Two pulp bleaching chemicals have emerged to knock chlorine from the top spot, but their popularity is subject to regional variations

by JAB Whiteside

Greener chemicals for a whiter pulp

Sodium chlorate and hydrogen peroxide have replaced chlorine gas as the most commonly used bleaching agents in pulp and paper mills across the globe. Other bleaching chemicals, such as ozone, peracids and enzymes, continue to occupy niche positions, but they are not expected to grow significantly over the next decade.

In North America, pulp mills have seen a significant annual increase in consumption of sodium chlorate in their bleaching units throughout the 1990s. This growth has mainly been achieved at the cost of chlorine usage, but there are still a large number of North American mills using chlorine as a bleaching chemical. In 1985, chlorine demand by pulp and paper mills was 1.95 million tons/yr, while sodium chlorate was 620,000 tons/yr. By 1995, sodium chlorate demand had grown 250% to around 1.55 million tons/yr and chlorine had plummeted by 46% to around 1.05 million tons/yr. By 2000, sodium chlorate demand is expected to climb 65% to 2.55 million tons/yr, boosted by the recently introduced "Cluster Rules". Chlorine sales on the other hand could dip by a further 38% (Figure 1).

The North American sodium chlorate market looks set to be balanced in 1998, with adequate installed capacity to cope with annual growth rates of 5-6% in demand. The main North American producers of sodium chlorate are Eka Chemicals, Sterling Pulp Chemicals and CXY Chemicals (the partnership formed by Canadian Occidental Petroleum and Occidental Chemical Corp). Total North American sodium chlorate capacity is expected to rise to 2.25 million tons by 2000 (Figure 2).

Taking a longer-term view, North American sodium chlorate demand is expected to plateau and then fall slightly, with the rise in consumption of totally chlorine-free bleaching agents such as hydrogen peroxide, oxygen and ozone early in the next century. Even so, sodium chlorate will continue to be the most popular bleaching chemical in the USA, particularly in the east of the country.

In Canada, where the transition to ECF pulp started earlier than in the USA, growth rates are starting to peak. Total North American demand for sodium chlorate is expected to be around 1.95 million tons in 1998.

Peroxide falls flat

The main competitor to the sodium chlorate business is hydrogen peroxide and in North America its consumption has significant increased through the 1990s, capitalizing on the strong demand growth from the pulp and paper industry. In 1995, total peroxide capacity in the region stood at 507,000 tons/yr. In 1996 this grew to 518,000 tons/yr, following a 11,000 ton expansion at DuPont's Gibbons, Alabama, plant.

Despite the worsening climate in the pulp and paper industry in 1997, further expansions were commissioned in 1997 as projects were too advanced to be shelved. This raised total capacity to 634,000 tons/yr including one cut-back of 10,000 tons at FMC's Spring Hill plant, West Virginia. Between 1995 and 2000, North American peroxide capacity is predicted to rise by 27% (Figure 3).

The main producers of hydrogen peroxide in North America last year were DuPont, FMC and Solvay Interox. In the second quarter of 1998, DuPont partly quit the market, selling its Gibbons, AB, operations (80,000 tons/yr) to Degussa. Further plant sales of DuPont's Memphis, TN, and Maitland, ON, hydrogen peroxide business units to OCI Chemical fell through in July, evidently because OCI could not reach a final agreement with its financial backer. DuPont is expected to find another buyer in the near future.

Prospects for hydrogen peroxide in North America are intimately linked with the pulp and paper industry, which accounts for 57% of all North American sales. In Canada, the pulp and paper industry accounts for 96% of the region's peroxide consumption, while in the USA it accounts for 48%. Other end-use sectors are small in comparison, with only the environmental sector (12%) and textiles business (10%) reaching double figures.

Prior to the steep fall in pulp and paper industry fortunes in 1996, hydrogen peroxide demand had been growing at 10-12%/yr and producers confidently expected the situation to continue for the next 10 years at least. After the crash, growth rates were recast downward to 8-10%/yr, but even these are now seen as being too optimistic. Growth in 1998 is expected to be around 4-5%, rising slightly to around 5-6%/yr over the next 5-10 years.

The lower estimates for future peroxide growth have much to do with the final form of the so-called "Cluster Rules" set by the US Environmental Protection Agency (EPA) for air and waste emission from US pulp and paper mills. It was obvious to most in the industry that the Cluster Rules would abolish chlorine gas bleaching, but earlier in the decade it was also thought that EPA would opt for a totally chlorine-free (TCF) pulp bleaching route. This would have meant tremendous growth in the use of peroxide. But EPA has bowed (many say) to industrial pressure and instead decided on an elemental chlorine-free (ECF) route. The new rule will become mandatory around mid-1999.

