Continuous Vacuum Research Articles

Characterization of a Modular Continuous Vacuum Screw Filter for Small-Scale Solid–Liquid Separation of Suspensions

A key enabler for the future success of continuous manufacturing in pharmaceutical and fine chemical production processes is the control of product quality. Since approx. 90% of all small molecular active pharmaceutical ingredients produced involve a crystallization step, a holistic view on its process chain is crucial in order to ensure a defined particle size distribution, high purity, and specific polymorphic form. Different concepts for small-scale continuous crystallization are available, improving the product qualities in comparison to batch. Continuous solid–liquid separations, on the other hand, are rather scarce. Therefore, we designed and characterized an innovative continuous vacuum screw filter (CVSF) for solid–liquid separation, washing, and drying of suspensions in a small scale (up to 10 g of solid per minute). This contribution shows the general working principle of the CVSF as well as a systematic investigation of varying operating parameters on the particle size distribution (PSD), residual moisture, and residence time distribution of the solid phase. As a model system, l-alanine/water is used. The results show that the PSD can be entirely maintained while ensuring a narrow residence time distribution of the solid phase with axial dispersion numbers between 18.7 and 76.2. The residual moisture is for all experiments in a good range of 20–25%. Furthermore, it could be shown that the operability is possible over 8 h. Summarizing, the modular setup of the CVSF offers a maximized flexibility and thus rapid adaptability to changing market demands and product requirements.

Drying of wolfberry fruit juice using low-intensity pulsed ultrasound

In this study, the low-intensity pulsed ultrasound-assisted vacuum drying (LPUVD) was applied to improve the efficiency in drying wolfberry fruit juice with acceptable quality. The low-intensity ultrasound used was 0.7 W/cm2, and the effects of pulsed ultrasound ratio and drying temperature on the drying kinetics and quality parameters (color, total flavonoid, total polyphenol content, DPPH radical scavenging activity and powder properties) were investigated and compared with continuous ultrasound-assisted vacuum drying (CUVD). It was shown that LPUVD offers an advantage over CUVD in quality retention, and LPUVD at 10 s: 10 s pulsed ultrasound ratio took only 30 min more than CUVD. Significant influence of pulsed ultrasound ratio on quality parameters was not observed (p ≥ 0.05). The minimal quality loss was found in the sample dried at 50 °C whereas the maximum was found in the sample dried at 40 °C. Also, the drying methods and conditions showed no significant effects on the powder properties. Overall, the optimal drying conditions of LPUVD was found to be drying temperature of 50 °C and pulsed ultrasound ratio of 10 s: 10 s. The findings in current work demonstrate that LPUVD is a promising drying technique for wolfberry fruit juice.

Comparative study of negative pressure wound therapy with moist gauze dressings in the treatment of leg ulcer wounds

Background: Leg ulcers are one of the most commonly encountered cases in any surgical out-patient department. Causes of leg ulcers vary from traumatic, diabetic, chronic venous insufficiency, trophic, hypertensive, and so on. The purpose of this study is to evaluate the safety and clinical efficacy of negative pressure wound therapy compared with moist gauze dressings to treat foot ulcer wounds.Methods: Patients presenting with leg ulcers to the department of general surgery, VMKVC hospital. 50 randomly selected patients will be assigned to the study group based on their willingness for undergoing topical negative pressure dressing and 50 patients to the moist gauze dressing, control group.Results: Most of the ulcer (45.4%) got healed by secondary intention through VAC. dressing. treating DFU with VAC therapy results in a better graft take rate (p=0.05) when compared to standard wound care. There is a statistically significant association found between interventions and the area of the ulcer on day 28.Conclusions: While moist gauze dressing can be applied to any wound surfaces, vacuum dressing is limited to certain surfaces and certain wounds exposing tendon sheath, blood vessels, bones, aponeurosis cannot be treated by vacuum dressing. The frequency of dressing is lower with continuous vacuum suction dressing, while moist gauze has to be changed twice a day to obtain favorable results.

