Patent Publication Number: US-2011064544-A1

Title: feed arrangement of a system for the processing of carbon containing raw material

Description:
The invention relates to feeding devices of plants for processing carbon-containing raw materials, such as gas producers, furnaces, boilers and the like, and can be used in plants for processing domestic and industrial waste. 
     A feeding device, in particular for a plant for burning material cut into pieces, designed in the form of a vertical downpipe and containing a feeding chamber and a sealable chamber arranged in a row one below the other, is known. The sealable chamber is separated from the feeding chamber and from the plant by closing elements, which are designed, for example, as slides with drives. 
     The disadvantage of this device is that, when processing (burning) plastic waste, in particular thermoplastics, and in view of the high temperatures in the plant, adhesion of the raw materials to be processed to the slide separating the sealable chamber from the plant may occur. The waste-gas temperature in the upper part of the plant exceeds 200° C., whereas the melting point of polyethylene, for example, is between 100 . . . 135° C. The adhesion of the raw materials to the slide may also lead to the jamming of the slide, resulting in stoppage not only of the feeding device but of the plant as a whole. Unplanned and planned downtimes for cleaning the slide reduce the productivity of the plant. 
     The object which the invention aims to achieve is to increase the operating reliability of the feeding device by preventing a possible adhesion of thermoplastic raw materials to be processed to the closing element separating the feeding device from the raw material processing plant. 
     The set object is achieved in that the feeding device of a plant for processing carbon-containing raw materials is designed in the form of a vertical downpipe fixed to the plant and contains three chambers in a row one below the other, to be precise the feeding chamber and two downwardly widening sealable chambers, the chambers being separated from one another and from the plant by driven closing elements; a gas flue with forced gas circulation, in the circuit of which flue a gas cooler is installed, and the inlet and outlet cross-sections of which flue are provided with closing elements and are arranged at the lateral surface of the middle chamber of the device. The sealable chambers are designed as truncated cones or truncated pyramids, and the inlet and outlet cross-sections of the gas flue accordingly lie in the upper and lower region of the middle chamber of the device. In the case of the conical design of the sealable chambers, the inlet and outlet cross-sections of the gas flue lie tangentially to the chamber. 
     If the sealable chambers are designed in such a way that they broaden downwardly, the area of contact of the raw materials to be processed with the chamber walls can be reduced, since the raw materials assume the shape of a downwardly broadening column as they fall from the feeding chamber into the middle sealable chamber. The raw materials only come into contact with the heated closing element. The likelihood of the raw materials to be processed adhering to the heated chamber walls is reduced. Unhindered passage of the raw materials through the feeding device is also ensured, which increases the operating reliability, in contrast, for example, to the prototype, in which the downwardly decreasing cross-section of the feeding chamber can lead to obstruction of the outlet opening, and this is found to be the case in practice. 
     Furnishing the device with a gas flue with forced gas circulation, in the circuit of which flue a gas cooler is installed, ensures the possibility of maintaining the required temperature in the middle chamber of the device at which no melting of the raw materials and adhesion thereof to the constructional elements of the device occurs, thereby increasing the operating reliability. The arrangement of the outlet cross-section of the gas flue in the lower part of the chamber enables optimum utilisation of the energy of the cooled gas for the cooling of the contact region of raw materials and the parts of the device, mainly in the region of the closing element. The gas heated in the chamber is made to circulate via the inlet cross-section of the gas flue, which lies in the upper part of the chamber. The arrangement of flaps in the inlet and outlet sections of the gas flue enables interruption of the gas circulation for the time of the opening of the closing elements separating the lower chamber from the chamber of the plant, and the middle and lower chambers, during the feeding of the plant with the next raw material batch. The hot and chemically aggressive gases from the plant do not get into the gas flue, they do not condense on the walls of the gas flue, thereby increasing the operating reliability. 
     In practice, the housing and closing elements of feeding devices are produced from available material which is resistant to elevated temperatures and aggressive media. Since the thermal conductivity of air is considerably lower than that of metal, the lower chamber of the device acts as a heat-insulating buffer between the chamber of the plant and the middle sluice chamber of the device. The energy used to maintain the temperature required to prevent the adhesion of the raw materials in the middle chamber of the device is reduced. The likelihood of condensation of the products of the raw materials to be processed on the surface of the closing element separating the chamber of the plant from the feeding device is reduced. 
     The arrangement of the inlet and outlet cross-sections of the gas flue tangentially to the walls of the middle chamber, which is designed as a truncated cone, ensures a uniform flow of the cooled gas flow around the raw material without the formation of accumulation zones, thereby reducing the likelihood of adhesion of the raw materials. 
     The use of the invention thus enables an increase of the operating reliability of the feeding device by preventing the adhesion of the raw materials to the working surfaces of the device. The presence of three closing elements reliably seals the chamber of the processing plant, emission of toxic substances is precluded, and the required process-technological regime is maintained in the chamber. 
    
