JPS6129899B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to the production of heated aggregate mixes, particularly bitumen-containing mixes. The invention involves feeding a cold aggregate mix and a bituminous binder to a reactor, which is in the form of an elongated hollow rotatable drum, and heating the feedstock within the reactor so that most of the moisture in the feedstock is removed. It is particularly, but not exclusively, applicable to processes that transform the raw material into a bitumen-containing mix in which the binder adheres to and coats the aggregate particles as they evaporate and are carried away from the drum in the air current.

Various types of reactors have been proposed for the above-mentioned method. These reactors generally have a liquid or gas fuel burner at one end of the drum with one or more air intakes that provide the oxygen necessary to complete combustion. at the same time as creating a heated air flow through the burner. In conventional reactors, an air atomizing burner blows a flame into a drum and the aggregate mix is heated by contact with the flame. The binder, on the other hand, is introduced into the thermal mix substantially beyond the reach of the flame.

With such known reactors, it is possible to liquefy the binder and remove enough moisture to obtain the desired specific thermal mix, while keeping the oxidative losses of the binder within acceptable limits. proved to be difficult. Inhaling large amounts of fines into the exhaust stream causes significant dust problems in many prior art systems, while also atomizing the burner fuel and blowing out the flame. On the other hand, the high air velocities required to remove the fine powder are often accompanied by an unacceptable amount of noise. These problems are
It is also present when the bituminous binder is not added to the drum, but rather to the batch of heated unbound aggregate mix removed from the drum.

So far, efforts have been made to reduce these difficulties by using sophisticated equipment that suppresses dust and noise, or by performing the mixing process of raw materials and additives in multiple stages to avoid the formation of free fine powder inside the drum. Measures were taken to prevent this from happening. However, the former measure is expensive, and the latter has the disadvantage that the degree of bitumen oxidation is unreasonably high and the bitumen is lost to the exhaust stream. Alternatively, attempts have been made to reduce airflow requirements by using more complex burners that mechanically atomize liquid fuel, instead of the relatively simple air atomization burners traditionally used. There are some, but
We know it's only a temporary stopgap.

The invention is based on the discovery that advantageous results can be achieved by monitoring conditions within the drum and controlling airflow from the drum in response to the monitored conditions.

The invention thus provides, first of all, a body defining a closed processing chamber which is rotatable about a predetermined longitudinal axis and which is arranged to tumble its contents during rotation; one or more inlet ports for supplying raw materials containing mixes to the processing chamber; an ejection port for removing heated mixes from the processing chamber; an inlet port for introducing gas, an exhaust port for exhausting gas from the processing chamber at or near the other end of its axis, means for creating a gas flow from the processing chamber to the gas exhaust port; and a reactor for producing a heated aggregate mix, comprising: a burner for heating the raw material within the processing chamber to a temperature sufficient to convert the feedstock into a heated mix of desired specification; A reactor is provided, characterized in that it includes means for monitoring one or more parameters indicative of conditions at the location and means for controlling said gas flow through the processing chamber in response to said monitoring.

The position of the burner relative to the raw material introduction port,
Preferably, the location is such that the gas stream is heated before it contacts the raw material, and the heated gas stream heats the raw material and converts it into heated mix.

Advantageously, the gas flow control means comprises a flow rate (volume rate) control valve arrangement associated with the gas discharge port. This valve arrangement is capable of removing gaseous combustion products and unburned gases and water vapor to the extent necessary to reduce moisture in the heat mix products to a predetermined level, regardless of the rate of oxygen combustion by the burner. The device is arranged to operate in response to said monitoring to determine the withdrawal rate (volumetric rate).

An exhaust fan with a constant degassing rate may be provided in the exhaust duct communicating with the gas exhaust port, and the valve device may be provided with an adjustable exhaust fan provided in the exhaust duct between the gas exhaust port and the fan. It may be equipped with a lead means.