Preparation and Optical Absorption Properties of Ternary Rare Earth Boride LaxPr1-xB6 Submicron Powders.

As multifunctional materials, rare-earth hexaborides (RB6) display many interesting physical properties such as optical absorption, magnetic and thermionic emission. With the wide application of rare earth hexaboride and the continuous extension of its research fields, researchers have studied the synthesis of multi-rare earth hexaboride nano-powders and their thermal emission and light absorption properties. In the present work, ternary Single-phase LaxPr1-xB6 submicron powders are successfully synthesized using a solid-state reaction, in which lanthanum chloride (LaCl₃) and praseodymium chloride (PrCl₃) are used as rare-earth source and NaBH₄ as the boron source under continuous vacuum conditions. The reaction temperature is 1150 °C and the holding time is 2 h. The Pr doping effects on crystal structure, grain morphology, and optical absorption properties were investigated using X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and ultraviolet-vis absorption measurements. The XRD patterns show that the diffraction peaks are sharp and well-defined, and no other extra impurity peaks were detected, indicating the characteristics of well-crystallized materials. It is found that all the LaxPr1-xB6 solid powders are of single phase. The SEM results demonstrate that the cubicshaped ternary LaxPr1-xB6 submicron crystals with a size of 50~200 nm are obtained. The TEM images reveal the cubic single-crystalline nature, and the FFT patterns implies the lattice fringe d = 0.416 nm which agrees well with the (100) crystal plane. The elements mapping results indicates that the Pr atoms occupied the lattice sites of LaB6. The optical absorption results show that the absorption valley of LaB6 are located at 591 nm. With the increase of Pr doping contents from 0.2 to 0.8, the absorption valley moves from 596.3 nm to 612.9 nm, indicating the characteristics of visible light high transparency. The first-principle calculation results manifest that the move of the absorption valley of LaB6 in the visible region after doping Pr is related to the decrease of kinetic energy of electrons near the Fermi plane. X-ray photoelectron spectroscopy (XPS) analysis shows that the La and Pr exist in the type of La3+ and Pr3+ in LaxPr1-xB6. Therefore, it exists as an efficient optical absorption material. The LaxPr1-xB6 should open up a new route to extend the optical applications of rare-earth hexaborides.

Clinical strategies for preservation of the exposed implant in chronic wounds and wound repair

Objective: To explore the clinical strategies for preservation of the exposed implant in chronic wounds and wound repair. Methods: From January 2016 to January 2019, totally 8 patients (4 males and 4 females, aged 10 to 73 years) sustaining postoperative chronic wounds with exposed implants were admitted to the Fourth Medical Center of PLA General Hospital. There were 2 cases of abdominal patch exposure after abdominal trauma surgery, 2 cases of titanium plate exposure post craniocerebral surgery, 3 cases of internal fixator exposure post orthopedic surgery, and 1 case of cerebrospinal fluid drainage tube exposure after craniocerebral surgery. The wound exudate was collected for bacterial culture on admission. On the basis of glycemic control and correction of anemia and hypoproteinemia, thorough wound debridement was performed as soon as possible and the wound area after debridement ranged from 2.0 cm×0.5 cm to 6.0 cm×5.0 cm. The wounds of 4 patients were immediately closed after debridement, including 1 case by primary closure, 1 case by primary closure after local filling of platelet rich plasma gel, and 2 cases by local flap transplantation, with flap size of 10.0 cm×8.0 cm and 12.0 cm×8.0 cm, respectively. The donor sites of flaps were sutured directly and all the incisions were treated with continuous vacuum sealing drainage (VSD) after surgery. The other 4 patients were treated with continuous VSD after debridement to improve the wound bed. The wound of 1 case healed gradually, 1 case received direct wound suturing, and the wounds of 2 cases were repaired with thin split-thickness skin grafts from the thigh or the head. The results of bacterial culture of wound exudate on admission, wound healing post surgery, and follow-up were observed and recorded. Results: The bacterial culture of wound exudate on admission was positive in 6 patients, and 10 strains of bacteria were isolated with Staphylococcus epidermidis as the main pathogen. All the skin grafts or flaps of patients survived post surgery, with the incisions and wounds healed and all the implants preserved. After 1 to 3 years of follow-up, no recurrence of wound was found in any patient. Conclusions: The postoperative chronic wounds with exposed implants can be closed in primary stage by direct suturing or flap transplantation if it is clean enough on the basis of thorough debridement. The wounds with large defects or serious infection can be treated with continuous VSD firstly and then closed with direct suturing or skin grafting for delayed wound closure, thereby to reach the treatment goal of preserving the implants and repairing the wounds simultaneously.

