Generation efficiency of gas-fired generating units usually ranges from 30% to 40%, up to 35% compared with common models. The most prominent advantage of gas internal combustion engine is high power generation efficiency, followed by high integration of equipment, fast installation, low dust requirement in gas, no need for water at all, and low unit kilowatt cost of equipment. But the internal combustion engine also has some deficiencies. Firstly, when the internal combustion engine extinguishes the low calorific value fuel, the output of the unit obviously drops. When a 500 kW gas-fired internal combustion generator unit extinguishes the low calorific value 8000 kcal/cubic meter natural gas fuel, the output may drop to about 350-400 kW when using the low calorific value 4000 kcal/cubic meter coking gas.
In addition, the frequent replacement of oil and spark plug in internal combustion engine demands a large amount of data, which also affects the usability and reliability of the two main equipment application indicators, and has a great impact on the equipment application rate. Sometimes, the method of increasing the number of generators has to be adopted to eliminate the impact of low application rate. Internal combustion engine equipment is sensitive to water molecule content and hydrogen sulfide ratio in coking gas, which may cause hydrogen sulfide and water to form sulfuric acid corrosion problem. Some necessary measures should be taken to restrain it.
Gas turbines are comparable to inferior fuels with high hydrogen content, low calorific value and more impurities in gases. Some gas turbines even use crude oil and high sulfur residue fuels. The generation efficiency of gas turbine itself is not very high, usually between 30% and 35%, but the temperature of waste heat flue gas generated is as high as 450-550 C. It can recover heat energy to convert steam again through waste heat boiler, drive steam turbine to generate electricity again, and form gas turbine-steam turbine combined cycle power generation. The generation efficiency can reach 45%-50%, and some large-scale units can exceed 55%. 。
The advantages of using gas turbines are comparable, first, the availability and reliability of the equipment are comparatively high, and the comprehensive application rate can generally be maintained at 90%; secondly, the fuel compliance is comparatively strong, and the problems of high sulfur and dust content are not serious; thirdly, the power output of power generation is generally not reduced, and even increased due to the increase of fuel intake; moreover, the power density of gas turbines is high. The coking gas application of some uncertain coking plant projects is very advantageous.
However, there are advantages and disadvantages in the affairs of the world. There are no perfect things. The intake pressure of gas turbine is larger than that of gas turbine, and the higher the intake pressure of fuel of unit with high power generation efficiency. Because there is no pressure of coking gas itself, it is necessary to use gas compressor to tighten the demand of gas, which consumes a lot of energy and affects the practical output power of equipment. Some projects even consume 15%~20% of the power of gas turbine. The noise may be 10%~15% of the output power; the system is complex, the investment is large, and the relocation is difficult when the combined cycle system has the same water resource requirements as the steam turbine.