The multi-share branch in the water-based coating production device accurately measures the pipe design

In the coatings industry, water-based coatings are in line with the mainstream of coating products to environmentally friendly direction of development, began to gradually replace the traditional solvent-based coatings. With the growing national demand for environmental protection and health, the market for water-based coatings is also developing rapidly. Water-based coating production belongs to the category of fine chemical industry, raw materials, additives, production brands, intermittent production, complex formulation is the main characteristics of its technology
China
. Dosing is often weighed in the laboratory, and ingredients need to be measured frequently in industrial plants. Whether it's acetone or process water as a solvent, or as a raw material, you'll encounter a flow meter to measure multiple target devices. How to achieve accurate measurement of multi-share branches is the difficulty of process pipe design.1 Process Introduction
a new water-based coating device in Ningbo uses puD and PA production processes, each with 3 production lines. PUD to polyols and water-based isocyanate as the main raw materials, according to the stage of the use of acetone and process water as a solvent, mainly divided into pre-polymerization, dispersion, post-expansion chain, de-acetone four steps. PA with acrylics as the main raw material, process water as a solvent, mainly divided into pre-emulsification, polymerization, after-treatment three steps.2 determines the common branch
to use the same flow meter to accurately measure different branches, the first thing to meet is that the measurement range can not be too different. From the point of view of giving priority to meeting this requirement, it should be classified by functional unit. Example: Pre-polymerized acetone to 3 PUD lines will be measured using the same flow meter, the measurement range is consistent to ensure a smaller range, accuracy is guaranteed. However, the scheme ignores the independence of each line, if the same equipment of the two lines need to feed at the same time, it will not be able to achieve, thus leaving a production hazard in the process. Therefore, it is necessary to divide according to each line, and then in-line according to the measurement range is not much different from the common flow meter. Although the number of flow meters has been increased, production needs have been met. From the pipe consideration, reduce the connection between different production lines, but also reduce the difficulty of pipe.3 Common flow meter multi-share branch scheme
common common flow meter multi-share branch is mainly divided into three schemes: all-SV branch scheme, all-hand valve branch scheme, single-SV control plus branch hand valve combination scheme. Among them, the all-hand valve scheme and the full SV scheme on the accurate measurement requirements are basically the same. The PUD operation of this unit is a full SV branch scheme, and the PA operation is a single SV control plus branch hand valve combination scheme.
3. 1 All-SV branching scheme
all-SV branch scheme can be divided into the following 4 basic situations, see Figure 1, each scenario analysis can be seen in Table 1.
analysis shows that scenario (1) is not available when there is a feed time limit. Scenario (2) Is not available when the media does not allow fluid build-up. Scenario (3) does not enable accurate metering. The recommended scenario (4). Extension: Any combination between scenarios (1) and (4) is not possible.
3. 2 Single SV control plus branch hand valve combination scheme
single SV control plus branch hand valve combination scheme can be divided into the following 4 basic conditions, see Figure 2, each scheme analysis see Table 2.
analysis shows that scenario (5) is not available when there is a feed time limit. Scenarios (6) and (7) do not achieve accurate metering. Scenario (8) Is not available when fluid build-up is not allowed on the medium.
: Any combination between scenarios (5) and (8) is not possible.4 Options
4. 1 PUD process selection scheme
acetone, process water due to its allowable fluid accumulation, scheme (1), (2), (4) can be selected, considering the requirements to minimize the distribution around the kettle, the basic choice of option (1), but for the process water used in the dispersing kettle due to its time constraints and choose the scheme (2).
4. 2 PA process selection options
HDI, TDI, HMDI and other media that do not allow fluid build-up (4). Process water allows fluid build-up and option (8) is selected.5 Conclusion
by analyzing the whole SV branch scheme and the single SV control plus branch hand valve combination scheme, the results show that it is feasible to measure multi-share branches using a common flow meter. The choice of scheme is limited by equipment arrangement, media characteristics and pipe space.