A protocol of systematic review and meta-analysis of continuous vacuum sealing drainage for diabetic foot ulcer.

Background: Although continuous vacuum sealing drainage (CVSD) is often reported for the management of diabetic foot ulcer (DFU), its effectiveness has been evaluated primarily via clinical outcomes with limited attention. This study will aim to assess the effectiveness of CVSD for the treatment of patients with DFU.Methods:We will carry out a search in Cochrane Library, MEDLINE, Embase, CINAHL, PsycINFO, Web of Science, Allied and Complementary Medicine Database, Chinese Biomedical Literature Database, and China National Knowledge Infrastructure from their inceptions to the March 1, 2020. We will exert the searches in those electronic databases without restrictions of language, and the use of validated filters to obtain eligible studies. In addition to the search in electronic databases, we will retrieve studies from conference proceedings, and reference lists of included trials. We will use Cochrane risk of bias tool to assess study quality for each eligible study. All statistical analysis will be conducted using RevMan 5.3 software.Results:This study will systematically summarize the most present evidence to assess the effectiveness and safety of CVSD for the management of DFU.Conclusion:The results from this study will contribute to obtain a genuine understanding of perspective from evidence-based medicine and a scientific basis for the effectiveness and safety of CVSD for the treatment of DFU.PROSPERO registration number:PROSPERO CRD42020170723.

Unilateral or Bilateral Percutaneous Endoscopic Debridement and Lavage Treatment for Lumbar Spinal Tuberculosis

To compare the clinical outcome between bilateral percutaneous endoscopic debridement and lavage (PEDL) and unilateral PEDL treatment for lumbar spine tuberculosis (LST). A total of 40 patients with LST who underwent either bilateral PEDL (group A) or unilateral PEDL (group B) were reviewed. Perioperative parameters were assessed by operative time, intraoperative fluoroscopy times, and days of postoperative continuous irrigation and vacuum drainage. Clinical outcomes were evaluated in the Oswestry Disability Index (ODI), visual analog scale (VAS), erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP). All patients were followed-up for at least 18months after treatment. The average operative time and intraoperative fluoroscopy time were increased in group A compared with those in group B. There was no statistical significance between the 2 groups in postoperative continuous irrigation and vacuum drainage days. The ESR and CRP curves in the 2 groups showed a similar trend during 18-month follow-up. The VAS and ODI in the 2 groups significantly decreased 6 and 18 months postsurgery. There was no significant difference in the incidence of complication between the 2 groups. Two procedures yielded comparable and satisfactory results. Unilateral PEDL showed shorter operative time and decreased intraoperative fluoroscopy times compared with bilateral PEDL. We suggest the use of unilateral PEDL rather than bilateral PEDL in the treatment of LST.

A new vertical continuous vacuum pan (evaporating crystallizer) design

Crystallization is a key section of sugar manufacture for controlling the sugar quality as well as energy consumption. In this paper, i-VCP, a new vertical continuous evaporating crystallizer (vacuum pan) design is described. Unlike some other VCPs, i-VCP has a partitioned shell in the top compartments especially for low-grade massecuites, which helps to keep coefficient of variation at 25–30% and about a vapor consumption of about 28 kg/100 kg massecuite. A high vapor space avoids entrainment and efficient mechanical circulators with variable frequency drives reduce power consumption. Flexibility to use different pressure vapors in different compartments and an inbuilt seed magma crystallizing compartment obviate the demand for a separate batch apparatus. One 100t/h capacity A massecuite i-VCP installed at Dalmia Bharat Sugar Ltd. (India) and one 25t/h capacity B or C massecuite i-VCP have completed their first season without any stoppages.

