Approved jointly by China National Solar Thermal Energy Alliance and China Boiler Water Treatment Association, the standard of “Organic Heat Carrier for Concentrating Solar Power: Biphenyl - Biphenyl Oxide Mixture”, has been formally issued with dual standard number (standard number for the Alliance: T/GRLM 11-2017, and that for China Boiler Water Treatment Association: T/CBWQA 0004-2017).
The organic heat carrier, biphenyl - biphenyl oxide, is the most widely used and the most mature heat-transfer medium for parabolic trough solar-thermal power stations. Since the 1980s when the first batch of commercialized solar-thermal power stations in the world was established in the United States, biphenyl - biphenyl oxide has always been the mainstream choice of heat-transfer medium for parabolic trough solar-thermal power generation. Biphenyl - biphenyl oxide as an organic heat carrier shows various characteristics that other carriers don’t have: 1) with good thermo-stability, it is workable at the temperature of 400℃, the highest of all organic heat carriers; 2) it has lower vapor pressure, and the saturated vapor pressure is just above 1MPa at the temperature of 400℃; 3) It has lower liquid-phase viscosity, which is good to system running and results in lower system resistance; 4) as it has a flash point above 110℃, it is not inflammable and safer; 5) Content of sulphur and chlorine can be 10ppm or even lower, which leads to effective reduction of equipment corrosion. These characteristics are important guarantees that the requirements of solar-thermal power generation systems are satisfied.
Through reference, it was found that following standards are available: “Heat Transfer Fluids – Specifications and Test Requirements”(DIN 51522-1998) in Germany, and “Organic Heat-Transfer Fluids”(GB 23971-2009) , “Safety Technology Conditions for Organic Heat Transfer Fluids”(GB 24747-2009) and “Heat Transfer Oil – 400 (Biphenyl - Biphenyl Oxide Mixture)”() in China, but there was no standard available yet as for application of biphenyl - biphenyl oxide mixture in the field of solar-thermal power generation. Therefore, in 2015, Jiangsu Zhongneng Chemical Technology Co., Ltd applied for a project to prepare such a standard, and after approval, it together with other 11 dominant units established a standard drafting team.
Drafting units for the standard of “Organic Heat Carrier for Concentrating Solar Power: Biphenyl - Biphenyl Oxide Mixture” mainly included Jiangsu Zhongneng Chemical Technology Co., Ltd, Institute of Electrical Engineering of Chinese Academy of Sciences, CGN New Energy Holdings Co., Ltd and Shandong Tianyi Chemicals Co., Ltd. Cooperative units included Beijing Tianruixing Photo-thermal Technology Co., Ltd, Suzhou Solutia Therminol Co. Ltd., Rayspower Energy Group, Huaneng Clean Energy Research Institute, Northwest Electric Power Design Institute Co., Ltd, of China Power Engineering Consulting Group, Shenzhen Enesoon Science and Technology Co., Ltd, Huadian New Energy Technology Development Company, and Chengdu Boyu New Energy Co., Ltd.
This standard is developed according to requirements of the solar-thermal power generation industry, as well as on the actual technological level and product quality of the organic heat carrier industry in China. It puts forward various technical requirements suitable for solar-thermal power generation, based on full consideration of fundamental characteristics of biphenyl - biphenyl oxide products, special application conditions of the solar-thermal power generation industry such as running temperature up to 400℃, running period up to 25 years and required low equipment corrosion rate, and other factors like safety, etc. In addition, it defines various technical indexes based on experimental verification.
Comparison between indexes in this standard and those in HG/T 2546-1993
|
Item
|
Indexes in this standard |
HG/T2546-1993 indexes (high-class products) |
|
Appearance |
Clear and transparent, without suspended substances |
Flavescent transparent liquid at room temperature |
|
Purity (mass fraction) /%, not lower than Component content Content of biphenyl (mass fraction) /% Content of biphenyl oxide (mass fraction) /%
|
99.9
26.5 ± 0.8 73.5 ± 0.8
|
|
|
Maximum permissible service temperature/℃ |
400 |
|
|
Spontaneous ignition point /℃, not lower than |
600 |
|
|
Flash point (closed type)/℃, not lower than |
110 |
|
|
Sulphur content / (mg/kg), not more than |
10 |
|
|
Chlorine content / (mg/kg), not more than |
10 |
|
|
Water content /(mg/kg), not more than |
300 |
300 |
|
Density (20℃) / (kg/m3) |
1060 - 1064 |
1060-1064 |
|
Crystallization point /℃ |
12.1- 12.3 |
≥12.0 |
|
Carbon residue (mass fraction) /%, not more than |
0.03 |
|
|
Acid value (measured with KOH) /(mg/kg), not more than |
0.02 |
|
|
Kinematic viscosity (40℃) / (mm2/s) |
2.2 - 2.8 |
4.0-4.4 (20℃ kinetic viscosity) |
|
Thermo-stability (400℃, 1000h) Appearance Deteriorating rate /%, not more than |
Transparent, without suspended substances and precipitation 10 |
|
|
Distillation range, temperature range for distillate volume of 95%, /℃ |
|
256.5-258.0 |
The standard of “Organic Heat Carrier for Concentrating Solar Power: Biphenyl - Biphenyl Oxide Mixture”, provides a technical basis for the evaluation and selection of biphenyl - biphenyl oxide products used in solar-thermal power generation. The implementation of this standard will show significance and play an important role in guaranteeing product quality, regulating enterprise production and market order to ensure safe running of the solar-thermal power generation industry, and strengthening supervision and management to realize healthy and orderly development, which will bring great economic and social benefits.
(Reported by Du Fengli and Su Yahong)
