Application of Water Treatment in Energy and Power Industry

1. Background.

Due to the growth of the world population, the demand for fresh water and electricity will increase significantly than in previous years. Water resources are facing the problem of scarcity, and clear and clean water is also the key to hydropower generation. In boilers, cooling towers and turbines, pure water is the key to ensuring the efficient and reliable operation of the system. When the power industry relies on water to produce clean energy, this creates a dilemma.

NEWater combines advanced reverse osmosis technology with professional knowledge to protect and recycle water in a more economical, environmentally friendly, and cleaner way to meet the power demand of the increasingly interconnected electronic world. With the increasing maturity of reverse osmosis technology, new solutions have completely changed the way of water purification, recovery and reuse, and renewable power generation.

Figure 1 Power and energy applications.

2. Basic Principle of Reverse Osmosis Technology.

The physical explanation of permeation is that the water in the solution flows from the low concentration side to the high concentration side through the membrane structure, and finally the flow of water makes the solution concentration on both sides of the membrane equal.

Reverse osmosis is to apply a certain pressure to make water flow from the high concentration side to the low concentration side through the membrane structure, while the special membrane structure makes the salt in the solution not pass through, and finally separates the salt in the solution from the water.

Figure 2 Working principle of reverse osmosis.

NEWater has been committed to the development of a reverse osmosis water treatment system. The following will introduce its application in the energy and power industry from the aspects of Pretreatment, Boiler Feedwater, Condensate Polishing System, Cooling Tower Blowdown, etc.

3. Pretreatment System of NEWater Reverse Osmosis Water Treatment.

Reverse osmosis technology needs a lot of technical equipment support in the actual operation of the plant. At present, the power industry has this technical support and can complete the water treatment process of the power industry. In the whole system process, the system heater maintains the heating effect on the water treatment system. On the one hand, it ensures the water output in the reverse osmosis process, on the other hand, it keeps the system water temperature constant, which is conducive to the normal operation of the system.

The water in the initial state enters the pretreatment stage after simple precipitation and filtration. In the pretreatment stage, the power industry mainly carries out another deep filtration of water quality, including mechanical accelerated clarifier and ultrafiltration system.

Figure 3 Pretreatment system flow of reverse osmosis water treatment.

In the above process, the purpose of filtering suspended substances, colloidal substances, and microorganisms in water can be realized, and sediment and other deep filtration can be realized with the support of ultrafiltration equipment so that the water pollution index (EDI) entering the reverse osmosis system is less than 5.

The reverse osmosis system of NEWater is equipped with a security filter, reverse osmosis membrane stack, and other equipment to prevent the scaling of the reverse osmosis system, so as to ensure the long-term operation of the reverse osmosis system.

Figure 4 Reverse osmosis system of NEWater.

Although there is a security filter in front of the reverse osmosis inlet to ensure that the membrane elements are not scratched or blocked, the reasonable design and smooth operation of the front pretreatment system are very important for reverse osmosis. However, more than 70% of reverse osmosis application accidents in the power industry are related to pretreatment.

The pretreatment system of reverse osmosis water treatment developed by NEWate company can solve this problem well, and provide the following targeted solutions and suggestions:

  • Two Layer Filter Material Filter: For the reverse osmosis desalination system of surface water source, the two-layer filter material filter (generally anthracite and quartz sand) has a large sewage interception capacity, long operation cycle, slow growth of head loss in operation, and good application effect in practice, ensuring that the reverse osmosis inlet water meets the requirements;
  • Dosing: Various coagulants are added in the pretreatment to remove suspended solids, colloids, and other impurities in the water. However, if it is not added blindly according to the actual situation of the water source, it will not improve the water quality.

On the contrary, substances harmful to reverse osmosis membrane elements will be brought into the water due to the reagent itself or the impurities contained in the reagent. At least, the service life of membrane components will be shortened, and some membrane components will be scrapped simultaneously. At the same time, the compatibility between drugs can not be ignored;

Figure 5 Dosing device.

  • Activated Carbon Filter: Activated carbon can remove organic matter, residual chlorine, and other impurities harmful to membrane components in water. For CA membrane, because of its strong chlorine resistance and poor organic pollution resistance, Cl2or NaOCl should be added in the pretreatment to prevent microorganisms, and activated carbon is generally not added for filtration;
  • Security Filter: The main purpose of the security filter is to ensure that the reverse osmosis inlet water does not damage the membrane module. It can be divided into backwashing types and non backwashing types according to the operation mode. The nonbackwashable filter element is one-time with high operation cost, but good effect.

In the early power industry, most of the security filters are back washable, and the operation is more complex. Due to poor pretreatment, backwashing shall be carried out once a day, and ultrasonic cleaning shall be carried out regularly.

