Systems and devices for the pyrolysis of used plastics

Abstract

The present invention relates to the processing of waste plastics (used plastics) to obtain hydrocarbons for the production of fuel or further plastics. A method of controlling a process for pyrolysis, comprising: filling a reactor vessel with plastic material, processing the plastic material by heating the reactor vessel to pyrolyze the plastic material, driving an agitator in the reactor vessel to mix the material in the reactor vessel, and receiving hydrocarbon vapors from the reactor vessel, monitoring one or more parameters consisting of the load of the agitator, and / or a plurality of temperatures at a plurality of different heights in the reactor vessel, and / or the temperature of the vapors received from the reactor vessel, and modifying the heating and / or driving and / or terminating the process in response to the monitored parameters.

Description

[Technical field]

[0001] The present invention relates to the processing of waste plastics (post-consumer plastics) to obtain hydrocarbons for fuel or further plastics production. [Background technology]

[0002] Used plastic chemical recycling technologies are generally designed to recycle mixed waste plastics into a variety of liquid hydrocarbon products. These waste plastics are converted to liquid hydrocarbon products by feeding the plastic feed in molten form into a reactor vessel. The reactor vessel is externally heated by a combustion system to temperatures in excess of 350°C. This produces rich saturated hydrocarbon vapors from the molten plastics, which flow out of the reactor vessel through a contactor vessel, condensing the heavier vapor fractions. This is then distilled at near atmospheric pressure in a downstream atmospheric distillation column.

[0003] Systems for the pyrolysis of used plastics are known, such as in WO2011077419, WO2016030460 and WO2020065316. Summary of the Invention [Problem to be solved by the invention]

[0004] The exact composition of the source material is highly unpredictable, since the system is fed with material in the form of mixed waste post-consumer plastics. It can be sourced from any recycled plastic, from plastic bottles to plastic bags, with different properties and different impurities. The waste plastics used in such processes may contain, for example, low density polyethylene (LDPE), high density polyethylene (HDPE), polystyrene (PS), and / or polypropylene (PP). The amount of each of the different types of plastic is not known at the start of the process. As a result, it is difficult to predict the exact processing time of the plastic material, since this is highly material-dependent and may also depend on the feed rate and batch size.

[0005] There is a continuing need to improve the efficiency in such pyrolysis systems, not only in terms of the effectiveness of extracting hydrocarbons from the plastic material being processed, but also in terms of the energy efficiency of the overall process, which must be achieved in the context of an unpredictable supply of waste plastics. [Means for solving the problem]

[0006] Accordingly, below, methods and systems for controlling the pyrolysis process are presented, such methods and systems preferably configured for batch or semi-batch processing of plastic materials, as described below.

[0007] Drawing List For a better understanding of the present invention and to show how it may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings in which: [Brief description of the drawings]

[0008] [Figure 1]FIG. 1 shows a reactor assembly for processing plastic materials. [Diagram 2] FIG. 13 is a diagram showing an example of the change over time in the power required to drive an agitator. [Diagram 3] FIG. 1 is a diagram showing an example of a change in temperature distribution over time in a reactor vessel. [Figure 4] FIG. 1 is a schematic diagram of a reactor system. [Diagram 5] FIG. 2 is a schematic diagram of a mixing vessel. [Figure 6] FIG. 2 is a schematic diagram of a dehydration container. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Overall structure 4 depicts a reactor system 100 for the pyrolysis of plastic materials. The reactor system 100 includes a reactor vessel 1 as described with reference to FIG.

[0010] The reactor system 100 includes a reactor vessel 1 , an actuator 5 , an agitator 3 , a feed inlet 210 , a steam outlet 206 , a char outlet 208 , a heater 202 , sensor systems 110 , 112 , 114 , 116 , 118 , and a controller 204 .

[0011] The reactor vessel 1 has a feed inlet 210 for receiving a feed of plastic material. The reactor vessel 1 has a vapor outlet 206 for releasing hydrocarbon vapors.

[0012] The reactor vessel 1 has a char outlet 208 for exiting the char. The agitator 3 is for mixing the materials in the reactor vessel 1. Preferably, the agitator is as described with reference to FIG.

[0013] The agitator 3 is driven by an actuator 5. Preferably, the actuator 5 is a motor or an engine (preferably a motor) that drives the agitator 3 to rotate within the reactor vessel 1. Preferably, the actuator 5 is reversible.

[0014] Heater 202 is configured to heat the contents of reactor vessel 1. Preferably, heater 202 is a jacket that surrounds some or all of reactor vessel 1 to transfer heat from a heating fluid to the contents of reactor vessel 1. The jacket can receive a flow of a heated fluid, such as a combustion gas.

[0015] Sensor systems 110 , 112 , 114 , 116 , 118 monitor various operating parameters of the process and reactor system 100 .

[0016] The sensor systems 110 , 112 , 114 , 116 , 118 include a steam temperature sensor 118 downstream of the steam outlet 206 for producing a signal indicative of the temperature of the steam exiting the reactor vessel 1 .