Furthermore, the gas flow control means preferably includes a flow rate (volume rate) control valve arrangement attached to the burner. The valve arrangement is connected to a device for measuring the temperature of the mix being removed from the process chamber, so that air and fuel intake to the burner can be controlled in response to said temperature measurements.

In addition, the reactor is equipped with a means for mixing the raw materials before supplying them to the processing chamber and for stabilizing and homogenizing them to a considerable extent, if not completely, to prevent dust formation during the reaction. It is advantageous to have as little as possible.

The invention also provides for feeding a raw material containing an aggregate mix into a closed processing chamber, maintaining a gas flow through said processing chamber, and converting said raw material into a desired specific heated mix within said processing chamber. A method for producing a heated aggregate mix by tumbling the same while heating to a sufficient temperature and removing the heated mix from the processing chamber, wherein the processing is performed during the gas flow maintenance and raw material heating steps. A method is provided comprising monitoring one or more parameters indicative of conditions at one or more locations within the chamber and controlling the gas flow through the processing chamber in response to this monitoring.

In a preferred embodiment of the invention, the mix production process is completely controlled by monitoring only the temperature of the heated product mix and the net gas pressure within the processing chamber. Under normal conditions, the values of these two variables are expected to reasonably reflect other variables of the product such as moisture and production rate.

The invention further provides for feeding a raw material containing aggregate mix into a closed processing chamber, maintaining a flow of gas containing air longitudinally through said processing chamber, and heating said raw material within said processing chamber to a desired degree. in a method for producing a heated aggregate mix, in which the heated mix is tumbled while being heated to a temperature sufficient to convert it into a heated mix, and the heated mix is removed from the processing chamber, before the gas stream contacts the raw material. The method is characterized in that the raw material is heated by heating the gas stream to convert it into a heated mix of the desired specification.

In a particularly advantageous embodiment of the method of the invention,
The raw material supplied to the processing chamber contains a bitumen-based binder, and such raw material is tumbled and heat treated to form a heated bitumen-containing mix in which the binder is adhesively coated onto the aggregate particles.

Referring to the accompanying drawings, the plant shown in FIG. 1 is advantageously located at or near the location where the aggregate mix is actually extracted and used. The illustrated plant includes four easily disassembled subplants, a storage distribution system 10, and a pug mill.
mill) 12, heating bitumen mix reactor 1
4, and a mix storage device 16. These four sub-plants are spaced apart on the ground 18 and are connected to a series of material conveyors 20a, 20b.
and 20c are connected in a line. Subplants 10 and 12 can be used to process a variety of materials and produce milled materials of various types and grades, while devices 14 and 16 are removable from devices 10 and 12 and are used for dispensing and loading. It is an accessory to the devices 10 and 12 in the sense that it does not preclude its use in combination with a pugmill for other purposes.

The apparatus 10 consists of a plurality of aggregate storage bins 22. These bins 22 are mounted on one or more frameworks 24 and each has an outlet feeder 2 on its underside for feeding material onto one or more lateral conveyors 28.
6. These conveyors 28 are adapted to transport materials towards conveyor 20a,
Various ratios of aggregate mixes can be prepared on conveyor 20a. The apparatus 10 may also have storage tanks for other materials, such as silos and the like for filler, and tanks for bitumen and other liquid materials.

The plug mill 12 has an inlet opening 30 on its upper side and an outlet opening 32 on its lower side. The whole is mounted on a raised platform 34 with supporting legs so that a transport truck, such as the one shown at 35, can be driven below the mill and parked in the space 37, allowing the mixed material to be transferred onto the truck. ing.

A slide housing 13 with a feed hopper 13a is provided on the underside of the platform.
The conveyor 20b is movable, and the hopper 1
3a, that is, a position to receive the milled material from the outlet opening 32, or the popper 13
It is also possible to move the conveyor to one side so that the material passing through the popper enters a track or the like.

