1. Background.
To achieve carbon peaking and carbon neutrality at home and abroad, how to achieve greendevelopment through energy conservation and emission reduction is an important issue facing thedevelopment of enterprises. The boiler is one of the main equipment for energy conversion in theproduction process of enterprises, but there is generally about 5% energy loss when boilers blowdown. One of the key factors affecting the heat loss of boiler blowdown is the water quality of thewater supply system during boiler operation.
Therefore, suitable boiler water treatment technology should be found to improve the water quality ofthe boiler, thus improving boiler operation efhciency, reducingthe sewage discharge of gas-steamboiler and achieving the purpose of saving energy and reducing consumption. However,CHUANYI Company uses reverse osmosis technology to treat boiler water quality in boiler water supply system,which can not only solve the chloride ion pollution problem existing in traditional sodium ion exchangeresin method, but also obviously reduce the boiler sewage, effectively improving the utilization rate ofresources, and achieve the purposes of energy saving, consumptionreducti棄楿誰茂n.and environmentaprotection.
2. Purpose of Boiler Water Treatment.
The treatment result of feed water of boiler make-up water is one of the important factors affectingthe stable operation of the boiler. Ungualifed feedwater treatment will cause scaling and corrosion ofthe boiler, Because of the scaling phenomenon caused by poor water quality, it is easy to cause burningloss, bulging, cracking, and other phenomena on the heating surface of the boiler. The above factorswill reduce the boiler steam quality, resulting in a large amount of boiler sewage, resulting in highenergy consumption of boiler operation.
It deviates from the current development trend of energy-saving and environmental protection, soreliable measures must be taken to effectively treat the water quality of the boiler in the process oiboiler operation. Effective methods are adopted to remove ionic impurities harmful to boilers in water.to ensure the control of water quality, avoid the damage ofunqualifed water quality to boileroperating components, ensure steam quality, ensure boiler operating effciency and reduce thegeneration and discharge of sewage during operation.
The following will introduce how the reverse osmosis water treatment system developed by CHUANYI is applied to reverse osmosis treatment of feed water of offshore thermal recovery boiler and reverseosmosis treatment of utility boiler water.
3.Application of Reverse Osmosis WaterTreatment in Boiler.
The steam injection system is the core of thermal recovery, which mainly includes a boiler watertreatment system and steam injection boiler. The inlet water quality standard ofsteam injectionboilers is extremely high, which requires no oil, zero hardness, and low salinity make-up water.Unqualifed inlet water quality will cause boiler scaling and coil corrosion,increase maintenance work.and even cause safety accidents.
Therefore, a reliable boiler water treatment system plays a vital role in thermal recovery and is the keyto the safe, continuous, and stable operation of the steam injection system.
The boiler feedwater treatment system developed by CHUANYI Company can be used to removeimpurities in water such as suspended solids, salt, and dissolved oxygen, and meet the water qualityindex of boiler population, to discharge heat loss, save energy and reduce emissions. The systemincludes a pretreatment unit and a desalination unit.
Pretreatment Unit
The pretreatment unit mainly removes suspended solids such as solid particles and colloids and adjuststhe temperature of raw water. The pore size ofthe reverse osmosis membrane is extremely small, andthere are many suspended solids in the infuent, which will cause fouling ofreverse osmosis membrane.resulting in decreased membrane flux, increased cleaningfrequency, and difhcult operation andmaintenance, Therefore, a stable and effcient pretreatment unit is the basis for the normal operationof the boiler feedwater treatment system, and it is generally necessary to reduce the turbidity of rawwater to below 1NTU.
Ultrafltration membrane is a selective permeation membrane that separates solvents and solutesaccording to particle size. lt can separate particles of ten nanometers by pressure drive, removebacterial colloids and macromolecules in water, and reduce the turbidity of raw water to 1.The maindifference between organic ultrafltration and inorganic ultrafltration lies in the different membranematerials and operation modes. lnorganic ceramic membrane ultrafltration is more wear-resistant,usually adopts large-flow cross-flow fltration, and can tolerate higher suspended solids; For organicultrafltration, it is generally necessary to reduce the turbidity of influent to below 5 to ensure longterm stable operation.
