Coal gas is only a "transitional resource"

Despite the recent coal market downturn, coal-based methane production is still in a “hot” state.

It cannot be avoided that the coal-to-metal methane dispute has not ceased. In particular, on July 17, 2014, the National Energy Administration issued the “Notice on Regulating the Scientific and Orderly Development of Coal-to-Petroleum and Coal-to-Gas-to-Gas Industry”, once again making coal. The controversy and thinking about the development of methane development have been pushed to a climax.

According to the latest release of the "Greenpeace" coal gas industry developments and benefits conference in July 2014, as of June 2014, the total planned production capacity of coal-to-metals methane projects in China has reached 225 billion cubic meters per year.

Among them, the production capacity is only 2.705 billion cubic meters/year, the construction capacity is 14.395 billion cubic meters/year, the production capacity of the pre-project work is 66.2 billion cubic meters/year, the planned production capacity is 63.7 billion cubic meters/year, and the newly contracted production capacity is 780 Billion cubic meters/year. The scale of projects planned for construction is 12 times the scale of production and construction.

The development of coal-to-methane projects in China can be said to have reached a “crossroads.” As a “substitute product” of natural gas, it needs to be analyzed from the "big space" of energy, natural gas, and the environment. Where coal makes methane to go, it requires industry and national leaders. The department will study as soon as possible and formulate relevant policies.

"Large money" shows that there are many types of gas undermine gas, such as coal gas, coal-to-gas, coal-based syngas, etc. The most commonly used are the former two titles. This may be due to natural gas. It is a clean energy source, according to Li Junfeng, director of the National Strategic Research Center for Climate Change and International Cooperation, for the purpose of “big money”. In fact, we should begin with the analysis of the principle and production process of coal-based methane production and explore the specific term for coal-based methane production.

The technical scheme of coal-to-methane production mainly uses coal as raw material, and adopts process technologies such as pressurized pulverized coal gasification or coal-water slurry gasification, conversion, low-temperature methanol scrubbing gas purification, *recovery, methanation, and gas-water separation to produce major products. Methane and by-products**, naphtha, tar, crude phenols, **, and the like. From the reaction process, it can be seen that the raw materials are coal and water, and the main products are methane and carbon dioxide emissions.

It can be seen that this kind of project is a coal chemical project and should be similar to other coal chemical projects when they are named, such as coal production of synthetic ammonia, methanol, synthesis gas (CO+H2), etc. It is known as “coal to methane” is suitable. of.

The appropriate development of a country's need to develop coal for methane depends on three factors: energy development goals, environmental capacity, and natural gas supply and demand. Therefore, our country’s energy development goals determine that the development of coal to methane should be moderated or even controlled.

Energy in most countries in the world is basically realized through energy structure adjustment and energy efficiency or energy conservation. In this process, the proportion of coal is usually reduced and the proportion of natural gas is rising. The energy development goal of our country is to control the total amount of energy and the adjustment of energy structure. One of the energy consumption road maps is to save energy. In achieving energy development goals, coal-based methane does not have such a function, mainly because the development of coal to methane cannot adjust the primary energy structure.

The main reason for the development of coal-based methane may be to convert non-clean energy—coal to clean energy—natural gas (mainly composed of methane), the so-called coal cleansing. However, the production of methane from coal is actually a kind of coal chemical industry, mainly based on coal.

Based on this, both from the supply side and the consumer side, especially the supply side, coal-made methane still does not get rid of coal. For primary energy sources, the energy structure has not been changed and coal is still consumed. It is estimated that the total primary energy consumption in China will reach 4.32 billion tons by 2020. If the coal-to-methane production scale is to be 100 billion cubic meters by 2020, then 320 million tons of coal will be consumed, accounting for 7% of the total primary energy consumption, which is a relatively large proportion. The adjustment of energy structure is a test.

