Membrane filtration
| Technology | |
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| Technology details | |
| Name: | Membrane filtration |
| Category: | Separation process |
| Feedstock: | all materials |
| Product: | separated products |
Membrane filtration as a separation technology covers all engineering approaches for the transport of substances between two fractions with the help of permeable membranes.
Feedstock
Origin and composition
In membrane separation processes, the membrane acts as a selective barrier between two phases with the ability to facilitate or limit the transport of one or more components from one phase to another by the action of a driving force. This driving force can be pressure, concentration, electrical potential, or temperature gradient. The stream passing through the membrane is the permeate, whereas the stream containing the rejected components is the retentate. The most common applications in biotechnology are the separation of solid biomass from feedstocks, separation of production cells within a pre-treatment or a downstream process and separation of target dissolved substances from liquid streams.
Pre-treatment
For a membrane filtration in general no specific pre-treatment is needed since it is used to separate different fraction within a process chain. Sometimes it is combined with other separation technologies such as centrifugation.
Process and technologies
Membrane separation processes differ based on driving force and size of the separated particles. Pressure driven processes include microfiltration, ultrafiltration, nanofiltration and reverse osmosis. Other driving forces such as electrical potential, concentration gradient or vapor/pressure gradient include electrolysis, dialysis, electrodialysis, gas separation, vapor permeation, pervaporation, membrane distillation, and membrane contactors. All processes except for pervaporation involve no phase change. Microfiltration and ultrafiltration is widely used in food and beverage processing, biotechnological applications and pharmaceutical industry, water purification and wastewater treatment, the microelectronics industry, and others. Nanofiltration and reverse osmosis membranes are mainly used for water purification purposes.
Membrane filtration can be carried out by means of two operating modes: dead-end filtration and cross-flow filtration. In dead-end filtration, the feed stream flows perpendicular to the membrane and is forced through the membrane. In consequence, the retained components accumulate on the membrane surface forming a cake layer, resulting in a decrease of the filtration rate due to the additional resistance to filtration of this cake layer. Dead-end operation mode is mostly employed in MF and is commonly used for separation of solid biomass from different feedstocks withing pre-treatment process. In cross-flow filtration (CFF), the feed flows parallel to the membrane surface. The tangential flow allows drag of the accumulated rejected solutes on the surface of the membrane, limiting the thickness of the cake layer and helping to maintain the permeate flow. CFF is widely used for concentration, purification or fractionation of target compounds from liquid streams.
The membrane module is also a key parameter in the performance of a membrane separation process. The modules are designed with the objective of increasing turbulence on the surface of the membrane to reduce the mass transfer resistance and the concentration effects. The most used modules are plate and frame, spiral, tubular and hollow fibres.
Products
The products of a membrane filtration are the compounds retained by the membrane and the permeate stream that can be further processed.
Post-treatment
The post-treatment of the filtrate is depending on the next steps within the production chain.
Technology providers
ABC
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| Technology and process details | |||
| Technology name: | Technology category: | Pre-processing (Separation technologies), Post-processing (Separation technologies) | |
| TRL: | Capacity: | kg·h-1 | |
| Filter material: | Hydrophobicity: | ||
| Molecular cut-off: | kDa | pH: | |
| Pore size: | µm | Pressure: | bar |
| Processable volume: | L | Surface area: | m2 |
| Temperature: | °C | Other: | |
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| Feedstock: | Product: | ||
describe the company, here is an example
ABC was founded in 20... 12 by KNN and Syncom, in collaboration with the university of Groningen, Netherlands. The company is a technology provider developing chemical recycling technologies for different feedstocks including non-food bio- and plastics waste. In 2018 a pilot plant with the capability to process biomass and plastic waste was set up at the Zernike Advanced Processing (ZAP) Facility. The company is now focused on setting up their first commercial plant with a capacity of 20,000 to 30,000 tonnes. The investing phase B was recently completed, with the last investment phase in 2019 the financial requirements are fulfilled to complete the commercialisation activities to build the plant which is expected for 2023.
describe their technology, here is an example
The technology is based on an Integrated Cascading Catalytic Pyrolysis (ICCP) process, being able to produce aromatics including benzene, toluene, and xylene (BTX) as well as light olefins from low grade biomass and plastics waste. This technology utilises catalytic cracking in a two-step process at temperatures between 450- 850 °C. In the first step the feedstock material is vaporised via thermal cracking. The pyrolysis vapours are then directly passed into a second reactor in which they are converted into aromatics by utilising a zeolite catalyst which can be continuously regenerated. Finally, the products are separated from the gas via condensation. An ex situ approach of catalytic conversion has several advantages such as the protection of the catalyst from deactivation/degradation expanding its lifetime, a greater variety of feedstock, and a precise adjustment of process conditions (e.g. temperature, catalyst design, and Weight Hourly Space Velocity (WHSV) in each step for improved yields. In current pilot plant with 10 kg h-1 feed capacity for either waste plastics or biomass, final design details are established, which will be include in the running engineering activities for the commercial plant.
Berrytec GmbH
Sartorius AG
Open access pilot and demo facility providers
Patents
Currently no patents have been identified.
References and further readings
- Membrane filtration in Wikipedia