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2022-08-14
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Bottled compressed natural gas transmission and distribution process

I. Introduction

nowadays, countries around the world have raised their awareness of the status of natural gas in the world energy to an extremely important height. As the third largest natural energy after coal and oil, natural gas is known as a new environmental protection energy in the 21st century. Natural gas consumption will rise to the first place in the 21st century. Therefore, countries have invested a lot of human and material resources in the development and utilization of natural gas. Marked by the "Shaanxi gas to Beijing" project, China has opened the prelude to the great development of natural gas. The "west to East Gas Transmission" project will become the largest natural gas construction project in China. This means that China has entered the era of natural gas development

however, there are still many factors restricting the development of natural gas construction in the process of natural gas transmission and distribution. We believe that there are three main problems:

1. Huge investment in natural gas pipeline construction

2. Unreasonable natural gas consumption structure

3. Inappropriate management system and the needs of natural gas development

based on the above view, many small and medium-sized towns, especially those located far away from natural gas pipelines, have great difficulties in natural gas construction. This paper discusses the feasibility of using bottled compressed natural gas transmission and distribution technology to meet the natural gas needs of small and medium-sized cities and towns

II. Introduction to bottled compressed natural gas transmission and distribution process

bottled compressed natural gas transmission and distribution process flexibly applies compressed natural gas technology to urban gas transmission and distribution system, and solves the connection and pressure regulation problems between ultra-high pressure natural gas system and urban gas pipe system. The main process is divided into three parts:

1. Pressurized filling of natural gas

in the gas source, the natural gas is compressed to 205 MPa after purification, and then filled into the compressed natural gas cylinder through the filling equipment

in this process, the quality of natural gas must meet the requirements of high-pressure transportation, and the content of water and C02 must be strictly controlled

2. Transmission of compressed natural gas

compressed natural gas cylinder groups are transported to gas consumption points (small and medium-sized towns, users) by car or ship. This process makes full use of the advantages of convenient and flexible highway transportation and shipping. At the same time, the group quantity of compressed natural gas cylinders can be adjusted at will to meet the needs of different users. At present, the skid mounted bottle group we developed meets the standards of Lloyd's register of shipping and has obtained a national patent

3. Decompression transmission system

the pressure in the bottled compressed natural gas cylinder is 20.25 MPa. In order to meet the needs of the urban gas system, it is necessary to reduce the pressure to the pressure level of the urban gas pipe (high, medium and low pressure). According to the pressure level system of users or urban gas pipes, a variety of processes and equipment can be selected to meet the pressure needs. At present, it is often solved by heat tracing regulator or return tube bundle. The decompression process is also equipped with control facilities such as overpressure release, emergency cut-off, low-voltage switching, etc

see the process flow chart for the above processes

to sum up, the main equipment of the bottled compressed natural gas process has been localized in China, and a national safety standard or ministerial standard has been formed to ensure the experiment. Ultra high pressure natural gas connection has practical equipment in the oil system. Therefore, the technology of bottled compressed natural gas is completely feasible

the bottled compressed natural gas transmission and distribution process has the following advantages:

1. The operation is flexible and reliable, which can meet the needs of different types of users

2. Simple process and less land occupation

3. Short construction period

III. economic feasibility analysis

the bottled compressed natural gas transmission and distribution process is a gas transmission and distribution process developed to meet the natural gas needs of small and medium-sized cities and towns or industrial users. Therefore, its economic comparison should be based on the gas development mode of small and medium-sized cities and towns. At present, as a small and medium-sized town, there are three commonly used pipeline gas supply methods:

1, natural gas pipeline transmission (long-distance pipeline)

2, LPG pipeline transmission

3, LPG mixed gas transmission

as for the first transmission method, if the geographical location of the town is close to the natural gas pipeline, undoubtedly, the first transmission method is the most economical. Otherwise, the first transportation mode will face loss operation (long pipeline, large investment, small consumption and high pipeline transportation cost). In this case, the second and third conveying modes will be selected

therefore, the economic feasibility of the bottled compressed natural gas transmission and distribution process should be compared with the economics of LPG pipeline transportation and LPG wet gas transportation. The comparison results are shown in Table 2 and table 3

basic data

1. The price of LPG is 2600 yuan/ton; The price of natural gas is 1.2 yuan/International Party (management price)

2. The low calorific value of LPG is 108 MJ/standard cubic meter; The low calorific value of natural gas is 40 MJ/standard cubic meter

3. The transportation distance is within 200 kilometers

several notes:

1. For the raw material cost of compressed natural gas, the pressurization cost and transportation cost are considered

2. Natural gas is oil associated gas

3. The gas mixing process is considered by adjusting the blessing gas process in proportion

from the anti risk analysis, according to the current actual price of natural gas and liquefied petroleum gas in China:

liquefied petroleum gas: 3000 yuan/ton in the mechanical property test of materials

natural gas price: 1.2 no/standard square, cngl 9.0 yuan/standard square (considering the price rise of transportation fuel)

if the sales price of gas remains unchanged, the economic comparison is shown in Table IV

through the comparison, the following conclusions are drawn:

1. The bottled compressed natural gas transmission and distribution process is superior to the other two processes in terms of risk resistance

2. From the economic benefit analysis, the bottled compressed natural gas transmission and distribution process is economically feasible

3. The scale benefit of bottled compressed natural gas transmission and distribution process is obvious

4. Bottled compressed natural gas transmission and distribution is not suitable for residential areas with less than 500 households

5. The start-up scale of bottled compressed natural gas transmission and distribution process should be 2000 households

IV. actual use cases and completed work

in December 1999, Beijing Huairou Dadi gas company completed the first compressed natural gas transmission and distribution project in which a layer of paint on the bottle can play the role of warming in winter and cooling in summer, providing 11000 households in Huairou with compressed natural gas, with a daily supply of 4500 cubic meters. From the actual situation of the nine month operation of the project, the bottled compressed natural gas transmission and distribution process has good reliability and safety. The economic benefits are obvious (the company originally used liquefied petroleum gas mixture), which has been highly praised by relevant leaders of cities and counties

the bottled compressed natural gas transmission and distribution process has obtained one national invention patent and two utility model patents. And passed the technical appraisal and asset appraisal of Beijing Science and Technology Commission and asset appraisal department

up to now, the bottled compressed natural gas transmission and distribution process has been used in many communities in Beijing and France, and has achieved good results and benefits

v. problems existing in the bottled compressed natural gas transmission and distribution process

although the bottled compressed natural gas transmission and distribution process has achieved certain results, there are still many technical problems to be solved

the main problems are as follows:

1. Specification interpretation problem

bottled compressed natural gas transmission and distribution process is a new technology, and the relevant problems are not involved in the specification of urban gas juice design, so there is a gap in the specification interpretation of this process

2. Equipment improvement problem

at present, most of the equipment used are domestic. The degree of self-control of the equipment is not high, and the control means are backward. We need to develop products with high control level. This work is being actively carried out, and we need the support and help of the majority of gas peers

3. Limited gas supply range

because there are few gas sources with compressed natural gas supply capacity at present, this technology cannot be widely promoted

source: yesizecom

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