US20110041404A1

US20110041404A1 - Plasma-based apparatus for gasifying bio-waste into synthetic gas

Info

Publication number: US20110041404A1
Application number: US12/076,243
Authority: US
Inventors: Yuh-Jenq Yu; Chin-Ching Tzeng
Original assignee: Institute of Nuclear Energy Research
Current assignee: Institute of Nuclear Energy Research
Priority date: 2008-03-14
Filing date: 2008-03-14
Publication date: 2011-02-24

Abstract

An apparatus for producing synthetic gas from bio-waste includes a chamber, a feeder, a plasma torch, a steam-providing and water-circulating system and a synthetic gas cleaner. The feeder is in communication with the chamber. The feeder feeds the bio-waste into the chamber. The plasma torch is in communication with the chamber. The plasma torch provides plasma into the chamber for gasifying the bio-waste into the synthetic gas. The steam-providing and water-circulating system circulates water for cooling the chamber and the plasma torch. Furthermore, the steam-providing and water-circulating system and provides steam into the plasma torch for the generation of the plasma. The synthetic gas cleaner is in communication with the chamber. The synthetic gas cleaner receives the produced synthetic gas and polishes it into fuel-class gas.

Description

FIELD OF THE INVENTION

The present invention relates to the production of synthetic gas from bio-waste and, more particularly, to a plasma-based apparatus for gasifying bio-waste into synthetic gas.

DESCRIPTION OF THE RELATED ARTS

Fossil fuel is running out. The price for energy is rising. The global warming is getting worse. People around the world are exploring non-fossil energy such as solar energy, wind power, geothermal energy, fuel cells and bio-energy, intending to reduce the burden that we put on the environment and generating sustainable energy.
The bio-energy plays an important part. We can burn wood to generate heat to cook. It is however inconvenient for urban residents to burn wood. Most of the urban residents use gas instead of wood. Wooden waste causes a serious problem for the environment. Moreover, wood drifting near seashores or in ports might cause danger for traffic in the sea.
There are other types of bio-waste in addition to wooden waste. In fact, bio-waste is produced in thousands of tons in Taiwan alone. The bio-waste includes agricultural waste, forest waste, industrial waste and urban garbage. If converting bio-waste into clean fuel, we will solve a problem in handling the waste and provide a sustainable energy source.
Gasification apparatuses are used to produce synthetic gas from bio-waste. They however produce much sticky tar that sticks to devices and/or pipes used therein. The tar interferes with the operation of the gasification apparatuses. Furthermore, the synthetic gas contains tar so that the use and storage thereof are difficult. To solve the problems, water-scrubbing tar-removing apparatuses are used with the gasification apparatuses. The water-scrubbing tar-removing apparatuses use water to wash the tar from the gasification apparatuses, thus preventing the tar from clogging the pipes and reducing the combustion efficiencies. However, the cost of the equipment and the complexity of the operation and maintenance are increased. Moreover, the use of the water causes a demand on the water resource, which is also precious. Furthermore, after removing the tar from the gasification apparatuses, the water-scrubbing tar-removing apparatuses produce much wastewater, which contains the tar. The wastewater causes another problem for the environment.
The present invention is therefore intended to obviate or at least alleviate the problems encountered in prior art.

SUMMARY OF THE INVENTION

The primary objective of the present invention is to provide an apparatus for producing fuel-class synthetic gas from bio-waste.
To achieve the foregoing objective of the present invention, the apparatus for producing synthetic gas from bio-waste includes a chamber, a feeder, a plasma torch, a steam-providing and water-circulating system and a synthetic gas cleaner. The feeder is in communication with the chamber. The feeder feeds the bio-waste into the chamber. The plasma torch is in communication with the chamber. The plasma torch provides plasma into the chamber for gasifying the bio-waste into the fuel-class synthetic gas. The steam-providing and water-circulating system circulates water for cooling the chamber and the plasma torch. Furthermore, the steam-providing and water-circulating system provides steam into the plasma torch for the generation of the plasma. The synthetic gas cleaner is in communication with the chamber. The synthetic gas cleaner receives the produced synthetic gas and polishes it into fuel-class gas.
Other objectives, advantages and features of the present invention will become apparent from the following description referring to the attached drawing.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be described via the detailed illustration of the preferred embodiment referring to the attached drawing.

