JPS5833040B2 - Anaerobic treatment equipment - Google Patents

Description

[Detailed description of the invention] This invention is applicable to organic sludge and organic waste liquid (also referred to as undiluted liquid).

) is used for methane fermentation to recover gas as an energy source for boilers, gas engines, etc., and is particularly effective for processing sulfur-containing protein stock solutions that contain sulfides, such as those discharged from amino acid manufacturing processes. This invention relates to an anaerobic treatment device for methane fermentation.

In recent years, methane-containing gas (also referred to as digestion gas) has been produced as energy from the above-mentioned stock solution.

) is frequently subjected to methane fermentation to recover the methane, and in order to efficiently carry out the methane fermentation, the stock solution is converted to volatile low molecules such as acetic acid, propionic acid, and butyric acid by a group of anaerobic liquefaction bacteria. A two-phase anaerobic digestion method that has two reactions: a liquefaction reaction (acidogenic phase) in which organic acids are converted into organic acids, and a methanation reaction (methane generation phase) in which the organic acids produced in this way are converted to methane by a group of methane bacteria. is publicly known.

The reaction efficiency of each reaction in this two-phase anaerobic digestion method can be increased by maintaining the pH and temperature at which bacterial groups are most active. In the production phase, 7 to 8 is optimal.

For this reason, pH adjusters such as slaked lime have traditionally been used in the acid generation phase, but in addition to the disadvantage of increasing chemical costs, volatile organic acids decompose in the methane generation phase, causing an increase in pH. This has the disadvantage that the amount of digestive gas produced decreases due to the phenomenon of excessive water consumption.

Therefore, in order to eliminate the above-mentioned drawbacks, the present invention optimally adjusts the pH in the acid generation phase without using a special pH adjuster, thereby improving the amount of digestion gas produced in the methane generation phase. That's what I did.

Hereinafter, the present invention will be described with reference to the drawings. The first reaction tank 1 is an acid production phase and the second reaction tank 2 is a methane production phase. The gas is supplied, undergoes a liquefaction reaction by a group of anaerobic digestive bacteria in this X, and is then supplied to the second reaction tank 2, where a methanation reaction is performed by a group of methane bacteria to generate digestive gas and remove the desorbed liquid. becomes.

The digestion gas generated in each of the second reaction tanks is desulfurized by being desulfurized through a pipe 3 to a known desulfurization device 4, such as a gas-liquid contact type desulfurization device in which it is brought into contact with an alkaline solution, and then led to a digestion gas storage tank 6 through a pipe 5. It is stored and supplied as energy key to boilers and gas engines as needed.

Further, the desorbed liquid generated in the second reaction tank 2 is led to a known aerobic treatment device (not shown), treated, and then discharged.

Now, conventionally, a pH adjusting agent such as slaked lime was injected into the first reaction tank 1 using a chemical dosing device to maintain the pH at 5 to 6, which caused the problems mentioned above, especially the production of digestion gas in the second reaction tank. This resulted in a fatal drawback: the amount decreased.

Therefore, the present invention feeds back the desulfurized digestion gas to the first reaction tank 1, aerates the raw solution in the tank, and strips hydrogen sulfide (H2S) generated in the first reaction tank by the liquefaction reaction. A pipe 7 is provided between the storage tank 6 and the first reaction tank 1.

The first layer that tries to fall due to the hydrogen sulfide generated by this
The pH in the reactor does not drop because the hydrogen sulfide is stripped off by the digestion gas.

In fact, hydrogen sulfide can be easily stripped by this aeration, and therefore the amount of digestion gas fed back to the first reaction tank 1 can be adjusted to keep the pH in the acid production phase optimal.

Therefore, the reaction in the acid generation phase proceeds well without adding a p)l regulator such as slaked lime, and when it is subsequently supplied to the second reaction tank, the pH does not rise too much.
However, by maintaining the optimum pH of 7 to 8, the reaction progresses well, and compared to conventional methods, it takes less time to complete, the yield increases, and overall the operation progresses very smoothly.

and hydrogen sulfide stripped in the first reaction tank;
For this purpose, the surplus of the digestive gas supplied is directly led to the desulfurization equipment through a pipe 8, or this pipe 8 is connected to the pipe 3 that leads the digestion gas generated in the second reaction tank to the desulfurization equipment 4 as shown in the figure. Hydrogen sulfide is removed, and the digestion gas is collected in a storage tank 6.

Therefore, the total amount of digested gas obtained does not decrease.

The first reaction tank may be of a type in which the sludge containing the anaerobic liquefied bacteria is stirred and dispersed by the digestion gas fed back through the pipe 7 and mixed with the stock solution, or it may be equipped with a mechanical stirring device and the stirring power of the digestion gas may be If this alone is insufficient, this mechanical stirring device may be driven to compensate for the deficiency.

In addition, the reactor is equipped with a rotating disk that is entirely immersed in the liquid, and the sludge adheres to this rotating disk in a film form to advance the reaction, and the digestion gas is attached to the rotating disk. The sludge film may be fed into the tank without peeling off.

In addition, the second reaction tank, like the first reaction tank, is a reaction tank in which substantially oxygen-free gas or sludge containing methane bacteria is stirred and dispersed using a mechanical stirring device, or a rotating disk type fixed bed type reaction tank. It can be a reaction tank.

As described above, the present invention uses the generated digestive gas to adjust the pH of the acid generation phase, so there is no need for chemicals as in the past, and additional costs such as a dissolution tank and injection device for the pH adjuster are required. Since no equipment is required, equipment costs are lower, and the yield of the generated digestion gas is not reduced.

Furthermore, it is possible to implement the method by simply modifying a conventional device, which has the great effect of eliminating the cost of pH-adjusting chemicals from running costs.

The amount of digestion gas supplied to the first reaction tank is determined by the p of the first reaction tank.
It may be controlled in conjunction with the H meter.

[Brief explanation of drawings]

The drawing shows a flow sheet of an embodiment of the present invention, and in the drawing,
1 is a first reaction tank (acid production phase), 2 is a second reaction tank (methane production phase), 4 is a desulfurization device, 6 is a digestion gas storage tank, 7 is a pipe that supplies digestion gas to the first reaction tank, Reference numeral 8 indicates piping that leads gas from the first reaction tank to the desulfurization device.

Claims (1)

[Scope of Claims] 1. A first reaction tank that uses organic sludge or organic waste liquid as a stock solution and performs an acid production reaction thereon, and a second reaction tank that receives the organic acid produced in the first reaction tank and performs a methane production reaction thereon. In an anaerobic treatment device including two reactions having two reaction tanks, a pipe for guiding gas generated from both the first reaction tank and the second reaction tank, a desulfurization device installed in this pipe, and a desulfurization device An anaerobic treatment device characterized by having a pipe for supplying the treated gas to a first reaction tank.