[0017] The sensor systems 110, 112, 114, 116, 118 include an actuator sensor 116 for generating a signal indicative of an operating parameter of the actuator 5. The operating parameter may be indicative of a load on the agitator 3.

[0018] The sensor system 110, 112, 114, 116, 118 includes multiple temperature sensors 110, 112, 114 respectively positioned at multiple locations on the reactor vessel 1 for each generating a signal indicative of temperature. The temperature sensors are preferably on the exterior surface of the wall of the reactor vessel 1.

[0019] The controller 204 monitors the process as it proceeds within the reactor system 100 and controls the reactor system 100 .

[0020] The controller 204 monitors the signals received from the sensor systems 110 , 112 , 114 , 116 , and 118 .

[0021] The controller 204 controls the amount of heat supplied by the heater to the reactor vessel 1 as well as the rate and / or power supplied to the actuator 5 .

[0022] The reactor system 100 may also comprise a char discharge means (for actively discharging the charge rather than simply relying on gravity). In a preferred embodiment, this may include an agitator 3 and / or a central shaft auger 35 (possibly formed integrally with the agitator 3) as discussed with reference to FIG. 1. In such a case, the agitator 3 may be reverse drivable such that a downward force is applied through the char outlet 208 of the reactor vessel 1 to discharge the char from the reactor vessel 1. "Reverse" in this context means that the agitator 3 is opposite to the normal driving direction in which the agitator 3 is driven during processing, which is configured to lift the contents of the reactor vessel 1 and thus promote mixing.

[0023] Reactor vessel The pyrolysis process can be carried out in a reactor vessel 1 as shown in FIG. 1, which provides a non-limiting example of a suitable reactor vessel.

[0024] An agitator 3 may be rotatably mounted within the reactor vessel 1. The agitator 3 may include a central shaft 31 extending generally longitudinally within the reactor vessel 1. The agitator 3 is mounted to be rotatable about an axis X. The axis X is preferably approximately coincident with the central axis of the central shaft 31 and the upper and lower openings of the reactor vessel 1. A plurality of horizontal support bars 32 may extend from the central shaft 31 of the agitator 3. The horizontal bars 32 have a plurality of agitator blades 34 attached thereto. In alternative embodiments, other configurations of the agitator 3 may be used. The agitator 3 need only be configured to mix materials within the reactor vessel 1.

[0025] The agitator 3 is installed in the reactor vessel to improve several functions of the system. In particular, the agitator 3 can increase the thermal homogenization of the molten plastic mixture. This can shorten the reaction time by maximizing the heat transfer from the reactor vessel casing and preventing cold spots from forming. This thermal homogenization can further prevent the formation of vapor bubbles within the plastic mass of more volatile hydrocarbon chains. This can then reduce the risk of subsequent pressure and / or temperature spikes. The agitator 3 can remove problematic by-products (a substance known as "char") that lead to coking formation on the inner surface of the reactor vessel wall. Excessive accumulation of char can inhibit heat transfer from the reactor wall to the molten plastic. The agitator 3 can also aid in drying the char by continuously mixing it and bringing it into contact with hotter parts of the reactor vessel, such as the vessel casing. Finally, the agitator 3 can improve the removal of char by-products by pushing the char out of the reactor vessel.

[0026] While this embodiment includes multiple impellers 34, it is envisaged that the agitator 3 may be designed in any suitable manner. In particular, the agitator 3 may include one impeller 34 or three or more impellers 34 in alternative embodiments. The impeller 34 is generally helical such that it is generally spaced distally from the central shaft 31 at a constant distance. Thus, the outer edge of the impeller 34 is generally spaced at a constant distance from the inner surface of the reactor vessel 1. The impeller 34 may comprise an agitator base 33 at its lower end (either as a separate part or integral therewith). The base 33 generally conforms to the lower curved surface of the reactor vessel 1. The base 33 may be a separate component attached to the main portion of the impeller 34 or the base 33 may be integrally formed therewith.

[0027] The agitator 3 may further comprise a central shaft auger 35. This allows the agitator 3 to further operate in a "reverse" mode in which a downward force is applied by the central shaft auger 35 through the discharge nozzle of the reactor vessel 1 into the char hopper vessel, thereby discharging the char from the reactor vessel 1.

[0028] In other embodiments, the auger 35 may be provided separately from the agitator 3 and may act solely as a char discharge means.

[0029] The auger 35 may be located within the char outlet 208. When driven to rotate in one direction, the auger 35 may push char out of the reactor vessel 1 through the char outlet 35.

[0030] In use, plastic is fed into reactor vessel 1, preferably in the form of extruded molten plastic. Agitator 3 is driven to rotate, for example about axis X. Agitator blades 34 then rotate within the plastic, allowing it to be mixed throughout reactor vessel 1.

