Scale-up Design Research Articles

Numerical investigations on hydrothermal flame characteristics of water-cooled hydrothermal burner

Abstract Supercritical hydrothermal combustion, as a quick homogeneous oxidizing process, offers a promising treatment option for industrial wastewater. This paper established a computational fluid dynamics model of a water-cooled hydrothermal combustion burner to investigate the thermal flame characteristics. The effects of the fuel mass flow rate, fuel concentration, initial reactor temperature, reaction pressure, and oxidant temperature on the thermal combustion ignition were revealed. The results indicate that the fuel concentration (from 10 wt% to 60 wt%) and initial reactor temperature (from 623 to 773 K) had less effect on the ignition temperature. In contrast, the ignition temperature increases by 398 K with increasing fuel mass flow rate (from 24 kg h−1 to 1080 kg h−1). As the oxygen temperature increases (from 273 to 673 K), the ignition temperature gradually decreases to 573 K and then increases. An increase in reaction pressure can facilitate a decrease in ignition temperature to a certain extent, and the optimal reaction pressure is 25 MPa. This study provides a vital reference for a hydrothermal burner’s scale-up design and ignition operation.

Reaction Calorimetry and Scale-Up Considerations of Bromo- and Chloro-Boron Subphthalocyanine

The formation mechanism of boron subphthalocyanines (BsubPcs) has thus far evaded researchers, making it nearly impossible to accurately estimate the overall reaction enthalpy─a critical metric for determining chemical process safety for scale-up. To address this gap, reaction calorimetry was used to collect thermokinetic data for a baseline Br-BsubPc reaction at three temperatures and two BBr3 reagent ratios and a proposed semibatch process for Cl-BsubPc. For the Br-BsubPc process, the magnitude of the enthalpy of reaction (ΔHr) increased with increasing reaction temperature, from −244.6 kJ/mol-BBr3 at 25 °C to −332.7 kJ/mol-BBr3 at 50 °C to −391.3 kJ/mol-BBr3 at 75 °C. However, this increase in the magnitude of ΔHr did not result in a noticeable increase in Br-BsubPc yield, achieving 50%, 49%, and 52% yields at 25 °C, 50 °C, and 75 °C, respectively. When the molar equivalence of BBr3 was increased by 1.5× at 25 °C, the magnitude of ΔHr increased slightly (−252.2 kJ/mol-BBr3), but the yield did not improve (47%). Therefore, further attempts were made to try and improve the yield of Br-BsubPc by increasing the molar equivalence of BBr3. It was found that BBr3 equivalencies greater than 0.48 resulted in significant reductions in Br-BsubPc yield. The ΔHr of the semibatch Cl-BsubPc process was −266.5 kJ/mol-BCl3 with a yield of 33%. These processes were assessed based on criticality criteria and were both found to be “Criticality Class 1”, which is relatively safe for scale-up. Based on the calorimetry measurements, preliminary estimates for process conditions and reactor design for scale-up are provided.

Integrating chemical coagulation with fixed-bed column adsorption using rice husk-derived biochar for shipboard bilgewater treatment: Scale-up design and cost estimation

Discharging shipboard bilgewater (SBW) into seas and oceans without proper treatment could poison marine organisms and negatively impact transportation-related activities. This study focuses on the treatment of synthetic SBW using a simple and cost-efficient physico-chemical process. This treatment system included coagulation-flocculation (CF) using alum coagulant and fixed-bed column adsorption using rice husk-derived biochar (RHB). The optimization and effect of CF process parameters, viz., pH, fast stirring speed, and alum dosage, on surfactant and COD removal efficiencies were studied using a central composite design-response surface methodology (CCD-RSM). At optimum conditions (pH of 6.4, rapid mixing speed of 160 rpm, and coagulant dosage of 140 mg/L), the surfactants and COD removal efficiencies were 46.31±1.48% and 84.67±2.61%, respectively. The adsorption column optimum conditions were flow rate= 5 mL/min and bed depth= 16 cm, giving a surfactant removal efficiency of 96.6%. The primary adsorption mechanism was physisorption, including electrostatic attraction, hydrogen bonding, pore-filling, and hydrophobic interaction, as revealed by SEM, EDX, and FTIR characterizations. The adsorption data fitted well with Thomas model predictions, giving the best kinetic constant (KTh)= 0.305 mL/min/mg and equilibrium surfactant uptake (qo)= 11.05 mg/g (R2= 0.996). The Thomas model's coefficients were successfully used to predict the breakthrough curves and determine the column dimensions for pilot-scale (3 L/h) and large-scale (300 L/h) fixed-bed adsorption units. The estimated cost for the on-board treatment of SBW by the proposed system was 2.51 US$/m3. Future studies are required to implement the proposed combined coagulation/flocculation/adsorption system to treat real SBW from medium-sized ships.

