gas generator

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Gas generators. The main types of fuel used in industry today are solid fuels, liquid fuels, and gas fuels. From an international development perspective, the use of gaseous fuels is becoming increasingly widespread. Gaseous fuel is generally referred to as gas. Based on their method of production, they can be divided into two main categories: natural gas and synthetic gas. In natural gas, there are gas from wells drilled underground, mine gas, gas produced alongside oil extraction, and natural marsh gas, among others. In synthetic gas, the main types are coke oven gas, generator gas, and liquefied petroleum gas. Producer gas is also a type of gaseous product obtained through a thermal processing of solid fuels (coal or coke). This process involves passing oxygen and oxidizing agents (such as steam and carbon dioxide) through a layer of hot solid fuel (coal or coke), where the organic substances undergo oxidation to produce gases including oxygen, carbon monoxide, and methane. Other substances introduced in this process are known as gasifiers, and the gas resulting from this gasification is producer gas. Gasifiers can be classified into the following three types: 1. Air gasifier: uses air as the gasifying agent. II. Water gas: Uses steam as the gasifying agent. III. Mixed gas: Using air and water vapor as gasifying agents. The generator sets designed and manufactured by our factory are gas generators that use a mixture of air and water vapor as gasifying agents. Due to its reasonable gasification principle, simple equipment, low investment, convenience and safety in use, as well as easy operation and maintenance, it is easier to master, making it more suitable for small and medium-sized factories. In a typical gas generator, coal moves from top to bottom, while the gasifying agent moves from bottom to top in a counter-current manner; chemical reactions and heat exchange occur between them. In this way, several zones are formed in the gas generator, which we generally refer to as “layers”. 　　Following the sequence of the gasification process within the gas generator, its interior can be divided into six layers (see the schematic diagram of the mixed gas generator structure): 1) Ash layer ； 2) Oxide layer (also known as fire layer) ； 3) Reduction layer ； 4) Dry distillation layer ； 5) Drying layer ； 6) Empty layer ； Among them, the oxidation layer and the reduction layer are collectively referred to as the reaction layer, while the carbonization layer and the drying layer are collectively referred to as the coal preparation layer. 　　(1) Ash layer: Ash is produced as a result of coal combustion, forming an ash layer that is located at the very bottom of the shaft furnace, covering the grate. Its main functions are: a) to protect the grate and air caps from being damaged by the high temperatures of the oxide layer ； 　　b Preheat the gasifying agent; after entering from the bottom of the furnace, it first passes through the ash layer for heat exchange, which lowers the temperature of the ash layer while raising the temperature of the gasifying agent. Typical gasifiers can preheat to around 300-450°C. 　　The c ash layer also serves to distribute the air, ensuring that the gasifying agent entering the furnace is distributed as evenly as possible. 　　(2) Oxidation layer: Also known as the combustion layer (fire layer). The oxygen in the gasifying agent rising from the ash undergoes intense combustion with carbon to produce carbon dioxide, releasing a large amount of heat. It is one of the main areas in the gasification process, and its primary reaction is: C+O2→CO2+97,650 calories. The thickness of the oxidation layer is generally 3-4 times that of all the fuel blocks, usually ranging from 100 to 200 millimeters. The temperature of the gasification zone is generally lower than the ash fusion point of coal, and is kept around 1200°C. 　　(3) Reduction layer: Above the oxidation layer is the reduction layer. Red-hot carbon has a strong ability to seize oxygen from oxides and combine with it, so in the reduction layer, carbon reduces carbon dioxide and water vapor into carbon monoxide and hydrogen. This layer is thus named the reduction layer. Its main reactions are as follows:
