WO2025125709A1

WO2025125709A1 - Method for recovering metal and arrangement

Info

Publication number: WO2025125709A1
Application number: PCT/FI2023/050673
Authority: WO
Inventors: Mathias STENLUND; Changji XUAN; Pär LINDBERG; Ove BERGQVIST; Joakim VENNSTRÖM
Original assignee: Metso Metals Oy
Current assignee: Metso Metals Oy
Priority date: 2023-12-11
Filing date: 2023-12-11
Publication date: 2025-06-19
Anticipated expiration: 2026-06-11

Abstract

A method and an arrangement for recovering metal from recycled materials comprising organic substances. The method comprises: feeding a batch of recycled coarse material into a top blown rotary converter (1), preheating the top blown rotary converter (1) and the batch of recycled coarse material to a temperature sufficient for combusting organic substances but below melting temperature of said metal, feeding continuously a main recycled material, comprising said organic substances, maintaining temperature sufficient for combusting organic substances but below melting temperature of said metal, combusting said organic substances, raising the temperature of the top blown rotary converter (1) to or over melting temperature of said metal and melting said metal, and discharging melted metal from the top blown rotary converter (1).

Description

METHOD FOR RECOVERING METAL AND ARRANGEMENT

BACKGROUND

The invention relates to a method for recovering metal from recycled materials comprising organic substances .

The invention further relates to an arrangement for carrying out the method for recovering metal from recycled materials comprising organic substances .

The recycling of scrap materials plays a vital role in resource conservation and the establishment of a sustainable economy . The rapid advancement of technology and the economy has led to a substantial increase in the production of various material s containing significant amounts of organic substances . Consequently, there has been a significant rise in the volume of related scrap materials in recent decades . For example consumer electronic devices have relatively short service lives due to factors like frequent innovations in new products and rapid changes in equipment features . As a result , global e-waste production has experienced substantial growth and is expected to continue increasing in the near future . These scrap materials , such as e-waste , copper scrap with insulation cables , and lead scrap from batteries , comprise a complex mixture of high-value metals (e . g . , Cu, Pb, Sn, Au, Ag, etc . ) , plastics , and hazardous components . The high levels of organic constituents in these materials ' present significant challenges for recycling due to the substantial energy generation and the emis sion of hazardous substances during the process of expelling organics .

BRIEF DESCRIPTION

Viewed from a first aspect , there can be provided a method for recovering metal from recycled materials comprising organic substances , the method comprising : ( a) feeding a batch of recycled coarse material into a tiltable and rotatable top blown rotary converter,

(b) preheating the top blown rotary converter and the batch of recycled coarse material therein to a temperature sufficient for combusting organic substances but below the melting temperature of said metal ,

( c) feeding continuously a main recycled material , comprising said organic substances , until a predetermined batch quantity in the top blown rotary converter is reached,

(d) maintaining a sufficient temperature for combusting organic substances but below the melting temperature of said metal , combusting said organic substances and generating a reducing atmosphere , preventing the undesired oxidation of the metal in the top blown rotary converter,

(e ) guiding off-gas created in the combustion of organic substances out from the top blown rotary converter,

( f ) raising the temperature of the top blown rotary converter to or over the melting temperature of said metal and melting said metal , and

(g) discharging melted metal from the top blown rotary converter .

Thereby many advantages may be achieved . The implementation of continuous feeding results in a more uniform and stable reaction condition compared to conventional batch-wise feeding methods . Throughout the feeding process , temperature , off-gas flow and composition, and material composition variations remain at stable and adj ustable levels . This allows for the smooth monitoring of measuring parameters and the necessary adj ustment of process control variables . Moreover, continuous feeding simplifies the operational process by eliminating multiple steps inherent in batch- wise feeding, ultimately improving efficiency . Keeping temperature sufficient for combusting organic substances but below melting temperature of said metal creates a reducing atmosphere within the top blown rotary converter and prevents an undesired oxidation of valuable metal ( s ) during the continuous feeding .

Viewed from a further aspect , there can be provided an arrangement for carrying out the method for recovering metal from recycled materials compri sing organic substances according to the first aspect .

Thereby many advantages may be achieved . The implementation of continuous feeding results in a more uniform and stable reaction condition compared to conventional batch-wise feeding methods . Throughout the feeding process , temperature , off-gas flow and composition, and material composition variations remain at stable and adj ustable levels . This allows for the smooth monitoring of measuring parameters and the neces sary adj ustment of process control variables . Moreover, continuous feeding simplifies the operational process by eliminating multiple steps inherent in batch- wise feeding, ultimately improving efficiency . Keeping temperature sufficient for combusting organic substances but below melting temperature of said metal creates a reductive atmosphere within the top blown rotary converter and prevents an undesired oxidation of valuable metal ( s ) during the continuous feeding .

