FI117574B - Method and equipment for incineration and use of waste for energy generation - Google Patents

Description

117574

METHOD AND APPARATUS FOR INCINERATION OF WASTE AND USE OF WASTE FOR ENERGY PRODUCTION Field of the Invention

The present invention relates to a method and apparatus for incinerating solid waste.

This method can be used to produce thermal and electrical power. ;

Description of the state of the art

There is great interest in the efficient use of municipal waste as an energy source and potential chemical raw material. The hope is to save on fossil fuels, and solid municipal waste is cheap and readily available. Furthermore, the disposal of municipal waste in landfills is an environmental problem, as land is being lost and toxic decomposition products and greenhouse gases are emitted from landfill sites. In addition, plastic waste in particular contains significantly bound energy which can be recovered by incineration processes.

The mass incineration of solid waste as well as waste energy generating processes with a particular focus on energy recovery are severely constrained by excessive levels of chlorine-containing compounds. Generally, waste fuels should contain less than 2% by weight of chlorine to avoid problems with the operation of the incinerator, incinerator or carburettor.

The problems are mainly related to corrosion, which causes low vapor parameters and leads to thermal efficiencies of about 20%. This is largely due to the presence of PVC (polyvinyl chloride), a polymer containing about 55% chlorine (Cl). For example, * · · • * / In Finland, more than 90% of the chlorine in waste is derived from PVC.

* * · · · ··, '··. · ...

• · * · * "incoming conventional waste incineration plant steam the value of the temperature should be limited • · · • · less than 500 ° C, in order to avoid fire-side high-temperatures overheat range * · · • * * ··· * of corrosion associated with the flue gases in the corrosive nature of the Thus, the low incoming steam value of the steam turbine reduces the electricity production and the thermal efficiency of the plant.

• # ·

Special materials are required to combat corrosion, which results in higher investment and maintenance costs. Although conventional waste incinerators are capable of handling municipal waste containing plastic, they are not capable of handling waste with a high plastic content. In order to avoid problems in traditional incinerators, the maximum amount of plastic waste incinerated should be about 5% of the total amount of waste. Most conventional furnaces * • · * · / ·· cannot provide sufficient air to completely burn plastics.

During incomplete combustion, soot is formed which adheres to the walls of the heat exchanger tube 2 117574 and affects its performance. Processes designed for plastics require gas cleaning.

U.S. Patent No. 3,716,339, which discloses a hydrogen fuel recovery furnace for hydrogen and chlorine-containing plastics, does not provide a solution for problematic municipal waste incineration with high electrical efficiency. Since the decomposition temperature of the plastic alloy is quite low, there is still a significant amount of chlorine in the decomposed residue. According to this patent, this plastic residue is partially decomposed in the kiln. As a result, a water jet is needed to purify the flue gas. The conventional kiln used to burn the decomposition residue used in said patent is not useful for generating electricity at high electrical efficiency. The chlorine present in the decomposition residue is the main reason why high electrical efficiency is not achieved. In said patent, heat is used only to cause partial decomposition, not to generate electricity, and the use of fluidized bed reactors is not an advantage here either.

Summary of the Invention

The main object of the present invention is to provide a method and apparatus in which the incineration of otherwise problematic solid waste containing chlorine is used as an energy source. At least energy or electricity and HCl can be recovered. Approximately 36% of the (electric) thermal efficiency can be achieved, depending on the temperature and plastic content of pyrolysis or gasification and the type of solid waste. The efficiencies are high because the recovery of heat i (t;) from the incinerator is combined with a circulating heat carrier such as sand.

• · • · · * · 1 * • · · 2.1. It is also an object of the invention to provide an apparatus in which the HCl emissions of the kiln are • · .... less than the statutory emission limits without gas purification, without the need to treat hot HCl-containing gases during the process. The characteristics of fluidized bed combustion lead to a relatively · «·: ***: pure combustion process, especially with regard to NOx.

*: 2ί Another object of the invention is to utilize the thermal stability of PVC. Instead of solving the problematic removal of HCl from the flue gases by sorbent, the waste fuel is '' cleaned '' more or less, in fact, by removing hydrogen chloride to produce * 1 1 ·: 1 ·: HCl gas stream and chlorine-free waste fuel can still be burned or,. sold as such as waste fuel.

• · · * · 1 · · · · 2 · ·

Another object of the invention is to provide an apparatus in which HCl is recovered from waste more than 90%.

3, 117574

The objects defined above are achieved in accordance with the present invention in the manner described in the characterizing part of the appended claims. Thus, the process of the present invention is characterized in that the solid waste is dehydrogenated in at least one of the first reactors and the dehydrogenated waste is incinerated in at least one of the second reactors and said waste is fluidized in at least one of these reactors. Thus, the apparatus has at least a first reactor for the removal of hydrogen chloride from the waste and at least a second reactor for the incineration of the waste, and at least one of these reactors is a fluidized bed reactor.

