TCS synthesis materials

Reply to 1# Strolling in the Clouds 1 3.2 Synthesis of hydrogen chloride 3.2.1 Properties of hydrogen chloride and principles of its synthesis Hydrogen chloride (HCl) has a molecular weight of 36.5, a density of 1.63 grams per liter, and is a colorless gas with a pungent odor. HCl is highly soluble in water; under standard conditions, 500 volumes of HCl can dissolve in 1 volume of water, second only to NH3 (700). The density of a saturated HCl solution is 1.19. Dry HCl has low corrosivity, whereas an HCl solution (hydrochloric acid) is highly corrosive. This is because, under the influence of water molecules, HCl ionizes to produce a large amount of H+, and these H+ ions can undergo displacement reactions with various substances, especially metals. Therefore, in order to prevent the equipment from being corroded by hydrochloric acid and to ensure a longer service life, dry hydrogen and chlorine should be used for the reaction. The reaction between chlorine and hydrogen is a chain reaction: Cl2 + energy —— 2Cl· + H2 —— HCl + H+ + H+ + Cl2 —— HCl + Cl-. Its reaction rate is extremely fast, and an explosive reaction occurs once a certain concentration mixture is reached. However, this reaction requires external energy to occur; at lower temperatures and in the absence of light, no intense reaction takes place even if the two are mixed in large quantities. Therefore, we must prevent the two from mixing during the synthesis process; if mixing does occur, the mixed gas should be fed into the alkali scrubber in the absence of light. We generally write the reaction between chlorine and hydrogen as follows: This is an exothermic reaction, with the temperature of the outer flame reaching 1000°C. 3.2.2 Quality specifications of synthetic raw materials – Polysilicon production imposes high requirements on the quality of raw materials; they must meet the following specifications in order to be used for the synthesis of HCl. 1. Quality specifications for hydrogen: H2 content (by mass) ≥ 99.997%; O2 content (by mass) ≤ 0.003%; dew point –60°C. 2. Quality specifications for chlorine: Cl2 content (by volume) ≥ 99.8%; water and other oxygen-containing impurities (by mass) ≤ 0.015%; nitrogen trichloride (by mass) ≤ 0.002%; residual substances (by mass) ≤ 0.015%. 3.2.3 Introduction to the main equipment for HCl synthesis. 3.2.3.1 HCl synthesis furnace: The HCl synthesis furnace is the main equipment used for producing hydrogen chloride; it consists of a furnace body and a burner (lamp disk). The furnace body is a biconical device without any internal components; it has an air outlet at the top, with 4 horizontal explosion-proof holes distributed around it, and a viewing port at the bottom. An explosion-proof membrane is installed over the explosion-proof hole; it is generally capable of withstanding a pressure 1.25 times that of the operating pressure inside the furnace, and it will rupture automatically when the pressure exceeds this level, thus providing excellent safety protection. The viewing port at the bottom of the furnace is used to observe the flame and reaction inside the furnace. The burner is the most critical component of the synthesis furnace; it consists of a double-layered tube structure, with chlorine being introduced into the inner tube and hydrogen into the outer tube. This design ensures that, even when there is a 3%–4% excess of hydrogen, the content of free chlorine in the resulting HCl remains below the specified threshold. The exit temperature of the synthesis furnace roof can reach 450°C, so it is entirely made of the high-temperature resistant 0Cr18Ni9Ti material. Furthermore, to prevent burns and the effects of explosions during synthesis, the synthesis furnace must be installed in a enclosed space isolated with concrete. 3.2.3.2 Hydrogen and chlorine buffer tanks: The flow control of the raw gases, hydrogen and chlorine, which are used to synthesize HCl, is achieved by regulating the inlet pressure and the volumetric flow rate of the gases. The buffer tanks together with the pressure regulators installed above them ensure that the pressure fluctuations of the gases entering the furnace remain below 0.01 Mpa. Due to our high operating pressure (0.5 MpaG), chlorine may liquefy in winter, resulting in insufficient pressure. Therefore, the chlorine buffer tank is equipped with a jacket through which warm water can be circulated to maintain temperature. 3.2.3.3 HCl buffer tank: Regulates pressure fluctuations between the HCl synthesis furnace and the SiHCl3 synthesis furnace. 3. 