Source: CSSC
Understanding of marine low-speed engine emissions
and thoughts on future technology
and product development under the dual carbon strategy (1)
Tao Guohua, Liu Bo, Marcel Ott, Gui Yong
Preface
In view of the current discussion of double carbon Enthusiastic", and also based on the "divergent opinions" of the current discussion, we tried to "look at the industry from outside the industry" and "look beyond the motivation to look at the motivation" to raise some questions, do some research, and make some thoughts on the current status quo for industry reference. At the same time, we try to introduce our understanding of this major to outsiders when communicating with peers.
(This article actually discusses the emissions of low-speed marine engines during use, that is, ship shipping, and thoughts on the focus of future product development. my country is a major ship manufacturing country, and emissions during the ship manufacturing process include pollutants and carbon emissions. Worthy of attention, this needs to be discussed separately)
1. The importance of marine low-speed engines in global economic life and its important role in the development of ships
80% (transportation load)/70% (transportation value) of world trade is made up of The maritime industry is completed, and 80%-90% (power number) of the main power of global shipping is provided by the technical product of marine low-speed engine, so when we discuss the technical product of marine low-speed engine, it can also be understood that we are discussing A power output product that promotes 60%-70% of world trade transportation volume. There is no doubt about its important role and significance in global economic life. (Why does this technology product have such a status and will it have continued vitality in the future?) This status means the value and significance of the issues we discuss about this technology product.
Marine low-speed engine, also known as a two-stroke reciprocating internal combustion engine, its principle is to burn a certain type of fuel in a closed volume to produce high-temperature and high-pressure working gas to push the mechanical mechanism to do work and then output the propeller needed to propel the ship forward. At the same time, the working gas generated by combustion is discharged to the atmosphere through a series of equipment after completing its work. Its essence is an energy conversion device that converts fuel containing chemical energy into thermal energy through combustion, and then converts thermal energy into mechanical energy. As the heart of the entire ship, the marine low-speed engine is not only the most important equipment among all ship equipment (its name is vividly called "Main Engine"), but its technological progress is also one of the main driving forces for the continuous improvement of ship design. Due to the particularity of ship shipping, as the basic guarantee for the safe operation of ships, the safety and reliability of marine low-speed engines need to be paid more attention to. The special relationship between marine low-speed engines and ships requires us to pay full attention to the development of marine main engines (mainly marine low-speed engines) when discussing ship development. For example, the large-scale design of container ship must be based on the design of ultra-high power availability of marine low-speed engines (more than 100,000 horsepower, etc.); the improvement of thermal efficiency of marine low-speed engines is one of the important measures to improve the ship energy efficiency design index (EEDI) ; Emissions from marine low-speed engines are one of the main sources of ship emissions. For marine low-speed engines, efficiency (economy), environmental protection, and reliability are the most important product elements.
2. Ship emissions
Each industry and each technical product has its own characteristics in terms of emissions that affect the environment. The prerequisite for precise and effective pollution control and emission reduction is to accurately, objectively and completely grasp the actual emission status of this industry and this technology product . Before discussing the emissions of marine low-speed engines and the development of "dual carbon", it is necessary to understand some basic conditions about the current "emissions" of ships.Ship emissions are mainly divided into "pollutant emissions" and "greenhouse gas emissions": pollutants include: NOX, SOX, PM (particulate matter, in which the insoluble BC ( black carbon ) also has a greenhouse gas effect); greenhouse gas Gas GHG includes: CO2, CH4, N2O. Ship "emissions" are mainly produced by fuel combustion of ship equipment (main and auxiliary engines and fuel boilers , etc.). Their composition and concentration depend on fuels with different chemical compositions and the combustion mechanism results caused by different technical paths.
In the current world shipping fleet, the main and auxiliary engines mainly use heavy oil and diesel as fuel. They adopt the two-stroke Diesel cycle technology path for marine low-speed engines and the four-stroke Diesel cycle technology path for marine medium-speed engines. Emissions are the main source of ship emissions.