The present invention discloses a process for generating electricity from waste and an apparatus therefor. According to the invention, the rigid system consists of at least two reactors and at least one of these reactors is a fluidized bed reactor, preferably two reactors are fluidized bed reactors. However, any of the reactors may be, for example, a conventional rotary kiln, preferably having a solid heat carrier. According to a preferred embodiment, the removal of hydrogen chloride from the fuel takes place in a bed of hot heat carrier such as sand fluidized with nitrogen in the first reactor at 200-400 ° C, preferably 300-400 ° C, most preferably 350-400 ° C. The heat carrier is in direct contact with the waste. If oxygen-free fluidizing gas is used, it will • block chemical pathways to dioxins and furans, which are also subject to * * ··, ·. temperature level and the presence of catalysts such as (in particular) copper. However, the process is- • · * * * ♦ ··. *. also flexible in view of the gas atmosphere in the decomposition reactor. If air is used in the decomposition reactor i ·, there is a risk of formation of dioxins and furan, but when the · *** · HCl / water mixture is separated as liquid hydrochloric acid after cooling, the remaining ··· water-insoluble gases can be fed to another reactor. The same applies to other gases, such as ChMIe or CO, that can be produced by using the temperatures required to bring the amount of chlorine present in the waste to below 1%. The air * «♦ used in the decomposition reactor can be used as secondary air in the furnace after * · ** ': after removal of the HCl / water mixture.

* «· • · i · · • * # w · · * ··· * ·. - · 4 '117574

Chlorine is released as a gaseous mixture containing HCl and moisture from solid waste. The solid mixture of sand and non-chlorine-derived fuel is fed to a second reactor where the chlorine-free waste is incinerated at a temperature of 700 to 900 ° C, preferably 800 to 900 ° C, most preferably 840 to 860 ° C. This heats up the sand and produces additional heat for steam and electricity production. The hot sand is fed back to the previous reactor after heat exchange, whereby its temperature drops to the value required in this earlier reactor. It is also possible to use non-chlorinated waste fuel as such.

The two-step process has at least two steps. They can be described as follows: low temperature: PVC + energy E1 HC1 + hydrocarbon residue (R1) at high temperature: hydrocarbon residue + air energy E2 + CO2 + H2O (R2) This two-stage combustion takes place without air (pyrolysis) or partial oxidation (gasification) in the first stage. In the second step of the process, air is used for the combustion reaction.

With the exception of PVC, the other components of the waste fuel mixture preferably remain unchanged during the process (R1), with the exception of moisture evaporation. These other components are co-incinerated with PVC or other chlorine-containing waste hydrocarbon residue at higher temperatures. In the case of two-stage incineration, temperatures in excess of 500 ° C can be used in the second reactor without any HC1 · * "· emission problems. These components can be incinerated as any other non-chlorinated solid waste fuel. power generation and thermal efficiency are high and this equipment and method provides means such as heat carriers to recover combustion heat for energy, thermal and electrical power production, and it is also possible to increase the amount of plastic waste such as PVC. percent and * · * treat even pure PVC.

· · · *.

• · * · ·

The present invention will now be described in more detail with reference to preferred exemplary embodiments and the accompanying drawings.

* * *

Ittl * • • • • • »* · · ·« · * ·· • * 5 117574

Brief Description of the Drawings

Figure 1 is a schematic representation of a preferred embodiment of the process used for incineration of solid waste.

Figure 2 is a flow diagram of a preferred apparatus for incinerating solid waste.

Figure 3 is a flow diagram of another preferred apparatus for incinerating solid waste.

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

Figure 5 graphically illustrates the effect of PVC in fuel on the thermal efficiency of the process.

Figure 6 graphically illustrates the effect of PVC in fuel on the residual LHV. ·

Figure 7 graphically illustrates the effect of fuel water content on process efficiency.

Figure 8 graphically illustrates the effect of the stoichiometric ratio λ on process efficiency, '· • t ·· · ·

Figure 9 graphically illustrates the effect of PVC in fuel on the thermal efficiency of the process. relationship.

»· • * * ·. ***; In Figure 1, waste-derived fuel 31 is fed to a fluidized bed reactor 1 where fluidization takes place with nitrogen, air, or other gas 32. Chlorine is released as a gaseous mixture containing ··· HCl and moisture from solid waste 33. Sand and chlorine-free ·: **: a solid mixture of waste-derived fuel 34 is fed to the second reactor 3, 4 and 5 • * · * ../ together with auxiliary sand 36. This chlorine-free fuel will be burned and. ***. this heats up the sand and generates extra heat to produce the vapor 35 as flue gas. The hot sand 38 is fed back to the first reactor in a heat exchanger, * ·. 24 after cooling. The ash and sand 39 are removed from the process.

