The asphalt tanks (i.e. asphalt storage tanks and asphalt high temperature tanks) and heat transfer oil heating and reasonable application in the asphalt concrete mixing system are the key to reducing investment costs and improving the economic benefits of equipment. This article intends to take the QLB1000 asphalt concrete mixing equipment of Lianshui County Highway Management Station as an example to explain how to reasonably select asphalt tanks and heating equipment.
The selection of asphalt storage tanks and asphalt high temperature tanks must meet the needs of continuous production of asphalt concrete mixing equipment, and avoid excessive investment, waste, and increased costs. It should be reasonably determined based on the amount of asphalt consumption.
The daily asphalt production volume m(t) of the mixing equipment is:
m=P·h·k=80×10×5%=40
Where P----the upper limit production capacity of asphalt concrete mixing equipment t/h, k----asphalt content, its value is generally 2.5%--8%, and the normal value is 5%, h----daily effective working time, set to 10, the total asphalt storage volume M is
M=A·m=3×40=120
Where A----storage coefficient, A＞1, when the asphalt supply transportation distance is short and the vehicle transportation capacity is sufficient, this value can be appropriately reduced.
After the total asphalt storage volume is determined, the selection principle of the number and size of asphalt tanks is: suitable for the layout and installation of the mixing site; the production capacity of the asphalt high-temperature tank should meet the needs of continuous production of the mixing equipment; the heating equipment heats as little asphalt as possible at the same time; convenient manufacturing and maintenance. The QLB1000 asphalt concrete mixing system of Lianshui County Highway Management Station uses two 50t elliptical horizontal asphalt tanks, with a single tank surface area of 30m².
The heat transfer oil heating equipment is usually heated simultaneously according to the heating equipment. The quality of the insulation asphalt and the size of the asphalt tank are selected.
The heat required for heating asphalt is:
Qadd = qli - qdissipation = M·C (t1-t2)/b + KF (ty-t0)/s
Where Qadd----the heat required for heating asphalt, kj/h, qli----the heat required for asphalt heating, kj/h, qdissipation----the heat lost by the asphalt tank when heating asphalt, kj/h, M----the mass of the heated asphalt, kg, t1----the termination temperature of asphalt heating, ºC, t2----the initial temperature of asphalt, ºC, C----average value of specific heat of asphalt at temperature t1 and t2, kj/kg·ºC, K----heat transfer coefficient of asphalt from tank wall to air, kj/m2·h·ºC, s----heating time, h, F----surface area of horizontal asphalt tank, m2, ty----average temperature of asphalt, ty=(t0+t2)/2, t0----ambient temperature, ºC,
The heat required for insulation asphalt is calculated as follows
Q保=M·C·Δt
Where Q保----heat required for insulation asphalt, kj/h, M----mass of insulated asphalt, kg, C----specific heat of insulation asphalt, kj/kg·ºC, Δt----cooling rate, ºC/h, when the outside temperature is 12--15ºC, the cooling rate is not more than 2ºC/h.
The asphalt temperature of the storage tank is 100ºC, the initial temperature of the high-temperature tank asphalt is 100ºC, the end temperature is 170ºC, the ambient temperature is 10ºC, and the heating time of the high-temperature tank is 2h (s〈MYM /P·k). According to the formula, the maximum heat required for heating and insulation of asphalt can be calculated.
Q大=Q储保+Q高保+Q高加
Where Q大----maximum heat required for heating and insulation, kj/h, Q储保----heat required for storage tank asphalt insulation, kj/h, Q高保----heat required for high-temperature tank asphalt insulation, kj/h, Q高加----heat required for high-temperature tank asphalt heating, kj/h.
Q storage and protection = M storage·C storage·Δt=50×10³×1.6×2=1.6×105kj/h
Q high protection = M high·C high·Δt=10×10³×2.1×2=0.42×105kj/h
Q high plus==M·C(t1-t2)/b+KF(ty-t0)/s=10×10³×1.7(170-100)/2+10×30(135-10)/2=6.14×105kj/h
Q large=8.16×105kj/h
The heating capacity of the heating equipment is calculated as follows:
Q´=Q large/B=8.16×105/0.75=26×104kCal/h
Where Q´----heating capacity, B----thermal efficiency of the heating equipment.
