discharge summary system design

Transcription

1 liquid discharge ZLDzero summary system design

2 ZLD TECHNOLOGY S.M.A.R.T. Z PROCESS TM S.M.A.R.T. Z PROCESS TM Zero Liquid Discharge (ZLD) is the ultimate cutting-edge process for the total elimination of wastewater effluent into neighboring waterways. This process allows the return of high quality water for reuse, limiting the water footprint. A growing number of industrial operators face the challenge of developping more sustainable solutions for their production sites. For water needs, Suez environnement s Zero Liquid Discharge (ZLD) process is a complete and costeffective solution recovering high quality water for re-use while enhancing the production of solid by-products and reducing the facility s environmental footprint. The ZLD System removes unwanted solids from streams and returns high-quality water to the plant process (source). Membrane filtration (such as reverse osmosis) may be used to concentrate the stream and to return the clean permeate to the process. In this case, a much smaller volume (the reject) will require evaporation, thus enhancing performance and reducing power consumption. In many cases, falling film evaporation is used to further concentrate the brine prior to crystallization. Falling film evaporation is an energy efficient method of evaporation, typically to concentrate the water to the initial crystallization point. The resultant brine then enters a forced-circulation crystallizer where the water concentrates beyond the solubility of the contaminants and crystals are formed. The crystal laden brine is dewatered in a filter press or centrifuge and the filtrate or centrate (also called mother liquor ) is returned to the crystallizer. The condensates from the falling film evaporator and crystallizer are collected, cooled and combined with the reverse osmosis permeate and returned to the process, eliminating the discharge of liquids. If any organics are present, condensate post-treatment may be required for final clean-up prior to reuse. ZLD TECHNOLOGY: S.M.A.R.T. Z PROCESS TM & S.M.A.R.T. ZONES TM The S.M.A.R.T. Z PROCESS TM is the ultimate process covering all the needed steps for ZLD applications. This process may utilize all or part of the six S.M.A.R.T. ZONES engineering modules including pretreatment, preconcentration, evaporation, crystallization, condensate post-treatment and solids recovery. Each module can be executed in parallel to expedite the design and implementation process. This integrated solution covering all treatment steps and supplied entirely by proprietary technologies allows project optimization in terms of capital and operating costs.

3 S.M.A.R.T. Z PROCESS TM reuse/recycling ZONE 6 - SOLIDS RECOVERY ZONE 1 - PRETREATMENT ZONE 5 - CONDENSATE POST-TREATMENT condensate condensate permeate ZONE 2 - PRECONCENTRATION ZONE 4 - CRYSTALLIZATION ZONE 3 - EVAPORATION applications oil & gas refining & petrochemicals chemicals metals & mining power

4 S.M.A.R.T. ZONES TM S.M.A.R.T. ZONE 1 pretreatment In the majority of cases, it is more cost effective to remove contaminants at the early stage prior to the preconcentration. Several treatment solutions are available depending on the required target: suspensed solids removal, calcium/magnesium precipitation, organic removal, etc. S.M.A.R.T. ZONE 4 crystallization The crystallizer is the heart of the ZLD process. Typically, forcedcirculation crystallizers are used to evaporate the water past the crystallization point. Crystals are grown to an adequate size before they are mechanically dewatered and the resulting liquid is returned to the crystallizer. The clean condensate is recycled in the plant as process water and the dewatered crystals (see S.M.A.R.T. ZONE 6) are transported off-site for reuse or disposal. The wastewater chemistry has a large effect on the crystallizer design. S.M.A.R.T. ZONE 2 preconcentration Where possible, a specific process such as reverse osmosis can be used to reduce the volume of wastewater to be evaporated. The permeate is reused in the process and the reject is sent to evaporation. S.M.A.R.T. ZONE 5 condensate post-treatment During the evaporation/crystallization process, steam is generated, and after cooling, condensate is formed. In some cases, like for boiler feed water, the collected condensate must be polished, to remove entrained impurities. Dissolved matter which can cause corrosion and maintenance issues are effectively removed by condensate post-treatment. This process step allows the condensate to meet most stringent reuse and process water requirements. S.M.A.R.T. ZONE 3 evaporation When the concentration of dissolved solids is not high enough to form crystals, water is evaporated prior to the crystallization step in a falling film evaporator. These evaporators require less heat/power per unit of water evaporated and are suitable for a wide range of brines specification capable of handling large streams. S.M.A.R.T. ZONE 6 solids recovery Sludge generated by S.M.A.R.T. ZONE 1, is generally mechanically dewatered in a plate-and-frame filter press as an example. A solids concentration of 20-50% dry solids can usually be achieved. The dewatering filtrate is simply recycled in S.M.A.R.T. ZONE 4. The crystals from S.M.A.R.T. ZONE 4 can also be mechanically dewatered. Corrosion resistant materials compatible with the presence of high salt concentrations are necessary. The crystals can be dewatered in a filter press or centrifuge and as a result, much higher solids concentrations can be achieved.

5 system enhancements / energy by-products recovery High quality by-products can be produced from a ZLD system under the form of permeate, condensate and salts. Our process experts will define the most suitable solution for the project. mechanical vapor recompression For some applications, turbofans or high speed compressors can be more economical by reducing the steam usage with electricity. Water vapor produced in the evaporator or crystallizer can be compressed and reused as the heating source. Depending on the boiling point elevation of the wastewater, singleor multi-stage vapor compression systems can be used. multiple effects Evaporation processes such as falling film evaporators can be installed in series such that the water vapor from one is reused in the next. In this way, the efficiency of the evaporation process can be increased. waste heat usage Cost saving are enhanced when other heat sources found in most industrial applications are productively reused in the ZLD design. This can take the form of exhaust gas or low pressure return steam. The evaporator designs can make use of these waste heat sources, significantly saving on energy requirements. integration SIMPLIFIED effects The MODULAR AQUEOUS REDUCTION TECHNOLOGY chemistry of ZLD systems is very complex. The waste streams from the different zones are very interdependent. Having a single point of contact for the entire system is therefore crucial for CAPEX and OPEX optimization. We can design, supply, install and operate part of or all of the components of the ZLD System (Physical-Chemical pre-treatment systems,membranes, evaporators, crystallizers post treatment systems and solids recovery systems).

6 contacts SUEZ environnement - Treatment solutions Tour CB21 16, Place de l Iris Paris La Défense Cedex France