ELCOGAS, S.A. - Puertollano, Spain

IGCC Wastewater (ZLD) System

The Client's Needs

ELCOGAS, S.A. IGCC plant
ELGOGAS IGCC Power Plant - Spain

ELCOGAS, established in 1992 with the aim of building and operating a 335 MW Integrated Gasification Combined Cycle (IGCC) power plant as well as the commercialization of its technology.

Based on the PRENFLO™ gasification process, the plant uses a mixture of local coal (from ENCASUR) with a high-ash content and petroleum coke produced at a nearby REPSOL refinery as feedstock.

The goal of the plant is to use technical innovation to create a highly efficient, environmentally sustainable plant when compared to other thermal power generation. This is also true of the water treatment system, which would need updating to meet required compliance to increasingly strict local and state regulations.

The Solution

Installed CoLD® Crystallization system
Installed CoLD® Crystallization system

Veolia Water Technologies worked with ELCOGAS to implement a new, more effective water treatment system for the plant. Veolia developed a new thermal process based on similar applications which is ideal for treating gray water from the gasifier. It offers a reliable, robust solution to achieve the objectives of the plant for maximum water reuse, Zero Liquid Discharge (ZLD), and use of the best available technology.

The proprietary CoLD® Process, utilizing HPD® evaporation and crystallization technology, was developed to overcome challenging wastewaters such as IGCC gray water that may contain chloride, ammonia, organic acids, cyanides, sulfides, silica, and heavy metals including mercury and selenium. It provides a solution without the complications and costs of pretreatment and drying equipment to attain a ZLD facility.

Process Description

The CoLD® Process requires no chemical or filtration pretreatment of the gray water prior to evaporation that adds cost and complexity to the process. The gray water is fed directly to an HPD® MVR evaporator in which the bulk of the concentration takes place. The vapors generated are sent to a vapor washing system in order to protect the vapor compressor from foaming events and carryover that are common with certain wastewater streams.

Concentrate from the evaporator is sent to the CoLD crystallizer where chlorides and other solids are removed from solution. What makes this process unique is that at the lower temperature in the COLD crystallizer, the highly soluble solids will crystallize at relatively low temperatures. These solids are then sent to a filter press for disposal and the filtrate is recycled back to the crystallizer.

Volatile compounds (formic acid, ammonia, cyanide and hydrogen sulfide) which condense into the distillate produced from the evaporator and CoLD crystallizer are removed by an integrated stripping system. This allows the distillate quality to meet the recycled water specifications.

Key Condensate Quality Data

HPD® ZLD System

Parameter Specification (mg/l) Actual (mg/l)

Ammonia

<10.0

<10.0

Cyanide

0.04 

0.015 

Sulfide 

0.2

<0.1

Mercury 

0.02 

<0.01 

Arsenic 

0.05 

<0.01

Selenium

0.001 

<0.0005 

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