Ceramic Filter Press Feed Valves for Carbide Slag Slurry

Carbide slag slurry filtration process showing acetylene recovery, the filter press and filtrate recycling

KOWOV ceramic valves are used at filter press feed inlets handling carbide slag slurry in salt chemical plants. This application overview focuses on abrasive wear, scaling and valve sticking, and presents a ceramic C-type valve trial at the slurry inlet. The reported valve sizes in the case are DN65, DN80 and DN200

Calcium Carbide Slurry Filter Press

In chlor-alkali plants, filter press systems dewater calcium carbide slurry into filter cake for easier storage and transportation. The slurry contains hard solid particles and calcium hydroxide, which may form calcium carbonate scale when exposed to carbon dioxide

The combined effects of particle erosion, crystallization and scale buildup can cause conventional metal valves to wear, seize or become blocked. This results in internal leakage, unstable operation, frequent maintenance and interruptions to normal production

Typical Failures of Conventional Metal Valves

Severe internal wear, component deformation, scale buildup and flow-path blockage

Operating Conditions

The filter press inlet valve conveys residual calcium carbide slurry from the acetylene generation process into the filter press for dewatering and filter-cake formation. Hard suspended solids cause severe abrasive wear, while crystallization and scale buildup occur on valve internals and pipe walls. Conventional valves are therefore prone to internal leakage, seizure and blockage, disrupting normal production

Item	Value	Design Parameter	Specification
Medium	Calcium carbide slurry	Phase	Liquid-solid slurry
Operating Pressure	≤0.7 MPa(g)	Nominal Pressure	PN16 / PN25
Differential Pressure	≤0.2 MPa	Nominal Diameter	DN65-DN200
Temperature	<100°C	Thermal Condition	No significant thermal shock
Key Characteristics	Abrasive solids and scale-forming tendency	-	Wear, scaling and blockage

Medium Details

Parameter	Description
Chemical Composition	Primarily calcium hydroxide, calcium carbonate and calcium-containing suspended solids
Corrosive Species	Trace chloride ions (Cl⁻)
pH	8-10*
Solids Content	To be confirmed
Particle Size	To be confirmed
Particle Hardness	To be confirmed

Operating Challenges

Key Characteristics of the Operating Conditions

Mild Chemical Corrosion

The slurry contains trace chloride ions and is mildly corrosive. Duplex stainless steel 2205 generally provides adequate corrosion resistance under these conditions, subject to verification of the actual chloride concentration, pH and operating temperature

Severe Abrasive Wear

The medium has a high solids content and may contain calcium carbide residue, iron particles and other hard contaminants. Continuous scouring rapidly damages conventional metal sealing surfaces, resulting in internal leakage and loss of shutoff performance

High Solids Loading and Deposit Buildup

The high-solids slurry tends to settle and accumulate in valve cavities and low-flow areas. Deposits increase operating torque, restrict the flow passage and may eventually prevent the valve from opening or closing

Crystallization and Scaling

Calcium hydroxide in the slurry reacts with dissolved or entrained carbon dioxide to form calcium carbonate deposits. These deposits adhere to valve internals and pipe walls, causing scaling, seizure and pipeline blockage

Equipment and Operational Risks

Abrasive wear of sealing surfaces causes internal leakage and increases maintenance and replacement costs
Scaling and hardened deposits can jam valves and block pipelines
Manual dismantling and cleaning require substantial labor and maintenance time
Valve failure can interrupt filter-press operation and destabilize upstream slurry handling

Keywords: Chlor-Alkali Industry · Filter Press · Calcium Carbide Slurry · Crystallization and Scaling · Ceramic Ball Valve · Ceramic C-Segment Ball Valve · FCRV6 · FCCV6

Process Pain Points and Opportunities

Existing Valve Materials and Designs

Conventional installations mainly use hardened metal-seated ball valves and hemispherical or segment-type valves. Typical surface treatments include tungsten carbide and Stellite hardfacing

Problems with Conventional Valves

Continuous slurry erosion damages the sealing surfaces and causes internal leakage. Calcium carbonate crystallization and scaling accumulate inside the valve cavity, increasing operating torque and eventually causing the valve to seize