The method and the arrangement are characterised by what is stated in the independent claims . Some other embodiments are characterised by what is stated in the other claims . Inventive embodiments are al so disclosed in the specification and drawings of this patent application . The inventive content of the patent application may also be defined in other ways than defined in the following claims . The inventive content may also be formed of several separate inventions , especially if the invention is examined in the light of expressed or implicit sub-tasks or in view of obtained benefits or benefit groups . Some of the definitions contained in the following claims may then be unnecessary in view of the separate inventive ideas . Features of the different embodiments of the invention may, within the scope of the basic inventive idea, be applied to other embodiments .

Various embodiments of the first aspect may comprise at least one feature from the following paragraphs :

In one embodiment the top blown rotary converter comprises a mouth and at least one taphole separate from said mouth, wherein the method comprises

- feeding the materials through the mouth in the top blown rotary converter,

- tilting the top blown rotary converter and discharging flowable slag therefrom through the mouth by prior to discharging melted metal , and

- rotating the top blown rotary converter and discharging melted metal therefrom through the at least one taphole .

In one embodiment , the method comprises rotating the top blown rotary converter to a position where the taphole is at lower position than the mouth after said discharging flowable slag .

In one embodiment , the method comprises a predetermined waiting time after melting said metal and prior to discharging the top blown rotary converter for releasing metal droplets entrapped in the slag .

In one embodiment , the method comprises raising temperature to an overheat state in the top blown rotary converter prior to discharging melted metal . In one embodiment , the method comprises skimming and removing slag from melted metal by a slag skimming device prior to discharging said melted metal .

In one embodiment , the method comprises monitoring melted metal in the top blown rotary converter during discharging by a quality detection system, and

- interrupting or ending said discharging in case a predetermined amount of slag is detected .

In one embodiment , the method comprises providing an upstream feeding system for receiving the main recycled material from one or more material source , and

- feeding the main recycled material in the top blown rotary converter .

In one embodiment , the method comprises providing a charge bin system for receiving the mixture of the main recycled material from the upstream feeding system, and

- feeding continuously said mixture from the charge bin system in the top blown rotary converter .

In one embodiment , the method comprises providing a waste heat boiler comprising an after-burner boiler having a first water circulation arrangement ,

- guiding off-gas from the top blown rotary converter in said after-burner boiler, and

- cooling said off-gas by water circulating in the water circulation arrangement .

In one embodiment , the method comprises feeding additional air into the after-burner boiler, and

- combusting gaseous compounds of the off-gas in said afterburner boiler . In one embodiment , the method comprises providing the waste heat boiler with a radiation chamber boiler comprising a second water circulation arrangement ,

- guiding off-gas from the after-burner boiler in said radiation chamber boiler, and

- cooling said off-gas further .

In one embodiment , the method comprises rotating the top blown rotary converter around its longitudinal axis (X) with

- a lower rotational speed during preheating, and

- a higher rotational speed during feeding the main recycled material .

In one embodiment , the method comprises feeding a secondary feeding material with the main recycled material in the top blown rotary converter .

In one embodiment , the method comprises controlling said combusting of organic substances by measuring at least one measuring parameter selected from the following list :

( i ) off-gas temperature of the waste heat boiler,

( ii ) steam flow in the waste heat boiler and

( iii ) CO -content in off-gas flowed through the gas cleaning system ( 19 ) , and

- controlling the feeding of the main recycled material by at least one control variable selected from the following list :

( i ) material feeding rate into the top blown rotary converter,

( ii ) total oxygen flow rate into the top blown rotary converter, and

( iii ) flow rate of the additional air into the after-burner boiler .

In one embodiment , the method comprises defining two ranges for the measuring parameter : a design range limiting the maximum and minimum threshold values , and an operational range which is located within the design range and is narrower than said design range , and the method comprises

- controlling said feeding of the main recycled material so that the measuring parameter is in its operational range , and

- implementing an interlock function in case one of the measuring parameters is out of its design range for a predetermined period of time , wherein the interlock function comprises

- shutting off the material feeding and oxygen flow into the top blown rotary converter .

Based on the above , it should be noted that different embodiments mentioned in the above paragraphs may combined in any possible suitable manner for implementing the present invention .

BRIEF DESCRIPTION OF FIGURES

Some embodiments illustrating the present disclosure are described in more detail in the attached drawings , in which

Figure 1 is a schematic view of a step of a method for recovering metal from recycled materials comprising organic substances in partial cross-section,

Figure 2 is a schematic view of another step of said method for recovering metal from recycled materials comprising organic substances in partial cross-section,

Figure 3 is a schematic view of a third step of said method for recovering metal from recycled materials comprising organic substances in partial cross-section, Figure 4 is a schematic view of a fourth step of said method for recovering metal from recycled materials comprising organic substances in partial cross-section, and

Figure 5 is a schematic end view of a top blown rotary converter .

