US20110147193A1

US20110147193A1 - Coal reforming plant

Info

Publication number: US20110147193A1
Application number: US12/691,290
Authority: US
Inventors: Setsuo Omoto; Shinya Tachibana; Fumiaki Sato
Original assignee: Mitsubishi Heavy Industries Ltd
Current assignee: Mitsubishi Heavy Industries Ltd
Priority date: 2009-12-18
Filing date: 2010-01-21
Publication date: 2011-06-23
Also published as: WO2011074279A1; JP2011127010A

Abstract

A coal reforming plant includes: a drying combustor for generating drying combustion gas; a dryer for drying low-grade coal introduced into an inside thereof with the combustion gas from the drying combustor being supplied to the inside thereof; a pyrolysis combustor for generating pyrolysis combustion gas; a pyrolyzer for pyrolyzing dried coal with the combustion gas from the pyrolysis combustor being supplied to an inside thereof; a circulating blower for supplying part of pyrolysis gas and pyrolysis oil in gaseous form generated in the pyrolyzer to the pyrolysis combustor; a cooling tower and the like for cooling the other part of the pyrolysis gas and the pyrolysis oil in gaseous form generated in the pyrolyzer, and thus separating the other part into the pyrolysis gas and the pyrolysis oil in liquid form; a circulating blower for supplying the pyrolysis gas separated from the pyrolysis oil in the cooling tower to the drying combustor; and the like.

Description

TECHNICAL FIELD

The present invention relates to a coal reforming plant for reforming coal by drying and pyrolyzing it. The present invention is particularly effective when applied to reformation of low-grade coals containing much moisture such as lignite, sub-bituminous coal, and the like.

