Selection principles for gasification technology

I think the first step is to analyze the local coal quality. Firstly, the technology must be suitable for the actual characteristics of the coal quality. Each technology has its own suitable type of coal. The three gasification methods differ in the following ways: (coal slurry method, SH method-SHELL, GSP). (1) Different feeding methods: Water-coal slurry method: Feeding is done via water-coal slurry, which is safe, easy to operate, simple, and has relatively lenient requirements regarding the moisture content of coal. SH method and GSP method: Dry coal powder is fed into the gasification furnace using high-pressure nitrogen or CO2 gas. The coal must be dried and ground into fine powder; the lower the water content of the coal, the better. Drying the coal requires a significant amount of heat. (2) Different furnace structures: In the water-coal slurry method, wear-resistant and high-temperature resistant refractory bricks are used for lining, with a typical service life of 1 to 2 years. SH/GSP method: It uses a membrane-type water wall lining, offering a longer service life. (3) The percentage of active gases (CO+H2) in the produced water gas varies. Water-coal slurry method: Water gas contains effective gases (CO+H2) ≈80%. SH method: The water gas contains effective gases (CO+H2) ≈90%. GSP method: The water gas contains effective gases (CO+H2) ≈90%. (4) Coal and oxygen consumption: Since numerous sources indicate that the composition of gas produced by the SH and GSP methods is over 90% CO+H2, while that of gas produced by the water-coal slurry method is over 80% CO+H2, many people believe that these methods can save 10% in consumption; however, this is not the case. Coal grinding and drying still require a large amount of heat energy and power consumption. Oxygen consumption: When comparing coal of the same quality, the water-coal slurry method requires 8–10% more oxygen compared to the SH method and the GSP method. (5) Impact on subsequent processes: As mentioned earlier, the CO content in SH gas is as high as 60%, which **increases the load on the conversion process; simultaneously, 85% of the steam generated as a by-product must be added to meet the requirements of this conversion process. Water-coal slurry quenching process and GSP quenching process. Water-coal slurry: CO content of about 45% ； GSP: The CO content is 60%, and its gas is saturated with water vapor; the water vapor ratio is approximately 1.1–1.5, which is sufficient to meet the requirements of the shift reaction for water vapor. Moreover, the process design allows for smooth operation despite the presence of sulfur compounds. (6) Different heat recovery methods: the water-coal slurry method and the GSP method – heat can be recovered indirectly using waste boilers, or directly through quench chambers; the choice depends on the type of product to be produced. For example, quench chambers are generally used in the production of synthetic ammonia, methanol, and hydrogen products for direct recovery, which can save a significant amount of investment. SH method: It is the only way to indirectly recover heat from waste boilers, with no alternative options. Due to high investment costs, stringent material requirements, great manufacturing difficulties, and complex operation procedures, it is not very suitable for projects involved in the production of methanol and carbon-based chemicals. (7) Differences in equipment investment: For the water-coal slurry method, there are two processes: the waste boiler process and the quenching process. Based on available information, under the same production scale, the investment required for the waste boiler process is generally about 50% or more higher than that for the quenching process. Therefore, to save on investment, whether producing synthetic ammonia or chemical products such as methanol, the quenching process is generally the preferred option to reduce costs. GSP method: Due to the complex structure of the gasification furnace, the investment is higher than that of water-coal slurry. SH method: Due to factors such as the use of a waste boiler process, complex structure, high requirements, and difficulties in manufacturing, it can be said that its investment is definitely much higher than that of the water-coal slurry gasification quenching process for the same production scale. Based on the available information we have, for projects of exactly the same scale, the investment required for the SH method is approximately 2 times that of the water-coal slurry quenching process. Based on the above data, it can be seen that with Shell’s gasification technology, high capital costs for the installation lead to increased production costs. The lack of operational experience, along with the absence of backup units, results in complex operation and poor production stability, which in turn reduces profitability and prolongs the payback period. Of course, what the brave brother upstairs said is also correct. We are looking at things from different perspectives. I’m just sharing my views here; if there’s anything incorrect in what I say, I hope everyone will point it out. At the same time, I’m putting forward some ideas here to stimulate further discussion. Awaiting insights from experts. This post was last edited by Hada on 2007-11-9 at 16:17.]

　　After reading it, I have some reservations: although various sources state that the composition of gas produced by the SH and GSP methods consists of over 90% CO+H2, and that the composition of gas produced by the water-coal slurry method is also over 80% CO+H2, many people believe that these methods can save 10% in terms of energy consumption; however, this is not the case. Coal grinding and drying still require a large amount of heat energy and power consumption. The composition of gas produced by the water-coal slurry method, in terms of CO+H2, is 80%; whereas for the SH method and GSP method, this proportion reaches 90%. These figures refer only to the composition of the gas, not the total amount of gas produced. Only when the total amount of gas produced per ton of coal is the same can it be said that the SH method and GSP method save 10% in terms of resource usage. In reality, the amount of gas produced per ton of coal using the water-coal slurry method is higher than that produced by the SH method and GSP method; therefore, these methods do not achieve a 10% savings. Strictly speaking, a comparison should be made based on the amount of usable gas produced per ton of coal. Reports on actual use show that no such 10% savings are achieved. Additionally, the SH method still requires a large amount of heat energy and power to dry the coal, as well as a small amount of superheated steam – facts that patent holders often avoid mentioning. Users should be aware of this

