礦熱爐又稱電弧電爐或電阻電爐。它主要用于還原冶煉礦石，碳質還原劑及溶劑等原料，主要生產硅鐵，錳鐵，鉻鐵、鎢鐵、硅錳合金等鐵合金。礦熱爐主要分為半密閉和密閉爐兩種類型，其中密閉爐產生的尾氣含有的可燃成分較多，能夠用于燃氣內燃機發電。

Mineral arc furnace, also known as electric arc furnace or resistance furnace. It is mainly used for reducing smelting ores, carbon reducing agents, solvents and other raw materials, and mainly produces ferroalloys such as ferrosilicon, ferromanganese, ferrochromium, ferrotungsten, and silicomanganese alloys. Mineral heat furnaces are mainly divided into two types: semi enclosed and enclosed furnaces. The exhaust gas generated by enclosed furnaces contains more combustible components and can be used for gas internal combustion engine power generation.

在礦熱爐生產鐵合金的過程中產生的尾氣(Furnace off gas，簡稱FOF)主要成分為CO，以及少量的 H2、 CO2等。其中一氧化碳（CO）氣體是由于還原劑中存在碳而形成的，如果還原劑中含有揮發性碳氫化合物，則會形成氫氣（H2）。過去，礦熱爐尾氣通常是直接燃燒后排放，而現在則可以通過高效的燃氣內燃機發電，同時利用高溫煙氣的熱能，使能源得到高效充分地利用。

The exhaust gas (FOF) generated during the production of ferroalloys in a submerged arc furnace is mainly composed of CO, as well as a small amount of H2, CO2, etc. Carbon monoxide (CO) gas is formed due to the presence of carbon in the reducing agent. If the reducing agent contains volatile hydrocarbons, hydrogen gas (H2) will be formed. In the past, the exhaust gas from submerged arc furnaces was usually discharged after direct combustion. However, now it can be generated through efficient gas internal combustion engines, while utilizing the heat energy of high-temperature flue gas to efficiently and fully utilize energy.

2 礦熱爐尾氣的燃燒特性和利用難點

The combustion characteristics and utilization difficulties of exhaust gas from a submerged arc furnace

FOF的熱值通常只有天然氣熱值的1/3左右，也就是說相比于同級輸出功率的天然氣機型，FOF發電機組的進氣量需要增大3倍以上。FOF的抗爆性與天然氣也有顯著區別，其甲烷指數(Methane Number，簡稱MN)只有天然氣的大約60%左右，這意味著這種氣體在內燃機氣缸里面更容易發生爆震。所以，燃氣發電機組需要通過傳感器監測爆震的發生以調整機組的運行狀態。另一方面，FOF燃燒時的層流火焰速度(Laminar Flame Speed，簡稱LFS)卻比天然氣快許多，這和氣體里面氫氣的含量比例有關。層流火焰速度是在層流前沿發生氧化反應的速度， 即未燃燒的混合氣與火焰前沿之間的相對速度。根據麻省理工學院的研究資料，在當量比(Equivalence Ratio)為2時，5% H2和95% CO組成的混合氣的LFS約為50cm/s，而 50% H2和50% CO組成的混合氣的LFS可到160cm/s。鑒于FOF特殊的燃燒特性，燃氣內燃機的進氣系統和控制參數都需要特殊設計以適應其特性，同時還必須滿足NOx的排放要求。

The calorific value of FOF is usually only about one-third of that of natural gas, which means that compared to natural gas models with the same level of output power, the intake volume of FOF generator sets needs to be increased by more than three times. The anti knock performance of FOF is also significantly different from that of natural gas, with its Methane Number (MN) only about 60% of that of natural gas, which means that this gas is more prone to detonation in internal combustion engine cylinders. Therefore, gas generator units need to monitor the occurrence of detonation through sensors to adjust the operating status of the unit. On the other hand, the laminar flame speed (LFS) during FOF combustion is much faster than natural gas, which is related to the proportion of hydrogen content in the gas. The laminar flame velocity is the rate at which oxidation reactions occur at the front of the laminar flow, that is, the relative velocity between the unburned mixture and the flame front. According to research data from the Massachusetts Institute of Technology, when the equivalence ratio is 2, the LFS of a mixture of 5% H2 and 95% CO is about 50cm/s, while the LFS of a mixture of 50% H2 and 50% CO can reach 160cm/s. Given the unique combustion characteristics of FOF, the intake system and control parameters of gas internal combustion engines require special design to adapt to their characteristics, while also meeting the NOx emission requirements.