• · · * ·· ♦ ·· «·· • · 6 117574

In Figure 2, the wood is dried in a dryer 2 and then pyrolyzed with PVC in a pyrolysis reactor 1. The heat supplied to the pyrolysis reactions is obtained from recycled hot sand from a fluidized bed combustion furnace FBC 3, 4 and 5. A stream of nitrogen, air, or other gas is used to fluidize the bed in the pyrolysis reactor 1. The removal of water + HCl from the product gas is not shown for simplicity. The FBC is implemented as a burner 3 plus a hot bed 4 with a fluidized boiler (drum) 5. Non-chlorine-derived fuel is burned in the FBC, followed by heat recovery in the superheater 6, the preheater 7 and the air in the preheater 8.

Electric power is generated using a steam turbine 10, 11, 12, 13 and 14, the first stage being the control step, followed by three-stage groups from which steam is drawn for the feed water tank 22 and the feed water heater 19, and a final pressure reduction. The feed water from the feed water tank 22 is reheated in the preheater 7 and the reflux condenser 24. The feed water reaches the fluidized boiler 5 in the liquid phase and is then reheated in the superheater 6.

In Figure 3, the wood is first dried in a dryer 2 and then pyrolyzed with PVC in a pyrolysis reactor. The feed water from the feed water tank 22 is preheated in the preheater 8 and again in the sand reflux condenser 25. It then enters the boiler 5 as a saturated liquid phase. The steam produced in the fluidized boiler is superheated in the superheater 6. The steam is allowed to expand in the steam turbine 11 and then reheated in the superheater 7. The efficiency is also improved by two feed water heaters, one by one. instead of. The steam leaving the cooler 25 is still in liquid form.

: ·: • · • ·

Examples of Embodiments of the Invention • ·, · »·. The temperature range at which PVC decomposes to chlorine-free carbon is shown in Table 1. At 350 ° C * · ···, »··, the amount of chlorine in the solid residue is less than 0.1%. The removal of hydrogen chloride may be carried out with at least 60%, preferably 90%, most preferably 100% hydrogen chloride removed.

··· • · M * • · · • * • ·

Ml f ···· • * t · · • »· ··· ······ · · 7 117574

Table 1 Chlorine content in the residue, depending on temperature Temperature (° C) __ HCl (%) depleted of PVC

A preferred embodiment of the invention is shown in Figure 2. The hardware components are listed in Table 7. This process is simulated with software for simulating power plant processes. The fuel to be fed is wet wood and wet PVC. The wood is first dried in a dryer 2, assuming that the wood contains 15% water, and then pyrolysed with wet PVC (5% water content) in the pyrolysis reactor 1. The heat supplied to the pyrolysis reactions comes from recycled hot sand from FBC (fluidized bed incinerator). A nitrogen flow of 4 kg / s is used to fluidize the bed in the pyrolysis reactor (this gives a rate of · · Γ of 1 to 2 m / s in a bubbled fluidized bed, for example). Water + HCl removal * · · • · from product gas is not included here for simplicity. The FBC is made into a burner • · ... 3 + hot bed 4 with a fluidized boiler (ramp) 5. Made of PVC and wood, only * · l. '.' low-chlorine carbon is burned in FBC, followed by heat recovery * · in superheater 6, preheater 7 and air in preheater 8.

Electrical power is produced using a steam turbine 10 + 11 + 12 + 13 + 14, with the first * * · *; the phase is the control phase, followed by the three phases, from which steam is extracted • * for the inlet water tank and the inlet water heater, and the final pressure reduction • · in the final stages. The isentropic efficiency of the turbine is assumed to be 0.86. Two * · ·; . Feed water heater instead of one improves efficiency. The pressure of the first feed water • · · * tl '* is 1.17 bar and the pressure of the second is 0.24 bar. Table 2 shows the technical features for the design case.

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Table 2 Two-stage incineration of a PVC-rich power plant (design case)

the pyrolysis reactor:

Fuel supply (20% PVC + 80% wood) 0.5 kg / s PVC + 2 kg / s wood PVC conversion,% 99.8%

Pyrolysis reactor temperature 350 ° C

Sand feed temperature 410 ° C

Water content of PVC 5%

Water content of wood 15%

The LHV of the wood is 17.8 MJ / kg

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

The fluidized bed reactor:

