Abstract:
It is an object of the present invention to provide a method for reducing crushing of grain when the grain having Vickers hardness Hv in a range of 11≦Hv≦14 is transported by means of gas. The present invention is a gas transportation method for grain having Vickers hardness Hv in a range of 11≦Hv≦14, and gas transportation is performed under the condition that a velocity V of transportation gas is set at a value in a range of 10 m/s≦V≦20 m/s. Alternatively or additionally, a blending ratio μ expressed as a ratio of a flow amount of the grain (kg/H) to a flow amount of the transportation gas (kg/H) is set at a value in a range of (3 V−30)≦μ≦(3 V−20).

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a gas transportation method for grain, and more particularly to a method for transporting grain with low hardness such as rice by means of gas. 
     2. Description of Related Art 
     Conventionally, in rice polishing factories and boiled rice factories, delivered unpolished rice is usually polished by a rice polishing machine to be half-polished rice, and the half-polished rice is processed to be polished rice with its rice bran removed. This polished rice is stored, wrapped to be shipped after being blended with various kinds of polished rice, or is used immediately for boiled rice. In various transportation processes of transporting rice from an unpolished rice storage tank to the rice polishing machine, from the rice polishing machine to a rice bran removing machine, from the rice bran removing machine to a polished rice storage tank, from the polished rice storage tank to a blended rice accommodation tank, and so on, a number of transportation apparatus such as bucket conveyers, lifts, horizontal belt conveyers, and the like are usually used. 
     However, these transportation apparatus tend to become upsized as factories become large, which has resulted in difficulty in assembly, installation, and maintenance thereof. Furthermore, since rice bran remains in gap parts in these transportation apparatus, microbes such as mold may possibly grow to gather insects and so on eating the mold. This has brought about a problem that values of rice and boiled rice as products may possibly be lost. Since the transportation apparatus need to be frequently disassembled for cleaning in order to eliminate the problem, a problem has been further caused that maintenance cost is increased. 
     To solve these problems, apparatus for pneumatically transporting rice through pipes are known as are disclosed in Japanese Patent Laid-open No. Hei 7-330151, Japanese Patent Laid-open No. Hei 2-56255, and Japanese Patent Laid-open No. Sho 52-20582. In these apparatus, grain such as rice is transported by air streams which are generated in pipes with the use of blowers and compressors. The use of such a pneumatic transportation method makes it possible to avoid the problem that the rice bran remains halfway in the pipes since the rice and the air are transported in the pipes which are shielded from the outside. 
     However, in the conventional pneumatic transportation method, problems have often occurred that transported rice is crushed or each grain of rice cracks to reduce the value of the rice as a product. Since consumers demand high quality, particularly for rice to be used for boiled rice, sufficient quality control is required. However, it has been very difficult to transport rice pneumatically without causing any crush or crack to the rice. 
     The present invention is made in view of the conventional problems as described above and it is an object of the present invention to provide a gas transportation method and apparatus which are capable of preventing transported grain such as rice from crushing or cracking. 
     SUMMARY OF THE INVENTION 
     Transportation methods by means of gas such as air are generally divided into a high-pressure transportation method in which the pressure of supplied air is set at a value equal to 200 kPa (kilopascal) or more and a low-pressure transportation method in which the pressure of the supplied air is suppressed at a low value. In the high-pressure transportation method, pressurizing air flows through transportation pipes at a high speed when transportation is finished so that substances moving though the pipes may possibly collide with inner wall surfaces of the pipes to be crushed. Hardness of grain such as rice is generally in a lower range of 11≦Hv≦14 in terms of Vickers hardness Hv and since the occurrence of crush and crack of grain during transportation affect its quality, the low-pressure transportation method in which the pressure of the supplied air is suppressed at a low value is appropriate for pneumatic transportation of grain. However, when grain is transported through pneumatic transportation pipes in which transportation passages are long and curved, pressure loss is caused. Therefore, making allowance for this pressure loss, air pressure of a supplying source is generally set at approximately 50 kPa. Transportation of grain through the pipes under this pressure causes the possibility that the grain may be damaged, and therefore, a countermeasure for this problem is required. 
