I want to learn *vaporization; could the university help provide some learning materials?

Chapter 1 Basic Concepts Section 1 Coal I. Concept of Coal Coal is a macromolecular organic compound formed from ancient plants. Large quantities of ancient plant remains, under the action of prolonged biochemical processes as well as geothermal and high-temperature conditions, cause carbon, hydrogen, and oxygen in these plants to be gradually released in the form of carbon dioxide, water, and methane. This results in plant material that contains more carbon and less oxygen, which then undergoes coalification to form coal. II. Classification of coal All components of coal-forming plants contribute to the formation of coal. Different types of coal are formed due to varying coal-forming plants and degrees of coalification. There is peat (not suitable as an industrial raw material), lignite, bituminous coal, and anthracite. III. Composition of coal: The organic matter in coal is primarily composed of five elements—carbon, hydrogen, oxygen, nitrogen, and sulfur—with carbon being the main element. The carbon content in coal increases as the degree of coalification increases. Young lignite has a low carbon content, bituminous coal follows, and anthracite has the highest. The hydrogen and oxygen contents decrease as coalification progresses ； Lignite is the highest, anthracite is the lowest, and bituminous coal is in between. The nitrogen content in coal remains relatively constant. Sulfur varies significantly depending on the type of coal-forming plants and the coal-forming conditions, and it has little relation to the degree of coalification. The modern concept holds that the macromolecules of coal are composed of several structurally similar basic structural units bonded together by bridge bonds. The basic unit consists of a condensed aromatic core as its main structure, while the non-aromatic parts of the unit include heterocycles, hydrogenated aromatic aliphatic groups, oxygen-containing functional groups, and alkyl side chains. Coal does not have a uniform molecular formula or molecular weight. Therefore, the properties of coal cannot be described in the same way as those of a single compound. The moisture and ash content in coal affect its use. In addition to being related to coal-forming conditions, moisture and ash content are also affected by factors such as mining, storage, and transportation. When coal is heated to a certain temperature, volatile substances such as gases and tar are released; after deducting the moisture content, this constitutes the volatiles of the coal. Volatile matter is an important indicator of coal, as it is related to the degree of coalification; the volatile matter content in lignite can be over 35%. Volatile matter and carbon content are related to the composition and properties of organic matter. It is difficult to directly determine the organic matter in coal. However, by conducting industrial and elemental analyses on coal, along with other property measurements (such as calorific value, caking property, vitrinite thickness, reactivity, etc.), it is possible to gain a basic understanding of the coal’s properties and to determine its type as well as the effectiveness of its processing and utilization. Table (1–2) lists the industrial analysis and elemental analysis data of the coal used by this plant. The moisture and ash content of coal vary greatly, and the analysis results for the same type of coal differ significantly when expressed using different benchmarks. The benchmarks used for current coal analysis in China and their values are shown in the table below. Table 1-1 Current coal analysis benchmarks in China: Sample basis, Application basis, Air-dried basis, Dry basis, Dried ash-free basis, Dried mineral-free basis. Representative symbols: ar, ad, d, daf, dmmf. Relationships among China’s coal benchmarks: Mt, C, H, O+N, St, A, Mf, Minh, So, Sp, Ss, dmmf, daf, d, ad, ar. In the table: Mt – Total moisture, % ； Mf——external water, % ； Minh——Internal water, % ； St——Total sulfur in coal ； So——organic sulfur, % ； Sp——Sulfur in iron sulfide, % ； Ss——Sulfate sulfur, % ； C, H, O, N — represent carbon, hydrogen, oxygen, and nitrogen elements in coal respectively ； A — Ash content in coal, % ； Common elemental analyses of various types of coal: Tables 1–2 show the industrial and elemental analysis of the coal used in our plant. Component, Type: Wood, Peat, Lignite, Low-sulfur coal, Bituminous coal, Semi-bituminous coal, Semi-anthracite coal, Anthracite coal. Moisture: 56.70, 34.55, 24.28, 3.24, 2.03, 3.38, 2.80. Volatile matter: 26.14, 35.34, 27.63, 27.13, 14.47, 8.47, 