JPH044496B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides solid carbonaceous fuels other than coal.
The present invention relates to a method for facilitating the removal of deposits forming on walls and heat exchange surfaces in industrial furnaces or utility boilers burning carbonaceous fuel.
This is an effective amount of uncalcined vermiculite
vermiculite) from approximately 1649℃ to 649℃ (approximately 3000〓
Preferably 0.023 to 45 Kg (0.05 to 100 lb) of vermiculite per ton of fuel burned, more preferably 0.23 to 4.5 Kg (0.5 〜10
lbs. Vermiculite increases the friability of deposits, making them easier to remove by conventional soot blowers (i.e., by removing air or water vapor from approx.
probe placed inside the boiler blowing at 200 psig).

The minerals (ash) in the solid carbonaceous fuel become deposits in the endothermic areas of the boiler, especially in the superheater and convection paths. These sintered flyash deposits can be stronger than normal cleaning equipment is capable of. We have found that by injecting vermiculite, the strength of the deposits is reduced in order to maintain a clean heat exchange surface and prevent future blockage of these pathways.

Vermiculite is a naturally occurring mineral, approximately
When exposed to temperatures above 649°C (approximately 1200°C), it expands to 15 to 20 times its original volume. This results in sintering (bonding) in which vermiculite is present.
The strength of the deposit is severely reduced. Previously, chemical and physical properties of materials such as magnesium oxide, alumina, etc. have been used to damage sinter deposits. Vermiculite is superior to these additives.

Vermiculite, a hydrated magnesium-aluminum-iron silicate, is composed of 14 closely related mica minerals. unextoliated
When vermiculite is used in a way that is incorporated into ash deposits and exposed to the range of temperatures encountered in superheaters and convection zones, a dramatic reduction in the strength of the bound deposits is evident. be. Unique properties that explain this activity include thermally induced exfoliation (swelling) and the presence of naturally occurring platelet structures (silica sheets) that act as cleavage planes. The deposit is
This treatment results in much easier removal.

We recommend that the vermiculite be relatively finely ground, eg, approximately 3 to 325 mesh (Tyler Screen), even more preferably approximately 28 to 200 mesh.

To our knowledge, green vermiculite has never been injected into the hot end of a furnace for any purpose. In the prior literature, calcined (expanded) vermiculite is heated at the cold end of the furnace (82-182 °C (180-360 °C) to absorb the sulfuric acid that adheres to the metal surface.
〓)) was injected into. BLLibutti, A., C.S.
Centennial Meeting, New York, NY April
4-9, 1976, Symposium on Heavy Fuel
Oil Additives.

Solid Addition Device Preferably, an air-cooled probe is used to inject the vermiculite into the furnace. This probe is approximately 3 feet long and consists of a single piece of steel tubing. The vermiculite is delivered from the hopper by a screw-type feeder that meters the vermiculite into a pneumatic conveying system that delivers the vermiculite to the probe.
The air flow cools the probe as the vermiculite is pumped into the boiler.

Babcock
The sintering test developed by
It was used to determine the clogging tendency of various ash (formation of bonded deposits) and the effect of additives.

“Sintering test, indicator of ash clogging tendency (The
Sintering Test, An Index to Ash−Fouling
Tendency)” DHBernhart and PC
Williams, Transactions of the ASME, 1956.
See August, p. 1229. In summary, this test consisted of forming the ashes into pellets, heating them to various high temperatures for 15 hours, and measuring the force required to break the resulting sintered samples.

A number of solid carbonaceous fuels are available for use with vermiculite in the method of the present invention. Such fuels include lignite, peat, sunflower seed hulls, wood, wood chips, paper, paper by-products, garbage, garbage-based fuels, sewage sludge, bagasse, plant by-products, etc. Included. They may be used alone or together with each other and/or
Or it can be used with gas or oil.

The following example shows the effect of vermiculite on a furnace fired with sunflower seed husks.

Example Boiler is 18200Kg (40000lb) steam/
It had a time design capacity. It was a stocker that burned 80 tons of sunflower seed husks per day. It was equipped with a soot blower.

3.6 to 4.5 kg (8 kg) of unexpanded vermiculite per ton of shells
~10 lb) into the furnace at 1204 °C (2200 °C). The additive renders the deposit friable and easily removed by a soot blower,
This results in clean tube and boiler surfaces that require no further maintenance.

In contrast, in a comparative run without the addition of vermiculite, the deposits become hardened, sintered, and bonded, making them impossible to remove by ordinary soot blasts. Deposits accumulated throughout the boiler, particularly at the entrance to the convection passages. Fouling build-up occurred over time resulting in bridging between the tubes. The deposits had to be removed manually.

As used herein, the terms green, unexpanded and unexfoliated are intended to mean the same thing with respect to vermiculite.

Embodiments of the present invention are described in a prepared form.
(forn) using unexpanded vermiculite. However, it is baked (i.e. expanded or peeled)
You can also use vermiculite.

Claims (1)

[Claims] 1. A method for rendering flyash deposits more friable in furnaces fired with solid carbonaceous fuels other than coal, thereby facilitating their removal by steam or air probes, the method comprising: Vermiculite
A method consisting of injecting into the furnace at 1649-649°C (3000-1200〓). 2. Approximately 0.23 to 4.5 per ton of vermiculite as fuel
The method according to claim 1, wherein the injection is carried out at a rate of 0.5 to 10 lbs. 2. The method according to claim 1, wherein the vermiculite is 28 mesh to 200 mesh. 4. A method according to any of claims 1 to 3, wherein the temperature of the injection is about 1204°C (2200°C). 5. A patent claim in which the fuel is selected from the group consisting of lignite, peat, sunflower seed husk, wood, wood chips, paper, paper by-products, food waste, garbage-derived fuel, sewage sludge, bagasse, and platonic by-products. The method described in item 1. 6. The method of claim 5, wherein the fuel is sunflower seed husk. 7 Claim 1 in which the vermiculite is unexpanded
The method according to any one of Items 6 to 6. 8 Claim 1 in which the vermiculite is expanded
The method according to any one of Items 6 to 6.