矿热炉又称电弧电炉或电阻电炉。它主要用于还原冶炼矿石，碳质还原剂及溶剂等原料，主要生产硅铁，锰铁，铬铁、钨铁、硅锰合金等铁合金。矿热炉主要分为半密闭和密闭炉两种类型，其中密闭炉产生的尾气含有的可燃成分较多，能够用于燃气内燃机发电。

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.

在矿热炉生产铁合金的过程中产生的尾气(Furnace off gas，简称FOF)主要成分为CO，以及少量的 H2、 CO2等。其中一氧化碳（CO）气体是由于还原剂中存在碳而形成的，如果还原剂中含有挥发性碳氢化合物，则会形成氢气（H2）。过去，矿热炉尾气通常是直接燃烧后排放，而现在则可以通过高效的燃气内燃机发电，同时利用高温烟气的热能，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 矿热炉尾气的燃烧特性和利用难点

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

FOF的热值通常只有天然气热值的1/3左右，也就是说相比于同级输出功率的天然气机型，FOF发电机组的进气量需要增大3倍以上。FOF的抗爆性与天然气也有显著区别，其甲烷指数(Methane Number，简称MN)只有天然气的大约60%左右，这意味着这种气体在内燃机气缸里面更容易发生爆震。所以，燃气发电机组需要通过传感器监测爆震的发生以调整机组的运行状态。另一方面，FOF燃烧时的层流火焰速度(Laminar Flame Speed，简称LFS)却比天然气快许多，这和气体里面氢气的含量比例有关。层流火焰速度是在层流前沿发生氧化反应的速度， 即未燃烧的混合气与火焰前沿之间的相对速度。根据麻省理工学院的研究资料，在当量比(Equivalence Ratio)为2时，5% H2和95% CO组成的混合气的LFS约为50cm/s，而 50% H2和50% CO组成的混合气的LFS可到160cm/s。鉴于FOF特殊的燃烧特性，燃气内燃机的进气系统和控制参数都需要特殊设计以适应其特性，同时还必须满足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.

山东中拓的 DIA.NE XT4系统在气体质量波动时自动调整设置，因此能够适应复杂的运行情况。同时，山东中拓的LEANOX稀薄燃烧控制技术能够实时控制氮氧化物NOx的排放，确保始终满足严苛的环保要求，使机组排气出口NOx达到250-500mg/Nm3(@5% O2)，并且无需SCR等复杂的尾气后处理装置。新的山东中拓资产管理系统myPlant则能实时监测、控制和预测机组的运行状态，并能提供前瞻性的维护保养建议。

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.

图2 H2和CO混合气的层流火焰速度（来源：MIT）

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

3 燃气内燃机对气体的杂质含量要求

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

尾气的成分和气量与炉子的运行参数有关，并受到原料质量、炉子控制和运行状态等因素的影响，所以通常会连续变化。采用气柜来减少气体热值和压力的波动，对于燃气内燃机发电非常重要。在炉子供气中断时，气柜还可以起到缓冲的作用。

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.

进入内燃机前的FOF需要进行预处理，以满足气体质量要求。通常需要去除粉尘，以及多余的水分，还有焦油、硫及其他有害杂质等。硫、氨等成分的含量要求与燃气的热值相关，须根据实际热值确定上限值。下表是山东中拓燃气内燃机对气体的一般质量要求。

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.

燃气质量范围或上限值

Gas quality range or upper limit value

压力波动(kPa/s)1

Pressure fluctuation (kPa/s) 1

热值波动(%/min)4

Calorific value fluctuation (%/min) 4

3μm以上颗粒过滤效率(客户提供运行过滤器)>99.99%

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

温度(°C)10~40

Temperature (° C) 10~40

相对湿度<80%

Relative humidity<80%