Guangdong Shenxing Chemical Co., Ltd. has a formaldehyde production capacity of 100,000 tons/year and formaldehyde downstream products U-50, U-57, U-65 urea-formaldehyde rubber production capacity of 70,000 tons/year, a large-scale formaldehyde and Urea-formaldehyde rubber production company, the company's urea-formaldehyde plastic reactor formaldehyde metering used once more expensive mass flowmeter produced by the United States Micro Motion company, the flowmeter installed soon appears measurement error is too large, it is difficult to repair many times Meet the measurement accuracy requirements. Because the flowmeter has certain restrictions on the use environment and medium, the requirements on the use and maintenance technology are relatively high, and the other parts are difficult to purchase, the measurement of the urea-formaldehyde rubber reactor's formaldehyde ingredient has not been well resolved. The control of product quality brings certain difficulties. The company has two 20 m3, 1 15 m3 urea-formaldehyde rubber reactors, how to invest in less, but also to achieve accurate measurement of 3 formaldehyde urea-formaldehyde rubber reactor ingredients, is a very important subject. In response to this problem, we have envisaged 3 scenarios:
1. A container is placed on an electronic weighing scale using an electronic scale. Formaldehyde is pumped into a container and weighed before flowing from the bottom of the container to the reactor. This is a traditional measurement method. Manufacturers use this method. The advantages are: intuitive, to meet the general accuracy requirements. The inadequacies are: one-time capital investment is relatively large, if the use of stainless steel container capital investment will be greater; feeding rate is slow, if you use 28 m3 / h of formaldehyde pumping 13 tons of formaldehyde into the container takes 27 minutes, after manual weighing Afterwards it takes about 30 minutes to flow into the reaction vessel. It takes about 1 hour. Obviously, the efficiency is low. The strain sensor of the ground scale is relatively large with temperature change, and the repeatability is poor. Each time when weighing is over, the manual sensor is used to overcome the sensor band. From the management of the residual value of worse; ground scale is not continuous online measurement.
2. Use RT automatic value control system This is a better automatic control measurement program, measurement accuracy is less than 0.5%, if there is temperature compensation, measurement accuracy will be higher, but also can reduce the labor intensity of workers. What he lacks is: one-time capital investment is large and maintenance is large.
3. With RT intelligent temperature compensated pipeline flow meter This is a more advanced high-precision temperature compensation flow meter, he has the following characteristics:
â—Small pressure loss and fast flow rate. If using 28 m3/h formaldehyde to pump 13 tons of formaldehyde into the reaction kettle, it takes only 27 minutes to complete the entire process of formaldehyde batching. â— Built-in lithium battery, no external power supply, easy installation, and anti-interference ability Strong;
â— Advanced technology, the core components of the United States using micro-computer chips, stable and reliable operation, maintenance-free;
â— Celsius temperature, instantaneous flow, cumulative flow can be displayed dynamically;
◠High precision:±0.2～0.5%, with temperature compensation function, no worry about measurement error caused by temperature change, temperature compensation range: -40°C～+100°C;
â— Easy to maintain, small and lightweight, simple structure, can be disassembled in a short time, the internal cleaning is simple â— The price is reasonable, the same caliber is half cheaper than oval gear mechanical flowmeter;
After repeated comparisons of the advantages and disadvantages of the above three programs, we believe that the RT temperature-compensated pipe flowmeter developed by Jiangsu is more suitable.
1 Selection of flow range and temperature range The company's existing formaldehyde pump has a flow rate of 65 m3/h, a lift of 20 m, a flow of 65 mm, an existing pipeline of 50 mm, and a formaldehyde temperature of between 20°C and 50°C. The distance between urea-formaldehyde rubber reactors is relatively long (about 100 meters) and the kinetic energy consumption is large. Actually, when formaldehyde flows into the reactor, it is about 30 m3/h. According to "Formaldehyde and Methanol", 2004, Phase 6, 28-30, 2004 Formaldehyde industry will report the relevant content of 128-130 pages), pass through the 50mmDZK-J intelligent temperature compensation flowmeter best, its normal flow range: 4 ~ 40 m3 / h, pressure: 2.5Mpa,
Temperature compensation range: -40°C to +100°C, accuracy: up to 0.2% after temperature compensation.
2 Installation and Commissioning
2.1 Piping connection First remove the original Micro Motion mass flow meter and pneumatic diaphragm control valve from the pipe, and then follow the installation requirements of the DZK-J intelligent temperature compensation flowmeter manual provided by Shenzhen Boret Technology Co., Ltd. The temperature compensation flowmeter is directly installed at the inlet manifolds of formaldehyde reactors in the three reactors. A 50mm stainless steel filter is added on the basis of the original horizontal pipeline, strictly in accordance with the 10 times straight pipe section and 5 times straight pipe section. Requirements
2.2 commissioning and commissioning According to the quality of measurement, the density of formaldehyde shall be stored in the flowmeter. If no density is set, it shall be measured in volumetric terms. The reactor was calibrated with a ruler as a standard reference container.
1 Turn the counterclockwise to open the front cover of the RT smart temperature compensation meter header, and input the formaldehyde density and temperature expansion coefficient separately (operate according to the relevant section of the manual). The meter is automatically stored in the microcomputer chip and stored forever. Tighten the front cover clockwise.
2 Input 12 tons of formaldehyde into the reactor, first press the cumulative amount of the flow meter to clear the button, open the No. 1 reactor valve, close the No. 2 and No. 3 reactor valve, start the formaldehyde pump, open the valve before the flowmeter (see Fig. 2) The flowmeter enters the metering state. When the flowmeter's cumulative flow rate approaches 12 tons, the front valve of the flowmeter is closed at 20KG in advance, and the flowmeter's cumulative flow rate is read. The formaldehyde input of the reactor is measured with a ruler rod and calculated by the following formula:
Relative error = [flow meter cumulative flow (tons) - reactor input formaldehyde (tons)] / reactor reactor input (tons) * 100%, the actual error is 0.18%.
When the error between the actual flow rate and the standard volume is large, the following correction can be used:
Actual traffic
L correction = L setting × standard flow
L correction ------ new flow coefficient meter
L set ------ meter old flow coefficient actual flow ------ [flow meter cumulative flow (tons)]
Standard flow ------ [reactor input (tons)]
During the measurement process, we observed that the instantaneous flow rate of the liquid crystal display of the flowmeter was about 31.2m3/h and the temperature was 42°C, which was within the normal operating range of the flowmeter. We carried out the actual verification according to the above method. The error was within the controllable range and reached the specified accuracy requirements. It met the requirements for the formaldehyde ingredient metering of our urea-formaldehyde rubber reactor.
The successful operation of the RT intelligent temperature compensation flowmeter in the measurement of formaldehyde in the urea-formaldehyde plastic reactor will reduce the one-time capital investment, reduce the cumbersome maintenance workload and maintenance costs, and achieve a small pressure loss, high accuracy, and flow rate Fast, easy to operate, ideal effect, especially the flow meter has a temperature compensation function, which effectively solves the measurement inaccuracy caused by formaldehyde temperature changes. It is more beneficial that the production quality of our company's urea-formaldehyde rubber is effectively controlled. Improve the company's reputation,
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