中小城镇天然气配气管网的压力级别选择

Pressure rank selection of natural gas distribution networks in medium-small towns

中小城镇是我国当前天然气利用快速发展的区域,工程设计中其天然气管网多采用中压A级配气管网,而忽略了中压B级管网具有的特性。为此,比较了中压B级和中压A级管道的爆破能量比和泄漏质量流量比,分析了压能转移利用的贡献,对中压A级管道所需的最小街道宽度进行了定量分析,论证了中压B级管道的适用性。进而用虚拟环网覆盖中小城镇供气区域,推导出等流速工况下中压天然气配气管网管径表达式,计算了相同管网构成时不同供气规模、不同最大管路长度时,中压B级管网与中压A级管网的管材耗量比。结果表明:中小城镇天然气配气管网采用中压B级比采用中压A级投资增加20%以上,经济性相对较差;但中压B级在压力安全和敷设条件方面却具有明显的优势。因此对于老城古镇等区域较窄的街道,要考虑各种方案并综合决策。结论认为:中压B级配气管网在中小城镇的应用具有广阔的前景。

In medium and small-sized towns of China, natural gas utilization is developing fast. In engineering design, medium pressure A distribution networks are mostly adopted, but medium pressure B distribution networks are seldom used. In view of this, blasting energy ratio and leakage mass flow ratio between medium pressure B and A pipelines were compared, and an analysis was performed on the contribution of pressure transferring utilization. Quantitative analysis was also conducted on the minimum street width required by medium pressure A pipelines and the applicability of medium pressure B pipelines was demonstrated. Then, a pipe diameter expression for mediumpressure natural gas distribution networks at constant flow rate was developed by covering the gas supplying regions in medium and small- sized towns with virtual looped networks. On the basis, pipe consumption ratios of medium pressure B and A networks were calculated for the networks with the same constitutions by varying gas supply scale and maximum pipeline length. It is shown that the investment rises by more than 20% when medium pressure B is adopted in natural gas distribution networks of medium and small-sized towns. It is indicated that medium pressure B is economically worse than medium pressure A, but much more superior in terms of pressure safety and laying conditions. As for the old towns with narrower streets, therefore, it is necessary to analyze and compare various programs comprehensively so as to reach the final decision. It is concluded that medium pressure B distribution networks are prospective in medium and small-sized towns.