The main beneficiary of EPA's decision to reduce the severity of its Cluster Rules has been sodium chlorate, which will be used as chlorine dioxide to replace chlorine gas bleaching at all kraft pulp mills in the USA by early in the next century.

In Canada, due to much stricter environmental Provincial State rules, a much higher proportion of mills are already committed to sodium chlorate bleaching. But what is proving to be of great interest is the emerging role for hydrogen peroxide in combination with sodium chlorate. With the sharp decline in price of peroxide over the last 12 months, due mainly to overcapacity, the bleaching agent has assumed the role of a commodity chemical and is now being increasingly used with sodium chlorate in two-stage ECF bleaching sequences, where it enhances brightness without reducing pulp strength. Pulp mills are also finding that smaller quantities of chlorate are required in two-stage bleaching to achieve the required brightness, with consequent savings on raw material costs.

Peroxide demand growth is expected to continue, but at much lower rates than in the earlier part of the 1990s. Over the next eight years, growth will be around 5-6%/yr, which will undoubtedly lead to further capacity expansions by the year 2002.

Stable Europe

The bleaching plants of the western European pulp and paper industry are almost 100% committed to sodium chlorate and hydrogen peroxide, with only one or two mills in Spain and Portugal still using chlorine gas bleaching on an irregular basis. Predominantly, western European bleached pulp is ECF or TCF in origin. Sodium chlorate demand at pulp mills grew strongly in the first half of the 1990s. But in the second half of the decade, consumption has stabilized and now moves in accordance with the fluctuations in demand for pulp and paper. The current capacity situation is shown in figure 4. No further expansions are expected in the medium term.

There have been predictions that sodium chlorate capacity in western Europe would decline in the last few years of the 1990s, but this has not been the case. It is true that sodium chlorate must compete with hydrogen peroxide for a share in the growth in demand for bleaching chemicals, but it is not losing out, at least not yet. However, demand for sodium chlorate in the western European chemical pulp bleaching sector is predicted to peak at around 605,000 tons/yr in 2000 and then decline slightly to stabilize at around 590,000 tons/yr by 2010 (Figure 5).

Demand for hydrogen peroxide in the European pulp and paper industry has been growing at about 8-10%/yr for the last few years, both in two-stage bleaching in combination with sodium chlorate for ECF pulp production and with oxygen for TCF production. There has also been considerable growth in demand from its use as a deinking agent in the treatment of wastepaper for recycled pulp production, particularly in continental Europe.

The three largest producers of hydrogen peroxide in western Europe are Solvay Interox, Degussa and Eka Chemicals (Figure 6). Hydrogen peroxide plant capacity grew from 882,000 tons/yr in 1995 to reach 1.048 million tons/yr in 1997, with expansions in Sweden by Eka Chemicals and FMC's new plants, Oxysynthese and Ausimont. Solvay intends to close a small 23,000 ton/year plant in Germany. Western Europe will then have adequate capacity to supply all domestic requirements until the first decade of the next century.

In the middle of 1998, Elf Atochem acquired 100% ownership of Oxysynthese, its 50:50 joint venture in hydrogen peroxide with Air Liquide. With it, Elf assumed total control of the 105,000 ton/yr facility at Jarre in southern France - the largest peroxide plant in the world. The deal also involved a 35,000 ton/yr unit at Leuna, Germany, a 73,000 ton/yr plant at Becancour, Canada, a 25,000 ton/yr plant at Tomokomai, Japan, and a 35,000 ton/yr plant under construction at Shanghai in China, where the local partner is Shanghai Pacific Chemical.

Unlike sodium chlorate, western European demand for hydrogen peroxide as a bleaching agent and as a deinking aid will continue to increase through the next 10-15 years. Demand is forecast to total 455,000 tons in 2000, rising from 160,000 tons in 1990 and 235,000 tons in 1995 (Figure 7).

TCF pulp has not performed as expected, apart from its popularity in Nordic markets and in the environmentally conscious German paper sector, and output is not likely to exceed 15% of total production over the next 10 years. The European pulp and paper industry will continue to concentrate on the production of ECF pulp, with emphasis being given to the concept of the closed loop or minimum emission mill. If for any reason there is a failure in the development of minimum emission technology at pulp mills, however, then environmental pressures could swing favor back to TCF bleaching. This would ensure it a much larger market share, perhaps as high as 50% in the first quarter of the next century.

JAB Whiteside is the editor of Bleaching Chemicals at Harriman Chemsult, London, UK