[0031] Although not required, the reactor system 100 is preferably used in a semi-batch process. By "semi-batch process" we mean that the processing of the plastic material can be started while the plastic material is still being fed into the reactor vessel 1, but the feeding of the plastic material stops at a given total charge and does not continue throughout the process as in a "continuous" process. The available hydrocarbon yield per batch depends on the exact composition of the plastic fed into the reactor vessel 1. However, the time required to dry the char by-product results in negligible hydrocarbon production. The rate at which the hydrocarbons are produced decreases towards the end of the process, resulting in a decrease in the efficiency of the process.

[0032] As the reactor system 100 operates, hydrocarbon vapors are discharged from the reactor vessel 1, changing the composition of the reactor contents remaining in the reactor vessel 1. The reactor contents comprise a mixture of hydrocarbons and char. As the process continues, the shorter chain hydrocarbons form vapors, leaving behind a waxy residue formed from (mainly) longer chain hydrocarbons mixed with the char. That is, the reactor contents comprise hydrocarbon vapors and residue that have not yet been discharged. As the hydrocarbon yield increases, the wax content of the residue decreases. This changes the viscosity of the residue.

[0033] Towards the end of the process, the wax content of the residue is reduced to form a solid that can be described as dry. Typically, at this point in the process, the ratio of wax content to char content of the residue is in the region of 5% to 12% by weight.

[0034] While maximizing the yield of hydrocarbons seems preferable, counterintuitively, the inventors have recognized that other benefits may result from intentionally not extracting the maximum yield of hydrocarbons. First, by not maximizing the yield, processing time can be significantly reduced. In one example, the last 15%-20% of the processing time produced only 5% of the total yield. Second, by not maximizing the yield, the overall energy efficiency of the system can be improved, since the end of the process results in less hydrocarbon vapor yield per unit of energy consumed.

[0035] Through extensive experimentation, the inventors have determined that a by-product residue having a wax to char ratio of between 2% and 20% by weight, preferably between 5% and 12% by weight, is particularly beneficial for downstream handling of the residue and provides an efficient process.

[0036] The inventors have realized that the progress of the process, and therefore the wax to char ratio, can be best established by reference to the timing of the agitator peak power consumption shown in Figure 2 and / or the temperature differential shown in Figure 3. These monitoring concepts are described below.

[0037] The ability to monitor a parameter that indirectly indicates the wax content of the residue makes it possible to control the wax content within the boundaries that allow a particular device to process the released by-product residue.

[0038] In particular, this allows for the preferred method of quenching the by-product residue via direct contact with a liquid such as water. While this is possible without the ability to precisely control the wax content of the residue, using a liquid for quenching is more difficult because the agglomeration of the discarded reactor contents may be too high to form an easily manageable slurry or too low to allow the slurry to be adequately dewatered.

[0039] One embodiment of a method for pyrolysis includes charging a reactor vessel with a plastic material, heating the reactor vessel to pyrolyze the plastic material (optionally, the heating step may overlap with the charging step), driving an agitator in the reactor vessel to mix the reactor contents within the reactor vessel, receiving hydrocarbon vapors from the reactor vessel, and releasing a residue formed from the remaining reactor contents.

[0040] Preferably, the residue is released when the wax has a wax content of between 2% and 20% by weight, preferably between 5% and 12% by weight.

[0041] The amount of wax in the residue cannot be measured directly, and furthermore, the wax content cannot be accurately estimated based solely on the amount of time the process has been running, since the feed composition, feed rate and exact batch size are unknown.

[0042] agitator load Figure 2 shows the change in power required to drive the agitator over time. While there has been some attention to using the agitator load to indicate that char drying is occurring, to date there has been no use of this information to modify the system operating parameters.

[0043] The agitator load can be determined, for example, based on the power, current or voltage used by an actuator, such as a motor driving the agitator 3, or by the torque of the force applied to the agitator 3 by the actuator 5 (motor, engine, etc.). Any such signal indicative of the agitator load is suitable to provide an indication of the viscosity of the residue. It has been found that the power consumed by the actuator 5 provides a convenient and reliable signal.

[0044] The inventors have realized that the agitator loading, due to its relationship to the viscosity and volume of the residue, can be used to provide an indirect indication of the wax content, which in turn can be used as an indirect indication of the ease of future processing (remaining reactor contents and end of processing) of the discharged by-product residue.

[0045] As mentioned above, the reactor contents change throughout the process as hydrocarbon vapors are obtained from reactor vessel 1, resulting in a decrease in the wax content of the residue.

[0046] In the early stages, as it becomes liquid, the reactor contents are at their lowest viscosity and have a low char-to-liquid ratio. During this stage, the resistance of the reactor contents to the agitator movement is low. Over time, the reactor contents increase in viscosity until finally reaching a maximum viscosity. Just before this point, there is a sudden increase in the resistance of the reactor contents to the agitator 3 movement, thereby increasing the agitator load on the actuator 5.

[0047] Following this point, the wax content of the residue is further reduced to form a solid which may be described as dry.

[0048] It has not previously been recognized that the agitator load can provide a reliable and sufficient indication of the state of the process within the reactor vessel 1 such that control parameters can be modified in response to this signal.