Replacement Cycle and Service Life

Under severe operating conditions, conventional metal valves may develop internal leakage or become blocked within approximately 3-6 months, requiring frequent repair or replacement

Losses from Shutdown and Maintenance

Interruption of filter-press operation and reduced production throughput
Time required for isolation, drainage, dismantling and pipeline flushing
Increased spare-parts, labor and cleaning costs
Unstable slurry feed and reduced filtration efficiency
Additional safety risks caused by frequent manual maintenance
Disruption to upstream acetylene production and slurry-recovery operations

Case Study

Calcium Carbide Slurry Filter Press Inlet Valves

Selected End Users

Tangshan Sanyou Chlor-Alkali Co., Ltd., since 2017
Xinjiang Zhongtai Chemical Co., Ltd., since 2018
CNSG Jilantai Chlor-Alkali Chemical Co., Ltd., since 2019
Inner Mongolia Junzheng Chemical Co., Ltd., since 2020
Inner Mongolia Elion Chemical Industry Co., Ltd., since 2020
Baotou Haipingmian High Polymer Industry Co., Ltd., since 2020

Filter press installations across the chlor-alkali industry face similar valve problems. Hard solids cause severe erosion and wear, while calcium carbonate crystallization and scaling lead to blockage and valve seizure. Conventional metal valves consequently suffer from internal and external leakage and require frequent removal, cleaning and maintenance. This increases operator workload and disrupts stable production

At one chlor-alkali plant, pneumatically actuated conventional metal-seated valves in DN65, DN80 and DN200 were installed on the calcium carbide slurry inlet lines of the filter press. Although the valves were designed for remote operation, continuous slurry erosion and scale buildup caused leakage and seizure. Routine cleaning was required frequently, while major removal, repair or replacement was typically necessary every 3-6 months. Once seized, the valves could no longer respond to remote operating commands, defeating the purpose of automated control

To solve the problem, the plant installed KOWOV Ceramic C-Segment Ball Valves. Since commissioning, no valve-sticking failures have been reported. Inspection found no significant scale accumulation or other abnormalities on the ceramic flow-path surfaces. Following the successful trial, the customer began replacing conventional metal valves on additional filter press lines

Valve Performance Comparison

No.	Item	Conventional Metal Valve	KOWOV Ceramic C-Segment Ball Valve
1	Valve Design	Cam-Flex / eccentric rotary design*	C-segment ball valve
2	Key Wetted Materials	Carbon steel / stainless steel	Structural ceramic
3	Shutoff Class	Class IV	Class IV
4	Cleaning Interval	Sticking after approximately two weeks; cleaning required monthly	Normal operation after three months, with no sticking
5	Cleaning Time	Approximately two hours per event	No cleaning required during the reference period
6	Inspection Result	Severe scale accumulation	No significant scale accumulation observed

Demonstrated Service Life: ≥3 Years

Scale deposits inside valves shown in the carbide slag filter press application

Why Choose Ceramic Valves?

Superior Abrasion and Erosion Resistance

Structural ceramics have a Rockwell hardness of HRA 87 or higher, substantially exceeding that of conventional metal alloys and PTFE-lined components. They withstand continuous impact and scouring from hard particles in calcium carbide slurry, reducing internal wear, leakage and valve replacement frequency

Excellent Corrosion Resistance

Structural ceramics are inorganic, non-metallic materials with excellent chemical stability. Under applicable operating conditions, they resist corrosion from alkaline slurry, chloride-containing media and many acidic or alkaline process fluids commonly encountered in the chlor-alkali industry

Smooth Surface and Low Adhesion

Precision-ground ceramic surfaces have very low roughness and low material adhesion, helping to minimize calcium carbonate scaling and solids buildup. The high-hardness ceramic flow path also withstands continuous slurry erosion, ensuring smoother operation and more accurate flow control

Stable Sealing and Process Control

The combination of high mechanical strength, smooth ceramic surfaces and precision-lapped sealing components reduces scaling, wear and internal leakage. Ceramic ball valves and ceramic C-segment ball valves therefore provide more stable control, fewer maintenance interventions and improved batch-to-batch process consistency

Conclusion: Ceramic ball valves and ceramic C-segment ball valves provide a reliable solution for long-term operation in calcium carbide slurry systems, significantly reducing valve sticking, leakage and unplanned maintenance