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Code for design of recirculating cooling seawater system is proposed to be divided into the following five parts:
——Code for design of recirculating cooling seawater system - Part 1: Requirement of intake technology
——Code for design of recirculating cooling seawater system - Part 2: Requirement of wastewater engineering
——Code for design of recirculating cooling seawater system - Part 3: Requirement of seawater pre-treatment
——Code for design of recirculating cooling seawater system - Part 4: Guideline of material selection and corrosion protection design
——Code for design of recirculating cooling seawater system - Part 5: Recirculation cooling water unit
This part is Part 3.
This part is developed in accordance with the rules given in GB/T 1.1-2009.
This part is proposed by the Institute of Seawater Desalination and Multipurpose Utilization, MNR (Tianjin).
This standard is under jurisdiction of the National Technical Committee on Ocean of Standardization Administration of China (SAC/TC 283).
Code for design of recirculating cooling seawater system-
Part 3: Requirement of seawater pre-treatment
1 Scope
This part specifies the technical requirements for seawater pretreatment design of recirculating cooling seawater system.
This part is applicable to seawater pretreatment design for newly constructed, reconstructed or expanded recirculating cooling seawater systems. The seawater pretreatment design of other seawater utilization systems can reference it.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 4482 Water treatment chemicals - Ferric chloride
GB/T 12763.4 Specifications for oceanographic survey - Part 4: Survey of chemical parameters in sea water
GB/T 14591 Water treatment chemicals - Poly ferric sulfate
GB 15892 Poly aluminium chloride for treatment of drinking water
GB 17378.4 The specification for marine monitoring - Part 4: Seawater analysis
GB/T 17514 Water treatment chemicals - Anionic and non-ionic polyacrylamides
GB/T 33584.1 Seawater quality requirements and analysis methods for seawater cooling system - Part 1: Determination of calcium and magnesium
GB/T 33584.4 Seawater quality requirements and analysis methods for seawater cooling system - Part 4: Determination of sulfate
GB/T 33584.5 Seawater quality requirements and analysis methods for seawater cooling system - Part 5: Determination of dissolved solid
GB/T 33584.6 Seawater quality requirements and analysis methods for seawater cooling system - Part 6: Determination of heterotrophic bacteria
GB 50013-2006 Code for design of outdoor water supply engineering
CJ/T 83 Inclined tube for water and wastewater treatment
CJJ 40-2011 Code for design of water supply engineering using high-turbidity raw water
HY/T 187.2 Code for design of recirculating cooling seawater system - Part 2: Requirement of wastewater engineering
HY/T 191 Determination of iron for cooling seawater
HG 2227 Water treatment chemicals - aluminum sulfate
JTJ 275 Corrosion prevention technical specifications for concrete structures of marine harbour engineering
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
recirculating cooling seawater system
a water supply system that uses seawater as a cooling medium and will recirculate, and consists of heat exchange equipment, seawater cooling tower, water pump, pipeline and other related equipment
[HY/T 187.1-2015, Definition 3.1]
3.2
raw seawater
seawater collected and transported by seawater intake structure, and will be subjected to pretreatment
Note: It is revised from GB 50013-2006, Definition 2.0.37.
3.3
seawater pre-treatment
treatment process for raw seawater when the quality of raw seawater cannot meet the quality index of makeup water of recirculating cooling seawater system, usually including measures such as blowdown-cleaning, anti-fouling organism attachment, flocculation, sedimentation and filtration (or clarification)
[HY/T 187.1-2015, Definition 3.14]
3.4
amount of makeup water
amount of water to compensate for recirculating cooling seawater loss due to evaporation, wind blowing, blowdown and leakage during operation
[HY/T 187.1-2015, Definition 3.9]
3.5
amount of blowdown
amount of water that needs to be discharged from the recirculating cooling seawater system under certain concentration multiples
[HY/T 187.1-2015, Definition 3.10]
3.6
amount of evaporation loss
amount of water that is emitted to the air in the form of water vapor due to evaporation of recirculating seawater in a cooling system
[HY/T 187.1-2015, Definition 3.11]
3.7
amount of windage loss
amount of drift of recirculating seawater due to the wind blowing in the cooling system
[HY/T 187.1-2015, Definition 3.12]
3.8
cycle of concentration
ratio of the salt content of the recirculating cooling seawater to the salt content of makeup water
[HY/T 187.1-2015, Definition 3.13]
3.9
floatation-sedimentation tank
a novel integrated water purification structure that combines the dual functions of floatation tank and sloping plate (pipe) sedimentation tank, which can operate according to the sedimentation or floatation condition based on the change of raw water quality
[CECS 110: 2000, Definition 2.0.4]
4 Design principles
4.1 The seawater pre-treatment design of recirculating cooling seawater system shall meet the requirements of safety, reliability, advanced technology, reasonable economy, convenient management, energy saving and environmental protection.
