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PLC in asphalt emulsification equipment

PLC in asphalt emulsification equipment

The so-called emulsified asphalt is to melt the asphalt through the action of emulsifier and machinery. The asphalt is dispersed in a water solution containing a certain amount of emulsifier in the form of tiny droplets, forming an oil in water asphalt emulsion. The emulsion is liquid at room temperature. Modified emulsified asphalt is a modified asphalt mixture emulsion which has emulsified asphalt as the base material and bitumen modified material as the external modification material under certain technological process. After mixing, mixing and preparing, the modified asphalt mixture emulsion is called modified emulsified asphalt.




Current domestic technology status: before the founding of New China, only a few municipal engineering departments used a small amount of anionic emulsified asphalt, after liberation has not been exposed to this technology. Up to the late 1970s, in order to develop the application of this new technology in our country, the Ministry of Communications organized a collaborative group of "cationic emulsified asphalt and its road performance research" to tackle the key problems of this technology. The project was listed as a key scientific research project of the Ministry of Communications in 1981 and an energy-saving application project of the former National Planning Commission and the National Economic Commission in 1983. Now the National Highway Department has more than 500 sets of emulsified asphalt plants. The production technology of emulsified asphalt workshop has been improved continuously. The production of emulsified asphalt has gradually developed from open flow, experience control of oil-water ratio to sealed pressure control of oil-water ratio by flowmeter and then to computer automatic control of oil-water ratio and oil-water temperature. The production quality of emulsified asphalt and the increase of output have met the needs of highway engineering and maintenance engineering. With the development of emulsified asphalt technology and its extensive application in China, higher requirements for the quality and output of asphalt emulsion have been put forward. Asphalt emulsification equipment will change the current situation of varieties confusion, high failure rate and small output, and develop towards standardization and rationalization.

Fig. 1. Emulsified asphalt production equipment abroad

The emulsified asphalt equipment can be divided into three types: batch operation, semi-continuous operation and continuous operation. The batch modified emulsified asphalt production equipment mixes emulsifier, acid, water, and latex modifier in the soap mixing tank, and then pumps them into the colloid mill. Once a bottle of soap liquid is used up, then the soap solution is placed, and then the next tank can be produced. When used in the production of modified emulsified asphalt, according to the different modification process, latex pipeline can be connected to the colloid mill before or after the colloid mill, or there is no special latex pipeline, but manually add the prescribed amount of latex to the soap tank.




Semi-continuous emulsified asphalt production equipment, in fact, the intermittent emulsified asphalt equipment is more equipped with soap mixing tank, so that can alternately mix soap, to ensure that the soap into the colloid mill uninterrupted. At present, a large number of emulsified asphalt production equipment in China belongs to this type. Continuous emulsified asphalt production equipment, the emulsifier, water, acid, latex modifier, asphalt and other directly pumped into the colloid mill with metering pump. The mixing of soap liquid is carried out in the conveying pipeline.

Fig. 2. Advanced emulsified asphalt production equipment in China

The existing asphalt emulsifying equipment mainly relies on manual operation, and consists of several pumps and several material tanks containing asphalt, emulsifiers and finished asphalt emulsifying products. Material proportion is mainly added by manual allocation through operator's experience. The characteristics of simple control technology, extremely unstable product quality and low production efficiency have always troubled our country's highway builders and highway maintenance personnel, but also greatly increased the intensity of people's labor.




After Market Research and in-depth discussion with highway maintenance staff, we decided to design a new set of equipment with high degree of automation and significantly improved production efficiency while reducing the labor intensity of staff.




The following is a production process in the emulsified asphalt production process. We have adopted this production process, coupled with programmable logic controller, frequency converter, flowmeter, quantitative pump and other computer technology control units, to a very large extent, improved the existing production conditions and improved the quality of products.

Fig. 3. A commonly used emulsified asphalt production process.

The whole equipment is made up of over asphalt tank, emulsion mixing tank, finished product tank, speed regulating emulsion pump, shearing mill, finished product delivery pump, electric control cabinet, large floor pipeline and valve.




Features of the equipment: mainly to solve the problem of oil-water ratio, it uses two speed-regulating quantitative pumps, according to the oil-water ratio, adjust the speed of the quantitative pump to meet the proportion requirements, operation is both intuitive and convenient, oil and water through the two pumps into the emulsifier for emulsification.




The electronic control part takes the UN 200 series 224 PLC of Shenzhen UniMAT Company as the control core. The PLC has the characteristics of high control precision, sensitive response and excellent seismic performance. It has been widely used in road construction industry. It is composed of frequency converter, flowmeter, quantitative pump and all kinds of temperature, touch screen and pressure control equipment.




The remarkable feature of this system is that PLC control system with stable and reliable response and prompt response is introduced. At the same time, it is equipped with advanced control equipment such as frequency converter, touch screen and flowmeter, so as to ensure the fast and stable operation of the system.




