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Hydraulic retrofit meets increased demand

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Productivity targets are a key performance measure in any process industry and the refining business is no exception. Increasing output from a large refinery to meet market demand does present its challenges, however, dealing with the pumps does not need to be one of them. Sulzer has proved that a retrofit can provide the most cost-efficient solution, when carried out by a provider with the right design experience and manufacturing expertise.

Matt Kinney, Hydraulic Retrofit Specialist, at Sulzer, discusses a good example of a successful retrofit project.

Due to changes in Government regulations over the past several years, the demand for ultra-low sulfur diesel (ULSD) has increased significantly. As a result, refineries across the country have been forced to adapt and find innovative solutions to meet increasing capacity. A refinery located in Texas found themselves in this situation and reached out to Sulzer’s Odessa Service Center to investigate possible solutions.   In a focused effort to address this issue, the two pumps of interest are 6x8x10.5 BB5 10 stage units in diesel charge service. The American Petroleum Institute (API) BB5 is a barrel pump that encloses a multi-stage axial split inner bundle with an opposed impeller configuration (see figure 1). Being that the pressure boundary is radially split, these pumps are typically designed for high-temperature and/or high-pressure applications. With the capability of handling pressures and temperatures up to 6’250 psi (431 bar) and 800 °F (427 °C) respectively, the API BB5 is an excellent pump selection for applications such as water injection, oil export, boiler feed, and charge service.

Challenge

The subject pumps were originally sold in 2006 at a rated point of 1’110 gpm (252 m3/hr) @ 4’014 ft (1’223 m). However, with the change in ULSD demand the reliability engineers at the refinery were interested in a capacity increase to 1’628 gpm (370 m3/hr) @ 3’450 ft (1’052 m) (see figure 2). The goal for Sulzer was to find the most economical and timely solution to meet the customer’s needs.

Design review

When in this situation, there are three possible options:

Purchase a new pump that is designed to deliver the desired capacity Hydraulically modify or “re-rate” the existing pumps Operate their two existing 100% pumps in parallel (depending on customer system curve) Each of these options above have their own advantages and disadvantages. For example, parallel operation would clearly be the least costly to achieve the increase in flow. However, the lack of system redundancy in the event of a failure is risky and can often be very costly in terms of lost production. A new pump selection to fit the application could be advantageous with regards to efficiency but long lead times, the cost to reroute pipework, and baseplate/foundation modifications may make this option less attractive. There is really no downside to re-rating pumps other than the fact that the desired performance may not always be achievable in the given frame size, if feasible, re-rating is often faster and more economical.

Based on the criticality of this service for the overall success of the refinery, the possibility of re-rating was of great interest in this example. To support the customer, Sulzer engineers conducted a thorough feasibility study both hydraulically and mechanically to determine whether the goal was possible. A specific speed (Ns) based search through Sulzer’s vast hydraulic database revealed an existing proven design that would meet the client’s needs – provided the impellers were able to physically fit, and the inner-case volute nozzle areas were able to be increased enough to allow the impeller to meet as-designed performance. A review of the volute development drawings provided confidence that both items could be fulfilled.

The Sulzer approach was to keep it simple:

Select an existing standard Sulzer impeller hydraulic design that is suitable for the desired performance and has been proven by at least two factory tests.  Ensure that case modifications can be made to fit the new impeller. Confirm the nozzle area can be increased enough to mimic the reference pump performance.  

Optimized solution

With a massive array of impeller hydraulic designs available, Sulzer engineers were able to select an existing design that would meet the new desired head and capacity of the application.

A mechanical cutback was done (see figure 3) to achieve both an increase in nozzle area and lip diameter. Based on empirical data, the increase in nozzle area would allow the new impeller selection to runout to the new design point. The increase in volute lip diameter enabled the designers to achieve sufficient lip clearance. This, and the fact that the cutback was ‘angled’, helped with the reduction of vane pass pulsations and overall vibration amplitudes.

The outlet vanes of the impeller were underfiled to increase the outlet area between vanes (OABV) and help flatten the performance curve. This also pushed the best efficiency point (BEP) to achieve higher flows.