At the same time, although methane production from coal is relatively energy efficient, there is a problem of reduced energy efficiency for secondary use. At present, China converts coal into energy by way of power generation, coal to oil, coal to methanol, coal to ether, and coal to methane. Among them, coal-based methane has the highest energy efficiency, the lowest calorific value per unit of calorific value, and overall project carbon dioxide Less emissions and other advantages, if compared with other coal-based energy sources, coal-based methane has certain advantages.

However, this only explains the energy consumption of coal once used. If the coal methane is considered to be used in secondary production in the live production, the utilization process is lengthened, then coal-based methane does not necessarily have advantages in energy conservation. Take coal power generation as an example. If coal directly generates electricity, the current energy consumption of the most advanced technology can reach 40%.

The comprehensive energy consumption of coal to methane production is 52%. If the power is generated again, the most advanced comprehensive energy consumption for natural gas power generation can reach 58%, and the combined energy consumption for two uses is only 30%. China's "12th Five-Year Plan for Energy Development" proposes that in 2015, the country's overall energy efficiency will increase to 38%, and the comprehensive energy consumption of coal-to-methane for power generation will be much lower than this, and the energy consumption ** roadmap will save energy. There is some conflict in the goals.

In the future, the natural gas industry in the western region should be positioned to maintain rapid development in the future. Within a certain period of time, the market still has a situation of less than supply. Coal-based methane, as a supplemental gas source for natural gas resources, plays a role in catalyzing market development. Therefore, it should be judged from the perspectives of supply scale, project layout and utilization direction, and then a more reasonable and feasible coal-based methane positioning should be determined.

Judging from the supply scale of coal-based methane production, all coal-to-methane projects are analyzed one by one. Considering the operating rate of coal-based methane projects, in the future, the scale of coal-based methane development in China will be lower than previously forecasted.

It is estimated that the supply of coal-based methane in 2015 will be approximately 5 billion cubic meters with an average annual growth of 2.5 billion cubic meters, which is less than the target of 150-180 billion cubic meters for the “Twelve Five-Year Plan for Natural Gas Development”; the supply will be approximately 500 in 2020. Billion to 70 billion cubic meters, with an average annual growth of 90% to 13 billion cubic meters from 2015 to 2020, is a period of high-speed development of coal-based methane.

After 2020, with the growth of unconventional gas resources, the growth rate of coal-to-methane production will further slow down. It is expected that the supply volume in 2025 will be approximately 800 to 110 billion cubic meters, with an average annual increase of 6 to 8 billion cubic meters, and the supply will be 2030. The volume is approximately 1200 to 160 billion cubic meters per year, with an average annual growth of 8 to 10 billion cubic meters, which is lower than the total planned capacity of 225 billion cubic meters.

According to the analysis of the layout of coal-based methane projects, according to the principle of coal-based methane production, 1 ton of coal can produce 250 to 333 cubic meters of coal-based natural gas, and the carbon content of coal is calculated at 70%, yielding 1.28 tons of carbon dioxide. If the coal-based methane production scale is 50 billion cubic meters, there will be 200 million tons of carbon dioxide if there is no effective carbon capture, storage and utilization process (CCS). If China's total carbon dioxide emissions are calculated at 5.3 billion tons in 2020, the carbon dioxide produced from coal-producing methane will account for 6% of emissions. China's coal-to-methane project is mainly concentrated in Xinjiang, Inner Mongolia and other regions. The above two provinces have large geographic area and relatively large environmental capacity. For the central and eastern regions of China, such as Anhui Province, the environmental capacity is small, and it is not recommended to develop coal in the region. Methane production project.

From the perspective of the use of coal to make methane, the gas produced by coal from methane can be used in the same way as natural gas produced from primary energy, and can be used in city gas, industrial fuel, chemical industry, and power generation. However, since coal is directly used as a chemical raw material and fuel for power generation, it is economically more feasible. Therefore, it is not economically reasonable for coal-based methane to be reused for power generation and chemical engineering.

