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Intelligent Safety Detection of Phosphine Gas in Grain Depot

2019-03-02 20:21:42
Macro-control of grain is the main means to maintain national food security, and grain depot is the basis of macro-control of grain. Therefore, intelligent control and precise management of grain depots are the key to achieve safe and efficient grain storage.
The most important thing in grain storage is insecticidal treatment. Aluminum phosphide is a very effective insecticide for grain storage, which is widely used in grain storage in China. When water or moisture is absorbed, it can dehydrate and release phosphine gas with severe toxicity. The grain depot laboratory staff will be exposed to phosphine gas when they take samples and test temperature, humidity and inspect grain and insect conditions. Some of them are poisoned by phosphine due to lack of safety and hygiene knowledge.

In order to investigate the concentration of phosphine in the granary during fumigation and the time when it falls below the national hygienic standard after fumigation, it is necessary to monitor the concentration of phosphine in the granary after fumigation and the concentration of oxygen, carbon dioxide and other gases in the environment, so as to provide scientific basis for the protection of human health. During the fumigation period, the phosphine concentration in silos and grain piles was very high, peaking at 48 hours and 96 hours, and much higher than that in grain piles in the first two days. However, with the passage of time, the difference between the two becomes smaller and tends to be balanced, which indicates that the hydrogen phosphide produced by aluminium phosphide after deliquescence quickly diffuses in the silo and gradually permeates into the grain heap. The concentration of hydrogen phosphide in the silo decreases to near the national health standard two days after opening and venting. After the second closure, the phosphine concentration in the grain stack decreases gradually, while that in the grain stack increases first and then decreases. This indicates that the phosphine in the grain stack gradually releases into the space of the grain stack after the second closure, which results in the increase of the phosphine concentration in the grain stack. It was not until the 9th day that the concentration of phosphine in grain piles and warehouses fell below the national hygienic standards. It is safer to enter the warehouse about half a month after fumigation.
On the basis of the existing digital temperature measurement, the grain condition monitoring and early warning module of the warehousing business management system should also integrate the functions of automatic analysis of the gas, humidity and Insect Pests Detection in the grain stack, and the measured data should be written into the historical database to provide large data support for the accurate decision-making of scientific grain storage. On this basis, an expert decision-making system of grain condition should be established step by step. When abnormal changes occur in the grain situation, the alarm sent by the system directly notifies the responsible mobile phone, and according to the ecological digital model of grain storage in this area, after comprehensive analysis of the system, recommend treatment suggestions; even directly related to intelligent ventilation, fumigation and insecticide, controlled atmosphere storage and other equipment, after authorization, automatically take corresponding measures to truly achieve the completion of "measurement" and "control". Integration of the United States. The following figure shows the model of grain depot comprehensive monitoring system:
Alphasense, a two-year conventional electrochemical principle phosphine sensor, is represented by Apollo Company. It is specially used for monitoring and alarming phosphine concentration in granaries or industries. It has good stability, high sensitivity, fast response and high cost performance. It also has 10 ppm small range PH3-A1/B1 and 2000 ppm large range PH3-BE optional.
The main performance parameters are as follows:
1. Test range: 0-10 ppm (A1/B1) 0-2000 ppm (BE)
2. Sensitivity: 550-900nA/ppm (A1); 600-1000nA/ppm (B1); 15-35nA/ppm (BE)
3. High resolution: 0.03 ppm (A1/B1); 2 ppm (BE)
4. T90 response time: < 25s (A1/B1); < 30s (BE)
5. Working environment: - 30-50 C, 10-90% RH