Parameter space validation through OOPS simulations of plasma burnthrough and discharge evolution in the SST-1 tokamak

Plasma burnthrough and current ramp-up phases in an SST-1 superconducting tokamak are simulated by the OOPS code. The main purpose of this study is to optimize the operation regime in SST-1 through the input parameter scan for OOPS for both successful and failed shots from the SST-1 database. SST-1 is now equipped with carbon plasma facing components (PFCs). Hence, PFCs are expected to offer a carbon dominated impurity environment. An electrically continuous vacuum vessel and cryostat hinder sufficient loop voltage during start-up, thereby rendering electron cyclotron resonance heating (ECRH) pre-ionization an absolute requirement. OOPS simulation is optimized for the essential plasma initiation parameters like the seed electron density ne = 3 × 1017/m3 and the initial neutral density n0 = 1–4 × 1018/m3 (corresponding to a tailored pre-fill pressure) and for an error magnetic field Berr ≤ 20 G. The simulation shows that the ECRH pre-ionization threshold power required for the successful plasma start-up under low available loop voltage conditions is ≥180 kW.

Bench-scale dehydration of a native microalgae culture by centrifugation, flocculation and filtration in Minamisoma city, Fukushima, Japan

Fukushima, northeastern Japan, was damaged by a tsunami and nuclear incident following the March 2011 earthquake. To make effective use of non-arable lands, an examination of biofuel production from native microalgal communities was carried out in Minamisoma city, Japan. After cultivation in open-air raceway ponds, the concentration of suspended solids (SS) of microalgae culture reaches 0.03 wt%. Efficient dehydration of microalgae is, therefore, essential. This study examined a bench-scale dehydration process composed of centrifugation, flocculation and filtration. A continuous centrifuge was used for primary concentration, and 14,600 kg of algal culture was dehydrated. After centrifugation, a cationic trimethylamine-type polymer as flocculant was added to the primary concentrate, and mixed. The mixture was processed by a continuous vacuum filtration and compression, and 12.9 kg of concentrate was obtained with 82.7% recovery. Through this process, SS concentration reached a satisfactory value of 24.6 wt% with the high throughput of 5920 kg/h.

Integration of Self-Sealing Suction Cups on the FLEXotendon Glove-II Robotic Exoskeleton System

This article presents a hand exoskeleton using self-sealing suction cup modules to assist and simplify various grasping tasks. Robotic hands, grippers, and hand rehabilitation exoskeletons require complex motion planning and control algorithms to manipulate various objects, which increases system complexity. The proposed hand exoskeleton integrated with self-sealing suction cup modules provides simplified grasping with the assistance of suction. The suction cup has a self-sealing mechanism with a passive opening valve and it reduces vacuum consumption and pump noise. The gimbal mechanism allows the suction cup to have a wide range of contact angles, which increases adaptability of grasping of the exoskeleton. The fabrication process of the device is introduced with the suction cup design and material selection. The vacuum canister and solenoid valve that comprise the proposed pneumatic circuit provide a continuous vacuum supply source without continuous operation of a vacuum pump and autonomous suction/release motion, respectively. The performance of the hand exoskeleton was demonstrated with various grasping tasks and it provided stable grasping and pick-and-place task without complex finger manipulation. The proposed hand exoskeleton has the potential to simplify the grasping process and allow patients with hand dysfunction to expand their versatility of grasping tasks.

On the nature of canine aural haematoma and its treatment with continuous vacuum drainage.