1.16. Fixed carbon: 11.17, 22.91, 44.84, 62.52, 75.31, 76.65, 88.21. Ash content: 5.99, 7.20, 3.25, 7.11, 8.19, 11.50, 7.83. Sulfur: 0.64, 1.10, 0.36, 0.95, 2.26, 0.63, 0.89. Hydrogen: 6.25, 6.33, 6.60, 6.14, 5.24, 4.14, 3.58, 1.89. Carbon: 49.50, 21.03, 42.40, 55.29, 78.00, 79.97, 78.43, 84.36. Nitrogen: 1.10, 1.10, 0.57, 1.07, 1.28, 1.26, 1.00, 0.63. Oxygen: 43.15, 62.91, 42.13, 33.90, 7.47, 4.18, 4.85, 4.40. IV. Ash content: The chemical composition and properties of ash (A): Ash in coal refers to the residue that remains after all combustible substances in the coal have been completely burned, and after complex reactions such as decomposition and combination occur to the minerals present in the coal at high temperatures. They are oxides and salts of metals and non-metals; the most common ones include carbonates such as those of calcium, magnesium, and iron, silicoaluminates such as those of potassium and magnesium, silicates of calcium, aluminum, magnesium, sodium, and potassium, sulfates (gypsum), sulfides (pyrite, etc.), table salt, and ferrous oxide. Based on the different origins of the minerals in coal, they can be divided into three categories. Inherent minerals: Minerals contained within the coal-forming plants; their concentration in coal is not high. Secondary minerals: These are minerals that gradually enter the coal from the outside during the coal-forming process, and their content in coal is generally not high. Exogenous minerals: These minerals were not originally present in the coal seams; they are formed from the ore in the roof, floor, and intercalated strata that get mixed into the coal during coal mining. This mineral can be removed relatively easily through washing and separation. Ash is formed during coal combustion in the following way: Clays, gypsum, etc. lose water: SiO2•Al2O3•2H2O ——→ SiO2•Al2O3 + 2H2O; CaSO4•2H2O ——→ CaSO4 + 2H2O. Carbonates decompose when heated, releasing carbon dioxide: CaCO3 ——→ CaO + CO2↑; FeCO3 ——→ FeO + CO2↑. Ferrous oxide is oxidized to form ferric oxide: 4FeO + O2 ——→ 2Fe2O3. Pyrite is oxidized to produce sulfur dioxide and ferric oxide: 4FeS2 + 11O2 ——→ 2Fe2O3 + 8SO2. At high temperatures, some of the SO2 generated by the oxidation of pyrite can remain in the coal ash and combine with calcium. For example, it reacts with CaCO3 in coal or CaO in ash with oxygen to form calcium sulfate; the reaction equation is as follows: 2CaCO3 + 2SO2 + O2 → 2CaSO4 + 2CO2↑. V. Ash melting point The fusibility of coal ash is an important indicator that is closely related to its chemical composition, and it is conventionally expressed in terms of the ash melting point. In fact, this mixture does not have an exact melting point; it only has a range of melting temperatures. Common methods for determining the fusibility of coal ash include the melting point method (pyramidal method, high-temperature thermomicroscopy method) and the melting curve method. But most use the pyramidal method as the standard approach. Coal ash and dextrin are mixed to form pyramids of a certain size, which are then placed in a special ash fusion point determination furnace and heated at a specific rate. The deformation of these pyramids is observed and recorded in order to determine the melting point of the ash. The temperature at which the gray cones begin to deform when heated to the point where their tips slightly melt and start to bend or their edges become rounded is the initial deformation temperature T1(DT) (1000°C in our factory) ； Continue heating until the cone bends such that its tip touches the backing plate, and the cone becomes spherical or hemispherical with a height ≤ the diameter of its base; at this point, the softening temperature T2 (ST～HT) is reached (1060～1120°C in our factory) ； Finally, when the ash cones are completely melted and have high fluidity, spreading into a thin layer, the flow temperature or melting point T3(FT) of the ash is reached (1170°C in our plant). The gray cone melting characteristics of T1, T2, and T3 are shown in the figure. Generally, the temperature range from T1 to T2 is considered the softening range of coal ash, while the temperature range from T2 to T3 is referred to as the melting range of coal ash. Fixed-bed and fluidized-bed (boiling-bed) gasifiers typically use the softening temperature T2 of coal ash as the main indicator for assessing its melting properties, whereas gas-flow-bed gasifiers use T3 as the primary indicator. Generally, they can be divided into four groups based on the melting temperature T3 of the ash, namely: easily fusible ashes with a melting point ≤ 1100℃ ； Moderate melting ash, with a melting point