310°C. The emissions of HCl are high at temperatures below 340°C, while above 350°C the emission of HCl will be even below the allowable emission for Finland/EU (10 mg/m³ at 11% O₂). Figure 4 shows the effect of pyrolysis reactor temperature on the recovery of HCl from a typical PVC.

Table 3 Influence of pyrolysis temperature on process performance and efficiency with (PVC/wood, 20%/80%) fuel

The content of PVC in the solid waste is a very important parameter and affects the thermal efficiency of the plant. Results of an analysis with changing PVC content from 0% to 40%, in the fuel used in the pyrolysis reactor is shown in Table 4. By using only wood (0 %PVC) in the pyrolysis reactor, the thermal efficiency is 36.3%, while using 40 % PVC will increase the thermal efficiency to 37.2%. Figure 5 shows the effect of PVC content in the fuel on the thermal efficiency of the plant. The reason for this is the high heating value of PVC (21 MJ/kg) as compared to the heating value for wood (17.8 MJ/kg). Figure 6 shows the effect of the PVC% in the fuel on the LHV of the total residue (wood + residue of PVC) that will be burned in the FBC. Table 4 Influence of the input waste fuel PVC content on process performance and efficiency (with PVC 99.8% conversion)

Table 4 Influence of the input waste fuel PVC content on process performance and efficiency (continued)

Also the mass flow rate of the sand coming from the sand cooler (return sand) to the pyrolysis reactor is decreasing with increasing of PVC content in the fuel, which means that the energy needed in the pyrolysis reactor to decompose the fuel is decreasing. This related to the fact that PVC decomposition is exothermic. With no PVC pyrolysed the mass flow rate of the sand is 23.6 kg/s, while it is 8.58 kg/s for 40% PVC in the fuel.

The water content in the fuel has an important effect on the plant efficiency. When the moisture content percentage increases, it causes a decrease in heat from the fuel when it is burnt and consequently, it will decrease the electrical output and plant efficiency. For the design case, the moisture content was 15% in the wood and 5% in the PVC for fuel composition 80% wood + 20% PVC. Three more cases are calculated with 7.5%, 30% and 45% moisture content in the wood, with at the same time for PVC 2.5%, 10% and 15%. Thus, the total water content in the fuel will be 7%, 13%, 26% and 39% respectively. Figure 7 shows that the changes in the plant efficiency for the first case (36.8%) and for the design case (36.7%) are small but for the third case (35.7%) and fourth case (35%) are significant. The water content for the wood after the dryer (for these four cases) is 0%, 0%, 9% and 27% respectively, as calculated using similation software for thermal processes.

In general, plastics require more air for complete combustion when compared to other mass fractions in municipal solid wastes. If the solid waste fuel contains 100% plastic then the air- supplying equipment has to be able to provide 2.5 to 3 times the amount of air theoretically required for combustion of plastic in order to insure complete combustion.

For the design case, the stoichiometric ratio λ = 1.1 was selected for a fuel composed of 80% wood + 20% PVC. Four more cases are calculated with λ = 1.2, 1.3, 1.4, 1.5 respectively. Figure 8 shows the effect of the stoichiometric ratio increase on plant efficiency. It is obvious that the efficiency is decreasing with increasing air. The plant efficiency drops by 0.5% from 36.7% (λ = 1.1) to 36.2% (λ = 1.5). The reason for that is related^' to the increase in the flue gases losses due to the increase of its mass flow rate. Also, the electrical power needed for the air blower, which is taken from the net electrical power from the alternator will be increased with increasing (λ) and that will decrease the plant efficiency. Another favorable embodiment of the invention is shown in Figure 3. The process has been optimized using thermal process simulation software. The apparatus is similar to the previous one but another stage of reheat has been added to heat recovery system. The input fuel is 80%wet wood + 20%wet PVC. The wood is dried first in the dryer 2 and then pyrolysed with the PVC in the pyrolysis reactor 1. Table 5 gives the specifications for the design case.

Table 5 Two-stage combustion of high PVC waste power plant (design case with reheat)

Pyrolysis reactor:

Fuel input (20%PVC+80%Wood) 0.5 kg/s PVC + 2 kg/s Wood

PVC conversion % 99.8%

Pyrolysis reactor temperature 350°C

Sand input temperature 400°C

Water content in the PVC 5%

Water content in the wood 15%

LHV of wood 17.8 MJ/kg

LHV of C_nH_m (from PVC after decomposition) 38.2 MJ/kg

Fluidized bed reactor:

Combustion efficiency 0.98

Fluidized bed temperature 800°C

Bed height l m

Bed and ree board height 4 m

Steam cycle:

Steam turbine isentropic efficiency 0.86

Condenser pressure 0.03 bar

First feed water heater pressure 1.3 bar

Second feed water heater 0.6 bar

Deaerator pressure 3 bar

Superheater temperature 460°C

Steam pressure 78 bar

Reheat temperature 460°C

Reheat pressure 7 bar

Steam mass flow rate 12.44 kg/s

Net plant output 15.75 MW

Thermal efficiency (LHV)

Flue gases mass flow rate

HCl recovered

HCl emissions (without gas cleaning)

Minimum stack temperature 150°C Feed water from the feed water tank at 133°C, 78 bar and 12.44 kg/s mass flow rate is preheated in the economizer 8 to 152°C and re-heated once more to 293 °C in the sand return cooler 25. Then it goes to the boiler 5 as a saturated liquid phase. The steam generated in the fluidized boiler will be superheated to 460°C/78 bar in super heater 6 (the first super heater temperature 460°C has been chosen because there is not enough heat to reheat the steam from the flue gases if the temperature 510°C is chosen instead as in the case without reheat). The steam parameters 460°C/78 bar are optimal for the heat available in the super heater. The steam will be expanded in the steam turbine 11 to 212°C/7 bar and will be reheated to 460°C/7 bar in super heater 7. Also two feed water heaters instead of one give increased efficiency. The first feed water pressure is 0.6 bar and the pressure for the second is 1.3 bar. The approach temperature is 0°C i.e. the steam leaving the cooler 25 is at the saturation temperature for 78 bar but it is still liquid. This is the optimum case to utilize the heat in the sand that is returned to the pyrolysis reactor. The isentropic efficiency for the turbine is again assumed equal to 0.86.