The Collaborative Service Design Playbook to plan, design, and implement sustainable health services for impact

This paper sets out the Collaborative Service Design Playbook, to guide planning, design, and implementation of co-created health services. Successful health service development and implementation is best guided by theoretically informed approaches; however, organisations often lack design and implementation know-how and have difficulty applying it. This study seeks to improve health service design and potential for scale-up by proposing a tool to guide an end-to-end process, drawing together service design, co-design, and implementation science; and exploring the tool’s feasibility to establish a sustainable service solution developed with participants and experts that is scalable and sustainable. The Collaborative Service Design Playbook phases include, (1) Define the opportunity and initiatives, (2) Design the concept and prototype, (3) Deliver to scale and evaluate; and (4) Optimise to transform and sustain. This paper has implications for health marketing through providing an end-to-end approach with phased guidance for health service development, implementation, and scale up.

Numerical simulation of cavitation performance in a scaled-up bath-type sonoreactor considering inhomogeneous bubble cloud

The bath-type sonoreactor holds great potential in industrial applications of process intensification. However, the scale-up of this bath-type sonoreactor is limited by a lack of investigation into sonoreactor design. In this work, we employed linearized wave equation considering inhomogeneous bubble distribution for simulation of scale-up bath-type sonoreactor design. Comprehensive validation experiments were conducted to verify simulation accuracy. This model predicts abnormal attenuation phenomenon during sound waves transmission that pose challenges for optimal design of sonoreactors. The result implies that increasing driving pressure cannot constantly increase conversion rate of cavitation energy. For example, as driving pressure increases, cavitation rate become stabilized to be a constant value of 0.4 and average cavitation pressure tends to be 1.1 times of driving pressure. Reactor width determines cavitation area and a width of 350 mm generates most cavitation volume under a liquid level of 100 mm. Regardless of the liquid level, increasing the driving pressure causes sound pressure in the near-field decrease due to abnormal attenuation. Once sound wave has travelled to a distance of 60–80 mm, cavitation will not make a noticeable difference.

Utilization of Quality by Design, Kinetic Modeling, and Computational Fluid Dynamics for Process Optimization and Scale-Up

Under acidic conditions, 16-α hydroxy prednisolone (16-AHP) reacts with n-butyraldehyde through acetalization and epimer conversion to produce budesonide. To further understand the conversion of epimers, a kinetic study was conducted. Epimer A is converted to epimer B depending on the temperature and time following acetalization. Failure mode and effect analysis (FMEA), followed by the design of experiments, was used to identify and optimize the crucial process parameters. After purification and crystallization, the finished product was obtained. Maintaining the necessary epimer ratio and regulating the contaminants within the specifications were the biggest hurdles to the process. Even though all critical process parameters (CPPs) were under control and the mixing or velocity profile was accurately matched by computational fluid dynamics (CFD) simulation, it was a surprise when a few oxidation impurities formed at substantially higher levels during scale-up. To find the underlying causes, a thorough investigation was made. It was discovered that certain oxidation impurities were created during crystallization in the presence of dissolved oxygen, a metal reactor vessel, the temperature of the solution, and traces of hydrobromic acid (HBr). The process was successfully scaled-up with the desired quality after reoptimization and the establishment of an appropriate control approach for the CPPs.

Performance evaluation of a pilot-scale membrane filtration system for oily wastewater treatment: CFD modeling and scale-up design

The discharge of oily wastewater into the environment adversely impacts the ecosystem and human health due to the existence of toxic and carcinogenic compounds in oil. To decrease the destructive environmental impacts, membrane filtration technology has been used because it can remove emulsified oil with droplet sizes ranging from 1 to 10 μm which is a challenging issue for other types of treatment methods. In this research, a comprehensive 3D CFD model was developed to investigate the oily wastewater treatment process in a pilot-scale membrane filtration system. The model was validated using available data in experimental runs such as oil removal efficiency and average transmembrane pressure (TMP) for two types of oily wastewater containing heavy and light crude oils. Following that, the hydrodynamic condition of the pilot-scale unit was analyzed which is difficult to be investigated in a real condition. The impacts of inlet oil concentration, permeate, and aeration flow rates on permeate oil concentration and TMP were also evaluated. Results revealed when the inlet oil concentration was at the threshold of 270 and 330 mg/L containing heavy and light crude oil, respectively, the system met the International Convention for the Prevention of Pollution from Ships (MARPOL) 73/78 regulation. Additionally, the model was capable of predicting TMP changes under constant flux. Finally, the validated model was used to upscale the pilot-scale system to achieve a permeate production rate of 10,000 L/h for larger capacities. Based on the results, the oil removal efficiency was above 88 % in pilot and upscaled systems.

