JPS6123473B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for recovering heat from waste liquid containing inorganic salts.

For incineration of waste liquid containing a large amount of inorganic salts,
In most cases, a submerged combustion system was used, and heat recovery from the incineration exhaust gas was generally not performed. However, recently, from the standpoint of energy conservation, it has become necessary to recover heat from the incineration exhaust gas even in this case.

When waste liquid containing inorganic salts is incinerated in an incinerator of a submerged combustion system, inorganic salts are deposited on the furnace wall. This inorganic salt melts and flows down the furnace wall, and simultaneously flows into the water as the incineration exhaust gas flows out into the water, where it is dissolved and recovered. However, when the inorganic salt is precipitated, a considerable amount is scattered in the incineration exhaust gas. For this reason, when incineration exhaust gas from a normal liquid waste incinerator, including a submerged combustion equipment, is directly introduced into a heat recovery device such as a boiler for heat recovery, a considerable amount of inorganic salts entrained in the exhaust gas is transferred to the boiler tube. It adheres to walls, etc., and has a negative impact on heat exchange efficiency and service life. Furthermore, releasing incineration exhaust gas that has undergone heat recovery into the atmosphere as it is is problematic due to its relationship with salt concentration.

The present invention proposes a heat recovery method that can completely eliminate the various inconveniences mentioned above when recovering heat from incineration exhaust gas of waste liquid containing inorganic salts. This will be explained based on the diagram.

The inorganic salt-containing waste liquid W is temporarily stored in the waste liquid storage tank 1, and is supplied to the bottom of the heater 2 by the pump _P1 . Steam S is supplied to the heater 2, and the waste liquid W is heated by the steam S in a countercurrent manner while passing through the heater 2. As the steam S, steam S _A introduced from outside the system is used at the beginning of operation, and thereafter, steam S _P obtained by recovering heat from the incineration exhaust gas is used. The steam S is condensed through heat exchange with the waste liquid W, and is discharged from the heater 2 as condensed water _d1 , and then drained into the drain tank 3.
is stored in Heated waste liquid coming out from the top of heater 2
The Wh reaches the evaporator 4, where it is condensed to become a concentrated waste liquid Wc containing a high concentration of inorganic salts. The steam Sw generated in the evaporator 4 reaches the condenser 5 after leaving the evaporator 4, and after being condensed, the condensed water is transferred to the drain tank 3.
It is introduced as _d2 and stored temporarily. generated steam
Sw is heat exchanged with cooling water Cw in the condenser 5 in a countercurrent manner. On the other hand, the concentrated waste liquid Wc is taken out from the bottom of the evaporator 4, a part of which is circulated by pump P ₂ to the heater 2 where it joins with the waste liquid W before concentration, and the rest is incinerated by pump P ₃ . It is fed under pressure to the furnace 6. The incinerator 6 is of a cyclone type, and its body 7
A plurality of concentrated waste liquid nozzles 9 are installed in the combustion chamber 8 in the combustion chamber 8 so as to face in the tangential direction thereof. These nozzles 9 simultaneously discharge concentrated waste liquid from all of them.
Wc is not ejected, but is controlled so that it is ejected sequentially from each one for a certain period of time. This is based on the experimental result that if the concentrated waste liquid Wc is sprayed onto the furnace wall as coarse particles instead of fine particles, entrainment of inorganic salt particles onto the furnace wall _g1 can be minimized. A burner 10 is provided directly above the nozzle 9. This burner 1
0 is also directed in the tangential direction of the combustion chamber 8 based on the experimental results. The burner 10 is supplied with uncondensed steam V discharged from the condenser 5 in addition to the auxiliary fuel f and the primary and secondary combustion air a. Note that B ₁ is a combustion air blower, and B ₂ is an uncondensed steam blower. An outlet pipe 11 for incineration exhaust gas _g1 is connected to the top of the incinerator 6, and an inorganic salt outlet 12 is formed at the bottom. The outlet 12 is immersed in liquid stored in a closed liquid tank 13. This liquid is the condensed water stored in the drain tank 3.
d ₁ , d ₂ and process water Pw are pumped by pump P ₄ and are extracted by pump P ₅ for recovery of inorganic salts dissolved in the liquids.
When the concentrated waste liquid Wc is burned in the combustion chamber 8, the waste liquid Wc
The moisture inside evaporates, and the combustible content gasifies to become incineration exhaust gas g ₁ . In addition, the inorganic salt precipitates and adheres to the furnace wall, and is then discharged and recovered outside the incinerator 6 through batch operations of melting, flowing down, flowing out into the liquid from the outlet 12, and dissolving. At this time, the inorganic salt is removed from the outlet 12.
A part of the incineration exhaust gas g ₂ is jetted out from the outlet 12 in order to easily flow out from the outlet 12 and to prevent the outlet 12 from being blocked by inorganic salt precipitation.
This operation is carried out by suctioning the gas phase portion of the liquid tank 13 at an appropriate pressure using the blower _B3 . This operation also eliminates the risk of smelt explosion. The amount of incinerated exhaust gas ejected from the outlet 12 may be a few percent of the total amount of incinerated exhaust gas generated in the combustion chamber 8, and since this incinerated exhaust gas _g2 passes through the liquid, inorganic salts are completely removed and it is cooled. be done. On the other hand, the remaining incineration exhaust gas g ₁ passes through the outlet pipe 11 and reaches the heat recovery boiler 14 .
Since this incineration exhaust gas _g1 is the majority of the total amount of incineration exhaust gas generated in the combustion chamber 8, it is a sufficient amount to be used for heat recovery.Moreover, since it is obtained by incinerating the concentrated waste liquid Wc, almost no inorganic salt is entrained. I haven't. Figure 2 shows experimental results to prove that inorganic salts are not entrained in the incineration exhaust gas g ₁ of the concentrated waste liquid Wc. In Figure 2, A represents the total amount of inorganic salts in the waste liquid W from 20 to 80% (NaC = 10 to 20%,
B is the inorganic salt scattering rate curve when waste liquid W is incinerated and concentrated to 10% (Na ₂ SO ₄ = 10%).
It shows the inorganic salt scattering rate curve when incinerated with Na ₂ SO ₄ = 5%). From this result, it is clear that the amount of inorganic salts scattered and entrained in the incineration exhaust gas is reduced when waste liquid with a high concentration of inorganic salts is incinerated. Therefore, there is almost no inorganic salt entrained in the incineration exhaust gas _g1 , and the investigation results show that it only contains about 0.1 g/m ³ of inorganic salt as a dust component. Therefore, the amount of inorganic salts recovered by the above-mentioned batch operation is 99.5% or more of the total amount, and the amount of incineration exhaust gas _g1 that can be used for heat recovery can be 95% or more of the total amount generated. . Moreover, since almost no inorganic salt is entrained in the incineration exhaust gas g ₁ , the amount of inorganic salt adhering to the outlet pipe 11 or the pipe wall of the boiler 14 is also extremely small, making it possible to minimize the decrease in heat exchange efficiency. I can,
It has now become possible to easily remove adhering salts by a soot blowing operation performed once every 2 to 3 days. In addition, incineration exhaust gas after being subjected to heat recovery g ₁
It is no longer necessary to perform operations such as dust removal and smoke cleaning.
No problem will occur if it is released into the atmosphere as is. In addition, since the amount of water in the concentrated waste liquid Wc has been evaporated and removed in advance according to its degree of concentration, the amount of auxiliary fuel f for gas sensible heat can be omitted when incinerating it, and the amount of water in the concentrated waste liquid Wc can be omitted. It is possible to reduce the amount of exhaust gas generated commensurately with the amount of waste gas generated. Therefore, incinerating the concentrated waste liquid Wc has the practical benefit of reducing running costs, in addition to increasing the amount of salt trapped in the furnace and reducing the amount of salt entrained in the incineration exhaust gas g. The incineration exhaust gas g ₁ that has been subjected to heat recovery in the boiler 14 then joins with the cooled incineration exhaust gas g ₂ from the blower B ₃ and is emitted from the chimney 15 into the atmosphere. In this case, the incineration exhaust gas g ₂ from the blower B ₃ is a saturated wet gas, but since it joins the dry incineration exhaust gas g ₁ , the situation where white smoke is emitted when dissipating into the atmosphere is prevented. Ru. The process water Pw supplied to the boiler 14 is discharged as boiler-generated steam Sp, and then becomes the steam S supplied to the heater 2. In addition, almost no COD content is detected in the smoke washing wastewater Ws containing dissolved inorganic salts.
This is because the concentrated waste liquid Wc is completely incinerated.