2.3.4 HCl air cooler: S-shaped tubes used to cool HCl at 400–450°C down to 120–150°C. 3.2.3.5 HCl water cooler: A shell-and-tube heat exchanger that cools HCl at 150°C to about 85°C. 3.2.3.6 HCl preheater: Heat HCl to 150°C using steam at 1.0 Mpa. 3.2.4 Process flow diagram for HCl synthesis 1—Hydrogen buffer tank ； 2—Chlorine buffer tank ； 3—HCl synthesis furnace ； 4—Safety discharge HCl buffer tank ； 5—HCl air cooler ； 6—HCl water cooler ； 7—HCl buffer tank ； 8—HCl Preheater 3.2.5 Operating Steps for HCl Synthesis The HCl synthesis furnace involves a reaction between hydrogen and chlorine; this reaction occurs at an extremely fast rate. When hydrogen mixes with air or chlorine to reach a certain concentration, ignition or exposure to light can cause an explosion. Therefore, during the operation process, we must follow the requirements step by step, and in particular, we must not violate procedures during ignition and shutdown. 3.2.5.1 Preparations before starting the machine ⑴ Check whether all system equipment, pipelines, valves, and instruments are in good condition. ⑵ Perform pressure testing and leak detection on the system; the pressure used for leak detection should be 0.6–0.8 Mpa. ⑶　System gas displacement: The buffer tank is displaced with nitrogen 3 to 4 times. Among them, the chlorine and hydrogen buffer tanks also need to be further purged with process gas, and the waste gas resulting from this purification is discharged after passing through a scrubber tower. The synthesis furnace and HCl buffer tank are first purged with nitrogen and then with air, until the explosion analysis yields a negative value. ⑷　Pressurization of buffer tanks: Once the gas displacement is complete, the chlorine and hydrogen buffer tanks are filled with chlorine and hydrogen respectively to 0.5 Mpa, and the pressure control equipment is activated. 3.2.5.2 Ignition: Before ignition, it is necessary to confirm that there is no high concentration of hydrogen in the synthesis furnace, that the purge air flow remains normal, and that the explosion analysis shows a negative value before ignition is permitted. Before ignition, it is also necessary to ensure that the pipelines from the synthesis furnace and the HCl buffer tank to the scrubber tower are unobstructed, and that the scrubber tower is in operational condition. ⑴ Manual ignition is carried out by inserting a burning igniter through the access hole; the fuel for this igniter is hydrogen. Hydrogen is introduced through the auxiliary hydrogen pipe, ignited, then the igniter is removed and the manhole is closed. Subsequently, hydrogen was gradually introduced from the burner; once the combustion stabilized, the gas supply to the auxiliary hydrogen pipe was turned off. Chlorine is introduced from the burner in an amount that is 5–10% less than that of hydrogen, and the purge air is turned off. ⑵ A dedicated pipeline is used for remote ignition to introduce an argon-monosilane mixture into the synthesis furnace, and this mixture ignites spontaneously in air. The burner supplies hydrogen; once the combustion is stable, the argon-monosilane mixture is stopped. After the argon-monosilane mixture pipe is disconnected from the synthesis furnace (via the valve), it needs to be purged with nitrogen. Chlorine is introduced into the burner in an amount that is 5–10% less than that of hydrogen, and the purge air is turned off. 3.2.5.3 Normal operation: After successful ignition, gradually increase the flow rates of hydrogen and chlorine until they reach the specified parameter values. The mass of the synthesized HCl is also measured; once the following parameters are achieved, the exhaust pipe is switched, and gas is supplied to the SiHCl3 synthesis furnace, allowing the system to operate normally and gradually transitioning to automatic control: no free chlorine present, 3–4% excess hydrogen, and an HCl flow rate of approximately 400 Nm3/h. 3.2.5.4 Shutdown ⑴ Emergency shutdown – In the event of equipment failure or ignition problems, the synthesis system must be shut down urgently. For an emergency stop, first close the vent valve of the HCl buffer tank; the system should then be switched to the exhaust gas scrubber tower. After that, quickly close the chlorine inlet valve and the hydrogen inlet valve. Next, nitrogen is introduced into the furnace at a flow rate of about 100 Nm3/h; it takes at least 30 minutes before the manhole can be opened to introduce purge air and proceed with the ignition process, or the system remains in standby mode until the fault is resolved and ignition can be attempted again. ⑵ During normal shutdown, the inlet valve of the SiHCl3 synthesis furnace is closed, and the system is switched to the exhaust gas scrubber tower. Then gradually reduce the chlorine flow rate first, followed by the hydrogen flow rate, until it is turned off (turn off the chlorine first). After the flame is extinguished, nitrogen is introduced through the hydrogen inlet pipe to purge the system, at a flow rate of 50–100 Nm3/h. After 3–4 hours, the system is sealed and set aside, or it can be purged with air instead, with the manholes opened for future use. 3.2.5.5 Fully automatic control: (1) Automatic adjustment of the pressure in the hydrogen and chlorine buffer tanks, with flow monitoring prior to entry into the furnace; (2) Two photoelectric flame detectors and an observation port are provided to detect whether the reaction is taking place inside the synthesis furnace. ⑶ Furnace temperature monitoring and alarm function ⑷ Automatic control of heater temperature ⑸ Protective interlock alarm or shutdown in case of deviations in process parameters