BACKGROUND ART

Though there are abundant reserves of low-grade coals containing much moisture such as lignite, sub-bituminous coal, and the like, such low-grade coal has a low heating value per unit weight and has poor transport efficiency. For this reason, the low-grade coal is heated and dried to increase the heating value per unit weight, and is compression-molded to improve the handling capability.
FIG. 2 shows a schematic configuration of a conventional coal reforming plant for reforming such low-grade coal (see, for example, Patent Literature 1 below).
As shown in FIG. 2, a supply port of a hopper 11 for supplying low-grade coal 1 is connected to a receiving port of a dryer 12 for drying the low-grade coal 1. An outlet port of this dryer 12 is connected to a receiving port of a pyrolyzer 13 for pyrolyzing dried coal 2. An outlet port of this pyrolyzer is connected to a receiving port of a molder 14 for compression-molding pyrolysis coal 3.
A gas exhaust port of the pyrolyzer 13 is connected to a gas receiving port of a cooling tower 15 for separating and recovering gaseous pyrolysis oil 6, which is generated from the dried coal 2 by the pyrolysis, from pyrolysis gas 5. A gas outlet port of this cooling tower 15 is connected to a receiving port of a circulating blower 19. An outlet port of this circulating blower 19 is connected to both a drying combustor 20 and a pyrolysis combustor 21.
On the other hand, a lower part of the cooling tower 15 is connected to a receiving port of a circulating pump 16. An outlet port of this circulating pump 16 is connected via a heat exchanger 17 to a spray nozzle 18 provided in an upper part of an inside of the cooling tower 15, and is also connected to both the drying combustor 20 and the pyrolysis combustor 21 as well as the outside of the system.
A gas outlet port of the pyrolysis combustor 21 is connected to a gas receiving port of the pyrolyzer 13. A pyrolysis combustor bypass line 21 a is provided between the outlet port of the circulating blower 19 and the gas receiving port of the pyrolyzer 13 for establishing circulation bypassing the pyrolysis combustor 21. A flow control valve 21 b is provided in this pyrolysis combustor bypass line 21 a.
A gas outlet port of the drying combustor 20 is connected to a gas receiving port of the dryer 12. A drying combustor bypass line 20 a is provided between the outlet port of the circulating blower 19 and the gas receiving port of the dryer 12 for establishing circulation bypassing the drying combustor 20. A flow control valve 20 b is provided in this drying combustor bypass line 20 a. A gas outlet port of the dryer 12 is connected to a receiving port of a circulating blower 22. An outlet port of this circulating blower 22 is connected to the gas receiving port of the dryer 12, and is also connected to the outside of the system.
In this conventional coal reforming plant 10, once the low-grade coal 1 is introduced into the hopper 11, the hopper 11 dispenses the low-grade coal 1 to the dryer 12. The low-grade coal 1 supplied to the dryer 12 is heated by combustion gas 7 (about 150° C. to 350° C.) sent from the drying combustor 20, so that moisture is removed from the low-grade coal 1. The low-grade coal 1 is thereby turned into the dried coal 2, which is conveyed to the pyrolyzer 13. The dried coal 2 conveyed to the pyrolyzer 13 is heated and pyrolyzed by the combustion gas 7 (about 350° C. to 550° C.) sent from the pyrolysis combustor 21, so that components such as the pyrolysis gas 5, the pyrolysis oil 6 and the like, are removed from the dried coal 2. The dried coal 2 is thereby turned into the pyrolysis coal 3, which is then supplied to the molder 14. The pyrolysis coal 3 supplied to the molder 14 is compression-molded and turned into reformed coal 4 in the form of briquettes, or the like.
On the other hand, the pyrolysis gas 5 and the gaseous pyrolysis oil 6 (about 300° C. to 500° C.) generated in the pyrolyzer 13 are supplied along with the combustion gas 7 to the cooling tower 15 and cooled by the liquid pyrolysis oil 6 (about 60° C.), which is sprayed from the spray nozzle 18, thereby being recovered in a liquid form in a bottom part of the cooling tower 15. This pyrolysis oil 6 (about 80° C. to 120° C.) recovered in the bottom part of the cooling tower 15 is withdrawn by the circulating pump 16, so that part of the pyrolysis oil 6 is supplied to the drying combustor 20 and the pyrolysis combustor 21, whereas the other remaining part thereof is heat-exchanged with heat-exchange water in a heat-exchanger 17 to be cooled (about 60° C.), and is then sprayed from the spray nozzle 18 to be utilized for cooling the gaseous pyrolysis oil 6. Then, because the amount of the pyrolysis oil 6 recovered in the cooling tower 15 gradually increases and becomes too much, an appropriate amount of the pyrolysis oil 6 is appropriately withdrawn to the outside of the system and disposed.
On the other hand, the pyrolysis gas 5 (about 60° C. to 80° C.) separated from the pyrolysis oil 6 is supplied along with the combustion gas 7 to both the drying combustor 20 and the pyrolysis combustor 21 by the circulating blower 19 and combusted with the pyrolysis oil 6, so that it is turned into the combustion gas 7, which is then supplied to both the dryer 12 and the pyrolyzer 13 and used for drying (about 150° C. to 350° C.) and pyrolysis (about 350° C. to 550° C.), respectively.
A part (increment due to the combustion in the combustors 20 and 21) of the combustion gas 7 (about 90° C. to 150° C.) used for drying in the dryer 12 is exhausted to the outside of the system by the circulating blower 22, and the other remaining part thereof is supplied to the dryer 12 again and reused along with the combustion gas 7 from the drying combustor 20.
It should be noted that the temperature of the combustion gas 7 from the combustors 20 and 21 is controlled by adjusting the degrees of opening of the valves 20 b and 21 b so that the combustion gas 7 should not be combusted in the combustors 20 and 21 but flow through the bypass lines 20 a and 21 a. On the other hand, the supply of the pyrolysis oil 6 to the pyrolysis combustor 21 is reduced or cut off when only the pyrolysis gas 5 supplied to the pyrolysis combustor 21 can provide a sufficient amount of heat.

CITATION LIST

Patent Literature

{Patent Literature 1} U.S. Pat. No. 5,401,364

SUMMARY OF INVENTION

Technical Problem

In the conventional coal reforming plant 10 as described above, after the pyrolysis gas 5 and the gaseous pyrolysis oil 6 (about 300° C. to 500° C.) generated in the pyrolyzer 13 are cooled in the cooling tower 15 to separate the pyrolysis oil 6, the pyrolysis gas 5 (about 60° C. to 80° C.) is supplied to the drying combustor 20 and the pyrolysis combustor 21 to generate the drying combustion gas 7 (about 150° C. to 350° C.) and the pyrolysis combustion gas 7 (about 350° C. to 550° C.), respectively. In other words, because the combustion gas 7 having high temperatures is generated from the pyrolysis gas 5 once cooled to separate the gaseous pyrolysis oil 6, waste of thermal energy is generated.
In view of the above problem, it is an object of the present invention to provide a coal reforming plant that can utilize thermal energy more effectively than in the conventional plant, thereby improving thermal efficiency.

