The raw water filter system is an important part of the chemical water treatment of thermal power plants. The quality of the raw water directly affects the normal operation of the subsequent water treatment equipment and the water quality of the demineralized water, thus affecting the long-term and safe operation of power and thermal equipment. The maximum output of the original system design of our factory was 480t/h. Due to the needs of the “15th” expansion project, the supply of desalinated water increased, the raw water volume increased accordingly, and the water quality requirements increased. The original 2 processing capacities were 240t. /h's gravity valveless filter can not meet the production requirements, and there are problems with the system, and transformation has become inevitable. After investigation and full demonstration, it was decided to adopt a new type of pressure soft fiber filter with soft material in the form of a bundle, which is a filter element.

1 Introduction to the production system process status and problem analysis 1.1 The original process flow Raw water filtration equipment Valveless filter tank is a granular quartz sand filter element, using the principle of water mechanics designed a constant speed filter, the flow rate of 6 ~ 10m / h. The raw water system process flow is shown in Figure 1. The raw water comes from the Yangtze River, and after rough filtration, it enters the water supply system cryogenic power station heat exchanger (for 4) and the refinery return hot water (thermal desalinated water) heats up to about 40°C and is filtered through the valveless filter tank to the clean water tank (pool) , Followed by the clear water pump to follow-up water treatment equipment (except salt water treatment system).

1.2 Existing problems in the original system (1) As the water quality of the system is deteriorated, 2 sets of 4 plugs and dirt deposits are very serious, affecting the raw water heating; one outage is often required for overhaul, and the output of a single exchange 4 is small. The raw water temperature does not meet the process requirements; it reduces the cycle water production of the ion exchanger and increases the cost of water production.

(2) The valveless filter backwashing consumes a large amount of water and takes away a lot of heat, resulting in a great waste of heat.

(3) The valveless filter tank covers an area of ​​too large, and the valveless filter tank with a processing capacity of 240t/h has an external size of 8m×4m×3.6m. Due to site and production constraints, it is impossible to build a large set of large valves. No valve filter, and granular filter material filtration, the filter accuracy is limited by the filter particle size, the effluent turbidity up to 5mg / L, filter cleaning operation is too heavy; prone to platestock, filter replacement frequent, Labor intensity.

2 Feasibility Analysis In order to solve the problems existing in the original system, after investigation and analysis, we adopted the principle of advanced technology and high degree of automation. We used PLC control to reform the raw water system process. The raw water from the system is first filtered by 4 D3000mm high-efficiency fiber filters and then transformed into a low-temperature power station for 4 heating, and then into the clear water tank. A single high-efficiency fiber filter designed for 210t/h.

2.1 The working principle of a high-efficiency fiber filter The high-efficiency fiber filter is a bundle of puffed filaments (D20 ~ 50μm) that is hung on the lower end and is suspended on a perforated plate provided on the upper part of the filter as a filter medium. Filtration equipment. A plurality of capsules are arranged in the portion of the fiber bundle that is close to the perforated plate. During the filtration, water is filled into the capsule to forcibly compress the surrounding fiber bundles to make them dense, and then the water flows upward through the pores of the fibers. The operation. The state of the fiber filter during operation is shown in Figure 3.

When washing, the water in the bladder is drained first, and the extrusion of the fiber bundle is withdrawn, so that the bundle of fibers recovers its bulky state under the combined action of the elastic force of the gravity and the bulking fiber, and then the intake air and the water are mixed and scrubbed.

Since the fiber used as the filter element is a flexible material that can be bent, the filter material can have a diameter of several tens of micrometers, and there is a large amount of space in the filter material layer. During the filtering operation, the fiber is controlled. Extrusion conditions of the bundle can obtain different fiber porosity, and the efficiency and resistance of the filter can be controlled within a set range, thereby solving the problems of the conventional filter equipment such as valveless filter, siphon filter, mechanical filter, etc. All particulate filtering materials such as quartz sand are used for filtration, and the filtering accuracy is limited by the larger particle size of the filter material. The tiny diameter of the filter material greatly increases the specific surface area and surface free energy of the filter material, increases the chance of contact between the impurity particles and the filter material in the water, and improves the filter adsorption capacity, thereby improving the filtration efficiency and the interception capacity.

