JPH0220220B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for purifying roasting exhaust gas in a roasting machine mainly used for roasting coffee beans.

<Prior art and its issues> A coffee bean roaster heats and roasts the beans in a roasting chamber, deodorizes the roasting exhaust gas generated in the roasting chamber by passing it through an oxidation catalyst, and then The roasted beans are cooled with air in a cooling tank, and the cooled exhaust gas generated in the cooling tank is passed through an oxidation catalyst to deodorize it.

And when roasting beans for iced coffee,
Since there is no roaster for iced coffee, a roaster for hot coffee is used.

However, when roasting beans for iced coffee, the roasting temperature is higher than when roasting beans for hot coffee, so the temperature of the roasting chamber in the roaster for hot coffee is raised. .

As a result, the temperature of the roasting exhaust gas generated in the roasting chamber increases, and the temperature of the roasting exhaust gas passing through the oxidation catalyst increases.
The temperature rises to 500-600℃, and the oxidation catalyst through which the roasting exhaust gas passes becomes hot.

Oxidation catalysts have a shorter lifespan when exposed to high temperatures.
Furthermore, the amount of nitrogen oxide NOx generated during oxidation increases.

That is, when the roasting temperature is high, such as when roasting beans for iced coffee, the roasting exhaust gas is not purified well.

An object of the present invention is to solve the conventional problems as described above.

<Experiments and points of focus to solve the problem> It has been found that the life of the oxidation catalyst becomes longer as the temperature of the oxidation catalyst becomes lower. Since the relationship between the effect and the temperature of the oxidation catalyst is unknown, it was investigated through experiments.

According to nitrogen oxide experiments, nitrogen oxide NOx
As shown in the diagram of FIG. 1, it has been found that the production amount is greatly influenced by the outlet temperature of the oxidation catalyst and is almost directly proportional to the outlet temperature of the oxidation catalyst.

Judging only from this experimental result, it is better to have a lower outlet temperature of the oxidation catalyst;
At temperatures below 300°C, nitrogen oxides no longer form.

However, according to experiments on the deodorizing effect, when the outlet temperature of the oxidation catalyst falls below 300℃, the hydrocarbon HCs in the roasting exhaust no longer react with the oxidation catalyst, the odor concentration increases, and the deodorizing effect disappears. It has been found.

Therefore, according to these experiments, if the temperature of the roasting exhaust gas passing through the oxidation catalyst is set to around 300℃, the amount of nitrogen oxides produced is small, the deodorizing effect is effective, and the life of the oxidation catalyst is shortened. turned out to be long.

Next, we considered a method for lowering the temperature of the roasting exhaust gas that passes through the oxidation catalyst.

In a roasting machine, the cooling exhaust gas generated in the cooling tank that cools the roasted beans in the roasting chamber has a temperature of 20 to 50 degrees Celsius, which is significantly lower than the roasting exhaust gas. They came up with the idea of lowering the temperature of the roasting exhaust by merging the cooling exhaust with the roasting exhaust.

In this way, the deodorizing device using an oxidation catalyst does not require two units, one for roasting exhaust and one for cooling exhaust, and one
It is economical because it only requires a stand.

However, since the cooling time is shorter than the roasting time and the cooling exhaust gas is not always generated, we came up with the idea of lowering the temperature of the roasting exhaust gas by letting fresh air join the roasting exhaust air when there is no cooling exhaust air.

<Means for Solving the Problems> The present invention heats and roasts beans in a roasting chamber, deodorizes the roasting exhaust gas generated in the roasting chamber through an oxidation catalyst, and roasts the beans in the roasting chamber. In a roaster, the roasted beans are cooled with air in a cooling tank, and the cooled exhaust gas generated in the cooling tank is passed through an oxidation catalyst to deodorize it. The cooled exhaust gas is combined with fresh air when there is no cooled exhaust air to lower the temperature of the roasting exhaust gas before it passes through the oxidation catalyst. The amount of nitrogen oxides produced is small,
Moreover, it is a method for purifying roasting exhaust gas characterized by bringing the temperature to a temperature that has a deodorizing effect through oxidation.

<Function and Effect> In the method for purifying roasting exhaust gas in a roaster of the present invention, even if the roasting temperature is high and the temperature of the roasting exhaust gas generated in the roasting chamber is high, the roasting exhaust gas is not affected by the oxidation catalyst. The temperature is lowered by the confluence of cooled exhaust gas or fresh air before passing through the oxidation catalyst, and when passing through the oxidation catalyst, the amount of nitrogen oxides produced during oxidation by the oxidation catalyst is small, and the oxidation has a deodorizing effect. reaches a certain temperature.

Therefore, even if the roasting temperature is high, the life of the oxidation catalyst is long, the amount of nitrogen oxides produced is small, and there is a deodorizing effect.

That is, when the roasting temperature is high, such as when roasting beans for iced coffee, the roasting exhaust gas can be effectively purified.

