With the rapid development of global industrialization, the consumption of primary energy (such as oil, coal, natural gas, etc.) keeps increasing continually. Therefore, human beings have to look for new sources of energy constantly to reduce or replace disposable energy consumption for their own survival and development. As one part of the renewable energy and the world's fourth largest energy, biomass energy has promising prospects of development and utilization, among which, straw power generation is a newly developed technology using renewable energy in recent years.
The establishment and use of biomass power unit is greatly encouraged by national policies, such as these followings issued by the national development and reform commission: "Related Management Regulations on Renewable Energy Power Generation", "Guidance Catalogue on the Renewable Energy Industry Development", "Tentative Management Measures for the Price and Allocation of Charges of the Renewable Energy Power Generation”. The national development and reform commission has also approved a batch of biomass power generation projects, therefore the establishment and use of the biomass generator unit will undergo a fast development stage in the next few years. However, so far the equipment and system of biomass power generation unit are all imported abroad, and the personnel’s training is done in foreign countries. So the development of the full-range simulator of biomass power generation unit becomes imperative.
2. Technical Features
As the physical and compositional properties of the raw material fuel are greatly different with that of the coal-fired boiler, the primary task for establishing biomass power simulation is to develop new mathematical model applicable to raw material combustion; and second to it is about the surrounding ancillary equipments, such as water-air heat exchanger, and the material conveying equipment.
In the following are some theories about the mathematical model applicable to raw material combustion. The mixture of air and fuel in the furnace is completely burned to high temperature flue gas which firstly heats the water wall and the radiation superheater through radiation heat transfer; then heats other superheaters, economizer and flue gas cooler through convection heat transfer and finally becomes cold flue gas discharged into the atmosphere. During modeling, the lumped parameter method is used according to the mass conservation equation, energy conservation equation and momentum conservation equation. The basis for the designing is: the combustion mechanism of raw material fuel belongs to the type of static penetration diffusion combustion and its combustion process starts after the ignition.
(1) The combustible volatile on the original biomass fuel's surface burns, the combustible gas and oxygen form exothermic chemical reaction, in this way, the flame is formed;
(2) In addition to the burning of the combustible volatile on the original biomass fuel's surface, the carbon, on the fuel's surface and belonging to the transitional combustion zone, forms a relatively long flame;
(3) The combustion penetrates from fuel surface into deeper part. During the spread of the coke's combustion, the combustion products CO2, CO and other gases will be diffused, and CO will constantly combines with O2 into CO2, forming thin grey shells surrounded by the outer flame on the fuel surface;
(4) The combustion spreads into deeper layer. In the deeper layer is mainly the carbon combustion (C + O2 – CO2); on the surface is mainly the carbon monoxide combustion (C0 + O2 – CO2), forming a thick grey shell. Because of the biomass burning out and thermal expansion, the ash layers present micro porous organization or gap channel or even crack, with fewer short flame surrounded.
Therefore, original biomass combustion is a slow process different from the pulverized coal combustion. It becomes the key for establishing the mathematical simulation model that how to judge the combustion rate of the biomass fuel in the boiler.
3. First domestic biomass generation simulator ventured into training
With the joint efforts of Baoding SinoSimu Technology Co., Ltd, Guoneng Bio-energy Power Generation Co., Ltd and Shandong Huangtai Power Plant (biomass generator simulator training units), the first domestic 30 MW full-range biomass power unit simulator was successfully developed and researched on October 21, 2006.
Guoneng Bio-energy Power Generation Co., Ltd and Shandong Huangtai Power Plant carried out test both on the components and the whole unit from October 22 to 31, 2006, confirming that all the delivered equipments were in accordance with the provisions of the contract and had been successfully installed, debugged, and have met the training requirements.
The contract on this simulator was signed on July 20, 2006, so the delivery time is quite limited but the task is very heavy and requires a lot of innovation points. Under this kind of circumstance, through the corporation with Guoneng Bio-energy Power Generation Co., Ltd and its own hard-working and careful organization, Baoding SinoSimu Technology Co., Ltd successfully completed this tough work.
Baoding SinoSimu Technology Co., Ltd has contributed a lot in promoting the application and staff-training of the biomass power generation unit in our country.