In the figures , some embodiments are shown simplified for the sake of clarity . Similar parts are marked with the same reference numbers in the figures .

DETAILED DESCRIPTION

Figure 1 is a schematic view of a step of a method for recovering metal from recycled materials comprising organic substances in partial cross-section .

The method is run in an arrangement 100 the main parts or components of which comprise a tiltable and rotatable top blown rotary converter 1 , a feeding arrangement 13 arranged for feeding materials in said top blown rotary converter, and a waste heat boiler 8 arranged for handling off-gas of said top blown rotary converter .

The top blown rotary converter 1 is shaped like an open- ended barrel and inside lined with refractory material . The top blown rotary converter 1 can be rotated about its longitudinal axis X and tilted about an axis Y perpendicular to said longitudinal axis X .

In one embodiment , such as shown in Figures , the top blown rotary converter 1 comprises not only a mouth 2 but also at least one taphole 3 separate from said mouth 2 . In one embodiment , the the top blown rotary converter 1 has one taphole 3 . In another embodiment , there is a plurality of tapholes 3 , such as two , three , four or even more .

The arrangement 100 is a part of a pyrometallurgy plant . At the beginning of the method, it is fed or loaded a batch of recycled coarse material into the top blown rotary converter 1 through a mouth 2 thereof. Said recycled coarse material may comprise e.g. recycled coarse material that has been generated within the pyrometallurgy plant. Said recycled coarse material may comprise e.g. slag lumps, that contains metal oxides, blocks of material scraps comprising metal (s) , such as copper, etc. In one embodiment, particles or lumps of this material have typically size up to tens of centimetres, or even more.

During the feeding of the coarse material, the top blown rotary converter 1 may be positioned in an alternative position, for example in an upright position as shown by dashed lines in Figure 1. In the loading it may be used means like a skip hoist or a feeding boat.

As the top blown rotary converter 1 is filled with a desired amount of coarse material, the top blown rotary converter 1 and the batch of recycled coarse material therein is preheated to a temperature that is sufficient for combusting organic substances (that will be fed in the following method step in the top blown rotary converter 1) , but below melting temperature metal or metals to be fed in the top blown rotary converter. In one embodiment, the top blown rotary converter 1 is positioned at an incline, such as shown in Figure 1, during the preheating.

In one embodiment, the preheating is realized by a heating system comprising at least one burner, such as gas burner, or electric heaters. In one embodiment, the heating system comprises a burner lance 14 supplied with natural gas.

In one embodiment, the top blown rotary converter 1 is rotated slowly around its longitudinal axis X for minimizing dust emissions during the preheating process . In one embodiment , rotational speed during the preheating process is in range of 1 - 3 rounds per minute .

After the desired temperature has been reached in the preheating, a continuous feeding of a main recycled material is started . The term "continuous feeding" does not preclude short interruptions in introducing the main recycled material in the top blown rotary converter 1 .

The main recycled material is typically crushed in form of particles and fragments , and its s i ze is typically substantially finer than the coarse material . The main recycled material may originate from many sources . In one embodiment the main recycled material compri ses electronic scrap , cable scrap, and plastic scrap from electrical or electronic devices . In one embodiment the main recycled material comprises insulation or isolation materials that comprises organic material and metal , such as copper .

In one embodiment , a secondary feeding material is fed with the main recycled material in the top blown rotary converter 1 . The secondary feeding material may comprise e . g . dust removed from the flue gases of the arrangement 100 and fluxes from bins etc .

In one embodiment , the top blown rotary converter 1 is rotated around its longitudinal axis X while feeding the main recycled material with a higher rotational speed than in the preheating . This is for maintaining a sufficient and homogeneous reaction environment in the top blown rotary converter .

In one embodiment , rotational speed during the continuous feeding of the main recycled material is in the range of 3 - 10 rounds per minute . In one embodiment , the main recycled material , and the secondary feeding material , if any, is continuously introduced into the top blown rotary converter through the mouth 2 by means of material gravity coupled with pneumatic transport gas , e . g . pressuri zed air . In one embodiment , said feeding is reali zed by a feeding lance 15 . The dimensions of the feeding lance 15 are designed to facilitate a smooth transport of the main recycled material while meeting certain si ze requirements . In dimensioning of the feeding lance 15 , as well as other lances , such as a burner lance and a gas lance , it may be taken into account the si ze and capacity of the top blown rotary converter, the characteristics of the materials to be handled, etc .

The pressuri zed gas or air fed by the feeding lance 15 may serve two primary functions : firstly, it facilitates the feeding process , and secondly, it provides a portion of the required oxygen for the combustion reaction .

The feeding lance 15 is movable in and out of the top blown rotary converter 1 through a hydraulic-powered or another type of system carriage .

The feeding lance is preferably equipped with a water cooling to withstand high temperatures inside the top blown rotary converter 1 . In one embodiment , a water-cooling safety system is provided to shut off water feed in the feeding lance and automatically retracting the feeding lance from the top blown rotary converter in case of a cooling water system leak .