山東中拓的 DIA.NE XT4系統在氣體質量波動時自動調整設置，因此能夠適應復雜的運行情況。同時，山東中拓的LEANOX稀薄燃燒控制技術能夠實時控制氮氧化物NOx的排放，確保始終滿足嚴苛的環保要求，使機組排氣出口NOx達到250-500mg/Nm3(@5% O2)，并且無需SCR等復雜的尾氣后處理裝置。新的山東中拓資產管理系統myPlant則能實時監測、控制和預測機組的運行狀態，并能提供前瞻性的維護保養建議。

Yanbach's advanced DIA. NE XT4 system automatically adjusts settings when gas quality fluctuates, thus being able to adapt to complex operating conditions. At the same time, Yanbach's LEANOX lean combustion control technology can control the emission of nitrogen oxide NOx in real-time, ensuring that strict environmental requirements are always met, so that the NOx at the exhaust outlet of the unit can reach 250-500mg/Nm3 (@ 5% O2), and there is no need for complex tail gas post-treatment devices such as SCR. The new Yanbach asset management system myPlant can monitor, control, and predict the operating status of the unit in real-time, and provide forward-looking maintenance recommendations.

圖2 H2和CO混合氣的層流火焰速度（來源：MIT）

Figure 2 laminar flame velocity of H2 and CO mixture (source: MIT)

3 燃氣內燃機對氣體的雜質含量要求

3. Requirements for impurity content of gas in gas internal combustion engines

尾氣的成分和氣量與爐子的運行參數有關，并受到原料質量、爐子控制和運行狀態等因素的影響，所以通常會連續變化。采用氣柜來減少氣體熱值和壓力的波動，對于燃氣內燃機發電非常重要。在爐子供氣中斷時，氣柜還可以起到緩沖的作用。

The composition and gas volume of exhaust gas are related to the operating parameters of the furnace, and are influenced by factors such as raw material quality, furnace control, and operating status, so they usually change continuously. The use of gas cabinets to reduce fluctuations in gas calorific value and pressure is very important for gas internal combustion engine power generation. When the gas supply to the furnace is interrupted, the gas holder can also serve as a buffer.

進入內燃機前的FOF需要進行預處理，以滿足氣體質量要求。通常需要去除粉塵，以及多余的水分，還有焦油、硫及其他有害雜質等。硫、氨等成分的含量要求與燃氣的熱值相關，須根據實際熱值確定上限值。下表是山東中拓燃氣內燃機對氣體的一般質量要求。

The FOF before entering the internal combustion engine requires pre-treatment to meet the gas quality requirements. Usually, it is necessary to remove dust, excess water, tar, sulfur, and other harmful impurities. The content requirements of components such as sulfur and ammonia are related to the calorific value of the gas, and the upper limit value must be determined based on the actual calorific value. The following table shows the general quality requirements for gases in Yanbach gas internal combustion engines.

燃氣質量范圍或上限值

Gas quality range or upper limit value

壓力波動(kPa/s)1

Pressure fluctuation (kPa/s) 1

熱值波動(%/min)4

Calorific value fluctuation (%/min) 4

3μm以上顆粒過濾效率(客戶提供運行過濾器)>99.99%

three μ Particle filtration efficiency above m (customer provided running filter)>99.99%

溫度(°C)10~40

Temperature (° C) 10~40

相對濕度<80%

Relative humidity<80%