Study on Thermal Degradation Processes of Polyethylene Terephthalate Microplastics Using the Kinetics and Artificial Neural Networks Models

Because of its slow rate of disintegration, plastic debris has steadily risen over time and contributed to a host of environmental issues. Recycling the world’s increasing debris has taken on critical importance. Pyrolysis is one of the most practical techniques for recycling plastic because of its intrinsic qualities and environmental friendliness. For scale-up and reactor design, an understanding of the degradation process is essential. Using one model-free kinetic approach (Friedman) and two model-fitting kinetic methods (Arrhenius and Coats-Redfern), the thermal degradation of Polyethylene Terephthalate (PET) microplastics at heating rates of 10, 20, and 30 °C/min was examined in this work. Additionally, a powerful artificial neural network (ANN) model was created to forecast the heat deterioration of PET MPs. At various heating rates, the TG and DTG thermograms from the PET MPs degradation revealed the same patterns and trends. This showed that the heating rates do not impact the decomposition processes. The Friedman model showed activation energy values ranging from 3.31 to 8.79 kJ/mol. The average activation energy value was 1278.88 kJ/mol from the Arrhenius model, while, from the Coats-Redfern model, the average was 1.05 × 104 kJ/mol. The thermodynamics of the degradation process of the PET MPs by thermal treatment were all non-spontaneous and endergonic, and energy was absorbed for the degradation. It was discovered that an ANN, with a two-layer hidden architecture, was the most effective network for predicting the output variable (mass loss%) with a regression coefficient value of (0.951–1.0).

Evaluation of monolith catalyst in catalytic combustion of anode off-gas for solid oxide fuel cell system

Solid oxide fuel cells (SOFC) can operate at high temperatures (> 650 °C) and have attracted attention because of their high efficiency. However, the CH4, CO, and H2 contained in the anode off-gas that are not reformed or does not participate in the SOFC power generation process must be treated. A catalytic combustion process, which can improve the efficiency by treating the target substances and heat recovery, is essential for this purpose. This study examined the CH4 combustion performance of Pd- and Pt-supported catalysts in the presence or absence of H2O in the feed, at O2/2CH4 ratios of 15 and 20, at a gas hourly space velocity (GHSV) of 5000, 10,000, and 20,000 h−1, and at inlet temperatures of 100–580 °C. The Pd-rich catalyst with a cell per square inch of 400 exhibited the best CH4 combustion performance, as CH4 combustion was possible even at an inlet temperature of 200–300 °C. The performance of this catalyst was evaluated by applying it to a 5-kW scale catalytic combustor. CH4, CO, and H2 combustion experiments of the catalyst in this apparatus were performed at a O2/C of 12–15, GHSV of 8400–16,800 h−1, and inlet temperatures of 100–580 °C, and CO and H2 conversions exceeding 98 % and a CH4 conversion exceeding 75 % were obtained. We expect that the results of this study can be used for the scale-up design of high-efficiency SOFC systems capable of reducing the concentrations of emitted CO and CH4 and utilize the heat generated in the power generation process through the AOG catalytic combustor.

Triple Benefit: Impact of an Integrated Early Childhood Development and PMTCT Intervention on ART Outcomes Among Mothers Living with HIV and Infants in Malawi—An Endline Evaluation

We conducted a programmatic, observational cohort study with mother-infant pairs (MIPs) enrolled in prevention-of-mother-to-child-transmission (PMTCT) programs in Malawi to assess the feasibility and potential HIV-related benefits of integrating Early Childhood Development (ECD) services into PMTCT programs. Six health facilities were included in the intervention. We offered ECD counseling from the WHO/UNICEF Care for Child Development package in PMTCT waiting spaces while MIPs waited for PMTCT and broader treatment consultations. Primary outcomes were mothers’ retention in HIV care at 12 months and infant HIV testing at 6 weeks and 12 months after birth. Routine facility-level data from six comparison health facilities were collected as an adhoc standard of care comparison and used to calculate the cost of delivering the intervention. A total of 607 MIPs were enrolled in the integrated ECD-PMTCT intervention between June 2018 and December 2019. The average age of MIPs was 30 years and 7 weeks respectively. We found that 86% of mothers attended ≥ 5 of the 8 ECD sessions over the course of 12 months; 88% of intervention mothers were retained in PMTCT versus 59% of mothers in comparison health facilities, and 96% of intervention infants were tested for HIV by six weeks compared to 66% of infants in comparison health facilities. Costing data demonstrated the financial feasibility of integrating ECD and PMTCT programs in government health facilities in Malawi. Integrating ECD into PMTCT programs was feasible, acceptable, resulted in better programmatic outcomes for both mothers and infants. Further investigation is required to determine optimal delivery design for scale-up.