<Example> As schematically shown in FIG. 2, the roasting machine of this example has a roasting chamber 1 and a cooling tank 4 located close to each other, and the roasting chamber 1 is collected by a duct 6 with an air blower 5 interposed therebetween. The outlet of the dust collector 7 is connected to the inlet of the filter 9 through a duct 8, and the outlet of the filter 9 is connected to the inlet of the dust collector 7 through a duct 11 with an air blower 10 interposed therebetween. The outlet of the heat receiving passage of the heat exchanger 12 is connected to the inlet of the heating furnace 14 through the duct 13.
The outlet of the deodorizing furnace 16 is connected to the inlet of the deodorizing furnace 16 through a duct 15, and the deodorizing furnace 16 has a built-in platinum-based oxidation catalyst layer 17.
The outlet of the heat exchanger 12 is connected to the inlet of the heat radiation passage of the heat exchanger 12 through the duct 18, and the outlet of the heat radiation passage of the heat exchanger 12 is opened to the atmosphere via the duct 19, and the roasting chamber 1 is discharged to the atmosphere. It forms a purification path for roasting exhaust gas. Furthermore, the cooling tank 4 is connected to the inlet of the dust collector 22 through a duct 21 with a blower 20 interposed therebetween.
The outlet of the filter 2 is connected to the inlet of the filter 9 by a duct 23 to form a purification path for the cooling exhaust gas leaving the cooling tank 4 to the atmosphere, using a part of the purification path for the roasting exhaust gas. Furthermore, a duct 25 with a damper 24 interposed is connected to the outlet of the filter 9, and the end of the duct 25 is opened to the atmosphere to form an air intake path.

When roasting green beans for iced coffee in the roasting machine of this example, the rotary basket 2 in the roasting chamber 1 is rotated, and the burner 3 on the lower side of the rotary basket 2 is ignited, and the roasting exhaust gas is ignited. The blowers 5 and 10 in the purification channel are each driven, the burner in the heating furnace 14 is ignited, the damper 24 in the air intake channel is opened, the green beans are put into the rotary basket 2, and the green beans are heated for about 15 minutes. and roast. When the green beans in the rotary basket 2 are roasted, the blower 20 in the cooling exhaust purification path is driven and the damper 24 in the air intake path is closed, while the roasted beans in the rotary basket 2 are transferred to the cooling tank 4. Take it out, put the next green beans into the rotary basket 2 and roast them in the same way as before, while roasting the roasted beans in the cooling tank 4.
Cool in air. When the roasted beans in the cooling tank 4 are cooled, the drive of the blower 20 in the cooling exhaust purification path is stopped, and the damper 24 in the air intake path is opened to take out the roasted beans in the cooling tank 4.

Then, the roasting exhaust gas generated in the roasting chamber 1 at a temperature of 500 to 600 degrees Celsius, which contains dust and emits an odor, is sent to the dust collector 7 by the blower 5 in the purification path of the roasting exhaust gas, and is dedusted. , is fed into the filter 9 and filtered, then passed through the heat receiving passage of the heat exchanger 12 by the blower 10, fed into the heating furnace 14 and heated, and is also fed into the deodorizing furnace 16. Platinum-based oxidation catalyst layer 1
7 and is deodorized by oxidation, and then passes through a heat radiation passage of a heat exchanger 12 and is discharged to the atmosphere.
However, when the blower 20 in the cooling exhaust purification path is driven and the damper 24 in the air intake path is closed, that is, when roasted beans are being cooled, the cooling tank 4
The cooled exhaust air at 20 to 50°C, which contains dust and gives off an odor, is sent to the dust collector 22 by the blower 20 in the cooling exhaust purification path to be dedusted, and this dust-free cooled exhaust is passed through the filter. 9 and joins the roasting exhaust,
The temperature of the roasting exhaust air is lowered, and the combined exhaust gas, which is lower temperature than the roasting exhaust gas, is sent to the filter 9, the blower 10, the heat receiving passage of the heat exchanger 12, the heating furnace 14, the deodorizing furnace 16, and the heat exchanger 12.
The temperature of the combined exhaust gas that is released into the atmosphere through the heat dissipation passage and passes through the platinum-based oxidation catalyst layer 17 of the deodorizing furnace is such that the amount of nitrogen oxides produced is small and the deodorizing effect is high.
The temperature will be around 300℃. Furthermore, when the blower 20 in the cooling exhaust purification path is stopped and the damper 24 in the air intake path is open, that is, when the roasted beans are not being cooled, the blower 1 in the roasting exhaust purification path is
0, fresh air is taken into the outlet of the filter 9 through the air intake passage 25, and the fresh air at room temperature joins the roasting exhaust air to lower the temperature of the roasting exhaust air and cool the roasted beans. The temperature of the combined exhaust gas passing through the platinum-based oxidation catalyst layer 17 of the deodorizing furnace reaches a temperature of about 300°C.

Therefore, even if the roasting temperature is high for roasting green beans for iced coffee, the life of the platinum-based oxidation catalyst layer 17 is long, the amount of nitrogen oxide produced is small, and the deodorizing effect is achieved.

That is, when the roasting temperature is high, such as when roasting green beans for iced coffee, the roasting exhaust gas can be effectively purified.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between nitrogen oxides and oxidation catalyst outlet temperature in a roasting machine, and FIG. 2 is a schematic diagram of a roasting machine implementing the method for purifying roasting exhaust gas according to an embodiment of the present invention. It is a diagram. 1: roasting chamber, 4: cooling tank, 17: platinum-based oxidation catalyst layer.

Claims (1)

[Claims] 1. Beans are heated and roasted in a roasting chamber, and the roasting exhaust gas generated in the roasting chamber is deodorized by passing through an oxidation catalyst,
In a roaster, beans roasted in a roasting chamber are cooled with air in a cooling tank, and the cooled exhaust gas generated in the cooling tank is passed through an oxidation catalyst to deodorize it. The cooled exhaust gas before passing through the catalyst is combined, and when there is no cooled exhaust air, fresh air is combined to lower the temperature of the roasting exhaust gas before passing through the oxidation catalyst. The amount of nitrogen oxides produced during oxidation by an oxidation catalyst is small,
A method for purifying roasting exhaust gas characterized by bringing the temperature to a temperature that has a deodorizing effect through oxidation.