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Wednesday, January 29, 2014

#169 - Most Common Connections to Nova Analyzers (electrical & tubing)

In terms of customer interaction with Nova continuous analyzers, there are surprisingly few requirements. Especially on auto-cal equipped units, the instrument essentially calibrates and runs itself.

During installation and set-up, there are a few connections for the customer to be aware of. We can roughly categorize them as Power, Signal, and Gas.

Power

The vast majority of our continuous analyzers are AC powered using 115VAC / 60Hz or 220VAC / 50Hz. This is dictated by the country / region the instrument will be installed into. AC power is brought into the analyzer cabinet and terminated at the main terminal block located on the upper right hand side.

In some cases, a separate power supply may be brought into the cabinet if the customer has required an internal cabinet LEL monitor that can depower the analyzer during an alarm condition. The separate power supply allows the LEL monitor to continue functioning when the rest of the analyzer is depowered.



Signal

The analyzer will have a visual display of the gas readings. The most common format of communicating the gas readings to other parts of the customer’s instrumentation system is via 4-20mA output. The gas analysis range is co-related to a 4-20mA scale. There will be a separate output for each gas analyzed. The outputs are usually connected to the customer’s PLC or data collection system. The main terminal block will have the output connections clearly labeled as shown in the diagram.

Digital outputs such as RS-485, RS-232, and USB are also available on some Nova analyzers. The connection points will be on the main terminal block next to the 4-20mA outputs. We can also offer MODBUS protocol over Ethernet connection using a small convertor usually located under the main terminal block.

Gas

Obviously, there will be tubing connections on the analyzer to allow flow of sample gas or calibration gas.

The SAMPLE IN port is used during normal operation when the instrument is continuously measuring the gas. The tubing is connected to this port directly from the process or from another sampling component located between the process and analyzer. The SPAN and ZERO ports are used during calibration. The DRAIN port is located on the bottom of some analyzers and is used to evacuate condensate from the analyzer.



The tubing attached to the SAMPLE IN and DRAIN ports will usually contain various amounts of condensed water which can freeze if the analyzer is installed outside in cold weather. These tubing lines require heat-tracing to prevent freezing. (Note: the tubing shown in the picture is just temporary flexible tubing used during the manufacturing stages. The tubing used in on-site permanent installation will be stainless steel, PFTE, or another specified material.)

For information on these and other gas analyzer systems, give Mike or Dave at Nova a call, or send us an e-mail.
1-800-295-3771
sales at nova-gas dot com
websales at nova-gas dot com
http://www.nova-gas.com/
https://twitter.com/NOVAGAS
http://www.linkedin.com/company/nova-analytical-systems-inc-
http://www.tenovagroup.com/

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Thursday, January 23, 2014

#168 - Nova Analyzers from the Field – Episode 4

We received this beauty into our service department recently. This is a continuous H2 / CO2 analyzer that has been connected to a heat treat furnace for about 14yrs now.




As can be seen, the unit is covered inside and out with black grime. The tubing has turned yellowish-brown. The jet black bowl filters at the bottom of the picture were actually transparent when they were new. It is a small miracle that the detectors were able to function for so many years in such harsh conditions.

Some of the black grime may be soot resulting from combustion of fuel in a low O2 environment. Some furnaces are operated this way intentionally to produce a certain atmosphere around the metal products that are being heat treated. However, most of the surfaces on / in this analyzer are also quite tacky / sticky.

Some types of metal heat treating, such as sintering, employ waxes and binders as part of the manufacturing process that later burn off in the heat treat furnace. These oil vapor products can later condense onto cooler surfaces and gradually accumulate there. That may be what is coating the various surfaces of this analyzer. This coating is probably also present on the optical surfaces in the detector assembly.

Infra-red detectors need to ‘see’ through a set of glass barriers and then through a volume of the sample gas. Some vapors deposit a colored film which will eventually become opaque like the black bowl filters mentioned above. If the detector can’t see through its window, it cannot make measurements.