Kinetic Modeling of Glycerol Hydrogenolysis: A Short Review

Glycerol hydrogenolysis represents one of the most promising technologies for future bio-refineries. In this context, kinetic modeling provides key quantitative assessment of the significance of various reactions for process development. However, as of present, there are only limited studies on detailed kinetic modeling of glycerol conversion to 1,2-propanediol, ethylene glycol and other alcoholic products. In this work, a comprehensive summary on kinetic modeling of glycerol hydrogenolysis has been conducted to reveal the possible mechanism involved in the activation of the C-H and C-O bond in glycerol molecules. In particular, power law and Langmuir–Hinshelwood model types have been critically discussed with mechanistic insights. The outcome of this review article will offer alternative views on the scale-up design of glycerol hydrogenolysis to glycols, as well as hydrogenolysis of various other bio-derived compounds to value-added chemicals.

Techno-economic analysis of MOF-based adsorption cycles for postcombustion CO2 capture from wet flue gas

In this study, we present a scale-up design, scheduling, and costing of a single-stage MOF (Metal-Organic Framework)-based 5-step temperature swing adsorption (TSA) process, which was recently shown to be effective for carbon capture and concentration (CCC) from wet flue gas containing 5 to 15 mol% CO2 without any pre-drying (Peh et al., 2022). This TSA process is also compared with a two-stage process at two feed conditions. In the two-stage process, the wet flue gas is first dried in a TSA process, and then CCC from the dry flue gas is carried out in a MOF-based 6-step vacuum swing adsorption (VSA) process. The TSA-based pre-drying process is also analyzed in detail. The two-stage process has lower minimum capture costs at both feed conditions ($91 versus $104.1 per tonne of CO2 captured at 25 °C and $113.3 versus $146.9 per tonne of CO2 captured at 40 °C).

Size-dependent growth kinetics model for potassium chloride from seeded chloride solution

Abstract It was widely known that crystallization kinetics are the basis for crystallization behavior and crystallizer scale-up design. Cooling crystallization of potassium chloride was an essential unit operation in recycling industry. Some researchers have proposed the strategy of adding seed crystals for the intermittent cooling crystallization process to control the particle size and distribution of the target product. This paper studied the complex function relation between particle size and growth rate of KCI in the crystallization process in a continuous mixed-suspension mixed-product-removal (MSMPR) crystallizer at a steady state. Using the crystallization kinetics data, the mathematical models of coupling crystallization were established based on the population balance equations and mass balance equations. Since population density distributions of products behave multiform under different conditions, based on diffusion theory. The growth rate was obtained by a least square method for the multivariate linear regression, and the reliability of the kinetics model was validated experimentally. Fitting results indicated that some classical models, including several size-independent growth models and size-dependent growth models, such as Bransom, C-R, MJ2, ASL, and MJ3, could not model the size-dependent growth accurately. Based on this situation, an exponential growth model was proposed and confirmed to describe the size-dependent growth behavior. It was found that the model parameters have definite meanings and were strongly related to particle size. Compared with the classical models, this model showed good pertinency and adaptability to experimental results when used to describe the population density distribution and the size-dependent growth rate of KCI. This research could provide a theoretical guide for optimizing the crystallization process and designing industrial crystallizers.