Combustion efficiency 0.98

Fluid 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 117kPa

Second feed water heater 240 kPa

Air vent pressure 0.3 MPa

Superheater temperature 510 ° C

Vapor pressure 7.8 MPa Steam mass flow rate 14.24 kg / s

The total output of the plant is 15.9 MW

Thermal Efficiency (LHV) 36.7%

Flue gas mass flow rate 17.84 kg / s

HCl recovered 0.276 kg HCl / s · · HCl emissions (no gas cleaning) 37 mg / m3STP dry, 2% O2 · · · = 20 mg / m3sTp dry, 11% O2

* _ · * Minimum chimney temperature 150 ° C

** · · "- --———“ • * • · * Feed water from a feedwater tank having a mass flow rate of 12.24 kg / s, 133 ° C and 78 bar, • V * • · "··· * is heated again in preheater 7 to 152 ° C and 293 ° C in m · * ··· * sand reflux condenser 24. The feed water reaches the fluidized boiler 5 in the liquid phase and then overheats in the superheater 6 to 510 ° C / 78 bar. These steam parameters · ♦ ··· • * ... 510 ° C / 78 bar are optimal for the heat available in the superheater.

• ·

The pressure was raised from a starting value of 60 bar to 78 bar to raise the saturation temperature ·· * • · · .. · * from 276 ° C to 293 ° C to use heat in a sand reflux condenser 24. At a pressure of less than 78 bar, the feed water evaporates partially inside the sand cooler. to the evaporator 5. This would result in a biphasic mixture in the sand cooler, * ···· '# * 9 117574, which would increase the size of the sand cooler and piping. The approach temperature is 0 ° C, i.e. the steam leaving the cooler 24 is at saturation temperature at 78 bar but is still in the liquid phase. This is the optimal way to utilize the heat of the sand returned to the pyrolysis reactor.

A minimum chimney temperature of 150 ° C is selected to ensure that the flue gas does not condense corrosive compounds that cause corrosion. In the design case, it may be possible to operate below 110 ° C to reduce energy loss and increase thermal efficiency.

In the design case, when the heat input is 43.18 MW, the heat efficiency is 36.7% (16.046 MW, power generation), calculated taking into account the power required to operate the pumps and fan (0.1568 MW and 0.016 MW, respectively).

The chlorine content of the FBC fuel is then 0.025% by weight. The temperature of the FBC is selected at 800 ° C to reduce operational problems associated with ash behavior when burning biomass or waste-based fuels. Combustion in FBC takes place using air containing 2% oxygen in dry flue gases (stoichiometric ratio λ = 1.1).

The temperature of the pyrolysis reactor is selected in this range from 250 to 400 ° C. The decomposition of PVC begins already at 250 ° C with a conversion of 21% (here the conversion ratio means conversion of PVC to HCl and residue). The temperature of the pyrolysis reactor influences the thermal efficiency, ·· 1 · • · .., the chlorine content of the fuel burned in the FBC and the HCl emissions of the FBC. Table 3 * 1 · shows the analytical results at pyrolysis temperatures in the range of 250-400 ° C.

* 1 1

The thermal efficiency of the process seems to vary from 36.7% to a maximum value of 37.1% for pyrolysis at 310 ° C. HCl emissions are high at temperatures below 340 ° C * · # · .2 ·. temperatures, while above 350 ° C, HCl emissions are even less than · 1 1

Emission allowed in Finland / EU (10 mg / m, when (V content is 11%). Figure 4 shows the effect of ... · »pyrolysis reactor temperature on HCl recovery from PVC.

here • · * · • ·· t · * a a f1 ··· '·.' • · 1 1 2 • 1 · * a a * ·· 1 · ♦ · 117574 ίο

Table 3 Effect of Pyrolysis Temperature on Process Performance and Efficiency with (PVC / Wood, 20% / 80%) Fuel

Pyrolysis temperature, ° C 250 280 310 340 370 400

Sand return temperature, ° C 310 350 370 400 430 460

Sand reversible, kg / s 15J [öJ7 ίΐόδ 15J1 ΓδΓΐ 20.5

Fuel to FBC, kg / s 2.42 2.36 2.22 2.2 2.15 2.15

Chlorine in FBC fed material 55 12 0.1 0 0, wt% _______ Thermal Effect Pyrolysis Reactor, MW q.67 0.94 0.7 0.75 0.87 0.98 Thermal Effect FBC, MW 25.9 24.4 21.8 21 20.3 19.93 Electricity Production, MW 18 9 ig j9 169 15.9 15.84 15.8 Thermal efficiency,% 36.7 36.8 37.1 36.7 36.8 36.7 HCl emissions, mg / mJsTP (2% 02) 134 1007 1850 112 0 0 HCl emissions, mg / nr $ TP (11% 02) 705 5300 974 59 0 0 HCl recovered from PVC, kg / s 0.06 0.12 0.25 0.27 0.28 0.28 HCl recovery efficiency,% 21 42 90 99 100 100 The PVC content of the fuel is a very important parameter and it influences the thermal efficiency of the plant. Table 4 shows the results of the analysis obtained by varying the PVC content in the range 0 to 40% in the fuel used in the pyrolysis reactor. When using only wood (0% PVC) in the pyrolysis reactor, the thermal efficiency is 36.3%, whereas in the case of 40% PVC, the thermal efficiency rises to 37.2%.