Solution to Problem

A coal reforming plant according to a first invention for solving the above-described problem includes: drying combustion gas generating means for generating drying combustion gas; drying means for drying coal introduced into an inside thereof with the combustion gas from the drying combustion gas generating means being supplied to the inside thereof; pyrolysis combustion gas generating means for generating pyrolysis combustion gas; pyrolysis means for pyrolyzing dried coal with the combustion gas from the pyrolysis combustion gas generating means being supplied to an inside thereof, the dried coal being dried in the drying means; pyrolysis fuel supply means for supplying part of pyrolysis gas and pyrolysis oil in gaseous form generated in the pyrolysis means to the pyrolysis combustion gas generating means; pyrolysis oil separating means for cooling the other part of the pyrolysis gas and the pyrolysis oil in gaseous form generated in the pyrolysis means, and thus separating the other part into the pyrolysis gas and the pyrolysis oil in liquid form; and drying fuel supply means for supplying the pyrolysis gas separated from the pyrolysis oil in the pyrolysis oil separating means to the drying combustion gas generating means.
A coal reforming plant according a second invention is the coal reforming plant, according to the first invention, in which the drying fuel supply means supplies part of the pyrolysis gas from the pyrolysis oil separating means to the drying combustion gas generating means, and the coal reforming plant further comprises power generating means for generating power by using the other part of the pyrolysis gas from the pyrolysis oil separating means.
A coal reforming plant according a third invention is the coal reforming plant, according to any one of the first and second inventions, further including drying combustion gas circulating means for supplying the combustion gas exhausted from the inside of the drying means to the drying means again.
A coal reforming plant according a fourth invention is the coal reforming plant, according to any one of the first to third inventions, further including molding means for compression-molding pyrolysis coal obtained by the pyrolysis in the pyrolysis means.

ADVANTAGEOUS EFFECTS OF INVENTION

In the coal reforming plant according to the present invention, part of the mixture of the pyrolysis gas and the pyrolysis oil in gaseous form is not cooled but is used with the pyrolysis oil in gaseous form still included in the part to generate the pyrolysis combustion gas. Accordingly, the amount of the pyrolysis gas and the gaseous pyrolysis oil to be used for obtaining a required amount of thermal energy to generate the pyrolysis combustion gas can be made smaller than that in the conventional art. Therefore, thermal energy can be utilized more effectively to improve thermal efficiency than in the conventional art.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a schematic configuration diagram of a principal embodiment of a coal reforming plant according to the present invention.

FIG. 2 shows a schematic configuration diagram of an example of a conventional coal reforming plant.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of a coal reforming plant according to the present invention will be described with reference to the drawings, though the present invention is not limited to the embodiments described with reference to the drawings.