Multi-media flter is conventional equipment for offshore oilfeld water treatment, which uses fltermaterials with different particle sizes and materials to adsorb, coagulate and flter suspended matter inwater step by step. The turbidity of inlet water is less than 20, and the turbidity of outlet water canreach 5.
Desalination Unit
The desalting unit removes salt from raw water such as NaCl, CaCl, MgCl, etc, to avoid the risks ofscaling, burning through, and corrosion of boilers. The desalting process is quite different withdifferent boiler water treatment indexes. This study studies desalting schemes with different depthsbased on the reverse osmosis membrane method.
The reverse osmosis process refers to the reverse osmosis process in which brine is separated byapplying an external driving force to overcome osmotic pressure and making water molecules passthrough the reverse osmosis membrane. Reverse osmosis membrane is a selective permeationmembrane that can separate sub-nanometer (low molecular salt) particles according to their size.Desalination gradient design based on the concentration of soluble solids in seawater, the frst-stagereverse osmosis can desalinate more than 97% and the water recovery rate can reach 40% withinthree years; The secondary reverse osmosis treatment can desalinate more than 98%, and the waterrecovery rate can reach 85%. Different desalination units are adopted according to different boilerwater quality.
The water quality index does not require high salt content, so primary reverse osmosis and ionexchanger can be used to meet the reguirements. The active Na?* in the resin for the ion exchanger cancontact the plasma of Ca?*and Mg?*in the exchange water. The purpose of softening raw water can beachieved, and the comprehensive water production rate can reach 35%. At the same time, it reducesthe sewage discharge of the boiler, saves energy, and reduces consumption.
Reverse osmosis technology is a comprehensive technology for effcient treatment of raw water usingflters, water tanks, pumps, and other devices, which is mostly used for water quality improvement.CHUANYI selected this technology as the core technology of boiler water quality treatment. Usingreverse osmosis treatment technology, a set of boiler water quality reverse osmosis treatment systemsis constructed by concentrating multiple appliances, to eliminate impurities in the boiler water. After aseries of treatments, users’ water is obtained, and the purpose of improving the utilization rate ofwater resources is achieved.
Working principle of reverse osmosis system: Coagulant and multi-media flter are used to removeimpurities in the boiler water, scale inhibitor is added to control the state of boiler water to avoid scaleformation in water, and carbon in boiler water is cleaned and fltered by security filter and reverseosmosis chemical cleaning mechanism, Under the action of mixed bed device and regeneration device.salt in water is fltered to obtain clean user water.
The system consists of a multi-media flter, coagulant adding device, scale inhibitor adding controlmechanism, security flter, reverse osmosis device, reverse osmosis chemical cleaning mechanism,carbon dioxide removal appliance, mixed bed device, and regeneration device.
Specifc process: Raw Water Tank- Raw Water- Raw Water Pump- Flocculant- Multi-MediaFilter-Scale lnhibitor -Security Filter-High-Pressure Pump-Cleaning- Carbon Removal -Intermediate Water Tank- Intermediate Water Pump- Mixed Bed- Regeneration Device AndDesalting Water Tank- Desalting Water Pump- User Water. In this process, a roots blower is usedto remove the impurities in the air tank, and a regeneration device is constructed, which will be used asan auxiliary device for mixed bed and multi-media filter to complete the boiler water quality treatment.
Boiler water treatment project in the thermal power plant is a water treatment project that treatsimpurities and scales in boiler water of power station to obtain water up to standard. The water qualityrequirements used in this project are high, which cannot be met by traditional water quality treatmentmethods. CHUANYI uses a reverse osmosis system to purify the water source through a series oftreatments such as dirt fltration so that all indexes ofwater quality meet the standard.