. Figure 5 shows the effect of the PVC content of the fuel on the thermal efficiency of the plant. * · .. #. T The reason for this is the high calorific value of PVC (21 MJ / kg) compared to the calorific value of wood (17.8 MJ / kg). • ♦ ··. ·. Figure 6 shows the effect of the percentage PVC fuel content on the LHV value of the total residue (wood + PVC residue) burned in the FBC (wood + PVC residue).

* · · • · • 1.

·· ♦ ·· '«· ♦ ·· * ·· 2: • · • 1 · • · ··· ···» · * · ···'.

· *** · '• 1 • · · • · ·.

*** '· 141 2 • · 11 117574

Table 4 Effect of PVC content of feedstock-derived feedstock on process performance and efficiency (with a PVC conversion of 99.8%) PVC content (dry),% by weight 0 5 .10 15 20

Sand return temperature, ° C 420 420 420 415 410

Sand return flow, kg / s 23.6 21.2 18.84 17.7 16.5

Fuel to FBC, kg / s 2.45 2.37 2.31 2.23 2 16

Combustion of chlorine in FBC q 0.00 0.012 0.018 0.02% by weight ____ Thermal Effect Pyrolysis Reactor, MW 132 119 \ 06 0.92 0 79 Thermal Effect FBC, MW jgj 190 20 20.2 20.5 Power Production, MW 26.1 16j 16 0 15 94 15 g Thermal efficiency,% 36.3 36.4 36.5 36.6 36.8 HCl emissions, mg / mJsTP (2% 02) 0 9 19 28 37 HCl emissions, mg / mJsTP (11% 02) 0 5 10 15 20 HCl recovered from PVC, kg / sec 0 0.07 0.14 0.21 0.28 HCl recovery efficiency,% 99 8 99 8 99 8 99 8 99 8

Table 4 Effect of PVC content of feedstock-derived feedstock on process performance and efficiency (cont'd) PVC content (dry),% by weight 25 30 35 40

Sand return temperature, ° C 405 4QQ 395 399

Sand return flow, kg / s 15 0 13 3 11 2 8 58; ··: Fuel to FBC, kg / s 2.09 2.01 1 93 1 86

9 93 994 0 049 0 058 ··· · · · · · · · · ·. in substance, weight% __ * '. Thermal Effect Pyrolysis Reactor, MW 9 55 9 53 94 927 • ♦ - '1 —I— - h. ... Thermal Effect FBC, MW 21? 1 5 22 34 23 37 • · · .. _ Power Generation, MW 15.8 15i7 15 66 ^ 59 • 9 I ^ —J_ | ___ ^, _ ___ Heat Efficiency,% 35 9 37 371 37 2 HCl emissions, mg / mJsTP (2% 02) 47 57 66 • · ____ ..... HCl emissions , mg / mJsTP (11% 02) 24.7 30 34.7 40 * 1 HCl recovered from PVC, kg / s 935,941,943,955 • · _ _ '_1_ *** ·. HCl recovery efficiency. % 993 993 993 993 * · ^ '' · - -. I 1.. - * * »· ·» · · • · · · 1 · · 12 117574

Likewise, the mass flow of sand from the sand cooler (return sand) to the pyrolysis reactor decreases as the PVC content of the fuel increases, which means that less energy is needed in the pyrolysis reactor to decompose the fuel. This is due to the exothermic decomposition of PVC. When PVC is not pyrolysed at all, the mass flow rate of the sand is 23.6 kg / s at 8.58 kg / s with 40% PVC in the fuel.

The water content of the fuel plays an important role in the efficiency of the plant. As the percentage humidity increases, it causes a reduction in the amount of heat it produces when the fuel is burned, and consequently the plant's electrical output and efficiency is reduced. In the design case, the moisture content of the wood was 15% and that of PVC 5%, while the fuel composition was 80% wood + 20% PVC. In addition, three other cases of 7.5%, 30% and 45% moisture and 2.5%, 10% and 15% PVC were included. Thus, the total water content of the fuel is 7%, 13%, 26% and 39%, respectively. Figure 7 shows that the changes in plant efficiency are small in the first case (36.8%) and in the design case (36.7%), but significant in the third case (35.7%) and the fourth case (35%). After the dryer (in these four cases) the water content of the wood is 0%, 0%, 9% and 27% respectively.

