Patent Publication Number: US-2023150778-A1

Title: Fluid control system in pneumatic conveying ducts for powdered or granular material

Description:
The present invention relates to a fluid control system in pneumatic conveying ducts for powdered or granular material. 
     In particular, the present invention relates to a system for regulating the operating parameters of the fluid that is supplied into ducts for handling the powdered or granular material along respective processing lines of such material. 
     For this purpose, the control system of the present invention finds particular application in pneumatic systems of various kinds, in which it is necessary to bring the granular material among different processing stations that may be of various types. 
     As is known, in systems of the type described above, the granular or powdered material is supplied into the passage ducts with the thrust of pressurized air (or vacuum in the case of suction of the material) or other pressurized gas suitably selected according to the type of material to be handled. 
     In this way, the fluid flow conveys and transports the material along the entire path of the plant which may be defined by one or more ducts in communication with each other. 
     Generally, the injection of the pressurized gas is carried out at specific points in the duct in order to generate a flow having optimal pressure and flow values, which translate into the conveying speed of the material. 
     Each injection point has a supply line of the pressurized gas, suitably connected to the duct and equipped with gas pressure and flow regulating devices. 
     According to a solution known and described in Italian Patent No. 01262314, a regulation is made at each specific injection point of the conveying gas by means of a manual air flow regulation valve and a self-regulating pressure valve controlled under pressure. 
     In this way, a manual adjustment of the pressure of each individual injection point is carried out (by means of a common pressure signal) and a pressure drop is introduced to reduce the flow rate resulting from the difference between the injection gas pressure and the back pressure inside the duct. In this regard, it should be specified that the back pressure inside the duct, under normal conditions, is always lower than the injection pressure of the conveying gas. 
     Japanese Patent Publication JPH11130257A also provides for a control and regulation system arranged near the powdered and/or granular product introduction zone, and adapted to supply said product along a respective line. 
    