Principal Embodiment

A principal embodiment of the coal reforming plant according to the present invention will be described with reference to FIG. 1.
As shown in FIG. 1, a supply port of a hopper 111 that is coal supply means for supplying low-grade coal 1 is connected to a receiving port of a dryer 112 that is drying means for drying the low-grade coal 1. An outlet port of this dryer 112 is connected to a receiving port of a pyrolyzer 113 that is pyrolysis means for pyrolyzing dried coal 2. An outlet port of this pyrolyzer 113 is connected to a receiving port of a molder 114 that is molding means for compression-molding pyrolysis coal 3.
A gas exhaust port of the pyrolyzer 113 is connected to a gas receiving port of a cooling tower 115 for separating and recovering gaseous pyrolysis oil 6 generated from the dried coal 2 by the pyrolysis, from pyrolysis gas 5, and is also connected to a gas receiving port of a circulating blower 123 that is pyrolysis fuel supply means. A gas outlet port of this circulating blower 123 is connected to a pyrolysis combustor 121 that is pyrolysis combustion gas generating means. A gas outlet port of the cooling tower 115 is connected to a receiving port of a circulating blower 119 that is drying fuel supply means. An outlet port of this circulating blower 119 is connected to a drying combustor 120 that is drying combustion gas generating means, and is also connected to an independent power generation boiler 124 that is power generating means. This independent power generation boiler 124 is connected to an independent power plant 125 including a steam turbine and the like.
In addition, a lower part of the cooling tower 115 is connected to a receiving port of a circulating pump 116. An outlet port of this circulating pump 116 is connected to a spray nozzle 118 via a heat exchanger 117, and is also connected to the outside of the system.
A gas outlet port of the pyrolysis combustor 121 is connected to a gas receiving port of the pyrolyzer 113. A pyrolysis combustor bypass line 121 a for establishing circulation bypassing the pyrolysis combustor 121 is provided between the outlet port of the circulating blower 123 and the gas receiving port of the pyrolyzer 113. A flow control valve 121 b is provided in this pyrolysis combustor bypass line 121 a.
A gas outlet port of the drying combustor 120 is connected to a gas receiving port of the dryer 112. A drying combustor bypass line 120 a for establishing circulation bypassing the drying combustor 120 is provided between the outlet port of the circulating blower 119 and the gas receiving port of the dryer 112. A flow control valve 120 b is provided in this drying combustor bypass line 120 a.
A gas outlet port of the dryer 112 is connected to a receiving port of a circulating blower 122 that is drying combustion gas circulating means. An outlet port of this circulating blower 122 is connected to the gas receiving port of the dryer 112, and is also connected to the outside of the system.
In this embodiment, the cooling tower 115, the circulating pump 116, the heat exchanger 117, the spray nozzle 118 and the like constitute pyrolysis oil separating means.
In the coal reforming plant 100 according to this embodiment, once the low-grade coal 1 is introduced into the hopper 111, the hopper 111 dispenses the low-grade coal 1 to the dryer 112. The low-grade coal 1 supplied to the dryer 112 is heated by drying combustion gas 7 (about 150° C. to 350° C.) sent from the drying combustor 120, so that moisture is removed from the low-grade coal 1. The low-grade coal 1 is thereby turned into the dried coal 2, which is conveyed to the pyrolyzer 113. The dried coal 2 conveyed to the pyrolyzer 113 is heated and pyrolyzed by pyrolysis combustion gas 7 (about 350° C. to 550° C.) sent from the pyrolysis combustor 121, so that components such as the pyrolysis gas 5, the pyrolysis oil 6 and the like are removed from the dried coal 2. The dried coal 2 is thereby turned into the pyrolysis coal 3, which is then supplied to the molder 114. The pyrolysis coal 3 supplied to the molder 114 is compression-molded and turned into reformed coal 4 in the form of briquettes, or the like.
On the other hand, part of the pyrolysis gas 5 and the gaseous pyrolysis oil 6 (about 300° C. to 350° C.) generated in the pyrolyzer 113 is supplied along with the combustion gas 7 to the pyrolysis combustor 121 by the circulating blower 123 and combusted in the pyrolysis combustor 121, thereby being turned into the pyrolysis combustion gas 7 (about 350° C. to 550° C.), which is then supplied to the pyrolyzer 113.