     Next, findings obtained by the inventors of the present invention are explained. As a result of various studies on correlation of a collision speed of polished rice with its crushing rate and cracking rate, the inventors of the present invention have found that a velocity V of transportation gas needs to be in a range from 10 m/s to 20 m/s. FIG. 1 is a graph showing correlation between a collision speed and rates of occurrence of crushed granules of polished rice and of occurrence of cracked plus crushed granules of polished rice. Here, the crushed granules of polished rice mean polished rice which is crushed to be broken into pieces and therefore, is difficult to be used as boiled rice and can be used only for materials for confectionary, rice crackers, or the like. The cracked granules mean polished rice which only has cracks therein and can be used as boiled rice. This experiment was conducted, using a device in which a blower  82  is disposed at one end of an acryl pipe  81  having length of 1000 mm and a stainless plate  83  is disposed vertically in a position 25 mm away from an exit at the other end of the acryl pipe  81 , as shown in FIG.  2 . Damage condition of polished rice  84  was examined after the polished rice  84  was put at an end part on a blower  82  side inside the acryl pipe  81  as shown in FIG.  2  and was pneumatically transported by the blower  82  to be collided with the stainless plate  83  at a collision angle of 90 degrees. 
     It is apparent from FIG. 1 that the occurrence rate of crushed granules or cracked and crushed granules of the polished rice suddenly increases when the collision speed exceeds 20 m/s. Therefore, the velocity V of the transportation air needs to be set at a value equal to 20 m/s or less. Meanwhile, in order to secure an amount of transported rice in pneumatic transportation, the velocity V of the transportation air needs to be set at a value equal to 10 m/s or more. Based on the above findings, it has been found that the velocity V of the transportation air needs to be set at a value in a range of 10 m/s≦V≦20 m/s. 
     The inventors of the present invention have also found it appropriate that a blending ratio μ which is expressed by a ratio of a flow amount of the polished rice (Kg/H) to a flow amount of the transportation air (Kg/H) is set at a value within the following range. Namely, the inventors of the present invention have obtained the result, after studying correlation between the velocity V (m/s) of the transportation air and the blending ratio μ, that appropriately, the blending ratio is within the range between the line P-R and the line Q-S in FIG.  3 . In FIG. 3, L 1 , L 2 , L 3 , and L 4  show results in cases where the length of the transportation pipe is 15 m, 50 m, 75 m, and 100 m respectively. A favorable result has been obtained that the polished rice can be transported without any crushed granules occurring therein in this range while an unfavorable result has been obtained that the occurrence rate of the crushed granules increases outside this range. Based on these results, it has been found appropriate that the blending ratio μ is in a range of (3 V−30)≦μ≦(3 V−20). 
     The inventors of the present invention have also confirmed in the experiment that the inside of the pipe is clogged when μ exceeds 10 under the condition that the velocity V of the transportation air is approximately 10 m/s, which does not allow pneumatic transportation to be performed. It has also been confirmed in the experiment that, when μ is 10 or less, since the inside of the pipe approximates to vacancy, the pipe is not clogged, which allows the rice to be sent smoothly, but since an amount of transported rice is small, the rice easily collides, and, under the condition of a high velocity of the transportation air, it easily crushes. Meanwhile, as the velocity V approaches 20 m/s, which results in an increased amount of the transportation air, even more amount of the rice can be transported and crushing is reduced owing to self-cushion among the rice. However, there is a limit that crushing increases drastically when the velocity V exceeds 20 m/s as described above. 
     Based on the above findings, the inventors of the present invention have found it appropriate that the blending ratio μ is within the range surrounded by the substantial parallelogram P, Q, R, S shown in FIG.  3 . 
     The inventors of the present invention have also obtained correlation of a difference in temperature between polished rice and transportation air with damage to the polished rice under the condition that the velocity V of the transportation air is fixed (V=20 m/s), using the experiment device shown in FIG.  2 . In this experiment, the polished rice  84  is put and kept unmoved in the air whose temperature is 20° C. and whose humidity is 70%, and thereafter, the polished rice  84  whose temperature has reached 20° C. is put at one end on the blower  82  side of the acryl pipe  81 , while an air stream generated by the blower  82  is supplied with its temperature adjusted by a heater  85  to vary its difference in temperature from that of the polished rice  84 . Similarly to the aforesaid experiment, the damage condition of the polished rice  84  was examined after the polished rice  84  was pneumatically transported by the blower  82  to be collided with the stainless plate  83  at the collision angle of 90 degrees. 
     The result of the experiment is shown in FIG.  4 . In FIG. 4, the horizontal axis shows a difference in temperature (° C.) between the polished rice and the transportation air and the vertical axis shows an occurrence rate of crushed granules and an occurrence rate of cracked granules of the polished rice. The occurrence rate of crushed granules is shown by the solid line A and the occurrence rate of cracked granules is shown by the broken line B. 