of 1100–1250℃ ； Refractory ash, with a melting point of 1250–1500℃ ； Fusible ash, with a melting point of over 1500°C. In addition to accurate testing, the range of the ash fusion point can also be roughly calculated using the following formula. Ash melting point (softening point): T = 19Al2O3 + 15(SiO2 + Fe2O3) + 10(CaO + MgO) + 6(Fe2O3 + Na2O + K2O); the molecular formula indicates the percentage content of ash, with the percent sign removed. In fixed-bed gasifiers, feed materials with a low ash melting point tend to melt and clog, affecting gas flow distribution. It also reduces the contact area between the gasifying agent and the fuel, which is unfavorable for gasification; therefore, raw materials with high melting points must be used. In contrast, fluidized bed gasifiers require a low ash melting point, as liquid slag is discharged. The normal operating temperature is T3+50～100℃. Table 1–3 Melting points of various mixtures in ash Components Melting point/°C Components Melting point/°C Components Melting point/°C SiO2 crystals 1710 2FeO•SiO2 1065 CaO•SiO2 1540 Al2O3•SiO2 1850 CaO•FeO•SiO2 1100 CaO•Al2O3 1500 VI. Viscosity-temperature properties The viscosity-temperature properties of slag refer to the relationship between the viscosity of molten slag and temperature. The operating limit for liquid slag discharge in a fluidized bed should be such that the viscosity of the molten slag is less than 25 Pa•S (250 P). It is generally believed that the viscosity of the molten slag should be kept below 1 Pa•S (250P); if it exceeds 10 Pa•S (250P), it is necessary to consider adding fluxes. Adding CaO or Fe2O3 to water-coal slurry can improve the viscosity-temperature properties of the molten slag, as CaO acts as an oxidizing agent in the ash slag, disrupting the formation of silicon polymers and thereby reducing the viscosity of the liquid molten slag. However, when the CaO addition exceeds 30%, the range within which the molten slag can flow smoothly decreases, and the viscosity of the molten slag increases as the GaO addition increases. This is because, after adding a large amount of CaO, the amount of calcium orthosilicate with a high melting point (melting point of 2130°C) in the slag increases, thereby raising the melting point of the slag. Therefore, the amount of additive added should not be too high; it should be determined through experimental firing using different types of coal. Section 2: Water Coal Slurry I. Concept of Water Coal Slurry Water coal slurry is a solid-liquid suspension formed by dispersing pulverized coal in an aqueous medium. To improve the technical and economic efficiency of water-coal slurry gasification, it is necessary to first produce coal slurries with a high solid content, low viscosity, good pumpability, and excellent stability. In water-coal slurry, the diameter of solid particles is mostly greater than 20 μm, resulting in a coarse dispersion system; it is also an uneven and dynamically unstable system with issues related to gravitational sedimentation. Especially at low flow rates or when at rest, due to the effect of gravity, the system changes over time, resulting in the coal-water suspension being divided into an upper layer with low concentration (or water) and a lower layer with high concentration (or sediment). Under the action of external forces (such as vigorous stirring), the interface layer gradually disappears, allowing a more uniform and stable solid-liquid suspension system to be formed again. This phenomenon is known as thixotropy. A notable characteristic of Newtonian fluids is that their viscosity does not change with variations in shear rate (stirring speed). One of the important characteristics of water-coal slurry is that its viscosity is not a constant value; it changes depending on the velocity gradient (shear rate, stirring rate). Compared to pure water, which is a Newtonian fluid, this clearly deviates from Newton’s laws; therefore, water-coal slurry is a non-Newtonian fluid. (The schematic diagram showing the variation of water-coal slurry viscosity with concentration is as follows:) II. Particle size distribution of coal and its control For a given type of coal, the concentration of the water-coal slurry depends primarily on the particle size distribution of the coal and the use of additives. For the particle size distribution of pulverized coal, the following empirical correlation formula proposed by Rosin and Rammler in the 1930s is currently mainly used. In the formula: R —— the weight fraction of coal particles larger than the specific particle size or sieve opening ； x —— sieve pore size, μm ； 1μm = 10-6m; b or x0 and n