Patent Application
20110005135
This invention is related to a gasifier which is used to recover gas from waste by thermally processing the waste and is also related to gasification methods using this gasifier. Specifically, this invention is related to gasification methods realized using this gasifier in which switching between downdraft and updraft modes can be realized without any interruptions according to the feedstock material introduced and the gas recovered, for which the gasification realized under vacuum conditions with high efficiency.
In prior art, downdraft and updraft gasifies were used for waste gasification. Either downdraft gasifiers or updraft gasifiers or even the up/downdraft gasifiers are used. However, it is not possible to switch from one mode to another without shutting down the process.
In prior art, WO2005/047435 discloses an up/downdraft gasifier. However this reference does not include any disclosure regarding the smooth switching between the systems without interrupting the process.
In US 2007/169411 a circulating bed up/downdraft gasifier has been disclosed. However, it is not easy to maintain the inside temperature at a fixed rate with this circulating bed gasifier. Since the reduction reactions will not be regulated, sudden changes in gas output will be very high.
In WO2007/081296 which belongs to the owner of the present application, it is disclosed that ash and tar production is high in circulating bed up/downdraft gasifies compared to fix bed up/downdraft gasifiers. During the suction of the gas, partially un-processed feedstock will come out along with and the pyrolytic operation will not be proper. In addition to that, since the unprocessed feedstock will leak from the gasifier, full process may not be realized.
Selection of the downdraft or the updraft operation mode in a gasifier depends on the feedstock to be introduced and type, the quality of the output gas. This present gasifier provides smooth switching between modes without interrupting the process.
One of the objects of this invention is to provide modular solutions instead of huge plants at geographical areas where the access is difficult by processing in an environmentally sound manner the refuse-derived-fuel (RDF) obtained from waste including hazardous, industrial and municipal waste.
Another object of this invention is to let the smooth transfer between modes without interrupting the process. Therefore energy, labor and time saving is realized via the invented gasifier and the gasification method.
Another object of this invention is to obtain a gasifier and a gasification method which decreases pollution in the output gas and increases the hydrogen content.
Another object of this invention is to obtain a gasifier and a gasification method which prevent the solidification of feedstock and clinker formation within the reactor and provides continuous gas production.
Below is the detailed description of this gasifier and the gasification method in order to reach the objects. Particular technical terminology used in text is explained herebelow.
Gasification: It is the chemical transformation of organic solid and liquid waste in syngas in an environment at 800-1200° C. with partial oxidation.
Incineration: It is the combusting process of municipal solid waste at a temperature of 1200-1600° C. within full oxygen environment. Some of the differences between gasification and incineration are:
in incineration hydrogen and oxygen combine and form vapour whereas in gasification the vapour is cracked in this 2 molecules.
CO2 is to be formed in incineration, whereas CO in gasification
a) The incineration process mainly forms carbon monoxide and vapor. These are waste gases and are let into the atmosphere. However, the syngas formed in gasification process is mainly formed of hydrogen and carbon monoxide gases. The syngas is not a waste gas. This can be used in burners, in gas turbines or in internal combustion engines for electrical energy production.
b) Incineration forms complex molecules containing poisonous materials such as dioxins and furans. Whereas gasification transforms complex molecules into gases with simpler molecule formation and prevents the formation of poisonous compounds such as dioxins and furans.
Pyrolysis: It is the thermal degradation of solid waste at 500-600° C. and in no oxygen containing environment. The syngas formed mainly contains hydrogen, carbon monoxide, carbon dioxide, methane and tar including complex hydrocarbons. This gas mixture can be used in burners for burning purposes, in gas turbines and internal combustion engines for electrical energy generation or coal and active carbon production.
