脱硫塔外文翻译

Research

and

Development

of

Baosteel

Swirl-JetSintering

Flue Gas Desulphurization Technology

SHEN Xiao-lin, LIU Dao- qing, ZHOU Jing

(Environment and Resources Institute, R&D Center, Baoshan Iron and Steel Co., Ltd., Shanghai

201900, China)

Abstract

: The research background and technical features of BSFGD (Swirl-Jet-Absorbing Wet

Limestone-gypsum Sintering FGD Technology) process and equipments were introduced here in

detail. The main contents, achievements of

pilot

experiments,

and

engineering

practices

of

BSFGD

were

analyzed

and

discussed

systematically. Past engineering

practice

experiences

indicate

the

fact

is

that

the

technology

has

the

following

merits,

wide

applicability to sintering flue gas

features

such

as

temperature

changing

frequently,

SO

2

concentration

being

unstable,

flow

rate

fluctuating

intensively;

high

pollutants

removal

efficiency;

low

investment

and

energy

consumption; stable and reliable running; utilizable byproduct

(gypsum) etc. It has been proved

that BSFGD has the value of a wide range of applications for large and medium-sized

sintering

machines flue gas desulphurization in the steel industry.

Key words

: sintering flue gas; desulphurization technology; research; engineering practice

1 Introduction

At the beginning of the century, while

to science and technology development

in

Iron and Steel Industry until 2020> was constituted, the experts

of metallurgy point out that “Due

to the complicacy of agglomerate and the otherness of sintering process, the technology of flue gas

desulphurization

used

in

power

plants

could

not be

applied

in

sintering

flue

gas

desulfurization

directly and blindly. The investment and running cost of FGD technology used in Iron and Steel

Industry

of

other

developed

countries

are

usually

too

expensive

to

be

accepted

by

Chinese

companies.”

Therefore, the technology of sintering flue gas desulfurization in china was listed as

important

study

topic

in

Guide

to

science

and

technology

development

in

Iron

and

Steel

Industry

until

2020>.

Since

there

are

few

researches

and

technologies

existing

in

this

area,

it?s

significant to invent a technology with the properties of efficient, highly adaptive, cost-effective,

safe and reliable in operation for Chinese Iron and Steel companies. In china, Baosteel takes the

lead in sintering FGD technology research and development at beginning of the year 2005.

2

The

Features

of

Baosteel

Sintering

Flue

Gas

Desulfurization

Technology

According

to

the

production

characters

of

large-scale

sintering

machine,

considering

the

application

of

desulfurizer

and

desulfurizing

product

and

the

actual

condition

of

company,

we

contrast

and

analyze

the

technology

of

FGD

used

in

market

widely

and

deeply.

Choosing

wet

limestone-gypsum sintering flue gas desulfurization as the base of technical route and then starting

to research and develop through industrial tests point at the sintering flue gas feature, and finally,

and

formed

serial

technology

and

equipment

of

Baosteel

Swirl-Jet-Absorbing

Wet

Limestone-gypsum Sintering FGD with own intellectual property rights (Referred to as Baosteel

Sintering flue gas desulfurization technology, and abbreviated as BSFGD).

2.1 Introduction of process flow

Flue gas flow from main suction fans of sinter machines be pressurized by booster fan, then

be cooled and pretreated in cooling equipment, and then perform the desulfurization reaction in

Swirl-Jet Absorber, the purified flue gas discharge from chimney on standard after demisting. The

auxiliary

systems

such

as

limestone

slurry

preparation

and

gypsum

dehydrationsystem

are

the

same

as

normal

wet

FGD

system,

which

are

mature

techniques.

The

process

flow

diagram

of

BSFGD is shown in Fig.1.

2.2 Technical features

2.2.1

Baosteel swirl-jet- absorbing wet limestone-gypsum sintering FGD technology

Use limestone powders (250 meshes) as desulfurizing agent, Ca/S is equal to 1.01 to 1.03,

and

the

cost

of

desulfurizer

is

low.