In this case, natural gas produced from coal-to-methane production is only reasonably used for city gas and industrial fuels. However, in the future, western China, especially Xinjiang, cannot consume natural gas on a large scale, so the excess natural gas will only be lost in the east. Therefore, it is recommended that coal-fired methane be consumed in the western region in terms of energy flow, while the natural gas that is produced from coal to methane flows to the east.

The situation of supply and demand for natural gas in China will gradually turn oversupply to exceed demand. Under the premise of guaranteeing domestic gas production and import gas contracts, coal-to-methane production capacity will be the first to be challenged. At present, the total production capacity of coal-to-methane projects has reached 225 billion cubic meters. With the accelerated progress of coal-based methane construction, overheating has already occurred in some areas. In the future, we will face shortcomings of exporting and peaking: First, the existing pipeline network plan cannot meet the external transportation of resources, and second, it accounts for one-third of China's total natural gas resources and resources in 2030, which will affect the peaking of China's natural gas market. Safety.

From the perspective of pipeline transportation, because coal-based methane resources are mainly concentrated in Xinjiang and Inner Mongolia, there are currently built access pipelines mainly consisting of Datang coal-based methane pipelines, and pipelines under construction include the West Third Line. Planning pipelines include New Guangdong and Zhejiang, The general trend of E'anhao, CNOOC's coal-made methane pipelines and self-built pipelines for coal-to-methane projects is from east to west and from south to north, which is the same as the flow of conventional gas in China.

The total pipeline capacity of these pipelines is close to 140 billion cubic meters per year, and in addition to transporting other natural gas resources, it can transport 100 billion cubic meters of coal to methane per year, failing to meet the safety guarantee of the high-limit resource supply of 2025, and even unable to meet the 225 billion yuan. There are certain problems in the export of methane from coal to the total planned production capacity of cubic meters of coal to methane.

From the point of view of peak shaving capacity, coal-based methane is essentially a coal chemical project. One of the characteristics of chemical engineering technology is continuous and stable production. At the same time, it is subject to equipment and other factors, and chemical equipment needs a maintenance period. Based on this, the coal-to-methane project not only has to meet downstream users' peaking needs, but also requires other facilities for peaking due to its own overhaul.

Taking a coal-based methane project with an annual output of 4 billion cubic meters as an example, equivalent to 10 million cubic meters of natural gas per day. When this coal-to-methane project centrally supplies natural gas to a northern city, the consumption market is also 4 billion cubic meters. Due to the volatility of downstream gas, it is assumed that the peak gas consumption is 18 million cubic meters and the low valley gas consumption is 8 million cubic meters. Then, the coal-to-methane project will also have to be matched with conventional natural gas, and it is looking for supporting peaking facilities.

In addition, when the coal-to-metals methane project is overhauled, it draws lessons from other coal chemical industry experience and has 15 to 30 days of repair time per year (although there are industry experts suggesting that this problem can be avoided through multiple series, the more the series, the larger the monomer size. Small, unable to reach the scale of economy, the greater the energy consumption. During this period, the production of 10 million cubic meters of natural gas per day is stopped. How to solve the problem of downstream gas use must be met by other gas sources. It is also a problem.

It can be seen from this that China's development of coal to methane should be moderate. For some areas where coal produces methane, the relevant competent authorities should further rigorously approve and administer it, and plan the layout from the country's overall level, not only to avoid stumbling, but also to control it reasonably. Capacity.

Secondly, the overall supply pattern of China's natural gas is still dominated by domestic gas, with the goal of expanding conventional gas exploration and development and realizing the development of unconventional gas resources. Therefore, whatever the development of coal-based methane projects, the main position of coal-based methane is still the replacement resource for natural gas supply. It is a phased resource for the development of the natural gas industry and cannot be used as the main source of gas in the future, but the development of the overall supply structure of natural gas in China will have an impact. .

Finally, we should coordinate the development of coal-to-methane projects, pipeline transportation, and downstream markets to handle the relationships among the three, especially the joint study of peaking issues.