Pollutants:
NOX
NOX (IMO regulations include NO and NO2) The production mechanism is caused by the high temperature and oxygen-rich combustion environment during combustion; NOX enters the human lungs and can cause bronchitis or emphysema; NOX can also interact with the atmosphere Other pollutants undergo photochemical reactions to form photochemical smog pollution ; NOX reacts in the atmosphere to form nitric acid , which is one of the causes of nitric acid rain.
SOX
The generation of SOX (mainly SO2) is closely related to the sulfur content in the fuel; its harm to the human body is mainly to stimulate the human respiratory system. It can combine with other components in the atmosphere to form sulfuric acid mist. In severe cases, smog events will occur ( Such as London smog incident ), it is also the cause of sulfuric acid rain (sulfuric acid rain plays a major role in acid rain). The generation mechanism of
PM
PM (particulate matter) is due to impurities in fuel oil and intermediate products of incomplete combustion. Not only is PM itself harmful to the human respiratory system, but the pores of soot particles often adsorb sulfur dioxide and carcinogenic polycyclic aromatic hydrocarbons and other substances.
Greenhouse gas (GHG):
CO2 emissions mainly come from the combustion of C-containing fuels. The greenhouse gas effect can be characterized by GWP, that is, the global warming potential of pulsating emissions over a time span of more than 100 years. The GWP of CO2 is 1; CH4 mainly comes from methane fuel escape and incomplete combustion (GWP is 28); N2O mainly comes from the combustion of fossil fuels and biomass fuels. Currently, there are few studies on the generation and control of N2O in the internal combustion engine , but its greenhouse gas effect is very strong and the industry needs to pay attention to it in the future (GWP is 265). In addition, black carbon (BC) is the form of insoluble carbon particles in the pollutant PM. It is not a greenhouse gas, but it has a strong greenhouse effect (GWP is 900). Greenhouse gas emissions lead to an increase in global average temperatures, triggering melting of ice caps, extreme weather, drought and sea level rise etc.
3. The actual situation of ship emissions and marine low-speed engines
The following is a study of ship emissions and the emission conditions of marine low-speed engines. From the perspective of the constraints of laws, regulations and policies, the actual emissions caused by international shipping do not belong to a country. Within the scope of emission statistics, this article uses international shipping and low-speed engine emissions to compare emissions between countries to better examine the emissions situation of our industry. International shipping is based on statistics from the International Maritime Organization (IMO) and is transnational/inter-regional port transportation.
At the same time, in order to better evaluate the actual emission status of marine low-speed engines, we have adopted the following calculation boundary conditions (different calculation methods are also welcome):
Bulk carriers, oil tankers, container ships, chemical tankers, liquefaction Natural gas carriers , and general cargo ships are the main ships in international shipping. According to the "Fourth IMO GHG Study 2020" data, in 2018, these six types of ships accounted for 93.1% of the deadweight tonnage and 39.6% of the number of international shipping ships. These ship hosts usually choose low-speed machines, which is close to the data of 38.6% of the number of low-speed machines.Therefore, it can be approximately considered that the main engines used by these six types of ships are all low-speed engines. These six types of ships consume 85.4% of the total fuel, of which main engine consumption accounts for about 80%. Therefore, it is estimated that the total fuel consumption of low-speed engines accounts for about 68.4% of the international shipping industry.
Based on this, the following emission data is analyzed:
NOX
In 2018, the global international shipping industry’s NOX emissions accounted for 16.655 million tons, accounting for 13.4% of the world. If compared with countries, the international shipping industry ranks second only to China's 28.333 million tons and higher than the United States' 11.184 million tons.