Even non-optical detectors are sensitive to oil vapor contamination. We see this issue in the power industry on large generators. Electric generators are sealed with oil which can be vaporized over time and be pulled into a hydrogen purity analyzer. Oil-contaminated hydrogen detectors will not function properly. So we always provide an oil vapor filter assembly with the generator atmosphere analyzers. Maybe that would have been a good investment on this analyzer from the field.

I notice that this particular analyzer has a water-cooled condenser mounted on the left side of the cabinet (not visible in this picture). The purpose of this component is to help remove water from the sample gas. The condenser is basically a tube within a tube. Cold water is filtered and flowed into one end of the outer tube, and out at the other end. 

The cold water surrounds the inner tube and keeps it cool. On the inside of the inner tube, the cool tubing wall causes moisture in the sample gas to condense out. The condensed water runs down and is collected and drained in the condensate traps which mount on the bottom of the analyzer. The dried sample gas continues on into the analyzer. Of course, this whole concept only works if there is a continuous supply of cold water. In some regions, this cannot be guaranteed.

Another quirk of this analyzer is the fact that there is only a display for the H2 reading even though there is also a CO2 detector. In this application, the H2 reading was critical, but the CO2 reading was not. However, the presence of CO2 will interfere with accurate an accurate H2 reading. So we measure the CO2 and actively compensate the H2 reading. This keeps the H2 reading accurate even if the CO2 levels vary continuously.

It is hard to say what the future of this particular analyzer will be. I assumed that it was un-repairable. However, the owner wanted to try replacing the tubing and some of the other internal components. They probably also had to clean the optical surfaces in the detector as much as possible. How much longer the analyzer will stay functional, is anyone’s guess. But we are pleased to see that a Nova instrument has remained operational in adverse conditions for this long.

A new version of this equipment is still readily available. Check here in the heat treat section of our website.

Episode 1 - old portable flue gas with dual CO channel
Episode 2 - portable ppm H2 analyzer for university metallurgical lab
Episode 3 - ex-proof H2 analyzer in South Africa

If a system like this is of interest to you, contact Nova for details.

1-800-295-3771
sales at nova-gas dot com
websales at nova-gas dot com
http://www.nova-gas.com/
https://twitter.com/NOVAGAS
http://www.linkedin.com/company/nova-analytical-systems-inc-
http://www.tenovagroup.com/

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Thursday, January 16, 2014

#167 - Using the Energiron Process with SynGas for DRI Production

The following article appeared back in January 2007 in the technical section of Acero magazine. This concept combines two industrial processes that are of interest to us at Nova.
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Using the Energiron Process with SynGas for DRI Production

The standard Energiron process does not require major changes to operate with SynGas from a wide variety of sources.

The possibility of successfully coupling a DRI plant with a coal gasifier system will provide new perspectives in ironmaking. New possibilities are thus opened to introduce gas-based direct reduction technology in markets (like India, China or Europe) where there is low availability of natural gas at competitive prices, but high availability of coal.

In this respect, due to the specific characteristics of the process scheme, the technology offered by the Energiron alliance presents the most adequate configuration for this application, in terms of proven technology and investment/operating costs.

Increasing prices for energy, mainly for coke and natural gas, and environmental restrictions related to CO, emissions have led to new considerations for using available energies and materials. Additionally, continuing rising prices of metallics and prevailing market fluctuations make it necessary to analyze the alternatives for processing metalling units on site, for advantages in cost and availability. Energiron, the innovative Direct Reduction Technology, jointly developed by Tenova and Danieli, is offering an approach based on coal or other carbonaceous fuels as a source of reducing gas to a standard DR module for DRI production in locations lacking availability and/or low price of natural gas. By using synthesis gas (SynGas) from a gasifier as source of reducing agents, the amount, quality, and conditions of the gases required for the reduction process are the most important parameters defining the most adequate gasifier-DR scheme.

