Conventional heat exchangers frequently fail when processing high-viscosity fluids, high-solids slurries, and corrosive media due to rapid fouling and blockage. The Wide Gap Welded Plate Heat Exchanger (WGPHE) has significant technical advantages such as excellent anti-clogging performance, high heat transfer efficiency, low pressure loss, corrosion resistance, and wear resistance. This paper analyzes the application of WGPHE in the aluminum, sugar, pulp and paper, and chemical wastewater treatment industries, explaining how the wide-channel structure serves as a core support for ensuring process continuity and heat transfer efficiency.

1. Alumina Industry: Addressing Erosion and Scaling in the Bayer Process

Alumina production is the cornerstone of modern metallurgical industry, and its mainstream process — the Bayer Process — is a complex chemical process involving high temperature, high pressure, strong alkali, and a large number of suspended solid particles. Among them, the precipitation process (Precipitation) is the core link determining product quality and output, and it is also one of the areas with the most severe challenges in the operation and maintenance of heat exchange equipment.

1.1 Process Characteristics of the Precipitation Stage

In the precipitation tanks, diluted sodium aluminate liquor is required to precipitate gibbsite crystals under controlled temperature. This process is accompanied by significant heat release and demands precise temperature control to regulate the crystal growth rate.

Scaling:Sodium aluminate liquor is in a supersaturated metastable state. When the fluid velocity near the heat transfer surface decreases (forming dead zones) or the temperature difference is excessive, sodium aluminate and sodium silicate spontaneously nucleate on the wall and grow into hard scaling. This scaling layer has extremely low thermal conductivity, which not only severely hinders heat transfer but also continues to thicken, eventually blocking the flow channels.

Erosion:To suppress scaling and particle sedimentation, the slurry must maintain a relatively high flow velocity. However, the slurry suspends high-hardness aluminum hydroxide seed crystals and bauxite residue. In traditional heat exchangers, the high-speed solid-liquid two-phase flow acts like “liquid sandblasting”, continuously scouring and impacting the inlet, bends and plate contact areas of the heat transfer channels, resulting in rapid wall thickness reduction and even perforation and leakage of the equipment.

1.2 Solution by SHPHE

In view of the above characteristics, Shanghai Heat Transfer Equipment Co., Ltd. (SHPHE) has developed dedicated WGPHE for precipitation slurry based on research in multiphase fluid mechanics.

1.2.1 Structural Advantages of Vertical Wide‑Gap Plate Heat Exchanger

• The slurry flows vertically, using its own kinetic energy and buoyancy to keep solid particles suspended, forming homogeneous flow.
• The plates are located on both sides of the vertical channels, which reduces the accumulation of solid phase in the lower corrugations of the plates and makes scaling less likely.
• Combined with an alkali boiling cleaning system, it reduces the frequency of disassembly and cleaning of the heat exchanger.

1.2.2 Structural Advantages of Horizontal Wide-Gap Plate Heat Exchanger

• Precise flow velocity control ensures that the bottom velocity is higher than the critical suspension velocity.
• Improved plate corrugation design not only promotes turbulence formation at the fluid bottom but also reduces stagnant zones on the plates.
• Easy disassembly, cleaning and maintenance.

1.2.3 Unique Inlet Distributor Design

To address inlet erosion issues, SHPHE has developed a unique fluid distributor at the slurry inlet.

• Energy Dissipation & Flow RectificationThis device buffers the high-speed jet from the feed pipe, eliminating local vortices and high-pressure zones.
• Uniform DistributionIt ensures uniform flow rate and velocity across every channel along the width of the plate pack when slurry enters, preventing the coexistence of local high-speed erosion and local low-speed scaling caused by uneven flow distribution.

1.2.4 Application Case

In a technical renovation project of a large‑scale alumina plant, the original shell‑and‑tube coolers required shutdown for high‑pressure water cleaning every 2–3 weeks, and the service life of the tube bundles was less than one year.After being replaced with SHPHE’s wide‑gap precipitation slurry cooler, the cleaning cycle was extended to 3–6 months, greatly reducing downtime and the generation of cleaning waste liquid.Due to the significantly reduced scaling rate, the average heat transfer coefficient (K‑value) of the equipment remained high during the operation cycle, resulting in more precise temperature control of the precipitation tanks and directly improving the particle size distribution quality of the alumina product.

Operational Performance Comparison: WGPHE vs. Tubular Exchangers

2. Sugar and Fermentation Industry: Handling High Viscosity and Biomass Fibers

Biomass processing presents a dual challenge: biological fibers that clog contact points and viscosity that escalate exponentially during concentration.