According to the data of "Fourth IMO GHG Study 2020", it can be seen that the total fuel consumption of the six types of ship main engines in 2018: bulk carriers, oil tankers, container ships, chemical tankers, liquefied natural gas ships and general cargo ships was 164.582 million tons. Since the main engines of these ships are usually low-speed engines, their fuel consumption can be calculated as 169g/kWh. Therefore, it can be calculated that the total power of the main engines of Class VI ships in 2018 (approximately equivalent to low-speed engines) is approximately 9.74×1011kWh. Before 2011, the NOX emission factor of ship's low-speed engines was 17.0g/kWh (Tier I), and after 2011 it was 14.4g/kWh (Tier II). To facilitate calculation, the NOX emission factors of all low-speed engines were taken as the average of the two, that is 15.7g/kWh. Using the total power of low-speed engines in 2018 multiplied by the emission factor, it can be calculated that the NOX emissions from low-speed engines in 2018 were approximately 15.2896 million tons, accounting for approximately 91.8% of the international shipping industry and 12.3% of the world. Second only to China and higher than the United States, it ranks second by country.
SO2
In 2018, the international shipping industry SO2 emissions were 10.093 million tons, accounting for 8.58% of the world. If compared with other countries, it is less than India’s 12.209 million tons and higher than the United States’ 7.588 million tons, ranking third.
SO2 emissions are determined by the molecular weight of the fuel itself. The total fuel consumption of low-speed engines accounts for about 68.4% of the international shipping industry. If the fuel is completely burned, the SO2 generated will also account for 68.4% of the international shipping industry, and 5.87% of the world, that is About 6.904 million tons, second only to Chile and higher than Kuwait , ranking 25th by country.
PM
-PM2.5
In 2018, PM2.5 emissions from the international shipping industry were 1.665 million tons, accounting for 4.09% of the world. If compared with countries, it is less than 1.669 million tons of Brazil and higher than 1.620 million tons of Indonesia , ranking fifth.
PM2.5 calculation method is similar to NOX, which is derived from total work and emission factors. The PM unit emission of low-speed machines is about 1.25g/kWh. After multiplying by the total power of low-speed machines in 2018, the PM2.5 emissions of low-speed machines are about 1.217 million tons, accounting for 73.11% of the international shipping industry and about 2.99% of the world. Less than the 1.392 million tons of the United States, higher than 700,000 tons of Vietnam , ranking seventh by country.
-PM10
In 2018, PM10 emissions from the international shipping industry were 1.667 million tons, accounting for 2.59% of the world. If compared with other countries, it is less than the United States' 2.122 million tons and higher than Ethiopia's 's 1.221 million tons, ranking seventh.
PM10 calculation method is similar to NOX, which is derived from total work and emission factors. The unit PM emission of low-speed machines is about 1.36g/kWh. After multiplying by the total power of low-speed machines in 2018, the PM10 emissions of low-speed machines are about 1.324 million tons, accounting for 79.4% of the international shipping industry and about 2.06% of the world. %, if compared with other countries, it is less than the United States’ 2.122 million tons and higher than Ethiopia’s 1.221 million tons, ranking seventh.
CO2
In 2018, the international shipping industry’s CO2 emissions were 704 million tons, accounting for approximately 2% of the world. If compared with countries, international shipping is slightly less than Iran , higher than Germany, ranking seventh in the world.
CO2 emissions are statistically calculated in the same way as SO2. Both are determined by the molecular weight of the fuel itself. The total fuel consumption of low-speed engines accounts for approximately 68.4% of the international shipping industry. If the fuel is considered to be completely burned, then the CO2 emissions of low-speed engines are calculated to account for approximately 68.4% of the international shipping industry. 68.4% of the total, 1.37% of the world. That is about 505 million tons, less than Canada and higher than Brazil, ranking 12th by country.