     It is apparent from FIG. 4 that a crushing rate of the polished rice varies depending on the temperature difference between the polished rice and the transportation air. For example, the result of the experiment in FIG. 1 shows that the crushing rate of the polished rice is approximately 15% under the condition of the velocity of V=20 m/s, but the result of the experiment in FIG. 4 shows that the crushing rate of the polished rice increases to approximately 22% or more under the condition that the temperature difference between the polished rice and the transportation air is 20° C. or more. 
     The inventors of the present invention have found from the experiment result shown in FIG. 4 that crushed granules do not occur when the temperature difference between the polished rice and the transportation air is 10° C. or less. Therefore, when the polished rice is transported by transportation air flowing through transportation pipes which are connected with tanks for accommodating the polished rice therein, it is appropriate that the transportation air whose temperature difference from that of the polished rice flowing into the tanks or the polished rice flowing out of the tanks is 10° C. or less is supplied into the transportation pipes to transport the polished rice. Basically, it is appropriate that the temperature of the transportation air is equal to the temperature of the polished rice, but it has been found that in an actual apparatus, the temperature difference of the transportation air from that of the polished rice may be within a range of ±15° C. and more appropriately, within a range of ±10° C. 
     The present invention, which is made based on the above findings, is a gas transportation method for grain having Vickers hardness Hv in a range of 11≦Hv≦14, and is characterized in that a velocity V of transportation gas is adjusted to be in a range of 10 m/s≦V≦20 m/s. 
     The present invention is also a gas transportation method for grain having Vickers hardness Hv in a range of 11≦Hv≦14, and is characterized in that a blending ratio μ expressed as a ratio of a flow amount of the grain (kg/H) to a flow amount of transportation gas (kg/H) is set in a range of (3 V−30)≦μ≦(3 V−20). 
     It is also a gas transportation method for grain having Vickers hardness Hv in a range of 11≦Hv≦14, and is characterized in that a velocity V of transportation gas is set to be in a range of 10 m/s≦V≦20 m/s and a blending ratio μ expressed as a ratio of a flow amount of the grain (kg/H) to a flow amount of the transportation gas (kg/H) is set to be in a range of (3 V−30)≦μ≦(3 V−20). 
     Furthermore, it is appropriate that the temperature of the transportation gas is controlled so that a difference between the temperature of the transportation gas and the temperature of the grain is within a predetermined range. 
     It is appropriate here that the difference between the temperature of the transportation gas and the temperature of the grain is 15° C. or less. 
     It is also appropriate that the humidity of the transportation gas is controlled to be at a value substantially equal to equilibrium temperature of the grain. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a graph showing correlation of a collision speed with an occurrence rate of crushed granules and of cracked plus crushed granules of polished rice when the polished rice is collided with a wall surface at a right angle; 
     FIG. 2 is an explanatory view of a device used for the experiment in FIG. 1; 
     FIG. 3 is a graph showing correlation between a velocity of transportation air and a blending ratio in pneumatic transportation of polished rice; 
     FIG. 4 is a graph showing correlation of a difference in temperature between the polished rice and the transportation air with the occurrence rate of the crushed granules and the cracked granules of the polished rice; 
     FIG. 5 is an explanatory block diagram of a transportation apparatus for rice showing one embodiment of the present invention; according to the present invention; and 
     FIG. 6 is a fragmentary enlarged view of the transportation apparatus for rice in FIG.  5 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A preferred embodiment of a gas transportation method for grain according to the present invention is explained in detail below with reference to the drawings. 
     FIG. 5, showing one embodiment of the gas transportation method for grain according to the present invention, is an explanatory block diagram of an apparatus in a case where the present invention is applied to pneumatic transportation of rice. 
     FIG. 5, a transportation apparatus  1  for rice has a structure in which four stages of transportation pipes  11  through which pneumatic transportation is performed are connected in series. The transportation apparatus  1  is composed of an unpolished rice storage section  2  for storing unpolished rice therein, a rice polishing section  3  for polishing the unpolished rice to make half-polished rice, a rice bran removing section  4  for removing rice bran from the half-polished rice to make polished rice, a polished rice storage section  5  for storing the polished rice therein, and a blending section  6  for blending various kinds of polished rice stored in the polished rice storage section  5 . 
     The transportation pipes  11  are composed of a first transportation pipe  11   a  for connecting the unpolished rice storage section  2  with the rice polishing section  3 , a second transportation pipe  11   b  for connecting the rice polishing section  3  with the rice bran removing section  4 , a third transportation pipe  11   c  for connecting the rice bran removing section  4  with the polished rice storage section  5 , and a fourth transportation pipe  11   d  for connecting the polished rice storage section  5  with the blending section  6 . It is necessary that curvature of passages of these transportation pipes  11  is set at a value at least equal to 500 mmR or more (more appropriately, about 1000 mmR) to prevent rice from colliding with inner walls of the pipes at an acute angle. 