There is a lot of information on such issues in forums. In my opinion, the final decision should be based on a comprehensive technical and economic evaluation. Here, I will briefly outline a few aspects that need attention; for more in-depth information, one can refer to relevant materials: 1. The origin and suitability of the coal type； 2. The advancement of technology is also reflected in energy consumption metrics ； 3. Reliability of the technology ； 4. Depending on the gas composition requirements of different products, it is necessary to \"adapt measures to local conditions\"” ； 5. Project construction investment. 6. Conduct a comprehensive analysis of the advantages and disadvantages of each technology; do not follow trends blindly. For example, although SHELL has many advantages, the fact that it does not have backup furnaces means that the longest continuous operating period for the five units in use in China is only around 60 days, which is a matter that requires careful consideration. Although TEXACO’s investment is lower, it is significantly inferior to SHELL in terms of oxygen consumption, cold gas efficiency, and effective gas composition. In short, my view remains that there is no universal choice – only the one that is best suited to oneself.

In terms of current gasification technologies, the wet gas flow bed represents a stable and advanced technology. Although dry gasification offers good performance metrics, it is complex to control, unstable, and lacks industrial implementation experience. Personally, when choosing a gasification method, one should opt for a mature and stable technology; dry gasification systems should not be used as experimental platforms.

What was said upstairs is quite comprehensive. There are many specific factors that influence the choice, and numerous elements need to be taken into consideration; it’s difficult to achieve perfection. One can only make a comprehensive comparison and select a process that offers a lower overall investment, uses relatively mature production technologies, has gas composition that matches subsequent demands, and allows for the recycling or proper treatment of the three types of waste generated during production at minimal cost, so as to meet emission standards.

The quality of gasification technology largely determines whether the entire system can operate for long periods of time in a safe and stable manner, as well as the cost-effectiveness of the products. Therefore, choosing new coal gasification technologies that feature high reliability, high efficiency, low energy consumption, and low pollution – namely, \"two highs and two lows\" – is a prerequisite and foundation for the development of modern coal chemical industry. 　　Principle of advancement. The advancement of process technology determines a project’s market competitiveness; the proposed project should make use of advanced and high-tech solutions to achieve leadership at the domestic level, and to approach or even exceed international standards. When choosing gasification technology, enterprises should thoroughly study the current status and development trends of such processes, as well as determine whether there are more advanced technologies available and their feasibility of adoption, in order to ensure the competitiveness of the project. The advancement of technology should be reflected primarily in several aspects such as product quality and performance, process level, and equipment standards. 　　Principle of applicability. There are too many types of coal in our country, so when choosing gasification technology, adaptability must be taken into account. Enterprises should select an appropriate coal gasification process based on actual conditions such as the quality and type of coal available locally and the source of water, while also taking into account some of the raw materials that may be purchased, as well as auxiliary materials. 　　Furthermore, the choice of gasification technology must also be determined in conjunction with the downstream products. The production of different products such as synthetic ammonia, methanol, or coal-to-oil fuels imposes varying requirements on the composition of the syngas, its purification, and even its pressure level. When choosing gasification technology, enterprises should select an appropriate and advanced production process based on the products to be produced and the scale of production. 　　Principle of reliability. Reliability is the guarantee for the long-term, full-load, safe, and stable operation of technology, and it also extends the service life of nozzles and linings. The technologies chosen by enterprises should have a track record of successful industrial application in the coal chemical industry; their production and operation techniques must be mature and reliable, ensuring satisfactory technical performance, product quality, and production capacity. Generally, technologies that have been thoroughly tested and are already in use should be adopted. 　　Principles of safety and environmental protection. The inherent properties of coal determine that the coal chemical production process generates large amounts of coal powder, coal ash, cinder, coal water, and waste gases, some of which are quite difficult to handle. When selecting technologies, enterprises should put people first; the process technologies chosen should ensure safety and enable clean production, minimizing the emission of waste materials. 　　Principles of intellectual property security. Attention should be paid to the origin of the process technology and the owners’ equity. Regarding patented technologies, industrial property issues should be studied, including their scope of use and validity period.

Everything must be considered based on the actual situation; different needs require different approaches, and it’s not possible to generalize. However, too many monitoring points lead to a high failure rate, which affects production and results in significant losses; isn’t it precisely because of the high failure rates and high costs associated with downtime that many companies struggle to survive? Is practicality and reliability key?

The choice of gasifier depends first on what you produce: synthetic ammonia, methanol, electricity generation, city gas, chemical raw materials, etc. Every type of gasifier has its advantages as well as its limitations； Secondly, regarding the raw material, it is best to use local coal, as it is inexpensive, easily available, and can be used over a long period of time ； Then looking at investment, it’s better to use domestic technology; foreign equipment is expensive, and the transportation of spare parts is difficult, which inadvertently increases operating costs ； Finally, consider the advancement of technology and the maturity of the manufacturing process. In short, when choosing a vaporizer, it is necessary to conduct thorough research and make careful comparisons before finally deciding on the model to select.

The mature gasification technology is still coal water slurry gasification technology. I hope to communicate with Haiyou, whose equipment uses GE and four-nozzle technology.