N2O
In 2018, the international shipping industry emitted 97,900 tons of N2O (GWP is about 256*9.79=25.06 million tons, which is 3.4% of CO2 international shipping emissions), accounting for 1.07% of the world.If compared with other countries, it is less than Iran’s 98,200 tons and higher than Poland’s ’s 94,000 tons, ranking 19th.
refers to the calculation method of NOX and calculates N2O based on the total power and the emission factor of the low-speed machine. The N2O emission factor of low-speed machines is considered to be 0.03g/kWh. Due to the current lack of research on N2O, the actual emission situation may be more complicated. It is estimated that N2O emissions from low-speed engines are about 29,200 tons, accounting for about 29.6% of the international shipping industry and 0.32% of the world. Second only to , Sweden’s ’s 29,300 tons, and higher than Mongolia’s 27,600 tons, ranking 54th by country.
CH4
In 2018, the international shipping industry emitted 533,400 tons of CH4 (GWP is about 53.34*28=14.93 million tons, which is 2.02% of CO2 international shipping emissions), accounting for 0.14% of the world. If compared with countries, it is less than Congo 's 549,500 tons, higher than Cuba's 's 532,800 tons, ranking 89th.
International shipping CH4 emissions mainly come from methane escape from LNG low-speed dual-fuel engines and LNG medium-speed dual-fuel engines. According to IMO statistics, the number of low-speed diesel engines accounted for 38.6% in 2018, and the number of LNG-otto low-speed dual-fuel engines accounted for approximately 0.036%. , the number of LNG-diesel low-speed dual-fuel engines accounts for about 0.076%; using the total power of low-speed engines as the denominator, it can be approximately calculated that the power of low-speed diesel engines accounted for 99.711% in 2018, and the power of LNG-otto low-speed dual-fuel engines accounted for 0.093%. The power of the LNG-diesel low-speed dual-fuel engine accounts for 0.196%; based on the total power of the low-speed engine in 2018 of 9.74×1011kWh, it can be calculated that the total power of the LNG-otto low-speed dual-fuel engine in 2018 is 9.06×108kWh. The total power of the LNG-diesel low-speed dual-fuel engine is 9.06×108kWh. The total power of the machine is 1.91×109kWh. In addition, the emission per unit CH4 of the LNG-otto low-speed dual-fuel engine is about 2.5g/kWh, and the emission per unit CH4 of the LNG-diesel low-speed dual-fuel engine is about 0.2g/kWh. It can be calculated that the LNG-otto low-speed dual-fuel engine in 2018 The CH4 emissions of LNG-diesel low-speed dual-fuel engines are about 2,260 tons, and the CH4 emissions of LNG-diesel low-speed dual-fuel engines are about 0.38 million tons. Therefore, the CH4 emissions of LNG low-speed dual-fuel engines in 2018 are about 2,640 tons, accounting for 0.49% of the international shipping industry. Accounting for 0.00069% of the world. In 2018, the trend of mass application of low-speed dual-fuel engines has just begun. The number of medium-speed dual-fuel engines in use is much greater than that of low-speed engines. At the same time, the amount of methane escaped from medium-speed engines is greater than that of low-speed engines. If compared with countries, it is less than the 02,710 tons of Sao Tome and the Republic of Principe, and higher than the 02,450 tons of Seychelles , ranking 192nd.
From this, we can draw the following conclusions about the emissions of international shipping and marine low-speed machines in 2018:
. International shipping is second only to China in the total global NOX emissions, accounting for 13.4% of the world, while marine low-speed machines account for 13.4% of the world's NOX emissions. It is also second only to China in terms of total emissions, accounting for 10.8% of the world. This is the largest impact factor on global emissions from international shipping and marine low-speed machines. The following international shipping is SOX (8.58%), PM2.5 (4.09%), PM10 (2.59%), CO2 (2%), N2O (1.07%), CH4 (0.14%); the following marine low-speed machines are SOX (5.87%), PM2.5 (2.99%), PM10 (2.06%), CO2 (1.37%), N2O (0.32%), CH4 (0.00069%). It can be seen that international shipping and marine low-speed machines have a significant impact on the total global pollutant emissions, and their impact is much greater than greenhouse gas emissions;
. Marine low-speed machines are the main contributors to international shipping emissions (except CH4), especially NOX (91.8 %), PM10 (79.4%), PM2.5 (73.11%), SOX (68.4%), CO2 (68.4%), N2O (29.8%), CH4 (0.49%).