Then, the other remaining part is supplied to the cooling tower 115 and cooled by the liquid pyrolysis oil 6 (about 60° C.) sprayed from the spray nozzle 118, and is recovered in a liquid form in a bottom part of the cooling tower 115. The pyrolysis oil 6 (about 80° C. to 120° C.) recovered in the bottom part of the cooling tower 115 is withdrawn by the circulating pump 116 and heat-exchanged with heat-exchange water in the heat-exchanger 117 to be cooled (about 60° C.). Then, the cooled pyrolysis oil 6 is sprayed from the spray nozzle 118 to be utilized for cooling the gaseous pyrolysis oil 6. Then, because the amount of the pyrolysis oil 6 recovered in the cooling tower 115 gradually increases and becomes too much, an appropriate amount of the pyrolysis oil 6 is appropriately withdrawn to the outside of the system.
Moreover, part of the pyrolysis gas 5 (about 60° C. to 80° C.) separated from the pyrolysis oil 6 is supplied along with the combustion gas 7 to the drying combustor 120 by the circulating blower 119 and combusted in the drying combustor 120, thereby being turned into the drying combustion gas 7 (about 150° C. to 350° C.), which is then supplied to the dryer 112.
Then, the other remaining part is supplied to the independent power generation boiler 124 and combusted as fuel and, then, is exhausted as the combustion gas 7 to the outside of the system. Steam generated in the independent power generation boiler 124 is supplied to the independent power plant 125 to drive the steam turbine, thereby generating electric power. This electric power generated in the independent power plant 125 is used in electric-powered devices in this plant 100 and surplus electric power is sold.
A part (increment due to the combustion in the drying combustor 120) of the combustion gas 7 (about 90° C. to 150° C.) used for drying in the dryer 112 is exhausted to the outside of the system by the circulating blower 122 and the other remaining part is supplied to the dryer 112 again and reused along with the combustion gas 7 from the drying combustor 120.
The temperature of the combustion gas 7 from the combustors 120 and 121 is controlled by adjusting the degrees of opening of the valves 120 b and 121 b so that the combustion gas 7 should not be combusted in the combustors 120 and 121 but flow through the bypass lines 120 a and 121 a.
Thus, in the conventional coal reforming plant 10 described above, the mixture of the pyrolysis gas 5 and the gaseous pyrolysis oil 6 (about 300° C. to 500° C.) is entirely cooled to separate the pyrolysis oil 6 and, then, the pyrolysis gas 5 (about 60° C. to 80° C.) is utilized to generate the pyrolysis combustion gas 7 (about 350° C. to 550° C.). On the other hand, in the coal reforming plant 100 according to the embodiment, part of the mixture of the pyrolysis gas 5 and the gaseous pyrolysis oil 6 (about 300° C. to 500° C.) is not cooled, but the pyrolysis gas 5 still including the gaseous pyrolysis oil 6 is used to generate the pyrolysis combustion gas 7 (about 350° C. to 550° C.).
For this reason, in the coal reforming plant 100 according to the embodiment, the usage amount of thermal energy of the pyrolysis gas 5 and the pyrolysis oil 6 required to generate the pyrolysis combustion gas 7 (about 350° C. to 550° C.) can be made smaller (for example, about 32 Gcal/h) than that in the conventional art (for example, about 56 Gcal/h).
Therefore, in the coal reforming plant 100 according to the embodiment, thermal energy can be utilized more effectively to improve thermal efficiency than in the conventional art.
Further, because the usage amount of thermal energy of the pyrolysis gas 5 and the pyrolysis oil 6 required to generate the pyrolysis combustion gas 7 (about 350° C. to 550° C.) can be made smaller than that in the conventional art, not only the pyrolysis gas 5 separated and recovered in the cooling tower 115 can be utilized in the drying combustor 120, but also the surplus pyrolysis gas 5 (for example, about 58 Gcal/h) can be burned in the independent power generation boiler 124 to be utilized as energy to drive the independent power plant 125 (about 10 MW), in turn covering the operation of the electric-powered devices in this plant 100. Furthermore, the surplus electric power can be sold, so that the operating cost can be reduced.
Furthermore, because the other remaining part of the mixture of the pyrolysis gas 5 and the gaseous pyrolysis oil 6 (about 300° C. to 500° C.) is cooled in the cooling tower 115, the disposed thermal energy can be significantly reduced (for example, about 7 Gcal/h) in comparison with that in the conventional art (for example, about 49 Gcal/h) and, as a result, capacity of the cooling tower 115, the circulating pump 116 and the heat exchanger 117 can be reduced. As a result, cost and installation space of the cooling tower 115, the circulating pump 116 and the heat exchanger 117 can also be significantly reduced.
Performance data of the coal reforming plant 100 according to this embodiment and the conventional coal reforming plant 10 will be shown in Table 1 below.

