[Q&A Question 224] 11/30/2016
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【Q&A Question 224】November 30, 2016: How is reactor pressure drop formed? What factors are related to it? A reference ** will be shown after responding; scoring is achieved by answering the key points. The bed pressure drop is mainly caused by the effects of the following forces: (1) the acceleration and deceleration of the fluid in the bed, as well as the inertial forces resulting from vapor-liquid turbulence in local areas ； (2) The effect of viscosity on fluid flow at gas-liquid, liquid-solid, and gas-solid interfaces ； (3) The effect of interfacial forces (capillary forces) is particularly significant in foamed liquids ； (4) The liquid is under the effect of static pressure. Within regions of strong interaction between the phases, the inertial forces of the gas-liquid phases play a major role, while in regions of weak interaction, it is primarily the viscous forces and interfacial forces that have a significant impact. Therefore, the bed pressure drop is related to factors such as the mass flow rates of the gas and liquid phases, fluid properties, and bed porosity. Summary post of Q&A from 2016 (updated as of November~~~~) http://bbs.hcbbs.com/thread-1597792-1-1.html Seeking sponsors for the “2016 Haichuan Top 10 Members Selection Contest” http://bbs.hcbbs.com/thread-1628108-1-1.html (Source: Haichuan Chemical Forum)
The influencing factors include: ① An increase in reaction temperature leads to a higher cracking temperature, increased H2 consumption, and a drop in pressure. ②Fluctuations in the amount of fresh hydrogen or failures in the fresh hydrogen generator can cause pressure fluctuations. ③As the moisture content of the raw material increases, the pressure rises. ④Leakage in the heat exchanger where the reaction products exchange heat with recycled hydrogen, as well as in the high and low pressure heat exchangers, caused a drop in pressure. ⑤Cold high-pressure loss of control. The pressure drop caused by energy loss as fluid flows through a pipe. This energy loss is caused by the internal friction that must be overcome during fluid flow, as well as by the collisions between fluid particles and the exchange of momentum that occurs due to turbulence; it manifests itself as a pressure difference, namely pressure drop, between the upstream and downstream sections of the fluid flow. The magnitude of the pressure drop varies with the flow velocity inside the pipe.
Pressure drop refers to the pressure loss of the reactants as they pass through the reactor; a higher value indicates greater resistance in the reactor bed. Thus, the pressure drop can be used to check whether there is any blockage in the reactor bed.
The bed pressure drop is mainly caused by the effects of the following forces: (1) the acceleration and deceleration of the fluid in the bed, as well as the inertial forces resulting from vapor-liquid turbulence in local areas； (2) The effect of viscosity on fluid flow at gas-liquid, liquid-solid, and gas-solid interfaces ； (3) The effect of interfacial forces (capillary forces) is particularly significant in foamed liquids ； (4) The liquid is under the effect of static pressure. Within regions of strong interaction between the phases, the inertial forces of the gas-liquid phases play a major role, while in regions of weak interaction, it is primarily the viscous forces and interfacial forces that have a significant impact. Therefore, the bed pressure drop is related to factors such as the mass flow rates of the gas and liquid phases, fluid properties, and bed porosity.
The reactor pressure drop is primarily concentrated in the first bed layer, which is related to the metal and impurity content of the raw materials used in normal operations; additionally, the emergency pressure relief process carries impurities into the reactor
The reactor pressure drop is caused by: 1. Catalyst fragmentation； 2. Catalyst coking ； 3. Impurities introduced into the reactor by the system ； 4. Local collapse of the bed layer. Related factors: 1. Catalyst quality ； 2. Catalyst loading quality ； 3. System cleanliness ； 4. Low-flow, over-temperature operation
(1) System impurities enter the reactor； (2) The dechlorination tank is saturated with adsorbents, and pipeline equipment is blocked by salt deposits ； (3) Catalyst coking (caused by temperature, pressure, raw material dry point, etc.) ； (4) Increased pre-hydrogenation feed rate ； (5) Increased amount of hydrogen mixed in during pre-hydrogenation ； (6) In winter, the ambient temperature is low.
1. Poor quality of raw materials leads to catalyst coking； 2. Solid particles and the like are present in the raw materials and have not been removed by the filter ； 3. Damage to the catalyst leads to an increase in pressure drop ； 4. The amount of raw material processed increases, resulting in an increase in space velocity and a greater pressure drop ； 5. An increase in reaction temperature leads to a higher yield of gaseous products and a greater pressure drop.
Liquids are subjected to static pressure. Within regions of strong interaction between the phases, the inertial forces of the gas-liquid phases play a major role, while in regions of weak interaction, it is primarily the viscous forces and interfacial forces that have a significant impact
The bed pressure drop is mainly caused by the effects of the following forces: (1) the acceleration and deceleration of the fluid in the bed, as well as the inertial forces resulting from vapor-liquid turbulence in local areas； (2) The effect of viscosity on fluid flow at gas-liquid, liquid-solid, and gas-solid interfaces ； (3) The effect of interfacial forces (capillary forces) is particularly significant in foamed liquids ； (4) The liquid is under the effect of static pressure. Within regions of strong interaction between the phases, the inertial forces of the gas-liquid phases play a major role, while in regions of weak interaction, it is primarily the viscous forces and interfacial forces that have a significant impact. Therefore, the bed pressure drop is related to factors such as the mass flow rates of the gas and liquid phases, fluid properties, and bed porosity.