     The transportation pipes  11  are provided at respective starting ends thereof with blowers  13  for sending an air stream and intercoolers  15  which are disposed inside the pipes on downstream sides of the blowers  13 , for heating or cooling transportation air according to the temperature of the rice to adjust the temperature of the transportation air. By putting the blowers  13  and the intercoolers  15  into operation, the air whose temperature is adjusted at a value appropriate for the rice moving toward terminal ends of the transportation pipes  11  is sent into the transportation pipes  11 . Moreover, humidifying/dehumidifying devices  17  are provided on downstream sides of the intercoolers  15  to adjust the humidity of the transportation air to be equal to equilibrium humidity of the rice. Here, the equilibrium humidity of the rice, which means the humidity at which rice does not absorb or discharge moisture, is approximately 70%. 
     Each of the transportation pipes  11   a ,  11   b ,  11   c , and  11   d  is explained as follows. In the first transportation pipe  11   a , a first blower  13   a , a first intercooler  15   a , and a first humidifying/dehumidifying device  17   a  are disposed; in the second transportation pipe  11   b , a second blower  13   b , a second intercooler  15   b , and a second humidifying/dehumidifying device  17   b  are disposed; in a third transportation pipe  11   c , a third blower  13   c , a third intercooler  15   c , and a third humidifying/dehumidifying device  17   c  are disposed; and in a fourth transportation pipe  11   d , a fourth blower  13   d , a fourth intercooler  15   d , and a fourth humidifying/dehumidifying device  17   d  are disposed. 
     The unpolished rice storage section  2  is provided with a plurality of first storage tanks  21  for storing unpolished rice therein, and the first storage tanks  21  are connected with the first transportation pipe  11   a  at parts on a downstream side of the first blower  13   a , the first intercooler  15   a , and the humidifying/dehumidifying device  17   a  via respective rotary feeders  23 . When the transportation air is supplied to the first transportation pipe  11   a  by the first blower  13   a , the unpolished rice discharged from the first storage tanks  21  by the respective rotary feeders  23  is transported toward the rice polishing section  3  which is disposed at a terminal end of the first transportation pipe  11   a.    
     All of first storage tanks  21 A,  21 B,  21 C . . . , and so on are provided with unpolished rice temperature sensors  25  for measuring respective temperatures of stored unpolished rice A, B, C . . . , and so on, and temperature signals indicating the temperatures measured by the unpolished rice temperature sensors  25  are transmitted to control means  31 . The control means  31  stores the temperatures of the first intercooler  15   a  corresponding to the temperatures of the unpolished rice measured by the unpolished rice temperature sensors  25  and controls a difference in temperature between the unpolished rice and the transportation air to be within a predetermined range. Alternatively, feed back control is also appropriate in which a temperature sensor  29  (shown in FIG. 6) for measuring the temperature of the air is provided inside the first transportation pipe  11   a  on a downstream side of the first intercooler  15   a  and the humidifying/dehumidifying device  17   a  as shown in FIG. 6, and the control means  31  receives a temperature signal indicating the measured temperature to adjust the temperature of the first intercooler  15   a . Furthermore, a humidity sensor  27   a  for measuring the humidity of the transportation air from the first intercooler  15   a  is also provided in the first transportation pipe  11   a , and a humidity signal indicating the humidity measured by the humidity sensor  27   a  is transmitted to the control means  31 . Based on this humidity signal, the control means  31  outputs an instruction to the humidifying/dehumidifying device  17   a  so that the humidity of the transportation air is adjusted to be equal to the equilibrium humidity (approximately 70%) of the rice, for example, by generation of vapor, and the control means  31  causes the transportation air to be supplied to the first transportation pipe  11   a.    
     The rice polishing section  3  is provided with a plurality of branch valves  33  which are disposed in series in the first transportation pipe  11   a , for sending the unpolished rice which is transported thereto to either one of branching-off passages. By an appropriate changeover operation of the branch valve  33  designated by an instruction from the control means  31 , the unpolished rice which has passed through either one of the branching-off passages is sent to a corresponding rice polishing machine  37  via a corresponding first accommodation tank  35  to be processed into half-polished rice. Incidentally, the structure in which the changeover operation is performed at a branching angle of 30° or less so as not to have branching lines make sharp curves at the branch valves  33  prevents the unpolished rice from crushing due to collision. Under the rice polishing machines  37 , a plurality of second accommodation tanks  39  for storing half-polished rice and storing various kinds of half-polished rice to be supplied to a starting end side of the second transportation pipe  11   b  are disposed. 