[0049] For example, in some cases it may be preferable to accelerate the drying rate of the residue towards the end of the process so that it can be released sooner. This may slightly reduce the hydrocarbon yield from a particular batch of source plastic material, but may significantly reduce the time and energy costs of processing each batch. Thus, the controller may be programmed to change the operating mode from pyrolysis mode to char drying mode to accelerate the drying of the char (i.e., removal of hydrocarbons from the residue). In the char drying mode, the heat provided by the heating jacket may be increased compared to the pyrolysis mode. Alternatively, or in addition, in the char drying mode, the drive speed of the agitator 3 may be increased compared to the pyrolysis mode.

[0050] In other cases, the agitator load signal can be used to initiate the discharge of the residue. Stall Protection In addition, the inventors have realised that monitoring the agitator load signal can provide an early warning that can be used to prevent stalling of an actuator 5, such as the drive motor of the agitator 3.

[0051] A recognized problem is that if the viscosity of the reactor contents increases too much, it can stall the agitator 3. When the agitator 3 stalls, it is often not possible to get the agitator 3 to start again.

[0052] In such cases, tedious manual procedures are required: First, the reactor system 100 must be shut down; Then, the reactor vessel 1 must be cooled; Then, the residues in the reactor vessel 1 must be manually removed; This can be very time-consuming, affecting the production rate of the entire process.

[0053] By monitoring the agitator load signal, the controller 204 can predict when the viscosity of the residue exceeds a threshold that would likely stall the agitator, and vary operating parameters to prevent stalling.

[0054] For example, the controller may compare the agitator load to a stall avoidance threshold that is a predetermined percentage of the stall load.

[0055] In response to determining that a stall is imminent, the controller may reduce the speed of the agitator 3 from its normal set point, e.g., rotational speed, thereby avoiding a stall.

[0056] More preferably, in some embodiments, a control system may be provided for adjusting the speed of the agitator 3 such that the agitator load is equal to a predetermined percentage of the stall load, which may be triggered in response to a determination that a stall is imminent.

[0057] In this manner, as the viscosity of the reactor contents decreases from the peak value, the agitator 3 can increase in speed until the agitator load drops sufficiently to return to the normal set point.

[0058] Reactor Temperature Measurement In a preferred embodiment, multiple temperature sensors 110, 112, 114 are provided to generate signals indicative of the temperature of the reactor contents adjacent the temperature sensors 110, 112, 114. The temperature sensors are provided at multiple locations at different heights on the reactor vessel 1.

[0059] Multiple temperature sensors 110, 112, 114 may be mounted on the outer casing of the reactor vessel 1, for example at different heights within the area of ​​the heating jacket. Because the heating jacket heats the outer surface of the reactor vessel 1 evenly, any temperature difference between the sensors 110, 112, 114 will result in the temperature of the reactor contents adjacent the temperature sensors 110, 112, 114.

[0060] The first temperature sensor 110 is preferably provided within the upper 50% of the height of the reactor vessel 1. The second temperature sensor 112 is preferably provided within the lower 20%-50% of the height of the reactor vessel 1. The third temperature sensor 114 is preferably provided within the lower 20% of the height of the reactor vessel 1.

[0061] For example, the reactor vessel 1 may be shaped with a generally cylindrical wall 122 sealed by a top surface 124 and a bottom surface 126. A first sensor 110 may be provided on the generally cylindrical wall 122 at a first height. A second sensor 112 may be provided on the generally cylindrical wall 122 at a second height that is lower than the first height. A third temperature sensor 114 may be provided on the bottom surface 126.

[0062] A first temperature sensor 110 measures a first temperature, a second temperature sensor 112 measures a second temperature, and a third temperature sensor 114 measures a third temperature.

[0063] Because the temperature sensors 110, 112, 114 are all within the area of ​​the heating jacket, when the reactor vessel 1 is empty, before filling, the temperature sensors 110, 112, 114 all record approximately the same temperature.

[0064] Thus, a first temperature distribution exists between the temperature sensors 110, 112, 114. The first temperature, the second temperature, and the third temperature are substantially equal.

[0065] The reactor vessel 1 is heated prior to being filled with the plastic material. Once filled, it melts (if not provided in liquid form) until it reaches a maximum level of liquid content. As hydrocarbon vapors are obtained from the reactor vessel 1, the liquid level drops.

[0066] The reactor vessel 1 is filled with plastic material to a level such that the first temperature sensor 110 is above the maximum level of any liquid reactor contents and the second temperature sensor 112 and the third temperature sensor 114 are below the level of any liquid contents.

[0067] Early in the process, when the reactor contents are liquid, the second temperature sensor 112 and the third temperature sensor 114 will record similar temperatures. The only difference is that the temperature of the reactor contents at the bottom of the reactor adjacent the third temperature sensor 114 is slightly lower due to the cooling influence of the cooler molten feed plastic. However, the temperature recorded by the first temperature sensor 110 will be much higher because there is no liquid at that altitude within the reactor vessel 1, which means that there is less transfer of heat from the walls due to reduced thermal conductivity.

