Tank Cleaning Odor and Waste Water Abatement Process
Executive Summary
Epcon provided a turnkey integrated system for a tank-cleaning facility to eliminate odorous emissions and reduce wastewater disposal costs. By combining a thermal oxidizer, waste-water/sludge feed, vapor dilution & ducting, and a waste-heat boiler, the solution destroyed volatile organic compounds (VOCs) at high destruction efficiency, recovered energy to produce steam, reduced wastewater volume and disposal cost — while solving odor complaints and meeting stringent environmental regulations.
Project Overview
A tank-cleaning facility was struggling with odorous emissions during cleaning operations and high costs of wastewater disposal. Steam cleaning inside tanks volatilized aromatic compounds (e.g. benzene, toluene, ethylene, etc.), which were vented to atmosphere — creating odor nuisance for neighbors and regulatory risk. Wastewater generated from rinsing and cleaning had to be disposed of off-site, costing the facility ≈ US$0.135 per gallon.
Epcon was commissioned to analyze the existing cleaning process and design a combined abatement and recovery system: one that would treat vapor emissions and wastewater/sludge simultaneously, via thermal destruction and waste-heat reuse — maximizing environmental performance and minimizing operating costs.
The Challenge
- Odorous vapor emissions: Steam cleaning pushed aromatic and VOC compounds into the air, causing odor nuisances and creating potential health and regulatory issues.
- Variable and potentially high VOC load / explosion risk: Because the emissions varied depending on cleaning batch and tank contents, the vapor concentration could swing widely; design had to ensure safe operation even in worst-case VOC load (up to 1407% of LEL).
- High wastewater disposal costs: The facility already spent money disposing of wastewater/sludge generated by cleaning — a recurring expense that scaled with production.
- Need for integrated steam / energy recovery: The process consumed steam and energy; the customer wanted a solution that would not just treat emissions and wastewater, but ideally reclaim energy — reducing operating cost and improving sustainability.
Engineering Requirements
To satisfy the customer’s needs and constraints, the system had to deliver:
- A thermal oxidizer capable of destroying VOC-laden cleaning vapors, with sufficient safety margins to handle high VOC concentrations (with dilution and control of combustion risk).
- A ducting network that collects and conveys process gas (from tank cleaning), diluted as needed, into the oxidizer — ensuring safe, efficient mixing and combustion.
- A wastewater/sludge feed system that feeds wastewater and sludge from cleaning operations into the oxidizer — enabling combined disposal / destruction of water-borne organics and residual solvents.
- A waste-heat boiler to recover heat from oxidizer exhaust, producing steam — turning waste energy into usable steam for plant processes (or reducing external steam/fuel demand).
- Controls and safety interlocks to monitor vapor concentration (LEL), ensure safe dilution, combustion, pressure, temperature, and to avoid runaway or unsafe conditions.
- A turnkey solution: design, engineering, fabrication, installation, commissioning — minimizing disruption to the client’s operations.
The Solution
Epcon delivered a full, integrated Odor- & Wastewater-Abatement System, composed of:
- A duct network collecting vapors emitted during tank cleaning, conveying them into the oxidizer, with dilution to safely manage concentration.
- A thermal oxidizer that combusts the diluted VOC/organic vapor stream — thoroughly oxidizing benzene, toluene, ethylene and other aromatic compounds typically released during tank cleaning, ensuring safe emissions and eliminating odor.
- A wastewater / sludge feed line — tank-cleaning wastewater/sludge is directed into the oxidizer, allowing simultaneous thermal treatment of both vapor and water-borne wastes.
- A waste-heat boiler — heat recovered from combustion exhaust is used to generate steam. This helps recover energy that would otherwise be wasted, improving overall energy efficiency.
- Safety controls: the system is designed to safely handle extreme concentration scenarios (up to 1407% of LEL before dilution), ensuring that vapors are diluted, combusted under stable conditions, and that the plant meets regulatory and safety requirements.
This solution transformed a problematic, costly, and environmentally risky cleaning operation into a controlled, efficient, compliant process — combining odor elimination, waste-water abatement, and energy recovery in one package.
Technical Specifications
Oxidizer Type: Thermal Oxidizer (designed for mixed vapor + wastewater feed plus sludge)
Emissions Treated: Aromatic VOCs (benzene, toluene, ethylene, etc.) from tank-cleaning vapors + organics from wastewater/sludge streams
Safety Design: Vapor dilution system with LEL monitoring; design accommodates very high pre-dilution VOC concentrations (up to 1407% LEL) safely, by controlling dilution and combustion conditions.
Wastewater / Sludge Handling: Wastewater and sludge from cleaning are piped into the oxidizer for thermal treatment — eliminating need for external wastewater disposal.
Waste-Heat Recovery: Exhaust heat recovered via waste-heat boiler to produce steam — enabling reuse of energy instead of purely venting heat.
Operational Output / Savings: VOC destruction efficiency: ~ 99.9%; wastewater disposal cost reduced ~ half (from US$0.135 to US$0.06 per gallon); steam production increased vs. previous baseline (initially 2,800 lb steam/hr).
Compliance & Emissions: Meets strict EPA (or relevant) emissions standards for VOC and air-pollution control; odor nuisance eliminated.
The Results
After implementation, the facility achieved:
- Complete elimination of odor nuisance from tank-cleaning operations, satisfying neighboring community concerns and regulatory requirements.
- High-efficiency VOC destruction (≈ 99.9%), ensuring that aromatic and solvent vapors are safely combusted, not vented untreated.
- Substantial reduction in wastewater disposal costs — the facility cut its disposal cost significantly (from 13.5¢/gallon down to ~6¢/gallon) by thermally treating wastewater/sludge instead of off-site disposal.
- Energy recovery with steam production — the waste-heat boiler converts combustion heat into usable steam, enhancing process efficiency and reducing fuel/steam supply cost.
- Compliance and regulatory safety — the system was designed to handle worst-case VOC loads safely (1407% LEL before dilution), ensuring safe operation with sufficient dilution, combustion control, and emissions abatement.
- Improved operational efficiency and reduced cost — combining odor abatement, wastewater treatment, and energy recovery in a single integrated system simplified operations and improved overall ROI compared to separate disposal, ventilation, and wastewater-treatment approaches.