However, residual chlorine is not allowed for composite membranes. The security filter becomes the main hidden danger of bacterial breeding and dirt deposition in the system. Therefore, the service time of the filter element should not be too long, and a higher filter speed can be selected. It is recommended to use l5t/(h,1Ti) filter element filter area, so as to reduce the replacement cycle and operate well.

In this way, the number of filter elements replaced each time is small, the investment is reduced, and hidden dangers such as bacterial breeding are prevented.

Figure 6 Pretreatment system of NEWater reverse osmosis water treatment.

4. NEWater Boiler Feedwater Reverse Osmosis Purification Unit.

In the thermal power industry, boilers and steam turbines are the main equipment. In order to ensure their operation, there are strict requirements for the quality of boiler water. Impurities in the water, such as minerals and gases, will make the process inefficient, wear the generator receiving evaporated water and corrode the exposed equipment. Therefore, it is very important to ensure that the water used in boiler feedwater is as pure as possible.

The boiler make-up water reverse osmosis purification device developed by NEWater can effectively remove harmful impurities in the water, improve the quality of boiler make-up water and obtain as pure water as possible. And it can improve the service efficiency and effective life of the whole power generation system. If the quality of boiler make-up water is poor, the service life and maintenance cycle of the generator unit will be negatively affected.

Figure 7 NEWater boiler feedwater reverse osmosis purification unit.

Process flow of Feedwater Treatment System: Raw Water → Heater → Clarifier → Clean Water Tank → Clean Water Pump → Filter Ultrafiltration Device → Ultrafiltration Water Tank → Ultrafiltration Outlet Booster Pump → Security Filter → High-Pressure Pump → Reverse Osmosis → Decarbonizer → Cation Exchanger → Anion Exchanger → Mixed Ion Exchanger → Demineralized Water Tank → Demineralized Water Pump → Main Power House.

5. Condensate Polishing System.

Since high purity water absorbs a lot of heat, it is conducive to removing heat from the generator and bringing it to the generator. Many types of motors and generators will produce a lot of heat during operation. Too much heat will destroy them from the inside to the outside.

When the boiler heats water, a large amount of condensate will appear. In order to fully facilitate the evaporated water, we use a condensate receiver(condensate tank) to capture it and send it back to the boiler room for reuse. A condensate polishing system is used as an effective water treatment strategy to save power, energy, and chemical costs. This process can also prolong the service life of boiler equipment and improve its performance.

Figure 8 The feed tank in relation to the other elements within a steam system.

6. Cooling Tower Blowdown Reverse Osmosis Water Treatment Equipment.

The function of a cooling tower in the power industry is to exchange the heat of cooling water with air in the tower, so as to transfer the heat of cooling water to the air and disperse it into the atmosphere, and further reduce the temperature of cooling water.

At present, the cooling tower has a large amount of sewage water, nearly 400 tons/hour, resulting in a large environmental burden and a serious waste of resources. The quality of discharged sewage is hard and contains a large number of suspended solids. If it is discharged by improper treatment, it will have a great negative impact on the surrounding environment and groundwater. Therefore, the later treatment and discharge of cooling tower sewage is an important work in the power industry.

The process flow of sewage treatment from the cooling tower of the reverse osmosis system is as follows:

Figure 9 Process flow of sewage treatment from cooling tower of reverse osmosis system.

The demineralized water produced by the ultrafiltration filtration and reverse osmosis desalination treatment system provided by NEWater comp any is returned to the condenser for recycling as circulating feedwater.

The wastewater reuse process using this double membrane method not only solves the pollution problem and reduces the corrosion and clean discharged water, but also the engineering investment of this water-saving project is expected to be recovered within two to three years, creating huge economic, environmental, and social benefits.

It is specifically reflected in:

  • Reduce the feedwater of circulating water of cooling tower, and the current feedwater is about 70t/h;
  • The water cost is saved and the circulating sewage volume of the cooling tower is reduced, which is now about 70t/h;
  • Reduce the burden of environmental protection, save resources, and increase the circulation ratio from 2 times to 3.5 times (due to the supplement of clean demineralized water after ultrafiltration and reverse osmosis treatment);
  • Improve the water utilization rate and reduce the operation cost.

Figure 10 Sewage reverse osmosis water treatment equipment of NEWater cooling tower.

NEWater has always been an industrial water treatment company providing reverse osmosis water treatment technology platform, which is widely used in various industries and applications. The performance of the water treatment system is continuously monitored by using advanced technologies, such as data recording, telemetry, and remote monitoring.

If you have any needs and problems in the energy and power industry, whether it is Pretreatment, Boiler feedwater, Condensate Polishing System or Cooling Tower Blowdown System, our engineers will use the power of analysis to diagnose and provide you with a practical scheme to determine the efficiency of your water treatment system, so as to help you save financial and operating costs!

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