[0068] Thus, a second temperature distribution exists between the temperature sensors 110, 112, 114. The first temperature exceeds the second temperature, and the second temperature is substantially equal to the third temperature.

[0069] As the process continues and hydrocarbon vapors are obtained from the reactor vessel 1, the liquid content decreases while the char content increases, decreasing the content level in the reactor vessel 1, resulting in a semi-liquid content with reduced thermal conductivity. As a result, the thermal conductivity of the reactor contents adjacent to the third temperature sensor 114 decreases, resulting in a higher temperature being recorded, while the temperature recorded by the second temperature sensor 112 approaches the temperature recorded by the first temperature sensor 110, which is slightly reduced. This is because the liquid level is lowering, and therefore the temperature throughout the reactor vessel 1 increases, but due to the presence of a highly insulating material at the bottom of the reactor vessel 1, this section is heated more than the upper section of the reactor vessel 1, reducing the heat transfer into the reactor vessel 1. Moreover, the presence of steam in the reactor vessel 1 can exacerbate this difference. This causes the first temperature sensor 110 and the second temperature sensor 112 to record lower temperatures than the third temperature sensor 114.

[0070] Thus, a third temperature distribution exists between the temperature sensors 110, 112, 114. The first temperature is substantially equal to the second temperature, and the second temperature is less than the third temperature.

[0071] Finally, after further processing, the semi-liquid contents become solid, resulting in a dry by-product (char mixed with wax) with limited production of hydrocarbon vapors. This dry by-product has a low thermal conductivity and therefore no longer absorbs heat from the walls of the reactor vessel 1. Thus, the temperature recorded by the third temperature sensor 114 increases.

[0072] Thus, a fourth temperature distribution exists between the temperature sensors 110, 112, 114. The first temperature, the second temperature, and the third temperature are substantially equal.

[0073] Thus, the temperature profile sensed by the multiple temperature sensors 110, 112, 114 changes predictably over time. The time course of the temperature profile can reliably indicate the stage of processing of the reactor contents in a manner that is robust to the composition of the feed material.

[0074] Further, referring to FIG. 3, it can be seen that while the individual temperatures peak at similar times, the bottom temperature (from the third temperature sensor 114) peaks more than the top (temperature sensor 110) and side (temperature sensor 112) temperatures. The inventors have found that the timing of the peak temperature difference is a useful indicator that peak viscosity is achieved. The peak temperature difference may be the difference between either the first temperature or the second temperature and the third temperature (or, optionally, the difference between the average or weighted sum of the first and second temperatures and the third temperature).

[0075] For example, (i) the difference between the first temperature and the third temperature; (ii) the difference between the second temperature and the third temperature; (iii) the difference between the third temperature and the average of the first and second temperatures; (iv) the difference between the third temperature and a weighted average (to compensate for different heights) of the first and second temperatures; etc.

[0076] Typically, the peak temperature difference is determined as the difference between temperatures measured at two locations that exceeds a temperature difference threshold, for example, the difference between a first temperature and a third temperature that exceeds the threshold. Preferably, the threshold is in the range of 50 degrees Celsius to 100 degrees Celsius.

[0077] Steam Temperature A steam temperature sensor 118 is provided to measure the temperature of the steam exiting reactor vessel 1 through steam outlet 206. The inventors have realised that this temperature also provides useful information regarding the state of the process within reactor vessel 1.

[0078] Specifically, when this temperature falls below a threshold, this can indicate a point in the process, the same as the agitator or temperature differential peak discussed above.

[0079] A suitable steam temperature threshold may be, for example, in the range of 90 degrees Celsius to 110 degrees Celsius, such as 100 degrees Celsius.

[0080] process A preferred embodiment of a batch process for pyrolysis includes charging a reactor vessel with plastic material, heating the reactor vessel to pyrolyze the plastic material, driving an agitator in the reactor vessel to mix the material in the reactor vessel, receiving hydrocarbon vapors from the reactor vessel, and monitoring one or more parameters of the process or system.

[0081] Monitoring the one or more parameters may involve monitoring the load on the agitator 3 (as described above), and / or multiple temperatures at multiple heights within the reactor vessel 1 (as described above), and / or the temperature of steam received from the reactor vessel 1.

[0082] The controller 204 controls the batch process. The controller can also modify the heating and / or driving based on the monitored parameters and / or terminate the batch process based on the monitored parameters.

[0083] Specifically, the controller 204 operates the reactor system 100 in one of several operating modes.

[0084] The controller 204 may be configured to operate the reactor system 100 in a normal pyrolysis mode, with the actuator 5 driving the agitator 3 at a first speed and the heater 202 generating a first amount of heat.

[0085] The controller 204 may be configured to operate the reactor system 100 in a trip avoidance pyrolysis mode in which the actuator 5 drives the agitator 3 at a second speed and the heater 202 generates a second amount of heat, the second speed being lower than the first speed.