The design process highlighted the fact that the new performance level did not require all 10 stages. One stage was removed so that the impeller trim could be near-full diameter. This benefitted both the efficiency and the BEP location for the pump. With the stage reduction, the effect on axial thrust direction and magnitude was analyzed; the internal bushings were resized to ensure the axial load was acceptable for the thrust bearing.

Challenges and drawbacks

With a major re-rate such as this, it can be rather difficult to fit a new, relatively large, high capacity impeller within the existing volute. This is because multi-stage pumps such as this are designed with the shortest possible stage spacing to limit overall pump length. Fortunately, the pumps in this example were originally equipped with a relatively low flow rotor compared to its frame size, which offered more room to work. In order to accommodate the increased impeller outlet width, the volute side walls required widening or “slabbing” to ensure adequate side-room clearance, which is extremely important to centrifugal pumps.

In addition, the inner-case line bore diameter was increased to accommodate the larger impeller eye diameter. The bore was increased to the maximum allowable value while maintaining enough wall thickness between it and the waterways and maintaining structural integrity of the inner bundle.

The increased pump performance required more power than the original 1’250 hp (932 kW) motor could deliver, so a new motor was required to meet this demand. However, no baseplate modifications were required as the frame size for the higher rated motor remained the same.

The Net Positive Suction Head Required (NPSHR) had increased with the new selected suction impeller. However, this was not a problem as the Net Positive Suction Head Available (NPSHA) was adequate.

I manage the editorial affairs for MONETA Tanıtım, which produces specific publishing, specially for the sphere, Turkey industry. We work for content development through digital and print media, with a new generation, dynamic publishing intellection.

Pumps

Chemical manufacturing made pure and simple

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Sulzer’s expertise in crystallization enhances product quality and manufacturing performance. Process simplification is key to manufacturers staying ahead in a highly competitive market, as it allows them to deliver products of higher quality at lower costs. When a premier Chinese producer of food additives, Wuhan Youji Industries, wanted to review one of its purification processes, Sulzer offered an ideal solution. Advanced fractional crystallization technologies allowed the manufacturer to reach quality levels that were unattainable with its existing equipment while at the same time improving efficiency.

With production capacities of 200’000 tonnes  per annum [approx. 220’400 tons per annum] benzoic acid, including 60’000 tonnes per annum [approx. 66’100 tons per annum] of high purity benzoic acid  and 50’000 tonnes per annum [approx. 55’100 tons per annum] benzyl alcohol, Wuhan Youji is a global leader in antisepsis, preservation and antioxidation as well as an award-winning pioneer in China’s food additive industry. The company is particularly active in the production and standardization of benzoic acid and benzoates, which are widely used as preservatives. Safety, eco-friendliness and health are key aspects that Wuhan Youji promotes in its own operations and good manufacturing practice guidelines. This commitment drives the company to regularly simplify and enhance its processes.

Recently, the company decided to improve one of its most challenging processes: the purification of benzyl benzoate. Used in flavor and fragrance industries, the chemical needs to have extremely low levels of impurities and appear colorless, i.e. any remaining foreign matter should not affect the benzyl benzoate’s appearance. Therefore, separation processes that rely on crystallization are a must, in order to achieve such a highly concentrated substance.

Wuhan Youji’s existing purification method was based on suspension crystallization. It involved several complex stages as well as a number of pieces of equipment, such as crystallizers, centrifuges and waste disposal systems. In addition, the procedure required constant human intervention and manual operations.

Repeating previous success

To succeed in this ambitious task, Wuhan Youji contacted Sulzer, the leader in separation and mixing technology. The two businesses had developed a good working relationship based on previous projects – Sulzer delivered two high-performance and efficient separation systems for the purification of benzoic acid. Based on the success of these projects, the chemical manufacturer was keen on getting an innovative solution for the purification of benzyl benzoate.

“By using our proprietary, fully-automated falling film crystallizers, Wuhan Youji was able to produce benzoic acid of the highest quality and purity, greatly increasing the business’ competitiveness in China,” explains Matthias Schäfer, Project Manager at Sulzer.

Sulzer’s specialists started looking at how to simplify the purification process for benzyl benzoate by conducting extensive small-scale and pilot plant testing to identify the most suitable and efficient way to remove impurities from the chemical. The in-depth investigation by Sulzer revealed a way to purify benzyl benzoate using a finely tuned static layer crystallization process.

