Introduction to SDN Environmental‑Protection Filter Materials and Filter Elements

SDN Metallic Membrane Filter Elements

Metallic Membrane Materials

1. The membrane material is prepared by the Kirkendall effect induced by elemental partial‑diffusion.
2. It addresses global technical bottlenecks of material selection for high‑temperature gas filtration.
3. Adopting atomic‑scale partial‑diffusion reaction synthesis technology, it enables precise regulation of pore structures at micron and sub‑micron levels. The material delivers excellent filtration performance including uniform pore‑size distribution, high filtration accuracy, high open porosity, low tortuosity factor and low filtration resistance.
4. Its unique mixed‑bond crystal form combining metallic bonds and covalent bonds integrates merits of both metals and ceramics. It features outstanding chemical stability, thermal stability, mechanical‑physical properties, machinability, thermal conductivity and electrical conductivity.
5. The material is manufactured via eco‑friendly processes. It is environmentally benign throughout its full life cycle, recyclable and cost‑effective.

Material Characteristics

1. Presented in thin sheets with thickness of 0.5‑0.8 mm, flexible and roll‑formable.
2. High open porosity, uniform pore size and smooth pore channels.
3. Excellent machinability.
4. Asymmetric pore structure.

 Features of Flexible Metallic Membranes

Metallic membranes can be made into flexible, semi‑rigid and rigid types. Flexible membranes are the most widely‑used variant with the following properties:

- High‑temperature resistance: up to 400 °C (no bag burnout risk)
- Corrosion resistance: resistant to H₂S, SO₂, SO₃ and other corrosive media
- High filtration accuracy: 0.1 μm; membrane pore size 10 μm; outlet dust concentration can reach ＜5 mg/Nm³
- High flux: above 1.5 times the flux of conventional filter bags per unit area
- Low resistance: about 300 Pa lower pressure drop than filter bags for the same gas volume, bringing around 10 % power‑saving
- Smooth surface: facilitates pulse‑jet ash cleaning (filter bags tend to accumulate dust)
- Long service life: durable under normal operation; service life is 1‑2 years longer than premium filter bags

SDN Silicon Carbide (SiC) Membrane Technology

 Properties of Silicon Carbide Ceramic Membrane Materials

- Structure: Silicon carbide, also known as carborundum or moissanite, has two basic grades: black SiC and green SiC. Its crystal forms include hexagonal/rhombohedral α‑SiC and cubic β‑SiC.
- Performance: Chemically stable, barely etched by any solvent below 1500 °C. It boasts high thermal conductivity, low thermal expansion coefficient, strong hydrophilicity and superior wear resistance. With a Mohs hardness of 9.5, it is second only to diamond (Mohs 10).

Multi‑Channel Tubular Silicon Carbide Ceramic Membrane

The support layer, transition layer and separation layer are all fabricated from high‑purity silicon carbide (>99.5 %) without any sintering additives, thus inheriting nearly all intrinsic properties of SiC.

 Membrane Structure

The support layer, transition layer and separation layer are sintered layer‑by‑layer under matched firing regimes. Neck‑joints are formed between SiC particles of each layer to guarantee membrane strength, pore‑size precision and high porosity.

 Technical Advantages of SiC Membranes

SDN holds domestically leading complete technologies for high‑performance SiC ceramic membranes, including slurry preparation & coating, grain morphology control, local sintering and pore‑size tuning. The reaction‑recrystallization composite sintering process for SiC ceramic membranes yields stable and consistent microfiltration / ultrafiltration membrane products.

 Separation Advantages of SiC Ceramic Membranes

1. Stable separation & retention performance: narrow and stable pore‑size distribution. Membrane structure and pore dimension remain intact under high pressure or pulse pressure.
2. High separation efficiency and large flux: produced by high‑temperature recrystallization sintering with smooth rounded particle edges. Membrane pores and channels are well interconnected with no closed pores, bringing low flow resistance and higher flux compared with other inorganic membranes.
3. Physical demulsification for efficient oil‑water separation: hydrophilic‑oleophobic surface delivers favorable oil‑water separation capacity.
4. Physical separation with strong anti‑fouling performance for reliable separation quality. Membrane and auxiliary materials are non‑polluting; no chemical additives are introduced during filtration to avoid secondary contamination.
5. Fouled membranes can be thoroughly cleaned to restore original flux.
6. Compact equipment footprint, low energy consumption and low operating cost. It supports automatic control and unattended operation.