The invention will be described herebelow with reference to the attached drawings in which
A gasifier (1) and gasification methods have been developed in order to reach the objects as mentioned above and to eliminate disadvantages of the prior art. With reference to
the present gasifier (1) comprises a scale (9.2),
A bottleneck zone (2) that comprises a double sliding valve (9) and a rotating valve (9.1) where the waste is exposed to heat for the first time in oxygen free environment;
A drying zone (3.1) located under the bottleneck zone (2) with a diameter bigger than the bottleneck zone comprising a higher syngas outlet zone (3.2), a safety valve (11), a level indicator (12), an inspection glass (12.1), a sliding cover (12.2), a thermocouple (13.2), a pressure forwarder (14), a pressure meter in syngas outlet zone, a proportional valve (19) and a hydraulic piston (21);
a pyrolysis zone (4) located under the drying zone (3) comprising a preheated air and oxygen inlet (4.1), air nozzles (4.4), a vibrator (10), a thermocouple (13.1), liquid hazardous waste injection nozzles (20), a proportional valve for hazardous liquid waste (20.1);
a cambered oxidation zone (5) comprising top air nozzles (4.2), bottom air nozzles (4.3), an air chamber (4.7), a bottom syngas outlet zone (6.1), proportional valve for air and oxygen inlet (6.3), igniters (8), a temperature meter in first oxidation zone (13), a pressure meter (14.1) at the syngas outlet zone;
a reduction zone (6) interior surface of which is covered with refractory material to prevent heat dissolvement comprising upper air nozzles (4.5), lower air nozzles (4.6), an air chamber (4.8), lower preheated air or oxygen inlet (6.2), proportional valve (6.4) for air or oxygen inlet, an ash grate (7.1) at the gas outlet zone for creating centrifugal effect, vapour nozzles (7.2) for increasing the carbon monoxide and hydrogen amount to enrich syngas, an igniter (8.1), igniting system (10.1) for the arc formation, a thermocouple (13.3), a vapour proportional valve (15) for regulating the vapour percentage;
an ash section (7) comprising ash discharger (7.3), an ash pool (22), a first threaded carrier (22.1) to convey big particles from ash discharger into the ash pool, a second threaded carrier (22.2), an ash carrying palette (22.3);
a precooler and scrubber system (23) placed between the gasifier reactor and fan and comprising a cyclone, syngas vapor exchanger, a gas cleaning scrubber and an electro static precipitator at least one fan (24); and valves (17, 18).
The gasifier permits the switching between downdraft and updraft modes without any interruption during the gasification process according to the feedstock material and the gas produced.
The gasifier (1) contains the an ash section (7) and at least one ash discharger in order to create centrifugal effect, at least one ash pool (22), at least one first threaded carrier (22.1) which conveys big particles coming from ash discharger into ash pool, at least one second threaded carrier (22.2), at least one ash carriage palette (22.3), at least one dry ash pool (22.4). The second carrier (22.2), axially rotates and carries small particles of ash accumulated at the bottom and popped to the surface through the ash carrying palette (22.3) into the dry ash pool (22.4).
The double sliding valve (9) located at the bottleneck zone prevents the leakage and moves horizontally back and forth reciprocally. It is formed of two valves located as one on top of the other one and which is driven by a hydraulic piston.
When the sliding valve (9.1) is open the RDF weighted on the scale (9.2) which is commonly used, is loaded. The sliding valve (9.1) is closed and the lower part of the valve is opened and the RDF is let into the gasifier. With the vacuum effect, the whole RDF is fed into the system.
In order to improve efficiency and to obtain higher quality gas, the RDF level in the gasifier (1) needs to be supervised by the operator and this can be done thru ultrasonic voiced level indicator (12). In order to control the RDF, there is an optional high heat and vacuum resistant window (12.1).
The sliding cover (12.2) used for protecting the inspection window is formed in a single sliding cover system and prevents the pollution of the inspection window by tar gases and explosions of gas in the gasifier (1). The sliding cover (12.2) is opened when there is high vacuum in gasifier (1) and thus it helps to extract the tar gases in the drying zone (3). The inspection window (12.1) is located at the same place with the level indicator.
The security valve (11) is used to prevent damage in the system for when there is a sudden pressure increase in the system and when there is gas accumulation at the drying zone at the pyrolysis (4) and drying zones of the gasifier (1) and when the gas can not find a path to outflow from the system. The thermocouple (13.2) located in the drying zone is used to transmit the heat information in this zone to the supervision room.
The pressure meter (14, 14.1, 14.2) in the drying zone is used to check the vacuum power applied by the fan (24). The pressure meter (14.1) used during downdraft mode indicates the pressure of the syngas outlet. The other pressure meter (14.2) is used for the same purpose in the updraft mode.