Generally, plastics require more air for complete combustion compared to other mass fractions in solid municipal waste. If the solid waste fuel contains 100% plastic, then the air supply equipment must be able to produce 2.5 to 3 times it. the amount of air theoretically needed to burn the plastic to achieve the perfect · «·· • · ... combustion.

• · • · ·· · • · • 1 * ♦

In the design case, the stoichiometric ratio λ = 1.1 was selected for a fuel composed of 80% wood + 20% PVC. The other four cases were also calculated correspondingly with λ: η values of · · 1 1.2, 1.3, 1.4, 1.5. Figure 8 illustrates the effect of an increase in stoichiometric ratio ** on plant efficiency. It is obvious that the efficiency decreases as the air increases. The efficiency of the plant is reduced by 0.5% from 36.7% (λ = 1.1) to 36.2% (λ = 1.5).

* 1 1

The reason for this is the increase in flue gas losses due to the increase in its mass flow rate. Likewise, the electric power required for an air blower, which is obtained by AC · · · ·: 1 · 1. the total electric power of the generator, increases with λ: η, which reduces the plant. efficiency.

9 · · · 13 117574

Figure 3 illustrates another preferred embodiment of the invention. This process is optimized using PROSIM software. The equipment shown in Table 8 is similar to the one above, but a second reheating step has been added to the heat recovery system. The fuel input is 80% wet wood + 20% wet PVC. The wood is first dried in a dryer 2 and then pyrolyzed with PVC in a pyrolysis reactor 1. Table 5 shows the technical data for this design case.

Table 5 Two-stage incineration of a PVC-rich power plant (design case using reheating)

the pyrolysis reactor:

Fuel supply (20% PVC + 80% wood) 0.5 kg / s PVC + 2 kg / s wood PVC conversion,% 99.8%

Pyrolysis reactor temperature 350 ° C

Sand feed temperature 400 ° C

Water content of PVC 5%

Water content of wood 15%

Wood I.I IV 17.8 MJ / kg

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

The fluidized bed reactor:

Combustion efficiency 0.98

Fluid bed temperature 800 ° C

Bed height lm

Bed and free edge height 4 m • · · * · · L; · Steam Turbine Efficiency 0.86 ·; ··· Condenser Pressure 0.03 bar

First feed water heater pressure 1.3 bar '··· * Second feed water heater 0.6 bar

Vent pressure 3 bar

Superheater temperature 460 ° C

, Vapor pressure 78 bar

Re-heater temperature 460 ° C

Re-heater pressure 7 bar · * Steam mass flow rate 12,44 kg / s • ·

The total output of the plant is 15.75 MW

. Thermal Efficiency (LHV) 36.5%; '· * · Flue gas mass flow rate 19.4 kg / s I. HCl recovered 0.276 kg HCl / sec * · * · HCl emissions (no gas cleaning) 34 mg / m3STP dry, 2% O2 = 18 mg / m3sxp dry, 11% O2

Minimum chimney temperature__150 ° C_ 14 117574

The feed water from the feed water tank, having a temperature of 133 ° C, a pressure of 78 bar and a mass flow of 12.44 kg / s, is preheated to 152 ° C in a preheater 8 and reheated again to 293 ° C in a sand reflux condenser 25 It is then passed to boiler 5 as a saturated liquid phase. The steam produced in the fluidized bed boiler is superheated to 460 ° C at 78 bar overheater 6 (the first superheater temperature of 460 ° C is selected because there is not enough heat to reheat the steam from the flue gases if it is set to 510 ° C instead in the event that reheating is not used). The steam parameters of 460 ° C / 78 bar are optimal for the heat available in the superheater. In the steam turbine 11, the steam is allowed to expand to 212 ° C and, at 7 bar, is reheated to 460 ° C and 7 bar in the superheater 7. Improved efficiency is also achieved with two feed water heaters instead of one. The first pressure of the feed water is 0.6 bar and the second is 1.3 bar. The approach temperature is 0 ° C, i.e. the steam leaving the condenser 25 is at saturation temperature at 78 bar but is still in the liquid phase. This is the optimal way to utilize the heat of the sand returned to the pyrolysis reactor. The isentropic efficiency of the turbine is again assumed (0.86).

Also, the minimum chimney temperature is again 150 ° C to ensure that the flue gas does not condense corrosive compounds that cause corrosion problems. In the design case, when the heat input as fuel is 43.18 MW, the heat efficiency is 36.5%. (15.97 MW), calculated taking into account the need to operate the pumps and blower. power (0.138 MW and 0.08 MW, respectively). The chlorine content of the FBC fuel is then * * · • · 1.1 0.025% by weight. The FBC temperature is set to 800 ° C to reduce operational problems * · related to ash behavior when burning biomass or waste-based fuels. Burning «·. ···. FBC takes place using air containing 2% oxygen in the dry flue gases (λ - 1.1).

