5 Tons/Day Capacity | Waste Hydrochloric Acid Replacement Regeneration Line | Resource Recovery System for Hot-Dip Galvanizing Pickling Waste Acid

1. Product Overview

This treatment line is specifically designed for resource recovery of waste hydrochloric acid generated from pickling processes in the hot-dip galvanizing industry, with a processing capacity of 5 tons/day. Waste hydrochloric acid contains ferrous chloride and zinc chloride at concentrations of approximately 5-10%. Through freeze crystallization + sulfuric acid replacement processes, ferrous sulfate monohydrate byproduct is recovered and regenerated hydrochloric acid (concentration 15-22%) is reused in production – achieving zero pollution, zero emissions, full recovery, full utilization and resource recycling. Typical applications include waste acid treatment and resource recycling in hot-dip galvanizing plants and steel component pickling workshops.

2. Industry Challenges & Root Cause Analysis

High cost of outsourced waste acid treatment:Waste hydrochloric acid is hazardous waste – outsourced treatment costs approximately 600 RMB/ton, amounting to 1.8 million RMB annually for 3,000 tons. Root cause: lack of on-site resource treatment capability, only outsourcing disposal available.

Continuously increasing hydrochloric acid procurement costs:Pickling processes require continuous replenishment of new hydrochloric acid – procurement costs account for a significant proportion of operating expenses. Root cause: hydrochloric acid in waste acid is not recovered – resource waste.

High environmental risk of waste acid discharge:Waste acid storage and transportation pose leakage pollution risks – high environmental compliance pressure. Root cause: lack of zero-emission closed-loop treatment process.

Difficult byproduct disposal:If ferrous chloride and other byproducts cannot be resourced, they remain waste – increasing disposal burden. Root cause: lack of crystallization separation and resource conversion processes.

Difficult energy consumption and operating cost control:Freeze crystallization, replacement reaction, vacuum filtration and other processes consume significant energy – affecting economics. Root cause: lack of equipment intermittent operation optimization and cold energy utilization design.

3. Solution

3.1 Freeze Crystallization + Sulfuric Acid Replacement Process:Waste acid pumped through acid pump into filter – clean acid enters crystallization tank – simultaneously some concentrated hydrochloric acid added. Refrigeration unit cools and crystallizes – at crystallization temperature the tank contains solid-liquid mixture of ferrous chloride solid and regenerated acid. Solid-liquid mixture discharged into solid-liquid separator – vacuum filtration system pumps regenerated acid into storage tank – heated by heater and reused in production workshop.

3.2 Ferrous Chloride Replacement & Ferrous Sulfate Recovery:Ferrous chloride from solid-liquid separator discharged into replacement reactor – concentrated sulfuric acid added to replace and generate ferrous sulfate and hydrogen chloride gas. Ferrous sulfate undergoes thermal crystallization to form ferrous sulfate monohydrate with particle size below 0.2mm – then solid-liquid separation – ferrous sulfate monohydrate sold as resource – hydrogen chloride gas dissolved in waste hydrochloric acid to increase concentration – reused in production workshop.

3.3 Regenerated Acid Specification Control:Regenerated acid residual iron ions 4%, acid concentration 15-22%. Ferrous sulfate monohydrate byproduct quality: ferrous sulfate content ＞90%, titanium dioxide ＜0.75%, arsenic ＜0.0002%, lead ＜0.0001%, cadmium ＜0.0001%, mercury ＜0.00002%, chromium ＜0.001%, free acid (as sulfuric acid) 1%, insoluble matter ＜0.5%.

3.4 Equipment Material Anti-Corrosion Design:Heat exchanger, agitator paddles, reactors, piping and other acid-contact components use corrosion-resistant materials: heat exchanger approximately 200m long corrosion-resistant material, agitator paddle acid-resistant alloy, regenerated hydrogen chloride reactor PTFE material, concentrated sulfuric acid pump PTFE material, regenerated acid absorption tank PP material, flow meter tantalum material, level gauge acid-resistant material.

