Traditional steam explosion technology was developed by W. H. Mason in 1928. However, from the physical perspective of blasting, this method cannot be called blasting but should be called steam thermal ejection technology. Thermal ejection technology generally refers to the process of releasing materials that have been steamed at high temperature and high pressure through a quick-release valve into a normal pressure receiving container. Because the materials pass through the quick-release valve one by one, the blasting pressure of the released materials decreases sequentially after passing through the valve. More importantly, the energy of the steam inside the blasted plant tissue cannot be released instantaneously in the form of an explosion, but is gradually released from the plant tissue.

　　In addition to this technology, there is another so-called "steam explosion" technology, namely puffing technology. This is a method frequently used in the food industry to process puffed foods, namely screw extrusion puffed food processing technology. Since both of the above technologies do not conform to the physical definition of "explosion," they do not belong to the category of "steam explosion".

　　1. Essential Attributes of Steam Explosion Equipment

　　The physical concept of an explosion is: the complete release of energy in a short period of time. In chemical reactions, nuclear reactions, and physical decompression processes, one of the characteristics that measures its suddenness is to see whether there is a "bang" sound during energy release, i.e., whether a shock wave is generated, and whether the reaction process is completed within milliseconds. For example, a firecracker loaded with a small amount of gunpowder can shatter its body, accompanied by a crisp and loud firecracker sound. Although fireworks have more gunpowder than firecrackers, because the gunpowder energy release is a long-term sequential release, the body cannot be shattered.

　　Therefore, whether it is an explosion caused by explosives or a pressure vessel, only when it has a sudden bang sound and can generate an explosion shock wave does it belong to a true explosion in the physical sense. In contrast, some decompression processes that rapidly reduce the pressure inside the container by opening the quick-release valve do not produce a millisecond-level shock wave. The participating reaction materials are sequentially released from high pressure to low pressure to achieve reaction equilibrium, so no violent bang sound is produced. The decompression process is far from reaching the millisecond level to reduce all the materials in the container to normal pressure, and it does not have the necessary conditions for explosion and steam shattering. Because these work processes take a long time and do not produce instantaneous high power, they cannot achieve the expected physicochemical effects of the explosion.

　　If the process of quickly opening the valve connected to the container is defined as steam explosion or another form of steam explosion, it will cause large-scale rewriting of the universally accepted physical definition of "explosion" in textbooks around the world. Therefore, the essential attribute of steam explosion equipment should first meet the maximum limit of explosion (venting) time. Since the steam penetration time of straw and other herbaceous materials is generally less than 1 second, the venting time of steam explosion equipment should not be greater than 0.1 seconds in order to generate a pressure difference, destroy the crystal lattice structure of cellulose, and produce a true steam explosion effect. The widely used ejection-type steam explosion equipment has an explosion time of 0.00875 seconds, which already meets this necessary condition.

　　2. Process Parameters of Steam Explosion Equipment

　　Main Parameters of Steam Explosion Process—Material Intrinsic Factors and Equipment Extrinsic Factors

　　2.1 Material Intrinsic Factors

　　Material intrinsic factors generally include: material type and tissue composition, moisture content, pre-soaking, chemical pretreatment, degree of pulverization, fluidity, etc. The selection of material type is fundamental to the direction of the project, and its tissue composition, growth characteristics, harvest yield, and suitable planting areas should be fully considered.

　　Moisture content is an easily overlooked important factor because it is not simply the basis for calculating dry matter; it also affects the biomass harvesting mode, transportation method, and storage method in production implementation. In addition, because the water in plant tissue cells has a direct and important impact on the steam explosion results, moisture content will also have an important impact on the process parameters of steam explosion equipment. Pre-soaking and chemical pretreatment are essentially other pretreatment methods combined with steam explosion methods and are also common contents of comparative experiments.

　　The degree of pulverization and fluidity are two interrelated factors that have a relatively small impact on the steam explosion results in most cases. However, in large-scale production, these two factors will have a key impact on the actual output of steam explosion equipment, the type of supporting pulverization equipment, pulverization power consumption, and the type of logistics transportation equipment, etc. In order to maintain consistency with the industrial production environment, the same conditions should also be used in steam explosion experiments.

　　2.2 Equipment Extrinsic Factors

　　Equipment extrinsic factors include: steam pressure (temperature), steam composition, pressure holding time, explosion (venting) time, etc. These factors are also the narrow sense steam explosion process parameters. Among them, steam pressure and pressure holding time can be controlled by the user and are the main comparative parameters commonly used in experiments.

　　Explosion (venting) time is an inherent parameter of the equipment. Because this parameter is determined by the structure and type of the steam explosion equipment itself, it is often overlooked. According to the principle of steam explosion, under the same energy, in order to obtain high explosion power, the explosion (venting) time needs to be close to zero. Therefore, under the same steam pressure and pressure holding time, different steam explosion equipment will produce different pretreatment effects due to its different explosion (venting) time. Therefore, in a more standardized and complete expression of steam explosion process parameters, the record and description of explosion (venting) time or steam explosion equipment type should be added.

　　In summary, the experimental objectives of the above parameters are determined by the material conversion direction, such as fiber ethanol, hemp degumming, xylose production, papermaking, etc., and the experimental results of different parameter combinations are evaluated accordingly.