How to improve the heavy oil thermal recovery of waste heat from flue gas of steam injection boiler in oil field?
As the main production position at the present stage of oilfield production, heavy oil thermal recovery plays a key role in the stable supply of crude oil in China. Steam injection boiler, the key equipment of heavy oil thermal recovery, is an important guarantee for heavy oil production. With the continuous strengthening of energy-saving requirements for high energy consumption equipment, how to further improve the thermal efficiency of steam injection boiler and reduce the energy consumption per unit steam has become the key point to save energy, reduce consumption and reduce the input-output ratio per ton of heavy oil.
Summary of the invention
Waste heat recovery refers to the recycling and reuse of waste heat generated by industrial processes. The main technologies include heat exchange technology, heat power conversion technology, and waste heat refrigeration and heating technology. The industrial waste heat resources are abundant and widely exist in the production process of various industries. The waste heat resources account for about 17% to 67% of the total fuel consumption, of which the recovery rate is 60%. Industrial waste heat recycling is considered a “new energy”.
There is a large amount of waste heat in the flue gas discharged from steam injection boiler. At present, most steam injection boilers do not have flue gas waste heat utilization devices, and only a few of them are installed with flue gas waste heat recovery devices. These flue gas waste heat recovery devices generally use flue gas to preheat combustion air or flue gas to preheat boiler feed water. These two flue gas waste heat recovery methods only recover part of sensible heat in flue gas, due to the large proportion of water vapor in the flue gas of gas-fired boiler, and the latent heat of steam vaporization is large.
In view of the above defects in the existing technology, Sanjack company provides a condensing oil field steam injection boiler flue gas waste heat recovery device and method, which is installed above the convection section of the original steam injection boiler to recover the waste heat of flue gas, improve the boiler feed water temperature, reduce the exhaust gas temperature, improve the thermal efficiency of the boiler, effectively reduce the operation cost of the boiler, with reasonable layout, compact structure, and easy installation, maintenance and replacement. The technical scheme is as follows: the inner wall of the pipe ring support is welded with heat preservation fixed parts to fix the inner insulation layer; the heat absorbing pipe group is welded by the finned tube and elbow to form a water supply circulation channel, including the upper tube group and the lower pipe group;
the flue gas uniform distribution guide plate and condensate water collection plate are inclined welded and fixed on the pipe ring support; After the flue gas absorbs heat through the lower tube group of the heat absorption tube group, when it reaches the flue gas uniform distribution guide plate and condensate water collection plate, its temperature has dropped to the flue gas dew point, and then enters the upper tube group through the flue gas uniform distribution guide plate and condensate water collection plate, and the flue gas flows through the Z-shaped curve, so that the water vapor in the flue gas changes from gas condensation to liquid state, thus releasing the latent heat in the flue gas.
Fig. 1 is a structural diagram of the device;
Heat absorption tube group (1), external insulation box (2), pipe ring support (3), inner insulation layer (4), heat preservation fixing parts (5), flue gas uniform distribution guide plate (6), condensate collection plate (7) , heat insulation sleeve (8), water inlet pressure transmitter (9), water inlet temperature transmitter (10), condensate discharge pipe group (11), outlet pressure transmitter (12), outlet temperature transmitter (13)
Fig. 2 is the front schematic diagram of the device installed in the steam injection boiler;
Fig. 3 is a side diagram of the device installed on the steam injection boiler;
In embodiment 1, the flue gas of steam injection boiler mentioned in this tech reduces the temperature from 230 ℃ (oil fired boiler) to 80 ℃ (oil fired boiler) through heat exchange with boiler feed water from bottom to top, and the feed water of 20 ℃ increases the temperature to 70 ℃ from top to bottom. Take the gas-fired boiler as an example: when the flue gas temperature drops to about 45 º C, more than half of the water vapor in the flue gas condenses, and the latent heat utilization rate is 51.4%. Most of the sensible heat has been absorbed, and the utilization rate of sensible heat has reached 75%.
After the boiler feed water is increased to 70 º C through flue gas waste heat exchange, it will not have any impact on other boiler auxiliaries and accessories. The purpose of improving boiler thermal efficiency and reducing smoke exhaust heat loss is achieved.
This tech adopts an overall combined design to ensure the function of the whole system; The whole set of equipment of the utility model has the advantages of reasonable layout, compact structure, easy installation, maintenance and relocation, and can effectively improve the thermal efficiency of the steam injection boiler by more than 5%. The device does not need personnel to operate during operation, so as to realize the automatic operation of the whole device.