As we all know, highway construction and highway maintenance are mostly outdoors, the environment is unparalleled by other industries, not only to withstand the wind and sunshine, but also to withstand the high temperature and cold, at the same time, most of the road construction equipment is mobile, and the vibration is very serious, therefore, we in the selection of components on the past. Considered, the year before last we made a road maintenance asphalt paver, its control system is the use of the company's 224 series PLC (DC24V power supply), the biggest feature of this equipment is installed in a car, all day with the car running around, tremors, but after more than a year of use The PLC has stood the test and is still working conscientiously. Therefore, in the asphalt emulsification equipment, we also selected the 224 series PLC of UniMAT company.




The 224 CPU has two communication ports, one is connected with touch screen, the other is used for program debugging. The two communication ports do not interfere with each other, which brings great convenience to debugging. It can not only control the equipment by touch screen, monitor the operation of the equipment, but also carry out PLC by STEP 7 MicroWIN SP9 programming software. Monitoring greatly facilitated the debugging of the equipment and improved the work efficiency.




The PLC control system adopts the UN 200 series 224 (order number is UN 214-1BD23-0XB0) CPU of Shenzhen UniMAT Company, with 4-channel analog expansion input module (order number is UN 231-0HC22-0XA0), 2-channel analog expansion output module (order number is UN 232-0HB22-0XA0) and necessary digital output input module. After debugging and using, the whole system shows excellent performance of sensitive response, high control precision and high production efficiency.




The control system of asphalt emulsification equipment is shown below.




The working principle of the whole equipment is not complicated, the key is the mixture control of asphalt and emulsifier, which is related to the quality of the product and the production efficiency, is the key to the control system, it needs to adjust the rotational speed of each material pump, and needs to timely and accurately handle the flow back from the scene. Pressure and temperature signals, according to the analog signal processed to further adjust the speed of each material pump, forming a fast and accurate closed-loop control.




This control system is equipped with touch-screen as the upper computer to facilitate users to modify parameters and hand automatic control. In order to realize the mixing ratio of asphalt and emulsifier, the system controls the asphalt pump and emulsifier pump by frequency conversion, and then carries on the closed-loop control through the data feedback from the flowmeter.

                           Figure 6, part of the program screenshots

Firstly, the output of finished product and the mixing ratio of asphalt emulsifier are set by touch screen. The operating frequency of the two pumps is transmitted to the speed of the converter of the two pumps by the two-channel analog output module (the order number is UN 232-0HB22-0XA0) with the analog signal of 4-20mA, and the output frequency of the two converters is 4-20mA. The signal is also fed back to the PLC's four-channel analog expansion input module (order number UN 231-0HC22-0XA0), which is displayed on the touch screen after calculation.




In order to facilitate users to monitor whether the system works correctly and to achieve closed-loop control, two flowmeters are installed in the pipeline. Both of them are connected to the PLC system by analog signals of 4-20 mA. The PLC adjusts the rotational speed of each quantitative pump according to the preset proportion of ingredients and production efficiency through the collected flow signals. To achieve stable product quality and reasonable arrangement of production planning purposes.




In order to facilitate the mixing of emulsifier and asphalt, the emulsifier tank is electrically heated with a power of 10KW. The temperature is collected by the temperature controller. At the same time, the alarm signal of the temperature controller is connected to the PLC control system. The temperature is monitored in real time to ensure the quality of the product to the greatest extent.




When the asphalt temperature in the raw asphalt tank is too high, the exhaust fan is stopped to reduce the air volume to reduce the temperature. When the temperature is lower than the working temperature, the exhaust fan is started. Because the user requests to control the temperature by the temperature controller, the alarm contact of the temperature controller is connected to the PLC system, and the final temperature is realized by the output of the PLC. Degree control.

Because asphalt is not only easy to solidify at room temperature, but also easy to plug the pipeline, the pipeline through which the asphalt flows is heated: the pipeline through which the asphalt flows is a double-decker pipeline (a thick tube is then welded, another tube is used at the corner to connect the outer pipeline), the inner laminar flow asphalt, the heat-resistant oil heated by the outer laminar flow, and the oil. At temperatures of about 200 degrees, an oil pump pumps the heated heat-resistant oil out of the small furnace of the bituminous tank of the raw material and then delivers it to all the outer layers of the asphalt pipeline. In order to avoid asphalt blocking the pipeline, on the one hand, it is necessary to heat the pipeline through heat-resistant oil before work, on the other hand, there are strict requirements for the start-up and stop sequence of each pump and shear mill.Figure 9, debugger debugging equipment

In order to facilitate debugging and use, the system set up manual and automatic mode, automatic control mode through PLC control, equipment in accordance with the pre-set operation mode.




Manual control when the user can start a pump alone, but the order of the pump start-stop requires the operator to operate strictly in accordance with the equipment production process, at this time, only the start-stop operation of the pump by the operator's own control, pump speed is still controlled by PLC settings parameters.




Equipment maintenance is not subject to any restrictions, in manual mode can be arbitrarily started and stopped each device (running without material).




Under normal conditions, the equipment runs in automatic control mode, debugs or maintains the equipment and uses manual mode in emergency.




After debugging and more than a month's application, the equipment, with its stable and reliable quality, fast and sensitive control speed, improves the output of the products, ensures the qualified rate of the products, reduces the labor intensity of the field operators, and brings very good economic and social benefits to the users, and wins the praise of the users.

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