Reply to 2# wangli115: 3.3 Synthesis of SiHCl3: Pure SiHCl3 is a colorless, volatile, transparent liquid at room temperature; it has a strong odor, a density of about 1.33 kg/L, and a boiling point of 31.5°C. It reacts very readily with water; once it leaks, it quickly reacts with the moisture in the air, releasing large amounts of heat and HCl, which not only pollutes the environment but also poses safety risks. Careful inspection is necessary when using it. When SiHCl3 does not react fully, siloxanes are produced, which are flammable and may catch fire under impact or friction. Furthermore, when heated to above 200°C, SiHCl3 also readily reacts with reducing agents such as H2, Na, Al, and Mg. ① 2SiHCl3 + 4H2O = 2SiO2 + 6HCl + H2 ② SiHCl3 + H2 = Si + 3HCl ③ 2SiHCl3 + 2Al = 2Si + 2AlCl3 + H2 3.3.1 Principle of SiHCl3 preparation SiHCl3 is synthesized by reacting high-purity silicon powder with dry HCl in a bubbling bed; the reaction equation is as follows: As mentioned earlier, silicon powder remains stable at room temperature and reacts only with a few substances, showing almost no reaction with dry HCl. Therefore, to synthesize SiHCl3, the silicon powder must first be preheated to above 280°C. However, this reaction is exothermic; once it is initiated, no additional heat energy is required, and instead heat is removed. During the reaction of silicon powder with HCl to produce SiHCl3, other side reactions also occur, yielding various substances such as SiCl4, SiH2Cl2, and polysiloxanes. These reactions are all sensitive to temperature; at higher temperatures, the amount of SiCl4 produced increases significantly, while at lower temperatures, the production of SiH2Cl2 increases. The reactions tend to cease when the temperature drops below 260°C. Therefore, precise temperature control during the synthesis of SiHCl3 is the main means to ensure quality. ① ② During the reaction of silicon powder with HCl, the small amounts of impurities present in the silicon powder such as Ca, Fe, Al, Zn, Ti, P, B, etc., primarily form compounds like CaCl2, FeCl3, AlCl3, ZnCl2, TiCl4, PCl3, and BCl3. Most of these substances are separated out in solid form during dust removal, while only a small amount enters the condenser along with the SiHCl3 mixture and is collected in the liquid phase. Impurities at the ppm level can be removed only through distillation. Fixed-bed reactors were initially used for the synthesis of SiHCl3. We know that this reaction is exothermic, and due to the poor thermal conductivity of silicon powder, the fluid flow rate cannot be too high because it is limited by the pressure drop, which leads to difficulties in heat transfer and temperature control. There is a significant temperature gradient inside the furnace, with a highest temperature point along the axial direction. This is extremely detrimental to the selectivity of the reaction as well as to the strength of the equipment; the yield of SiHCl3 obtained through synthesis is generally only 70%. With the development of fluidized bed technology, and due to its numerous advantages, it has replaced fixed-bed reactors and become the equipment commonly used in polysilicon plants today. Due to the intense mixing of fluids and solids within the fluidized bed layer, the temperature distribution in the bed is even, preventing localized overheating. The synthesis yield can reach around 90%, and it enables continuous and large-scale production. It can be said that the application of boiling furnace technology has significantly improved the overall level of SiHCl3 synthesis. 3.3.2 Hydrodynamics principles of the SiHCl3 synthesis furnace and the structure and technical requirements of its components 3.3.2.1 Formation of a bubbling bed and hydrodynamics principles The fundamental contradiction in fluid flow is between fluid movement and resistance. A similar relationship of \"interdependence\" and \"contradiction\" in the driving forces of fluid flow exists when studying the process of fluidized bed formation and the principles of fluid dynamics. To illustrate the internal relationships in the formation process of a fluidized bed, its development can be described in four stages: the fixed-bed stage, the critical fluidization stage, the bubbling-bed stage, and the pneumatic conveying stage. Fixed-bed stage: When the flow velocity is very low, the solid particles remain stationary, with the fluid passing through the gaps between them. As the flow