    
     This document describes a valve-based regulation that regulates the flow passage section to obtain a constant downstream pressure. In this case the pressure regulation is manual and there are proportional automatic valves with shutters downstream capable of varying the flow passage section. 
     The known regulation systems, although capable of controlling the values of the gas conveying the granular or powdered material, nevertheless have some drawbacks and can be improved in several aspects. 
     These drawbacks primarily result from the manual regulation action by means of direct action on the flow rate regulation valve. In this context, in fact, the regulation operations at each gas injection point are particularly long and laborious, as they require manual intervention on each injection point present throughout the entire system. 
     Furthermore, the known systems do not allow to optimize the operating parameters depending on the type of granular or powdered material to be conveyed. 
     In this regard, it should also be considered that the same plant is used for conveying different materials and therefore they do not have the same behaviours in the individual transport steps relating to their nature and the particle size of the material itself. 
     In this context, the absence of a regulation of the operating parameters with respect to the material may result in an incorrect supply or even damage to the material itself inside the conveying ducts. 
     Moreover, the rigidity of the known systems in terms of flexibility in the variation of operating parameters, does not allow to maximize the flow rate and reduce gas consumption depending on individual needs, or in any case to optimize the conveying parameters compared to a target parameter in general. 
     In addition, known solutions that provide for injection only into the material inlet zone (as described in JPH11130257A), have the major drawback of not allowing the dispensing in separate individual blocks of material, in this case the material is pushed only from the launch zone and there is no possibility of managing the advancement directly along the line. Moreover, this document is not adaptable to the rapid variations in conditions on the line that cause, for example, pressure spikes. In this case, the regulation system would not be fast enough to cope with such variations. 
     In this context, the technical task underlying the present invention is to propose a fluid control system in pneumatic conveying ducts for powdered or granular material which overcomes the drawbacks of the prior art mentioned above. 
     In particular, an object of the present invention is to provide a control system that is able to control the injection of conveying gas at each single point and automatically in order to adapt at all times the optimal conveying conditions according to the specific operating needs and the characteristics of the granular or powdered material to be conveyed. 
     Furthermore, another object of the present invention is to provide a control system able to reduce the gas consumption in order to implement energy saving in the operation of the entire plant. Similarly, a further object is to use the device to optimize the system with respect to any objective parameter. 
     The outlined technical task and the specified object are basically achieved by a fluid control system in pneumatic conveying ducts for powdered or granular material comprising the technical specifications set out in one or more of the appended claims. 
     Further features and advantages of the present invention will be more apparent from the approximate, and hence non-limiting description of a preferred, but not exclusive, embodiment of a fluid control system in pneumatic conveying ducts for powdered or granular material, as illustrated in  FIGS.  1  to  3   , which show block diagrams in respective embodiments of the control system according to the present invention. 
     As shown in the appended figures, the reference number  1  globally indicates a fluid control system in pneumatic conveying ducts of powdered or granular material. 
     Preferably, the present invention relates to a control system  1  usable in plants of any type. For this purpose, a set of systems  1  of the present invention may be provided, located at different in-line injection sites within the same pneumatic system. 
     Each control system  1  is operative at a point for injecting pressurized gas into a respective pneumatic conveying duct  2  of the aforementioned powdered or granular material. Advantageously, a series of systems  1  are provided for the same duct  2 , each of which is arranged at specific pressurized gas injection points. These points are appropriately spaced in order to always obtain a control of the products’ advancement along the entire duct  2 . 
     The control system therefore comprises a plurality of sources  3  for supplying a pressurized gas, such as air, nitrogen or other gases suitably selected according to the type of material to be handled. 
     It should be specified that in the appended drawings only one section of the duct  2  at a single source  3  is illustrated purely by way of example. The present invention, however, comprises a series of gas supply sources  3  at respective injection points  2   a  suitably spaced along the duct  2  from a product loading station to an unloading station. 
     The gas supplied by each source  3  is conveyed inside the duct  2 , at the respective injection point  2   a  by means of a gas injection line  4 . The injection line  4 , consisting of suitable connection pipes, puts the source  3  in fluid communication with the respective conveying duct  2  inside which the material is handled. 
     The system  1  also comprises a plurality of self-regulating pressure valves  5 , each arranged on the injection line  4  between the source  3  and the injection point  2   a . 
     Preferably, the self-regulating pressure valve  5  is a pressure-controlled valve. The valve  5  is in a determined “no relieving” configuration, thus it is adapted to prevent the entry of a return gas (“dirty” gas) from the duct  2 . In fact, in conditions where the pressure inside the duct  2  is greater than the regulating pressure, the gas may return towards the valve  5 . 
     Other technically equivalent devices may be provided and adapted to prevent the return of “dirty” gas. 
     The system  1  also comprises a plurality of control members  6  of the respective self-regulating valves  5  for providing a control signal to each valve  5  representing a pressure value. 
     The valve  5  regulates the gas pressure as a function of the control signal and keeping the supplied gas flow in the duct  2  constant. 
     In other words, unlike what is described above with reference to the state of the art in which the regulation system is active on the flow by moving the gas passage section, in this case each valve  5  intervenes on the pressure regulation while maintaining the flow constant. 
     A plurality of flow and flow rate meters  7  are further provided, each arranged on the injection line  4  upstream of a respective valve  5  and configured to transmit a flow and flow rate value to the control member  6 . 
     Advantageously, a pressure meter  8  may also be provided arranged on the injection line  4  downstream of the valve  5  and close to the injection point  2   a  to transmit to the control member  6  a pressure value detected at the duct  2 . 
     According to a first embodiment diagrammed in  FIG.  1   , each control member  6  is in the form of a local integrated electronic device  9  comprising a current/pressure converter. 
     In this situation, the local integrated electronic device  9  can be associated with a centralized control unit  10  which manages a plurality of control systems  1 . 
     In other words, the centralized unit  10  is associated with a plurality of local integrated electronic devices  9  each of which operating on a respective injection line  4 . 
     Advantageously, it is possible to intervene directly on the local control member  6  to change the operating parameters in the single injection line  4 . Alternatively, the centralized unit  10  may command a series of control members  6  of respective systems  1  separately located in a single plant to change the transport parameters along the entire duct  2  into which the gas is injected. 
     According to a second embodiment shown in  FIG.  2   , the control member  6  comprises a local proportional valve  11  controlled by a centralized electronic unit  10 . 
     Also in this case, the centralized electronic unit  10  (e.g., a PLC) is associated with a plurality of control members  6  of respective systems  1  each of which is operatively active on a respective injection line  4 . 
     In this situation, which does not provide for the possibility of local intervention, the flow and flow rate meter  7  and the possible pressure meter  8  are directly connected to the centralized electronic unit  10 . 
     Still, in accordance with a further embodiment illustrated in  FIG.  3   , the self-regulating valve  5  is provided with a current/pressure converter  12 . In this situation, the control member  6  is not local but is in the form of a centralized electronic unit  10 . 
     Thus the regulation of each valve  5  is implemented only centrally, to change the operating parameters in each gas injection line  4  that may be present in a plant. 
     Accordingly, also in this case the flow and flow rate meter  7  and any pressure meter  8  are directly associated with the centralized electronic unit  10 . 
     The system  1  described above in the three embodiments therefore maintains a flow value in each line  4  which is constant and continuously set remotely by means of the pressure command generated by each control member  6 . 
     At the same time, a remotely adjustable maximum pressure limit value is set for each individual valve  5  by the control member  6 . 
     In this way, a regulation is obtained that maintains the gas flow introduced into the duct  2  constant without allowing the same gas to exceed a maximum pressure limit value that is considered optimal for the system  1  under certain conditions. 
     This limit value is in fact set according to the type of powdered or granular material, or according to the gas injection zone. 
     In addition, the pressure value detected by the meter  8  near the injection site  2   a  may be used to modify the control criteria and adjustment parameters and to adapt the local or general parameters to the new system conditions. 
     Furthermore, the gas injection flow rate (required in the specific point  2   a ) is reduced when the pressure value in the duct  2  is lower than a predetermined threshold value. Advantageously, under certain conditions it is therefore possible to reduce the gas consumption in line  4 , obtaining a considerable energy saving. 
     Likewise, when the pressure at the injection point  2   a  exceeds a fixed value, the system  1  may decide to use optimized parameters with respect to the new condition that in this case could be of incipient blockage of the transport line. The latter condition therefore determines a safety measure for the entire system and the material handled in the respective ducts  2 . 
     In other words, for each line  4  a self-regulating valve  5  is provided, controlled under pressure, which intervenes on the pressure regulation in a mechanical way in order to regulate the flow thereof. 
     Advantageously, the system intervenes very quickly, limiting any pressure peaks due to regulation transients in the face of rapid changes in conditions (typical in direct injection along the duct). 
     Note that in the present invention the injection is not limited at the loading zone of the product. In fact, the lines  4  inject the gas along the entire extension of the duct  2  and at predefined distances. 
     In this situation, it is possible to separate the product into blocks and push the blocks from the various injectors distributed on the duct  2 . 
     The thrust of each block is controlled and it is possible to intervene quickly on the various pressure peaks derived precisely from the separate passage of these blocks. 
     Further to the above, the possibility of introducing a fixed pressure drop by means of a needle valve or calibrated orifice may also be provided. 
     In this way, the regulation of the system is made more precise within the range of use.