The reactor 14 can be of any known construction with a conveyor 20b supplying raw material feed and binder and a conveyor 20c removing fresh mix from the appropriate point. The conveyor 20c is for distributing the heated mix into the upper intake ports 35a of one or more large thermal mix storage bins 36.
6 has a raised funnel-shaped feeder 38 for loading the thermal mix onto trucks for transporting it to the construction site.

The illustrated plant represents one major improvement over known thermal mix production plants in that the aggregate preparation stage of the plant can be separated and utilized for other aggregate processing functions. It must also be noted that the components of the plant can be constructed in such a way that they can be easily moved from one location to another.

One embodiment of a thermal mix reactor 14 according to the present invention is shown in FIGS. 2 and 3. For use in the method of the invention, a substantially stabilized mixture of aggregate and particulate binder is prepared by mixing selected proportions of the material in apparatus 10 with a bituminous binder in pack mill 12. Provide a homogeneous "cold mix" feed. If desired,
This cold mix may be taken out at the baggage mill 12 and piled up. Such a pile of cold mix can later be fed to the reactor as is or after further stabilization treatment.

An elongated hollow drum 5 forming part of the reactor 14
2 (The inside of the drum 52 defines the processing chamber 63.
The cold mix is conveyed by the conveyor 20b to the inlet port 44 (FIG. 2) of FIG. 3). The drum 52 is mounted on a raised platform 54 such that the axis of the drum is inclined at a small angle with respect to the horizontal.
4 is supported on the ground 18 by a plurality of support columns 56 installed at intervals, as shown.
Of course, the drum can also be supported for transport. The drum can be of conventional construction with two spaced annular tracks 58, 58a. These tracks support the drums on respective roller set trunnions 60, 60a mounted on platform 54. The drum is rotatable about its longitudinal axis by a motor and differential connected to roller set 60. A typical example of such a device is shown at 62 in FIG. Protrusions and lifting devices are provided inside the drum to allow tumbling of the drum contents as the drum rotates. The inlet 44 communicates with the interior of the drum 52 by means of a flow pressure operated valve tongue and an annular labyrinth seal which renders the inlet substantially airtight. The drum can be thermally insulated if desired or deemed necessary.

Parameters such as drum inclination and rotational speed as well as internal construction details of the drum determine the residence time of the material within the drum.
These parameters are set according to the desired specifications for the product. For transport, a drum of standard structure is used, the inclination angle is adjusted and set according to the type of work, and fine adjustments are made by adjusting the rotation speed.

A cylindrical housing 66 is fixed to the platform 54 and constitutes a front combustion chamber. The combustion chamber extends from the raised end of the drum and is a generally conical chamber with its wide end opening into the interior of the drum. drum 52
is rotatably engaged to the housing 66 in a substantially air-tight manner due to the labyrinth seal.

Housing 66 is between the drum and liquid fuel atomizing burner 68. Burner 68 can be a mechanically atomizing burner manufactured by Weishaupt et al., for example. burner 68
Although not shown in Figure 2, block 1 is shown in Figure 3.
It has one or more air introduction dampers which are both controlled by a motor indicated at 12. Their air tambours and fuel supply valves are controlled to provide balanced fuel conditions.

The combined length of the fuel chamber axes of burner 68 and chamber 66 is selected such that when heat production is maximum, i.e., when the burner is fully opened, combustion is completed at the forward end of chamber 66 adjacent intake 44. do.

The lower end of the drum 52 is open and a labyrinth seal provides a manifold or expansion box 80.
It communicates with the inside of. Box 80 terminates at its lower end to form an outlet 81 for the heated bitumen-containing mix produced within the drum. The heated mix flows downwardly from the drum and passes through a substantially air-tight controlled droplet 83 onto the conveyor 2.
0c (Figure 1).