• · · 9 9 · · · · · · · · ·

Table 6 shows the results of the analysis obtained by varying the PVC content of the fuel used in the pyrolysis reactor in the range 0-40%. When using only "wood" (0% PVC) in the pyrolysis reactor, the thermal efficiency is 35.9%, while when using 40%. · ♦ ·. PVC, the thermal efficiency is 37.1%. high heat value (21 MJ / kg) • · · versus wood heat value (17.8 MJ / kg) Figure 9 shows the effect of fuel PVC content on process thermal efficiency.

• · ♦ I · »···· * -.

• · 15 117574

Table 6 Effect of PVC content of feedstock-derived feedstock on process performance and efficiency (at 99.8% PVC conversion) on reheating PVC content (dry),% 0 5 10 15 20

Sand return temperature, ° C 400 400 400 400 400

Sand return flow, kg / s 33 1 29.79 26.47 23.14 19.85

Fuel to FBC, kg / s 2 22 2 39 2 31 2 24 2 16

Chlorine in FBC fuel q 0.006 0 012 0.018 0.025% by weight __ Thermal effect pyrolysis reactor, MW 133 119 j q6 0 93 0 79 Thermal effect FBC, MW 116 1124 1 1165 1188 17.26 Production of electricity. MW 15.9 15.91 15.85 15.8 15.75 Thermal efficiency,% 35.9 _ 36 36.2 313 36 5 HCl emissions, mg / mJsTP (2% 02) 0 9 ~ 17 ~ 26 34 HCl emissions, mg / mJSTP (11% 02) 0 4.7 9 13.6 18 HCl recovered from PVC, kg / s 0 0.07 0.14 0.21 0.28 HCl recovery efficiency,% 99 3 99 3 99 3 993 993. ,

Table 6 Effect of PVC content of feedstock-derived feedstock on process performance and efficiency (continued) PVC content (dry),% by weight 25 30 35 40

Sand return temperature, ° C 395 399 385 330

Sand return flow, kg / s 15.05 13 3 11 2 8 58

Fuel to FBC, kg / s 2.09 2 02 1 94 1 87

The chlorine in the fuel fed to FBCi 0.032 0.04 0.049 0 058 *. 'in matter, by weight% ____:. * Thermal Effect Pyrolysis Reactor, MW 0.66 0.53 0.4 0 28 ····· - --- - - -' 'Thermal Effect FBC, MW 17.68 13 93 19.11 20.31 Electricity Production, MW ~ ϊϊόί) 1164 1158 15.53 · - _ __ _ ____________ Thermal efficiency,% 36.6 36.8 36.9 37.1. HCl emissions mg / nrisTP (2% 02) 43 52 61 70 HCl emissions mg / mTSTp (11% 02) 22.6 27.4 32 37 • - | M · -—- ·; * HCl recovered from PVC, kg / s 0 35 0 41 0 48 0 55 ··· ______ _____ HCl recovery efficiency,% 99 3 99 3 99 3 993

·· ** · "" "1 -—— 1-- 1 —I

• · a * • · · • · a * · •• aa · '' a * 16 117574

Also, the mass flow rate of the sand (reflux sand) from the ash cooler and fed to the pyrolysis reactor decreases as the PVC content of the fuel increases. When PVC is not pyrolysed at all, the mass flow rate of the sand is 33.13 kg / s, to 8.58 kg / s in the case of fuel containing 40% PVC.

Table 7 Parts of the equipment shown in the two-stage solid waste incineration flow diagram (Figure 2)

The reference (Figure 2) __ device ____Ominaisuus _1_ Pyrolyysireaktori________ 2__Kuivuri__ _3__Poltin__ 4, 5__Leijupeti ___ 800 ° 0, 1.03 bar _6__Ylikuumennin__ J7__Esilämmitin__ J8__Ilman esilämmitin__ _9__Venttiili__ 10,11,12,13,14 Turbiini__ 15 __Vaihtovirtageneraattori 15.87 MW_ 16 __Lauhdutin_______ 17 __Pumppu 6.5 kW_ 18,19__Feed Water Heater _________ 20 _____ Pump__0.4 kW__ 22 __Feed Water Tank__ 23 __Pump__150 kW_ 24 __Sand Cooler _______ ... · 25_ Blower · * · 1 2 3 • 1 1 • • · ··· • 1 * · • · · · · · · · · · · · · · · · · · · · · · · · · · · · ··· «» * 1 • · · • 1 · • · · 2 * ·· 3 * · ’17 117574

Table 8 Parts of the equipment shown in the two-stage solid waste incineration flow diagram (Figure 3)

Reference (Figure 3) __ Device__Feature _1__Pyrolysis Reactor__ J2__Dryer__ 3__Burner__4005C, 1 bar 6, 7__Heat heater___8__Preheater___9__Air Preheater__ 10,15Vac13__

16 __Access generator 15.75 MW

17 __Condenser___ 18 __Pump_ 6 kW_ 19,20__Feed water heater _ 21__Pump__0.4 kW_ 23 __Feed water tank__

24 __Pumppu__0.131 MW

25 _____Sand Cooler _______ 26 _ Blower__

The present invention has been described above with reference to some exemplary embodiments thereof, but it will be apparent to one skilled in the art that the invention may also be embodied in many different ways within the scope of the appended claims.