rate increases gradually, the position of the solid particles changes slightly, becoming more loose, but the particles remain in contact with one another. The height of the bed layer does not change either; it is merely preparing for the fluidization stage. Critical fluidization stage: As the flow rate is increased further, when the sum of the friction force generated by the gas flowing over the solid particles and the buoyancy of those particles equals the weight of the particles themselves, the bed begins to expand and become looser; the particles move to some extent, and the height of the bed also starts to increase. This is an ideal situation; it does not exist in practice. Boiling bed stage: When the gas flow rate increases above the critical fluidization velocity, significant instability occurs in the bed, with the particles within it tumbling in clusters. Continuing to increase the fluid velocity causes the volume of the fluidized bed to keep growing, but the bed volume does not become much larger than that at critical fluidization. As the flow velocity increases, the movement of the solid particles intensifies; they flip up and down, just like liquid when it is boiling. However, the movement of solids has distinct interfaces; upon reaching these interfaces, most particles fall back into the bed layer, while a few are carried away with the gas. Therefore, there is a dense phase and a dilute phase inside the reactor; the region below the interface is the dense phase, while the region above it is the dilute phase. Pneumatic conveying stage: When the gas flow velocity increases to a certain limit value, the particle carrying speed is reached, the bed interface disappears, and the entire reactor turns into a dilute phase; the solid particles are carried away from the bed along with the fluid. As the gas flow velocity within the bed layer changes, the pressure drop after the gas passes through also changes accordingly. At low flow rates (fixed-bed stage), the pressure drop is approximately proportional to the gas flow velocity. As the velocity increases, it eventually reaches a maximum value before reaching critical fluidization; this value is slightly higher than the static pressure of the bed. As the gas velocity is increased further, the fixed bed suddenly \"unlocks\", the void fraction εm rises to εmf (the void fraction of a critically fluidized bed), and the pressure drop decreases to the static pressure of the bed ； As the gas velocity increases further, the bed will continue to expand before reaching the carry-away velocity, but the pressure drop remains almost unchanged ； Once the gas velocity reaches the pneumatic conveying stage, the pressure drop increases as the flow rate rises, which is purely a problem of gas fluid dynamics. Of course, once the pneumatic conveying speed is reached, a large amount of silicon powder is lost (it is carried to the dust collector without undergoing any reaction and is discharged as waste). Therefore, an appropriate operating speed should be selected. For a specific boiling furnace reactor, it is difficult to determine an appropriate operating flow rate using traditional calculation methods, as there are too many influencing factors; therefore, manufacturers generally use experimental methods or insights gained from production experience to determine it. 3.3.2.2 Heat transfer in fluidized beds The excellent heat transfer properties of fluidized beds are based on three fundamental forms of heat transfer: A. Heat transfer between points within the bed layer: Due to the intense stirring of the particles in the fluidized bed, their turbulent mixing results in an effective thermal conductivity that is 100 times higher than that of silver. B. Heat transfer between particles and fluid: The heat transfer between solid particles and a fluid occurs mainly through convection, with the thermal resistance lying in the gas film surrounding the particles. Experiments have shown that in a fluidized bed layer, a temperature difference between the gas and solid phases exists only in a small area near the air inlet; thereafter, due to rapid heat transfer between the two phases, the bed temperature becomes very uniform, and the specific surface area of the particles is large. C. Heat transfer between the bed layer and the vessel wall: Heat transfer between the bed layer and the vessel wall is a key aspect of heat transfer in fluidized beds. In our production process, it is an exothermic reaction; the heat energy is transferred through the vessel wall to the water in the jacket, where it is carried away, thereby allowing the temperature inside the furnace to be controlled. The furnace cylinder and conical bottom of the synthesis furnace are equipped with jackets, into which water at about 90°C is circulated, allowing the wall temperature to be maintained at around 150°C. 3.3.2.3 Structure of the