In one embodiment , the feeding lance 15 is provided with a hydraulic-powered or another type of system carriage that is preferably provided with a safety system for electric power failure . Said safety system is configured to retract the feeding lance 15 from the top blown rotary converter 1 in the event of an electric power failure . The safety system for electric power failure may comprise e . g . a pressure tank (part of the cooling water lances unit ) or other device that may supply sufficient power to retract the feeding lance 15 from the top blown rotary converter .

In one embodiment , the feeding arrangement 13 comprises an upstream feeding system 6 that is arranged for receiving recycled material from one or more material sources . This recycled material comprises at least the main recycled material , and the secondary feeding material if present . The upstream feeding system 6 may comprise multiple units , for instance conveyors . Regardless of the number of units or material sources , the upstream feeding system 6 is preferably controlled so that it provides one continuous flow, where the material quantity is kept as constant as possible regardless of the material flow setpoint and transport speed .

In one embodiment , the recycled material is fed from the upstream feeding system 6 into the top blown rotary converter 1 , optionally through the feeding lance 15 . In another embodiment , such as shown in the Figures , the feeding arrangement 13 is provided with a charge bin system 7 that is arranged to receive the recycled material from the upstream feeding system 6 into a charge bin, and feed said material continuously from the charge bin into the top blown rotary converter 1 , typically through the feeding lance 15 .

The charge bin system 7 may ensure a continuous supply of the recycled material into the top blown rotary converter, even if the upstream feeding system 6 faces malfunctions . The charge bin system 7 comprises one or more charge bins . In one embodiment , a feeder, like a screw feeder or a chute , is located beneath the charge bin for feeding the material from the charge pin forwards .

In one embodiment , the charge bin system 7 comprises a ventilation .

In one embodiment , the charge bin system 7 comprises a weighing scale to monitor the feeding material ' s weight . The weighing scale may provide valuable weight data for predictive guidance and adj ustment of the upstream feeding system .

In one embodiment , the charge bin system 7 comprises a valve for inspection and maintenance during non-operation .

Figure 2 a schematic view of another step of said method for recovering metal from recycled materials comprising organic substances in partial cross-section .

The expulsion of organic substances occurs through a combustion reaction with oxygen . This exothermic reaction generates high temperatures in the converter, thanks to the high heat values of organic substances , especially plastics . The method is controlled such that temperature is sufficient for maintaining the combustion of organic substances but below the melting temperature of metal ( s ) in the recycled material , and such that said combusting generates a reductive atmosphere that prevents , or at least substantially reduces , the oxidation of metal ( s ) in the top blown rotary converter .

In one embodiment , the temperature sufficient for maintaining the combustion of organic substances but below the melting temperature of metal ( s ) in the recycled material is selected such that it is 100 ° C - 400 ° C below the melting temperature of the metal ( s ) in the recycled material .

The combustion reactions taking place in the top blown rotary converter are typically not complete ones but result in a significant amount of reductive and combustible offgases , such as carbon monoxide and hydrogen . The reductive atmosphere in the domain helps prevent unwanted oxidation of valuable metals .

In one embodiment , additional oxygen for the combustion reactions is supplied by either the burner lance 14 or a gas lance 16 or the material feeding lance 15 or combinations of two or more of said lances . The gas lance 16 may have a similar structure as the burner lance , but it is arranged to feed air or oxygen-containing gas or gas mixture .

In one embodiment , off-gas created in the combustion of organic substances is guided out from the top blown rotary converter 1 into a waste-heat boiler 8 through a gas hood 17 . In one embodiment , said off-gas combines with air A incoming through a gap between the mouth 2 of the top blown rotary converter and the gas hood 17 . The gas hood 17 is preferably water-cooled and connected to the waste heat boiler 8 .

In one embodiment , the waste-heat boiler 8 comprises two maj or sections : an after-burner boiler 9 and a radiationchamber boiler 11 . In one embodiment , the after-burner boiler 9 comprises a first water circulation arrangement 10a, and the radiation-chamber boi ler 11 comprises a second water circulation arrangement 10b . In one embodiment , the first water circulation arrangement 10a is separate from the second water circulation arrangement 10b . In another embodiment , the first water circulation arrangement 10a is connected to the second water circulation arrangement 10b such that they create a common water circulation arrangement .

A continuous supply of circulation water, preferably at a constant temperature , is provided through the first and the second water circulation arrangements 10a, 10b as well as through the water-cooled gas hood 17 . Heat transfer occurs between the off-gas and said circulation water, resulting in the generation of steam, which in one embodiment is collected in a waste heat boiler steam condenser (not shown) .

In one embodiment , the after-burner boiler 9 comprises an air feed 18 arranged for feeding additional air and combusting gaseous compounds of the off-gas in the after-burner boiler 9 . Thus , the final combustion of gaseous compounds takes place in the after-burner boiler 9 .