Sustainable high-pressure light-driven water pump with a spiral tube structure and Büttiker–Landauer ratchet

Developing sustainable water transportation technology is essential for solving water shortage problems. In this study, we proposed a sustainable high-pressure light-driven water pump that used a spiral tube structure (where light hit one side and shadowed the other) with a Büttiker–Landauer (BL) ratchet. Moreover, we examined the performance of this water pump. By using a polyurethane tube with a diameter of 2.5 mm and a length of 5 m, we demonstrated that the light-driven BL pump lifted water from a water source against the force of gravity, transported it horizontally along the spiral tube, and removed it from the tube against the surface tension. In particular, by the height scale-up design, we observed ∼800 times larger actual pressure difference (ΔP∼40 Pa) than the previous light-driven BL pump along with the pumping flow velocity up to 2.4 mm/s. In addition, by proposing a model that considers the effect of the transportation of heat energy from the hot region to the cold region, we explain the experimentally observed self-adjustment phenomenon for a flow velocity. Since our pump can work under sunlight without using electricity or fossil fuels, it is more sustainable than other pumps. Our findings should contribute to practical sustainable water transportation.

Effects of stator and rotor geometry on inline high shear mixers: Residence time distribution, flow, and energy consumption

Using high shear mixers (HSMs) as the vessel to intensify chemical processes requires knowledge of the residence time distribution (RTD) characteristic. Considering the numerous structural characteristics of HSMs, a series of pilot-scale HSMs was developed to investigate the RTD characteristics through pulse tracing and deconvolution. A number of structural parameters were included here, including tooth height, tooth thickness, and the number of rotor-stator tooth rows, slots, and stages. Meanwhile, by using CFD simulations with the large-eddy simulation model coupled with the sliding mesh method, the flow rate, power consumption, and energy dissipation rate distribution, as well as RTD of HSM were examined. It is illustrated that adding a distributor or increasing rotor speed improves the local energy dissipation, reducing short-circuits and dead zone. The RTD curves become smoother and closer to plug flow with increasing stator-rotor stages. Typical first/second-order reactions are favored by higher or thicker rotor-stator teeth, and HSM is better suited when kR1 > 1 s−1 or kR2cA0 > 5 s−1. Furthermore, the correlations of E(t), tR, σθ2, Potot, and qave, 1+ were obtained, which would provide useful guidance on the scale-up design and optimization of HSMs.

Scale-up Design and Treatment Cost Analysis for Abatement of Hexavalent Chromium and Metanil Yellow Dye from Aqueous Solution Using Mixed Phase CaFe2O4 and ZrO2 Nanocomposite

Scale-up Design and Treatment Cost Analysis for Abatement of Hexavalent Chromium and Metanil Yellow Dye from Aqueous Solution Using Mixed Phase CaFe2O4 and ZrO2 Nanocomposite

Removal of methylene blue by H3PO4Treated eucalyptus leaves: Study of fixed bed column and GA-ANN modeling

This investigation aims to implement the fixed bed column method to eliminate methylene blue (MB) by H3PO4 treated eucalyptus leaves (PEUL). PEUL is characterized using SEM, XRD, FTIR, solid-state NMR, and BET surface areas. Initially, the batch experiments revealed that the maximum percentage removal of MB is obtained at pH 8. The column experiments are performed at pH 8 and 25 °C with a varying bed height (5–9 cm), rate of flow (10–20 ml min−1), and MB concentration (10–50 mg L−1). The column experimentation shows that the breakthrough and exhaustion times rise with the bed's height but decrease with the increasing rate of flow and MB concentration. Different well-known kinetic models are tested with the experimental results, which display that the Thomas model (R2 = 0.9969, χ2 = 0.0005) fits better than others, so it is appropriate for the scale-up design. The Langmuir isotherm model (R2 = 0.9949) is superior to the Freundlich model (R2 = 0.9516). The Langmuir maximum adsorption capacity is 52.18 mg g−1, which suggests monolayer adsorption. Desorption of MB from used adsorbents with CH3COOH solution (0.4 N) suggests 55.10% regeneration efficiency. The used adsorbents are safely disposable after incineration at 800 °C. This innovative study suggests that the inexpensive H3PO4 treated eucalyptus leaves feasible to use effectively for MB removal from the wastewater. The modeling using multiple linear regressions shows a statistically good result. The applicability of GA-ANN modeling is also tested.

Performance evaluation of zirconium silicate composite for removal of cadmium and zinc ions

ABSTRACT The purification of wastewater is preferred using the adsorption by column due to the process’s high efficiency. Column investigations are performed to remove hazardous pollutants and demonstrate the adsorption efficiency of the pollutants in the wastewater treatment process. Cadmium and zinc exist in radioactive and industrial wastes. Therefore, this work is interested in zinc and cadmium removal from wastewater utilising a fixed-bed column. Zirconia–silicate composite (ZrO2–SiO2) was synthesised utilising the sol–gel technique and analyzed for this purpose. The influence of some parameters as bed depth (2.0, 3.0 and 5.0 cm), flow rate (2.0 and 3.0 mL/min) and initial ions concentrations (50–200 mg/L) was investigated. The column performance was computed to be 80.3 and 79.3% for Zn2 + and Cd2+, respectively, at the optimum conditions (3.0 cm bed depth, 2.0 mL/min flow rate and 100 mg/L ions concentration). Thomas, Adams–Bohart and Yoon–Nelson theories were performed to assess breakthrough curves and determine the parameters of column models which are essential for scale-up design. Thomas theory exhibited the highest R 2 values (0.84–0.97) and gave the most accurate computation of the adsorption process.