The method would streamline and simplify the process, as it requires only one, fully automated piece of equipment with no moving parts, and doesn’t need solvents nor does it generate waste streams. Furthermore, the technique could handle the high viscosity of benzyl benzoate.

In addition, the analyses were fundamental to estimating the number of stages required to reach a high level of purity as well as construct an ideal temperature profile. In effect, the temperature-sensitivity of the chemical required a highly accurate temperature profile to regulate the crystallization and melting phases, which are separated by narrow temperature intervals. The knowledge and expertise of Sulzer’s engineers, the in-depth testing and the high-quality separation equipment contributed to successfully overcoming these issues.

Well-planned crystallization

Based on the process developed by Sulzer, the feed in the static crystallizer undergoes stages of cooling and heating to separate benzyl benzoate from the impurities. When the temperature within the crystallizers are below the freezing point of the melt (between 14 and 4°C), benzyl benzoate crystals build up on the outer surface of the plates. Impurities are largely rejected from the growing crystals and are concentrated in the remaining melt.

Once all the benzyl benzoate fraction has been crystallized, the liquid phase is drained from the crystallizer, while the purified crystalline layer remains attached to the plates. This is then further purified by sweating (or partial melting), which is a gentle reheating up to the melting point (18°C). The resulting impurity-rich melt is drained off. After sweating, the purified benzyl benzoate crystal layer is totally melted and collected in product storage vessels.

Having two crystallization stages allows the manufacturer to reach a product purity of at least 99.9% w/w, a quality level that is far higher than what the existing suspension crystallization unit could achieve. An additional stripping stage helps to eliminate remaining impurities with boiling temperatures close to benzyl benzoate.

Scaling up to full industrial plant

Based on the successfully developed design, Sulzer proceeded to manufacture, install and start-up the full-scale unit. In order to allow Wuhan Youji to benefit from this new system as soon as possible, the entire project was completed in a record time of 12 months, and the chemical plant can now accommodate a benzyl benzoate product capacity of 5’500 tonnes [approx. 6’000 tons] per year.

Sun Bo, Technical Director at Wuhan Youji, comments: “We are extremely happy with the solution delivered by Sulzer. Not only were they able to greatly simplify our existing process, improving efficiency and resource use, but they also helped us to enhance the quality of our product. Sulzer has been a very reliable partner and we look forward to collaborating again in a near future.”

Matthias Schäfer concludes: “We are particularly delighted with the outcome of this project. Our research and development capabilities helped us create a tailored and highly efficient solution. Customer satisfaction and the continued cooperation with Wuhan Youji clearly attest to our capabilities in separation technology and our commitment to develop complete, customized solutions.”

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Pumps

Digital Displacement pump technology

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Most hydraulic machines today have the same basic control mechanism that was first patented in 1893. The variable-angle swash plate pump has been a reliable way to transmit fluid power for over 120 years. Efforts have been made to digitize the mechanism with feedback and electronic control, but the underlying principle has limited benefits.

Our Digital Displacement® pump technology is a natively digital hydraulic innovation. It utilizes a radial piston machine which enables and disables cylinders in real time, using ultra-fast mechatronic valves.

The intelligent, digital controls mean a digitally-enabled machine is highly controllable and extremely efficient. The net result is:

  • Dramatically lower energy losses (typically less than a third of swash-plate machines)
  • Dramatically faster response (typically ten times faster)
  • Reduction of annoying, high-frequency noise

Individual cylinders are only called into action when required to meet the load demanded, resulting in a pump with efficiency over 90 percent. The control of individual cylinders allows a single pump to have multiple independently-controllable services providing system innovators a platform to invent new architectures to unlock the capabilities of digital hydraulics.

By replacing a mechanical or hydraulic device with one which is electronically and digitally controlled, new possibilities of flow metering, response, system control, diagnostics (self-healing) and automation are now possible. The pump is able to create real time data for live streaming via telematics.

Danfoss advanced off-road demonstrators are showing radical improvements in efficiency and controllability.  In multiple field tests, the original axial piston pump was replaced by a Digital Displacement® pump as a simple pump upgrade. Benchmarking to a conventional 16-tonne excavator, fuel consumption on a standard work cycle was reduced between 16 and 21 percent, whilst at the same time, productivity was increased by 28 percent.