2.2 Performance Comparison The main performance comparison of the two filters is shown in Table 1.

3 Implementation 3.1 Process High-efficiency fiber filter The process flow in our factory is shown in Figure 4.

Before the filter operates, the bladder is filled with water to ensure that the pressurized chamber reaches the set pressure. When the filter starts, it must be pre-run, and the water turbidity can be detected before it can be incorporated into the system. During the operation of the filter, the adjustment of the flow rate must be smooth, and the sudden change in flow rate prevents the filtered product from being “taken out”, causing the effluent turbidity to exceed the standard. The cleaning process of the filter is as follows: bladder drainage → fan startup → downwash → upwash four steps.

3.2 Operating conditions The filtration system has been put into use since July 29, 2000 in the water treatment system. In order to grasp the operating law and make the filter system safe, efficient and reasonable, we tested the filter's operation cycle.

The system adopts PLC control and adopts three-parameter control for single filter failure control: (1) inlet and outlet pressure difference ≥ 70kPa; (2) effluent turbidity ≥ 2mg/L; (3) set period cumulative water production. Satisfy one to confirm its failure.

The system has been designed in the application of four modes of operation: point operation - manual control of each valve switch; operation - artificial control of each time; semi-automatic - the entire process is divided into capsule filling, operation, cleaning three; fully automatic - Water from the bladder to the wash until it is ready for use. Since the analysis of water turbidity is based on manual analysis, the semi-automatic operation mode can meet the needs of safe production under normal circumstances.

Since the incoming water is affected by the Yangtze River season, and the season is different, the amount of water produced by the cycle is also different. The periodic water production is between 8,000 and 10,000 tons to ensure the quality of the effluent. The turbidity of incoming water is up to 60mg/L and the minimum is only 5mg/L, but the effluent turbidity can meet the requirements. Filters act as retainers for any situation. Protect the follow-up process.

4 Economic Benefits and Social Benefits The raw water system has been transformed and operated for one and a half years. It has solved the problems in the original process, improved the quality and output of the effluent, and reduced production costs.

(1) Water consumption calculation: The high-efficiency fiber filter has a large amount of water in the cycle and a small amount of backwash water, which reduces water consumption and reduces the amount of pollutants discharged. The water consumption comparison calculation is shown in Table 2.

Filter water saving throughout the year = (filter water production rate - valveless filter water rate) × total annual raw water = (0.983-0.974) × 3500000 = 31500t Annual savings of sewage charges = 4.5 × 31500 ≈ 140,000 Yuan (2) Thermal Energy Calculation: Due to the adoption of a new process, backwash water for filtration equipment is not heated, reducing heat loss.

Valveless filter year backwash volume = annual water production × (1-water rate) = 3500000 × (1-0.974) = 91000t

Backwash heat loss = raw water temperature rise × backwash volume × 4.18 = 15 × 91000 × 4.18 = 5.71 × 106 MJ

Discounted standard oil = 5.71 × 106/41.87 = 136.37t where: 41.87 - 1kg standard oil heating value, MJ/kg.

(3) Process effect: The water quality of the high-efficiency fiber filter has been improved, so that the effluent turbidity is stable and less than 2mg/L, which reduces the burden on the cation exchanger and effectively improves the cycle water production of the ion exchanger and reduces the acid. Alkali consumption reduces the contamination of the resin.

(4) Solved the problem of changing the plug 4 and improved the heat exchange effect of 4 and saved the maintenance cost. Renovation of the former two stations 4 Because the poor quality of the raw water is often blocked, each station needs to be repaired for 2 or 3 times per year. The raw water is bypassed directly by the heat exchanger to the valveless filter. The hot brine is cooled by the circulating water to increase the circulating water field. The load. At the same time, due to the low raw water temperature, the periodical water production of the subsequent equipment ion exchangers will decrease, and acid and alkali consumption will increase. In the past one and a half years since the renovation, there has been no blockage, saving maintenance costs and reducing the labor intensity of workers.

5 Conclusion High-efficiency fiber filter with fiber as filter material Compared with valveless filter tank with quartz sand as filter material, it has high filtration efficiency, fast filtration speed, large interception capacity, large cycle water production, and low self-consumption water consumption. The features of small footprint, at the same time solved the problems existing in the original process flow, and have higher economic and social benefits. If you can improve the filter cleaning technology, simplify the internal structure of the filter equipment, so that it has the ability to directly handle the high turbidity water inflow and better solve the large-scale fiber filter equipment, can be more widely used in the field of water treatment .