Ash-water separator

Ash Water Separator

I. Overview
The HSFL series ash water separator is an advanced device developed based on the analysis and summary of contemporary water purification methods. After long-term use, it has been well received by users. This equipment is mainly used for the purification of industrial boiler (kiln) furnaces, coal washing plants, coking plants, wet dust removal in hydropower station boilers, hydraulic ash and slag flushing wastewater, and coal mine flushing (washing) wastewater. It can also be used for water supply purification and treatment of other wastewater containing general suspended solids in rural areas, towns, industrial and mining enterprises, and other industries.
II. Working Principle
Ash water is injected by a slurry pump into the stirring and coagulation zone, then enters the inclined plate sedimentation zone, and finally passes through the filtration layer to obtain clear water that meets reuse and discharge standards. When necessary, the configured backwashing system is used to backwash the filter media. The mechanisms of each part are as follows:
1. Stirring and Coagulation
Pressurized (0.1-0.3 MPa) ash water is sprayed at high speed through a nozzle into the first reaction zone, creating a corresponding low pressure. The gas contained in the micropores of the ash and slag expands in volume under low pressure. With intense stirring, the gas can be flushed out by water, increasing the specific gravity of the slag particles. If coagulants are added, flocculation can occur here, preparing for the next step of sedimentation and clarification.
2. Inclined Plate Sedimentation
Based on the principle of horizontal flow sedimentation: when the flow rate (Q) and particle settling velocity (U) are constant, the sedimentation efficiency (E) is proportional to the horizontal area (A) of the sedimentation tank, i.e., E = UA/Q.
Thus, dividing a sedimentation tank into m intervals horizontally by height increases the horizontal area by m times, thereby improving sedimentation efficiency E by m times. To facilitate the removal of accumulated sediment, the plates are inclined at 60°. Although the effective horizontal area is reduced by 50%, the goal of improving sedimentation efficiency is still achieved. All particles with a settling velocity greater than the upward flow velocity of the ash water in the inclined plate zone will deposit on the plates.
3. Filtration
The smaller the filter media particles, the smaller the gaps between them, and the smaller the particles that can pass through these gaps. Therefore, all particles larger than the gaps in the sludge layer are retained by the filter layer, achieving the separation of solid and liquid phases.
4. Backwashing
Based on hydraulic scouring, the particles retained in the lower part of the filter layer and ash particles, which have a specific gravity greater than water, are separated from the filter media. This restores the filtration performance of the filter layer.
IV. Main Features
1. Purification efficiency: over 95%;
2. Cost per ton of recovered clear water: about 0.06 yuan;
3. Clear water recovery rate: 90-95%, enabling a closed-loop system with zero wastewater discharge;
4. Small land footprint: requires about 20-50 square meters, only 10-20% of the land area needed for a sedimentation tank handling the same volume of ash water, saving over 80% of land;
5. Low investment: only about 50% of the construction and land acquisition costs of a sedimentation tank with the same capacity, with potential recovery from the value of the reclaimed clear water;
6. Quick installation: only a 10-30 square meter foundation is needed for rapid installation and operation;
7. Easy centralized management: multiple ash water separators can be used in parallel in a pipeline network, requiring only the operation of a few corresponding valves;
8. Treated ash concentration: up to 5000 mg/L;
9. Suspended solids concentration in recovered clear water: less than 50 mg/L, far below the discharge standard (200 mg/L);
10. Recovered clear water is pressurized: the pressure depends on the head of the slurry pump used, allowing direct connection to wet dust collectors or other water usage points.
V. Closed-Loop Ash Water Separation System
Wastewater from hydraulic ash and slag flushing in industrial boiler (kiln) furnaces, small power station boilers, and various coal-fired furnaces, as well as flue gas cooling and various wet dust removal wastewater, first flows into a collection pond to settle large particles. Part of the ash water is then pumped by a slurry pump to the SHFL ash water separator (another part can be directly used for hydraulic ash and slag flushing). The clear water from the clear water valve can be directly introduced into wet dust collectors or stored in a reclaimed clear water tank for later use by a clear water pump for backwashing the separator or other purposes. This forms a closed-loop system with zero wastewater discharge.
If the pH of the ash water is <5.5, it must be neutralized to around pH 7 using alkaline solutions (e.g., boiler blowdown water, sodium carbonate, sodium hydroxide solution, lime water, etc.).