. Among the greenhouse gas emissions from international shipping and marine low-speed machines, the absolute amount of CO2 emissions reaches 739 million tons / 505 million tons. Other emissions with greenhouse gas effects such as N2O and CH4 only account for hundreds of thousands of tons, which is the entire CO2 3.4% and 2.02% of emission equivalent. The total GWP equivalent of N2O emissions is greater than CH4.
Figure 1 The proportion of international shipping and marine low-speed engine emissions in global emissions in 2018
As above, we have a panoramic image of the emissions of international shipping and marine low-speed engines in 2018. At the same time, the following is a study on the emission trends of international shipping and marine low-speed engines from 2010 to 2018.
It can be seen from the trend of all emissions that ship harmful substances and greenhouse gas emissions were at a high level before 2012, then dropped significantly in 2012, reached the lowest point in 2013, and then showed a continuous growth trend. slow.
IMO has successively formulated restriction requirements for SOX and NOX emissions around the world. In terms of sulfur oxides , on May 19, 2005, MARPOL Annex VI came into effect for the first time, requiring that the sulfur content of fuel used worldwide does not exceed 4.5%m/m; from January 1, 2012, the MARPOL Annex VI Convention officially Effectively, the upper limit of sulfur content is 3.5%m/m; starting from January 1, 2020, IMO will implement the global regulation that the sulfur content of marine fuel shall not exceed 0.50%m/m. In terms of nitrogen oxides, from January 1, 2000, IMO began to implement Tier I emission standards globally; from January 1, 2011, IMO Tier II emission standards were officially implemented. In addition, IMO has established two NOX emission control areas in North American waters and the U.S. Caribbean Sea. Starting from January 1, 2016, the diesel engines of ships traveling in these areas should meet Tier III standards.
Figure 2 Emissions of the international shipping industry from 2010 to 2018 NOX (thousand tons)
Figure 3 Emissions of the international shipping industry from 2010 to 2018 (thousand tons)
Figure 4 PM emissions from the shipping industry from 2010 to 2018 (thousand tons )
Regarding greenhouse gas emissions, they were basically at a high level before 2012, and were at a low level in 2012 and 2013, but then entered a growth trend. From 2013 to 2018, CO2 emissions increased by about 14.1%, but starting from 2016, the growth rate became obvious Slowing down, emissions in 2018 are basically the same as in 2017. N2O and CH4 also show the same trend. The only difference is that the trough of CH4 occurred in 2014. By comparing the CO2 equivalent emissions of N2O and CH4, it can be analyzed that the current CO2 equivalent of N2O is significantly higher than that of CH4. However, the current emissions of CH4 only originate from existing marine LNG engines, while N2O emissions originate from all marine engines. Therefore, As the number of LNG ships continues to increase, the greenhouse gas effect caused by CH4 emissions may gradually exceed N2O.
Figure 5 CO2 emissions from the international shipping industry from 2010 to 2018 (billion tons)
Figure 6 NO emissions from the international shipping industry from 2010 to 2018 (thousand tons)
Figure 7 CH4 emissions from the international shipping industry from 2010 to 2018 (thousand tons )
In the next article, we will completely sort out the regulations and policies on emissions and their impact on overall emissions, and introduce the technical measures and effects to deal with various emissions from marine low-speed engines.
References
.Joint Research Centre, ongoing. Database for Global Atmospheric Research. [Online] Available at: https://edgar.jrc.ec.europa.eu/dataset_ghg60.
.Global Carbon Atlas, ongoing. Country emissions. [Online] Available at: http://globalcarbonatlas.org/en/CO-emissions.
.IMO, 2020. Fourth IMO GHG Study 2020, London: International Maritime Organization (IMO).
.IMO, 2017. Black Carbon emissions and fuel use in global shipping 2015, London: International Maritime Organization (IMO).
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