CO + C → 2CO + 38,790 calories
H2O + C → H2 + CO + 28,380 calories
2H2O + C → CO2 + 2H2 + 17,970 calories
Since the reduction layer lies above the oxidation layer, it receives a large amount of heat from the rising gases; as a result, its temperature is relatively high, ranging from 800 to 1,100°C. This high temperature provides the conditions necessary for the reduction reactions that require heat absorption. Strictly speaking, the reduction layer can be further divided into a first and a second layer; the area with a higher temperature at the lower part is referred to as the first reduction layer, where the temperature ranges from 950–1100°C, and its thickness is around 300–400 millimeters ； The second layer is at a temperature between 700–950°C, and its thickness is 1.5 times that of the first reduction layer, approximately 450 millimeters. 　　(4) Carbonization layer: The carbonization layer is located above the reduction layer. As the gases rising from the reduction layer lose heat, their temperature gradually decreases. Therefore, the temperature in the carbonization layer ranges from 150 to 700°C. At these temperatures, the coal undergoes a process of low-temperature carbonization; the volatile components in the coal break down to produce substances such as methane, olefins, and tar. When heated, these substances turn into vapor, forming gas which then escapes through the upper drying layer, thus becoming part of the coal gas. The height of the carbonization layer varies depending on the volatile content in the fuel and the operating conditions of the gas furnace, generally being >100 millimeters. 　　(5) Drying layer: The drying layer is located above the dry distillation layer, that is, on the surface layer of the fuel. The rising hot gas meets the fuel that has just entered the furnace in this layer, where heat exchange takes place; the moisture in the fuel evaporates as a result of the heat. It is generally believed that the drying temperature ranges from room temperature to 150°C, and the height of this layer also varies depending on different operating conditions; there is no relatively constant layer height. 　　(6) Empty layer: The empty layer is the area above the fuel layer, the free space within the furnace, and its main function is to collect gas. Some comrades believe that while the gas stays in the empty space, and when the temperature inside the furnace is high, some side reactions occur, such as the decomposition of CO and the release of some carbon black: 2CO→CO2+C, as well as 2H2O+CO→CO2+H2. From this brief description, it can be seen that the gasification process taking place inside the gas generator is quite complex, involving not only gasification reactions but also processes of carbonization and drying. Moreover, in actual production blast furnaces, the stratification is not very strict; adjacent layers often overlap each other, and the temperature across different layers gradually changes, making it difficult to draw clear boundaries. The variations in the gas composition within each layer are even more complex, and even in specialized research, opinions vary. Structure of gas stoves: There are various structural types for fixed-bed gas stoves, which are described below by different components: 1. Coal feeding device: Intermittent coal feeding cover ； double bell ； Vibrating coal feeder ； Tooth-turning coal feeder. 2. Furnace structure: pressure-rated full water jacket ； Semi-water jacket ； No water jacket (refractory lining) ； Atmospheric pressure, full water jacket. 3 Grates: Pagoda shape ； Steel section welding type. 4 Gray disc transmission structure: tooth-shifting type ； Worm and worm gear type. Our company produces gas stoves in various styles for users to choose from. (See the simplified diagram of the mixed gas generator): Table of gas composition and calorific value for several common types of gas generators. Coal type │ Parameter: Jiyang coking coal, Datong bituminous coal, Fushun gas coal, Hebi low-quality coal, Tongchuan low-quality coal, Yangquan anthracite, Yingcheng long-flame coal, Huainan gas coal, Jiaozuo anthracite, Hegang gas coal, Xishan anthracite. Gas composition (%): CO2: 