Study On Reasonable Utilization And Optimizing Distribution Of Gases Fuel In Iron And Steel Complex

The process of steel producing is a typical iron-coal chemical process:the coal energy such as clean coal and coal for injection change to CO2 by conversion tache, recovery tache and using tache, producing iron and steel products based on consumption of iron ore and coal. And in this way the energy flow is formed, in which the coal flow is the main part. Byproduct gases is main parts in carbon flow, and the important secondary energy in iron and steel works, taking part of 30% in total energy consumption. So how to recognize the changing law of gas supply and demand relations in iron & steel complex, to plan the production, stock, distribution and utilization of gas, especially the buffer utilization strategy for the residual gas, for using the gas rationally, reducing the energy consumption per ton steel and CO2 emission is very meaningful. This paper studies the law of gas production and utilization, and that of gas supply and requirement; builds the gas optimization and distribution model for several energy using equipments; constructs the gas dynamic optimization and distribution model for the residual gas distribution between gas holders and boilers in the power plant. The models offer the theoretical basis and analyzing tools for the rational utilization and optimization distribution of gases. The main contents of this paper are as follows:(1) Tracking the conversion and dissipation process of carbon element flow in iron and steel production, the byproduct gases recovery and utilization analysis indicate that the carbon element flow change under the certain amount of the total carbon element flow in iron and steel manufacturing flow. The producing process and BFG, COG and LDG recovery and utilization are analyzed. The factors of influencing the gas recovery and utilization are indicated:original fuel condition; thermal operation conditions; recovery process; equipment levels; preheated combustion medium et al. The three modes of gases for power are expounded and the rules of residual gas utilization are put forward. Gas regeneration utilization and route are viewed.(2) Gas supply and demand forecasting model is established in iron and steel works, the factors influencing the gas generation, gas consumption and residual gas amount per steel are analyzed, unit gas generation and gas consumption per product and steel ration of each process take the dominating factors. The relation of gas supply and demand is analyzed and the evaluating indexes of gas recovery and utilization are put forward, such as gas recovery rate, gas thermal conversion efficiency, gas thermal-electricity conversion efficiency and gas integration utilizing efficiency. The influence of gas recovery and utilization on energy consumption per steel is analyzed and the measures of reducing energy consumption per steel of iron and steel works from gas utilization viewpoint is indicated:â‘ reducing gas consumption of using energy equipments through improving gas utilizing efficiency by heat regenerative technique;â‘¡perfect the gas recovery process with dry dust technique;, increasing gas recovery ratio;â‘¢utilizing residual gas efficiently, enhancing gas thermal-electricity conversion efficiency with CCPP;â‘£strengthening gas management level, decreasing or eliminating gas release loss by constructing EMC. The model of "Buying only coal and no purchasing electricity" is proved and the gas supply-demand model are analyzed in different steel scale iron and steel works under residual pressure and heat power levels.(3) Exchangeability of fuels in facilities and reasonable heat value of gases are studied in iron and steel works, and the byproduct gas utilization and distribution model for least energy consumption which is restricted by energy demand, process requirement and energy medium balance is set up based on fuel utilization coefficient and unit fuel consumption of fuel changeable, according to the difference of fuel using efficiency in different equipments. Gas quantity and quality are considered comprehensively in interchangeability of fuel gases; reasonable gas heat values makes gas utilization and equipment thermal operation parameter combine closely for decreasing the heat transfer exergy lose in the process of heating; the viewpoint of priority using single variety gas and remainder inputting gas net is put forward for reducing the exergy lose in mixing process of BFG and COG, investment charge of pipelines, mixing and pressurized station equipments. The model is feasible and available for making gas utilization plan of long, middle and short term and confirming optimal gas consumption project by improving the gas utilization efficiency and thermodynamics grade.(4) The residual gas dynamic distribution model in gas holder and power station is set up using punishing function, and the status of gas holder only for safety and reducing the efficiency of power station by using abundant byproduct gases is changed. The buffer by gas holder and boilers in power station improves gas and power utilization efficiency, and reduces gas emission. The efficiency, capacity and available fuel of boilers, surplus and deficient gas amount are adjusted by gas holder and power station, the gases resource is optimized and distribution, the gas emission is reduced.(5) The gas optimizing distribution model and residual gas optimizing utilization model are used in different iron and steel works-An steel works and Qian Steel respectively. The plans of gas utilization and optimizing distribution efficiently are put forward on the gas supply and demand conditions of different producing status. It is indicated that the gas heat values and gas consumption per ton product of different energy using equipments decrease. If the residual gas using for power and power efficiency is 37%, the energy consumption per steel will decrease 37.59 kgce/t steel. It is indicated that the potential of energy saving in the gases system of An Steel is very high when the blast furnace stops running, or 1780 rolling producing line is examined, or the 6m coke oven is examined. In the current status it is 83.2 thousand cubic meter per hour coke oven gas for sale under the producing demand and gas. Residual gas is optimizing distribution between gases holders and boilers in power station in Qian Steel. After optimization, the gas emission decreases and operation fee is saved when gas holder is in safety zone and fuels are changed in boilers correctly.