A conduit 84 extends horizontally from the expansion box 80 and connects the interior of the box with a vertical exhaust chimney 86.
It communicates with There is an exhaust fan 88 inside the exhaust chimney, which is driven by an external motor 90. This motor and exhaust fan are
The volumetric rate of degassing is set to be constant.
Conduit 84 is provided with a bleed 92 that is controlled by a damper. Bleed 92 is adjustable by modulation motor 132 (FIG. 3) to vary the rate of fan exhaust flow exiting drum 52.

The feed introduced from the droplet 44 may be solely loose aggregate mix, but in a preferred method, the feed is premixed with a bituminous binder prior to introduction of the raw material consisting of aggregate mix into the processing chamber. It is usually formed by stabilization and homogenization. The previously used bitium-containing mix can also be recycled by incorporating it into the premixed feed. The feed supplied to the rotating drum descends in the drum, but is tumbled by being split, lifted and dropped by the action of projections and lifting members in the drum. Combustion chamber 66
The heated gas stream from the feed, which may contain some unburned air and combustion products, must be sufficiently hot to evaporate the moisture in the feed and at the same time cause physical interaction between particles and liquefied bitumen. The raw material feed is converted into a heated bitumen-containing mix by coating all particles with binder to a uniform thickness by direct contact.

The monitoring and control system for the reactor system will be explained in detail with reference to FIG. There are three monitoring points. The first is a first thermocouple 100 located in conduit 84 upstream of both bleed 92 and fan 88, which is sensitive to the temperature of the gas exiting from inside the drum. The second is a second thermocouple 102 located near the mix removal port 83 to measure the temperature of the product mix. The third is a pressure sensor 104 that spans the interior and exterior of the drum and monitors the difference between the total gas pressure inside the drum and the pressure outside. The sensor 104 is provided at the boundary between the combustion chamber 66 and the processing chamber 63.

Sensors 100 and 102 connect motor 112 which modulates burner fuel and air intake.
is coupled to a first control circuit for setting the modulation of. The variable values measured by the sensor 102 are sent to a readout device 114 and to a controller 116 where the desired value of the variable in question is set. Controller 11
The six control output pairs 116a, 116b and the control output 118a of the controller 118 coupled to the thermocouple 100 reach a switch relay 120. The thermocouple 100 has a visual indicator 124
The reading is also sent to the peak temperature shut-off alarm 126. At start-up, since it takes some time for the product to come out to the outlet 83, the motor 112 operates depending on the approximate value manually set on the panel automatic manual control 122 or the equivalent field control 124. or depending on the output of the controller 118 preset to meet the approximate requirements. When a measurable amount of product appears at port 83, the signal at output 116a switches relay 120, and from then on the control signal from output 116b depends on the comparison of the measured product temperature with the preset value. will be transmitted. That is, when the temperature of the product falls below a certain preset lower limit, the fuel and air supply is increased to increase combustion, and if the temperature reading exceeds the preset limit, it is recorded. If this happens, fuel and air intake are reduced.

Pressure sensor 104 is connected to damper motor 132
The monitoring point of a second independent control circuit 130 coupled to is the pressure sensor 104 . sensor 10
4 is a converter 134 that converts the pressure response into an electrical signal.
The electric signal is sent to the controller 136. The result of comparing the recorded pressure value with the preset value is used to adjust the damper 92 by the motor 132. automatic manual control 138
is provided for the purpose of setting at the start of operation and for emergency control. The pressure within the drum is controlled by the controller 136.
is lower than the given lower limit set by
The bleed damper 92 opens to increase its contribution to the constant exhaust mixture, thereby reducing the flow rate from the drum. In the opposite case, the excessively high internal drum pressure is restored by reducing the flow rate at the bleed.