To evaluate continuous vacuum drainage from the convex side of the pinna for surgical treatment of aural haematoma in dogs. To investigate aural haematoma fluid and cartilage samples harvested during surgery in an attempt to elucidate the etiopathogenesis of the lesion. Ten client-owned dogs with aural haematoma were treated by convex-side vacuum drainage using different types of vacuum drains and containers and were followed-up for at least 6 months. Systemic blood samples and aural haematoma fluids were analysed for biochemical, haematologic and electrophoretic content. Cartilage samples were examined histologically. Nine of the 10 dogs were successfully treated without recurrence at 6 months postoperatively and with excellent cosmetic results. In one case, infection required early drain removal and delayed healing was associated with wrinkling of the pinna. Fluid sample analysis suggested that "aural haematoma" contains a transudate that accumulates within a cartilage-lined cavity. Histologic examination of the tissue samples revealed clefts of the pinna cartilage, with the luminal surface often lined with granulation tissue. Fluids and cartilage lacked evidence of inflammation. This technique was characterised by patient comfort, tolerance of drains, absence of dressings and good cosmetic outcome. The results of fluid analysis suggest that the term "aural seroma" would be more appropriate for this condition.

Low surface energy nanofibrous membrane for enhanced wetting resistance in membrane distillation process

Membranes with hierarchical structure have higher water contact angle due to affording more air pockets in its nano-micro regions, and then have been known as more hydrophobic. However, the hydrophobicity could be vanished after air in pockets has been exhausted such as in the vacuum membrane distillation (VMD) process. Here, an intrinsically hydrophobic electrospun nanofiber membrane (ENM), whose hydrophobicity is entirely depended on these materials surface energy, was proposed to promote the wetting resistance without the aid of any hierarchical structure. The novel composite ENMs were fabricated using polyvinylidene fluoride (PVDF) as matrix material, and then covered it with polydimethylsiloxane (PDMS) of much lower surface energy via a facile dip-coating. Scanning electron microscope (SEM) images of nanofibers in composite ENMs showed almost no hierarchical structure was existed, while the hierarchical structure was supposed to lower water contact angle in theory. However, the composite ENMs exhibited a higher water-repellency as the surface energy of nanofibers became lower. Therefore, the composite ENMs cannot be wetted by condensed vapor throughout the MD process, and a thinner membrane exhibited an excellent durability in the continuous vacuum MD tests. The result indicated that for the ENMs material of intrinsic hydrophobicity, the low surface energy is the essential quality to exhibit the strong and durable wetting resistance in VMD process, what is difficult to achieve by conventionally hierarchical architecture constructing on membrane surface.

Parallel real-time quantum random number generator.

The quantum random number generation exploits inherent randomness of quantum mechanical processes and measurements. The real-time generation rate of quantum random numbers is usually limited by electronic bandwidth and data processing rates. Here we use a multiplexing scheme to create a fast real-time quantum random number generator based on continuous variable vacuum fluctuations. Multiple sideband frequency modes of a quantum vacuum state within a homodyne detection bandwidth are concurrently extracted as the randomness source. Parallel postprocessing of raw data from three subentropy sources is realized in one field-programmable gate array (FPGA) based on Toeplitz-hashing extractors. A cumulative generation rate of 8.25Gbps in real time is achieved. The system relies on optoelectronic components and circuits that could be integrated in a compact, economical package.

Vacuum Belt Dehydration of Chopped Beetroot (Beta vulgaris) and Optimization of Powder Production Based on Physical and Chemical Properties

