PROCESS AND SYSTEM FOR PRODUCING A HYDROCARBON-CONTAINING AND HYDROGEN-CONTAINING GAS MIXTURE FROM PLASTIC

Abstract

The invention relates to a method and a system for producing a hydrocarbon- and hydrogen-containing gas mixture from plastics, and the use of the system for producing this gas mixture and the use of this gas mixture as a starting material in chemical syntheses or for gas supply.

Claims

1. A method for producing a hydrocarbon and hydrogen-containing gas mixture from plastics, comprising the following steps: A) pyrolysis of plastics to form a pyrolysis gas mixture; B) hot gas filtration for removal of solid particles; C) catalytic cracking to produce the hydrocarbon-containing and hydrogen-containing gas mixture; and D) gas wash of the hydrocarbon-containing and hydrogen-containing gas mixture, wherein between step A) and B) or between step B) and C) a further step A2) is carried out: A2) catalytic cracking of the pyrolysis gas mixture, wherein water vapor and air or oxygen are added during the catalytic cracking comprising steps C) and A2).

2. (canceled)

3. The method according to claim 1, wherein the plastics in step A) is selected from lightweight aluminium packaging and mixed plastics.

4. The method according to claim 1, wherein a separation of solids takes place in step A).

5. The method according to claim 1 wherein the pyrolysis in step A) is carried out at an oxygen content in the range of 0% (v/v) to 2% (v/v).

6. The method according to claim 1 wherein the pyrolysis in step A) is carried out at a temperature in the range of 300° C. to 600° C.

7. The method according to claim 1, wherein the pyrolysis in step A) is carried out at a negative pressure in the range of 0 mbar to 1 mbar relative to the external pressure.

8. The method according to claim 1 wherein the hot gas filtration in step B) is carried out at a temperature in the range of 500° C. to 600° C.

9. The method according to claim 1 wherein the catalytic cracking is carried out by means of a catalyst selected from limestone, zirconium dioxide (ZrO2), noble metal and nickel catalysts.

10. A system for producing a hydrocarbon-containing and hydrogen-containing gas mixture from plastics, comprising: a) a pyrolysis unit; b) a hot gas filter; c) a unit for catalytic cracking; and d) a gas scrubbing unit comprising: a2) a pre-reformer for catalytic cracking of the pyrolysis gas mixture, wherein the pre-reformer is arranged downstream of the a) pyrolysis unit or the b) hot gas filter, wherein the catalytic cracking unit c) and the catalytic cracking reformer a2) together have at least one inlet for water vapor and air or oxygen, for the production of a hydrocarbon and hydrogen-containing gas mixture from plastic wherein the at least one inlet at the unit for catalytic cracking c) and the pre-reformer for catalytic cracking a2) is used for the inlet of water vapor and air or oxygen.

11. (canceled)

12. The system according to claim 10 wherein the pyrolysis unit is a rotary kiln pyrolysis unit or a fluidised bed pyrolysis unit.

13. The system according to claim 10, wherein one or more of the connections between the system parts a) to c) can be heated.

14. The system according to claim 10, wherein the hot gas filter has filter cartridges made of aluminum silicate wool.

15. (canceled)

16. The method according to claim 1, wherein step B) is carried out using a hot gas filter wherein the hot gas filter has filter cartridges made of aluminum silicate wool.

17. (canceled)

18. (canceled)

19. (canceled)

20. (canceled)

Description

[0088] FIG. 1 shows the schematic structure of the system according to the invention in an exemplary embodiment.

[0089] In order to implement the invention, it is also expedient to combine the above-described embodiments and features of the claims.

EMBODIMENTS

[0090] The invention will be explained in greater detail below with reference to some embodiments and accompanying drawings. The embodiments are intended to describe the invention without limiting it.

[0091] Method when Using Aluminium Packaging Waste Containing Plastics:

[0092] Aluminium packaging waste with plastics (so-called composite material) was used as the plastics.

A) The material is input into the pyrolysis unit via a stuffing screw. The stuffing screw flight stops approximately 0.5 m before the end and the end is fitted with a weighted flap. The pyrolysis drum is an indirectly heated drum having four heating zones which can be controlled independently. The input and output of the pyrolysis unit are continuously flushed with nitrogen. A measurement of the oxygen content in the pyrolysis drum gives approximately 1%. The four heating zones cover a range of 380-520° C. The temperature measurement of the gas in the pyrolysis drum gives 480-540° C.

[0093] The pyrolysis drum has a bypass flap by means of which excess heat can be dissipated without heating the drum. The pressure in the pyrolysis unit is 0.2 mbar below the external pressure. The solid waste is output via a double pendulum flap which is designed as a sluice in order to prevent oxygen from entering the housing during the output. The waste (mainly metal) is cooled and mechanically processed. The obtained gas is conducted to the hot gas filter via heated pipes.