The two variables monitored, product temperature and drum pressure, determine the desired key properties of the product,
It will reflect desired values for, for example, temperature, moisture content, ingredient ratios, and production rates.
Accordingly, in accordance with a preferred implementation of the invention, limits for these two variables are determined based on the desired limits for all variables of the product and those limits are sent to controllers 116 and 136. It seems possible to control the entire process by setting each. Generally, the aim is to achieve complete combustion in the burner,
and the temperature of the gas stream is maintained below the stoichiometric value of the burner system to a level that liquefies the binder but does not burn or fractionate the binder, thereby allowing gaseous state sintering to occur regardless of the rate of oxygen combustion by the burner. The removal rate (volume rate) should be sufficient to remove product and unburned gases and water vapor to the extent necessary to reduce the moisture content in the thermal mix product to a predetermined level, and there should be no binder inside the drum. The reactor is controlled to maintain a neutral atmosphere. The controlled presence of a neutral atmosphere for the binder has the effect of aiding the reaction process and reducing bitumen burning or fractionation. Sufficient cooling air is introduced to maintain the temperature within the drum at the level desired for liquefaction of the bitumen, yet to keep losses of bitumen due to oxidation or otherwise within acceptable limits. However, in order to minimize combustion of the bitumen and to minimize noise levels, the presence of excess air in the drum and the introduction of excessive volumes of cooling air flow should be avoided. It is also advantageous to have a slightly negative atmosphere within the drum to reduce leakage.

By heating the raw material with a heated gas stream in the drum and avoiding direct contact with the flame, it is possible to introduce the raw material as a homogenized and stabilized mix. As a result, the rate of production of fines can be reduced to a much lower level than the high levels unavoidable with conventional techniques in which dry aggregate mixes are tumbled and heated in contact with a flame, and yet oxidation and losses carried away by the exhaust stream can be maintained at low levels.

Of course, the invention is not limited to the production of heated bityumen-containing mixes. For example, the reactor of the present invention can be used to heat and dry aggregate mix alone, removing the unbound mix, which can then be combined with the binder in a batch process. In this case as well, by using the principles of the present invention, many of the benefits described above can be enjoyed.

[Brief explanation of the drawing]

FIG. 1 is a side view schematically showing the main components of a multi-purpose plant capable of producing heated bityumen-containing mixes; FIG. A side view of the vessel, and Figure 3 shows the second
1 is a block diagram of a monitoring and control circuit for the reactor shown in the figure; FIG. In these figures, 14 is the entire reactor of the present invention, 52 is a rotating drum defining a processing chamber 63,
44 is a raw material introduction port, 83 is a heated mix extraction port, 68 is a burner, 66 is a combustion chamber, 84 is a gas exhaust duct, 86 is a chimney, 100
and 102 are thermocouples, 118 and 1
16 is a controller, 118a, 116a and 116
b is the control output, 120 is clay, 112 and 1
32 is a motor, 104 is a pressure sensor, 136
is a controller, 92 is a bleed damper, and 88 is an exhaust fan.

Claims (1)