Beets contain the red and yellow pigments known as betalains, as well as nitrates and other phytochemicals that may affect human health, and have been studied for possible effects on lowering blood pressure and enhancing athletic performance. Betalains are heat-labile, so developing relatively low-temperature drying methods is one way to turn the perishable root vegetable into a value-added ingredient. The objective of this study was to determine if continuous vacuum belt drying (VBD) could be used to produce powdered ingredients with good color, physical properties, and retention of betalains. Drying studies showed that drying rate could be increased somewhat by increasing temperatures from 75 to 95 °C, with drying times ranging from 160 to 115 min. Drying times were substantially shorter than for powders produced by freeze drying (FD) (26 h) or hot air drying (HAD) (~ 6 h). Properties such as flowability or color did not depend on drying temperature. VBD beet powders had a red-purplish color that was slightly darker (L* = 25.74) than for freeze-dried powders (L* = 38.92). In contrast, HAD samples were much darker than VBD or FD powders, and showed signs of browning. Flowability was improved by the addition of maltodextrins, but at the expense of some increase in drying time. VBD powders were less hygroscopic than FD powders, but reached the same final moisture content. HAD powders were less hygroscopic. VBD samples had slightly lower betalain levels (261–273 mg betanin/g dry beet) than FD powders (291.2 mg betanin/g dry beet). Both had much greater levels than HAD powders (127.8 mg betanin/g dry beet). Powder dried at 95 °C without maltodextrin was optimal as it dried most quickly and had minimal betalain loss.

Autologous platelet-rich gel and continuous vacuum sealing drainage for the treatment of patients with diabetic foot ulcer

Background:Research focusing on the efficacy of autologous platelet-rich gel (APRG) and continuous vacuum sealing drainage (CVSD) for diabetic foot ulcer (DFU) is increasing. Despite increasing knowledge on this theme, its results remain inconsistent. Thus, we will provide insight into the efficacy of APRG and CVSD for patients with DFU.Methods:We will search electronic databases of MEDILINE, EMBASE, Cochrane Library, CINAHL, AMED, Chinese Biomedical Literature Database, and China National Knowledge Infrastructure from inception to October 1, 2019. No language limitation is utilized to these databases. Two authors will independently perform study selection, data extraction, and risk of bias assessment. Disagreements between 2 authors will be solved through discussion with a third author.Results:The efficacy and safety of APRG and CVSD for patients with DFU will be assessed by the time to complete healing, proportion of ulcers healed within trial period, change of size of ulcer, health-related quality of life, patient length of hospital stay, and adverse events.Conclusion:The results of this study will provide helpful evidence of APRG and CVSD for patients with DFU.Systematic review registration:PROSPERO CRD42019153289.

Clinical effects of autologous platelet-rich plasma gel in the repair of chronic wounds

Objective: To explore the clinical application effects of autologous platelet-rich plasma gel in the repair of various chronic wounds. Methods: From January 2015 to January 2018, 76 patients with chronic wounds were admitted to our unit, with 39 men and 37 women, aged 28 to 75 (52±6) years. Before the operation, areas of wounds ranged from 2.0 cm×0.5 cm to 17.0 cm×5.0 cm, depths of wounds ranged from 1 to 6 cm, areas of wounds substrate ranged from 3 cm×3 cm to 17 cm×8 cm, and volumes of deep cavities ranged from 7 to 55 mL. All patients received operation 2 to 7 days after admission. Autologous platelet of 220-250 mL was collected from each patient by single extraction to make platelet-rich plasma of 10-50 mL. The cavity was filled completely by injection of platelet-rich plasma gel for 1-3 times. Wounds were sutured directly or covered by local flaps or other materials according to the conditions of wounds, and the unclosed wounds in primary stage were treated by continuous vacuum sealing drainage (VSD). Ultrasound, CT, or magnetic resonance imaging was performed to detect the healing of cavity after the operation. The healing of wound and repair of cavity after the operation and during follow-up were observed. Results: Wounds in 39 patients were closed directly after primary operation. Among them, wounds of 36 patients were healed completely, and wounds of the other 3 patients were healed completely after second debridement and topical filling of platelet-rich plasma gel. The cavities in 35 patients were filled with granulation tissue after treatment of platelet-rich plasma gel for 1-3 times combined with VSD, and the wounds were healed after skin grafting or flap transplantation. The treatment of wounds discontinued in the other 2 patients after treatment of platelet-rich plasma gel for once. Postoperative follow-up was lost in 7 patients. During follow-up of 2 and/or 4 months after the primary operation, wounds were healed well with no recurrence, and cavities were filled with fibrous tissue. Conclusions: Autologous platelet-rich plasma gel has advantages in treating chronic wounds, including a large amount by single extraction, flexible use mode, ability to fully fill the complex cavity, high surgical safety, and mild secondary injury. It's a new choice for repair of chronic wounds in clinic.