	TABLE 1

		Conventional
	Embodiment	Example

Amount of Moisture in Low-grade Coal	6208	6208
(Wt %)
Amount of Low-grade Coal Processed	39	39
(wet-ton/day)
Amount of Reformed Coal Produced	3109	3109
(dry-ton/day)
Amount of Gas at Inlet of Dryer (Nm³/time)	840000	840000
Amount of Combustion Heat of	57.1	57.1
Drying Combustor (Gcal/hour)
Amount of Pyrolysis Oil Combusted in	0	1.5
Drying Combustor (ton/hour)
Amount of Gas at Inlet of Pyrolyzer	817000	817000
(Nm³/hour)
Amount of Combustion Heat of	32	56
Pyrolysis Combustor (Gcal/hour)
Amount of Pyrolysis Oil Combusted in	35.5	0
Pyrolysis Combustor (ton/hour)
Amount of Gas Flowing into Cooling Tower	82090	862570
(Nm³/hour)
Amount of Pyrolysis Oil Recovered	196	230
(ton/day)
Amount of Heat of Recovered Pyrolysis Oil	89	105
(Gcal/hour)
Amount of Heat Exchanged in Heat	7	49
Exchanger for Cooling Pyrolysis Oil
(Gcal/hour)
Amount of Heat of Surplus Pyrolysis Gas	58	0
(Gcal/hour)
Thermal Efficiency (%)	91.57	84.85

As is clear from Table 1 above, it can be observed that the coal reforming plant 100 according to this embodiment can improve thermal efficiency in comparison with the conventional coal reforming plant 10.

INDUSTRIAL APPLICABILITY

The coal reforming plant according to the present invention can utilize thermal energy more effectively than the conventional art and improve thermal efficiency. Therefore, it can be applied to industry very usefully.

REFERENCE SIGNS LIST

- 1 LOW-GRADE COAL
- 2 DRIED COAL
- 3 PYROLYSIS COAL
- 4 REFORMED COAL
- 5 PYROLYSIS GAS
- 6 PYROLYSIS OIL
- 7 COMBUSTION GAS
- 100 COAL REFORMING PLANT
- 111 HOPPER
- 112 DRYER
- 113 PYROLYZER
- 114 MOLDER
- 115 COOLING TOWER
- 116 CIRCULATING PUMP
- 117 HEAT EXCHANGER
- 118 SPRAY NOZZLE
- 119 CIRCULATING BLOWER
- 120 DRYING COMBUSTOR
- 121 PYROLYSIS COMBUSTOR
- 122 CIRCULATING BLOWER
- 123 CIRCULATING BLOWER
- 124 INDEPENDENT POWER GENERATION BOILER
- 125 INDEPENDENT POWER PLANT

Claims

1. A coal reforming plant comprising:

drying combustion gas generating means for generating drying combustion gas;

drying means for drying coal introduced into an inside thereof with the combustion gas from the drying combustion gas generating means being supplied to the inside thereof;

pyrolysis combustion gas generating means for generating pyrolysis combustion gas;

pyrolysis means for pyrolyzing dried coal with the combustion gas from the pyrolysis combustion gas generating means being supplied to an inside thereof, the dried coal being dried in the drying means;

pyrolysis fuel supply means for supplying part of pyrolysis gas and pyrolysis oil in gaseous form generated in the pyrolysis means to the pyrolysis combustion gas generating means;

pyrolysis oil separating means for cooling the other part of the pyrolysis gas and the pyrolysis oil in gaseous form generated in the pyrolysis means, and thus separating the other part into the pyrolysis gas and the pyrolysis oil in liquid form; and

drying fuel supply means for supplying the pyrolysis gas separated from the pyrolysis oil in the pyrolysis oil separating means to the drying combustion gas generating means.

2. The coal reforming plant according to claim 1, wherein

the drying fuel supply means supplies part of the pyrolysis gas from the pyrolysis oil separating means to the drying combustion gas generating means, and

the coal reforming plant further comprises power generating means for generating power by using the other part of the pyrolysis gas from the pyrolysis oil separating means.

3. The coal reforming plant according to claim 1, further comprising drying combustion gas circulating means for supplying the combustion gas exhausted from the inside of the drying means, to the drying means again.

4. The coal reforming plant according to claim 1, further comprising molding means for compression-molding pyrolysis coal obtained by the pyrolysis in the pyrolysis means.

5. The coal reforming plant according to claim 2, further comprising drying combustion gas circulating means for supplying the combustion gas exhausted from the inside of the drying means, to the drying means again.

6. The coal reforming plant according to claim 2, further comprising molding means for compression-molding pyrolysis coal obtained by the pyrolysis in the pyrolysis means.

7. The coal reforming plant according to claim 3, further comprising molding means for compression-molding pyrolysis coal obtained by the pyrolysis in the pyrolysis means.

8. The coal reforming plant according to claim 4, further comprising molding means for compression-molding pyrolysis coal obtained by the pyrolysis in the pyrolysis means.