B) The gas is fed into the hot gas filter from below and passed through filter candles made of aluminium silicate wool. The dust becomes caught on the candles and the cleaned gas rises to the top. The container of the hot gas filter consists of stainless steel and is heated to 550° C. The dust is automatically removed via differential pressure-controlled cleaning with nitrogen. The filtered gas is in turn passed through a heated pipe for catalytic cracking.
C) The reformer used, i.e. the unit for catalytic cracking, is in two-stages. The inflowing gas mixture is enriched with air and conducted past a ZrO.sub.2 catalyst. The temperature of the gas in this case is between 850-900° C. After this first stage, steam is added to the gas and the gas is then conducted past a nickel-based fixed bed catalyst.

[0094] For the first time, the gas is then conducted via non-heated pipelines, specifically to the condenser, where it is cooled to 0° C. and a liquid phase condenses. This liquid phase no longer contains any oils, tars or phenols, and it therefore does not have to be incinerated as hazardous waste.

D) The gas is then conducted to the gas scrubbing unit. At approx. 0-10° C., the gas is first passed through a NaOH solution and next passed over pure water, in order to then be conducted for gas ultra-purification. There the gas is reheated and then condensed again in order to dry it again and to then pass it through an activated carbon bed.

[0095] Method with Additional Catalytic Cracking a2) Between the Pyrolysis and the Hot Gas Filtration:

[0096] The method is carried out as described above. Only the two-stage catalytic cracking in step C) is one-stage cracking, since catalytic cracking is now also carried out in step A2). The temperature of the gas in step A2) is 850-900° C. A fluidised bed reformer is used with a dolomite (fluidised limestone) catalyst. In addition, air and steam are added. In this case, the hot gas filtration is also carried out at 850-900° C., such that nothing condenses in the subsequent hot gas filtration. The remaining steps take place analogously.

[0097] The compositions of various gases listed below were determined using gas chromatography-MS.

[0098] Composition of the Pyrolysis Gas after Step A):

[0099] 1.3% H.sub.2, 7.8% CO.sub.2, 4.1% CO, 2.2% CH.sub.4, 1.3% O.sub.2, 72.4% N.sub.2, 7.5% hydrocarbons >C.sub.4, 3.4% hydrocarbons C.sub.2-C.sub.4.

[0100] Composition of the Hydrocarbon- and Hydrogen-Containing Gas Mixture from Step C):

[0101] 40% H.sub.2, 17% CO.sub.2, 5% CO, 7% CH.sub.4, 0.5% O.sub.2, 28% N.sub.2.

[0102] Method when Using Mixed Plastics Waste:

[0103] The method is carried out in the two variants, as mentioned above. The obtained gases have the following compositions:

[0104] Composition of the Pyrolysis Gas after Step A):

TABLE-US-00001 Sample numbering 1 2 3 4 5 6 7 vol. vol. vol. vol. vol. vol. vol. % % % % % % % CH.sub.4 2.9 2.7 2.4 2.9 2.6 2.7 3.0 H.sub.2 1.9 3.1 2.6 2.0 1.9 1.4 1.6 N.sub.2 71.8 68.6 70.0 70.5 72.4 72.7 70.5 O.sub.2 0.5 0.2 0.3 0.4 0.5 0.4 1.2 CO.sub.2 8.5 13.5 12.4 9.4 9.0 8.5 8.1 CO 7.1 3.8 4.0 6.2 6.5 6.8 6.7 C.sub.2H.sub.6 (ethane) 1.09 1.25 1.29 1.47 1.00 1.12 1.37 C.sub.2H.sub.4 (ethylene) 1.84 1.96 2.01 2.08 1.50 1.70 1.80 C.sub.3H.sub.8 (propane) 0.25 0.39 0.46 0.41 0.24 0.30 0.41 C.sub.3H.sub.6 (propylene) 1.51 1.71 1.88 2.01 1.29 1.47 1.82 iso-C.sub.4H.sub.10 (iso-butane) 0.00 0.00 0.00 0.00 0.00 0.00 0.00 n-C.sub.4H.sub.10 (n-butane) 0.04 0.07 0.09 0.07 0.04 0.05 0.08 C.sub.3H.sub.4 (propadiene) 0.00 0.01 0.01 0.00 0.00 0.00 0.00 C.sub.2H.sub.2 (acetylene) 0.01 0.09 0.08 0.00 0.00 0.00 0.00 C.sub.4H.sub.8 (trans-2-butene) 0.06 0.08 0.09 0.08 0.05 0.06 0.07 C.sub.4H.sub.8 (iso-butene) 0.00 0.50 0.51 0.40 0.25 0.26 0.38 C.sub.4H.sub.6 (1,3-butadiene) 0.08 0.13 0.12 0.10 0.07 0.07 0.08 C.sub.5H.sub.12 (iso-pentane) 0.00 0.00 0.00 0.00 0.00 0.00 0.00 C.sub.5H.sub.12 (pentane) 0.09 0.20 0.26 0.15 0.07 0.10 0.16 C.sub.5H.sub.10 (1-pentene) 0.10 0.05 0.05 0.04 0.09 0.11 0.15 C.sub.6H.sub.6 (benzene) 0.02 0.49 0.54 0.53 0.40 0.33 0.37 C.sub.7H.sub.8 (toluene) 0.02 0.02 0.03 0.04 0.03 0.03 0.03 Unidentifiable hydrocarbons: C4 hydrocarbons 0.00 0.00 0.00 0.00 0.00 0.00 0.00 C5 hydrocarbons 0.60 0.65 0.68 0.68 0.35 0.42 0.54 C6 hydrocarbons 0.82 0.75 0.94 0.80 0.50 0.55 0.73 C7 hydrocarbons 0.04 0.06 0.10 0.09 0.06 0.07 0.08

