JPS5955397A - Operating method of digestion tank - Google Patents

Abstract

PURPOSE:To maintain exactly the sludge in a digestion tank at a prescribed temp., by calculating the temp. and flow rate of the sludge charged into the digestion tank and the quantity of heat required for heating the sludge with a control device and heating the heating water with a boiler when the waste heat of a gas engine is short. CONSTITUTION:A control device 22 controls the operation of a gas engine according to the volume of the gas measured with a flowmeter 8 to maintain the output of a generator 10 always constant. Said device calculates the quantity of heat that can be recovered from the gas engine 9 and calculates the quantity of heat reguired for heatint the sludge from the temp. and flow rate of the charged sludge measured with a thermometer 23 and a sludge flowmeter 3 and the temp. of the sludge in a primary digestion tank 1 measured with a thermometer 24. The control device compares the results of the calculations, and when the quantity of the recovered heat is smaller than the quantity of the heat required for heating in a winter season or the like, the control device closes a selector valve 20 and opens selector valves 19, 21 to operate and control a hot water boiler 15 thereby making up the deficient quantity of heat.

Description

[Detailed description of the invention] The present invention relates to a method for operating a digester.

When treating sewage, human waste, industrial waste, etc., a digestion tank is often used to decompose and digest organic matter in sludge into desorbed liquid, gas, and digested sludge through the action of sickling bacteria. In such a digestion tank, it is necessary to always maintain the temperature of the sludge in the digestion tank at a predetermined temperature, and for this reason, conventionally, a first boiler that uses digestion gas such as methane gas generated in the digestion tank as fuel has been used. and a second boiler that uses kerosene or heavy oil as fuel, and the first boiler or the first and second boilers generate steam and supply this steam directly into the digester.

However, in such a conventional operation method, the digestion gas is used only for heating the sludge, and is not used in the pond at all. In addition, at low temperatures such as in winter, the first boiler, which uses digestion gas as fuel, does not have enough heat, so a second boiler, which uses kerosene or heavy oil as fuel, is used in combination. Steam is generated by the second boiler and these steams are directly extinguished independently of each other) Convex circle i(j) It was difficult to maintain the temperature of the sludge, and it was not possible to keep the temperature of the sludge accurately constant.Furthermore, all operations were performed based on human judgment, resulting in high labor costs and the risk of x-h'> cropping. There was also.

In view of the above-mentioned points, the present invention has been developed to provide a digester system that can effectively utilize digestion gas for purposes other than heating sludge, and that can maintain the sludge in the digester at a predetermined temperature accurately even during low temperatures such as winter. The purpose is to obtain a method.

That is, the operation of the digestion tank according to the present invention≠ #Right method, the digestion gas generated in the digestion tank drives a gas engine to obtain power, and the waste heat of the gas engine warms the sludge in the digestion tank. The control device calculates the amount of heating heat necessary to bring the sludge to a predetermined temperature from the temperature and flow rate of the sludge input into the digestion tank and the temperature of the sludge in the digestion tank. and controlling the temperature of the heated water so that the required amount of heating heat is obtained from the heated water, and further controls the boiler to increase the temperature of the heated water when there is a shortage in the waste heat of the gas engine. Since the gas engine is driven by the digestion gas, electric power can be obtained by driving a generator, for example, and the waste heat of the gas engine can also be used to generate heated water. Since the sludge is heated through the boiler, this method is compared to the conventional method in which digestion gas is used as boiler fuel to generate steam in the boiler, and this steam is directly fed into the digestion tank to heat the sludge. It is possible to obtain approximately the same thermal efficiency in heating sludge,
Overall it is very economical in terms of energy. In addition, if there is a shortage of waste heat from the gas engine during low temperatures such as in winter, the boiler is controlled to further heat the mk water heated by the gas engine's waste heat, and this heated water is used to Since the sludge is heated, it is relatively easy to control the temperature of the heated water, and even if there is a short temperature change of 1υ in the heated water, there is almost no change in the temperature of the sludge. Sludge can be accurately maintained at a predetermined temperature.

Hereinafter, one embodiment of the present invention will be described based on the drawings. In the figure, (1) is the fire extinguisher, (2) is the secondary digestion tank, - the fire extinguisher (1) is fed with sludge via a sludge flow meter (3), and the - fire extinguisher is The sludge in seed (1) is transferred to a double-pipe heating heat exchanger (5) by a sludge circulation pump (4).
). -Fire extinguishing +1; (1)
The sludge that has been treated for a predetermined period of time is fed to the secondary digestion tank (2), and after being treated for a predetermined period of time in this secondary digestion tank (2), the digested sludge is transferred to dewatering equipment using a sludge extraction pump (6). (not shown) and the de-111 liquid is sent to a water treatment facility (not shown). Digestion gas such as methane gas generated inside the upper fire extinguishing tank (1) and the secondary fire extinguishing tank (2) is stored in the gas tank (7), and is stored in the gas tank (7).
Gas flow from 7) through meter (8) to gas engine (9
) is given fJI==Qi.

