There are numerous parameters that can be varied, including temperature, pressure, type of reaction solution, absolute and relative flow rates, flow type, and so on. It is impossible to cover all of these parameters in a single day of testing. We recommend the following approach:

*Regarding pressure, it is common to fix it at the maximum pressure of the equipment that is planned to be introduced in the future (except for batch experiments under the vapor pressure condition of subcritical water).

*The flow ratio is determined so that the temperature after mixing high-temperature water (supercritical or subcritical) with ambient-temperature feed reaches the target value. In cases where the temperature reaches 380°C after mixing, he flow rate of the raw material is often set to 10-30% of the supercritical water flow rate.

*The flow rate of high-temperature water is determined by the heater capacity rather than the pump capacity. If you want to use more than 10 ml/min of supercritical water, additional heaters are employed.

*Regarding the type of solution, it is advisable to consider the ion species and pH. For SUS316 piping, the pH range typically falls between 3 and 11.  Additionally, chloride ions can strongly corrode SUS materials, so for acids, nitric acid or acetic acid is commonly used. Inconel-lined titanium piping is used under severe conditions, but it is not recommended due to the cost and lead time.

*In addition to aqueous solutions, slurries can also be used as feedstocks. For example, in the case of synthesizing oxide particles, hydroxide slurries are more effective than aqueous solutions in preventing pipe clogging. Since pipe blockage is a major challenge in particle synthesis, slurries are considered an important option.

*When using biomass slurries as feedstock, it is important to use smaller particle sizes and lower concentrations to minimize the risk of blockage, as larger particle sizes are highly susceptible to clogging.

*The temperature has the most significant impact on the reaction. Even a 50°C change can often lead to completely different results,  making it a high-priority factor to consider. When investigating entirely unknown reactions, it is advisable to increase the temperature in 50°C increments as time allows.

*Regarding flow types, there are rapid heating, slow heating, and batch tests. Rapid heating involves mixing high-temperature water with room-temperature raw material liquid for instantaneous heating. Slow heating involves heating only the feed in the furnace without mixing, requiring a reaction tube coil. If a sufficiently long reaction time is desired, batch testing rather than flow testing is conducted.

*Although pure water is flowed for a certain period of time between different experimental conditions, this does not completely wash away the particles produced under the previous conditions. It is advisable to anticipate that the previous conditions will inevitably contaminate the subsequent conditions and design the experiment accordingly.