4.2 The seawater pre-treatment design of recirculating cooling seawater system shall have comprehensive, complete and correct design data, and use scientific and reliable methods for analysis and calculation. The design data collection content and the depth shall be in accordance with the relevant requirements of the industry of the recirculating cooling seawater system.
4.3 The seawater pre-treatment design of recirculating cooling seawater system shall be carried out simultaneously with the seawater intake design, the recirculating cooling seawater treatment design and the drainage design with unified planning and coordination.
4.4 The selection of the seawater pre-treatment technological process and the composition of the main structures shall be determined based on the raw seawater quality, the designed water amount, and the post-treatment water quality requirements, and subjected to investigation and research, test with different technological combinations, or the operating experience of seawater pre-treatment under similar conditions, in accordance with local operational management conditions through comprehensive study of technical and economic comparison.
4.5 The design service life of seawater pre-treatment permanent building, structure and buried drainage culvert shall be the same with that of recirculating cooling seawater system. The reasonable design and service life of the pipelines and water treatment components and equipment shall be determined through technical and economic comparison according to the material and product renewal period, and shall meet the requirements for shutdown and maintenance of the recirculating cooling seawater system.
4.6 The layout of seawater pre-treated buildings and structures shall be in accordance with the general plan design of the industry to which the recirculating cooling seawater system belongs, and shall be located on the upwind side in the dominant wind direction.
4.7 Additives and water treatment agents used in seawater pre-treatment shall not cause harm to human health during use and shall not damage the natural environment of the ocean.
4.8 The seawater pre-treatment design of the recirculating cooling seawater system for expansion and reconstruction shall be based on actual conditions and make full use of the functions of the existing water treatment facilities.
4.9 The design of seawater pre-treatment drainage pipelines and sludge treatment shall comply with the provisions of HY/T 187.2.
4.10 The seawater pre-treatment design of recirculating cooling seawater system shall be based on continuous summarization of production practice experience and scientific experiments, use effective new technology, new process, new material and new equipment to ensure safe water supply, optimize operation management, save energy and resource to reduce project cost and operating cost.
5 Water amount and quality
5.1 Water amount
5.1.1 The design water amount of the seawater pre-treatment structure shall be determined according to the amount of makeup water required for the recirculating cooling seawater system plus the self-contained water content of the pre-treatment structure.
5.1.2 The amount of makeup water of the recirculating cooling seawater system shall be calculated according to Formula (1) or Formula (2):
Qm＝Qe+Qb+Qw……………………………………(1)
Qm＝N·Qe·(N-1)-1……………………………………(2)
where,
Qm——the amount of makeup seawater, m3/h;
Qe——the amount of seawater evaporation loss, m3/h;
Qb——the amount of seawater blowdown, m3/h;
Qw——the amount of seawater windage loss, m3/h;
N——the cycle of seawater concentration, which is taken as 1.5 to 2.5. The specific value should be determined by static or dynamic simulation experiment.
5.1.3 The amount of seawater evaporation loss shall be determined according to Formula (3):
Qe＝k·Δt·Q………………………………………(3)
where,
Qe——the amount of seawater evaporation loss, m3/h;
Q——the recirculating seawater amount, m3/h;
Δt——the temperature difference of the cooling tower between entering and leaving the cooling tower, ℃;
k——the coefficient, valued according to Table 1. When the dry bulb temperature of air during entering the tower is the median value, it is calculated by the interpolation method, 1/℃.
Table 1 Coefficient k
Dry bulb temperature of air during entering the tower /℃ k/(1/℃)
-10 0.00076
0 0.00095
10 0.00114
20 0.00133
30 0.00143
40 0.00152
5.1.4 The amount of seawater blowdown shall be calculated according to Formula (4):
Qb＝Qe·(N-1)-1-Qw…………………………………(4)
where,
Qb——the amount of seawater blowdown, m3/h;
Qe——the amount of seawater evaporation loss, m3/h;
N——the cycle of seawater concentration, which is taken as 1.5 to 2.5. The specific value should be determined by static or dynamic simulation experiment;
Qw——the amount of seawater windage loss, m3/h.