The hydraulic piston (21) located in the drying zone is lowered occasionally in order to break down the hard plastic formation within the gasifier (1). Failing to do so will cause the interruption of the system as it prevents the formation of vacuum.
The RDF after the drying zone moves into the pyrolysis zone (4) as it is seen in
The thermocouple (13.1) is used to transmit the heat information in the pyrolysis zone (4) to the supervision room. The hazardous waste spraying nozzles (20) are used to feed the hazardous waste into the gasifier (1). Sprayed liquid hazardous waste is completely mixed with the reactions and increase the syngas efficiency within the pyrolysis zone (4). The proportional valve (20.1) is used to feed the liquid hazardous waste into the gasifier in defined quantities.
The next zone within the gasifier where the gas is processed is the oxidation zone (5). Air nozzles (4.2), lower air nozzles (4.3) for the downdraft working mode are located in the gasifier (1), and first air nozzles (4.3, 4.2) for downdraft mode and second air nozzles (4.5, 4.6) for updraft mode are activated. For the updraft mode, the upper air nozzles (4.5) are located in an angular manner to lower air nozzles (16). The distance between the two air nozzles are defined according to the RDF properties and the ash quantity. The gap between the two air nozzles (4.2 and 4.3) forms the first oxidation zone (5). In this zone the heat and the carbon monoxide formation is high. The air nozzles (4.2 and 4.3) are made of high heat resistant high alloy stainless steel located separately from each other and parallel to the gasifier bed (1) so that they do not get clogged. Not all air nozzles can be activated at the same time.
For downdraft mode, the air chamber (4.7) is active whereas for updraft mode, the air chamber (4.8) is active.
Air entering from either (4.1) or from left or right air valves (6.2) can circulate through all of the nozzles (4.2, 4.3).
The air nozzle (4.4) located at the upper side of the pyrolysis zone(4) for the downdraft mode is designed and located there to fix the level at the oxidation zone (5) and the pyrolysis zone (4).
This increases the speed of full combustion reactions by giving air or oxygen in a controlled manner to the complete surface of the oxidation zone (5). This optimizes partial combustion reactions in the pyrolysis zone (4). It is important to keep the RDF level not lower than the air nozzle (4.4). Unlike other air nozzles, via proportional valve (19), air or oxygen is introduced in a controlled manner thru the air nozzle (4.4).
The Bouduard reactions are realized in the reduction zone (6) of the gasifier during the downdraft working mode. Active carbon content high materials such as ash and tar are found. The reduction reactions are completed in this zone (6) for the syngas sucked from pyrolysis zone (4), tar gas and the carbon dioxide. The syngas, the gas mixture formed in pyrolysis zone (4) are directed to the reduction zone (6) and reducted when it is passing thru the tar and ash mixture.
The ash needs to be discharged during the catalytic cracking reactions when the tar quantity is lowered and the ash content is high. Ash discharge timing is directly related to the retention time of the RDF in the reduction zone (6). There is the thermocouple (13.3) to transmit the heat information from this zone to the supervision room.
The gasifier is positioned on a 50-70° angle to the ground so that oxidized RDF in tar and ash form can easily flow downward to the reduction zone.
When the gasifier is running at updraft mode, the parts active at the reaction zone (6) are upper air nozzles (4.5), lower air nozzles (4.6), air chamber (4.8), lower preheated air or oxygen inlet (6.2), proportional valve (6.4) for air or oxygen inlet, ash grate (7.1) at the gas outlet zone for creating centrifugal effect, vapour nozzles (7.2) for increasing the carbon monoxide and hydrogen quantity to enrich syngas, igniter (8.1), igniting system (10.1) for the arc formation, thermocouple (13.3), vapour proportional valve (15) to regulate vapour rate, refractory material inside the zone (7.4) to prevent heat dissolvement.
The air flow into the air chamber (4.8) is regulated via the proportional valve (6.4) for air or oxygen inlet into the gasifier (1) during the updraft working mode and the valve (17) is opened to create vacuum.
As the ash content in the reduction zone (6) increases, clogging may occur.
Vacuum disappears and sucking of gas is prevented, ash is discharged.