3.5 Automatic Control & Safety Protection:PLC automatic control system – automatic temperature control – 2 flow meter controllers – 2 level gauge controllers – 4 electric ball valves (DN200 acid-resistant). Vacuum unit PP material – vacuum solid-liquid separation tank manual unloading – waste acid filter PPH material.

3.6 Economic & Environmental Benefits:Annual savings of 1.8 million RMB in waste acid outsourced treatment fees (600 RMB/ton × 3,000 tons), annual revenue of 73,500 RMB from ferrous sulfate monohydrate (0.245 tons × 100 RMB/ton × 3,000 tons), annual savings of 600,000 RMB in hydrochloric acid procurement (200 RMB/ton × 3,000 tons). Annual operating costs: electricity 150,000 RMB + sulfuric acid consumption 257,400 RMB = 407,400 RMB. Annual net profit approximately 2.1546 million RMB – investment payback period approximately 3 months – hydrochloric acid procurement reduced by 80-90%.

4. Technical Specifications

5. Selection Guide

5.1 Recommended Scenarios

• Resource treatment of pickling waste hydrochloric acid in hot-dip galvanizing plants

• Zero-emission recycling of waste acid in steel component pickling workshops

• Resource recovery projects requiring hydrochloric acid recovery and ferrous sulfate byproduct

5.2 Key Selection Considerations

1. Waste acid volume matching: Verify daily waste acid volume within 5 tons/day processing capacity

2. Waste acid composition: Verify Fe²⁺＞120g/L, Fe³⁺＜5g/L, pH≤1.0, HCl concentration＞5%

3. Workshop conditions: 150-300m² workshop, 9m height, anti-corrosion and anti-seepage floor treatment

4. Utilities: User to supply 3-phase 5-wire 80kW power, tap water or purified water, waste acid storage tank (FRP 150m³)

5. Sulfuric and hydrochloric acid storage tanks: Concentrated sulfuric acid tank (iron, user determined), concentrated hydrochloric acid tank (FRP 20m³ recommended), regenerated acid tank (FRP 40m³ recommended)

6. Environmental supporting facilities: Equipment maintenance and solid unloading may generate slight acid odor – acid mist extraction hood (PP material) and exhaust fan piping required

6. FAQ

Q1: Can regenerated acid after waste acid treatment be directly reused for pickling?

A: Yes. Regenerated acid concentration 15-22%, residual iron ions 4% – heated by heater and reused in production workshop pickling process. Regenerated acid heating device includes heating tank, heater and piping – regenerated acid is cold acid and requires heating before use.

Q2: How is the ferrous sulfate monohydrate byproduct disposed of?

A: Ferrous sulfate monohydrate is sold as a resource product – can be used as wastewater treatment flocculant or other industrial uses. Equipment supplier recovers ferrous sulfate at zero cost. Byproduct quality meets requirements of ferrous sulfate content ＞90% and heavy metal content below limits.

Q3: Does the treatment process generate secondary pollution?

A: Process achieves zero pollution, zero emissions, full recovery, full utilization. Hydrogen chloride gas dissolved in waste hydrochloric acid to increase concentration for reuse – ferrous sulfate crystallized and separated as product for sale. Equipment maintenance and solid unloading may generate slight acid odor – acid mist extraction hood and exhaust piping configured.

Q4: What is the investment payback period?

A: Annual net profit approximately 2.1546 million RMB (savings of 1.8 million RMB outsourced treatment fees + 73,500 RMB ferrous sulfate revenue + 600,000 RMB hydrochloric acid savings - 150,000 RMB electricity - 257,400 RMB sulfuric acid consumption) – equipment investment 210,000 USD – investment payback period approximately 3 months.

Q5: What is the equipment energy consumption?

A: Total power 200kW, actual power consumption per ton acid approximately 40kWh. Refrigeration unit 11kW continuous operation 20 hours/day – gear motor 4kW, cooling water pump 1.5kW, chilled water pump 1.5kW continuous operation – vacuum pump 5.5kW operates once every 10 minutes – other pumps intermittent operation – most equipment operates intermittently – energy consumption controllable.