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Technical Renovation and Application of the £2,650 Gas Generator System Author/Source: Ma Demian (Shandong Hengtong Chemical Co., Ltd., Juecheng 276100) Date: 2003-6-16 The fertilizer production facility of Shandong Hengtong Chemical Co., Ltd. has a capacity of 180,000 tons per year for alcohol-ammonia and 250,000 tons per year for urea. The existing 10 gas generators with a diameter of ￠2650 and 2 gas generators with a diameter of ￠2400 in the facility are operating at full capacity, with no backup generators available for long periods. To make full use of the remaining coal dust in the power plant, leverage the advantages of comprehensive resource utilization, and address the issues of outdated equipment and process flows, high energy consumption, and high system resistance, the gas generation furnace was upgraded and modified after thorough investigation and evaluation. The company decided to use a gas furnace with a steel frame of diameter 2,650, along with briquette technology; it also adopted the automatic coke feeding technology from Hebei Delong Company, making adjustments to suit local conditions. Relying on the company’s technical capabilities for independent design and production, this project was put into operation recently, and it has demonstrated good economic benefits from the very beginning of its operation. The specific design, equipment, features, and application scenarios are summarized below for reference in practical use. 1 Improvement and fabrication of some equipment 1.1 Modification of the furnace bottom of the ￠2650 gas generator; the process flow is shown in Figure 1. The new DF-Ⅱ type hexagonal grating produced by Jiangsu Pizhou Dongfang Chemical Machinery Co., Ltd. has been introduced. The gray disc features inner upper and lower sealing rings; these rings are positioned at the center to prevent displacement. They contain high-chromium steel balls with a diameter of 80 mm, as well as sealed slides and a closed-type transmission system. The material used is heat-resistant cast iron. It effectively ensures the proper operation of the equipment at the bottom of the furnace, prevents the ash tray from tilting, and enables good ventilation through the grates as well as even distribution of the gasifying agent. It plays a crucial role in stabilizing the furnace conditions, effectively breaking down slag, removing ash, and maintaining a stable combustion layer within the furnace. http://www.zaoqiwang.com/upload/060315843145984.jpg 1.2 For the branch pipes at the furnace bottom, use a straight pipe; the air supply seat valve has a diameter of Π600. The branch pipes at the furnace bottom should be straight pipes, that is, the branch pipes should be changed from Y-shaped to T-shaped, so as to ensure a clear flow direction for the air vaporizing agent and semi-coke gas. Si Shi prevented the mixing of semi-water gas with air during production, reducing the risk level and providing a solid design guarantee for the proper operation of the gas generation furnace. The use of a blower seat valve worth £600 allows for an increased amount of air vaporizing agent to be fed into the furnace. It offers good sealing performance, a long service life, and low maintenance costs; it also provides the basis for adopting a \"high-pressure short-duration blowing\" approach in order to increase the gas production per furnace and optimize furnace operation. 1.3 Remove the preheater to reduce system resistance. The preheater was used to recover the latent heat of gas in order to increase the temperature of the saturated steam coming from the steam-water separator. However, in this technical upgrade, the previous practice of passing the F water gas through a preheater before feeding it into the waste boiler was changed; instead, the preheater was removed. The purpose is to reduce system resistance and ensure smooth gas flow. Removing the preheater may affect the superheating and quality of saturated steam, but the steam supplied by the power plant and the purge air is sufficient to address this issue. Removing the preheater can save an investment of 778,000 yuan. 1.4 Remove the chimney base and allow venting directly above the waste heat boiler; the chimney base is removed and a \"L\"-shaped elbow is designed to connect directly to the outlet of the chimney valve. Its advantages are low investment, simple construction, and minimal workload. The use of this “L”-shaped chimney is the result of our company adapting to local conditions. All design, production, and installation are carried out in-house by the company. By installing this chimney, space is reduced and costs are saved. It also reduces the resistance of exhaust gases in actual use. Removing this chimney base saves an investment of about 50,000 yuan. 1.5 The distributor of the automatic coke feeder has been changed from a downward-type to an upward-type design. As part of this technical upgrade, the distributor of the automatic coke feeder introduced from Hebei Delong Company has been modified from a downward-type to an upward-type design. It plays a very important role in extending the service life of the Fabric er, ensuring a uniform carbon layer, and stabilizing the furnace conditions. (1) Before the technical upgrade, the distributor of the automatic coke feeder was a downward-type distributor. The coal fed into the furnace enters the small silo after flow control via plug valves and disc valves. During coal addition (1–3 seconds), this distributor descends directly into the