     The plural second accommodation tanks  39  are connected with the second transportation pipe  11   b  at parts on a downstream side of the second blower  13   b  and the second intercooler  15   b  via respective rotary feeders  23 . Supplying the transportation air to the second transportation pipe  11   b  by the second blower  13   b  causes the half-polished rice which is discharged from the second accommodation tanks  39  by the respective rotary feeders  23  to be transported to the rice bran removing section  4  which is disposed at a terminal end of the second transportation pipe  11   b . In the second accommodation tanks  39 , half-polished rice temperature sensors  41  for measuring the temperatures of the stored half-polished rice is provided and temperature signals indicating the temperatures measured by the half-polished rice temperature sensors  41  are transmitted to the control means  31 . Furthermore, a humidity sensor  27   b  for measuring the humidity of the transportation air from the second intercooler  15   b  is provided in the second transportation pipe  11   b  and a humidity signal indicating the humidity measured by the humidity sensor  27   b  is transmitted to the control means  31 . The control means  31  receives the temperature signals and the humidity signal to perform control operation in the same manner as previously described. 
     The rice bran removing section  4  is provided with a plurality of branch valves  33  which are connected in series in the second transportation pipe  11   b , for sending the half-polished rice which is transported thereto to either one of branching-off passages. By the changeover operation of the branch valve  33  designated by an instruction from the control means  31 , the half-polished rice which has passed through either one of the branching-off passages is sent to a corresponding rice bran removing machine  45  to be processed into polished rice with its rice bran removed. Under the rice bran removing machines  45 , a plurality of third accommodation tanks  47  for storing the polished rice from which rice bran has been removed and storing various kinds of polished rice to be supplied to a starting end side of the third transportation pipe  11   c  are disposed. 
     The plural third accommodation tanks  47  are connected with the third transportation pipe  11   c  at parts on a downstream side of the third blower  13   c  and the third intercooler  15   c  via respective rotary feeders  23 . Supplying the transportation air to the third transportation pipe  11   c  by the third blower  13   c  causes the polished rice which is discharged from the third accommodation tanks  47  by the respective rotary feeders  23  to be transported to the polished rice storage section  5  which is disposed at a terminal end of the third transportation pipe  11   c . In the third accommodation tanks  47 , polished rice temperature sensors  49  for measuring the temperatures of the stored polished rice is provided and temperature signals indicating the temperatures measured by the polished rice temperature sensors  49  are transmitted to the control means  31 . Furthermore, a humidity sensor  27   c  for measuring the humidity of the transportation air from the third intercooler  15   c  is provided in the third transportation pipe  11   c  and a humidity signal indicating the humidity measured by the humidity sensor  27   c  is transmitted to the control means  31 . The control means  31  receives the temperature signals and the humidity signal to perform control operation in the same manner as previously described. 
     The polished rice storage section  5  is provided with a plurality of branch valves  33  which are disposed in series in the third transportation pipe  11   c , for sending the polished rice which is transported thereto to either one of branching-off passages. By the changeover operation of the branch valve  33  designated by an instruction from the control means  31 , the polished rice which has passed through either one of the branching-off passages is stored in a predetermined polished rice storage tank  51 . 
     The plural polished rice storage tanks  51  are connected with the fourth transportation pipe  11   d  at parts on a downstream side of the fourth blower  13   d  and the fourth intercooler  15   d  via respective rotary feeders  23 . Supplying the transportation air to the fourth transportation pipe  11   d  by the fourth blower  13   d  causes the polished rice which is discharged from the polished rice storage tanks  51  by the respective rotary feeders  23  to be transported toward the blending section  6  which is disposed at a terminal end of the fourth transportation pipe  11   d . In the polished rice storage tanks  51 , stored polished rice temperature sensors  53  for measuring the temperatures of the stored polished rice is provided and temperature signals indicating the temperatures measured by the stored polished rice temperature sensors  53  are transmitted to the control means  31 . Furthermore, a humidity sensor  27   d  for measuring the humidity of the transportation air from the fourth intercooler  15   d  is provided in the fourth transportation pipe  11   d  and a humidity signal indicating the humidity measured by the humidity sensor  27   d  is transmitted to the control means  31 . The control means  31  receives the temperature signals and the humidity signal to perform control operation in the same manner as described above. 