This gas engine (9) drives the s ton m Of) to generate four forces. The exhaust gas of this gas engine (9) is used as a cooling heat pump (1) and a heat exchanger (1) for cooling.
6) R'Ls discharged to the atmosphere through the engine cooling water pumps α, b*, ;a + therapeutic heat exchanger (i4) is circulated. Yes, fuel such as kerosene or heavy oil is supplied from the oil tank head to this hot water, to, and irra 0 itch.f5iJ
The fire-extinguishing species (1) passing through the heat exchanger (5)
) The hot water for heating the sludge is supplied from the heating heat exchanger (5) by the hot water circulation pump θ at a flow rate of 810 barrels,
The exhaust gas heat exchanger F (and; the flow path returning to the heating heat exchanger (5) via the cooling heat exchanger θ station is circulated, or the waste heat heat exchanger α After passing through the hot water boiler (IQ), the water is circulated through a flow path that returns to the heating heat exchanger (5) via the hot water boiler (IQ).Switching between these two flow paths can be performed by a switching valve 0 [→◇]. 2 is the control device u, and this control device The signal from (3) and the thermometer (c) that measures the temperature of the sludge in the blowing and digestion tank (1) θ11
and a signal from a thermometer that measures the temperature of the heated water flowing out from the BAH heat exchanger (5),
The signal from the hot water flow meter (to) and the signal from the Sass flow fJ meter (8) are electrically input, and the signal from the Sass engine (9) and the engine cooling water are inputted electrically. A control signal is output to the pump tank 1M and the hot water boiler θ0, and a control signal is also output to the switching valves (II to Qυ, not shown).

The control value @) controls the operating state of the gas engine (9) according to the amount of gas measured by the gas flow meter (8),
The gas engine (9) is always running at full capacity and the generator (1 (
) output is always constant.

In addition, the amount of heat that can be recovered from the gas engine (9) is calculated, as well as the temperature and flow rate of the input sludge measured by the thermometer) and sludge flow meter (3), and the temperature and flow rate of the input sludge measured by the thermometer (c). The heat U required to heat the sludge circulated by the sludge circulation pump (4) is calculated from the temperature of the sludge in the digester (1). Then, these calculation results are compared, and if the amount of recovered heat is greater than the required humidification heat H1, for example in the summer, the surplus energy that can be sent to the heat pump Oυ is calculated and the heat pump αυ is operated and controlled. At the same time, the engine cooling water pump α;1 is controlled to adjust the amount of cooling water so that the amount of recovered heat is equal to the required amount of heating heat. For example, in winter, when the recovered heat energy is less than the required heating heat amount, the switching valve (E) is closed and the switching valve 01020 is opened, the hot water boiler (C) is operated, and the hot water boiler is controlled by control 1. Ura now.

In this way, the gas engine (9) is
Therefore, for example, as in this embodiment, electric power can be obtained by generating electricity with this gas engine (9) and driving (13, α(), and this power can be used effectively in a processing field, etc. In addition, heated water is heated by the exhaust gas and cooling water of the gas engine (9) via the exhaust gas heat exchanger (2) and the waste heat heat exchanger Q4), and this heated water is used for heating purposes. Since the sludge in the primary d3 conversion tank (1) is heated via the heat exchanger (5), steam is generated using a boiler fueled with digestion gas and this steam is used in the primary Compared to the case where the sludge is directly injected into the digester, approximately the same thermal efficiency can be obtained in terms of heating the sludge. therefore,
Overall, energy can be used effectively and it is very economical. In addition, the operation can be fully automated using the control device).
It is possible to reduce labor costs and prevent operational errors. Furthermore, as in this embodiment, when the amount of recovered heat exceeds the required amount of heating heat during high temperatures such as in summer, the heat pump This method is significantly more economical than the method in which surplus digestion gas was burned and disposed of without any use. In addition, when the amount of heat recovered is less than the amount of heating heat required during low temperatures such as winter, the heated water heated by the waste heat of the gas engine (9) is further heated by the hot water boiler (lie), so the temperature of the heated water is increased. can be controlled relatively easily, and since the heated water heats the sludge of the primary digestion i'l (1), even if there is a short temporal temperature change in the heated water, the sludge temperature will not fluctuate. Since there is almost no sludge, the sludge can be accurately maintained at a predetermined temperature.

In the above embodiment, the heat pump/1]) is operated during high temperatures such as summer to perform air conditioning using the surplus of recovered heat, but it is not necessary to do this, for example, when the recovered heat (2) The surplus may be used for drying the digested sludge after dehydration treatment.

As explained above, according to the operating method of the digestion tank according to the present invention, the gas engine is QIjed by the digestion gas, and the waste heat of the gas engine is used to heat the sludge via the heated water. The power of the engine can be effectively used for power generation, etc.121), which is very economical compared to the conventional case where the digestion gas is used only for heating the sludge. In addition, during low temperatures such as winter, the heated water heated by the waste heat of the gas engine is further heated by the boiler.
The heated water is used to heat the sludge, so the temperature of the sludge can be accurately maintained at a predetermined temperature.Also, since the operation is automated by a control device, labor costs can be reduced and there is no risk of erroneous operation.

[Brief explanation of drawings]

The drawing is a block diagram of a piston system of a fire extinguisher (a) showing an embodiment of the present invention. ...Sludge flow meter, (5)...Heating heat exchanger, (9)...Gas engine, θQ...Exhaust gas heat exchanger, 0→...13J heat exchange): d, θ pupil...
Hot water boiler, θQ...oil tank, θtO-aυ
...Switching valve, (A) ...Control device, +23 (C).
... Temperature d1 agent Yoshihiro Teramoto

Claims (1)

[Claims] 1. The digestion gas generated in the digestion tank drives a gas engine to obtain power, and the waste heat of the gas engine heats heated water for heating the sludge in the digestion tank, and the control device: From the temperature and flow rate of the sludge input into the digestion tank and the temperature of the sludge in the digestion tank, calculate the necessary amount of heating heat necessary to bring the sludge to a predetermined temperature, and from the heated water 1) 1. A digestion tank characterized in that the temperature of the heated water is controlled so as to obtain the required amount of heating heat, and further, when the heat of the gas engine is insufficient, the boiler is controlled to heat the heated water. How to drive E.