Improvement of the fuel supply system for the TAP3000LB asphalt mixing plant

During the operation of the Tanaka TAP3000LB asphalt mixing plant, problems such as difficult ignition, incomplete combustion, aggregate temperature not meeting construction requirements, and automatic flameout occurred, which seriously affected the project progress. After inspection and analysis, it was found that the fuel supply pressure of the burner in the asphalt mixing plant was insufficient. The original design pressure was 3.2 MPa, but the actual working pressure was less than 1.5 MPa, and the flow supply also failed to meet the design requirements. The reason for the above phenomenon is that the fuel supply pump (twin-screw pump) has been in use for a relatively long time, and the screws are severely worn, resulting in significant internal leakage and causing the fuel supply pressure and flow rate to fail to meet the working requirements. If the original twin-screw pump is purchased from Japan, it will be very expensive (costing 120,000 RMB), and the delivery time will be as long as more than two months, which will seriously affect the normal operation of the asphalt mixing plant. For this reason, it was decided to make necessary improvements to the fuel supply system.

1. Improvement plan

The main technical parameters of the fuel supply system of the burner in this asphalt mixing plant: The rotational speed of the driving shaft of the supply pump is 2,900 r/min; Supply pump displacement

It is 34.5 mL/r; The rated output pressure of the supply pump is 3.5 MPa. The safety valve of the fuel supply system has a rated pressure of 3.2 MPa and a maximum unloading capacity of 50 L/min. The supply pump requires the quality of the fuel being conveyed to be relatively high, and there is a 100-mesh fine filter before the pump.

Based on the various parameter indicators of the above-mentioned fuel supply system, two selection schemes have been set:

The first is to adopt a twin-screw pump. When screening the parameters of various types of screw pumps, it was found that domestic twin-screw pumps have the following problems: the pressure fails to meet the requirements of the fuel supply system, and the price is relatively high; Screw pumps have relatively high requirements for the quality of the oil being conveyed. Therefore, twin-screw pumps are not suitable for use.

The second is to adopt a gear pump. Gear pumps have the following advantages: The pressure can meet the requirements of the system; The requirements for the quality of the oil being conveyed are relatively low. There are numerous domestic manufacturers, making it easy to choose. The price is low and the usage cost is low.

Taking various factors into comprehensive consideration, it was finally decided to select the CB-L-100 gear pump, with an output pressure of 15 MPa. The displacement is 70 mL/r; The rated speed is 1,500 r/min. The motor selected is a 7.5kW three-phase asynchronous motor with a rotational speed of 1450r/min. The connection type of the pump's inlet and outlet is flange connection, and the connection between the pump and the motor adopts a cross coupling. The electrical system of the original supply pump was inspected and it was found that the original electrical circuit could meet the usage requirements of the current motor, so no adjustment is needed for the electrical system.

2 Installation and commissioning

Due to the different structure and geometric dimensions of the selected CB-L-100 gear pump from the original twin-screw pump, it cannot be installed at the original position of the burner. Therefore, a base mounting plate needs to be processed to meet the installation requirements of the gear pump. Meanwhile, in order to facilitate processing, the oil supply pipeline was improved. The oil inlet of the pump is made of seamless steel pipe with a diameter of 50mm and is connected to the original oil supply pipeline through a flange. Move the position of the pump from its original narrow space to a larger space beside the burner. To reduce the impact of the gear pump's vibration on the burner, the pump's outlet is connected to the crude oil pipe of the burner through a flange with a Φ 35mm high-pressure hose. The driving shaft of the gear pump is connected to the motor with a cross coupling, which greatly reduces the processing accuracy requirements of the base and simultaneously increases the service life of the gear pump. The motor was changed from the original three-phase asynchronous motor with a speed of 2,900 r/min to a three-phase asynchronous motor with a speed of 1,450 r/min. The original pump input end can now use a 60-mesh filter with a lower price, and the range of fuel oils has been greatly expanded, reducing the construction cost. After the improvement, the original circuit, oil gauge, pressure gauge and safety valve and other components were retained. The improved practical application has proved that the burner can meet the construction requirements. The output of asphalt concrete has reached the designed output - 240 t/h, the temperature error is controlled within ±5 ℃, and the application range of fuel oil has been greatly expanded. At this point, the improvement of the fuel supply system has been completed, with a total improvement cost of approximately 6,000 yuan.

Practical experience has shown that by adopting the improved fuel supply system, a wider range of fuel can be used, which enhances work efficiency, reduces the failure rate, lowers energy consumption and saves funds. It is particularly worth noting that due to the significant reduction in fuel quality requirements for gear pumps, low-quality fuel can be used. The price of each ton of fuel has dropped by at least 460 yuan. Assuming that an asphalt mixing plant typically uses 2,000 tons of fuel per year, the fuel alone can save 920,000 yuan in a year, reducing costs by 15%, and the economic benefits are remarkable. (Zhang Xiang, Zhang Qin