The

FGD

system

run

steadily

and

safely,

over

95%

synchronous operation rate with sintering machine. The desulphurization efficiency is greater than

90%, the exhaust concentration of SO

2

and dust is less than 100 and 50mg/m

separately, and

the removal efficiency of SO

3

, HCl and HF will be greater than or equal to 50%, 80% and 90%

separately. The gypsum is good enough to meet the requirements of using as resources, in which

the content of CaSO

4

·

2H

2

O is over 90%, the content of moisture is below 10%, the pH value is

6-8. It shows excellent economics that the investment and operation cost is 70%- 80% to the cost

of other sintering flue gas desulfurization technology.

2.2.2 Cooling device for pretreatment

A

cooling

device

as

pretreatment

was

set

before

the

absorbing

tower

to

overcome

the

3

difficulty

to

cool

down

the

flue

gas

whose

temperature

fluctuated

seriously

and

frequently,

maintain

the

safety

of

absorbing

tower

and

provide

the

best

temperature

for

desulphurization

reaction.

This

component

was

helpful

to

protect

the

gas- gas

heater

(GGH)

from

blocking

in

traditional FGD technology and to promote the cooling efficiency of flue heavy metals,

alkali

metals

and

a

part

of

dust

in

flue

gas

were

removed

by

the

device,

which

was

useful

to

restrain the blocking problem and scale formation in the absorbing tower and improve the quality

of gypsum. Furthermore, most HF and HCl in flue gas were removed by the device, which can

prevent eroding for the material of absorbing tower and other subsequent devices.

2.2.3 Swirl-jet-absorbing tower

The reaction container was designed to be the swirl-jet absorber on the basis of aerodynamics

knowledge. The limestone slurry in the absorber performed as continuous phase, the flue gas was

erupted from Swirl-Jet device and separated into fine bubbles in the absorber, as dispersion phase.

Then the gas and the limestone slurry reacted thoroughly with high mass transfer efficiency. This

process

can

keep

the

system

stable

when

violent

fluctuation

of

flue

gas

flow

rate

and

SO

2

concentration,

with

high

desulphurization

and

dedusting

efficiency.

In

this

process,

the

absorbing reaction can be completed in

one cycle, so that the limestone slurry don?t need to be

repeatedly cycled, which can lower the energy consumption, Furthermore, the products of gypsum

were well-crystallized, larger particle size, and utilizable.

2.2.4 Integrated demister

The expansive space in the top of the absorber, which is empty, combined with the external

demister to compose integrated demister, which is good for eliminating the moisture in the flue

gas.

3 Technical Developments in Pilot Experiment and Engineering Practice

3.1 Device for pilot experiments

The

pilot

experiments

system

with

capacity

of

90000

m

/h

flue

gas

is

composed

of

six

subsystems

as

following:

SO

2

absorbing

system,

limestone

slurry

preparation

system,

flue

gas

system, gypsum dehydration system, process water system and DCS control system. Fig.2.

3.2 Research content in pilot experiment and engineering practice

(1)

Through experimental study on every influencing factors of desulphurization efficiency,

found out the main factors and essentials to ensure FGD system running continually and steadily

in

the

long

term,

made

the

debugging-programs

of

large-scale

FGD

project,

and

developed

complete set of rules, specification requirements, and standards for BSFGD, etc.

3

(2) By experimental investigation on a variety of swirl-jet devices and cooling pre-treating

methods, we have obtained the best configuration and design parameters of processing parameters

and key equipments, and established the thermodynamic and dynamic calculation models of FGD

system.

(3) Through long-term experiment at pilot plant, search and discover laws and solutions to

various problems that may occur in sintering flue gas desulfurization process, such as clogging,

deposition, etc. Develop control programs of large-scale FGD project, such as the key parameters,

instrument configuration.

(4) In response to the technical requirements that the surface of slurry tank must be steady,

carry out experiments on side-entry slurry agitation and oxidation air distribution, set up relevant

models,

find

out

various

kinds

of

control

parameter

laws,

develop

complete

set

technology

of

slurry agitation and forced oxidation.

(5)

Carry

out

antiseptics

experiments

of

over

100

test

pieces

at

every

representative

site,

provide the basis for antiseptics selection, develop several special-purpose antiseptic scaly clays

suitable to sintering FGD, and a complete set of antiseptic program of sintering FGD project.

(6)

Develop

such

series

sets

of

manufacturing,

processing

and

installing

technology

of

sintering flue gas desulfurization system, and provide technical guidance.