[Scope of Claims] 1. A main body defining a closed processing chamber which can be rotated around a predetermined long axis and is provided to tumble the contents during rotation, and includes at least an aggregate mixture. one or more inlet ports for supplying raw materials to said processing chamber; a withdrawal port for removing heated mixes from said processing chamber; and for introducing air into said processing chamber at or near one end of said processing chamber. an inlet port for discharging gas from said processing chamber at or near the other end of said processing chamber; and means for producing a gas flow from said processing chamber to said gas evacuation port; a burner for heating the raw material within the processing chamber to a temperature sufficient to convert it into the heated mix of the specification; 1. A reactor comprising: means for monitoring one or more parameters indicative of: and means for controlling said gas flow through the processing chamber in response to said monitoring. 2. The reactor of claim 1, wherein the burner is positioned relative to the raw material introduction port such that the gas stream is heated before it contacts the raw material. 3. The reactor according to claim 2, wherein the burner is a burner that mechanically sprays liquid fuel. 4. The reactor according to claim 1, 2 or 3, wherein the gas flow control means comprises a flow rate (volume rate) control valve device provided attached to the gas discharge port. 5. An exhaust fan with a constant degassing rate is provided in an exhaust duct communicating with the gas exhaust port, and the valve device is configured to provide an adjustable exhaust air flow between the gas exhaust port and the fan in the exhaust duct. Claim 4 is equipped with a lead means.
Reactor described in section. 6. The monitoring means includes a device for measuring gas pressure within the processing chamber, and means for comparing the measured pressure within the processing chamber with a preset value and sending a control signal to the valve device in accordance with the comparison. A reactor according to claim 4 or 5 provided. 7. The gas flow control signal comprises a flow rate (volume rate) control valve device attached to the burner, the valve device being connected to a device for measuring the temperature of the mix taken out from the processing chamber, 4. The reactor of claim 3, wherein said burner air and fuel intake can be controlled in response to said temperature measurement. 8. Claim 1 further comprising means for mixing said raw materials and stabilizing and homogenizing them at least to a considerable extent before supplying said raw materials to said processing chamber.
8. The reactor according to any one of items 7 to 7. 9. Feeding a raw material containing an aggregate mix into a closed processing chamber, maintaining a gas flow through the processing chamber, and heating the raw material within the processing chamber to a temperature sufficient to convert the raw material into a heated mix of the desired specification. In a method for producing a heated aggregate mix in which the heated mix is tumbled while the heated mix is removed from the processing chamber, one or more of the processing chambers are A method comprising monitoring one or more parameters indicative of conditions at the location and controlling the gas flow through the processing chamber in response to this monitoring. 10. The method of claim 9, wherein the raw material is heated to convert it into a heated mix of desired specification by heating the gas stream before it contacts the raw material. 11. A method according to claim 9 or 10, characterized in that the raw materials are mixed to stabilize and homogenize them to at least a significant degree before being fed to the processing chamber. 12. The method according to any one of claims 9 to 11, wherein controlling the gas flow includes controlling the flow rate (volume rate) of exhaust gas from the processing chamber. 13 Regardless of the rate of oxygen combustion by the burner, the withdrawal rate (by volume 13. The method according to claim 12, wherein the flow rate (volume velocity) of the exhaust gas is controlled so that the exhaust gas flow rate (volume velocity) is maintained at a constant flow rate. 14. Claim 12 or 14, wherein exhaust gas is mixed with outside air, the mixture is taken out at a constant volumetric rate, and the flow rate (volume rate) of the exhaust gas is controlled by controlling the ratio of outside air in the mixture. The method described in item 13. 15. The method of claim 9, wherein said monitoring includes measuring gas pressure within said processing chamber, and wherein said gas flow control is effected by comparing the measured pressure within said processing chamber with a preset value. 16 The raw material supplied to the processing chamber contains a bitumen-based binder, and such raw material is heated while being tumbled to form a heated bitumen-containing mix in which the binder is adhesively coated on the aggregate particles. A method according to any one of claims 9 to 15. 17. Said heating is carried out by a fuel burner open to said processing chamber, said controlling step comprising controlling the air and fuel intake rate (volumetric rate) of said burner, and said monitoring comprising measuring the temperature of the withdrawn mix. , and controlling air and fuel intake in response to said temperature measurement.
The method described in section. 18 feeding material containing aggregate mix into a closed processing chamber, maintaining a flow of gas containing air longitudinally through said processing chamber, and converting said raw material into a heated mix of desired specification within said processing chamber; A method for producing a heated aggregate mix, in which the heated mix is tumbled while being heated to a temperature sufficient to cause the mixture to be heated to a temperature sufficient to A method characterized in that the raw material is heated by heating to convert it into a heated mix of the desired specification. 19. The method of claim 18, wherein the raw material is mixed to stabilize and homogenize it to at least a significant degree before it is supplied to the processing chamber. 20 The raw material supplied to the processing chamber contains a bitumen-based binder, and such raw material is heated while being tumbled to form a heated bitumen-containing mix in which the binder is adhesively coated on the aggregate particles. A method according to claim 18 or 19.