Abstract:
A carrier gas recycling system is designed according to the procedures in which a carrier gas passes through a reactor, such as a fluidized bed reactor, so as to purify and recycle gas generated in the reaction to substitute for the carrier gas externally applied to the reactor. The carrier gas recycling system includes an oil-water separation chamber to separate and purify carrier gas, and a liquid-sealed constant pressure tank to reduce carrier gas pressure fluctuation and expel extra reaction-generated gas. The carrier gas recycling system also controls the carrier gas flow by controlling the rotating speed of a blower for transferring the carrier gas, and utilizes a heat supply device used in the reaction process to preheat the carrier gas.

Description:
FIELD OF THE INVENTION 
   The present invention relates to a recycling system, and more particularly to a recycling system designed according to the procedures in which a carrier gas passes through a reactor, such as a fluidized bed reactor, so as to recycle gas generated in the reaction. 
   BACKGROUND OF THE INVENTION 
   While the highly advanced technologies bring a lot of conveniences to human, they also cause many serious damages to people&#39;s living environment. Therefore, it has become a focus among all countries in the world to develop a reasonable way of waste disposal. To comply with the increasingly strict demands for environment protection, different waste decomposition processes are developed. Among others, the so-called fluidized bed reactor has drawn the world&#39;s attention. 
   Please refer to  FIG. 1  that is a block diagram of a conventional fluidized bed reactor. As shown, the fluidized bed reactor includes a reactor  10 , into which charges  11  are fed. To enhance the mass-energy transfer function of the reactor  10 , a carrier gas  12  is applied in the operation of the reactor  10 . The carrier gas  12  serves to assist in heat supply, mass transfer, etc., and is sometimes used as part of the reactant in the reaction. The product from the reaction in the reactor  10  is then sent to and condensed and deposited in a condensation tank  20  to generate an oil-water mixture  21  and a mixed gas  22  containing the carrier gas  12 . 
   The conventional fluidized bed reactor shown in  FIG. 1  has the following drawbacks in the implementing process thereof:
         The carrier gas is typically nitrogen to maintain the reaction system in an anaerobic state. Since the nitrogen would adversely increase the operation cost, it is uneconomical to expand the reaction system; and   The carrier gas must be applied from outside of the system, which would dilute the gas generated from the reaction and lessen the purity and utility value of the reaction-generated gas.       

   It is therefore an important issue to improve the above described conventional fluidized bed reactor. 
     FIG. 2  is a block diagram showing the implementing process of another conventional fluidized bed reactor, which is developed for use in waste pyrolytic reaction. In this type of fluidized bed reactor, combustible gas generated in the pyrolysis is recycled and used as the fluidizing gas. Therefore, it is not necessary to apply a carrier gas from outside into the reactor  10 . The mixture and gas generated in the reactor  10  are condensed and deposited in the condensation tank  20 , and the purified reaction-generated gas  23  is recycled and directly guided into the reactor  10  to substitute for the carrier gas. 
   U.S. Pat. No. 5,728,271 granted to Resource Transformations International Ltd. as well as the research on Hamburg Pyrolysis Plant conducted by Kaminsky et al. in the Hamburg University, Germany are relevant to the waste disposal using the fluidized bed reactor. However, in these two cases, there is only a simple description about the recycling of combustible gas for use as fluidizing gas without details about an operable system therefor. As a matter of fact, to recycle the reaction-generated gas in the fluidized bed, many other factors, such as the maintaining of stable pressure in the system, the expelling of ultra reaction-generated gas, the control of transferred gas, the preheating of gas, etc., must be taken into consideration at the same time. 
   SUMMARY OF THE INVENTION 
   A primary object of the present invention is to provide a carrier gas recycling system to realize the recycling of reaction-generated gas for use as a carrier gas in a reaction system. 
   Another object of the present invention is to provide a carrier gas recycling system that enables elimination of cost for applied carrier gas and upgrades the purity of gas generated in the reaction to largely increase the utility value of the reaction-generated gas. 