FIG. 1 is a cross-sectional view of a plasma-based apparatus for gasifying bio-waste into synthetic gas according to the preferred embodiment of the present invention.

FIG. 2 is a cross-sectional view of a plasma torch used in the apparatus shown in FIG. 1.

FIG. 3 is a perspective view of a bio-waste feeder used in the apparatus shown in FIG. 1.

FIG. 4 is a block diagram of a system including the apparatus shown in FIG. 1.

DETAILED DESCRIPTION OF EMBODIMENT

Referring to FIG. 1, a plasma-based apparatus 1 is used to gasify bio-waste into synthetic gas according to the preferred embodiment of the present invention. The apparatus 1 includes a chamber 11, a plasma torch for providing plasma into the chamber 11, a feeder 13 for feeding the bio-waste into the chamber 11 and a steam-providing and water-circulating system (FIG. 4). The highly active atoms and free radicals of the plasma heat and gasify the bio-waste into the synthetic gas of high energy density. The feeder 13 feeds the bio-waste into the chamber 11 in a gas-tight manner.
The chamber 11 includes an upper portion joined to a lower portion. Each of the upper and lower portions of the chamber 11 is formed with a flange 119. Threaded bolts and nuts may be used to secure the flange 119 of the upper portion of the chamber 11 to the flange 119 of the lower portion of the chamber 11.
A heat-isolating lining 111 is disposed in the chamber 11. The heat-isolating lining 111 is made of a refractory material that stands a high temperature of 1800 degrees Celsius. A water jacket 112 is located between the heat-isolating lining 111 and the chamber 11. The chamber 11 includes a water inlet 113 via which water flows into the water jacket 112 and a water outlet 114 via which the water flows out of the water jacket 112. The water flows past and cools the apparatus 1. A thermometer 115 is inserted through the chamber 11, the water jacket 112 and the heat-isolating lining 111 to measure the temperature inside the heat-isolating lining 111.
A gas inlet pipe 116 and a gas outlet pipe 118 are inserted through the chamber 11, the water jacket 112 and the heat-isolating lining 111. A mixture of reactive gasses is sent into the heat-isolating lining 111 through the gas inlet pipe 116. The types of the reactive gasses and their ratio are dependent on conditions under which the gasification is conducted. The synthetic gas is sent out of the chamber 11 through the gas outlet pipe 118. A crucible 117 is disposed in the heat-isolating lining 111 to receive ash produced after the gasification of the bio-waste. The threaded bolts and nuts can be removed from the flanges 119 so that the upper and lower portions of the chamber 11 can be detached from each other. Thus, the crucible 11 can be taken out of the chamber 11, and the ash disposed of.
Referring to FIG. 2, the plasma torch 12 includes a rear electrode 124 in communication with a front electrode 126, thus forming a barrel 123. A power supply 3 is provided between the electrodes 124 and 126. An isolator 125 is provided around the electrodes 124 and 126. A swirl generator 122 is provided around the isolator 125. The swirl generator 122 includes a steam inlet element 121 and four tangential steam outlets. A plasma outlet element 127 is provided near the front electrode 126.
Referring to FIG. 3, the feeder 13 conducts a two-phased feeding process. To this end, the feeder 13 includes a tube 136 in communication with the chamber 11, a case 133 in communication with the tube 136, a chute 131 for sending the bio-waste into the case 133, a gate 132 for controlling the communication between the case 133 and the chute 131, a vertical pusher 134 for pushing the bio-waste into the tube 136 from the case 133 and a horizontal pusher 135 for pushing the bio-waste down the tube 136 into the chamber 11.
Referring to FIG. 4, the steam-providing and water-circulating system includes a central control unit 21, a water reservoir 22, a steam reservoir 23, a steam re-heater 24 and a steam flow controller 25.
The central control unit 21 controls the operation of the steam-providing and water-circulating system.
Under the control of the central control unit 21, the water reservoir 22 detects the level of water contained therein and takes in more water if necessary to keep the level in a predetermined range. The water reservoir 22 is in communication with the steam reservoir 23 through a pipe so that the former can provide water into the latter that can turn the water into steam. The water reservoir 22 is in communication with the steam plasma torch 12 through a pipe so that the former can send water into the latter. The water reservoir 22 is in communication with the chamber 11 through a pipe so that the water reservoir 22 can provide water into the water jacket 112 of the chamber 11.
