2. Coal-fired boilers refer to coal burned with fuel. After the heat of coal is converted, steam is generated or turned into hot water. However, not all the heat is effectively converted, and some of them are idle, so there is an efficiency problem. Generally, the efficiency of larger boilers is higher, ranging from 6% to 8%.

3. The beancurd machine is based on the principle that protein molecules of soybean (soybean) form conjunctiva after heating, and the soybean is made into a traditional food beancurd machine in China. There is an interlayer in the middle of the rectangular pot, which is filled with water. It is necessary to set up a stove at one end of the machine and link it with water pipes. The straight water pipes are connected with the water in the interlayer, and the water is mainly used for constant temperature. The pot is divided into small squares to adapt to the size of yuba.