2.24, 2.35, 3.0, 4.69, 3.25, 5.82, 6.2, 3.8, 6.63, 4.78, 6.17; H2S: 0.06, 0.05, 0.1, 0.035, 0.85, /, 0.1/, 0.04/, 0.15; CmHn: 0.2, 0.4, 0.4/, 0.3/, 0.3, 0.3//, /; O2: 0.1, 0.2, 0.2, 0.2, 0.2, 0.3/, 0.2, 0.1, 0.1, 0.02; CO: 29.3, 31.6, 28.5, 25.8, 26.7, 24.16, 25.0, 28.5, 25.9, 27.3, 23.28; H2: 12.5, 13.3, 14.0, 13.45, 15.4, 14.62, 15.0, 11.3, 15.3, 13.98, 11.42; CH4: 2.2, 1.8, 2.5, 2.08, 1.2, 1.25, 2.4, 1.7, 0.8, 2.9, 2.07; N: 53.4, 50.3, 51.3, 53.75, 52.1, 53.81, 51, 54.2, 51.23, 51.04, 56.89. Qd (Kj/Nm3): 5980, 6320, 6280, 5520, 5110, 5580, 5860, 5760, 5230, 6030, 4980. Gas generators – I. Introduction: Among the numerous heat treatment furnaces, forging furnaces, lead melting furnaces, and industrial ovens in use today, direct combustion of coal leads to serious problems related to energy waste and environmental pollution. On the other hand, although fuel oil is a clean energy source, its high cost makes it unaffordable for many enterprises. Therefore, upgrading existing coal-fired equipment has become an urgent task. 　　Converting coal gas into crude gas using air and water vapor before burning it is a reasonable way to modify it, and it can meet environmental standards. The fluidized bed hot gasifier utilizes the mature V-shaped air distribution plate sparging fluidization technology; an oxidation zone with a high oxygen concentration is created in the central area of the furnace through sparging jets ； A low fluidization state is adopted in the surrounding annular area as the reduction zone for the gasification reaction. Due to the large difference in wind speed between the two zones, extensive internal circulation of particles occurs, thereby enhancing the mixing as well as heat and mass transfer between the gas and solid phases ； It also increases the carbon conversion rate and possesses a high gasification intensity. A steam generator is installed at the top of the furnace; the steam produced by this generator is mixed with air and introduced into the furnace, thereby increasing the proportion of water in the gas and thus raising its calorific value. The fluidized bed gasifier employs an ash external circulation system, which significantly increases the residence time of coal particles inside the furnace, thereby improving the conversion rate of carbon. The hot gas passes through another cyclone dust collector, becoming cleaner gas before entering the main pipe and being sent to the gas nozzle. Since the static pressure at the outlet of the gas stove remains at 200–300 mmH2O, there is no need to pressurize the gas pipeline. Furthermore, the gas temperature is maintained above 400°C, preventing tar from precipitating out of the coal and avoiding pipeline blockages. Fluidized bed gasifiers use screened pulverized coal directly, significantly reducing raw material costs. Objectively, it has the advantages of strong adaptability to different coal types, mature technology, simple equipment, easy operation, low operating costs and investment requirements, as well as a small footprint ； It is highly suitable for various types of coal-fired furnaces. If the air preheating temperature is above 400°C, the gas combustion temperature can reach 1335℃ ； It can meet the requirements of steel rolling heating furnaces and enable the substitution of coal for oil. Gas combustion can completely eliminate the black smoke produced by direct coal burning ； Even furnace temperature, fast heating speed, coal savings and reduced consumption, with a significant increase in productivity and quality rate. 　　Coal is the fuel with the largest reserves in our country, and 3/4 of the country’s total fuel and energy consumption comes from coal. Resolving the issue of coal combustion is a fundamental task for our country. Chinese science institutions and several key domestic universities have been continuously researching clean coal combustion technologies. Over the years, our company has established extensive collaborative research relationships with research institutions, developing gas generators of various structural types, some of which are at the international leading level. 　　