Under the control of the central control unit 21, the steam reservoir 23 detects the level of water contained therein and takes in more water if necessary to keep the level in a predetermined range. That is, the space for containing steam is retained in a predetermined range. The steam reservoir 23 is in communication with the steam re-heater 24 via a pipe so that the former sends steam into the latter.
Under the control of the central control unit 21, the steam re-heater 24 heats the steam from the steam reservoir 23 again so that the steam reaches a pre-determined temperature and is super-heated.
The steam flow controller 25 is provided between the steam re-heater and the steam plasma torch 12. The steam re-heater 24 sends the steam into the steam plasma torch 12 at a predetermined flow rate under the control of the steam flow controller 25.
Referring to FIG. 2, the steam enters the swirl generator 122 through the steam inlet 121. The swirl generator 122 turns the steam into swirl and sends the swirl into the barrel 123, thus inducing an electric arc 4. The power supply 3 provides electricity to the electrodes 124 and 126. The gap between the electrodes 124 and 126 is retained in a predetermined range by the isolator 125. The swirl forms a density gradient in the electrodes 124 and 126, thus generating a flow pattern that is less dense at the center than in the periphery. This flow pattern helps the arc 4 discharge along the electrodes 124 and 126. Moreover, this flow patterns helps to carry heat from the electrodes 124 and 126 so that the electrodes 124 and 126 can be cooled and that the arc 4 can be stabilized. Also in the barrel 123 is a pressure gradient that causes the arc 4 to extend along the electrodes 124 and 126 at two opposite ends of the swirl generator 122 and increases the power of the steam plasma torch. Finally, the arc 4 sends the plasma into the chamber 11 through the outlet element 127. The temperature at the center of the plasma torch 12 is as high as 10,000 degrees Celsius.
Referring to FIG. 3, the bio-waste is provided on the cute 131. When the temperature in the chamber 11 reaches a predetermined value, the central control unit 21 activates the feeder 13. The feeding rate is set based on the conditions under which the gasification is conducted. The gate 132 is opened so that the bio-waste slides past it along the chute 131. The gate 132 is closed again after a predetermined amount of the bio-waste slides past it. The predetermined amount of the bio-waste falls into the case 133. The vertical pusher 134 is drawn from the tube 136. The horizontal pusher 135 pushes the predetermined amount of the bio-waste into the tube 136 from the case 133. Finally, the vertical pusher 134 pushes the predetermined amount of the bio-waste down the tube 136 into the chamber 11. This process is repeated to feed the bio-waste into the chamber 11.
The plasma torch 12 raises the temperature in the chamber 11 to 800 to 1600 degrees Celsius. The feeder feeds the bio-waste into the chamber 11. The bio-waste is gasified in the chamber 11 so that the organic substances thereof are decomposed into methane, ethane, carbon monoxide and hydrogen. The mixture of the methane, ethane, carbon monoxide and hydrogen with one another is the synthetic gas.
Referring to FIG. 4, there is a synthetic gas cleaner 29 in communication with the chamber 11 so that the synthetic gas can travel into the synthetic gas cleaner 29 from the chamber 11 through the gas outlet 118. The synthetic gas cleaner 29 cleans the synthetic gas and then sends the synthetic gas into a synthetic gas storage element.
Tar and char are temporarily produced during the gasification. The tar and char react with the highly active atoms and free radicals of the plasma such as hydrogen atoms, oxygen atoms and hydroxyls.
Moreover, ash is temporarily produced during the gasification. However, the plasma torch 12 provides the plasma at 10,000 degrees Celsius to raise the temperature in the chamber to 1600 degrees Celsius to cause the ash to fuse into lava.
As discussed above, the apparatus exhibits several advantages. Firstly, it turns the organic substances of the bio-waste into the synthetic gas of the high energy density. Secondly, it eliminates tar and char without having to use an additional tar-removing device. Thirdly, it turns the inorganic substances of the bio-waste into quality lava for reuse.
The present invention has been described via the detailed illustration of the preferred embodiment. Those skilled in the art can derive variations from the preferred embodiment without departing from the scope of the present invention. Therefore, the preferred embodiment shall not limit the scope of the present invention defined in the claims.