fluidized bed and technical requirements for its various components. A bubbling furnace consists of a separator, a cylinder, and a conical bottom; the height, diameter, and height-to-diameter ratio of synthesis furnaces with different technical requirements vary accordingly. A. The separator is an extension of the synthesis furnace; its function is to recover larger particles carried away by the airflow. The design of the separator is determined based on the particle size range to be recovered; by increasing the cross-sectional area of the container, the airflow velocity is reduced, and through a sufficient deceleration distance, the particles fall back into the furnace, thereby reducing waste. The separator is generally chosen to be 3 times the diameter of the cylinder; in our case, it is φ2.4m with a height of 4.8m. B. The cylindrical section consists of two parts; the lower part is the main reaction zone, also known as the dense phase zone. The upper section is the dilute phase zone; its function is to allow the large particles ejected during boiling to slow down and fall back into the dense phase zone, thereby acting as an auxiliary separator. The cylinder diameter is φ0.8m, and the total length is H=14m. C. The base of the cone is the air intake and feed inlet. The silicon powder continuously enters the HCl inlet pipe and is carried into the synthesis furnace, where it mixes rapidly with the silicon powder already present at the bottom of the cone, causing a rise in temperature; this does not affect the operating conditions inside the furnace. The height of the cone’s base is 1.5 m. 3.3.2.3 Heating device: Before putting the boiling furnace into use, we know that it is necessary to heat the silicon powder to a certain temperature first so that the reaction can proceed. Traditional boiling furnaces use inductive coils for heating, which complicates the structure of the reaction furnace during operation. Our current heating method involves using nitrogen for external heating, with the hot nitrogen then being used to preheat the silicon powder inside the furnace. This process takes 10 hours; it is longer and requires more electricity compared to the traditional inductive heating method, but the equipment design is simpler. 3.3.3 Technical conditions for SiHCl3 synthesis 3.3.3.1 Reaction temperature As shown in the previous analysis, the reaction between silicon powder and HCl to produce SiHCl3 is highly sensitive to temperature, and the reaction temperature has a significant impact on production. If the temperature is too low, the reaction proceeds slowly; without reaching an adequate initiation temperature, there is a risk of disrupting the reaction equilibrium inside the furnace. To maintain the reaction, it is necessary to keep the furnace temperature above 220°C. If the reaction temperature is too high, the content of SiCl4 will increase significantly. This is because it has a highly symmetric structure and excellent thermal stability; it does not undergo thermal decomposition even at temperatures up to 600°C. The molecular structure of SiHCl3 is asymmetric, and it has poor thermal stability; it begins to decompose at 400°C and decomposes rapidly at 550°C. Therefore, in order to obtain a product with a high content of SiHCl3, the temperature should be controlled between 280 and 320°C. 3.3.3.2 Effects of oxygen and moisture Oxygen and moisture are highly detrimental to synthetic reactions, as the Si–O bond is more stable than the Si–Cl bond. Oxygen that enters the system reacts with silicon to form silica gel and siloxane compounds. On one hand, this creates a dense oxide layer on the surface of the silicon powder, hindering the proper progress of the reaction and reducing the amount of SiHCl3 in the product (see figure below). On the other hand, it leads to the formation of silica gel that blocks the pipes, preventing production from continuing. Therefore, it is generally required that the water content in silicon powder be less than 100 ppmw, the water and oxygen-containing impurities in liquid chlorine be less than 150 ppmw, the oxygen content in hydrogen be less than 30 ppmw, and the dew point be below -60°C. 3.3.3.3 Control of free chlorine: Free chlorine has two main effects on synthesis furnaces: firstly, high levels pose an explosion risk, and secondly, it affects the quality of the synthesis. The control of free chlorine is achieved by maintaining a hydrogen excess of about 4% during the reaction in the HCl synthesis furnace, and by using a continuous concentration detector to monitor the quality of the synthesized HCl, thereby ensuring that the free chlorine level remains below the specified limit. 