    
     
       The feeding device is schematically illustrated in the drawing, in vertical section. 
     
    
    
     The feeding device  1  is designed as a vertical downpipe and fixed to the plant  2  for processing carbon-containing raw materials. The device  1  consists of the feeding chamber  3  and the two downwardly widening sealable chambers  4  and  5 , arranged in a row one below the other. The chambers are separated from one another and from the chamber of the plant  2  by the closing elements  6 ,  7  and  8  with drives. The device  1  is equipped with the gas flue  9  with forced gas circulation, in the circuit of which flue the gas cooler  10  is installed. The inlet cross-section  11  and the outlet cross-section  12  of the gas flue  9  are accordingly situated at the lateral surface in the upper and lower part of the sealable chamber  4  (sluice chamber) and are equipped with the flaps  13  and  14 . 
     The sealable chambers  3  and  4  can be designed as truncated cones or as truncated pyramids. The feeding chamber  3  can also be designed in the same manner. The closing elements  6 ,  7  and  8  can be designed as slides, flaps, etc. The device can be equipped with an operating console, upon the signals of which the closing elements  6 ,  7  and  8  and the flaps  13  and  14  are moved. A temperature sensor can be installed in the chamber  4  or in the gas flue  9 , the temperature and/or the speed of the cooling air flow circulating through the chamber  4  being regulated according to the readings of this sensor. Protective gratings and filters can be fitted at the inlet and outlet of the gas flue  9  to prevent obstruction of the gas flue and deposition on the walls of the latter of resinous substances released in the chamber  4 . 
     The feeding device works as follows. Raw materials to be processed, such as, for example, domestic waste containing plastic products—plastic bottles, plastic carrier bags, plastic packaging etc.—are poured into the feeding chamber  3  by a transport vehicle, for example. The closing elements  6 ,  7  and  8  are in the closed position. The closing element  6  is opened, and the raw materials pass into the chamber  4 , the flaps  13  and  14  are in the closed position, the closing element  6  is closed. By indirect heating via the closing elements  7  and  8  and the layer of air, lying therebetween, in the chamber  5 , the raw materials in the chamber  4  are heated and dried. The flaps  13  and  14  are opened, and the circulation of the cooling air flow through the chamber  4  via the gas flue  9  begins, the temperature of the flow being maintained below the melting point of the raw material components to prevent the raw materials from adhering to the heated metal surfaces of the device. When it is necessary to fill the next raw material batch into the processing plant  2 , the flaps  13  and  14  are closed and the closing elements  8  and  7  opened; thereupon, the raw materials pass from the chamber  4  through the chamber  5  into the plant  2 . Since the process of discharging the raw materials from the chamber  4  into the plant  2  takes place quickly, the closing element  7  is unable to heat up to the melting temperature of the raw material components, which prevents the adhesion thereof mainly to the closing element  7 . The closing elements  8  and  7  are closed, the closing element  6  is opened, and the next raw material batch passes into the chamber  4 . The cycle is repeated. The circulation of the cooling air flow through the chamber  4  is started when the temperature in the chamber  4  approaches the desired value, which is determined according to the qualitative composition of the raw materials. 
     The use of the invention enables an improvement of the operating reliability of the feeding device by preventing the adhesion of thermoplastic raw materials to the working surfaces of the device, thereby increasing the time between two preventive maintenance procedures. The productivity of the plant is increased when processing, in particular, domestic waste containing substances which are not subject to storage. The reliable sealing of the chamber of the plant prevents the emission of toxic substances and ensures that the required parameters of the technological process of the processing are observed.