The ash formed in the reduction zone (6) follows the ash path (7.3) and is discharged to ash system (22) thru the ash carrier. The first threaded carrier (22.1) carries the big particulate ash from the water trap into the dry ash pool (22.4). The second threaded carrier is used to carry accumulated and suspended ash to the dry ash pool (22.4). The ash pallet (22.3) carries the bottom accumulating ash to the second threaded carrier (22.2). In order to decrease the ash content in the ash pool (22), dry ash pool that contains dehydrated ash.
The ash discharge system is trapped into the pool with water in order to prevent the air leakage into the reduction zone (6) since there is vacuum effect in the gasifier (1). The inner holes of the ash grate (7.1) located in the ash part of the reduction zone are made out of high alloy stainless steel and the syngas formed in and moving from the pyrolysis zone (4) passes thru it. This grate (7.1) has catalytic effect on reduction process to provide more effective and simpler reactions. The active carbon rich tar kept by the grate (7.1) provides smooth flow of the syngas and carbon dioxide mixture. During this flow the catalysis effect of the grate takes place and both the carbon dioxide and methanization reactions are completed. The particles carried by the syngas formed in and carried from the pyrolysis zone (4) are dissolved on the grate (7.1) due to the catalytic effect and the syngas is conveyed to have the catalytic cracking by passing through these grates (7.1) by a centrifugal effect.
Water gas reactions are realized via water vapour coming to the reduction zone (6) from three different sources. The first one of these is thru the inlet of vapor nozzles (7.2) which introduces vapor to the system under control.
The second one of these vapor sources from the dehydrated RDF is introduced in RDF form to the system and lets the water to evaporate in the drying zone (3) and sucked into the reduction zone (6) by the vacuum effect and creates water gas effects and this is considered as the vapour resource. The third one is through the controlled suction of vapor from the ash pool at the ash discharge system thru the vacuum by causing the water vapour phase balance impaired. Thus, the content of hydrogen resulting from water gas reactions and carbon monoxide resulting from water gas coverage reactions increase. The vapour resulting from these three sources especially the one resulting from the vapour nozzles (7.2) complete the hydro cracking reactions since it is sucked by the char in the carbonated ash after the pyrolytic process. As a result of these hydro cracking reactions, the efficiency of pyrolytic reaction is increased. The hydrogen and carbon monoxide increases by promoting the gas combination.
In order to stabilize reduction and water gas reactions in the lower reduction zone (6), the vapor from vapor nozzles (7.2) are regulated.
The vapor nozzles (7.2) are only used during downdraft working mode by opening the valves (18) fully. In order to realize the water gas reactions, water vapor is introduced in a controlled manner via proportional valve (15).
The gasifier is placed on a flexible wire (10.1) as a support in order to prevent loose joints and deformations on the gasifier (1) when it is working at high heat and vibration is applied. Thus, when the vibration is applied, the complete reactor shakes and joints do not loosen.
The updraft and downdraft modes conducted in the present gasifier are as described below. The parts which are common to both modes are as follows:
RDF is weighed and passed thru the bottleneck (2). The RDF meets for the first time the heat in oxygen free environment in the bottleneck zone (2). The heat is appropriate for dehydrating the RDF that increases hydrogen with gasification. The vacuum inside the gasifier provides safe working conditions and the suction power of the fan (24) is just sufficient to provide gasification process continuity.
RDF after the bottleneck zone meets the oxygen free environment created by vacuum in the drying zone (3). The oxygen and water free RDF gets ready for the pyrolysis zone (4) in this zone by using the oxygen content and by evaporating the water content.
Syngas pre-cooling and scrubbing unit (23) is also the same for both modes. Here, the outlet syngas from the gasifier is precooled and cleaned. Especially, use of the vapor exchanger creates the difference from conventional systems. The organic gases containing energy (CO—CH4—C2H4—C3H8) face sudden temperature decrease in scrubber and they are let in water with tar, so the energy in the gas is highly lost. Without the vapor exchanger integration, it is not possible to protect the syngas and to obtain an efficient gas after the scrubber. In order to protect the energy of the gas, the heat is decreased in vapor exchanger without destroying the energy content in the organic gas. The particles are taken away without destroying the energy content in the organic gases. The gas combination proceeds after scrubber once its tar and solid particles are removed.