[0105] Various samples were also analysed for H.sub.2S, polyaromatic hydrocarbons, chlorine and ammonia:

TABLE-US-00002 Sample i ii iii iv v vol. ppm vol. ppm vol. ppm vol. ppm vol. ppm H.sub.2S 5 6 12 5 8

[0106] The samples contained, inter alia, the following amounts of polyaromatic hydrocarbons (PAH). These values were determined by means of gas chromatography-MS (g/man=grams per m.sup.3 standard condition—0° C. and 101.325 kPa).

TABLE-US-00003 Sample I II III IV V VI g/m.sup.3n g/m.sup.3n g/m.sup.3n g/m.sup.3n g/m.sup.3n g/m.sup.3n Benzene 16 9 10 15 12 11 Light tars 99 82 123 140 153 132 (<naphthalene) Naphthalene 1 1 2 2 2 2 Heavy tars 21 49 85 99 87 66 (>naphthalene) Carbon black 6 44 21 10 1 2 Water 208 136 181 190 755 230 Sample x Reference/zero sample mg/l mg/l Chlorine (HCl) 278 0.22 Sample y z mg/l mg/l NH.sub.3 64 109

[0107] Composition of the Hydrocarbon- and Hydrogen-Containing Gas Mixture from Step C) and Step D):

[0108] In addition to nitrogen, hydrogen, oxygen, carbon dioxide and carbon monoxide, the samples contained the following hydrocarbons, inter alia:

TABLE-US-00004 Sample m n o p ppm ppm ppm ppm CH.sub.4 40,196 43,334 73,747 70,944 C.sub.2H.sub.6 (ethane) 2,234 683 2,012 2,169 C.sub.2H.sub.4 (ethylene) 40,700 18,329 83,247 50,523 C.sub.3H.sub.8 (propane) 226 2 97 49 C.sub.3H.sub.6 (propylene) 7,568 418 3,948 5,265 iso-C.sub.4H.sub.10 (iso-butane) 7 0 1 0 n-C.sub.4H.sub.10 (n-butane) 37 0 0 1 C.sub.3H.sub.4 (propadiene) 36 48 3,931 1,973 C.sub.2H.sub.2 (acetylene) 82 857 0 0 C.sub.4H.sub.8 (trans-2-butene) 176 1 16 21 C.sub.4H.sub.8 (iso-butene) 2,141 15 15 399 C.sub.4H.sub.6 (1,3-butadiene) 1,689 108 1,416 1,706 C.sub.5H.sub.12 (iso-pentane) 2 0 0 0 C.sub.5H.sub.12 (pentane) 111 1 8 0 C.sub.5H.sub.10 (1-pentene) 883 0 1 1 C.sub.6H.sub.6 (benzene) 949 4,016 9,535 6,737 C.sub.7H.sub.8 (toluene) 430 301 1,054 1,248 C.sub.6H.sub.12 (cyclohexane) 3 18 167 112 C.sub.7H.sub.14 (methylcyclohexane) 5 0 1 2 Unidentifiable hydrocarbons: C4 hydrocarbons 1,741 2 562 339 C5 hydrocarbons 968 64 513 552 C6 hydrocarbons 4,662 34 421 388 C7 hydrocarbons 914 8 902 102

[0109] Obtained Conversions:

[0110] The conversion is calculated on the basis of the molar volume for ideal gases of 22.4 l/mol. This means that, from the volume of the relevant gas in the hydrocarbon- and hydrogen-containing gas mixture obtained in the method, the substance amount is calculated in mol by means of this molar volume of 22.4 l/mol, which substance amount can in turn be converted into the mass of the gas by means of the molar mass of the gas. The sum of the masses of the individual contained gases is set in relation to the mass of the plastics used, and the conversion is thus obtained.

[0111] The conversion was 95%, 92.5% and 98% in the individual experiments.

LIST OF REFERENCE SIGNS

[0112] a) pyrolysis unit [0113] b) hot gas filter [0114] c) unit for catalytic cracking [0115] d) condenser [0116] e) gas scrubbing unit [0117] 1 plastics input [0118] 2 output of non-pyrolysable solids (metal) [0119] 3 heated pipes [0120] 4 output of the hydrocarbon- and hydrogen-containing gas mixture