     The blending section  6  is provided with a plurality of branch valves  33  which are disposed in series in the fourth transportation pipe  11   d , for sending the stored polished rice which is transported thereto to either one of the branching-off passages. By the changeover operation of the branch valve  33  designated by an instruction from the control means  31 , the stored polished rice which has passed through the branching-off passage is accommodated in a corresponding measuring tank  57 . The measuring tanks  57  are provided with load sensors  59  attached thereto, which measure the weights of kinds of polished rice A, B, C . . . , and so on which are transported via the fourth transportation pipe  11   d  and the branch valves  33  to transmit the measured weights to the control means  31 . When set specific amounts of various kinds of the polished rice A, B, C . . . , and so on are transported to and accommodated in the measuring tanks  57 , valves  61  are opened to send the polished rice to blending machines  63 . The blending machines  63  are driven by motors  63   a  according to instructions from the control means  31  to be rotated and blend various kinds of the polished rice A, B, C, . . . , and so on to make blended rice. The blended rice is wrapped by wrapping machines  67  and shipped after being accommodated in blended rice accommodation tanks  65 . 
     Incidentally, the control means  31  is connected with not-shown driving devices for driving the first blower  13   a , the second blower  13   b , the third blower  13   c , and the fourth blower  13   d  to control the respective blowers to start driving and stop driving. Furthermore, the control means  31  is connected with not-shown operating devices for operating the rotary feeders  23  and the branch valves  33  to control their starting and stopping operations and outputs instructions to these devices that the rice such as the unpolished rice, the half-polished rice, and the polished rice should be supplied to a predetermined one of the storage tanks, accommodation tanks, rice bran removing machines  45 , measuring tanks  57 , and so on from the pipes. The order of operations of the blowers  13 , the intercoolers  15 , the rotary feeders  23 , the branch valves  33 , the rice polishing machines  37 , the rice bran removing machines  45 , the blending machines  63 , and so on is determined by inputs to the control means  31  according to a required kind of blended rice, a required amount of rice, a shipment situation, and so on. The above-mentioned rotary feeders  13  are discharge devices which have space partitioned by blades arranged at equal spaced intervals on the circumferences thereof and are driven by not shown electric motors, and they are structured to discharge predetermined amounts of rice by their rotation. The branch valves  33  are disposed in series, among which only the branch valve  33  receiving an instruction signal from the control means  31  is changed over at the time of operation to transport the rice from the transportation pipes in a branching-off manner. 
     In this embodiment, unpolished rice is pneumatically transported from the unpolished rice storage section  2  for storing unpolished rice therein to the rice polishing section  3  which is disposed on a subsequent stage, for polishing unpolished rice, and half-polished rice is pneumatically transported from the rice polishing section  3  to the rice bran removing section  4  for removing rice bran to make polished rice, and furthermore, polished rice is pneumatically transported from the rice bran removing section  4  to the polished rice storage section  5  for storing polished rice therein. This pneumatic transportation is performed by each of the blowers  13  and each of the rotary feeders  23  in each of the processing sections as described above, and they are controlled by the control means  31 . 
     The velocity V of the transportation air generated by the blowers  13  and the blending ratio μ are controlled by the control means  31  and are controlled to be at the following values as described above. Namely, the velocity V of the transportation air supplied from each of the blowers  13   a ,  13   b ,  13   c , and  13   d  is controlled to be within the following range: 
     [Numerical formula 1] 
     
       
         10 m/s≦V≦20 m/s 
       
     
     Furthermore, the blending ratio μ expressed as the ratio of the flow amount of the rice (kg/H) to the flow amount of the transportation air (kg/H) is controlled to be in the following range. 
     [Numerical formula 2] 
     
       
         (3 V−30)≦μ≦(3 V−20) 
       
     
     The blending ratio μ is defined as follows. 
     [Numerical formula 3] 
     μ=a flow amount of rice (g/H)/a flow amount of air (kg/H) 
     Showing specific values for the above by a graph as the blending ratio μ relative to the velocity V (m/s) of the transportation air, the result shown in FIG. 3 is obtained as previously described. The range surrounded by the substantial parallelogram P, Q, R, S including the lines at the lower limit value 10 m/s and the upper limit value 20 m/s of the velocity of the transportation air is a range where crushing and cracking of the rice do not occur. More specifically, when μ exceeds 10 under the condition that V (m/s) is approximately 10 m/s, the inside of the pipes is clogged, which does not allow gas transportation, and therefore, the flow amount of the rice cannot be increased. When μ is less than 10, the pipes are not clogged to allow the rice to be sent smoothly, but since the flow amount of the rice is small, the problem that collision easily occurs and the rice easily crushes is caused. Moreover, since transportation efficiency is low, this condition cannot be applied. As V approaches 20 m/s, which results in an increased amount of the air, even more amount of the grain is allowed to be transported. Even when the inside of the pipes are filled with a large amount of the grain, transportation can be performed, and the occurrence rate of crushing is low even at a high velocity owing to self-cushion among the grain. However, when the velocity V exceeds 20 m/s, the occurrence rate of crushing drastically increases, and therefore, the maximum value for μ is 40. 