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• H

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Claims (19)

117574 An apparatus for incinerating solid waste, characterized in that the apparatus comprises at least one first reactor (1) for removing hydrogen chloride from the waste and at least one second reactor (3, 4, 5) for incinerating waste, said first reactor (1) comprising means for recovering HCl. as liquid hydrochloric acid and at least one of these reactors being a fluidized bed reactor. 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. Apparatus according to either of the preceding claims, characterized in that said first reactor (1) comprises means for heating said waste to a temperature in the range of from 200 to 400 ° C, preferably from 300 to 400 ° C, most preferably from 350 to 400 ° C. Apparatus according to any one of the preceding claims, characterized in that said second reactor (3, 4, 5) comprises means for heating said waste in the range of 700 to 900 ° C, preferably 800 to 900 ° C, most preferably 840 to 860 ° C. . temperature. φ »* ι · 1 a a ···, '• * • · Apparatus according to any one of the preceding claims, characterized in that it *. that said apparatus comprises means for fluidizing the bed in said first reactor (1) and / or second reactor (3, 4, 5) with gas. aa. a · * * * * a a An apparatus according to any one of the preceding claims, characterized in that the apparatus comprises means for feeding a heat carrier, preferably a solid heat carrier, to said first reactor (1) and to said second reactor a · * ·· * (3, 4, 5) and for recycling said heat carrier from said second reactor (3,: Y: 4, 5) to said first reactor (1). • a * • · • · * * * a aa · a · · · · a aa a · aa • a 117574 Apparatus according to any one of the preceding claims, characterized in that said first reactor (1) has means for circulating gases other than HCl from said first reactor (1) to said second reactor (OM.5) · Apparatus according to any one of the preceding claims, characterized in that the dryer (2) is installed for drying all or part of the waste. Apparatus according to any one of the preceding claims, characterized in that said second reactor (3, 4, 5) is provided with means for recovering the heat of combustion to produce thermal and electric power. A process for incinerating solid waste, characterized in that the solid waste is dehydrogenated in at least one of the first reactors (1) and the dehydrogenated solid waste is burned in at least one of the second reactors (3, 4, 5), the first reactor (1) being discharged as liquid hydrochloric acid and the fluidization of at least one of these reactors comprising said waste. The process according to claim 10, characterized in that said removal of hydrogen chloride from the waste takes place at a temperature in the range 200-400 ° C, preferably 300-400 ° C, most preferably 350-400 ° C. • 1 1 · * · 'ttt' A process according to any one of claims 10 to 11, characterized in that said waste is incinerated in the range of 700 to 900 ° C, preferably in the range of 800 to 900 ° C, most preferably in the range of 840 to 860 ° C. a · · 't * .ί.1 A process according to any one of claims 10 to 12, characterized in that the fluidization is accomplished by supplying a fluidizing gas such as air or nitrogen · 1; 1; said reactors. »· ··· '• · • · ··· ti» • 1 1 ··· · ··· • · 117574 Process according to any one of claims 10 to 13, characterized in that the fluidized bed is obtained by feeding a solid heat carrier and circulating said solid heat carrier from one reactor to another in direct contact with said waste. Method according to any one of claims 10 to 14, characterized in that gases other than HCl are recycled as fuel for said combustion. Method according to any one of claims 10 to 15, characterized in that said waste contains PVC. Process according to any one of claims 10 to 16, characterized in that the removal of hydrogen chloride is continued until at least 60%, preferably 99%, most preferably 100% of hydrogen chloride is removed from the waste. Process according to any one of claims 10 to 17, characterized in that energy is recovered from the gases leaving said second reactor by means of heat exchangers. , 19. Use of solid chlorine-containing waste to produce usable energy • *. removing hydrogen chloride from the solid waste in at least one of the first reactors; * and incinerating this dehydrogenated solid waste in at least one of the second reactors, comprising removing the HCl gas released in said first reactor as liquid hydrochloric acid and fluidizing said waste in at least one of said reactors . • * * • • • • • • • • • • • • • • · · · · · · · · · · · · · · · · · · · · · · · · ··· •, '• f »··· 0 · ·« · ♦ · · · · · * 117574