The usage of fly ash from flue gas desulfurization to make compositions for building

Abstract

Composition for building materials comprises of fly ash from flue gas desulfurization. The fly ash (βCaSO4 anhydrite), obtained from circulating fluidized bed flue gas desulfurization, is mixed with binder reactants at a ratio of 9:1. It's mainly used for non-structural cement mortar, bricks for paving walkways, brick wall decors, fire-resistant walls for interior partitions, plasterboards and so on. The binder reactants compose of 70% CaSO4.½H2O, 10% Na2SO4, 10% CaO, 5% NaOH, 0˜5% cement and 0˜5% starch. When the binder reactants are mixed with fly ash and water (30% to 40% of the above total weight), the hydration process of CaSO4 anhydrite is accelerated.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Taiwan Invention Patent Application No. TW 105124724 filed Aug. 4, 2016, which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

(1) Field of Invention

This invention relates to a reuse of abandoned fly ash, specifically focusing on fly ash from flue gas desulfurization to make compositions for building materials.

(2) Description of Related Art

Formosa Plastics Corporation (FPC) Sixth Naphtha Cracker Complex uses Circulating Fluidized Bed (CFB) Boiler from ALSTOM. Petroleum coke and limestone are mixed with a ratio of 2:1 and sent inside the boiler, undergoing high temperature oxidative combustion to generate steam and drive turbines. Hundreds of tons of by-product fly ash, composed of pulverized 3 CaSO₄ anhydrite, granular β CaSO₄ anhydrite and hydrated CaSO₄, are produced daily and have not been effectively dealt with. Since the fly ash is produced at temperatures above 850° C.˜900° C., it contains primarily the form β CaSO₄ anhydrite and doesn't easily undergo hydration with water under standard atmospheric pressure and temperature. As this property influences the usability of fly ash, the inventors continues to research and develop products that meet environmentally friendly standards.

CaSO₄ anhydrite+H₂O→Does not easily undergo hydration under standard atmospheric temperature and pressure.

BRIEF SUMMARY OF THE INVENTION

The goal of this invention is to use fly ash from flue gas desulfurization, along with binder reactants and known quantity of water, to make compositions for building materials that have a comparable strength to that cement.

To accomplish this goal, this invention involves mixing fly ash (13 CaSO₄ anhydrite), obtained from circulating fluidized bed flue gas desulfurization with binder reactants at a ratio of 9:1. It's mainly used for non-structural cement mortar, bricks for paving walkways, brick wall decors, fire-resistant walls for interior partitions, plasterboards and so on. The binder reactants compose of 70% CaSO₄.½H₂O, 10% Na₂SO₄, 10% CaO, 5% NaOH, 0˜5% cement and 0˜5% starch. When the binder reactants are mixed with fly ash and water (30% to 40% of the above total weight), the hydration process of CaSO₄ anhydrite is accelerated.

DETAILED DESCRIPTION OF THE INVENTION

[Simple Illustration]

To help the review committee better understand the technology, means and effects by which set goals are accomplished, the following case is shown in sequence and illustrated in details to provide deeper perception of the goals, features and advantages of this invention.

[The Way of Implement]

This invention involves mixing fly ash (β CaSO₄ anhydrite), obtained from circulating fluidized bed flue gas desulfurization, with binder reactants at a ratio of 9:1. It's mainly used for non-structural cement mortar, bricks for paving walkways, brick wall decors, fire-resistant walls for interior partitions, plasterboards and so on. The binder reactants compose of 70% CaSO₄.½H₂O, 10% Na₂SO₄, 10% CaO, 5% NaOH, 0˜5% cement and 0˜5% starch. When the binder reactants are mixed with fly ash and water (30% to 40% of the above total weight), the hydration process of CaSO₄ anhydrite is accelerated.

The products are showed in the following:

Category	Raw Material	Strength (SGS)
Non-structural Cement	CaSO4 anhydrite 43%	2500~3000 Lb/in2
Mortar	granular CaSO4 57%
Bricks for Walkways	CaSO4 anhydrite 43%	2500~3000 Lb/in2
	granular CaSO4 57%
Wall decor and plasterboard	CaSO4 anhydrite 100%	1500~1700 Lb/in2
Fire-resistant walls for	CaSO4 anhydrite 43%	1000 Lb/in2
interior partitions and	Hydrated CaSO4 57%
plasterboards

The above products satisfy the demands and standards of normal building materials. Only 10% binder reactant by weight of the above by-products is needed to produce building materials that meet standard construction strength requirement.

From the above procedures, it can be seen that the binder reactant of this invention can accelerate the hydration reaction of the fly ash, which provides a great variety of applications, in contrast to prior art.

The invention has been described in detail with particular reference to certain preferred embodiments thereof and it is intended that the specification and examples be exemplary only. It should be appreciated that variations and modifications can be effected within the spirit and scope of the invention.

Claims

1. The binder reactant for reusing a calcium sulfate compound comprising: approximate 70% CaSO4.½H2O, approximate 10% Na2SO4, approximate 10% CaO, approximate 5% NaOH, approximate 0˜5% cement, and approximate 0˜5% starch.

2. The binder reactant of claim 1, wherein the calcium sulfate compound is a fly ash, β CaSO4 anhydrite, essentially obtained from circulating fluidized bed flue gas desulfurization.

3. The method of making a building material: (a) mixing the binder reactant of claim 1 with the fly ash of claim 2 substantially at a ratio of 1:9 to form a pre-hydration material; and (b) mixing the pre-hydration material with water at a weight ratio of about 30% to 40%, whereby a hydration process of β CaSO4 anhydrite is accelerated.

4. The method of making a building material of claim 3, wherein the building material can be used for non-structural cement mortar, bricks for paving walkways, brick wall decors, fire-resistant walls for interior partitions, or plasterboards.

5. The process of making an alternative building material: mixing the binder reactant of claim 1 with hydrated CaSO4 at a ratio about 75% w/w.

6. The process of making an alternative building material of claim 5, wherein the alternative building material can be used for non-structural cement mortar, bricks for paving walkways, brick wall decors, fire-resistant walls for interior partitions, or plasterboards.