 SDN S31603 Stainless Steel Fiber Felt

 S31603 Fiber Felt Features

1. High‑temperature resistance: outstanding heat‑resistance, corrosion‑resistance and filtration performance.
2. Corrosion resistance: unique 3D porous architecture built by multi‑layers with graded pore sizes. It provides high porosity, large specific surface area, uniform pore‑size distribution, high dust‑holding capacity and high filtration precision.
3. High accuracy: effectively overcomes easy‑clogging and easy‑damage drawbacks of metal mesh, as well as brittleness and low flow rate limitations of powder‑based filter products. It delivers superior temperature‑resistance and pressure‑resistance compared with ordinary filter paper and filter cloth.

 S31603 Fiber Filter Bags

Cylindrical filter elements manufactured by high‑precision welding with stainless‑steel fiber felt as raw material.

Performance

1. High temperature resistance, corrosion resistance and high mechanical strength.
2. Good air permeability, low initial pressure drop and high separation efficiency; outlet emission can be lower than 5 mg/m³.
3. Available for on‑line back‑blowing and off‑line cleaning, favorable regeneration performance and long service life.
4. Easy‑to‑recycle, preventing secondary environmental pollution.

Specifications

- Outer Diameter D: 10 mm ~ 160 mm
- Length L: 50 mm ~ 6000 mm
- Filtration accuracy: ≥ 0.5 μm

Application: High‑temperature flue‑gas dedusting for steel, chemical, power, new‑energy and other industries.

SDN Non‑metallic Ceramic Fiber Filter Tubes

 Material Characteristics

1. Porosity: 65‑85 %; low density: 0.4 g/cm³; anti‑seismic performance, resistant to fracture caused by thermal expansion & contraction.
2. Filtration efficiency originates from ultra‑fine ceramic fibers (d=2‑3 μm).
3. Ceramic fibers are chemically inert against most reagents.
4. High‑temperature resistance.
5. Rigid mechanical property.
6. Self‑supporting monolithic cylindrical structure with no frame required. Main constituents: aluminosilicate fibers and inorganic binders.

 Five Core Advantages of Ceramic Fiber Filter Tubes

1. Replacement for conventional filter bags: identical installation and high‑pressure pulse‑jet cleaning mode as traditional baghouse filters.
2. Superior high‑temperature and corrosion resistance compared with conventional filter bags.
3. Longer service life than traditional filter bags.
4. Integrated ultra‑low‑emission solution: integrated dedusting‑denitrification system with simple operation and low cost, fully complying with national environmental‑protection emission standards.
5. Waste‑heat recovery capability: dedusting and denitrification are completed at high temperature. Clean hot flue gas can be further utilized for sensible‑heat and latent‑heat recovery.

Catalyst‑Loaded Ceramic Fiber Filter Tubes

Target pollutants: flue‑gas dust, desulfurization‑generated dust and nitrogen oxides (NOₓ).

1. Apart from dust filtration, reactive additives can be incorporated: alkaline agents for removing acid gases (SO₂, HCl, HF); ammonia / urea for NOₓ abatement.
2. Catalyst‑loaded ceramic fiber filter tubes integrate catalysts inside the filter substrate to accelerate catalytic NOₓ removal reactions.
3. Common catalysts and their optimal operating temperature ranges:
- M‑01 V‑Ti‑W based catalyst: optimal 270‑400 °C, max. 420 °C
- M‑02 V‑Ti based catalyst: optimal 250‑330 °C, max. 350 °C
- L‑01 Mn‑Fe based catalyst: optimal 150‑225 °C, max. 250 °C