Alternative Energy Use - Coal Gasification

One of the main advantages of the Energiron process is the configuration based on independent reducing gas generation and reduction sections. Under these conditions the only requirement for the reduction process is the supply of the required amount of hydrogen and carbon monoxide: the process scheme remains unchanged. For the Energiron process there is a wide flexibility
for using alternative sources of reducing gases:
  • Hydrogen.
  • Conventional reformed gas.
  • Gases from coal gasification processes.
  • Coke oven gas.
  • Gases from hydrocarbon gasification.
  • Gases from smelter gasifiers.
  • Others.

In case the reducing gas (SynGas) comes from a coal gasifier, it is possible to adjust its characteristics by conditioning it to enhance its H2 content.

Figure 1
DRI plant with gasifier: general arrangement


Coal Gasification: General background

Gasification refers to the partial oxidation of a fossil fuel, forming SynGas, which consists primarily of hydrogen (H2) and carbon monoxide (CO). The Energiron process is characterized by the use of H2-enriched gas. Most gasifiers produce SynGas with suitable analysis for use in the DR process. Gasification or partial oxidation consists of converting low-grade fuel that is often dirty. (such as coal, refinery residues and biomass). The partial oxidation reaction for carbon is:

C + 1/2 O2 = CO

This reaction is exothermic and thus, water is introduced into the gasifier in the form of steam or liquid water to moderate the temperature of the reaction by the endothermic reaction:

C + H2O = H2 + CO

Other reactions that occur within a gasifier are the shift reaction:

CO + H2O = H2 + CO2

and the hydro-gasification reaction:

C + 2H2 = CH4

For any DR process, carbon from the reducing gases make-up (either in the form of CO or CH4) must be eliminated from the DR plant. Typically, for other DR process, this carbon is purged from the system via tail gas, which is used as fuel in reforming/heating equipment. In the Energiron process, due to selective carbon elimination through CO, removal, the purge is minimized and recycling/reuse of reductants is maximized, thus optimizing reducing make-up requirements.

Energiron - Gasifier Scheme

As presented in Figure 2, the treated, H2-enriched SynGas from the gasifier is fed to the standard Energiron DR plant. The mixture of SynGas make-up and recycle gas is preheated in a direct gas heater up to 930°C and fed to the reactor. After reduction of iron ores in the DR reactor, top exhaust gas is passed through a scrubbing unit for dust removal and cooling. Then, the gas is recycled by the compressor and CO2 is selectively removed. To further decrease energy consumption, a top gas heat recuperator can be incorporated. Specific requirements of SynGas per tonne of DRI basically correspond to the typical makeup of the conventional Energiron gas scheme (about 685 Nm3/t DRI).

Figure 2
Energiron plant with syngas from gasifier, including HYTEMP system


In case a steel mill is present downstream, pneumatic transport of hot DRI (HYTEMP) to the Electric Arc Furnace can be incorporated as part of the basic plant arrangement. By comparing the scheme based on SynGas with the conventional Energiron DR scheme, the similarity of reducing gases entering the DR reactor can be noted; hence, no technological risk is foreseen for this application. Based on the analysis of treated SynGas (typically from a conventional gasifier), expected DRI characteristics for coal-SynGas are 93% metallization and up to 2% carbon.

Depending on particular applications, optional schemes, which can be incorporated, are: 
  • In plant electrical generation. This can be achieved by installing a turbo expander in the treated SynGas stream before it is fed to the DR module. This allows potential power savings of about 20-40 kWh/tonne of DRI (depending on gasifier technology), taking advantage of the gasifier high operating pressure. 
  • Carbon dioxide (CO2) recovery. For sale as by-product.