are constants. Taking the quadratic logarithm of the above equation yields the following linear equation. Obviously, n is the slope of the line, while b or x0 can be determined from the y-intercept of the line at the axis when 1nx = 0. Differentiate the original expression ； Thus, we obtain: This is the equation for the particle size distribution curve of coal powder. III. Use of additives The use of additives is more practical than controlling the particle size ratio; additives can significantly reduce the viscosity of water-coal slurry or increase its concentration. The function of the additive is to increase the hydrophilicity of the coal particles, forming a water film on their surface; this facilitates relative movement and improves the fluidity of the coal slurry. However, the addition of additives often affects the stability of the coal slurry. In the actual production process, adding two types of additives at times can achieve both the goal of reducing viscosity and maintaining stability. (2) Texaco water-coal slurry gasification: The Texaco gasification process was introduced in 1978 as the second generation of coal gasification processes in the world. Its technical features include a wide range of compatibility with different types of coal, no strict requirements regarding the activity of the coal, although there are certain requirements regarding the ash fusion point of the coal (which generally needs to be below 1400°C) ； Large production capacity per furnace ； High carbon conversion rate, with no pollutants such as tar or phenols in the wastewater ； The gas quality is good, with the effective gas content (CO+H2) reaching around 80%, and a low methane content, making it suitable for use as syngas. The Texaco gasification process has been put into operation at multiple plants in China, including those in Lunan, Weihe, Shanghai Sanlian, Huainan in Anhui, Shenmu, and Jinling, offering extensive production experience. The coal feeding rate per furnace ranges from 360 tons/day to 2,000 tons/day, while the gasification pressure ranges from 2.6 MPa to 8.5 MPa. The syngas produced is used for manufacturing synthetic ammonia, methanol, acetic acid, and for power generation. Through the construction of these Texaco gasification units, China has accumulated extensive experience in areas such as design, equipment manufacturing, construction, and operational management. With the exception of some key imported equipment, most of the equipment can be manufactured domestically, resulting in a high degree of localization. The Texaco water-coal slurry gasification process has the following advantages and disadvantages. 1. The coal types that can be used are quite diverse; in theory, any solid fuel can be gasified, such as various types of coal, petroleum coke, and residues from coal liquefaction. However, from an economic perspective, the Texaco process is most suitable for gasifying young bitcoals with low ash content and low ash melting points. Generally, it is not appropriate to use this process for lignite, as it is difficult to convert it into a slurry. 2. The process is flexible, and the quality of the syngas is high (CH4 < 0.1%, free of olefins, higher hydrocarbons, tar, alcohols, etc.). The product gas can be used for chemical synthesis, hydrogen production, and combined cycle power generation. 3. The coal water slurry feeding is simple and reliable, the process flow is straightforward; the gasification pressure can reach up to 6.5 MPa, enabling large-scale operation. Abroad, a single furnace can handle up to 1,800 tons of coal per day, which corresponds to 1,200 tons of synthetic ammonia produced per day. 4. It does not pollute the environment, and the treatment of waste materials is relatively simple. 5. Computer-controlled and optimized operation of the process is achievable. 6. The main drawback is high oxygen consumption, approximately 0.38–0.45 m3 (standard) per m3 (standard) of (CO + H2). 7. Another drawback is the high gasification temperature (T3 + 50°C), severe abrasion, high requirements for refractory materials on the fire-facing side, and high cost. (4) Texaco’s water-coal slurry gasification: In Texaco’s water-coal slurry gasification process, the combustion chamber is lined with refractory bricks, and the coal stays in the combustion chamber for a short period of time. Moreover, a high ash content in the coal accelerates scaling in the ash-water system, affecting the long-term operation of the system. To achieve a longer operating cycle, higher gas production, lower oxygen and coal consumption, as well as a longer service life for the refractory bricks, the coal needs