Following the after-burner boiler 9 , the off-gas proceeds into the radiation chamber boiler 11 for initial cooling . Subsequently, off-gas undergoes cleaning and further cooling in a gas cleaning system 19 , from which cleaned and cooled off-gas exits the arrangement . Exiting off-gas has typically temperature below 100 ° C and contains a relatively small amount of dust . These characteristics allow a reliable measurement of the CO ( carbon monoxide ) and CO2 ( carbon dioxide ) contents of said off-gas . According to an aspect , the desired CO content target is zero or as close to zero as possible .

The continuous feeding of the main recycled material , and the secondary material , if any, is continued until its amount reaches the predefined batch quantity in the top blown rotary converter 1 . After the combustion reaction in the top blown rotary converter 1 , the remaining material no longer contains organic compounds . The end of the combustion reaction can be theoretically calculated or estimated on basis of the characteristics of the recirculated material , or observed by measurements , such as decreasing temperature of the top blown rotary converter 1 or material therein . The remaining material is in a softened solid state , possibly with some liquid phases . Then the temperature of the top blown rotary converter 1 is raised to or over melting temperature of metal ( s ) in the top blown rotary converter 1 in order to melt said metal ( s ) . In one embodiment , said temperature is about 1300 ° C .

In one embodiment the burner lance 14 is used here . In this connection, the rotational speed may be increased to ensure adequate agitation .

Once the melting is completed, the material has separated into two phases : a slag phase and a liquid metal phase . Then, the arrangement is ready for the next step of the method, i . e . discharging of the top blown rotary converter . In one embodiment , the method comprises a predetermined waiting time prior to discharging the top blown rotary converter for releasing entrapped metal droplets in the slag phase and allow them to settle into the liquid metal phase . It is worth noting that the slag volume may be several times larger than the metal volume .

The method and the arrangement 100 are controlled through the control unit 12 , which may be a computer, a computation unit or a device comprising at least one processor and a memory .

During the step of continuous feeding of the main recycled material , the method requires that both an adequate degree of combustion is achieved and that an appropriate domain temperature is maintained below, or preferably slightly below, the melting temperature of metal ( s ) in the main recycled material . To ensure precise control of the operation, preferably several measuring parameters are continuously monitored and employed to regulate process control variables .

In an ideal scenario , the feeding of the main recycled material , and the secondary material if any, have a uniform composition and si ze . However, due to the complexity of the material , variations in gas composition, gas flow rate , and temperature over time may be expected .

In one embodiment , the control of the method and the arrangement comprises controlling said combustion of organic substances by measuring at least one measuring parameter selected from ( i ) off-gas temperature of the waste heat boiler 8 , ( ii ) steam flow in the waste heat boiler 8 , and ( iii ) CO-content in off-gas flowed through the gas cleaning system 19 .

Achieving an instant reaction to adj ust process control variables can be challenging, mainly due to factors like analyser response times and the inherent time lag in the control systems . Therefore , in one embodiment , the control of the method and the arrangement comprises that two ranges are defined for each of the measuring parameters : a design range and an operational range . The design range defines the maximum and minimum threshold values for the measuring parameter, whereas the operational range is located within the design range and is narrower than said design range . So , there is a safety buffer between the design range and the operational range to allow for the resolution of abnormal processes within a reasonable time frame . This safety buffer provides a buffer to address issues before they become critical.

According to an aspect, in selecting the operational range it is taken into consideration not only the proper function of the process and the arrangement, but also costs resulting from structural aspects, wear and maintenance of the arrangement 100. Thus, the investment costs and the running costs of the arrangement may be optimized.

During normal operation, each of the measuring parameters should remain within its operational range. If one or more of the measuring parameters exceeds the corresponding operational range, i.e. shifts out of its operational range, a signal is generated to adjust the process by adjusting at least one control variable. In one embodiment, the control variable is at least one control variable selected from (i) material feeding rate into the top blown rotary converter 1, (ii) total oxygen flow rate into the top blown rotary converter 1, and (iii) flow rate of the additional air into the after-burner boiler 9. In one embodiment, said adjustments are carried out automatically by the control unit 12. However, manual interventions may be necessary to ensure flexible and reliable control in response to changing conditions .