2.1 Sugar Industry: Challenges from Bagacillo and High-Viscosity Syrups

In the cane sugar production process, the squeezed mixed juice contains a large amount of bagacillo, which can cause:

• Fiber Fouling / Fiber Hang-Up:The corrugated contact points of conventional plate heat exchangers act as “fiber traps”. Once fibers are caught, they accumulate rapidly and form a dense fiber mat, blocking fluid flow.
• High-Viscosity Laminar Flow:As sugar juice is concentrated into syrup or molasses in multi-effect evaporators, its viscosity can reach thousands of centipoises. In tubular heat exchangers, such high-viscosity fluids tend to form laminar flow, creating an extremely thick thermal boundary layer near the tube wall and significantly reducing heat transfer efficiency.

Solutions by SHPHE

• “S” Type Unobstructed Flow Channel:The WGPHE by SHPHE features a special plate design with a smooth, wave-like channel cross-section, free of sharp protrusions and dead zones. The extra-wide gap of 20–30 mm allows long fibers to pass through smoothly.
• Low-Reynolds-Number Turbulence:The fish-scale pattern on the plate surface generates secondary flows such as Dean Vortices in syrup even at a low velocity of only 0.2–0.3 m/s. Such intense fluid mixing enhances heat transfer and prevents sugar caramelization caused by local overheating.
• Waste Heat Cascade Utilization:Thanks to high thermal efficiency, SHPHE equipment can use low-temperature waste vapor (only 60–70°C) from the end-effect evaporator to preheat raw juice, fully recovering waste heat that would otherwise be discharged and significantly reducing fresh steam consumption.

2.2 Fuel Ethanol: Mash Cooling and Bio-fouling

Ethanol fermentation mash is a complex slurry containing grain residues, yeast cells, proteins, and unfermented starch.

• Bio-foulingOrganic matter easily forms biofilms on heat transfer surfaces at suitable temperatures. This film has extremely high thermal resistance, is very difficult to clean, and even causes corrosion to stainless steel.
• Non-Newtonian Fluid CharacteristicsMash typically behaves as a shear-thinning fluid. In conventional equipment, uneven velocity distribution leads to excessive local viscosity and stagnation, forming “dead zones”.

Solutions by SHPHE

• No Dead Zones for Cleaning: The all-welded construction provides smooth internal surfaces. High-velocity acid and alkali cleaning fluids from the Clean-in-Place (CIP) system can scour all surfaces without dead zones, completely removing biofilms and preventing bacterial growth.
• Rheological Optimization: The channel design is modified for non-Newtonian fluids to ensure uniform shear rate distribution inside the flow channels, avoiding local high-viscosity zones and guaranteeing uniform cooling of the mash.

3. Pulp and Paper Industry: Heat Recovery from White Water

The paper industry is typically energy-intensive and water-intensive. The key to reducing energy consumption per ton of paper lies in heat recovery from white water and black liquor generated during production.

3.1 Paper Machine White Water: A Mixture of Fibers and Fillers

White water is discharged from the wire section of the paper machine, containing fine cellulose fibers, fillers, and chemical additives.Conventional heat exchangers are highly prone to fiber deposition and fouling, so paper mills usually dare not recover the low-grade heat (45–55°C) from white water.

3.2 Solution by SHPHE

The pillow plate heat exchanger is formed by laser welding two metal sheets followed by hydroforming, creating regular “pillow-like” protrusions on the surface with periodically expanding and contracting flow cross-sections.As fluid passes through the variable cross-section channels, its velocity changes periodically, generating local acceleration and deceleration, resulting in a self-turbulent flow effect.The wide-channel structure provides unobstructed physical space for fibers, while the velocity fluctuations and turbulent mixing caused by the variable cross-section keep fibers suspended and tumbling at all times, making adhesion and deposition nearly impossible.

3.3 Application Case

In a large-scale paper mill, SHPHE’s pillow plate heat exchangers are installed at the outlet of the white water tank to directly recover heat from white water for heating clean water.The equipment has been operating continuously for one year without blockage, successfully achieving waste heat recovery.

4. Environmental Engineering Applications

Chemical wastewater (e.g., from pesticides, dyes, and pharmaceuticals) is typically characterized by high salinity (TDS), high COD (Chemical Oxygen Demand), and strong corrosivity.

• Anti-Crystallization & Anti-Sedimentation: Crystalline salts tend to precipitate during evaporation and concentration of high-salinity wastewater.The wide channels of the WGPHE allow crystal particles to pass through, while high-flow scouring prevents channel blockage. For oily sludge-containing wastewater, the wide gap avoids bridging and accumulation of sludge.
• Economic Efficiency: Compared with graphite heat exchangers or special-material shell-and-tube exchangers, the WGPHE has a higher heat transfer coefficient and requires less heat transfer area.Therefore, when using Hastelloy (C‑276) or titanium‑palladium alloy, the overall material cost is lower and the cost performance is higher.

Comparative Analysis