ZIF-derived Co/NCNTs as a superior catalyst for aromatic hydrocarbon resin hydrogenation: Scalable green synthesis and insight into reaction mechanism

The large-scale synthesis of transition metal catalysts with high performance and their catalytic mechanism for hydrogenation is of great importance for the development of a cost-effective alternative to noble metal catalysts. Herein, we report a facile and high-yield approach for the large-scale production of highly active Co/NCNTs catalyst transformed from zeolitic imidazolate frameworks (ZIFs). The precursor ZIF-67 could be easily prepared in an aqueous solution at room temperature in a short time (∼30 min) with a high space–time-yield. Followed by low-temperature (450 °C) pyrolysis, the Co/NCNTs catalyst was obtained in high yield. Benefiting from the high density and accessible active sites, Co/NCNTs-450 exhibits high activity in hydrogenation of aromatic hydrocarbon resin (AHCR) at 160 °C and 3 MPa (for the first time below 5 MPa), which was superior to the 5 wt% Pd/C. Furthermore, a combination of kinetic experiments and density functional theory (DFT) calculations were conducted to provide insight into the mechanism of AHCR hydrogenation. The 21 kinetic models based on the Eley-Rideal (ER) and Langmuir-Hinshelwood-Haugen-Watson (LHHW) formalism were proposed to describe the kinetic data obtained via elimination of the mass transfer limitations. On the basis of the model discrimination and regression results, the LHHW mechanism presented the best fit. And all the estimated kinetic parameters, including rate constants and activation energy, could be used in a reactor design for process scale-up. The DFT calculations further corroborated the kinetic modeling results that the surface reaction of chemisorbed AHCR and the dissociatively adsorbed hydrogen was the rate-determining step.

Process Evaluation of an Application-Based Salt Reduction Intervention in School Children and Their Families (AppSalt) in China: A Mixed-Methods Study.

BackgroundSalt reduction is a cost-effective, and rather challenging public health strategy for controlling chronic diseases. The AppSalt program is a school-based multi-component mobile health (mhealth) salt reduction program designed to tackle the high salt intake in China. This mixed-methods process evaluation was conducted to investigate the implementation of this program across sites, identify factors associated with the implementation, and collect evidence to optimize the intervention design for future scale-up.MethodsMixed methods were used sequentially to collect data regarding five process evaluation dimensions: fidelity, dose delivered, dose received, reach, and context. Quantitative data were collected during the intervention process. Participation rate of intervention activities was calculated and compared across cities. The quantitative data was used for the selection of representative intervention participants for the qualitative interviews. Qualitative data were collected in face-to-face semi-structured interviews with purposively selected students (n = 33), adult family members (n = 33), teachers (n = 9), heads of schools (n = 9), key informants from local health, and education departments (n = 8). Thematic analysis technique was applied to analyze the interview transcripts using NVivo. The qualitative data were triangulated with the quantitative data during the interpretation phase.ResultsThe total number of families recruited for the intervention was 1,124. The overall retention rate of the AppSalt program was 97%. The intervention was implemented to a high level of fidelity against the protocol. About 80% of intervention participants completed all the app-based salt reduction courses, with a significant difference across the three cities (Shijiazhuang: 95%; Luzhou: 73%; Yueyang: 64%). The smartphone app in this program was perceived as a feasible and engaging health education tool by most intervention participants and key stakeholders. Through the interviews with participants and key stakeholders, we identified some barriers to implementing this program at primary schools, including the left-behind children who usually live with their grandparents and have limited access of smartphones; perceived adverse effects of smartphones on children (e.g., eyesight damage); and overlooked health education curriculum at Chinese primary schools.ConclusionThis process evaluation demonstrated the feasibility and acceptability of using smartphone applications delivered through the education system to engage families in China to reduce excessive salt intake.Clinical Trial RegistrationThe AppSalt study was registered at www.chictr.org.cn, identifier: ChiCTR1800017553. The date of registration is August 3, 2018.