[0086] Optionally, the controller 204 may be configured to operate the reactor system 100 in a char drying mode in which the actuator 5 drives the agitator 2 at a second speed and the heater 202 generates a second amount of heat, the second amount of heat being greater than the first amount of heat.

[0087] The controller 204 can be configured to operate the reactor system 100 in a char discharge mode in which the residue (including a mixture of char and wax) is discharged through a char outlet 208 .

[0088] Normal pyrolysis mode The controller 204 can implement a normal pyrolysis mode, in which the heater 202 heats the reactor vessel 1 to bring the reactor contents to a temperature between 390 degrees Celsius and 430 degrees Celsius. The agitator is driven to rotate at 30 and 40 revolutions per minute.

[0089] The controller 204 can implement a normal pyrolysis mode and then switch to another mode based on monitored parameters.

[0090] Trip-free pyrolysis mode For example, the controller 204 can detect an increase in the agitator load 3 to above a stall avoidance threshold (as described above) and then reduce the speed of the agitator 3 to avoid stalling the agitator 3. For example, the agitator 3 may be reduced in speed by 65%.

[0091] In a preferred embodiment, in trip avoidance pyrolysis mode, the agitator speed is adjusted to prevent the agitator load from exceeding the stall avoidance threshold.

[0092] Char drying mode In some embodiments, the controller 204 switches to the char drying mode based on monitored parameters. For example, as described above, the controller 204 can monitor parameters to estimate the point at which the wax content of the residue is between 2% and 20% by weight, preferably between 5% and 12% by weight.

[0093] One way this can be done is to monitor the timing of peak loads on the agitator 3, continue in normal pyrolysis mode for a period of time after the peak, and then switch to char drying mode.

[0094] Alternatively, the use of the temperature distribution signal can be used to establish when to switch to the char drying mode, which can be either the peak temperature difference being achieved or the tracked progression of the temperature difference having progressed to the third temperature distribution as described above.

[0095] A combination of temperature distribution and agitator peak load timing can be used by switching to char drying mode a period of time after sensing both the agitator peak load and the peak temperature difference, i.e., a period of time after the later of the agitator peak load and the peak temperature difference.

[0096] In the char drying mode, the controller 204 may control the heater 202 to heat the reactor vessel 1 to bring the reactor contents to a temperature of 420 degrees Celsius to 430 degrees Celsius, and control the actuator 5 to rotate the agitator 3 at 30 to 40 revolutions per minute. Typically, the char drying mode is implemented for a period of time before the controller 204 switches operation to the char discharge mode.

[0097] Char release mode In some embodiments, the controller 204 terminates the batch process based on the monitored parameters. For example, as described above, the controller 204 can monitor parameters to estimate the point at which the wax content of the residue is between 2% and 20% by weight, preferably between 5% and 12% by weight.

[0098] One way this can be done is to monitor the timing of peak load on the agitator 3, continue the process for a period of time thereafter, and then terminate the process and discharge the by-product residues via the char outlet 208.

[0099] Alternatively, this may be done by monitoring the timing of the peak temperature differential, continuing the process for a period of time thereafter, and then terminating the process and releasing the by-product residues via the char outlet 208.

[0100] Alternatively, this may be done by monitoring when the steam temperature drops below a steam temperature threshold, continuing the process for a period of time thereafter, and then terminating the process and releasing the by-product residues via the char outlet 208.

[0101] A preferred option is to monitor the timing of both the agitator peak and the peak temperature differential, continue the process for a period of time after determining that both peaks have occurred, and then terminate the process and discharge the by-product residues via the char outlet 208.

[0102] However, a steam temperature below the steam temperature threshold is a useful indication that can supplement any peak determination.

[0103] Therefore, the most preferred option is to monitor the timing of both the agitator peak and the peak temperature differential, and also monitor the steam temperature, continue the process for a period of time after a determination that both peaks have occurred and also that the steam temperature has fallen below the steam temperature threshold, and then terminate the process and discharge the by-product residue via char outlet 208.

[0104] The discharge process is preferably an automated (non-manual) process, for example using auger 35 as described above.

[0105] Quenching At the end of the process, the hot by-product residue must be discharged via the char outlet 208 .

[0106] A preferred method of by-product management of the released by-product residue involves quenching in a liquid to produce a slurry. The liquid is preferably water, but may include other solvents. Water is preferred due to the fact that it is easy to separate from the slurry for reuse and is not as volatile as the other solvents.

[0107] As noted above, one advantage of the disclosed method for monitoring the process state is that the residue can be released at a point when the residue has a predetermined wax content of 2% to 20% by weight, preferably 5% to 12% by weight. It is not essential that the wax content be between these limits, but these have been found to provide favorable properties for the slurry resulting from quenching the residue.

[0108] A preferred quench system includes a mixing vessel and a dewatering container (ie, a container for removing liquid, whether water or other liquid).

[0109] A preferred mixing vessel 300 is shown in Figure 5. The mixing vessel 300 includes a char inlet 308 in communication with the char outlet 208, and a slurry outlet 350.