Claims

1. An apparatus for producing synthetic gas from bio-waste comprising:

a chamber;

a feeder in communication with the chamber so that the feeder provides the bio-waste into the chamber;

a plasma torch in communication with the chamber so that the plasma torch provides plasma into the chamber for gasifying the bio-waste into the synthetic gas;

a steam-providing and water-circulating system for circulating water to cool the chamber and the plasma torch and for providing steam into the plasma torch for the generation of the steam plasma; and

a synthetic gas cleaner in communication with the chamber so that the synthetic gas cleaner receives the synthetic gas from the chamber and cleans the same.

2. The apparatus according to claim 1, wherein the chamber comprises a water inlet defined therein, a water outlet defined therein, a gas inlet defined therein and a gas outlet defined therein.

3. The apparatus according to claim 2 comprising:

a heat-isolating lining disposed in the chamber; and

a water jacket provided between the heat-isolating lining and the chamber so that water can travel into the water jacket through the water inlet of the chamber and leave the water jacket through the water outlet of the chamber.

4. The apparatus according to claim 1 comprising a crucible disposed in the chamber for receiving ash.

5. The apparatus according to claim 1, wherein the plasma raises the temperature in the chamber to 800 to 1600 degrees Celsius.

6. The apparatus according to claim 1, wherein the steam-providing and water-circulating system comprises:

a steam reservoir in communication with the plasma torch; and

a water reservoir in communication with the plasma torch and the chamber.

7. The apparatus according to claim 1, wherein the plasma torch comprises:

a rear electrode;

a front electrode in communication with the rear electrode;

an isolator provided around the rear and front electrodes;

a swirl generator provided around the isolator and formed with a steam inlet element and a steam outlet; and

a plasma outlet element is provided near the front electrode.

8. The apparatus according to claim 7, wherein the plasma torch comprises a power supply between the rear and front electrodes.

9. The apparatus according to claim 1, wherein the temperature at the center of the plasma torch is as high as 10,000 degrees Celsius.

10. The apparatus according to claim 1, wherein the feeder executes a two-phased feeding process.

11. The apparatus according to claim 1, wherein the feeder comprises:

a tube in communication with the chamber;

a case in communication with the tube;

a chute for sending the bio-waste into the case;

a gate provided between the case and the chute;

a horizontal pusher for pushing the bio-waste into the tube from the case; and

a vertical pusher for pushing the bio-waste down the tube into the chamber.

12. The apparatus according to claim 1, wherein the steam-providing and water-circulating system comprises:

a central control unit for controlling the operation of the steam-providing and water-circulating system;

a water reservoir for detecting the level of water contained therein and taking in more water if necessary to keep the level in a predetermined range, wherein the water reservoir is in communication with the steam reservoir so that the former can provide water into the latter that can turn the water into steam, the water reservoir is in communication with the steam plasma torch so that the former can send water into the latter, and the water reservoir is in communication with the chamber so that the water reservoir can provide water into the water jacket of the chamber;

a steam reservoir for detecting the level of water contained therein and taking in more water if necessary to keep the level in a predetermined range, i.e., keeping the space for containing steam in a predetermined range, and the steam reservoir is in communication with the steam re-heater so that the former sends steam into the latter;

a steam re-heater for heating the steam from the steam reservoir again so that the steam reaches a predetermined temperature and is super-heated; and

a steam flow controller provided between the steam re-heater and the steam plasma torch so that the steam re-heater sends the steam into the steam plasma torch at a predetermined flow rate under the control of the steam flow controller.