Fixed-bed gas generators represent a mature technology that has been in use for over a hundred years. The gas generators produced by our company have been successfully applied in industries such as metallurgy, machinery, non-ferrous metals, ceramics, and metal products, including various types of heating furnaces, melting furnaces, annealing furnaces, and drying furnaces. Since the gas is used directly in furnaces without being cooled, this approach not only saves energy but also meets **environmental requirements; as a result, gas generators have become increasingly widely used in various types of furnaces. Working principle of gas generator: In a typical gas generator, coal moves from top to bottom, while the gasifying agent moves from bottom to top in a counter-current manner; chemical reactions and heat exchange occur between them. In this way, several zones are formed in gas generation, which we generally refer to as layers. 　　Following the sequence of the gasification process within the gas generator, its interior can be divided into six layers (see the schematic diagram of the mixed gas generator structure): 1) Ash and slag layer, 2) Oxidation layer, 3) Reduction layer, 4) Carbonization layer, 5) Drying layer, 6) Air. The oxidation layer and the reduction layer are collectively referred to as the reaction layers, while the carbonization layer and the drying layer are collectively known as the coal preparation layers. 1) Ash layer: Ash is produced as a result of coal combustion, forming an ash layer that is located at the very bottom of the furnace, covering the grate. Its main functions are: a) to protect the furnace grates and air caps from being damaged by the high temperatures of the oxide layer. 　　b. Preheat the gasifying agent; after entering from the bottom of the furnace, the gasifying agent first passes through the ash layer for heat exchange, which lowers the temperature of the ash layer while raising the temperature of the gasifying agent. Generally, the preheating temperature of the gasifying agent is around 300–450°C. 　　c. The ash layer also serves to distribute the air, ensuring that the gasifying agent entering the furnace is distributed as evenly as possible. 2) Oxidation layer: Also known as the combustion layer. The oxygen in the gasifying agent rising from the ash undergoes intense combustion with carbon to produce carbon dioxide, releasing a large amount of heat. It is one of the main areas in the gasification process, and its primary reaction is: C + O2 ——> CO2 + 97,650 calories ————————(1). The height of the oxidation layer is generally 3–4 times the length of the fuel block used, typically ranging from 100 to 200 millimeters. The temperature in the gasification zone is generally lower than the ash melting point of coal, with an operating temperature of around 1200°C. 3) Reduction layer: Above the oxidation layer is the reduction layer. Hot carbon has a strong ability to seize oxygen from oxides and combine with it. Therefore, in the reduction layer, carbon reduces carbon dioxide and water vapor into carbon monoxide and hydrogen. This layer is thus named the reduction layer; its main reactions are: CO2 + C ——> 2CO – 38790 ————————(2) H2O + C ——> H2 + CO – 28380 ————————(3) 2H2O + C ——> CO + 2H2 – 28380 ————————(4) Since the reduction layer is located above the oxidation layer, it receives a large amount of heat from the rising gases. Therefore, the reduction layer has a high temperature of about 800–1100°C, which provides the conditions necessary for the reduction reaction that requires heat absorption. Strictly speaking, reduction can be further divided into a first stage and a second stage. The area with a higher temperature at the lower part is referred to as the first reduction layer; its temperature ranges from 950–1100°C, and its thickness is around 300–400 millimeters. The second layer exists at a temperature range of 700–950°C, and its thickness is 1.5 times that of the first layer, approximately 450 millimeters. 