In this mode, since the vacuum will be upwards, the RDF needs to be fed by considering the operation safety. The vacuum range before and after feeding the RDF is the same. At updraft mode, the fan (24) operates on a less rate (2100 rpm) that is because the gas is not sucked from the ash but thru the dry RDF in the pyrolysis zone (4).
Via the level indicator (12), the level of RDF is checked. When the sliding valve (12.2) under the inspection window is opened, the projector and the inspection camera are automatically run. The information is continuously transmitted to the supervision room.
The evaporated water in the drying zone (3) is sucked into the reduction zone by the vacuum and used for water gas reactions. The oxygen in the RDF is sucked by the vacuum to be used in the pyrolysis zone (4).
During updraft mode, since the gas will be passing thru the drying zone (3), the oxygen and the water content in RDF are depleted quite fast. In this working mode, the water gas reactions are realized more effectively compared to the downdraft mode and thus recovered hydrogen gas is increased.
The particles and tar formed in the pyrolysis zone are not filtrated and not reducted and that is how they are sucked because in updraft form, the syngas is not passing thru the ash and the feeding is realized in shorter period. Therefore less clean syngas is sucked from the system compared to the downdraft mode. The syngas zone (3.1) is activated during the updraft form. The valve (17) is opened for the updraft mode. The proportional valve (6.4) is opened and proportioned according to the fed material in order to create vacuum in the gasifier.
The gas continues upwards to the outlet (3.2) under vacuum. However, since the tar gas formed in the pyrolysis zone (4) is also sucked and the syngas moves without being reducted. For the updraft mode, the zone which is 10 cm away from the oxidation zone lower air nozzles (4.5, 4.6) is the pyrolysis zone.
In order to switch from the downdraft working mode, the valves (18 and 6.3) are fully closed. For starting up the updraft mode, igniters (8.1) are ignited and they are turned off after the ignition. For the updraft mode the igniters (8.1) are located at each air chamber (4.7 and 4.8). For this mode, igniters are located symmetrically to each other in air chamber (4.8). It is important to ignite them mutually at the oxidation zone during the start up.
During the updraft mode the upper syngas zone is active (3.2). The valve (17) is completely open in this zone. The proportional valve (6.4) is opened by the operator to create vacuum in the system. First oxidation zone is located in front of lower air nozzles (4.5, 4.6). The hot syngas passes thru the air in oxidation zone (6.2) and that is how the air is heated and the syngas is cooled. The syngas is low quality in this mode since it contains more tar and this tar gas is not reducted.
The syngas desired to be recovered under vacuum condition defines the amount of the RDF to be fed and expected ash amount will vary according to the elements in RDF.
When carbon content high material is fed to the pyrolysis zone, the process slows down and ash/tar content increase. Therefore; material feeding should slow down and ash discharge should speed up. Whereas for the hydrogen rich materials, the tar and ash formation is low and the RDF feeding should slowly increase and ash discharge should slowly decrease.
In updraft mode, in the reduction zone (6), the air chamber (4.8) is used. The valve (17) is fully opened. The proportional valve (6.4) is proportionally opened for creating vacuum. It is the first chamber where the air is introduced into the gasifier (1). The air inlet is regulated through the proportional valve (6.4). The air flows into the air chamber (4.8) under vacuum and from there it proceeds to the oxidation zone (5) to continue with the oxidation reactions.
The stainless steel slope is designed for preventing the excess heat up in the air chamber by meeting the cold air. When the hot syngas passes thru either oxygen or air inlet zone (6.2), the air coming in warms up and the syngas cools down. Only during the downdraft mode, vapor is introduced to the reduction zone (6) thru the vapor nozzles (7.2) via proportional valves (15). These valves (15) are fully closed during the updraft mode and no vapor is introduced. There is no interruption during the switching between the downdraft and updraft modes.
During the switching between the modes, fan (24) is closed and the valves are selectively opened according to the desired mode. Other valves are closed. The fan (24) is then operated again and let the reactions continue without any interruptions.