According to an aspect, the creation of a reductive atmosphere within the top blown rotary converter is critical to prevent the undesired oxidation of valuable metal (s) during continuous feeding. The reducing atmosphere is achieved through a systematic control philosophy that oversees the entire process chain, covering the feeding arrangement 13, the top blown rotary converter 1, and the off-gas treatment system. This comprehensive approach allows for the accurate and prompt resolution of any process anomalies while ensuring process quality and safety. According to an aspect , the material feeding rate into the top blown rotary converter 1 may be the most complicated factor to control . In embodiments where the feeding arrangement 13 is provided with a charge bin system 7 , the material is transported from upstream feeding system 6 to the charge bin system 7 and continuously dosed therefrom, for instance through a charge bin feeder, into the feeding lance 15 . In this embodiment , the control variable of material feeding rate into the top blown rotary converter may directly reflect the status of the charge bin or the charge bin feeder . According to an aspect , the goal is to create a synergy between the material flow from the upstream feeding system 6 to the charge bin system 7 and the material flow from the charge bin system 7 to the feeding lance 15 . However, maintaining flow homogeneity and continuity from the upstream feeding system 6 to the charge bin system 7 can be challenging due to e . g . material and structural complexity . The charge bin system offers an advantage by maintaining continuous feeding rate in the top blown rotary converter within a specified timeframe , even in the event of malfunctions in the upstream feeding system . Furthermore , the weight data of the material in the charge bin system 7 may serve as valuable predictive guidance , ensuring a seamless process , and may act as a clear reference for adj usting operation status of the upstream feeding system .

In one scenario , the off-gas temperature of the waste heat boiler 8 and/or steam flow in the waste heat boiler fall below the corresponding lower limit of the operational range . This issue can be responded by increasing the material feeding rate into the top blown rotary converter 1 and the total oxygen flow rate into the top blown rotary converter 1 . This adj ustment aims to achieve a stable and efficient reaction within the top-blown rotary converter 1 . In one scenario , the CO-content in off-gas flowed through the gas cleaning system 19 exceeds the upper limit of its operational range . This may indicate that the terminal combustion process in the after-burner boiler 9 is not ful ly completed, even when the combustion reaction in the top blown rotary converter 1 is operating normally . In one embodiment the response to this deviation is to increase the value of the control variable of the flow rate of the additional air into the after-burner boiler 9 . This adj ustment facilitates the terminal combustion process in the afterburner boiler 9 . Once the deviation in CO-content in offgas flowed through the gas cleaning system 19 disappears , suggesting that the terminal combustion is success fully completed, the flow rate of the additional air into the after-burner boiler 9 is gradually reduced back to its initial setting . This way unnecessary cooling of the off-gas is prevented, ensuring efficient operation of the system .

I f the off-gas temperature of the waste heat boiler 8 and/or the steam flow in the waste heat boiler 8 , but not the CO- content in off-gas flowed through the gas cleaning system 19 exceed their respective operational range upper limits , it indicates that an excessive volume of off-gas is entering the waste heat boi ler 8 , generating high energy . This s ituation may indicate that the terminal combustion in the after-burner boiler 9 is fully executed, but the combustion reaction in the top blown rotary converter 1 is too intense and needs to be reduced .

In this scenario , the material feeding rate into the top blown rotary converter 1 and the total oxygen flow rate into the top blown rotary converter 1 may be decreased to reduce the combustion reaction in the top blown rotary converter 1 . Since the material feeding rate and oxygen flow rate typically follow a certain proportion based on the design of the arrangement , it is advantageous to adj ust both of said control variables to achieve the desired reduction . In one embodiment , the flow rate of the additional air into the after-burner boiler 9 is additionally increased to enhance the cooling of the off-gas as it passes through the after-burner boiler 9 .

In still another scenario , if also the CO-content in the off-gas flowed through the gas cleaning system 19 exceeds the upper l imit of its operational range concurrently with the off-gas temperature of the waste heat boiler 8 and the steam flow in the waste heat boiler 8 , the flow rate of the additional air into the after-burner boiler 9 should be even more significant . This adj ustment is important to ensure both a complete terminal combustion and an effective cooling of the off-gas in after-burner boiler 9 .

In all the scenarios , once the deviation signals disappear, i . e . , value of the measuring parameter is again in its operational range , all the related process control variables are returned to their initial values to maintain normal system operation .

In one embodiment , an interlock function is implemented in case one of the measuring parameters is out of its design range for a predetermined period of time . The interlock function comes into use in extreme situations where an abnormal measuring parameter cannot be adequately corrected and exceeds the upper limit of the design range . In such cases , if the issue persists and cannot be resolved within a defined time range , the system automatically shut off the material feeding and the oxygen flow into the top blown rotary converter 1 . This action allows the off-gas l ine to self-correct by dissipating excess energy or eliminating excess CO before restarting the process , preventing potential safety hazards or equipment damage . Figure 3 a schematic view of a third step of said method for recovering metal from recycled materials comprising organic substances in partial cross-section .

In one embodiment , the moment when all or at least sufficient portion of metal ( s ) in the top blown rotary converter is melted is precalculated based on thermodynamical properties of materials in the top blown rotary converter and heating energy used in the process .