3.3.3.4 Particle size of silicon powder: The reaction between silicon powder and HCl gas takes place on the surface of silicon. A larger specific surface area of the silicon powder facilitates this reaction; therefore, it is necessary for the particle size of the silicon powder to be small. However, if the particle size is too small, a polymeric fluidized bed is likely to form during fluidization, with an abundance of bubbles that will inhibit mass transfer and reduce the primary conversion rate of HCl. At the same time, the smaller particles react rapidly and quickly reach the particle size range for removal, resulting in a low utilization rate of the silicon powder. Therefore, we generally choose silicon powder with a particle size of 10–60 mesh, achieving a conversion rate of around 93%. 3.3.3.5 Layer height and HCl flow rate: The layer height of the silicon powder layer and the HCl flow rate are important factors affecting the yield and quality of SiHCl3. A too high layer height leads to an increased pressure drop, which requires an increase in the inlet pressure accordingly. Excessively high pressure drops lead to reduced stability inside the furnace, posing a risk of the formation of \"fountains\" or \"gulfs\", and even \"pipe surges\"; all of these factors affect the efficiency of the equipment and raw materials, hindering the normal progress of production. If the material layer is too low, the unevenness of boiling increases, the contact time for the HCl reaction is reduced, and the yield decreases. The flow rate of HCl determines the fluidization state of the particle bed. The specific bed height and HCl flow rate need to be determined through production practice. 3.3.4 Schematic diagram of the SiHCl3 synthesis process flow. The synthesis system can be divided into four sections: the synthesis furnace and hopper, dry dust removal, wet dust removal, and CDI condensation, separation, and recovery. The process schematic is shown in the figure below. 3.3.5 Synthesis process of SiHCl3 3.3.5.1 Preparations before startup Check whether all the pipes, valves, equipment, instruments, electrical components in the system are in good condition, and conduct a leak test using nitrogen at a pressure of 0.6 MPaG. After ensuring that there are no leaks or blockages in the system, 2 tons of silicon powder were added to the synthesis furnace, and nitrogen at 500°C was introduced; the waste nitrogen was discharged through the cyclone separator in the hopper. After heating the silicon powder to 220°C, the system is replaced with HCl preheated to 150°C. The exhaust outlet of the synthesis furnace is switched to a dry dust removal system, and the gas is then sent to an exhaust gas purification scrubber. During this period, the system’s wet dust removal system and condensation recovery system should first be purged with nitrogen, and then replaced with pure hydrogen before being put into use. When the temperature of the silicon powder in the synthesis furnace approaches the required level, the units of these two systems also need to be started up and operated at 0% load. The temperature control system of the synthesis furnace should also start properly. 3.3.5.2 Startup of the synthesis furnace: When the flow rate of HCl entering the synthesis furnace reaches the specified value, the furnace temperature reaches 320°C, and the mass fraction of SiHCl3 is not less than 83%, it indicates that the synthesis tower has entered a stable state. At this point, the gas in the system is switched to \"wet dust removal\", and the entire synthesis system enters its normal operational mode. Once it is in normal operation, silicon powder is continuously added to the conical bottom of the synthesis furnace at an adjustable flow rate. The main technical parameters for system control are as follows: Temperature in the reaction zone: 300–330°C; Pressure at the top of the furnace: 0.15–0.24 Mpa; Pressure at the bottom of the cone: 0.2–0.45 Mpa; Maximum pressure drop in the synthesis furnace: 0.15 Mpa; Temperature of the mixed gas after dry dust removal: 100–250°C; Temperature of the mixed gas after wet dust removal: 80–90°C. 3.3.5.3 Shutdown of the synthesis furnace: To shut down the synthesis furnace, it is first necessary to stop supplying silicon powder to it, and transfer the gas mixture from the CDI system to the exhaust gas purification tower. After stopping the addition of HCl to the synthesis furnace, nitrogen preheated to 300°C was introduced for gas displacement until no chlorosilanes and HCl were present in the system. Then, the nitrogen heater is turned off, and the system is purged with cold nitrogen. Once the temperature drops to 50°C, the bottom of the synthesis tower is opened to unload the waste silicon powder into the transfer hopper. Waste silicon powder must be sent to the waste treatment facility for processing before it can be recycled.

Very detailed; the person up there is really generous – thanks for sharing so selflessly!

It is relatively detailed and comprehensive as well.

Very detailed. Worth a thumbs up!

I’ve learned it*, thank you for sharing