RU2534800C1 - Bitumen foaming device - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: device includes a mixer, bitumen and foaming liquid supply systems, which are equipped with shutoff valves and a dispersing device. The foaming liquid supply system forms a circular contour; the dispersing device is made in the form of an abrasive porous element connected to the foaming liquid supply system, and shutoff valves of the system are made in the form of two check valves.

EFFECT: invention ensures obtainment of homogeneous fine foam that allows achieving a high homogeneity degree of a mixture during mixing, prevention of blockage of a porous element, and a possibility of dosing small amounts of a foaming liquid.

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Description

The invention is intended for use in road construction in the production of asphalt mixtures and paving device.

A device for foaming bitumen in the form of a centrifugal nozzle, which is a cylindrical heat-insulated body, loading device, piping, sprayer. In the internal volume of the housing is a device for heating bitumen. Separately, there is a device for heating water, which is connected by pipelines to the body and spray. The sprayer is equipped with a hollow conical nozzle with spiral swirls made on the inner surface [RF Patent No. 2461417, 11/10/2010].

It is also known a device for preparing technical foam in the form of a screw nozzle, which is a dispersion chamber in the form of a truncated cone with a rotating screw located inside. A mixing chamber is attached to the dispersion chamber, to which nozzles with compressed air and a foaming solution are supplied. A nozzle for discharging the finished foam is supplied to the dispersion chamber, at the base of which a retaining grid is installed. [RF patent No. 2461458, 06/09/2011]. Despite the fact that foam concrete mixing plants are claimed to be the device’s area of operation, the device can also be used to produce bitumen foam.

The above devices are related to the jet type of devices for producing bitumen foam. Similar devices have certain disadvantages. To reach certain quality indicators of the obtained bitumen foam, such devices require some time (transitional mode with the release of a substandard product). Hence, in plants with an intermittent supply of bitumen foam, such devices are ineffective.

Also known is a device for producing bubble-type foam, which is a container filled with bitumen and equipped with a bitumen conduit in the lower part, as well as a foam conduit in the upper part. Inside the tank is a dispersant consisting of a spray gun and a mesh. [Pershin M.N. Barinov E.N. Korenovsky G.V. "Foamed bitumen in road construction." - M .: Transport, 1989, 80 pp.]. A foaming agent is fed into the lower part of the container under pressure through a spray gun, as a result of which a dynamic two-phase layer of gas and bitumen appears. Foam forms on the surface, which is diverted outward along the foam line. To increase the uniformity and dispersion of bitumen foam, a mesh is installed inside the tank.

The main disadvantages of the analog device should include the difficulty of dispensing a small amount of blowing agent, the inability to obtain a limited amount of foam.

As a prototype, a device for preparing foamed bitumen based on a car pneumatic system was selected. [Technological support for the quality of construction, guidelines, 2004, SIBADI]. The device comprises a bitumen tank, a distribution pipe, a hydrodynamic mixer, a bitumen pump, a water flow meter, a check valve, a water tank, and a pressure valve.

From the bitumen tank, through the pump, bitumen enters the hydrodynamic mixer. Water is dosed from the water tank using a water flow meter into the same hydrodynamic mixer under pressure, which is pumped into the tank by the vehicle’s pneumatic system. Foam is formed in the mixer, which is discharged into the distribution pipe.

However, such a device has some disadvantages. Constant monitoring of the blowing agent consumption is required and the dosage of small amounts of blowing agent becomes problematic. In addition, stopping the device will eventually lead to clogging of the mixing chamber and supply channels.

The objective of the invention is to provide a simple and reliable device for producing bitumen foam with a strict dosing system of foam and foaming agent, with the possibility of obtaining a limited amount of foam without transient conditions.

The solution to this problem is achieved by the device inside the mixer finely porous cylinder connected to a foaming fluid supply system circulating in a closed circuit.

The proposed device foaming bitumen (figure 1) consists of a mixer 1 containing nozzles input 2 and output 3 of bitumen. Inside the mixer body the dispersing device 4 is fixedly mounted, made in the form of a cylindrical porous element. As a dispersing device can be used abrasive tool of the appropriate form, used for peeling metal products. The dispersing device is connected to the foaming fluid (water) supply system through nozzles 5, 6. The foaming fluid supply system forms a circular circuit including a tank 7, pump 8 and check valves 9, 10.

When the device is in operation, bitumen is fed into the mixer body through the pipe 2 at a given pressure and operating temperature. The foaming liquid from the tank 7 by the pump 8 through the check valve 9 enters the dispersing device 4 under a pressure exceeding the pressure of bitumen and providing the necessary fluid flow through the wall of the porous cylinder. Seeping through the porous wall, the liquid is disrupted by the flow of bitumen, evaporates and disperses in it with the formation of foam, which is discharged through the pipe 3.

Non-return valves 9 and 10 during operation of the device make it possible to provide the necessary pressure drop for forcing through a porous wall a strictly normalized amount of foaming liquid. When the device stops, the non-return valves close, ensuring that the liquid in the main volume between the valves 9 and 10 is filled. The liquid cut off in this volume prevents bitumen from seeping into the pores of the dispersant and eliminates its clogging. The proposed device will provide the following benefits.

1. The use of a porous element as a dispersant makes it possible to obtain a homogeneous finely dispersed foam, which during mixing allows to achieve a high degree of homogeneity of the mixture.

2. The use of a flowing foaming fluid supply scheme allows to solve the problem of dispensing small amounts of foaming fluid. Its flow rate is determined by the throughput of the porous element at a given pressure difference in the fluid and bitumen supply systems.

3. The use of check valves in the foaming fluid supply system prevents clogging of the pores of the cylinder from its outer surface while the device is stopped. This is achieved due to the fact that when the unit is turned off, the volume of the line between the check valves remains filled with liquid under pressure determined by the stiffness of the spring in the valve. The pressure in the mixer is equal to atmospheric. Under these conditions, even after the cessation of bitumen supply, the foaming liquid seeps through the porous element and the pores are cleaned on its outer surface.

The bitumen foam obtained in the described device has the following characteristics: a multiplicity of 20-25, a dispersion of (0.3-0.5) 10 ^-3 m and stability (time of destruction of half a column of foam) is 60-90 seconds.

Claims (1)

A bitumen foaming device comprising a mixer, bitumen and foaming liquid supply systems equipped with shutoff valves and a dispersing device, characterized in that the foaming liquid supply system forms a circular contour, the dispersing device is made in the form of an abrasive porous element connected to the foaming liquid supply system , and the shutoff valves of the system are made in the form of two check valves.

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