4) Carbonization layer: The carbonization layer is located above the reduction layer. As the gases rising from the reduction layer lose heat, their temperature gradually decreases; therefore, the temperature in the carbonization layer ranges from 150 to 700°C. At these temperatures, the coal undergoes a process of low-temperature carbonization, during which the volatile components in the coal break down to produce substances such as methane, olefins, and tar. When heated, these substances turn into gas, forming coal gas, which then escapes through the upper drying layer and becomes part of the coal gas. The height of the carbonization layer varies depending on the volatile content in the fuel and the operating conditions of the gas furnace, and is generally greater than 100 millimeters. 5) Drying layer: The drying layer is located above the carbonization layer, that is, the layer where the fuel is present. The rising hot gas meets the fuel that has just entered the furnace at this layer, where heat exchange takes place; the moisture in the fuel evaporates as a result of the heat. It is generally believed that the drying temperature ranges from room temperature to 150°C. This guiding height also varies depending on various operating conditions, with no relatively stable ceiling height. 6) Empty space: The empty space refers to the area above the fuel, the free zone within the furnace, and its main function is to collect gas. During the brief residence time of the gas in the empty space, some side reactions occur when the temperature inside the furnace is high; for example, CO decomposes to release some carbon black. 2CO ————>CO2+C 2H2O+CO————>CO2+2H2. From this brief description of the six processes involved, it can be seen that the gasification process that takes place in a gas generator is quite complex, involving not only gasification reactions but also processes of carbonization and drying. Moreover, in the actual production process, the layering is not very strict either. The two adjacent layers are often intertwined, and the temperature of each layer changes gradually, making it difficult to draw a clear distinction between them. The changes in the gas composition across different layers are more complex, and even within specialized technical research, there are differing opinions. Structure of gas furnaces: There are various structural designs for fixed-bed gas furnaces, which are described below by different components: 1. Coal feeding device: intermittent coal feeding hood, double bellows, vibrating coal feeder. Toothed coal feeder. 　　2. Furnace structure: pressure full water jacket, semi-water jacket, no water jacket (refractory lining), Changcun full water jacket. 　　3. Furnace grating: pagoda shape, welded from section steel. 　　4. Gray disc drive structure: gear shift type, worm gear type. 　　Our company produces gas generators in various forms for selection. Technical parameters and prices of CGIQ-22A mixed gas generator
Specifications (Unit) φ1000 φ1500 φ2000 φ2400 φ3000
Item Furnace area (M2) 0.79 2 3.14 5.31 7.07
Applicable fuels Coke, anthracite, weakly caking bituminous coal
Fuel particle size (mm) 30-40 30-50 30-50 40-60 40-60
Fuel consumption (Kg/h) 150 400 600 1030 2200
Gas production volume (M3/h) 420-540 1120-1440 1680-2160 2800-3700 5800-7000
Gas outlet temperature (°C) 450-550 450-550 450-550 450-550 450-550
Gas calorific value (Kcal/m3) 1200-1350 1200-1350 1200-1350 1200-1350 1200-1350
Gas outlet pressure (Pa) 980-1960 980-1960 980-1960 980-1960 980-1960
Maximum blast pressure at furnace bottom (Pa) 2014 2014 2014 2014 2014
Saturation temperature (°C) 55-65 55-65 55-65 55-65 55-65
Steam consumption (Kg/h) 50 150 220 350 700
Ash removal method Rotary disc furnace with wet dust removal
Gasification type Air and steam
External dimensions (M2) 25 30 35 35 60

Composition and calorific value of gas generated from several common coal types
Coal type Jiayang coking coal Datong bituminous coal Fushun gas coal Hebi lean coal Tongchuan lean coal Yangquan anthracite Yingcheng long-flame coal Huainan gas coal Jiaozuo anthracite Hegang gas coal
Item Gas Volume Composition %
CO2 2.24 2.35 3.0 4.69 3.25 5.82 6.2 3.8 6.63 4.78
H2S 0.06 0.05 0.1 0.035 0.85 / 0.1 / 0.04 /
CmHn 0.2 0.4 0.4 / 0.3 / 0.3 0.3 / /
O2 0.1 0.2 0.2 0.2 0.2 0.3 0.2 0.1 0.1
CO 29.3 31.6 28.5 25.8 26.7 24.16 25.0 28.5 25.9 27.3
H2 12.5 13.3 14.0 13.45 15.4 14.62 15.0 11.3 15.3 13.98
CH4 2.2 1.8 2.5 2.08 1.2 1.25 2.4 1.7 0.8 2.9
N 53.4 50.3 51.3 53.75 52.1 53.81 51 54.2 51.23 51.04
Qd/Nm3 5980 6320 6280 5520 5110 5580 5860 5760 5230 6030