   To achieve the above and other objects, the carrier gas recycling system according to the present invention includes an oil-water separation chamber to separate and purify the carrier gas, and a liquid-sealed constant pressure tank to reduce carrier gas pressure fluctuation and expel extra reaction-generated gas. The system also controls the carrier gas flow by controlling the rotating speed of a blower for transferring the carrier gas, and utilizes a heat supply device used in the reaction process to preheat the carrier gas. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The structure and the technical means adopted by the present invention to achieve the above and other objects can be best understood by referring to the following detailed description of the preferred embodiments and the accompanying drawings, wherein 
       FIG. 1  is a block diagram showing the implementing process of a conventional fluidized bed reactor; 
       FIG. 2  is a block diagram showing the implementing process of another conventional fluidized bed reactor with gas recycling; 
       FIG. 3  is a block diagram of a carrier gas recycling system according to the present invention; 
       FIGS. 4A and 4B  are schematic views of a condensation tank included in the carrier gas recycling system of the present invention; and 
       FIGS. 5A and 5B  are schematic views of a constant pressure tank included in the carrier gas recycling system of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Please refer to  FIG. 3  that is a block diagram of a carrier gas recycling system according to the present invention designed for mounting in a fluidized bed reaction system, so that part of the gas generated in the reaction is recycled and guided to a reactor thereof to substitute for the carrier gas needed in the operation of the fluidized bed reaction system. 
   As shown in  FIG. 3 , the carrier gas recycling system of the present invention includes a reactor  10 , a condensation tank  20 , a filtering unit  30 , a constant pressure tank  40 , a transfer device  50 , a pre-heater  70 , and a backup carrier gas tank  80 . The reactor  10  is used to receive and combine charges with a carrier gas to generate a mixture and gas. The condensation tank  20  receives the mixture and gas produced by the reactor  10 , separates the oil and water in the mixture from each other, separates and purifies the reaction-generated gas, and delivers the reaction-generated gas to the filtering unit  30 . The filtering unit  30  may use a static precipitator to remove particulate pollutant, so as to ensure that the reaction-generated gas is free of any oil-gas deposition and accumulation before being sent into the transfer device  50 . The filtered reaction-generated gas is then output via to paths to the constant pressure tank  40  and the transfer device  50  separately. 
   After receipt of the reaction-generated gas, the constant pressure tank  40  on the one hand maintains a constant pressure in the system balancing with the external atmosphere, and on the other hand outputs the reaction-generated gas for burning (that is, waste gas burning). When the transfer device  50  receives the reaction-generated gas, it recycles and feeds the reaction-generated gas back to the reactor  10 , so that a reaction-generated gas circulation loop is formed. The reaction-generated gas is preheated by the pre-heater  70  before being sent into the reactor  10 . The preheated reaction-generated gas substitutes for the carrier gas and is cyclically supplied to the reactor  10 . The transfer device  50  is also connected to the backup carrier gas tank  80 , in which an amount of carrier gas is stored. Before the system has generated any gas, or before the system is actuated, the carrier gas in the backup carrier gas tank  80  is output to maintain system operation. 
   The transfer device  50  may be a non-explosive or a non-explosion-proof compressor, or a blower for transferring the reaction-generated gas. When the transfer device  50  is a compressor, a buffer tank  60  and a pressure regulating valve  61  must follow the compressor  50 , so that the reaction-generated gas from the transfer device  50  is buffered and stored in the buffer tank  60 , and regulated by the pressure regulating valve  61  to a predetermined output flow before being fed back for use by the reactor  10 . On the other hand, when the transfer device  50  is a blower, the blower may be directly adjusted to a predetermined rotating speed to achieve the purpose of regulating the output flow. The pre-heater  70  preheats the carrier gas in a non-direct contact manner, so that the carrier gas is recycled. When the pre-heater  70  has a preheating temperature that is too high, the temperature is regulated by increasing the gas flow. To maintain a fixed input flow to the reactor  10 , any extra gas is properly cooled and recycled back to the transfer device  50 . For this purpose, a pressure regulator  71  and a flow regulator  72  are provided following the pre-heater  70 . When the transferred carrier gas is increased, the pressure regulator  71  regulates the pressure generated by the carrier gas; and the flow regulator  72  serves to send the extra carrier gas back to the transfer device  50 . 