In one embodiment , following melting of metal ( s ) in the top blown rotary converter 1 and prior to discharging thereof , there is a predetermined waiting time . During the waiting time , the top blown rotary converter is preferably rotated around the longitudinal axis thereof . The purpose of the predetermined waiting time is to release metal droplets entrapped in the slag . The length of the predetermined waiting time depends on the characteristics of the metal ( s ) and the slag .

In order to discharge the top blown rotary converter 1 , it is tilted T to a position where the slag can flow out through the mouth 2 . In one embodiment , the temperature of the top blown rotary converter and the material therein is briefly raised to prevent a decrease in temperature , which can increase slag viscosity and even lead to slag solidification .

In embodiments where the top blown rotary converter 1 comprises not only the mouth 2 but also at least one taphole 3 separate from the mouth, the top blown rotary converter 1 is tilted so that the at least one taphole 3 is and stays above the mouth 2 . Then the flowable slag is discharged through the mouth 2 but not through the at least one taphole 3 . As previously mentioned, the slag volume can be much larger than the liquid metal volume after full smelting, creating a risk of slag entrapment when tapping metal from the top blown rotary converter . In one embodiment , the discharging of the slag is intensified by a slag skimming device 4 prior to discharging melted metal . In one embodiment , the slag skimming device 4 is a device controlled by the control unit 12 . In another embodiment , the slag skimming device 4 is a manually operated device , operated e . g . from a control cabin (not shown) equipped with a suitable control panel , and comprising preferably a heat radiation protection and air conditioning . Remote control machines are also available for the slag skimming .

Following the slag discharge , optionally enhanced by skimming, only liquid metal and a minor amount of slag remain in the top blown rotary converter .

Figure 4 a schematic view of a fourth step of said method for recovering metal from recycled materials comprising organic substances in partial cross-section, and Figure 5 is a schematic end view of a top blown rotary converter .

Following the slag discharge , the metal phase is discharged from the top blown rotary converter 1 . In embodiments where the the top blown rotary converter 1 does not comprise the at least one taphole 3 separate from the mouth 3 , the metal phase is poured through the mouth by tilting the top blown rotary converter 1 .

In embodiments where the the top blown rotary converter 1 comprises the at least one taphole 3 , the top blown rotary converter 1 is rotated around its longitudinal axis X to a position where the at least one taphole is at lower position than the mouth 2 , and then melted metal is discharged, optionally combined with a further tilting, through the at least one taphole 3 .

Figure 5 is showing an embodiment of the top blown rotary converter 1 . This embodiment comprises the mouth 2 and three tapholes 3 separate from the mouth . In the embodiment shown in Figure 5 , the tapholes 3 are positioned to a cone of the top blown rotary converter 1 . Both the mouth 2 and each of the tapholes are round . The number of tapholes may vary from one to more than three . The position and the number of tapholes as well as the si ze or the cross-sectional area thereof , are selected according to the requirements of the process .

The separate taphole ( s ) 3 allow ( s ) the discharged metal to form a concentrated j et flow, minimi zing the risk of metal re-oxidation .

Near the end of the discharging of the metal , the levels of slag and metal may reverse rapidly . To prevent slag discharge with the metal and/or entrapment thereof in the taphole 3 , a quality detection system 5 (e . g . , magnetic monitor, imaging camera) can be provided . The quality detection system 5 is configured to quickly terminate the discharging process . The quality detection system 5 may be arranged to control the tilting and/or the rotating of the top blown rotary converter such that the discharging process is stopped or at least interrupted .

An advantage of having a plurality of tapholes 3 is that , if some of the tapholes get blocked, e . g . due to slag, there may still be a taphole open and allowing the discharge .

Following the discharge of the metal phase , any remaining slag can be tapped from the top blown rotary converter through the mouth 2 . The obtained metal can undergo any suitable further processing after the discharge , such as refinement in a separate furnace .

The invention is not limited solely to the embodiments described above , but instead many variations are possible within the scope of the inventive concept defined by the claims below . Within the scope of the inventive concept, the attributes of different embodiments and applications can be used in conj unction with or replace the attributes of another embodiment or application .

The drawings and the related description are only intended to i llustrate the idea of the invention . The invention may vary in detail within the scope of the inventive idea defined in the following claims .

REFERENCE SYMBOLS

1 top blown rotary converter

2 mouth

3 taphole

4 slag skimming device

5 quality detection system

6 upstream feeding system

7 charge bin system

8 waste heat boiler

9 after-burner boiler

10a, b water circulation arrangement

11 radiation chamber boiler

12 control unit

13 feeding arrangement

14 burner lance

15 feeding lance

16 gas lance

17 gas hood

18 air feed

19 gas cleaning system

100 arrangement

A air

DI discharge of slag

D2 discharge of metal

M melted metal

R rotation

S slag

T tilting

X longitudinal axis

Y perpendicular axis

Claims

1. A method for recovering metal from recycled materials comprising organic substances, the method comprising:

(a) feeding a batch of recycled coarse material into a tiltable and rotatable top blown rotary converter (1) ,

