# Application of Digital Twin in Handling and Transportation of Hazardous Chemicals
## 2 Literature Review
### Current Situation of Hazardous Chemicals  
Most countries all over the world are strengthening the monitoring of \"carbon emissions\" and environmental protection during development. China is also scientifically eliminating backward industries and shutting down highly polluting factories according to the monitoring results of the environmental protection department. In this context, clean energy, represented by liquefied natural gas (LNG) and liquefied petroleum gas (LPG), has become the most important industrial and civil energy, and the demand for them will continue to expand in the future. Their filling locations are mainly divided into two categories: the ports close to the market and the inland Chemical Industry Park [1], and their unloading locations are energy consumer terminals distributed throughout the country, which can be roughly divided into four categories: chemical enterprises, power plants, manufacturing, and urban gas enterprises. However, the chemicals used are all dangerous with low-temperature, flammable, and explosive properties. The majority of them need to be transported by road to consumer terminals, which become mobile hazard sources. Accidents in the process of loading and unloading pose a threat to the entire industrial zone where the station is located, and accidents in the process of road transportation seriously affect the function of the road network. [PERSON] et al. analyzed 5207 hazardous chemical leakage accidents in the period of 2009-2018 in China and found that most accidents occurred in the road or the pipeline transportation process. This kind of accident is more likely to occur between 6:00 AM-10:00 AM and 3:00 PM, and the high mortality rate occurs between 0:00 AM-5:00 AM in road transportation [2]. Additionally, [PERSON] et al. studied the current LNG infrastructure risk analysis model and sorted it comprehensively; it will help managers to choose the proper model according to the different conditions [3].  
Active safety is based on the comprehensive control of all links in the production or transportation process [4]. China has released a series of important government documents to promote hazardous chemical safety [5], but [PERSON] analyzed 3974 hazardous chemical casualty accidents that occurred between 2006 and 2017 in China and found that there is a probability of 59.10% that 200-600 casualty accidents will occur per year. Fourteen provinces need better safety management with regard to hazardous chemicals [6]. As explained by [PERSON], the breakthrough progress in some key and common technologies limiting the improvement of hazardous chemical safety has not been achieved yet. Meanwhile, some advanced safety management approaches and safety technology means have not been widely used in hazardous chemical enterprises [5]. In the specific loading and unloading operation process, the working scope of personnel at each post is difficult to communicate with others and the degree of information sharing is insufficient; therefore, enterprises cannot effectively monitor the standardization of on-site operation. In road transportation, tankers transporting hazardous chemicals are driving in different positions, and the transportation enterprises cannot grasp the driving behavior of drivers and the complex traffic conditions they are facing. All of the above show that all departments still lack effective monitoring and intervention, and it is difficult to achieve \"active safety\".