     The control means  31  is connected with the first intercooler  15   a , the second intercooler  15   b , the third intercooler  15   c , and the fourth intercooler  15   d  as shown in FIG.  5  and it outputs instructions to the intercoolers  15  so that differences between the rice temperatures received from the rice temperature sensors and the transportation air temperature are controlled to be within a predetermined range. In order to cool gas warmed in the blowers  13 , the intercoolers  15  generally output instructions to coolant valves  71  for controlling coolant to control the temperature of the transportation air. More specifically, the control means  31  stores the temperatures of the rice and the temperature of the transportation air whose temperature difference from the rice temperature is within a range of ±15° C. and controls the intercoolers  15  so that the difference in temperature between the rice and the transportation air is within the range of ±15° C. More appropriately, the difference in temperature is controlled to be within a range of ±10° C. This temperature control and the control of the velocity and the blending ratio can realize more efficient pneumatic transportation of rice. 
     The control means  31  is also connected with the humidifying/dehumidifying devices  17   a ,  17   b ,  17   c , and  17   d  and outputs instructions to the humidifying/dehumidifying devices  17   a ,  17   b ,  17   c , and  17   d  so that the humidity of the transportation air is controlled to be equal to the equilibrium humidity of the rice. At this time, the control means  31  stores the value of the humidity of the transportation air as approximately 70% which is the equilibrium humidity of the rice and controls the humidifying/dehumidifying devices  17   a ,  17   b ,  17   c , and  17   d  so that the humidity of the transportation air is adjusted to be approximately 70% which is the equilibrium humidity of the rice after receiving the humidity signals of the transportation air from the humidity sensors  27   a ,  27   b ,  27   c , and  27   d.    
     Next, the procedure for supplying rice using the transportation apparatus  1  as structured above is explained. 
     First, the temperature of designated unpolished rice (for example, rice A) stored in the first storage tank  21  is measured by the corresponding unpolished rice temperature sensor  25  and a temperature signal indicating the measured temperature is transmitted to the control means  31 . The control means  31  determines the temperature of the transportation air according to the measured temperature of the unpolished rice, based on the result shown in FIG. 4, outputs an instruction to adjust the air flowing in the first intercooler  15   a  to be at the determined temperature, and puts the coolant valve  71  of the first intercooler  15   a  into operation. At this time, the control means  31  also outputs an instruction to the driving source for driving the first blower  13   a  so that the transportation air whose velocity V is in the range of 10 to 20 m/s is generated. The transportation air flowing in the first intercooler  15   a  is adjusted to be at the determined temperature and is supplied to the first transportation pipe  11   a . Furthermore, the humidity of the transportation air is measured by the humidity sensor  27   a  and a humidity signal indicating the measured humidity is transmitted to the control means  31 . The control means  31  outputs the instruction to the humidifying/dehumidifying device  17   a  so that the humidity of the transportation air is controlled to be equal to the equilibrium humidity (approximately 70%) of the rice, for example, by generation of vapor, and causes the transportation air to be supplied to the first transportation pipe  11   a.    
     When the transportation air flowing in the first transportation pipe  11   a  is kept at the determined velocity, temperature, and humidity, the control means  31  puts the rotary feeder  23   a  of the designated first storage tank  21   a  into operation and causes the unpolished rice A to be supplied to the first transportation pipe  11   a . The rotary feeder  23   a  is controlled so that this supply amount is within the range shown in FIG.  3 . This control can be performed by setting the supply amount at a value on the centerline in the parallelogram. More specifically, in FIG. 3, the blending ratio μ is controlled to be approximately 15, for example, when the velocity of the transportation air is set at 14 m/s. The unpolished rice A supplied to the first transportation pipe  11   a  is transported by the transportation air through the first transportation pipe  11   a  to flow into the rice polishing section  3 . Thereby, the unpolished rice transported through the first transportation pipe  11   a  is transported under the condition that the temperature difference between the rice and the transportation air is within the set temperature range, regardless of variation in the temperature of the rice depending on seasons such as summer or winter and so on. This makes it possible to reduce the occurrence of crushed granules and cracked granules of the rice. 