As detailed above, according to the present invention, the inorganic salt-containing waste liquid is heated and concentrated to increase the concentration of inorganic salts, and is further supplied as coarse particles to a cyclone-type incinerator and incinerated, thereby entrained in the incineration exhaust gas. This greatly reduces the amount of inorganic salts attached to the pipe wall of the incineration exhaust gas conduit of the heat exchange equipment, increases the heat exchange efficiency, facilitates maintenance, and reduces the running cost of the pipe wall. In addition, it is possible to directly dissipate the incineration exhaust gas into the atmosphere, increasing the amount of salt trapped in the furnace, and the heat from heat recovery can be used to heat and concentrate inorganic salt-containing waste liquid, making it more efficient. This enables efficient operation and highly efficient heat recovery as a whole.

[Brief explanation of the drawing]

FIG. 1 is a flowchart for implementing the method of the present invention, and FIG. 2 is a graph of experimental results. 2... heater, 4... evaporator, 6... incinerator,
14...Heat recovery boiler, W...Waste liquid, Wc...Concentrated waste liquid, _g1 , _g2 ...Incineration exhaust gas.

Claims (1)

[Claims] 1 After heating and concentrating the inorganic salt-containing waste fluid, it is supplied as coarse particles to multiple locations in the circumferential direction of the inorganic salt in a cyclone type incinerator and incinerated, and the generated salt is recovered, and heat is recovered from the incineration exhaust gas, and the recovered heat is A method for recovering heat from an inorganic salt-containing waste liquid, characterized in that the method is used for heating and concentrating the inorganic salt-containing waste liquid.