(b) preheating the top blown rotary converter (1) and the batch of recycled coarse material therein to a temperature sufficient for combusting organic substances but below the melting temperature of said metal,

(c) feeding continuously a main recycled material, comprising said organic substances, until a predetermined batch quantity in the top blown rotary converter (1) is reached,

(d) maintaining a sufficient temperature for combusting organic substances but below the melting temperature of said metal, combusting said organic substances and generating a reducing atmosphere, preventing the undesired oxidation of the metal in the top blown rotary converter (1) ,

(e) guiding off-gas created in the combustion of organic substances out from the top blown rotary converter (1) ,

(f) raising the temperature of the top blown rotary converter (1) to or over the melting temperature of said metal and melting said metal, and

(g) discharging melted metal from the top blown rotary converter ( 1 ) .

2. The method as claimed in claim 1, wherein

- the top blown rotary converter (1) comprises a mouth (2) and at least one taphole (3) separate from said mouth, wherein the method comprises - feeding the materials through the mouth (2) in the top blown rotary converter (1) ,

- tilting the top blown rotary converter (1) and discharging flowable slag therefrom through the mouth (2) prior to discharging the melted metal, and

- rotating the top blown rotary converter (1) and discharging the melted metal therefrom through the at least one taphole (3) .

3. The method as claimed in claim 2, comprising

- rotating the top blown rotary converter (1) after said discharging flowable slag to a position where the taphole (3) is at a lower position than the mouth (2) .

4. The method as claimed in any of the preceding claims, comprising

- a predetermined waiting time at the end of melting said metal and prior to discharging the top blown rotary converter (1) for releasing metal droplets entrapped in the slag .

5. The method as claimed in any of the preceding claims, comprising

- raising temperature to an overheat state in the top blown rotary converter (1) prior to discharging the melted metal.

6. The method as claimed in any of the preceding claims, comprising

- skimming and removing slag on melted metal by a slag skimming device (4) prior to discharging said melted metal.

7. The method as claimed in any of the preceding claims, comprising

- monitoring melted metal in the top blown rotary converter (1) during discharging by a quality detection system (5) , and - interrupting or ending said discharging in case the quality of the discharged metal turns low.

8. The method as claimed in any of the preceding claims, comprising

- providing an upstream feeding system (6) for receiving the main recycled material from one or more material sources, and

- feeding the main recycled material in the top blown rotary converter ( 1 ) .

9. The method as claimed in claim 8, comprising

- providing a charge bin system (7) for receiving the mixture of the main recycled material from the upstream feeding system ( 6) , and

- feeding continuously said mixture from the charge bin system (7) into the top blown rotary converter (1) .

10. The method as claimed in any of the preceding claims, comprising

- providing a waste heat boiler (8) comprising an afterburner boiler (9) having a first water circulation arrangement (10a) ,

- guiding off-gas from the top blown rotary converter (1) in said after-burner boiler (9) , and

- cooling said off-gas by water circulating in the first water circulation arrangement (10a) .

11. The method as claimed in claim 10, comprising

- feeding additional air into the after-burner boiler (1) , and

- combusting gaseous compounds of the off-gas in said afterburner boiler (9) .

12. The method as claimed in claim 10 or 11, comprising - providing the waste heat boiler (8) with a radiation chamber boiler (11) comprising a second water circulation arrangement (10b) ,

- guiding off-gas from the after-burner boiler (9) in said radiation chamber boiler (11) , and

- cooling said off-gas further.

13. The method as claimed in any of the preceding claims, comprising

- rotating the top blown rotary converter (1) around its longitudinal axis (X) with

- a lower rotational speed during preheating, and

- a higher rotational speed while feeding the main recycled material .

14. The method as claimed in any of the preceding claims, comprising

- feeding a secondary feeding material with the main recycled material in the top blown rotary converter (1) .

15. The method as claimed in any of the preceding claims, comprising

- controlling said combustion of organic substances by measuring at least one measuring parameter selected from the following list:

(i) off-gas temperature of the waste heat boiler (8) ,

(ii) steam flow in the waste heat boiler (8) , and

(iii) CO -content in off-gas flowed through the gas cleaning system (19) , and

(i) material feeding rate into the top blown rotary converter ( 1 ) ,

(ii) total oxygen flow rate into the top blown rotary converter ( 1 ) , and ( iii ) flow rate of the additional air into the after-burner boiler ( 9 ) .

16 . The method as claimed in claim 15 , comprising

- defining two ranges for the measuring parameters : a design range between the maximum and minimum threshold values , and an operational range which is located within the design range and is narrower than said design range , and the method comprises

- shutting off the material feeding and oxygen flow into the top blown rotary converter ( 1 ) .

17 . An arrangement ( 100 ) for carrying out the method for recovering metal from recycled materials comprising organic substances as claimed in any of the preceding claims .