to have high reactivity, high volatiles, low ash content, low moisture content, and an appropriate ash fusion point; meanwhile, it should also have good slurry-forming properties ； To protect the gas purification catalyst, it is desirable for the harmful substances in coal (sulfur, phosphorus, arsenic, chlorine) to be as low as possible ； Due to the limitations imposed by the ash melting point, the coal used for water-coal slurry gasification by Texaco has a narrower range of suitability compared to the coal used for dry coal powder gasification by Shell. The new (multi-nozzle) water-coal slurry gasifier is similar to Texaco’s water-coal slurry gasifier in terms of process, and it has the same requirements regarding coal quality. Chapter 3 Pressurized Gasification of Water-Coal Slurry I. Gasification Process There are two processes for coal slurry gasification: the quenching process and the waste heat boiler process. The waste heat boiler process can generate high-pressure steam, but due to the high temperature of the gasified product and the large amount of coal slag present, it causes abrasive wear on the waste heat boilers; as a result, high-quality materials are required for these equipment, and the initial investment as well as maintenance costs are relatively high ； The quenching process involves cooling the gas with water inside the gasifier, simultaneously removing dust; the gas exiting the gasifier contains a large amount of water vapor, and no additional steam is added in the shift unit ； Due to the lower temperature of the gas exiting the gasification furnace, the investment in gasification equipment is reduced, and maintenance requirements are minimized ； This project adopts a quenching process for gasification. II. Gasification Pressure: The pressurized gasification pressure for coal slurry can be 2.8 MPa, 4.0 MPa, or 6.5 MPa. There is operational experience with large-scale installations for all three vaporization pressures. Coal slurry gasification is carried out at a pressure of 6.5 MPa(G). Due to the high gasification pressure, the pressure of the syngas after purification remains at 5.7 MPa(G), which is exactly suitable for the pressure required in low-pressure methanol synthesis; thus, no pressure increase is needed for the syngas. This results in a 30% reduction in energy consumption compared to compressors used in methanol production at 4.0 MPa, which is why a gasification pressure of 6.5 MPa was chosen for this project. III. Specifications of the gasification furnace: The furnace comes in two specifications, φ3.2x12.2m and φ2.8x12.2m, which can be selected based on the scale of the syngas production. With a daily coal handling capacity of 2,712 tons, three φ3.2m gasifiers are selected, operating in two units with one as a backup. Each gasification furnace can process 1,500 tons of coal per day, with a maximum capacity of 2,000 tons, offering a 30% increase in production capacity. If a φ2.8 gasification furnace is used, four units are required for operation with one as a spare; not only is no cost savings achieved, but the investment is estimated to be about 20% higher as well. Section 1: Gasification Theory I. Reaction Mechanism in Fluidized Bed Gasification The reaction mechanism of water-coal slurry in fluidized bed gasification is similar to that in heavy oil gasification; that is, three types of chemical reactions occur within the flame. 1. Volatile matter combustion and gasification reactions: mn+(m+) == m+ (2–1); mn+ == m+ (2–2); mn+m = m+ (m+) (2–3); mn+m == 2m+ (2–4).
2. Carbon combustion and gasification reactions: + == (2–5); + == (2–6); + == + (2–7).
3. Equilibrium reactions of water gas: + == 2 (2–8); + == + (2–9).

II. Chemical equilibrium in gasification reactions
1. The law of mass action and its effect on chemical equilibrium: According to the law of mass action, the equilibrium constant expressed in terms of the partial pressures of various gases is given by the following formula. Let the reaction equation be as follows: then the equilibrium constant is given by: where PA, PB, PC, and PD are the partial pressures of the gas components A, B, C, and D respectively. The effect of temperature on the equilibrium constant can be expressed by the following equation. (Isobaric reaction) Where: Qp — the heat of reaction under isobaric conditions. As can be seen from the equation, if the reaction is endothermic, then Qp0 is positive; the value of the equilibrium constant increases as the temperature rises, meaning that as the temperature goes up, the equilibrium shifts in the direction of the endothermic reaction. If the reaction is exothermic, then: Qp>0 or