[0110] Preferably, the mixing vessel is positioned directly below the reactor vessel 1 such that the char outlet 208 is directly above the char inlet 308 .

[0111] Preferably, the slurry outlet 350 is at the lower end of the conical lower section 340 of the mixing vessel 300 .

[0112] The mixing vessel 300 includes one or more liquid inlets 320. These are preferably tangentially positioned to provide a source of liquid with rotational momentum.

[0113] Mixing vessel 300 may be filled with a predetermined amount of liquid prior to receiving the by-product residue discharged from reactor vessel 1. In an alternative, but less preferred embodiment, liquid may be provided to mixing vessel 300 after the by-product residue is discharged into mixing vessel 300 from reactor vessel 1.

[0114] It is preferable to provide the liquid in the mixing vessel 300 first to reduce liquid loss due to evaporation.

[0115] The temperature of the by-product residue is likely to be at least 35 degrees Celsius and can be as high as 60 degrees Celsius. Thus, as the by-product residue enters the liquid in the mixing vessel 300, a significant amount of steam is generated. Thus, the mixing vessel 300 includes a steam outlet 310. The steam may also carry some hydrocarbon vapors, and therefore the steam outlet 310 may be in communication with a downstream steam scrubbing system.

[0116] To reduce agglomeration of the by-product residue within the liquid, the mixing vessel preferably includes an agitator 306, such as a rotatable impeller. The impeller keeps the by-product residue suspended and can also act to break up larger solids. In this manner, a slurry can be produced.

[0117] Moreover, when the liquid is fed into the mixing vessel 300 before the by-product residue, it may be agitated rather than static.

[0118] Once the slurry is generated and its temperature drops below the slurry temperature threshold, it may be discharged from the mixing vessel 300 via the slurry outlet 350.

[0119] The release of the slurry from the mixing vessel can be assisted by a pressurized source of inert gas via a gas inlet (not shown) at the top of the mixing vessel 300. The inert gas is preferably nitrogen. Again, the predetermined wax content is preferably within a preferred range, as the wax content and liquid content of the slurry determine its adhesive properties and therefore how easily it is propelled by the inert gas.

[0120] The slurry is discharged into a dewatering container 400 as shown in FIG. The dewatering container comprises a watertight container body 420 in which a perforated container 410 is supported. The base and walls of the perforated container 410 are spaced from the container body 420 so that liquids can drain into the container body 420 while solids are retained within the perforated container 410. The slurry is delivered into the perforated body 410 from the mixing vessel 300.

[0121] One or more vibration elements 430 are provided to vibrate the perforated container 410 relative to the container body 420 to aid in the separation of liquids from solids.

[0122] The walls and base of the perforated container preferably comprise a perforated plate or mesh lined with a liquid permeable fabric or membrane.

[0123] The container body 420 includes one or more filtrate outlets 440 for discharging liquid.

Claims

1. 1. A method of controlling a process for pyrolysis, comprising: Filling a reactor vessel with a plastic material; The plastic material heating the reactor vessel to pyrolyze the plastic material; driving an agitator within the reactor vessel to mix the materials within the reactor vessel; and receiving hydrocarbon vapor from said reactor vessel; and processing the One or more parameters, a) the load on the agitator, and / or a plurality of temperatures at a plurality of different heights within the reactor vessel; and b) the temperature of the vapor received from the reactor vessel. monitoring one or more parameters, wherein monitoring the agitator load includes identifying peaks in the agitator load; in response to the monitored parameter; Modifying the heating and / or driving, and / or terminating said process; A method comprising:

2. 10. The method of claim 1, wherein the monitored parameter is used to provide an indication of a wax content of the contents of the reactor vessel, the method comprising terminating the treatment in response to the monitored parameter indicating that the wax content is between 2% and 20% by weight, preferably between 5% and 12% by weight.

3. The method of claim 1 , wherein monitoring one or more parameters comprises identifying a predetermined distribution of temperatures monitored by a plurality of temperature sensors.

4. The method of claim 1 , wherein monitoring one or more parameters comprises determining that a time series of a predetermined distribution of temperatures has occurred.

5. 2. The method of claim 1, wherein monitoring one or more parameters comprises identifying a peak in a difference between temperatures measured by the plurality of temperature sensors, and modifying the heating and / or driving and / or terminating the process in response to the identification of the peak.

6. 2. The method of claim 1, wherein monitoring one or more parameters includes identifying when a steam temperature falls below a steam temperature threshold, and modifying the heating and / or driving and / or terminating the process in response to said identification.

7. Monitoring one or more parameters Identifying the occurrence of peaks in agitator load; identifying occurrences of peaks in differences between temperatures measured by the plurality of temperature sensors; In response to said identification of both peaks, modifying the heating and / or driving; and / or terminating said process; The method of claim 1 , comprising:

8. Monitoring one or more parameters Identifying the occurrence of peaks in agitator load; identifying occurrences of peaks in differences between temperatures measured by the plurality of temperature sensors; Identifying when the steam temperature is below a steam temperature threshold; in response to both peaks and the identification that the vapor has fallen below the vapor temperature threshold; Modifying the heating and / or driving, and / or terminating said process; The method of claim 1 , comprising:

9. The method according to any one of claims 5 to 8, wherein said modifying step and / or said terminating step is performed a predetermined period of time after said identification of said peak.