When downdraft mode is active under vacuum, the RDF flows downwardly through the bottleneck zone (2). Long chain hydrocarbons are cracked in drying zone (3) and transferred into monoxide form with the partial combustion at the pyrolysis zone (4) and the combustible carbon monoxide gas is sucked by the vacuum. In the updraft mode, this tar-gas formed at the pyrolysis zone is not reducted in ash form and is not filtrated thus, all the tar gas mixes up with syngas and lowers the quality. Therefore, in downdraft mode, the gas recovered is cleaner.
When the hot syngas is introduced from the preheated air or oxygen inlet, the air coming in is heated up and the syngas is cooled down. During the downdraft mode when the oxidation zone (5) is active, the valve (18) is fully open and activated. During this mode, the lower syngas outlet zone (6.1) is activated. The proportional valve (6.3) is open to create vacuum within the gasifier. Oxidation zone is where oxygenated combustion reactions are realized. There is high amount of carbon monoxide formation. Oxidized RDF starts up pyrolysis process. When the cycle starts, the RDF processed at the oxidation zone gets lighter, flows downward and new RDF is fed once the ash discharged.
During the downdraft mode, the air within the gasifier (1) flows to the air chamber (4.7) under vacuum and from there it enters into the oxidation zone (5) and continues oxidation reactions. The lower air nozzles (4.6) are only used for updraft form.
The air chamber (4.7) is the part where air meets and the valve is open (19) in the downdraft mode. In the oxidation zone (5), air or oxygen is fed into the nozzles (4.4) in a controlled manner for the process to be properly continued. The proportional valve is opened (6.3) for vacuum creation. The required amount of air is introduced by valve (6.3). The air comes into the air chamber (4.7) under vacuum and goes down to the oxidation zone (5) to continue reactions. The heat balance is created by cooling down the stainless steel slope by the cold air entering into the air chamber. The hot syngas passes thru the oxygen inlet (4.1) so the inlet air is heated up and outlet syngas is cooled down. These valves are closed in updraft working mode (6.3).
While working in downdraft mode, the water vapor is not introduced at the first stage. Once the gasifier reaches its ideal temperature, in order to improve the quality of the outlet syngas, the syngas analysis is made and vapor is introduced into the system in a controlled manner. The vapor is at 150-170° C. when introduced into the reduction zone (6) only thru symmetrical nozzles (7.2) via proportional valve (15). During the updraft form, these valves (15) are fully closed and there is no vapor introduction.
At the updraft mode, the RDF is easily fed into the bottleneck zone (2) thru the vacuum formed by the fan (24). The ideal form of the RDF is quickly obtained by sucking the oxygen and water in RDF under heat and vacuum conditions at the drying zone (3).
The vacuum facilitates the oxidation reactions to be completed successfully and the flow of the RDF within the gasifier (1).
The syngas compound sucked from pyrolysis zone (4) and the flow of tar passes through the gas reduction zone (6) and grate (7.10) under centrifugal effect created via vacuum. Centrifugal reduction of the gas recovers cleaner gas.
During the ash discharge from the gasifier (1), the fan (24) intervenes into the water phase balance in the ash pool. The vapor generated due to the water phase destruction, flows into the ash discharge line (7.3) and reaches to the reduction zone (6) and there promotes water gas reactions.
During the downdraft working mode, the valve (18) is fully open and the proportional valve (6.3) is proportionally open to create vacuum. In order to switch from updraft mode, the valves (17 and 6.4) are fully closed.
In order to start the downdraft mode, the igniters (8) are activated and they are turned off after ignition. For this mode, the igniters (8) are located in each air chamber (4.7 and 4.8). Once the process starts, they are deactivated. The igniters are positioned symmetrically in the air chamber (4.7). The igniters are fed thru the LPG system. The end point of igniters are located in between the air nozzles (4.2 and 4.3). It is important to ignite the igniters mutually on the oxidation zone simultaneously. There is no continuous LPG feeding.
Although the invention is explained in respect to the above embodiments and methods, various modifications are evident for the persons skilled in the art without departing from the essence of the invention as defined in the attached claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2007/07958 | Nov 2007 | TR | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/IB08/50007 | 1/3/2008 | WO | 00 | 9/2/2010 |