Freezing and drying of pink grapefruit-lycopene encapsulated in Ca(II)-alginate beads containing galactomannans.

Lycopene extracted from pink grapefruit was encapsulated on Ca(II)-alginate beads with the addition of trehalose and galactomannans to improve its stability against freezing and drying. Three galactomannans of different physicochemical properties were studied since their inclusion affects both loading efficiency and release of lycopene in wet beads; however, there is no information about their performance during freezing and dehydration operations. The remaining lycopene and its stability towards isomerization were analyzed in beads subjected to continuous freezing, freezing/thawing cycles and vacuum- and freeze-drying. Isothermal crystallization studies were conducted by LF-NMR and related to beads formulation and lycopene stability. In the absence of excipients, lycopene was severely affected by all the treatments, retaining less than 20% of the original content. Alginate beads containing trehalose with guar gum protected more than 80% of the lycopene regardless of the employed freezing or drying methods. These beads concomitantly showed higher solid fraction than the other two galactomannans-containing systems, displaying guar gum ability to associate water. On the other hand, the addition of vinal gum affected lycopene stability (between 40 and 60% were recovered after treatments), even compromising the positive effect of a well-established cryoprotectant as trehalose. Thus, the addition of secondary excipients should be carefully conducted. The differences among galactomannans could be related to the substitution degree of the polymer chains, affecting the overall systems interactions. These results can contribute to excipients selection for the encapsulation of labile biomolecules in Ca(II)-alginate beads subjected to freezing and drying.

A smart three-loop fuel cycle architecture for DEMO

In the framework of the EUROfusion Programme the EU is preparing the conceptual design of the fuel cycle for a pulsed fusion DEMO. Over the last years, a smart fuel cycle architecture has been developed, driven by the need to reduce the tritium inventory to an absolute minimum. To achieve this goal, batchwise processes used in the fusion fuel cycle so far were replaced by continuous processes wherever possible. This includes the change from discontinuous cryopumping to mercury based continuous vacuum pumping with zero demand on cryoplant power, and the introduction of temperature swing absorption processes for isotope separation in the tritium plant instead of large cryogenic distillation columns with tritiated liquid hold-ups. To circumvent handling of high inventories of tritium-bearing liquid fuel in cryogenic distillation columns of the tritium plant, superpermeable metal foils will be installed in the divertor ports of the vacuum vessel to extract pure DT continuously from the exhaust gas. Direct internal fuel recycling takes place via the pellet injection system. The paper discusses the design drivers and limitations, and describes the development status of the novel technologies.

Colloid effect on clogging mechanism of hydraulic reclamation mud improved by vacuum preloading

Many cases of artificial soft clay foundation constructed by hydraulic filling and improved by the vacuum preloading show the clogging phenomenon in the surrounding soil, which compromises the improvement quality. To clarify the clogging mechanism and the formation of soil columns, the vacuum process was tracked from macro to micro by laboratory model tests. Results show that the soil column with higher strength (density) and lower water content was formed surrounding the prefabricated vertical drainage (PVD). Mercury intrusion porosimetry (MIP) tests revealed that the pore-entrance diameter of the soil column after 50 and 43 days of vacuum application ranged from 100 to 600 nm, and that at peak it is 300 nm. However, the mean diameter of the colloidal particles in tail water decreases from 1000 to 100 nm with continuous vacuum application, and then becomes stable at about 100 nm after 43 days. After re-visiting the vacuum process of the hydraulic reclamation mud, the pore-size distribution of surrounding soils and particle-size distribution of the tail water, the clogging was explained by the filling of the pores of the soil column by the colloidal particles in pore water. This mechanism differentiates the artificial foundation improved by vacuum preloading from the natural foundation for the presence of rich colloidal particles in pore water.