Also the minimum stack temperature again is 150°C, selected to insure there will be no condensation of aggressive compounds from the flue gases that will cause corrosion problems. For the design case, with 43.18 MW fuel thermal inputs, the thermal efficiency is 36.5%, (15.97 MW), which has been calculated accounting for the power needed to drive the pumps (0.138 MW) and the blower (0.08 MW). The chlorine content in the fuel for the FBC is then 0.025%-wt. The temperature of the FBC is chosen at 800°C as to reduce operational problems, which are related to ash behavior when firing biomass or waste-derived fuels. The FBC is fired with air at 2 % oxygen in the dry flue gases (λ = 1.1).

Results of an analysis with changing PVC content in the fuel used in the pyrolysis reactor from 0% to 40% are shown in Table 6. By using only wood (0 %PVC) in the pyrolysis reactor, the thermal efficiency is 35.9%, while using 40 % PVC the thermal efficiency is 37.1%. This is because of the high heating value of PVC (21 MJ/kg) compared with the heating value of wood (17.8 MJ/kg). Figure 9 shows the effect of PVC content in the fuel on the thermal efficiency of the process. Table 6 Influence of the input waste fuel PVC content on process performance and efficiency (with PVC 99.8% conversion) with reheat

Table 6 Influence of the input waste fuel PVC content on process performance and efficiency (continued)

Also the mass flow rate of the sand coming from the ash cooler (return sand) to the pyrolysis reactor is decreasing with increasing of PVC content in the fuel. With no PVC pyrolysed the mass flow rate of the sand is 33.13 kg/s, while it is 8.58 kg/s for 40% PVC in the fuel.

Above the present invention has been disclosed with reference to some exemplifying embodiments, but for the professional it is clear that the invention can be implemented also in many other ways within the scope of the appended claims.

Claims

1. An apparatus for combustion of solid waste, characterized in that the apparatus comprises at least one first reactor (1) for de-hydro chlorination of the waste and at least one second reactor (3, 4, 5) for combustion of the waste, at least one of said reactors being a fluidized bed reactor.

2. The apparatus according to claim 1, characterized in that said first reactor (1) comprises a fluidized bed reactor and said second reactor (3, 4, 5) comprises a fluidized bed reactor.

3. The apparatus according to any one of the preceding claims, characterized in that said first reactor (1) comprises means for heating of the said waste at 200 to 400°C, preferably at 300 to 400°C, most preferably at 350 to 400°C.

4. The apparatus according to any one of the preceding claims, characterized in that . said second reactor (3, 4, 5) comprises means for heating of the said waste at 700 to

900°C, preferably at 800 to 900°C, most preferably at 840 to 860°C.

5. The apparatus according to any one of the preceding claims, characterized in that said apparatus comprises means for fluidizing a bed in said first (1) and/or second reactor (3, 4, 5) with a gas.

6. The apparatus according to any one of the preceding claims, characterized in that means are provided for feeding heat carrier, preferably a solid heat carrier, to said first reactor (1) and said second reactor (3, 4, 5) and for re-circulating said heat carrier from said second reactor (3, 4, 5) to said first reactor (1).

7. The apparatus according to any one of the preceding claims, characterized in that said first reactor (1) includes means for recovery of HCl and for re-circulation of gases from said first reactor (1) to said second reactor (3, 4, 5). The apparatus according to any one of the preceding claims, characterized in that a dryer (2) is arranged for drying all or a part of said waste.

The apparatus according to any one of the preceding claims, characterized in that said second reactor (3, 4, 5) is provided with means for recovery of the heat of combustion for heat and electric power generation. . A method for combustion of solid waste, characterized in that solid waste is de- hydro chlorinated in at least one first reactor and de-hydro chlorinated solid waste is combusted in at least one second reactor, at least one of said reactors including fluidization of said waste. . The method according to claim 10, characterized in that said de-hydro chlorination of said^" waste takes place at 200 to 400°C, preferably at 300 to 400°C, most preferably at 350 to 400°C. - The method according to any one of claims 10 to 11, characterized in that said waste is combusted at 700 to 900°C, preferably at 800 to 900°C, most preferably at 840 to 860°C. i ' . The method according to any one of claims 10 to 12, characterized in that fluidization is provided by feeding a fluidizing gas such as air or nitrogen into said reactors. . The method according to any one of claims 10 to 13, characterized in that a fluidized bed is provided by feeding solid heat carrier and re-circulating said solid heat carrier from one reactor to another into direct contact with said waste. . The method according to any one of claims 10 to 14, characterized in that HCl gas which is freed in said first reactor is removed in water and other gases than HCl are re-circulated as fuel to said combustion. The method according to any one of claims 10 to 15, characterized in that said waste contains PVC.

The method according to any one of claims 10 to 16, characterized in that de- hydro chlorination is performed until at least 60%, preferably 99%, most preferably 100% of said waste is de-hydro chlorinated.

The method according to any one of claims 10 to 17, characterized in that energy is recovered from gases emanating from said second reactor by means of heat exchangers.

Use of solid chlorine containing waste for production of useful energy by de-hydro chlorination of solid waste in at least one first reactor and combustion of de-hydro chlorinated solid waste in at least one second reactor, at least one of said reactors including fluidization of said waste.