Method and device for energy recovery by manufacturing of asphalt in bulk

Method and device for manufacturing of asphalt bulk masses where a substantial part of the heat energy of the furnace gases from the drying and mixing process is transferred to the bulk mass fractions before those are supplied to the drying and mixing process and where the furnace gases by this process at the same time are cleaned for pollutions. Bulk masses are directed downwards between two parallelly arranged inclined planes (1, 5) where the lower inclined plane (1) comprising horizontally arranged downwards directed ribs (2) directing the furnace gases to the lower side of the bulk masses and where the second inclined plane (5) comprising vertically arranged ribs (4) suctioning the cleaned furnace gases up from the bulk masses after a substantial part of the heat energy being transferred to the bulk masses. At the lower and upper ends of the inclined planes accumulations of the bulk masses (7, 11) are maintained for preventing air from the atmosphere to penetrate into the system. The bulk mass fractions thereafter are transferred to the drying and mixing process, thereby having accumulated a substantial amount of heat energy and the bitumen components being transferred with the furnace gases, as well as other pollutions.

The invention is a method and a device for energy recovery during 
manufacture of asphalt in bulk. 
Today smoke gasses from the manufacturing of asphalt in bulk normally are 
cleaned by scrubbers or bag filters. Both systems have disadvantages which 
negatively influence the processes, both operationally and economically. 
In known scrubbers the pollutants of the gases are absorbed by a liquid, 
usually water. This process includes a high energy consumption and also is 
dependent on water supply. A high amount of condensation from the oil 
products creates problems with clogging of jets which in turn causes 
disturbances in the system. In addition, sulphur deposits also create 
difficulties. For these reasons, use of scrubbers demands a considerable 
amount of energy and maintenance work. 
Bag filters, on the other hand, have a considerable limitation in that the 
cloth is destroyed at temperatures exceeding about 230.degree. C. 
Furthermore the compositions of bitumen will condense and pack the clock 
in the bag filters. 
By means of the features mentioned in the characterizing clause of the 
claims, these unfortunate results of the prior art are overcome. In 
addition, a considerable energy recovery is achieved in that the heat 
energy of the smoke gases is used for preheating the bulk before it is 
supplied to the drying and mixing process.

FIG. 1 discloses a total plant for manufacturing asphalt in bulk according 
to the invention. Two bulk fractions are supplied through feeding pockets 
24, whereas filler is supplied from a silo 25 to a conveyor 28 which 
transports the bulk to the device according to the invention. The drawing 
discloses also bitumen tanks 22, an oil tank 23, doser device 27 for 
recirculation and a conveyor 26 for withdrawal of the end product. 
The waste gases from the mixing drum 29 are directed by channels 30 to the 
device 21. After treatment in the device, the bulk is transported by a 
transport means 31 to the input of the mixing drum 29. 
The device 21 is disclosed in vertical section on FIG. 2. The conveyor 28 
transports the bulk to the elongated funnel 6 where the bulk is 
distributed equally along the length of the funnel by a scraper conveyor 
8. In the lowest part of the funnel 6 a packing of bulk, generally denoted 
11, is created. This packing or plug prevents air in the environment from 
penetrating into the device 21. A cam 12 divides the bulk in the funnel 
into branches for treatment in symmetrically arranged sets of inclined 
planes. 
Each inclined plane comprises a lower inclined wall 1 and an upper inclined 
wall plan 5 being arranged in parallel and at a distance from each other. 
In one embodiment, the free distance between the walls is 200 mm and the 
sloping angle is 14.degree. to the vertical. Each inclined wall 1, 5 
comprises a grating 3, 13 to which horizontally fixed ribs 2, 4 are 
arranged. The ribs 2 in the first wall 1 are arranged sloping downwards 
against the second wall 5, the ribs thereby partly overlapping each other. 
The ribs 4 in the wall inclined plane 5 are arranged vertically. 
The combustion gasses supplied to the device from the mixing drum 29 by 
channels 30, are supplied to the lower side of the first inclined wall 1 
and pressed through the ribs 2 against the bulk masses sliding down the 
inclined plane from the funnel 6. The gasses disperse a substantial part 
of their heat energy to the bulk masses and simultaneously are cleaned of 
pollutants. The gasses are then sucked up through the ribs 4 in the second 
inclined wall 5 and further directed to the environment. 
To cause the bulk masses to move downwards between the inclined walls, 
vibrator devices 14 are used to vibrate the inclined planes. Further, to 
prevent the bulk masses from packing or compressing, the lower edge of the 
ribs 2 are provided with teeth comprising alternating recesses and webs, 
the webs in a rib being arranged above the recesses in the rib beneath. 
The bulk masses are thereby disengaged as they fall from rib to rib. 
A conveyor is arranged at the bottom of the inclined planes for 
transportation of the bulk masses which have been treated. The conveyor is 
permanently set to maintain a packing or plug 7 with bulk masses, 
preventing air from penetrating into the system from the environment. 
By means of the device according to the invention, a remarkable amount of 
energy is recovered as a substantial part of the energy in the furnace 
gases is transferred to the bulk masses, whereas at the same time, 
additional energy consumption for cleaning the gases is avoided. 
Additional bitumen substances transferred by the furnace gases are 
deposited in the bulk masses and recycled back to the process.