5.1.5 The percentage of the amount of seawater windage loss of cooling tower to the amount of recirculating water entering the cooling tower shall be determined according to the tower type and the water escaping rate of the designed and selected dehydrator as well as the water loss rate blown from the inlet of the tower. When there is no data such as the water escaping rate of the dehydrator, the mechanical ventilation cooling tower takes 0.1% of the recirculating seawater amount, and the air duct type natural ventilation cooling tower takes 0.05% of the recirculating seawater amount.
5.1.6 The self-contained water amount of the pre-treatment structure shall be 3.5% to 7.0% of the amount of makeup water of recirculating cooling seawater system according to the seawater quality, the treatment process and the structure type. When seawater treatment structure of other seawater utilization engineering is jointly built with the seawater pre-treatment structure of recirculating cooling seawater system, the calculation basis of self-contained water amount shall be the water amount produced by the jointly built seawater pre-treatment structure.
5.2 Design inflow water quality
5.2.1 The design inflow water quality of seawater pre-treatment shall be determined according to different types of seawater intake structures, as follows:
a) When the seawater intake structure adopts the shore type water intake structure or the seabed type water intake structure, the design inflow water quality shall be based on the actual monitored water quality of the raw seawater;
b) When the seawater intake structure adopts the water intake structure of open channel for diversion or the tidal water intake structure, the design inflow water quality shall be based on the seawater quality obtained by the raw seawater after the hydraulic model test or the actual inflow water quality of the seawater pre-treatment under similar conditions;
c) When the seawater intake structure adopts the beach well water intake structure or other underground water intake structure, the design inflow water quality shall be based on the actual monitored water quality of the experimental well.
5.2.2 The design inflow water quality of seawater pre-treatment shall be tested by a testing and inspection agency with metrological certification and shall meet the following requirements:
a) When the design inflow water quality is based on the raw seawater quality or seawater quality after hydraulic model test, there shall be full analysis data of the water quality at the highest and lowest tide levels of not less than one year. When the inflow water is the tidal estuary water, the testing shall be added once in dry season and wet season.
b) When the design inflow water quality is based on the seawater quality in experimental well, there shall be full analysis data of the water quality in each season of not less than one year.
5.2.3 The full analysis item of the inflow water quality of seawater pre-treatment design shall meet the requirements of Annex A. The analysis method shall be in accordance with GB 17378.4, GB/T 12763.4, GB/T 33584.1, GB/T 33584.4, GB/T 33584.5, GB/T 33584.6 and HY/T 191.
5.2.4 For the inflow water quality in the seawater pre-treatment design, the statistical value of the annual water quality analysis data with a probability of 90% to 95% shall be taken as the design value, and the treatment structure with treatment capacity most unfavorable for water quality verification shall be used.
5.3 Design outflow water quality
5.3.1 The design outflow water quality of seawater pre-treatment shall meet the makeup seawater quality index listed in Table 2.
Table 2 Makeup seawater quality index
Item Unit Control value
Turbidity NTU <10
Salinity - 20~40
pH - 7.0~8.5
CODMn mg/L ≤4
Dissolved oxygen mg/L >4
Total Fe mg/L <0.5
Sulfide (represented as S) mg/L <0.1
Oil mg/L <1
Total number of heterotrophic bacteria cfu/mL <103
5.3.2 The analysis method of seawater pre-treatment outflow water quality shall meet the technical requirements of GB 17378.4, GB/T 12763.4, GB/T 33584.6 and HY/T 191.
6 Process design
6.1 Technological process
6.1.1 The seawater pre-treatment technological process design shall be determined based on the design inflow water quality, design outflow water quality, water amount, and the design cycle of concentration, and subjected to investigation and research, test with different technological combinations, or the operating experience of seawater pre-treatment under similar conditions, in accordance with local operational management conditions through comprehensive study of technical and economic comparison.
6.1.2 When the design inflow water quality meets all water indexes in Table 2, the seawater shall be directly used as the makeup water of recirculating cooling seawater system after being collected by the water intake structure.
6.1.3 When the turbidity of the design inflow water often exceeds the limits of Table 2, the following technological processes should be adopted for seawater pre-treatment:
6.1.4 When there is relatively much silt in the design inflow water, the following technological processes should be adopted for seawater pre-treatment:
Foreword II
1 Scope
2 Normative references
3 Terms and definitions
4 Design principles
5 Water amount and quality
6 Process design
7 Pre-treatment structures and ancillary facilities
8 Agentia use
9 Testing and controlling
Annex A (Normative annex) Records of total analysis and testing of seawater quality