10. 10. The method of claim 1, comprising heating the reactor vessel to a higher temperature in response to the monitored parameter.

11. 2. The method of claim 1, further comprising decreasing the drive speed of the agitator in response to the monitoring of the agitator load.

12. 10. The method of claim 1, wherein the process is terminated in response to the monitored parameter, and wherein terminating the process comprises discharging the contents of the reactor vessel into a liquid.

13. 10. The method of claim 1, wherein terminating the process comprises discharging the contents of the reactor vessel into a mixing vessel holding a liquid.

14. 1. A method of controlling a process for pyrolysis, comprising: Filling a reactor vessel with a plastic material; heating the reactor vessel to pyrolyze the plastic material; driving an agitator within the reactor vessel to mix the materials within the reactor vessel; receiving hydrocarbon vapors from the reactor vessel; terminating the process by discharging the contents of the reactor vessel and mixing the discharging contents with a liquid; A method comprising:

15. The method of claim 14 wherein the liquid is water.

16. 15. The method of claim 14, wherein the contents of the reactor vessel are discharged into a mixing vessel and mixed with the liquid to form a slurry.

17. 17. The method of claim 16, wherein the liquid is fed to the mixing vessel prior to the discharged contents of the reactor vessel.

18. 18. The method of claim 16 or 17, wherein the slurry is passed to a dewatering container.

19. 20. The method of claim 18, wherein the slurry is forced into the dewatering container by pressurized inert gas.

20. 1. A method of controlling a process for pyrolysis, comprising: Filling a reactor vessel with a plastic material; heating the reactor vessel to pyrolyze the plastic material; driving an agitator within the reactor vessel to mix the materials within the reactor vessel; receiving hydrocarbon vapors from the reactor vessel; estimating the wax content of the reactor contents; discharging the contents of the reactor vessel when the estimated wax content is between 2% and 20% by weight, preferably between 5% and 12% by weight. A method comprising:

21. 1. A pyrolysis system comprising: A reactor for the pyrolysis of plastic materials, a reactor vessel having a feed inlet for receiving a feed of plastic material, a vapor outlet for releasing hydrocarbon vapors, and a char outlet for outputting char; an agitator for mixing materials within said reactor vessel; an actuator that drives the agitator; and a heater for heating the contents of the reactor vessel; a reactor comprising:

1. A sensor system comprising: an actuator sensor for generating a signal indicative of an operating parameter of the actuator, the operating parameter being indicative of a load on the agitator; and / or a plurality of temperature sensors positioned at a plurality of locations within the reactor vessel, each temperature sensor generating a signal indicative of temperature; and / or a steam temperature sensor for monitoring the temperature of the steam downstream of the steam outlet; a sensor system comprising: a controller in communication with the sensor system for controlling the reactor in one of a plurality of operating modes, the operating modes including: a pyrolysis mode in which the actuator drives the agitator at a first speed and the heater generates a first amount of heat; and Char discharge mode in which char is discharged through the char outlet Including, The controller a) the load on the agitator, or b) a plurality of temperatures at a plurality of different heights within the reactor vessel; and the temperature of the vapor received from the reactor vessel monitoring one or more parameters, wherein monitoring the agitator load includes identifying a peak in the agitator load; in response to said identifying a peak in the load of said agitator; or and a pyrolysis system configured to switch from the first one of the operating modes to the second one of the operating modes in response to monitoring the plurality of temperatures at the plurality of locations within the reactor vessel and the temperature of the vapor downstream of the vapor outlet.

22. 1. A pyrolysis system comprising: A reactor for the pyrolysis of plastic materials, a reactor vessel having a feed inlet for receiving a feed of plastic material, a vapor outlet for releasing hydrocarbon vapors, and a char outlet for outputting char; an agitator for mixing materials within said reactor vessel; an actuator that drives the agitator; and a heater for heating the contents of the reactor vessel; a reactor comprising: a char discharge system for discharging residue from the reactor vessel; a source of liquid, a mixing vessel in communication with the char outlet and the source of liquid to form a slurry of char and liquid; a char release system comprising: A pyrolysis system comprising:

23. 23. The pyrolysis system of claim 22, wherein the char discharge system further comprises an impeller within the mixing vessel.

24. 23. The pyrolysis system of claim 22, wherein the mixing vessel further comprises a steam outlet.

25. the char release system comprising: a dewatering container for receiving the slurry from the mixing vessel; an inert gas source; Furthermore, 25. The pyrolysis system of any one of claims 22 to 24, wherein the inert gas source is configured to drive slurry from the mixing vessel to the dewatering container.

26. 26. The pyrolysis system of claim 25, wherein the inert gas is nitrogen.

Images