     The unpolished rice A flowing into the rice polishing section  3  is accommodated in a predetermined one of the first accommodation tanks  35  from the first transportation pipe  11   a  by the changeover operation of the branch valve  33  designated by the control means  31 . The accommodated unpolished rice A is polished by the corresponding rice polishing machine  37  provided on a downstream side thereof to be processed into half-polished rice. At this time, the temperature of the half-polished rice increases by approximately 20° C. due to the polishing operation by the rice polishing machine  37 . The half-polished rice whose temperature has increased is accommodated in the corresponding second accommodation tank  39  which is disposed on a downstream side of the rice polishing machine  37 . 
     When the rice is continued to be conveyed to a downstream process in the rice polishing process, the half-polished rice whose temperature has increased is supplied from the second accommodation tank  39  to the second transportation pipe  11   b  via the rotary feeder  23  which is operated according to an instruction given by the control means  31 . At this time, the velocity V of the transportation air and the blending ratio μ are also determined. Furthermore, the temperature of the half-polished rice in the second accommodation tank  39  is measured by the half-polished rice temperature sensor  41  and a temperature signal indicating the measured temperature is transmitted to the control means  31 . The control means  31  determines the temperature of the transportation air according to the measured temperature of the half-polished rice whose temperature has increased so that the temperature difference between the half-polished rice and the transportation air is within the predetermined temperature range, and the control means  31  outputs an instruction that the transportation air flowing in the second intercooler  15   b  should be adjusted at the determined temperature and puts the second intercooler  15   b  into operation. Thereby, the rice transported through the second transportation pipe  11   b  is transported under the condition that the difference in temperature between the transportation air and the rice is within the set temperature range even if its temperature increases by approximately 20° C. after being polished by the rice polishing machine  37 , which can reduce the occurrence of crushed granules and cracked granules. Furthermore, the humidity of the transportation air is measured by the humidity sensor  27   b  and a humidity signal indicating the measured humidity is transmitted to the control means  31 . Then, the control means  31  controls the humidifying/dehumidifying device  17   b  to adjust the humidity of the transportation air. The control means  31  also outputs an instruction to the driving device for driving the second blower  13   b  to cause the transportation air to be generated. The transportation air flowing in the second intercooler  15   b  is supplied to the second transportation pipe  11   b  while being controlled to be at the determined temperature and humidity. Then, the control means  31  puts the rotary feeder  23  of the second accommodation tank  39  into operation and causes the half-polished rice to be discharged to the second transportation pipe  11   b . The half-polished rice discharged to the second transportation pipe  11   b  is transported by the transportation air through the second transportation pipe  11   b  and transported to the rice bran removing section  4 . 
     In a case where the rice is transported to the subsequent process after it is temporarily accommodated and kept in the second accommodation tank  39 , the rice is supplied to the second transportation pipe  11   b  via the rotary feeder  23  which also operates according to the instruction from the control means  31 . At this time, the velocity V of the transportation air and the blending ratio μ are also determined. Furthermore, the temperature of the half-polished rice in the second accommodation tank  39  is measured by the half-polished rice temperature sensor  41  and a temperature signal indicating the measured temperature is transmitted to the control means  31 . The control means  31  determines the temperature of the transportation air according to the measured temperature of the half-polished rice whose temperature has increased, outputs an instruction that the air flowing in the second intercooler  15   b  should be adjusted to be the determined temperature, and puts the second intercooler  15   b  into operation. The humidity is also controlled by the humidity sensor  27   b  and the control means  31 , and the half-polished rice is sent to the rice bran removing section  4  through the second transportation pipe lib. 
     Thereafter, similar processing is performed up to the process performed by the blending section  6  for polished rice. 
     As described hitherto, according to the present invention, the occurrence of crushed granules and cracked granules of the rice during transportation can be reduced when the rice is pneumatically transported from the unpolished rice storage tanks to the rice polishing machines, from the rice polishing machines to the rice bran removing machines, from the rice bran removing machines to the polished rice storage tanks, from the polished rice storage tanks to the blended rice accommodation tanks, and so on. 
     Incidentally, in the above-described embodiment, the case where rice is transported is explained, but the present invention is applicable to gas transportation of other grain such as wheat and corn other than rice. Moreover, the transportation gas is not limited to air, and nitrogen gas, which is filled in the pipes in order to prevent explosion, can also be used for transportation. 
     As described hitherto, according to the present invention, the occurrence of crushed granules and cracked granules can be reduced when grain is transported by means of gas.