furnace, distributing the fuel. As a result, a \"V\"-shaped carbon layer is formed, with a lower level in the center and a higher level on the periphery. This can lead to phenomena such as overturning or denting of the carbon layer inside the furnace, which hinders the even distribution of the gasifying agent. The furnace conditions tend to deteriorate, making it difficult to maintain control. (2) After the technical upgrade, the distributor of the automatic coke feeder is of the lifting type. The coal fed into the furnace enters the small silo through plug valves and disc valves. When coal is added, the distributor is raised, and the raw coal enters the furnace; as a result, an effect completely opposite to that of the \"sinking\" method occurs on the surface of the coal layer – that is, a bun-shaped surface with a higher layer in the middle and progressively lower layers, which meets the requirements for gas production in gas generators. 2 Innovations in process operations and parameters: (1) One blower (C600) is used to supply gas to 5 Φ2650 gas generators, with significant results. After the new gas generator came into operation, our company replaced the existing D400-11 fan with a 9-26N010.D pressure fan connected in series, following the standard practice of using such a fan to supply power to the 4 × ø650 gas furnaces. Using one C600-1.26 fan to power 5 Φ2,650 gas furnaces for production set a precedent for small and medium-sized nitrogen fertilizer plants in China. Its feature is a stable flow rate of air entering the furnace, which is easy to control. It can **increase the gas production volume of semi-water gas, make effective use of the air supply volume to raise the temperature of the gasification zone, and fully utilize its potential. Since it was put into operation, it has resolved the issues associated with the D400-11 fan and the series/parallel pressure-boosting fans, such as unstable air pressure, insufficient air volume, inadequate gas output, and low output per furnace; abnormal situations occur very rarely inside the furnace. The coal gasification in the furnace is thorough, with minimal coking, ensuring and stabilizing the supply required to support the operation of 26.5 units (of the 4M36 type) powered by 12 furnaces. (2) One C600-1.26 fan is used to supply 5 Φ2650 gas generators, and it operates in series with one D400-11 fan; together they power the 9-26N010.D compressor, which serves 4 Φ2650 gas generators. This arrangement offers considerable economic benefits. The motor power of the C600-1.26 fan is 440 kW, with an air flow rate of Q = 600 m3/min; its utilization rate can be increased to 80%. The D400-11 fan is connected in series and parallel with the 9-26N010.D compressor; the total motor power is 220 + 75 = 295 (kW). To operate 5 furnaces, another fan (D400-11) is required; thus, when using the D400-11 fan in combination with the booster pump to run 5 furnaces, the total power is 515 kW, which is 75 kW less than that achieved with the C600 fan. If the electricity price is 0.3 yuan/kWh, 540 yuan can be saved per day, amounting to nearly 200,000 yuan per year. (3) After being put into operation, compared with other furnaces, this furnace features good gas composition, sufficient gas generation volume, high decomposition rate, low coking rate, and stable operating conditions. A 72-hour test was conducted from December 10 to 13, 2002. The results are as follows: gas generation rate of 6,800 m3/h, steam decomposition rate of 56.9%, combustible content in the ash reduced to below 10%; gas composition (by volume): CO2 ≤ 5.8%, O2 0.4%, CO ≥ 32%. 3 Summary and Future Development (1) The new process for the modified Φ2650 gas generator features a relatively simple equipment structure and process flow; it has a unique design, is easy to operate and control, requires low investment, and is suitable for the needs of urea production upgrades and expansion. Suitable for use in most fertilizer plants whose main product is urea. (2) The improved technical process for this gas generator results in low total investment and quick benefits for ordinary urea plants, while allowing full utilization of residual coal dust for powder production, gasification, and briquette use. Only by changing the raw material supply route can the industry move forward in the direction of producing less nitrogen-based fertilizers, enabling enterprises to survive and develop. (3) To reduce air pollution and increase steam production, 3 blast air recovery units using 1990s-era technology will be phased out in the future, and a new large-scale blast air recovery unit with a design pressure of 3.8 MPa (38 kg/cm2) and a steam output of 30 t/h will be installed. The civil engineering work has already begun; its combustion furnace has a diameter of 7.5 m and a height of 25 m. The steam produced not only meets the needs of gas generation and other systems but can also be used to generate high-pressure steam for power plants, resulting in significant overall benefits. (4) To continue to adapt to the ongoing development and growth of the enterprise and to enhance the potential of the gas generation furnace, it is planned to install a DCS system during future renovations in order to conduct comprehensive monitoring of the furnace’s operation. On this basis, closed-loop optimization of the gas stove temperature is carried out to improve the conditions for gas production and reduce the workload on workers, thereby supporting the future development of the enterprise. This post was last edited by shanxg on 2009-2-25 21:59]