(7)

Experimental

study

on

Emergency

Preparedness

for

emergency

situations,

develop

relevant emergency preplans technical regulation.

(8) Research on the utilization of Sintering FGD gypsum, such as adding to steel slag powder

or slag powder to substitute for cement directly, and achieved significant results.

(9)

Research

and

analyze

the

characteristics

of

sintering

FGD

waste

water,

develop

wastewater

treatment

and

reuse

technology,

propose

wastewater

treatment

technology

and

program.

(10) Feasibility study program, preliminary design, and design schemes have been made for

three

typical

large-type

sintering

FGD

projects

in

the

whole

metallurgical

industry,

which

have

with different flue gas flow rates and different characteristics.

4 Engineering Applications

By experts' evaluation, Baosteel decided to put the results of BSFGD research into practical

application.

Based

on

unified

plan,

the

BSFG

R&D

Team

of

Baosteel

Research

Institute

was

responsible

for

the

completion

of

technical

assembly,

and

supported

comprehensive

technical

guidance

and

support

for

layout

of

plant,

configuration

and

manufacture

of

equipments,

heart

system construction, debugging, and operating, etc.

4.1 Scale of projects

Overview of three set of sintering FGD units is shown in Table 1.

4.2 Engineering operation

After putting into operation, this three sintering desulphurization units running steadily, every

technical economical indicators can meet the design requirements, Synchronous operation rate can

reach more than 95%.

4.3 Pollutant removal efficiency

Under

the

situation

of

flow

rate

fluctuating

intensively,

temperature

changing

frequently,

SO

2

concentration

being

unstable,

the

economical

desulphurization

efficiency

should

be

90%,

and

the

FGD

can

run

steadily

with

over

95%

desulfurization

efficiency.

The

dust

collection

efficiency is over 85%, and the removal efficiency of SO

3

, HCl and HF will be greater than or

equal to 50%, 80% and 90% separately.

The condensed fluid pH value of ?white fog? e

xit from

chimney is about 6.0 to 6.5.

Waste water about 3 to 5 t/h can be sent to in-plant wastewater treatment system, and then

return

to

sintering

process

utilization.

The

byproduct

is

gypsum,

in

which

the

content

of

CaSO

4

·

2H

2

O

is

over

90%,

with

high

degree

of

crystallization

and

low

impurity

content,

its

quality is superior to conventional power plants FGD gypsum and natural wet FGD gypsum, and it

can fully satisfy the requirements of China's building materials.

4.4 Benefit analysis

(1) In case of dealing with equal exhaust gas flow, compare and analyze with other wet FGD

and

CFB

semi-dry

FGD

technology,

the

One-time

investment

and

running

costs

of

Baosteel

Sintering FGD is about 70% to 80% of the other FGD technology.

(2)

Mei

Steel

Branch

No.3

Sintering

FGD

Project

has

been

the

demonstration

projects

of

environmental

protection

in

Nanjing

district

and

Jiangsu

Province.

The

Stainless

Steel

Branch

No.1 Sintering FGD Project and Baosteel Branch No.3 Sintering FGD Project can complete the

SO2 emission reduction task, and create environmental condition for sustainable development of

enterprises.

(3)

According

to

the

actual

sulfur

content,

this

three

sintering

desulphurization

units

can

reduce

about

15000

to

20000

ton

of

SO

2

emission,

and

save

industrial

discharge

taxes

about

20000

thousand

RMB

annually.

Little

wastewater

and

byproduct

gypsum

can

be

utilized

comprehensively, so BSFGD is an energy- saving and emission-reduction technology, it can reach

an agreement to Cyclic Economy.

(4) Develop and innovate independently, the technology developed by Baosteel will be the

effective solutions to sintering flue gas desulfurization, which is the difficult problem of the whole

metallurgical industry.

5 Brief Summary

The

Baosteel

sintering

FGD

technology

was

developed

for

the

complex

characteristics

of

sintering

flue

gas,

which

has

the

following

merits,

including

high

efficiency,

stable

running,

simple process, cheap absorbent, utilizable byproduct, and advanced techno-economic indicators,

etc, so, the BSFGD technology has extensive use value to the flue gas desulfurization of large and

medium- sized sintering machine.