Case Study of Fiber Demister Retrofitting in Chlorine Drying System of a Large Domestic Chlor-Alkali Chemical Enterprise

Project Location: Binzhou, Shandong Province; Project Time: March 2025; Application Location: Acid mist collector retrofit at the outlet of the chlorine drying tower of a 300,000-ton/year ion-exchange membrane caustic soda plant; Product: Filtearth upgraded fiber bed demister (same size replacement).

I. Customer Background and Existing Problems

This company is a large-scale chlor-alkali production base in China, with a 300,000-ton/year ion-exchange membrane caustic soda production unit. The existing chlorine drying system used a domestically produced ordinary fiber demister, which had experienced frequent problems after two years of operation, seriously affecting production stability:

Excessive acid mist and severe equipment corrosion.

1. The acid mist content at the export site reached as high as 120 mg/Nm³, far exceeding the industry standard of ≤10 mg/Nm³.

2. Acid corrosion frequently occurred in downstream chlorine compressor impellers, liquefier coils, liquid chlorine storage tanks, and valves.

3. Valves needed to be replaced on average every 6 months, resulting in annual production losses exceeding 800,000 yuan due to equipment corrosion.

Rolled wire mesh under a tarp in an outdoor setting. Fiber bed mist eliminator

Metal mesh cylinder with insulation material scattered around, placed outdoors near grassy terrain. Fiber bed mist eliminator

High Pressure Drop, High Energy Consumption

1. Pressure drop reaches 1800Pa in the initial operation phase, rising to over 2500Pa after 6 months of operation.

2. Chlorine compressor current consistently exceeds limits, increasing power consumption by 12kWh per ton of chlorine.

3. System processing capacity is limited, unable to operate at full capacity.

2. Rapid Filter Cartridge Clogging, High Maintenance Costs

1. Sodium sulfate crystals and salt spray rapidly deposit on the filter cartridge surface.

2. Filter cartridges must be replaced entirely every 8-10 months.

3. Each replacement requires a 3-day shutdown, impacting production capacity by approximately 2500 tons.

3. High Chlorine Moisture Content, Decreased Product Quality

4.

1. Chlorine moisture content exceeds 600ppm.

2. Unstable purity of liquid chlorine products affects the quality of downstream PVC production.

3. Increased consumption of concentrated sulfuric acid, consuming 22kg of acid per ton of chlorine.

II. Felfilt Solution

Addressing customer pain points, we offer **"Direct Replacement of Same Size + Structural Upgrade"** The overall solution requires no modification to existing towers and piping, with a modification cycle of only 2 days:

1. Product Configuration

✅Product Model: FLT-FB-3200 Fiber Bed Demister

✅Filter Media Material: Imported Special Glass Fiber (Customized for Chlor-Alkali Applications)

✅Frame Material: 470 Resin (Reinforced)

✅Sealing Material: Elastic PTFE Tape (Resistant to Concentrated Sulfuric Acid and Wet Chlorine Corrosion)

✅Filtration Area: 28% Increased Compared to Original Equipment (for the Same Tower Diameter)

✅Design Parameters: Gas Processing Capacity 35000 Nm³/h, Operating Gas Velocity 0.6 m/s, Filtration Accuracy 3μm 100%, 1μm 99%

2. Technical Upgrade Highlights

✅Gradient Filtration Structure: Three-layer fiber arrangement from coarse to fine effectively intercepts salt spray and sodium sulfate crystals, extending the clogging cycle.

✅Low-Resistance Flow Channel Design: Optimized gas distributor and fiber bed structure significantly reduces operating pressure drop.

✅Anti-Secondary Entrainment Design: Increased high-efficiency liquid trapping layer prevents captured acid mist from being carried away by the airflow again.

✅Reinforced Frame: Thickened 470 resin mesh cage, increasing deformation resistance by 50% and extending service life.

III. Retrofit Implementation Process

1. Preliminary Preparation: On-site measurement of tower dimensions, customized production of demisters based on customer process parameters.

2. Shutdown Retrofit: Utilizing the annual maintenance window, remove the old demister and install the new equipment.

3. Installation and Commissioning: Professional technicians provide on-site installation guidance, conduct airtightness tests and no-load trial runs.

4. Performance Testing: After load operation, on-site testing of key indicators such as demister efficiency, pressure drop, and chlorine moisture content.

5. Personnel Training: Training on equipment use and daily maintenance for customer operation and maintenance personnel.

IV. Comparison of Effects and Data After the Upgrade

Since its commissioning in April 2025, the equipment has been operating stably, with all indicators meeting or exceeding expectations:

Table

Indicator Item	Before renovation	After renovation	Improvement effect
Export acid mist content	120mg/Nm³	≤8mg/Nm³	Reduced by 93%
Chlorine moisture content	600ppm	≤120ppm	Reduced by 80%
Operating pressure drop	1800-2500Pa	650-900Pa	Reduced by more than 65%
Electricity consumption per ton of chlorine gas	215kWh	201kWh	Reduced by 6.5%
Consumption per ton of chlorine gas and concentrated sulfuric acid	22kg	16kg	Reduced by 27%
Filter replacement cycle	8-10 months	Expected to be more than 3 years	Extended by more than 3 times
Equipment cleaning cycle	3 months	12 months	Extended by 4 times
System processing capacity	85% load	110% load	promote 29%

V. Customer Economic Benefit Analysis

Based on a caustic soda production capacity of 300,000 tons/year, the direct economic benefits after the upgrade are as follows:

1. Energy savings: 300,000 tons × 14 kWh/ton × 0.6 yuan/kWh = 252,000 yuan/year

2. Sulfuric acid savings: 300,000 tons × 6 kg/ton × 0.8 yuan/kg = 144,000 yuan/year

3. Maintenance cost savings: Filter replacement cost + labor cost + downtime loss = 1,200,000 yuan/year

4. Capacity increase benefit: 300,000 tons × 25% × 200 yuan/ton = 1,500,000 yuan/year

Total annual economic benefit: Approximately 3,096,000 yuan; Investment payback period: Approximately 4.5 years

VI. Customer Testimonials

Filtearth fiber demisters completely solved our long-standing problems of excessive acid mist and high pressure drop. What surprised us most was that, without changing the original tower dimensions, not only was the demister effect significantly improved, but the system's processing capacity also increased by nearly 30%. In the year since the equipment started operating, the pressure drop has remained stable at around 700 Pa, with no signs of blockage. We have decided to replace all the remaining three demisters in our plant with Filtearth products.