At Danfoss Digital Displacement we aim to make the complex, simple, to re-imagine your machine to be optimized and differentiated unlike any on the market. Owned by Danfoss and developed in Scotland over the last 25 years, digital hydraulic technology delivers productivity, response and efficiency that cannot be replicated elsewhere in the market.

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Pumps

Green efficiency in Dublin’s Central Bank

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High performance, long-lasting sustainability and energy efficiency: The central bank campus in dublin unites these three aspects. Located in north wall quay in Dublin Ireland, the modern building provides a state-of-the-art workplace, facilitating open communication and promoting teamwork at every level. Germany-based technology expert Wilo has equipped the new campus with green pumps, and thus contributes to the building’s environmental efficiency.

The Dublin Docklands is spread over 520 hectares north and south of the Liffey. High employment prospect possibilities have attracted people and businesses since the late 18th century. What used to be a landscape of ship funnels, cranes, pubs and stables, has been transformed into a gleaming, modern business hub due to urban regeneration over the past years. North Wall Quay is located on the northern side of Dublin, including the International Financial Services Centre (IFSC). Since 2017, the new headquarters of the Central Bank of Ireland have been located here. The sculptural profile of the new building reflects the maritime setting and new civic identity of the Dockland area. The building is wrapped in a glass skin, which is shielded from glare and solar heat gain by an outer layer of anodized aluminium triangular mesh panels. Those panels contribute significantly to the overall energy performance by reducing the impact of solar heat and thus also reducing the energy needed for heating and cooling. The façade is broken down into a number of elements: a double glazed unitised inner skin, an outer solar shading skin, the unique glazing system and a rain screen cladding. North Wall Quay is the first office building in Ireland to achieve the Building Research Establishment’s Environmental Assessment Method (BREEAM) ‘Outstanding’ rating at design stage. The building energy rating (BER) is targeted to A2, which equates to a 72 % improvement in energy consumption over previous building regulation baselines. Effective insulation also reduces the energy consumption, the environmental impact is held on a low level by using energy from renewable sources. Annual energy savings according to the BER A2 rating is 209 tonnes of CO2.

Covering the complete life cycle

Green Wilo pumps also contribute to the overall efficiency of the new headquarters – from heating and cooling to cold water supply and products for rainwater harvesting. “Central Bank campus is a green building, certified by BREEAM, the world’s leading sustainability assessment method. The bank itself had set a number of objectives when it came to the sustainability of the building – one of our main requirements was to only provide high-efficient pumps with efficiency class IE4 to ensure compliance with BREEAM criteria”, says Derek Elton Managing Director from Wilo Ireland. The Wilo-Stratos GIGA series included for example is an electronically controlled glanded single pump in Inline-design using EC motor technology for increased operation efficiency along with the Wilo-IL-E series used for pumping the heating and chilled water systems. The Wilo-SiBoost Smart 3 Helix EXCEL series are in operation for cold water applications including rain water harvesting. The compact high efficiency pressure boosting system consists of vertically-mounted stainless steel high-pressure multistage centrifugal glanded pumps for which each pump has an integrated frequency converter for maximum efficiency of operation. These packaged booster systems include ready for connection stainless steel pipework base frame mounted and an automatic control system with all necessary measurement and adjustment facility. For a reliable operation in the HVAC applications several Wilo-Stratos models are used. Recently, Wilo Ireland has also been awarded with the service contract for the new campus: “As a global specialist for pumps and pump systems, we offer a wide variety of services to help our clients optimising and securing their processes”, explains Derek Elton. “Caring about our customer is an ongoing process. It is our understanding that our services cover the complete life cycle of our Wilo products – to live up to the sustainable requirements of our customers.” The Central Bank of Ireland also takes a pro-active approach to managing environmental obligations, which results in e.g. rainwater harvesting at North Wall Quay campus. This method is a simple and smart way to collect rainfall for further usage. Capturing the water can help recharge local aquifers or avoid urban flooding and thus create a sustainable water management.

The dockland campus

The building provides a modern workplace facilitating open communication, promoting teamwork and interaction at every level. The heart of North Wall Quay is the atrium, featuring collaboration spaces. More than 1,400 people work at the eight floor building. Central Bank set a number of objectives for the design of the building: apart from establishing a productive workplace, it was of outmost importance to ensure the environmental sustainability.

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