Most Suitable DR Technology for using SynGas from coal gasification

When comparing the basic Energiron Process scheme to the one required for SynGas from coal gasification, the following main aspects related to the Energiron Process application can be easily noticed: 
  • General process scheme. No major changes and innovations are required in the basic process scheme. The reduction section is incorporated as it is in typical Energiron plants. 
  • H2-rich gases use in DR plants. SynGas is conditioned through shifting and CO2 removal to produce the H2-rich gases, which characterize the Energiron process. 
  • Optimization of process SynGas consumption. Recycling of reducing gases through CO2 removal, minimizes SynGas make-up. 
  • HYTEMP iron use.

Potential incorporation of the HYTEMP system for delivering hot DRI to the EAF leads to important economic benefits related to power savings and productivity increase. The HYTEMP iron presents a unique option as an alternative product for integrated steelmaking facilities, based on the use of SynGas from coal gasifiers.

Overall plant performance

As compared to other existing and emerging coal-based DR technologies, this scheme offers the possibility of installing a DR plant of any size up to 1.7 million tonnes/year of DRI in a single module. This approach is based on the incorporation of proven technologies: Gasifier unit and Energiron DR plant.

A similar scheme, based on coal gasification, is being implemented by Danieli in India for a Jindal project to produce 1.7 million tons of DRI.

Conclusions

The possibility of successfully coupling a DRI plant with a coal gasifier system will provide new perspectives in iron making.

New possibilities are thus opened to introduce gas-based direct reduction technology in markets (like India, China or Europe) where there is low availability of natural gas at competitive price, but high availability of coal.

In this respect, due to the specific characteristics of the process scheme, the technology offered by the Energiron alliance presents the most adequate configuration for this application, in terms of proven technology and investment/operating costs.

Original article can be found on the Tenova website here.

Other links to HYL and Energiron:
http://www.tenovagroup.com/companies_hyl.php?id_company=2
http://www.energiron.com/

HYTEMP® is registered trademark of Tenova HYL

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Monday, January 6, 2014

#166 - PPM O2 – Part 2

We talked a little last time about oxygen analysis at the parts-per-million (ppm) level. Electrochemical sensors perform well in many applications at those levels.

Leaks and diffusion create challenges with ppm O2 applications. In a neutral pressure environment, the gas analyzer will require a built-in pump. Activation of the pump will create a slightly lower pressure in the sample tubing ahead of the pump and will promote inbound leaks at imperfect tubing connections.

Gas diffusion may also occur irrespective of pressure through polymer-type tubing based on the size of the gas molecule and the structure of the polymer. Flexible polymer tubing may initially show decent diffusion resistance. However, other constituents in the sample may alter the chemistry and structure of the tubing material and make it more prone to gas diffusion over time.

In many gas analysis applications small leaks and gas diffusion may not cause significant analytical problems. But with ppmO2 applications, these problems can have a noticeable effect. Even a small inbound leak of ambient air will introduce a high level of non-sample O2 and result in falsely high readings. It may also prevent an accurate Zero calibration. O2 diffusion may cause the same effects as inbound leaks, but at a slower rate.

The most effective solutions to these issues involve removing leaks and points of diffusion. PPM O2 analyzers should be meticulously built using stainless steel tubing with reliable connections. We prefer that ppmO2 applications have a positive sample pressure. This removes low pressure points before the sensor and allows us to use a regulator in place of a pump. Simple and strong seem to be the best methods for ppmO2.


We are currently building a couple instruments with dual-channel
PPM / % O2 analysis. The ppm channel can be switched to protect
the sensor automatically or manually depending on the customer’s
preference. In this photo, the instrument is being purged with N2
in advance of factory calibration.

The ppm side is being purged out with N2
in preparation for factory calibration.
Notice that the tubing is narrow diameter
flexible stainless steel to minimize leaks
or diffusion during this process.

In most applications, a ppm analysis requirement implies a high proportion of other gases in the sample. Some gases interfere with accurate ppm analysis of other gases. So it is important that we have a good understanding of the sample gas make-up before designing an analyzer.

We have produced portable and a continuous PPM O2 analyzers which may be suitable for your application.

1-800-295-3771
sales at nova-gas dot com
websales at nova-gas dot com
http://www.nova-gas.com/