   The operation of the condensation tank  20  included in the carrier gas recycling system of the present invention is now described in details with reference to  FIGS. 4A and 4B , which are schematic views of the condensation tank  20 . 
   The condensation tank  20  is internally divided into a separation chamber and a storage chamber located below the separation chamber. A photo-sensor  24  and an external pump  25  cooperate with the condensation tank  20  to form a photo-sensing level controlling system. The mixture produced by the reactor  10  and sent to the condensation tank  20  reaches the separation chamber first, at where water and oil in the mixture are separated. Since oil has a specific of gravity lower than water, water in the mixture naturally sink to a lower portion of the separation chamber while oil in the mixture floats on the water surface. When the mixture is continuously sent into the separation chamber, the oil floating on the water would finally flow over the separation chamber into the storage chamber while the water is retained in the separation chamber. The condensation tank  20  is therefore an effective oil-water separating system. 
   The mixture is continuously sent to the separation chamber during the reaction. At this point, the photo-sensor  24  functions to detect the water level in the separation chamber, so as to prevent the water from flowing over the separation chamber into the storage chamber. When the water level in the separation chamber reaches a high level H preset by the photo-sensor  24 , as shown in  FIG. 4B , the photo-sensor  24  would send out a start signal to actuate the external pump  25  to pump water out of the separation chamber. To prevent the external pump  25  from pumping the oil from the separation chamber, the photo-sensor  24  would send out a stop signal to the external pump  25  when the water level in the separation chamber reaches a low level L preset by the photo-sensor  24 , as shown in  FIG. 4A , so that the external pump  25  stop pumping water. 
     FIGS. 5A and 5B  show the operation of the constant pressure tank  40  included in the carrier gas recycling system of the present invention. The constant pressure tank  40  isolates the system from external air by way of liquid seal. In the present invention, a gas escape tube is adopted in the liquid seal to protect the system against exceeded back pressure and high pressure oscillation. As shown in  FIGS. 5A and 5B , the constant pressure tank  40  is internally provided with a gas inlet chamber, a gas escape tube  41 , and a pressure buffering chamber. The gas inlet chamber and the pressure buffering chamber, which are located at the left and the right side, respectively, of the tank  40  when viewing before the drawing, are separated from each other by a partition wall. However, the constant pressure tank  40  is provided near a bottom of the partition wall with a gas port, via which seal liquid in the tank  40  freely flows between the gas inlet gas chamber and the pressure buffering chamber. The gas escape tube  41  is provided in the gas inlet chamber with a lower end inserted into the seal liquid in the gas inlet chamber. When the reaction-generated gas is sent into the constant pressure tank  40  to accumulate sufficient gas pressure in the tank  40 , the seal liquid in the gas inlet chamber is compressed toward the lower end of the gas escape tube  41 , and forced into the pressure buffering chamber via the lower gas port, so that the gas inlet chamber is maintained at the constant pressure balanced with the external atmospheric pressure. At this point, the lower end of the gas escape tube  41  inserted in the gas inlet chamber is exposed to the reaction-generated gas due to the lowered liquid level in the gas inlet chamber, and a predetermined quantity of the gas may escape out of the gas inlet chamber via the gas escape tube  41 , as shown in  FIG. 5B . 
   The carrier gas recycling system of the present invention is superior to the prior art for the following the features:
         (a) Adopting a photo-sensor to control the water level in the oil-water separation chamber of the condensation tank  20 ;   (b) Adopting seal liquid and gas escape tube in the constant pressure tank  40  to maintain a constant pressure in the system;   (c) Adopting the buffer tank  60  and the pressure regulating valve  61  to control the circulation and transfer of the reaction-generated gas;   (d) Adopting the pressure regulator  71  and the flow regulator  72  to cooperate with the pre-heater  70  in controlling the flow of preheated carrier gas;   (e) Providing the backup carrier gas tank  80 ; and   (f) Being able to purify and accordingly increase the utility value of the reaction-generated gas.       

   The present invention has been described with a preferred embodiment thereof and it is understood that many changes and modifications in the described embodiment can be carried out without departing from the scope and the spirit of the invention that is intended to be limited only by the appended claims.